COMMUNICATION ARRANGEMENT, METHOD OF COMMUNICATION AND COMPUTER PROPGRAM FOR PERFORMING THE SAME

Abstract

A communication arrangement, a method for the operation thereof and a computer program including instructions causing a computer to perform the method for the operation of the communication arrangement are disclosed. The communication arrangement includes one or more digitally controllable scatterers, DCSs, an assignment circuitry and a DCS control circuitry. The assignment circuitry is configured to assign a respective base phase shift pattern to each of the one or more DCSs. The DCS control circuitry is configured to operate, during a sequence of time intervals, each DCS of the one or more DCSs to provide a respective sequence of phase shift patterns that is obtained by applying, during each time interval of the sequence of time intervals, a respective additional phase shift from a sequence of additional phase shifts for the respective DCS to the base phase shift pattern assigned to the respective DCS.

Claims

1. A communication arrangement, comprising: one or more digitally controllable scatterers, DCSs; assignment circuitry configured to assign a respective base phase shift pattern to each of the one or more DCSs; and DCS control circuitry configured to operate, during a sequence of time intervals, each DCS of the one or more DCSs to provide a respective sequence of phase shift patterns that is obtained by applying, during each time interval of the sequence of time intervals, a respective additional phase shift from a sequence of additional phase shifts for the respective DCS to the base phase shift pattern assigned to the respective DCS.

2. The communication arrangement according to claim 1, wherein each of the one or more DCSs comprises a plurality of scattering elements, wherein the base phase shift pattern assigned to the respective DCS defines a respective phase shift value for each scattering element of at least a part of the plurality of scattering elements of the respective DCS, and wherein, for each time interval of the sequence of time intervals, the applying of the respective additional phase shift from the sequence of additional phase shifts for the respective DCS to the base phase shift pattern assigned to the respective DCS comprises adding, for each scattering element of the at least a part of the plurality of scattering elements, the respective additional phase shift for the respective time interval from the sequence of additional phase shifts for the respective DCS to the phase shift value for the respective scattering element defined by the base phase shift pattern.

3. The communication arrangement according to claim 2, wherein, for at least one of the one or more DCSs, the at least a part of the plurality of scattering elements of the respective DCS is a first part of the plurality of scattering elements of the respective DCS, a second part of the plurality of scattering elements of the respective DCS providing a virtual DCS, the assignment circuitry being configured to assign a base phase shift pattern of the virtual DCS to the virtual DCS, the base phase shift pattern of the virtual DCS defining a respective phase shift value for each scattering element of the second part of the plurality of scattering elements, and wherein the DCS control circuitry is configured to add, during each time interval of the sequence of time intervals, a respective additional phase shift from a sequence of additional phase shifts for the virtual DCS to each of the phase shift values for the scattering elements of the second part of the plurality of scattering elements that are defined by the base phase shift pattern for the virtual DCS, the sequence of additional phase shifts for the virtual DCS being different from the sequence of additional phase shifts for the respective DCS.

4. The communication arrangement according to claim 1, wherein the assignment circuitry is further configured to assign a respective codeword from a set of codewords to each of the one or more DCSs, and wherein, for each DCS, the sequence of additional phase shifts for the respective DCS is based on a sequence of codeword components of the codeword assigned to the respective DCS.

5. The communication arrangement according to claim 4, wherein the one or more DCSs are a plurality of DCSs, and each DCS is assigned a different codeword from the set of codewords.

6. The communication arrangement according to claim 4, wherein the codewords from the set of codewords are at least one of orthogonal and semi-orthogonal.

7. The communication arrangement according to claim 4, wherein, for each of the one or more DCSs, each additional phase shift of the sequence of additional phase shifts for the respective DCSs is selected such that by applying the respective additional phase shift to the base phase shift pattern assigned to the respective DCS, a phase shifted scattering pattern of the DCS is obtained which corresponds to a product of a codeword component of the codeword assigned to the respective DCS and a base scattering pattern of the DCS that is obtained when the DCS provides the base phase shift pattern of the DCS.

8. The communication arrangement according to claim 1, further comprising signal component separation circuitry configured to obtain reception information from one or more first communication nodes, CNs, the reception information being based on a reception, by the one or more first CNs, of one or more transmission signals transmitted by one or more second CNs during the sequence of time intervals, wherein the reception information comprises a representation of at least a part of one or more signals received by the one or more first CNs in response to the transmission of the one or more transmission signals by the one or more second CNs during the sequence of time intervals, and wherein the signal component separation circuitry is configured to apply a transformation to the representation of the at least a part of the one or more signals received by the one or more first CNs to separate one or more signal components of the at least a part of the one or more signals that were received by the one or more first CNs via the one or more DCSs.

9. The communication arrangement according to claim 8, wherein the transformation is a linear transformation.

10. The communication arrangement according to claim 8, further comprising: channel estimation circuitry configured to compute, on the basis of the reception information and the set of codewords, a channel estimate that comprises, for at least one DCS of the one or more DCSs, an estimate of at least one respective communication channel between at least one of the one or more first CNs and at least one of the one or more second CNs via the at least one of the one or more DCSs.

11. The communication arrangement according to claim 10, wherein the channel estimation circuitry is further configured to compute a representation of the one or more transmission signals transmitted by the one or more second CNs on the basis of an aggregate communication channel and a result of the transformation, and to compute the channel estimate on the basis of the computed one or more transmission signals and the result of the transformation.

12. The communication arrangement according to claim 8, wherein the time intervals of the sequence of time intervals are subintervals of a coding time interval.

13. The communication arrangement according to claim 12, wherein at least one of the one or more second CNs transmits a plurality of orthogonal frequency division multiplexing, OFDM, symbols during the coding time interval.

14. The communication arrangement according to claim 13, wherein each of the one or more second CNs has one or more antennas, and each of the one or more second CNs transmits, during each time interval of the sequence of time intervals, a number of OFDM symbols that corresponds to a total number of the antennas of the one of more second CNs.

15. The communication arrangement according to claim 8, wherein the transformation is based on a set of conjugate codewords for the set of codewords.

16. The communication arrangement according to claim 12, wherein at least one of the one or more second CNs transmits a single OFDM symbol during the coding time interval.

17. The communication arrangement according to claim 16, wherein the applying of the additional phase shifts of the sequence of additional phase shifts is repeated during each of a plurality of coding time intervals, and the reception information is based on a reception, by the one or more first CNs, of one or more transmission signals transmitted by the one or more second CNs during the plurality of coding time intervals, the transformation being applied to a representation of the received one or more transmission signals.

18. The communication arrangement according to claim 17, wherein each of the one or more second CNs has one or more antennas, wherein each of the one or more second CNs transmits a single OFDM symbol during each coding time interval of the plurality of coding time intervals, and wherein a number of the plurality of coding time intervals corresponds to a total number of the antennas of the one or more first CNs.

19. The communication arrangement according to claim 18, wherein the transformation is based on a model of phase variations induced by the application of the sequence of additional phase shifts during the transmission of the single OFDM symbol.

20. The communication arrangement according to claim 12, wherein the coding time interval corresponds to a sampling interval wherein the one or more signals received by the one or more first CNs in response to the transmission of the one or more transmission signals by the one or more second CNs are sampled.

21. The communication arrangement according to claim 8, wherein at least one of the one or more first CNs is a user equipment and at least one of the one or more second CNs is a base station.

22. The communication arrangement according to claim 8, wherein at least one of the one or more first CNs is a base station and at least one of the one or more second CNs is a user equipment.

23. A method of communication, comprising: assigning a respective base phase shift pattern to each of one or more DCSs; operating, during a sequence of time intervals, each DCS of the one or more DCSs to provide a respective sequence of phase shift patterns that is obtained by applying, during each time interval of the sequence of time intervals, a respective additional phase shift from a sequence of additional phase shifts for the respective DCS to the base phase shift pattern assigned to the respective DCS.

24. A computer program comprising instructions which, when carried out on a computer, cause the computer to perform a method according to claim 23.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0038] In the following, embodiments will be described with reference to the drawings, wherein:

[0039] FIG. 1 shows communication channels in an arrangement including a DCS and two CNs;

[0040] FIG. 2 shows a communication arrangement;

[0041] FIG. 3 shows a CN;

[0042] FIG. 4 shows a DCS;

[0043] FIGS. 5a to 5d show configurations of scattering surfaces of DCSs;

[0044] FIG. 6 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during a transmission of a plurality of orthogonal frequency division multiplexing (OFDM) symbols during a coding time interval;

[0045] FIG. 7 shows a timing diagram illustrating a signal sent by a BS on a subcarrier and a signal received at a UE during OFDM symbols without DCS coding outside a coding time interval and with coding during a coding time interval for a downlink SISO case;

[0046] FIG. 8 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during a transmission of a plurality of downlink OFDM symbols during a coding time interval;

[0047] FIG. 9 shows a timing diagram illustrating a signal sent by a BS on a subcarrier and a signal received at a UE during OFDM symbols without DCS coding outside a coding time interval and with DCS coding during a coding time interval for a downlink MIMO case;

[0048] FIG. 10 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during a transmission of a plurality of OFDM symbols by a UE in uplink during a coding time interval;

[0049] FIG. 11 shows a timing diagram illustrating a signal sent by a UE on a subcarrier and a signal received at a BS from the UE during OFDM symbols without coding outside a coding time interval and with DCS coding during a coding time interval for an uplink MIMO case;

[0050] FIG. 12 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during one downlink OFDM symbol which corresponds to a coding time interval;

[0051] FIG. 13 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during each of a plurality of OFDM symbols, each of which corresponds to one of a plurality of coding time intervals;

[0052] FIG. 14 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during each of a plurality of OFDM symbols, each of which corresponds to one of a plurality of coding time intervals;

[0053] FIG. 15 shows a timing diagram illustrating an embodiment wherein a DCS applies a coded scattering pattern sequence during a sampling time interval which corresponds to a coding time interval;

[0054] FIG. 16 illustrates signaling according to an embodiment in a downlink scenario wherein a BS performs the configuration steps and uses signaling to inform DCSs and UEs after all the configuration steps are completed;

[0055] FIG. 17 illustrates signaling according to an embodiment in a downlink scenario wherein the BS performs the configuration steps and uses multiple signaling to inform DCSs and UEs after each configuration step is completed;

[0056] FIG. 18 illustrates signaling according to an embodiment in a downlink scenario wherein one DCS performs the configuration steps and uses multiple signaling to inform the other DCSs and UEs after each configuration step is completed;

[0057] FIG. 19 illustrates signaling according to an embodiment in an uplink scenario wherein a BS performs the configuration steps and uses signaling to inform DCSs and UEs after all the configuration steps are completed;

[0058] FIG. 20 illustrates signaling according to an embodiment in an uplink scenario wherein a BS performs the configuration steps and uses multiple signaling to inform DCSs and UEs after each configuration step is completed;

[0059] FIG. 21 illustrates signaling according to an embodiment in an uplink scenario wherein one DCS performs the configuration steps and uses multiple signaling to inform the other DCSs and UEs after each configuration step is completed; and

[0060] FIGS. 22, 23 and 24 illustrate signaling in embodiments wherein configuration steps are performed by extra logical entities.

DESCRIPTION OF EMBODIMENTS

[0061] The present disclosure provides embodiments of communication arrangements, methods of communication and computer programs wherein digitally controllable scatterers (DCSs) are used. In embodiments disclosed herein, during a sequence of time intervals, each DCS of one or more DCSs is operated to provide a respective sequence of phase shift patterns that is obtained by applying, during each time interval of the sequence of time intervals, a respective additional phase shift from a sequence of additional phase shifts for the respective DCS to the base phase shift pattern of the respective DCS.

[0062] The base phase shift pattern of each DCS is modified only by applying additional phase shifts, so that the resulting radiation pattern of the DCS is a phase shifted version of the pattern obtained when applying the base phase shift pattern.

[0063] The sequence of phase shift patterns can be provided on the basis of codes. In each time interval, only one scalar component per DCS is required for providing the additional phase shift for the DCS which is the same for all scattering elements of the DCS. Accordingly, providing only one codeword for each DCS is sufficient, and orthogonality or semi-orthogonality is required only between codewords of different DCSs, but not between individual scattering elements of one DCS. Thus, relatively short codewords can be used since the codeword length does not depend on the number of scattering elements, which is a desirable feature since the number of elements can be quite large (hundreds/thousands).

[0064] The coding can be applied during the transmission of data and more than one DCS can be active in each time interval, so that the overall overhead of DCS channel quality measurement can be reduced. Furthermore, in embodiments, codes such as, for example, Hadamard codes can be used. In Hadamard codes each component of the codeword is limited to only a small number (two) of possible values. This means that each phase shift in the sequence of additional phase shifts is limited to only a small number (two) of possible values. This can simplify the implementation.

[0065] FIG. 2 shows a schematic view of a communication arrangement 200 according to an embodiment. The communication arrangement 200 includes a plurality of DCSs 201, 202, 203 and a plurality of communication nodes (CNs) 204, 205, 206, 207. As shown in FIG. 2, the CN 204 can be a base station (BS) and the CNs 205-207 can be user equipments (UEs) or repeaters. A communication channel between BS 204 and the UEs 205-207 is in part via the DCSs 201, 202, 203. The wireless signals between the BS 204 and UEs 205-207 propagate via non-DCS paths that are illustrated by dotted line arrows and via DCS paths that are illustrated by solid line arrows.

[0066] The present disclosure is not limited to embodiments wherein one BS and a plurality of CNs are provided, as shown in FIG. 2. For example, the plurality of CNs 204-207 can include more than one BS, or all the CNs can be UEs. It can also include repeaters, IABs and other network components. Generally, there can be K UEs and D DCSs. In addition to one or more BSs and one or more UEs, the plurality of CNs can include one or more access points (APs).

[0067] FIG. 3 shows a schematic block diagram of a CN 300 according to an embodiment. The CN 300 can be a UE such as, for example, one of the CNs 205-207 shown in FIG. 2, or a BS such as, for example the BS 204 shown in FIG. 2. The CN 300 can include antennas 301, 302. The number of antennas can be one or two, as shown in FIG. 3. In other embodiments, a greater number of antennas can be provided. Providing two or more antennas can allow performing communication in accordance with multiple input, multiple output (MIMO) technologies. In further embodiments, for example in embodiments wherein the CN 300 is a UE, a single antenna can be provided. However, UEs having more than one antenna can also be used.

[0068] The CN 300 can include transmitter circuitry 303 and receiver circuitry 304, which are connected to the antennas 301, 302, and can be used for transmitting and/or receiving pilot signals and data signals for transmitting and/or receiving various types of information. Additionally, the CN 300 can include computation circuitry 305, which can include a processor and memory. The computation circuitry 305 can be used for carrying out various algorithms, as will be described below. The computation circuitry 305 can be used for performing various types of data processing at the CN 300 when methods of communication using the CN are carried out as described in detail below, so that the computation circuitry 305 can be configured so as to include circuitry for various purposes.

[0069] In embodiments, the computation circuitry 305 can include assignment circuitry 306. Additionally, the computation circuitry 305 includes signal component separation and channel estimation circuitry 307. The assignment circuitry can include base phase shift pattern assignment circuitry 306a, codeword assignment circuitry 306b, coding time interval assignment circuitry 306c and transmission signal assignment circuitry 306d. The signal component separation and channel estimation circuitry can include signal component separation circuitry 307a and, in embodiments, channel estimation circuitry 307b.

[0070] The present disclosure is not limited to embodiments wherein the assignment circuitry 306 is provided in a CN. In other embodiments, the assignment circuitry 306 can be provided in a DCS, as will be described in more detail below with reference to FIG. 4. In still further embodiments, the assignment circuitry or at least parts thereof can be provided in network entities that are different from CNs and DCSs. For example, the base phase shift pattern assignment circuitry 306a can be provided in a DCS control entity, the codeword assignment circuitry 306b and the coding time assignment circuitry 306c can be provided in a channel estimation entity and the transmission signal assignment circuitry 306d can be provided in the CN. In some embodiments wherein a channel estimation entity is provided, the signal component separation and channel estimation circuitry 307 or at least parts thereof can also be provided in the channel estimation entity.

[0071] Furthermore, the present disclosure is not limited to embodiments wherein the assignment circuitry 306 and the signal component separation and channel estimation circuitry 307 are provided in all CNs of the communication arrangement. For example, they can be provided in only one of the CNs which can be a BS or a UE.

[0072] FIG. 4 schematically illustrates a DCS 400 which can be implemented in the form of an Intelligent Reflective Surface (IRS) or Reflective Intelligent Surface (RIS). In embodiments, some or all of the DCSs 201, 202, 203 of the communication arrangement 200 can have features corresponding to those of the DCS 400. The DCS 400 includes a scattering surface 401 and a controller 402. The scattering surface 401 includes a plurality of scattering elements 407, one of which is exemplarily denoted by reference numeral 408. The plurality of scattering elements 407 can be adapted such that scattering phase shifts of the scattering elements of the plurality of scattering elements 407 (which will be denoted as scattering elements 407 in the following) for electromagnetic radiation are electronically controllable. In some embodiments, each of the scattering elements 407 can include an antenna based scattering circuitry and phase shifting circuitry. The phase shift provided by the phase shifting circuitry can be electronically controlled so as to provide the scattering phase shift of the scattering element. In other embodiments, the scattering elements 407 can include meta-material elements configured to provide a scattering phase shift for electromagnetic radiation in the predetermined frequency range that can be electronically controlled. By controlling the scattering phase shifts of the scattering elements 407, directions into which electromagnetic radiation impinging on the scattering surface 401 of the DCS is scattered and a phase of the scattered electromagnetic radiation can be controlled.

[0073] The DCS 400 can further include a controller 402. The controller 402 can include interface circuitry 403 for connecting the controller 403 to the scattering elements 407 of the DCS 400, and computation circuitry 404, which can include a processor and a memory so that the computation circuitry 404 can be configured as circuitry for various purposes. The computation circuitry 404 can include assignment circuitry 306 which can have features as described above with reference to FIG. 3. In particular, the assignment circuitry 306 can include base phase shift pattern assignment circuitry 306a, codeword assignment circuitry 306b, coding time interval assignment circuitry 306c and/or transmission signal assignment circuitry 306d (see FIG. 3). Additionally, the computation circuitry 404 can include DCS control circuitry 405.

[0074] The present disclosure is not limited to embodiments wherein each of the DCSs 201, 202, 203 has a scattering surface 401 that is substantially planar, as shown in FIG. 4. In other embodiments, some or all of the DCSs can include scattering surfaces having a non-planar configuration, as will be described in the following with reference to FIGS. 5a, 5b and 5c.

[0075] FIG. 5a schematically illustrates a scattering surface 501a, which can be used as an alternative to the scattering surface 401 of the DCS 400 shown in FIG. 4. The scattering surface 501a includes a plurality of scattering elements 407, one of which is exemplarily denoted by reference numeral 408. The scattering surface 501a has a non-planar configuration, wherein a front side of the scattering surface 501a is convex. The front side of the scattering surface 501a is the side on which, in the operation of the DCS 400, the electromagnetic radiation reflected at the scattering surface 501a impinges. For example, in embodiments, the scattering surface 501a can be mounted on a wall of a building. In such embodiments, the front side of the scattering surface 501a is the side of the scattering surface that is averted from the wall.

[0076] FIG. 5b schematically illustrates a scattering surface 501b, which can be used as another alternative to the scattering surface 401 of the DCS 400 shown in FIG. 4. The scattering surface 501b includes a plurality of scattering elements 407, one of which is exemplarily denoted by reference numeral 408. The scattering surface 501b has a non-planar configuration, wherein the front side of the scattering surface 501b is concave.

[0077] FIG. 5c schematically illustrates a scattering surface 501c, which can be used as a further alternative to the scattering surface 401 of the DCS 400 shown in FIG. 4. The scattering surface 501c includes a plurality of scattering elements 407, one of which is exemplarily denoted by reference numeral 408. The scattering surface 501c has a non-planar configuration, wherein the front side of the scattering surface 501c includes portions having a different curvature. For example, the front side of the scattering surface 501c can include convex portions, concave portions and/or saddle-shaped portions.

[0078] Moreover, the present disclosure is not limited to embodiments wherein the scattering surface of the DCS 400 is provided as a single piece. FIG. 5d schematically illustrates a scattering surface 501d, which can be used as a further alternative to the scattering surface 401 of the DCS 400 shown in FIG. 4. The scattering surface 501d includes a plurality of DCS blocks 502, 503, 504, 505, which can be distributed. Thus, the scattering surface 501d is not provided as a single piece. The scattering surface 501d includes a plurality of scattering elements, wherein each of the DCS blocks 502-505 includes a subset of the scattering elements. The DCS blocks 502-505 can have a non-planar configuration, as shown in FIG. 5d. In other implementations, some or all of the DCS blocks 502-505 can be planar. The scattering elements of the DCS blocks 502-505 can be operated in a coordinated manner, so that the scattering surface 501d is provided as a virtual DCS scattering surface.

[0079] Referring to FIG. 2 again, the controllable scattering phase shifts of the scattering elements of each of the DCSs 201, 202, 203 provide a way to modify the scattering pattern of the respective DCS, and hence to modify the communication channel between the BS 204 and the UEs 205-207 in order to improve the downlink and uplink communication. Knowing the contribution of each DCS 201, 202, 203 to the overall communication channel between the BS 204 and each UE 205-207 can be important for designing the communication algorithms that exploit the presence of DCSs 201-203 for improved downlink and uplink performance. The achieved improvement depends on the available channel state information (CSI).

[0080] Embodiments described herein provide solutions for estimating the contribution of each DCS 201, 202, 203 to the overall communication channel between BS 204 and UEs 205-207. This can be a challenging task, in particular when the scattering elements of the DCSs 201-203 are not connected to radio frequency (RF) chains. In this case, the DCSs 201-203 cannot estimate propagation conditions and cannot transmit pilot signals either. This means that the contribution of each DCS 201, 202, 203 to the overall communication channel can only be measured either at the BS 204 or at the UEs 205-207 via signals transmitted either by the BS 204 or the UEs 205-207. This complicates the task of characterizing the overall communication channel via each of the DCSs 201, 202, 203.

[0081] In the following, the index d will be used to denote the DCSs. The total number of DCSs will be denoted as D and the number of scattering elements of DCS d will be denoted as S.sub.d. The index k will be used to denote user equipments (UEs) and the total number of UEs will be denoted as K.

[0082] The phase shift pattern of the S.sub.d scattering elements of DCS d can be represented by a vector .sub.d whose components are the scattering phase shifts provided by the individual scattering elements of DCS d. The controllable phase shift pattern configuration of the scattering elements provides a way to control the scattering pattern of the DCSs and hence to modify the communication channel between the BS and the UEs in order to improve the downlink and uplink communication. In the following, the scattering pattern obtained by providing the phase shift pattern represented by .sub.d at DCS d will be denoted as F.sub.d(.sub.d). In the downlink, the signal received from the BS at the k.sup.th UE can be modeled as

[00001]$\begin{array}{cc}{y}_k=y_{0,k}+{.Math.}_{d=1}^D{y}_{{\mathrm{DCS}}_d,k},& \mathrm{Equation}\left(1\right)\end{array}$

where y.sub.0,k represents the signal received via the non-DCS paths and y.sub.DCS.sub.d.sub.,k represents the signal received via DCS d. In the uplink, a model like the one in Equation (1) can also be used to describe the signal received at the BS from the k.sup.th UE. Observing y.sub.k provides only information about the aggregate received signal, that is, the sum of the contributions of all DCS and non-DCS paths. Obtaining the decomposed information related to the signal component y.sub.0,k received via the non-DCS channel and the signal components from the D DCSs, namely y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k is of interest because it facilitates knowing the contribution of each DCS and hence facilitates estimating the communication channel via each DCS.

[0083] The present disclosure provides a DCS coding scheme that allows a receiver to obtain an estimate of the received non-DCS signal component y.sub.0,k and all signal components y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k received through the D DCSs using only the aggregate received signal y.sub.k described in Equation (1) and the knowledge of the coding used at the different DCSs.

[0084] Furthermore, the present disclosure provides a way to estimate both the non-DCS and DCS channels using the obtained signals y.sub.0,k, y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k. In embodiments, this can be done when these signals carry data information instead of training or pilot signals. The present disclosure provides a way to decompose and obtain the contribution from each DCS to the received signal and to estimate the non-DCS and DCS channels.

[0085] In embodiments, some or all of the following steps can be performed.

1. Base Phase Shift Pattern Assignment Step

[0086] In the base phase shift pattern assignment step, a respective base phase shift pattern .sub.d is assigned to each DCS d=1, 2, . . . , D. The base phase shift pattern .sub.d can define a respective phase shift value for at least a part of the scattering elements of the DCS d. In embodiments, the base phase shift pattern .sub.d can define a respective phase shift value for each of the scattering elements of the DCS d. Thus, a base scattering pattern F.sub.d (.sub.d) is set for each DCS. The base scattering pattern F.sub.d (.sub.d) of DCS d is a scattering pattern that is obtained when the DCS is operated to provide the base phase shift pattern .sub.d, which can be done by controlling the scattering phase shifts of the scattering elements of the DCS d so that they provide the phase shift values defined by the base phase shift pattern .sub.d. The coding for each DCS will be applied on top of the base scattering pattern. If the base phase shift pattern is assigned by a network entity different from the DCSs, then signaling is performed to inform the DCSs of the defined base phase shift patterns. In embodiments, the base phase shift pattern assignment step can be performed by the base phase shift pattern assignment circuitry 306a of the assignment circuitry 306 described above with reference to FIGS. 3 and 4.

2. Codeword Assignment Step

[0087] In the codeword assignment step, a respective codeword from a set of codewords is assigned to each DCS d=1, 2, . . . , D. This can be done by choosing D orthogonal or semi-orthogonal codewords of length T and assigning to each DCS d=1, 2, . . . , D one of the codewords. Different DCSs are assigned different codewords. The codewords are vectors of size 1T and can be represented in a codebook structure as in Equation (2):

[00002]$\begin{array}{cc}=\stackrel{T\mathrm{time}\mathrm{intervals}}{\stackrel{.fwdarw.}{\left[\begin{array}{ccc}{c}_1^1& .Math.& c_1^T\\ .Math.& & .Math.\\ c_D^1& .Math.& c_D^T\end{array}\right]}}D\mathrm{Codewords}& \mathrm{Equation}\left(2\right)\end{array}$

[0088] In the following, c.sub.d is used to denote the codeword assigned to DCS d. This codeword is represented by a vector c.sub.d=[c.sub.d.sup.1, c.sub.d.sup.2, . . . c.sub.d.sup.T], the components of which define a sequence of codeword components c.sub.d.sup.1, c.sub.d.sup.2, . . . c.sub.d.sup.T. Signaling can be performed to inform each DCSs of its assigned codeword. In embodiments, the codeword assignment step can be performed by the codeword assignment circuitry 306b of the assignment circuitry 306 described above with reference to FIGS. 3 and 4.

3. Coding Time Interval Assignment Step

[0089] In the coding time interval assignment step, one or more coding time intervals, which, in the following, will be denoted as T, are defined. A coding time interval is a time interval during which all D DCS devices will apply the codewords chosen in the codeword assignment step to the base phase shift pattern chosen in the base phase shift pattern assignment step.

[0090] Signaling can be used to inform the DCSs of the one or more coding time intervals. As will be described in more detail in the embodiments below, since the codewords have a length T, each coding time interval includes a sequence of T time intervals .sub.1, . . . , .sub.T which are subintervals of the respective coding time interval. In the DCS operating step, which will be described below, during each of the time intervals .sub.1, . . . , .sub.T, an additional phase shift from a sequence of additional phase shifts that is based on the sequence of codeword components c.sub.d.sup.1, . . . c.sub.d.sup.T is applied to the base phase shift pattern .sub.d of DCS d, d=1, 2, . . . , D. Thus, a sequence of phase shift patterns of the DCS d is provided. In embodiments with more than one coding time interval, the applying of the additional phase shifts is repeated during each of the coding time intervals. The duration of the one, .sub.1, or more, .sub.1, .sub.2, .sub.3, . . . coding time intervals therefore depends on the length T of the codewords and the duration of the time interval .sub.t, which is the time interval during which the DCSs d=1, 2, . . . , D apply each the corresponding codeword component . In embodiments, the one or more coding time intervals assignment step can be performed by the coding time interval assignment circuitry 306c of the assignment circuitry 306 described above with reference to FIGS. 3 and 4.

4. Transmission Signal Assignment Step

[0091] In the transmission signal assignment step, the signal that will be transmitted by one or more transmitting CNs during the one, .sub.1, or more, .sub.1, .sub.2, .sub.3, . . . coding time intervals is defined. If the transmission is in the downlink, then the signal transmitted by the BS is defined in the transmission signal assignment step. If the transmission is in the uplink, then the signal transmitted by the UEs is defined in the transmission signal assignment step. In some embodiments, a plurality of orthogonal frequency division multiplexing (OFDM) symbols is transmitted in one coding time interval, wherein the number of OFDM symbols corresponds to the total number of antennas of the transmitting CNs. In other embodiments, a single OFDM symbol is transmitted in each of a plurality of coding time intervals, wherein the number of coding time intervals corresponds to the total number of antennas of the transmitting CNs.

5. DCS Operation Step

[0092] In the DCS operation step, during each of the time intervals .sub.1, . . . , .sub.T that are subintervals of a respective coding time interval of the one, .sub.1, or more, .sub.1, .sub.2, .sub.3, coding time intervals, an additional phase shift from a sequence of additional phase shifts that is based on the sequence of codeword components c.sub.d.sup.1, . . . c.sub.d.sup.T is applied to the base phase shift pattern .sub.d of DCS d, d=1, 2, . . . , D, for providing a sequence of phase shift patterns of the DCS d. The additional phase shifts can be applied to the base phase shift pattern of DCS d by adding, for each scattering element of the at least a part of the scattering elements of DCS d, d=1, 2, . . . , D, the respective additional phase shift for the respective time interval from the sequence of additional phase shifts for DCS d to the phase shift value for the respective scattering element defined by the base phase shift pattern .sub.d.

[0093] The additional phase shifts for DCS d are selected such that a phase shifted scattering pattern of DCS d is obtained which corresponds to a product of a codeword component of the codeword assigned to DCS d and the base scattering pattern .sub.d of DCS d that is obtained when DCS d provides the base phase shift pattern .sub.d. Thus, a sequence of scattering patterns [c.sub.d.sup.1F.sub.d(.sub.d), c.sub.d.sup.2F.sub.d(d), . . . c.sub.d.sup.TF.sub.d(.sub.d)] of DCS d is obtained during the one or more coding time intervals. In embodiments, the operation of the scattering elements of each of the DCSs in the DCS operation step can be controlled by the DCS control circuitry 405 of the respective DCS. Additionally, over-the-air transmission of the transmission signal defined in the transmission signal defining step and a reception of y.sub.k, k=1, . . . , K by K CNs, for example UEs (see Equation (1)) are performed during the one or more coding time intervals.

6. Signal Component Separation and Channel Estimation Step

[0094] In the signal component separation and channel estimation step, knowledge of the received signal y.sub.k and the codewords used by the DCSs, namely c.sub.1, c.sub.2, . . . , c.sub.D, is used to obtain the separated non-DCS and DCS signal components y.sub.0,k, y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k. The knowledge of the received signal y.sub.k can be provided by obtaining reception information. For example, in the downlink, y.sub.k received at UE k can be obtained from reception information at UE k. As another example, in the uplink, the received signal at the BS contains the contribution y.sub.k from each UE k. For obtaining the separated non-DCS and DCS signal components y.sub.0,k, y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . ,y.sub.DCS.sub.D.sub.,k, a transformation can be applied to a representation of the received signals. The transformation can be a linear transformation which can be based on a set of conjugate codewords for the codewords c.sub.1, c.sub.2, . . . , c.sub.D or it can be based on a model of phase variations induced by the sequence of additional phase shifts during a transmission of a single OFDM symbol. In embodiments, the obtaining of the separated non-DCS and DCS signal components can be performed by the signal component separation circuitry 307a of the signal component separation and channel estimation circuitry 307 described above with reference to FIG. 3.

[0095] Based on the separated non-DCS and DCS signal components y.sub.0,k, y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k and an aggregate communication channel that can be obtained via conventional training, a representation of the transmission signals assigned in the transmission signal assignment step can then be computed. The channel estimate can be computed from the representation of the transmission signals and the separated non-DCS and DCS signal components y.sub.0,k, y.sub.DCS.sub.1.sub.,k, y.sub.DCS.sub.2.sub.,k, . . . , y.sub.DCS.sub.D.sub.,k. In embodiments, the computation of the channel estimate can be performed by the channel estimation circuitry 307b of the signal component separation and channel estimation circuitry 307 described above with reference to FIG. 3.

[0096] In the following, embodiments of the individual steps described above will be described in detail.

Embodiments for the Base Phase Shift Pattern Assignment Step

[0097] As mentioned above, in the base phase shift pattern assignment step, a base scattering pattern F.sub.d(.sub.d) is provided for each DCS d=1, 2, . . . , D. In the following, three different ways to obtain F.sub.d(.sub.d) for each DCS d=1, 2, . . . , D are described: [0098] (1) Randomly choose the initial DCS phase configuration by making a random choice of .sub.d. The benefit of this embodiment is its simplicity. However, it might generate reduced SNR for the signals received via the DCSs, unless selected from a predefined set of potential configurations identified for communication. [0099] (2) Choose .sub.d based on previously or offline computed information or previously acquired information. Such a prior information can be, for example (i) Pd that previously resulted in good performance or (ii) statistical channel information or (iii) information about dominant directions for communication between the DCS and one or both of transceivers (TX) and receivers (RX), an example is the offline channel estimation in near field scenario described in PCT/EP2021/057912, the disclosure of which is incorporated herein by reference). [0100] (3) Keep phases that have been selected for communicating and/or serving other UEs in the vicinity (use the one that has been set for communication serving other UEs).

Embodiments for the Codeword Assignment Step

[0101] As mentioned above, in the codeword assignment step, D orthogonal or semi-orthogonal codewords of length T are chosen and one of the codewords is assigned to each DCS d=1, 2, . . . , D. In the following, two implementations of such sequences or codes that can be used are provided. The first one is based on Hadamard codes and the second one is based on Fourier matrices. [0102] (1) Using Hadamard codes. The codewords c.sub.1, c.sub.2, . . . , c.sub.D are chosen from a Hadamard matrix of size D+1. The codeword length is thus T=D+1. An advantage of selecting the codewords from a Hadamard matrix is that in such matrices the elements only take two values {+1, 1}which can be easily implemented via the phase shift at the DCS scattering elements by respectively choosing phase shifts of {0, }. Since the Hadamard matrix is of size D+1, there are D+1 codewords that can be selected. The codeword (Hadamard matrix row) corresponding to all entries equal to +1 is not assigned to any DCS. In this way, this codeword implicitly becomes the codeword of the non-DCS path. If the non-DCS path is not of interest (for example, if it can be disregarded due to its negligible contribution in case of strong blockage) then a Hadamard matrix of size D can be used, and the corresponding rows of this matrix can be assigned as the c.sub.1, c.sub.2, . . . , c.sub.D codewords. For some codeword lengths T, a Hadamard matrix of the required size of D or D+1 may not exist. One option in this case is to use a Hadamard code with length of 2.sup.[log.sup.2.sup.D] were [log.sub.2D] is the nearest upper integer and to use only a subset of its codewords. Other Hadamard based constructions for different code sizes are reported in the literature and are known. [0103] As an example of a Hadamard based construction, consider the case of D=3 where the estimation of the non-DCS path is desired, so that T=D+1=4. A Hadamard matrix of size 4 is the following,

[00003]$\begin{array}{cc}\left[\begin{array}{cccc}+1& +1& +1& +1\\ +1& -1& +1& -1\\ +1& +1& -1& -1\\ +1& -1& -1& +1\end{array}\right].& \mathrm{Equation}\left(3\right)\end{array}$ [0104] The codewords c.sub.1, c.sub.2, c.sub.3 assigned respectively to DCSs d=1, d=2, d=3 are respectively the second to fourth rows of the Hadamard matrix in Equation (3) thus

[00004]$\begin{array}{cc}{c}_1=\left[+1,-1,+1,-1\right]& \mathrm{Equation}\left(4\right)\end{array}$$\begin{array}{cc}{c}_2=\left[+1,+1,-1,-1\right]& \mathrm{Equation}\left(5\right)\end{array}$$\begin{array}{cc}{c}_3=\left[+1,-1,-1,+1\right]& \mathrm{Equation}\left(6\right)\end{array}$ [0105] (2) Using DFT matrices. The codewords are selected from a DFT matrix of size D+1 so the codeword length is T=D+1. The codeword (DFT matrix row) corresponding to all entries equal to +1 is not assigned to a DCS so that this codeword implicitly becomes the codeword of the non-DCS paths. If the non-DCS path is not of interest (for example, if it can be disregarded due to its negligible contribution in case of strong blockage) then a DFT matrix of size D can be used and the corresponding rows of this matrix can be assigned as the c.sub.1, c.sub.2, . . . , c.sub.D codewords. An advantage of the use of DFT matrices is that the entries of such matrices are unit norm exponentials of the form e.sup.j. This facilitates implementation via DCS phases since e.sup.j can be implemented at a scattering element by applying a phase shift of . For implementing DFT based phase shifts, a number of different phase shifts greater than two may need to be provided by the scattering elements of the DCSs, whereas with Hadamard codes the phase shift is further restricted to {0, }.

Embodiments for the Coding Time Interval Assignment Step and the Transmission Signal Assignment Step

[0106] These will be presented later at the same time as the embodiments for the signal component separation and channel estimation step, since embodiments for the coding time interval assignment step, the transmission signal assignment step, and the signal component separation and channel estimation step are related as they depend on the waveform used for communication.

Embodiment for the DCS Operation Step

[0107] As mentioned above, in the DCS operation step, over the air transmission and signal reception are performed, with each DCS d applying the corresponding coded scattering pattern sequence [c.sub.d.sup.1F.sub.d(.sub.d), c.sub.d.sup.2F.sub.d(.sub.d), . . . c.sub.d.sup.TF.sub.d(.sub.d)] during each of the one or more coding time intervals. In the following, an implementation of this coded scattering pattern sequence at a DCS d is explained.

[0108] As mentioned above, the scattering pattern of DCS d is denoted F.sub.d (.sub.d) where .sub.d represents the phase shift pattern applied at the scattering elements of DCS d. More specifically, .sub.d can be represented as a vector with S.sub.d elements as follows,

[00005]$\begin{array}{cc}{}_d=\left[{}_d^1,{}_d^2,.Math.,,.Math.,{}_d^{S_d}\right]& \mathrm{Equation}\left(7\right)\end{array}$

where is the phase shift configured at the -th scattering element of DCS d. As also mentioned above, c.sub.d denotes the codeword of length T used for DCS d, where c.sub.d=[c.sub.d.sup.1, c.sub.d.sup.2, . . . , c.sub.d.sup.T] and is the -th component of c.sub.d. When Hadamard or DFT based codes are used, where the codeword components are of the form =, then c.sub.d=[e.sup.j.sup.d.sup.1, e.sup.j.sup.d.sup.2, . . . , e.sup.j.sup.d.sup.T]. A codeword component is applied on top of the scattering pattern F.sub.d(.sub.d) by adding to the phases of the scattering elements an additional phase shift of , thus obtaining the phase shifts to be applied to DCS d at time interval as follows:

[00006]$\begin{array}{cc}\begin{array}{cc}={}_d+& =\left[{}_d^1,{}_d^2,.Math.,{}_d^S\right]+\\ & =\left[{}_d^1+,{}_d^2+,.Math.,{}_d^S+\right]\end{array}& \mathrm{Equation}\left(8\right)\end{array}$

[0109] The equation above represents the coded phase shift at DCS d due to codeword component =. As can be seen from Equation (8), the phase of each scattering element is shifted by the same amount and thus does not change the scattering pattern of the DCS, apart from a phase shift.

[0110] A model of the scattering pattern F.sub.d(.sub.d) for a DCS d with S.sub.d scattering elements is given by a diagonal matrix

[00007]$\begin{array}{cc}{F}_d\left({}_d\right)=\mathrm{diag}\left({}_d^1{e}^{j{}_d^1},{}_d^2{e}^{j{}_d^2},.Math.,,.Math.,{}_d^{S_d}{e}^{j{}_d^{S_d}}\right),& \mathrm{Equation}\left(9\right)\end{array}$

where, as mentioned above, .sub.d=[.sub.d.sup.1, .sub.d.sup.2, . . . , , . . . , .sub.d.sup.S.sup.d] and is the phase shift configured at the -th scattering element of DCS d, and where represents the amplitude change due to DCS d element which is related to the radar cross section of the scattering element. Using the coded phase shift defined in Equation (8) in the model in Equation (9) results in the following coded scattering pattern at DCS d due to codeword component :

[00008]$\begin{array}{cc}\begin{array}{cc}\left(\right)& =F_d\left({}_d+\right)\\ & =\mathrm{diag}\left({}_d^1{e}^{j{}_d^1+j},{}_d^2{e}^{j{}_d^2+j},.Math.,{+j}^{},.Math.,{}_d^{S_d}{e}^{j{}_d^{S_d}+}\right)\\ & =e^j\mathrm{diag}\left({}_d^1{e}^{j{}_d^1},{}_d^2{e}^{j{}_d^2},.Math.,j^{},.Math.,{}_d^{s_d}{e}^{j{}_d^{S_d}}\right)\\ & =e^j{F}_d\left({}_d\right)\end{array}.& \mathrm{Equation}\left(10\right)\end{array}$

[0111] Thus, since = the coded scattering pattern at DCS d due to codeword component can also be written as

[00009]$\begin{array}{cc}\left(\right)=F_d\left({}_d\right)& \mathrm{Equation}\left(11\right)\end{array}$

[0112] Applying the codeword c.sub.d=[c.sub.d.sup.1, c.sub.d.sup.2, . . . , , . . . , c.sub.d.sup.T] for DCS at time intervals 1, 2, . . . , T results in the coded scattering pattern sequence described as

[00010]$\begin{array}{cc}\left[F_d^1\left({}_d^1\right),F_d^2\left({}_d^2\right),.Math.,\left(\right),.Math.,F_d^T\left({}_d^T\right)\right]=\left[c_d^1{F}_d\left({}_d\right),c_d^2{F}_d\left({}_d\right),.Math.,F_d\left({}_d\right),.Math.,c_d^T{F}_d\left({}_d\right)\right],& \mathrm{Equation}\left(12\right)\end{array}$

or equivalently as

[00011]$\begin{array}{cc}\left[F_d^1\left({}_d^1\right),F_d^2\left({}_d^2\right),.Math.,\left(\right),.Math.,F_d^T\left({}_d^T\right)\right]=\left[e^{j{}_d^1}{F}_d^1\left({}_d^1\right),,e^{j{}_d^2}{F}_d^2\left({}_d^2\right),.Math.,e^j\left(\right),.Math.,e^{j{}_d^T}{F}_d^T\left({}_d^T\right)\right]& \mathrm{Equation}\left(13\right)\end{array}$

when the codeword components are of the form =.

Embodiment for the Coding Time Interval Assignment Step, the Transmission Signal Assignment Step and the Signal Component Separation and Channel Estimation Step for the Case of Downlink, SISO and DCS Coding Over Multiple OFDM Symbols

[0113] As mentioned above, in the coding time interval assignment step, one or more coding time intervals are defined during which the DCSs will apply the coded scattering pattern sequence. In this embodiment, a single coding time interval .sub.1 is used. Given the codewords c.sub.1, c.sub.2, . . . , c.sub.D defined in the codeword assignment step where, as mentioned above, each codeword is of size T, a duration of .sub.1 equal to the duration of T OFDM symbols is defined. The coding time interval .sub.1 is divided into T subintervals labeled as .sub.1, 2, . . . , .sub.t, . . . .sub.T. Thus, if the duration of one OFDM symbol is equal to .sub.OFDM seconds, then the duration of .sub.1 is equal to T.sub.OFDM seconds and the duration of a subinterval it is equal to .sub.OFDM seconds. Furthermore, in this embodiment, as part of the coding time interval assignment step, the coding interval .sub.1 is defined to start at the (+1)-th OFDM symbol.

[0114] In the transmission signal assignment step, the signal that is transmitted during the coding time interval .sub.1 is defined. In this embodiment, the single input, single output (SISO) case is considered, where the BS has one transmit antenna and each of the UEs has one receive antenna. The signal transmitted during the -th OFDM symbol by the BS is denoted as (t).

[0115] Since the coding interval .sub.1 has been defined in the coding time interval assignment step to start at symbol +1 and to last T OFDM symbols in the transmission signal assignment step, the signals (t), xe+.sub.2(t), . . . , (t) are defined. In this embodiment, the signal transmitted during the coding interval .sub.1 is defined to be the same and equal to x(t) for all the T OFDM symbols, hence +(t)=(t)= . . . =(t)=x(t). FIG. 6 shows a time diagram of the transmitted signal and the coded scattering pattern sequence at the DCS d applied during coding time interval .sub.1 as defined in this embodiment. In this embodiment, DCS d applies the coded scattering pattern sequence [c.sub.d.sup.1F.sub.d(.sub.d), c.sub.d.sup.2F.sub.d(.sub.d), . . . , c.sub.d.sup.tF.sub.d(.sub.d), . . . , c.sub.d.sup.TF.sub.d(.sub.d)] during transmission of the OFDM symbols +1, +2 until +T which correspond to the coding time interval .sub.1. The signal transmitted during that time interval is equal to x(t).

[0116] Since, in this embodiment, OFDM waveforms are used, the transmitted and received signals can be expressed as follows. For an OFDM symbol consisting of N.sub.c orthogonal subcarriers, the frequency domain representation of the transmitted signal (t) can be written as ==[, , . . . , , . . . , ] where is a complex scalar that represents the information transmitted on the -th subcarrier, and the -th OFDM symbol. Assuming all non-DCS and DCS paths arrive within the cyclic prefix, then, after proper cyclic prefix removal, the frequency domain representation of the received signal in the downlink at user k subcarrier due to transmission of by the BS can be written as

[00012]$\begin{array}{cc}{y}_{,k,}=H_{0,k,}{X}_{,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}{X}_{,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)X_{,}& \mathrm{Equation}\left(14\right)\end{array}$

where H.sub.0,k, and H.sub.DCS.sub.d.sub.,k, are scalars that represent the non-DCS and the DCS d channel frequency response, respectively, at subcarrier for user k. Equation (14) has the same form as Equation (1), but is written in the frequency domain.

[0117] In the following, the effect that the scattering pattern F.sub.d(.sub.d) and the coded scattering pattern F.sub.d(.sub.d) have on the DCS channel H.sub.DCS.sub.d.sub.,k will be described. For a given scattering pattern F.sub.d (.sub.d), the DCS channel can be written as a product of three matrices

[00013]$\begin{array}{cc}{H}_{DC{S}_d,k,}=H_{DC{S}_d.fwdarw.U{E}_k,}{F}_d\left({}_d\right)H_{BS.fwdarw.{\mathrm{DCS}}_d,}& \mathrm{Equation}\left(15\right)\end{array}$

where H.sub.DCS.sub.d.sub..fwdarw.UE.sub.k.sub., is the channel between DCS d and UE k at subcarrier and H.sub.BS.fwdarw.DCS.sub.d.sub., is the channel between the BS and DCS d at subcarrier a. In the case of SISO and a DCS d with S.sub.d scattering elements, the matrix H.sub.DCS.sub.d.sub..fwdarw.UE.sub.k.sub., is of size 1S.sub.d and the matrix H.sub.BS.fwdarw.DCS.sub.d.sub., is of size S.sub.d1. If, instead of using the scattering pattern F.sub.d(.sub.d), the coded scattering pattern F.sub.d (.sub.d) is used, then the channel can be written as

[00014]$\begin{array}{cc}{c}_d^{}{H}_{DC{S}_d,k,}& \mathrm{Equation}\left(16\right)\end{array}$

since this is what is obtained by replacing F.sub.d(.sub.d) with F.sub.d(.sub.d) in Equation (15) and then simplifying as follows, using that is a scalar.

[00015]$\begin{array}{cc}{H}_{DC{S}_d.fwdarw.U{E}_k,}\left(c_d^{}{F}_d\left({}_d\right)\right)H_{BS.fwdarw.DC{S}_d,}=c_d^{}\left(H_{DC{S}_d.fwdarw.U{E}_k,}{F}_d\left({}_d\right)H_{BS.fwdarw.{\mathrm{DCS}}_d,}\right)=c_d^{}{H}_{DC{S}_d,k,}& \mathrm{Equation}\left(17\right)\end{array}$

[0118] Assuming all transmissions of interest happen within the channel coherence time (i.e. the channels H.sub.0,k,, H.sub.DCS.sub.d.sub..fwdarw.UE.sub.k.sub., and H.sub.BS.fwdarw.DCS.sub.d.sub., remain constant), the signal received at UE k at the DCS operation step (as mentioned above this step corresponds to over-the-air transmission and reception and applying DCS coding during the coding time interval .sub.1) can be written as in Equation (14) when using the scattering pattern without coding, F.sub.d(.sub.d), and as

[00016]$\begin{array}{cc}{y}_{,k,}=H_{0,k,}{X}_{,}+\underset{d=1}{\overset{D}{.Math.}}{c}_d^{}{H}_{DC{S}_d,k,}{X}_{,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{c}_d^{}{H}_{DC{S}_d,k,}\right)X_{,}& \mathrm{Equation}\left(18\right)\end{array}$

when using the scattering pattern F.sub.d(.sub.d) with coding. This follows from the derivations in Equation (15), Equation (16) and Equation (17). For illustration, a time diagram with transmitted and received signals in the downlink is shown in FIG. 7. The timing diagram illustrates the signal sent by the BS on subcarrier and the signal received at UE k subcarrier during OFDM symbols without DCS coding (outside the coding time interval .sub.1) and with DCS coding (inside the coding time interval .sub.1) for the downlink SISO case.

[0119] Using Y.sub..sub.1.sub.,k, to denote the received downlink signal for an OFDM symbol outside the coding time interval .sub.1 and to denote the received downlink signal for subinterval (which corresponds to OFDM symbol +t), Equation (14) and Equation (18), respectively, are rewritten as below, where the signals are further rewritten in matrix form, hence

[00017]$\begin{array}{cc}{Y}_{.Math.{}_1,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{DC{S}_d,k,}\right)X_{,}=\left[1,1,.Math.,1\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{,}& \mathrm{Equation}\left(19\right)\end{array}$$\mathrm{and}$$\begin{array}{cc}{Y}_{{}_{},k,}=Y_{+,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{c}_d^{}{H}_{DC{S}_d,k,}\right)X_{+,}=\left[1,c_1^{},.Math.,c_D^{}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{+t,}=\left[1,c_1^{},.Math.,c_D^{}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{}^{}& \mathrm{Equation}\left(20\right)\end{array}$

where it was used that during the coding interval .sub.1 the transmitted signal is fixed to x(t) which is an OFDM symbol and, hence, can be written in the frequency domain as X=[X.sub.1, X.sub.2, . . . , X.sub., . . . , X.sub.N.sub.c] so that +, =X.sub.. Also in Equation (20), it was used that at OFDM symbol + (i.e. at subinterval ) the DCS d uses codeword component .

[0120] In the following, the signal component separation and channel estimation step where knowledge of the received signals, Y.sub..sub.1.sub.,k,, Y.sub..sub.2.sub.,k,, . . . , Y.sub..sub.T.sub.,k,, and the codewords used by the DCSs, namely c.sub.1, c.sub.2, . . . , c.sub.D, is used to obtain the non-DCS signal component H.sub.0,k,X.sub. and the DCS signal components H.sub.Dcs.sub.1.sub.,k,X.sub., H.sub.DCS.sub.2.sub.,k,X.sub., . . . , H.sub.DCS.sub.D.sub.,k,X.sub., and to further estimate the non-DCS channel H.sub.0,k,, and DCS channels H.sub.DCS.sub.1.sub.,k,, H.sub.DCS.sub.2.sub.,k,, . . . , H.sub.DCS.sub.D.sub.,k, will be described. If the T observations Y.sub..sub.1.sub.,k,, Y.sub..sub.2.sub.,k,, . . . , Y.sub..sub.T.sub.,k, are stacked as follows,

[00018]$\begin{array}{cc}{Y}_{{}_1,k,}=\left[\begin{array}{c}{Y}_{{}_1,k,}\\ Y_{{}_2,k,}\\ .Math.\\ Y_{{}_T,k,}\end{array}\right]=\left[\begin{array}{c}1,c_1^1,.Math.,c_D^1\\ 1,c_1^2,.Math.,c_D^2\\ .Math.\\ 1,c_1^T,.Math.,c_D^T\end{array}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{}^{}& \mathrm{Equation}\left(21\right)\end{array}$

the signal received via DCS d during the entire coding interval .sub.1 and without the effect of coding, namely H.sub.DCS.sub.d.sub.,k,X.sub., can be obtained by using Y.sub..sub.1.sub.,k, defined above and the knowledge the code for DCS d, which is c.sub.d. Due to the orthogonality of the chosen codewords (for example Hadamard or DFT as explained in the embodiments for the codeword assignment step), this is obtained as follows:

[00019]$\begin{array}{cc}\begin{array}{c}{c}_d^{*}{Y}_{{}_1,k,}={\left[c_d^T,.Math.,c_d^T\right]}^{*}{Y}_{{}_1,k,}\\ ={\left[c_d^T,.Math.,c_d^T\right]}^{*}\left[\begin{array}{c}{Y}_{{}_1,k,}\\ Y_{{}_2,k,}\\ .Math.\\ Y_{{}_T,k,}\end{array}\right]\\ ={\left[c_d^T,.Math.,c_d^T\right]}^{*}\left[\begin{array}{c}1,c_1^1,.Math.,c_D^1\\ 1,c_1^2,.Math.,c_D^2\\ .Math.\\ 1,c_1^T,.Math.,c_D^T\end{array}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{}^{}\\ =1_{d+1,T}\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{}^{}\\ =H_{{\mathrm{DCS}}_d,k,}{X}_{}^{}\end{array}& \mathrm{Equation}\left(22\right)\end{array}$

where in the last steps of Equation (22), it was used that

[00020]$\begin{array}{cc}\left[c_d^1,.Math.,c_d^T\right]\left[\begin{array}{c}{c}_{d^{}}^1\\ .Math.\\ c_{d^{}}^T\end{array}\right]=\{\begin{array}{c}0\mathrm{for}d{d}^{}\\ 1\mathrm{for}d=d^{}\end{array}& \mathrm{Equation}\left(23\right)\end{array}$

and also

[00021]$\begin{array}{cc}{\left[c_d^1,.Math.,c_d^T\right]}^{*}\left[\begin{array}{c}1\\ .Math.\\ 1\end{array}\right]=0\mathrm{unless}{c}_d^1=c_d^2=.Math.=c_d^T=1.& \mathrm{Equation}\left(24\right)\end{array}$

[0121] Here, [ ]* is used to denote the conjugate of [ ] and 1.sub.d+1,T is a row vector of size T with entry d+1 equal to one and all other entries equal to zero. The multiplication of Y.sub..sub.1.sub.,k,, which is a representation of the signals received at the UE k during the coding time interval .sub.1 by [c.sub.d.sup.1, . . . , c.sub.d.sup.T]* is an application of a linear transformation that is based on conjugate codewords to the representation of the signals received at the UE k during the coding time interval .sub.1.

[0122] From Equation (22), it can be seen that by computing c*.sub.dY.sub..sub.1.sub.,k, one obtains

[00022]$\begin{array}{cc}{H}_{DC{S}_d,k,}{X}_{}^{}& \mathrm{Equation}\left(25\right)\end{array}$

which is a signal component received by the UE k via the DCS d. By computing [1, 1, . . . , 1]Y.sub..sub.1.sub.,k,, which is also an application of a linear transformation, one obtains

[00023]$\begin{array}{cc}{H}_{0,k,}{X}_{}^{}& \mathrm{Equation}\left(26\right)\end{array}$

which is a representation of the signal component received by the UE k via the non-DCS channel. Thus, by applying linear transformations to the representation of the received signals, signal components received via the individual DCSs and via the non-DCS channel can be separated.

[0123] By adding Equation (26) and Equation (25) computed for all D DCSs, one obtains

[00024]$\begin{array}{cc}\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{DC{S}_d,k,}\right)X_{}^{}& \mathrm{Equation}\left(27\right)\end{array}$

[0124] In the equation above, (H.sub.0,k,+.sub.d=1.sup.DH.sub.DCS.sub.d.sub.,k,) is the aggregate channel observed before the coding time interval .sub.1. The aggregate channel can be obtained by means of conventional training which can be performed at an earlier point in time for decoding earlier symbols, or it can be computed from previously received information (e.g. via joint data and channel estimation for OFDM symbols before the coding time interval .sub.1 starts). Using the knowledge of this aggregate channel (H.sub.0,k,+=.sub.d=1.sup.DH.sub.DCS.sub.d.sub.,k,), Equation (27) can be solved for X.sub.. Using the computed X.sub., Equation (26) can be solved for H.sub.0,k, and Equation (25) can be solved for H.sub.DCS.sub.d.sub.,k, for all the D DCS. Thus, an estimate of the non-DCS and DCS channels can be obtained.

[0125] These estimates can later be used for further post-processing to enhance the decoding of X.sub.. In this embodiment a tradeoff is observed: the data symbol X.sub. spans multiple OFDM symbols which reduces the communication rate but results in improved SNR. Thus, a higher Modulation and Coding Scheme (MCS) can be used to avoid rate loss due to the repetition of data during the time slots of coded DCS phases, i.e. during the coding time interval.

Embodiments for the Coding Time Interval Assignment Step, the Transmission Signal Assignment Step and the Signal Component Separation and the Channel Estimation Step for the Case of Downlink, MIMO and DCS Coding Over Multiple OFDM Symbols

[0126] In this embodiment, the downlink multiple input multiple output (MIMO) case is described where the BS has N transmit antennas and the UEs have multiple receive antennas, with M.sub.k denoting the number of receive antennas at each UE k. As part of the coding time interval assignment step, a single coding time interval .sub.1 is defined during which the DCSs will apply the coded scattering pattern sequence. Given codewords c.sub.1, c.sub.2, . . . , c.sub.D defined in the codeword assignment step where, as mentioned above, each codeword is of size T, a duration of .sub.1 equal to the duration of T*N OFDM symbols is defined and the T subintervals of the coding time interval are labeled as .sub.1, 2, . . . , , . . . .sub.T. Furthermore, each of the subintervals is further divided into N subintervals, where is used to denote the n-th subinterval within subinterval . Thus, if the duration of one OFDM symbol is equal to .sub.OFDM seconds, then the duration of is also equal to .sub.OFDM, the duration of is equal to N*.sub.OFDM seconds and the duration of is equal to T*N*.sub.OFDM seconds.

[0127] Furthermore, in this embodiment, as part of the coding time interval assignment step, it is defined that the coding time interval .sub.1 starts at the +1-th OFDM symbol, and it is defined that at subinterval each of the DCSs applies its corresponding codeword components .

[0128] In the transmission signal assignment step, the signal that is transmitted during the coding time interval .sub.1 is defined. A vector (t) of length N is used to denote the signal transmitted at time t and during the -th OFDM symbol by the BS. Since the coding time interval .sub.1 has been defined in the coding time interval assignment step to start at symbol +1 and to last T*N OFDM symbols, in the transmission signal assignment step, the signals (t), (t), . . . , (t) are defined as follows:

[00025]$\begin{array}{cc}{x}_{+\left(-1\right)N+n}\left(t\right)=x_n^{}\left(t\right)\mathrm{for}=1,2,.Math.,T\mathrm{and}\mathrm{for}n=1,2,.Math.,N& \mathrm{Equation}\left(28\right)\end{array}$

[0129] Therefore,

[00026]$$\begin{gathered} \begin{array}{cc}{x}_{+n}\left(t\right)=x_{+N+n}\left(t\right)=x_{+2N+n}\left(t\right)=.Math.=x_{+\left(T-1\right)N+n}\left(t\right)=x_n^{}\left(t\right)\mathrm{for} \\ n=1,2,.Math.,N,& \mathrm{Equation}\left(29\right)\end{array} \end{gathered}$$

which means that at time subinterval the transmitted signal is equal to x.sub.n(t). In the equations above, x.sub.n(t) is a vector of length N representing the signal transmitted by each of the transmitter antennas at time t. FIG. 8 shows a timing diagram of the transmitted signal and the coded scattering pattern sequence at DCS d that is applied during the coding time interval .sub.1 as defined in this embodiment. DCS d applies the coded scattering pattern sequence [c.sub.d.sup.1F.sub.d(.sub.d), c.sub.d.sup.2F.sub.d(.sub.d), . . . , F.sub.d(.sub.d), . . . , c.sub.d.sup.TF.sub.d(.sub.d)] during the transmission of the downlink OFDM symbols +1,+2 until +T*N which correspond to the coding time interval .sub.1.

[0130] Since this embodiment uses OFDM waveforms, the transmitted and received signals can be expressed as follows. For an OFDM symbol consisting of N.sub.c orthogonal subcarriers the frequency domain representation of the transmitted signal (t) can be written as =[, , . . . , , . . . , ], where is a complex matrix of size N1 and N is the number of BS transmitter antennas. This matrix represents the information transmitted on the -th subcarrier at the -th OFDM symbol. Assuming all non-DCS and DCS paths arrive within the cyclic prefix, after proper cyclic prefix removal, the frequency domain representation of the received signal in the downlink at user k and subcarrier due to the transmission of by the BS can be written as

[00027]$\begin{array}{cc}{Y}_{,k,}=H_{0,k,}{X}_{,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{DC{S}_d,k,}{X}_{,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{DC{S}_d,k,}\right)X_{,}& \mathrm{Equation}\left(30\right)\end{array}$

where H.sub.0,k and H.sub.DCS.sub.d.sub.,k, are M.sub.kN matrices, M.sub.k is the number of antennas at UE k and these matrices represent the non-DCS and DCS d channel frequency response at subcarrier for user k. Equation (30) has the same form as Equation (1), but is written in the frequency domain.

[0131] In the following, the effect that the scattering pattern F.sub.d(.sub.d) and the coded scattering pattern F.sub.d(.sub.d) have on the DCS channel H.sub.Dcs.sub.d.sub.,k will be explained. For a given scattering pattern F.sub.d (.sub.d), the DCS channel can be written as a cascade of three matrices as

[00028]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d,k,}=H_{{\mathrm{DCS}}_d.fwdarw.{\mathrm{UE}}_k,}{F}_d\left({}_d\right)H_{\mathrm{BS}.fwdarw.{\mathrm{DCS}}_d,}& \begin{array}{c}\mathrm{Equation}\\ \left(31\right)\end{array}\end{array}$

where, in this case of MIMO downlink, the channel between DCS d and UE k at subcarrier , namely H.sub.DCS.sub.d.sub..fwdarw.UE.sub.k.sub.,, and the channel between the BS and DCS.sub.d at subcarrier , namely H.sub.BS.fwdarw.DCS.sub.d.sub.,, are matrices of size M.sub.kS.sub.d and S.sub.dN, respectively. As mentioned above, S.sub.d is the number of scattering elements at DCS d. If, instead of using the scattering pattern F.sub.d(.sub.d), the coded scattering pattern (.sub.d) is used, then the channel can be written as

[00029]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d,k,}& \begin{array}{c}\mathrm{Equation}\\ \left(32\right)\end{array}\end{array}$

since this is what is obtained by replacing F.sub.d(.sub.d) with F.sub.d(.sub.d) in Equation (31) and then simplifying as follows, using that is a scalar.

[00030]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d.fwdarw.{\mathrm{UE}}_k,}\left(F_d\left({}_d\right)\right)H_{\mathrm{BS}.fwdarw.{\mathrm{DCS}}_d,}=\left(H_{{\mathrm{DCS}}_d.fwdarw.{\mathrm{UE}}_k,}{F}_d\left({}_d\right)H_{\mathrm{BS}.fwdarw.{\mathrm{DCS}}_d,}\right)=H_{{\mathrm{DCS}}_d,k,}& \begin{array}{c}\mathrm{Equation}\\ \left(33\right)\end{array}\end{array}$

[0132] Assuming all transmissions of interest happen within the channel coherence time (i.e. the channels H.sub.0,k,, H.sub.DCS.sub.d.sub..fwdarw.UE.sub.k.sub., and H.sub.BS.fwdarw.DCS.sub.d.sub., remain constant), the signal received at UE k at the DCS operation step (as mentioned above, this step corresponds to over-the-air transmission and reception and to the application of the DCS coding during the coding time interval .sub.1) can be written as in Equation (30) when using the scattering pattern without coding, F.sub.d(.sub.d), and as

[00031]$\begin{array}{cc}{Y}_{,k,}=H_{0,k,}{X}_{,}+\underset{d=1}{\overset{D}{.Math.}}{X}_{,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)X_{,}& \begin{array}{c}\mathrm{Equation}\\ \left(34\right)\end{array}\end{array}$

when using the scattering pattern with coding, F.sub.d(.sub.d). This follows from Equation (31), Equation (32) and Equation (33). For illustration, a timing diagram with transmitted and received signals in the downlink MIMO scenario is shown in FIG. 9. The timing diagram illustrates the signal sent by the BS on subcarrier and the signal received at UE k subcarrier during OFDM symbols without DCS coding (outside time interval .sub.1) and with DCS coding (inside time interval .sub.1) for the downlink MIMO case.

[0133] Using Y.sub..sub.1.sub.,k, to denote the received downlink signal for an OFDM symbol outside interval .sub.1 and denote the received downlink signal for subinterval (which is the received signal for OFDM symbol +(1)N+n), Equation (30) and Equation (34), respectively, can be rewritten as below, where the signals are further rewritten in matrix form so that

[00032]$\begin{array}{cc}{Y}_{.Math.{}_1,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)X_{,}=\left[I_{M_k},I_{M_k},.Math.,I_{M_k}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{,}& \begin{array}{c}\mathrm{Equation}\\ \left(35\right)\end{array}\end{array}$$\mathrm{and}$$\begin{array}{cc}{Y}_{{}_n^{},k,}=Y_{+\left(-1\right)N+n,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}\right)X_{+\left(-1\right)N+n,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}\right)X_{n,}^{}=\left[I_{M_k},c_1^{}{I}_{M_k},.Math.,c_D^{}{I}_{M_k}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{n,}^{}& \begin{array}{c}\mathrm{Equation}\\ \left(36\right)\end{array}\end{array}$

where I.sub.M.sub.k is the identity matrix of size M.sub.k and where it was used that during the interval , the transmitted signal is fixed to x.sub.n(t) which is an OFDM symbol and, hence, can be written in the frequency domain as X.sub.n=[X.sub.n,1, X.sub.n,2, . . . , X.sub.n,, . . . , X.sub.n,N.sub.c]. X.sub.n, is a complex matrix of size N1 and N is the number of BS transmitter antennas. The matrix X.sub.n, represents the information transmitted on the -th subcarrier at time subinterval . In Equation (36), it was further used that at time subinterval , DCS d uses codeword component. .

[0134] In the following, the signal component separation and channel estimation step will be described, where knowledge of the received signals, for =1, 2, . . . , T and for n=1, 2, . . . , N (i.e. the signals received during the coding time interval .sub.1) and the codewords used by the DCSs, namely c.sub.1, c.sub.2, . . . , c.sub.D, are used to separate the non-DCS signal component H.sub.0,k,X.sub.n, and the DCS signal components H.sub.Dcs.sub.1.sub.,k,X.sub.n,, H.sub.DCS.sub.2.sub.,k,X.sub.n, , . . . , H.sub.DCS.sub.D.sub.,k,X.sub.n, from the signals received by the UEs, and to further estimate the non-DCS channel H.sub.0,k, and the DCS channels H.sub.DCS.sub.1.sub.,k,, H.sub.DCS.sub.2.sub.,k,, . . . , H.sub.DCS.sub.D.sub.,k,. Stacking the T*N observations for =1, 2, . . . , T and for n=1, 2, . . . , N and rewriting them as follows

[00033]$\begin{array}{cc}{Y}_{{}_1,k,}=\left[\begin{array}{cccc}{Y}_{{}_1^1,k,}& Y_{{}_1^2,k,}& .Math.& Y_{{}_1^N,k,}\\ Y_{{}_2^1,k,}& Y_{{}_2^2,k,}& .Math.& Y_{{}_2^N,k,}\\ .Math.& .Math.& .Math.& .Math.\\ Y_{{}_T^1,k,}& Y_{{}_T^2,k,}& .Math.& Y_{{}_T^N,k,}\end{array}\right]=\left[\begin{array}{c}{I}_{M_k},c_1^1{I}_{M_k},.Math.,c_D^1{I}_{M_k}\\ I_{M_k},c_1^2{I}_{M_k},.Math.,c_D^2{I}_{M_k}\\ .Math.\\ I_{M_k},c_1^T{I}_{M_k},.Math.,c_D^T{I}_{M_k}\end{array}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]& \begin{array}{c}\mathrm{Equation}\\ \left(37\right)\end{array}\end{array}$

it can be seen that the signal received via DCS d during the entire coding interval .sub.1 and without the effect of coding, namely H.sub.Dcs.sub.d.sub.,k,[X.sub.1,, X.sub.2,, . . . , X.sub.N,], can be obtained by using Y.sub..sub.1.sub.,k, defined above and the knowledge of the code for DCS d, which is c.sub.d. This is obtained as follows due to the orthogonality of the chosen codewords (for example Hadamard or DFT as explained in the embodiments for the codeword assignment step).

[00034]$\begin{array}{cc}{\left[c_d^1{I}_{M_k},.Math.,c_d^T{I}_{M_k}\right]}^{*}{Y}_{{}_1,k,}={\left[c_d^1{I}_{M_k},.Math.,c_d^T{I}_{M_k}\right]}^{*}\left[\begin{array}{c}{I}_{M_k},c_1^1{I}_{M_k},.Math.,c_D^1{I}_{M_k}\\ I_{M_k},c_1^2{I}_{M_k},.Math.,c_D^2{I}_{M_k}\\ .Math.\\ I_{M_k},c_1^T{I}_{M_k},.Math.,c_D^T{I}_{M_k}\end{array}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]=\left[\begin{array}{c}{1}_{{\mathrm{dM}}_k+1,M_k\left(D+1\right)}\\ 1_{{\mathrm{dM}}_k+2,M_k\left(D+1\right)}\\ .Math.\\ 1_{{\mathrm{dM}}_k+M_k\left(D+1\right)}\end{array}\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]=H_{{\mathrm{DCS}}_d,k,}\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]& \begin{array}{c}\mathrm{Equation}\\ \left(38\right)\end{array}\end{array}$

[0135] In the last steps of Equation (38) it was used that

[00035]$\begin{array}{cc}{\left[c_d^1{I}_{M_k},.Math.,c_d^T{I}_{M_k}\right]}^{*}\left[\begin{array}{c}{c}_d^1,I_{M_k}\\ .Math.\\ c_d^T,I_{M_k}\end{array}\right]=\{\begin{array}{c}{0}_{M_k}\mathrm{for}d{d}^{}\\ I_{M_k}\mathrm{for}d=d^{}\end{array}& \begin{array}{c}\mathrm{Equation}\\ \left(39\right)\end{array}\end{array}$$\mathrm{and}\mathrm{also}$$\begin{array}{cc}{\left[c_d^1{I}_{M_k},.Math.,c_d^T{I}_{M_k}\right]}^{*}\left[\begin{array}{c}{I}_{M_k}\\ .Math.\\ I_{M_k}\end{array}\right]=0_{M_k}\mathrm{unless}{c}_d^1=c_d^2=.Math.=c_d^T=1,& \begin{array}{c}\mathrm{Equation}\\ \left(40\right)\end{array}\end{array}$

where 0.sub.M.sub.k is an M.sub.kM.sub.k matrix of all zeros. Here, [ ]* was used to denote the conjugate of [ ] and 1.sub.dM.sub.k.sub.+i,M.sub.k.sub.(D+1) is a row vector of size M.sub.k (D+1) with entry d*M.sub.k+i equal to one and all other entries equal to zero. The multiplication with [c.sub.d.sup.1I.sub.M.sub.k, . . . , c.sub.d.sup.TI.sub.M.sub.k]* is a linear transformation that is based on conjugate codeword components.

[0136] From Equation (38), it can be seen that by computing [c.sub.d.sup.1I.sub.M.sub.k, . . . , c.sub.d.sup.TI.sub.M.sub.k]*Y.sub..sub.1.sub.,k,, one obtains

[00036]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d,k,}\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]& \begin{array}{c}\mathrm{Equation}\\ \left(41\right)\end{array}\end{array}$

and by computing [I.sub.M.sub.k, . . . ,I.sub.M.sub.k]*Y.sub..sub.1.sub.,k,, one obtains

[00037]$\begin{array}{cc}{H}_{0,k,}\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right].& \begin{array}{c}\mathrm{Equation}\\ \left(42\right)\end{array}\end{array}$

[0137] Thus, by applying the linear transformation that is based on the conjugate codeword components, the signal components that are received by the UEs via the non-DCS channel and via the individual DCSs can be separated from each other.

[0138] By adding Equation (42) and Equation (41) computed for all D DCSs, one obtains

[00038]$\begin{array}{cc}\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)\left[X_{1,}^{},X_{2,}^{},.Math.,X_{N,}^{}\right]& \begin{array}{c}\mathrm{Equation}\\ \left(43\right)\end{array}\end{array}$

[0139] In the equation above, (H.sub.0,k,+1H.sub.DCS.sub.d.sub.,k,) is the aggregate channel observed before time interval .sub.1. This channel can be obtained via conventional training that can be performed at an earlier point in time, since it is needed to decode earlier symbols, or it can be computed from previously received information (e.g. via joint data and channel estimation for OFDM symbols before the coding time interval .sub.1 starts). Using the knowledge of the aggregate channel (H.sub.0,k,+.sub.d=1.sup.DH.sub.DCS.sub.d.sub.,k,), Equation (43) can be solved for [X.sub.1,, X.sub.2,, . . . , X.sub.N,]. Using the computed [X.sub.1,, X.sub.2,, . . . , X.sub.N,], Equation (42) can be solved for H.sub.0,k, and Equation (41) can be solved for H.sub.DCS.sub.d.sub.,k, for all D DCS, for example by multiplying by the inverse or pseudo-inverse of [X.sub.1,, X.sub.2,, . . . , X.sub.N,]. Thus, estimates of the non-DCS and DCS channels are obtained. These estimates can later be used for further post-processing to enhance the decoding of [X.sub.1,, X.sub.2,, . . . , X.sub.N,]. In this embodiment, there is a tradeoff: the data symbols [X.sub.1,, X.sub.2,, . . . , X.sub.N,] span multiple OFDM symbols. This reduces the communication rate but results in improved SNR. Thus, a higher Modulation and Coding Scheme (MCS) can be used to avoid rate loss due to the repetition of data during the time slots of coded DCS phases, i.e. during the coding time interval

Embodiments for the Coding Time Interval Assignment Step, the Transmission Signal Assignment Step and the Signal Component Separation and Channel Estimation Step for the Case of Uplink, MIMO and DCS Coding Over Multiple OFDM Symbols

[0140] In this embodiment, an uplink multiple input multiple output (MIMO) case is considered where the BS has N receive antennas and the UEs have multiple transmit antennas. M.sub.k denotes the number of transmit antennas at the k-th UE. Thus, a total number of M=.sub.k=1.sup.KM.sub.k transmit antennas is used for the uplink. As part of the coding time interval assignment step, a single coding time interval .sub.1 during which the DCSs will apply the coded scattering pattern sequence is defined. Given the codewords c.sub.1, c.sub.2, . . . , c.sub.D defined in the codeword assignment step where, as mentioned above, each codeword is of size T, in this embodiment a duration of T.sub.1 equal to the duration of T*M OFDM symbols is defined. This coding time interval .sub.1 is divided into T subintervals labeled as .sub.1, .sub.2, . . . , , . . . , .sub.T. Each of the subintervals is further divided into M subintervals where is used to denote the m-th subinterval within subinterval . Thus, if the duration of one OFDM symbol is equal to .sub.OFDM seconds, then the duration of is also equal to .sub.OFDM, the duration of is equal to M*.sub.OFDM and the duration of .sub.1 is equal to T*M*.sub.OFDM seconds. Furthermore, in this embodiment, as part of the coding time interval assignment step, the coding time interval .sub.1 is defined to start at the +1-th OFDM symbol and it is defined that at subinterval .sub.t, each of the DCSs applies each its corresponding codeword component .

[0141] In the transmission signal assignment step, the signal that is transmitted during the coding time interval .sub.1 is defined. A vector (t) of length M.sub.k is used to denote the signal transmitted at time t and during the -th OFDM symbol by UE k. Since the coding time interval .sub.1 has been defined in the coding time interval assignment step to start at symbol +1 and to last T*M OFDM symbols, in the transmission signal assignment step the signals (t), (t), . . . , (t) for all users k=1, 2, . . . K are defined as follows:

[00039]$\begin{array}{cc}{x}_{+\left(-1\right)M+m,k}\left(t\right)=x_{m,k}^{}\left(t\right)\mathrm{for}=1,2,.Math.,T,\mathrm{for}m=1,2,.Math.,M\mathrm{and}\mathrm{for}k=1,2,.Math.,K& \begin{array}{c}\mathrm{Equation}\\ \left(44\right)\end{array}\end{array}$

[0142] Thus,

[00040]$\begin{array}{cc}{x}_{+m,k}\left(t\right)=x_{+M+m,k}\left(t\right)=x_{+2M+m,k}\left(t\right)=.Math.=x_{+\left(T-1\right)M+m,k}\left(t\right)=x_{m,k}^{}\left(t\right)& \begin{array}{c}\mathrm{Equation}\\ \left(45\right)\end{array}\end{array}$

for m=1, 2, . . . , M and for k=1, 2, . . . K, which means that at the time subinterval the transmitted signal by UE k is equal to x.sub.m,k(t). In the equations above, x.sub.m,k(t) is a vector of length M.sub.k representing the signal transmitted by each of the transmitter antennas of user k at time t. FIG. 10 shows a time diagram of the transmitted signal and the coded scattering pattern sequence at a DCS d that is applied during the coding time interval .sub.1 as defined in this embodiment. The timing diagram shows an example where DCS d applies the coded scattering pattern sequence [c.sub.d.sup.1F.sub.d(.sub.d), c.sub.d.sup.2F.sub.d(.sub.d), . . . , F.sub.d(.sub.d), . . . , c.sub.d.sup.TF.sub.d(.sub.d)] during transmission of UE k's uplink OFDM symbols +1,+2 until +TM which correspond to the coding time interval .sub.1.

[0143] Since this embodiment uses OFDM waveforms, the transmitted and received signals can be expressed as follows. For an OFDM symbol consisting of N.sub.c orthogonal subcarriers, the frequency representation of the transmitted signal (t) can be written as =[, , . . . , , . . . , ], where is a complex matrix of size M.sub.k1 that represents the information transmitted on the M.sub.k transmitters antenans of UE k on the -th subcarrier at the -th OFDM symbol. Assuming signal components of all non-DCS and DCS paths from all users arrive within the cyclic prefix then, after proper cyclic prefix removal, the frequency domain representation of the received signal in the uplink from UE k at subcarrier due to transmission of by user k can be written as

[00041]$\begin{array}{cc}{Y}_{,k,}=H_{0,k,}{X}_{,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}{X}_{,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)X_{,k,}& \begin{array}{c}\mathrm{Equation}\\ \left(46\right)\end{array}\end{array}$

where H.sub.0,k, and H.sub.DCS.sub.d.sub.,k, are NM.sub.k matrices. These matrices represent the non-DCS and DCS d channel frequency response, respectively, at subcarrier for user k. Equation (46) has the same form as Equation (1) but is written in the frequency domain.

[0144] In the following, the effect that the scattering pattern F.sub.d(d) and the coded scattering pattern (.sub.d) have on the DCS channel H.sub.Dcs.sub.d.sub.,k will be explained. It is known that for a given scattering pattern F.sub.d (.sub.d), the DCS channel can be written as a cascade of three matrices as

[00042]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d,k,}=H_{{\mathrm{DCS}}_d.fwdarw.\mathrm{BS},}{F}_d\left({}_d\right)H_{{\mathrm{UE}}_k.fwdarw.{\mathrm{DCS}}_d,}& \begin{array}{c}\mathrm{Equation}\\ \left(47\right)\end{array}\end{array}$

where, in this case of MIMO uplink, the channel between DCS d and the BS at subcarrier a, namely H.sub.DCS.sub.d.sub..fwdarw.BS,, and the channel between UE k and DCS d at subcarrier a, namely H.sub.UE.sub.k.sub..fwdarw.DCS.sub.d.sub., are matrices of size NS.sub.d and S.sub.dM.sub.k, respectively. As mentioned above, S.sub.d is the number of scattering elements at DCS d. If, instead of using the scattering pattern F.sub.d(.sub.d), the coded scattering pattern (.sub.d) is used, then the channel can be written as

[00043]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d,k,}& \mathrm{Equation}\left(48\right)\end{array}$

since this is what is obtained by replacing F.sub.d(.sub.d) with F.sub.d(.sub.d) in Equation (47) and then simplifying as follows using the fact that is a scalar:

[00044]$\begin{array}{cc}{H}_{{\mathrm{DCS}}_d.fwdarw.\mathrm{BS},}\left(F_d\left({}_d\right)\right)H_{{\mathrm{UE}}_k.fwdarw.{\mathrm{DCS}}_d,}=\left(H_{{\mathrm{DCS}}_d.fwdarw.\mathrm{BS},}{F}_d\left({}_d\right)H_{{\mathrm{UE}}_k.fwdarw.{\mathrm{DCS}}_d,}\right)=H_{{\mathrm{DCS}}_d,k,}& \mathrm{Equation}\left(49\right)\end{array}$

[0145] Assuming all transmissions of interest happen within the channel coherence time (i.e. the channels H.sub.0,k,, H.sub.DCS.sub.d.sub..fwdarw.BS and H.sub.UE.sub.k.sub..fwdarw.DCS.sub.d.sub., remain constant), the signal received at the BS at the DCS operation step (as mentioned above this step corresponds to over-the-air transmission and reception and applying DCS coding during the coding time interval .sub.1) can be written as in Equation (46) when using the scattering pattern without coding, F.sub.d(.sub.d), and as

[00045]$\begin{array}{cc}{Y}_{,k,}=H_{0,k,}{X}_{,k,}+\underset{d=1}{\overset{D}{.Math.}}{X}_{,k,}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}\right)X_{,k,}& \mathrm{Equation}\left(50\right)\end{array}$

when using the scattering pattern with coding, F.sub.d(.sub.d). This follows from Equation (47), Equation (48) and Equation (49). For illustration, a timing diagram with transmitted and received signals in the uplink MIMO scenario is shown in FIG. 11. The timing diagram illustrates the signal sent by UE k on subcarrier and the signal received at BS from UE k at subcarrier during OFDM symbols without DCS coding (outside time interval .sub.1) and with DCS coding (inside time interval .sub.1) for the uplink MIMO case.

[0146] Using Y.sub..sub.1.sub.,k, to denote the received uplink signal for an OFDM symbol outside the coding time interval .sub.1 and to denote the received uplink signal for subinterval (which is the received signal for OFDM symbol +(1)M+m), Equation (46) and Equation (50), respectively, can be rewritten as below where the signals have further been rewritten in matrix form. Accordingly,

[00046]$\begin{array}{cc}=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}{H}_{{\mathrm{DCS}}_d,k,}\right)X_{,k,}=\left[I_N,I_N,...,I_N\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{,k,}& \mathrm{Equation}\left(51\right)\end{array}$$\mathrm{and}$$\begin{array}{cc}==\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}\right)=\left(H_{0,k,}+\underset{d=1}{\overset{D}{.Math.}}\right)X_{m,k,}^{}=\left[I_N,,...,I_N\right]\left[\begin{array}{c}{H}_{0,k,}\\ H_{{\mathrm{DCS}}_1,k,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,k,}\end{array}\right]X_{m,k,}^{}& \mathrm{Equation}\left(52\right)\end{array}$

where I.sub.N is the identity matrix of size N. Here, it was used that during the interval the transmitted signal for user k is fixed to x.sub.m,k(t) which is an OFDM symbol that can be written in the frequency domain as X.sub.m,k=[X.sub.m,k,1, X.sub.m,k,2, . . . , X.sub.m,k,, . . . , X.sub.m,k,N.sub.c]. X.sub.m,k, is a complex matrix of size M.sub.k1. M.sub.k is the number of transmitter antennas at the UE and the matrix X.sub.m,k, represents the information transmitted on the -th subcarrier at time subinterval from UE k. Also, in Equation (52), it was used that at time subinterval DCS d uses codeword component .

[0147] Taking into account the contribution from all the K users for an OFDM symbol outside interval .sub.1, the received signal is obtained using Equation (51) as follows:

[00047]$\begin{array}{cc}{Y}_{.Math.{}_1,}=\underset{k=1}{\overset{K}{.Math.}}{Y}_{.Math.{}_1,k,}=\left[I_N,I_N,...,I_N\right]\left[\begin{array}{c}{H}_{0,1,}\\ H_{{\mathrm{DCS}}_1,1,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,1,}\end{array}\right]X_{,1,}+.Math.+\left[I_N,I_N,...,I_N\right]\left[\begin{array}{c}{H}_{0,K,}\\ H_{{\mathrm{DCS}}_1,K,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,K,}\end{array}\right]X_{,K,}=\left[I_N,I_N,...,I_N\right]\left[\begin{array}{cccc}{H}_{0,1,}& H_{0,2,}& .Math.& H_{0,K,}\\ H_{{\mathrm{DCS}}_1,1,}& H_{{\mathrm{DCS}}_1,2,}& & H_{{\mathrm{DCS}}_1,K,}\\ .Math.& .Math.& & .Math.\\ H_{{\mathrm{DCS}}_D,1,}& H_{{\mathrm{DCS}}_D,2,}& .Math.& H_{{\mathrm{DCS}}_D,K,}\end{array}\right]\left[\begin{array}{c}{X}_{,1,}\\ X_{,2,}\\ .Math.\\ X_{,K,}\end{array}\right]=H_{.Math.{}_1,}\left[\begin{array}{c}{X}_{,1,}\\ X_{,2,}\\ .Math.\\ X_{,K,}\end{array}\right]& \mathrm{Equation}\left(53\right)\end{array}$

[0148] Herein, H.sub..sub.1.sub., , is a matrix of size NM. The received signal taking account the contribution from all the K users inside interval .sub.1 is obtained using Equation (52) as follows:

[00048]$\begin{array}{cc}=\underset{k=1}{\overset{K}{.Math.}}=\left[I_N,I_N,...,I_N\right]\left[\begin{array}{c}{H}_{0,1,}\\ H_{{\mathrm{DCS}}_1,1,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,1,}\end{array}\right]X_{m,1,}^{}+.Math.+\left[I_N,I_N,...,I_N\right]\left[\begin{array}{c}{H}_{0,K,}\\ H_{{\mathrm{DCS}}_1,K,}\\ .Math.\\ H_{{\mathrm{DCS}}_D,K,}\end{array}\right]X_{m,K,}^{}=\left[I_N,I_N,...,I_N\right]\left[\begin{array}{cccc}{H}_{0,1,}& H_{0,2,}& .Math.& H_{0,K,}\\ H_{{\mathrm{DCS}}_1,1,}& H_{{\mathrm{DCS}}_1,2,}& & H_{{\mathrm{DCS}}_1,K,}\\ .Math.& .Math.& & .Math.\\ H_{{\mathrm{DCS}}_D,1,}& H_{{\mathrm{DCS}}_D,2,}& .Math.& H_{{\mathrm{DCS}}_D,K,}\end{array}\right]\left[\begin{array}{c}{X}_{m,1,}^{}\\ X_{m,2,}^{}\\ .Math.\\ X_{m,K,}^{}\end{array}\right]=H_{{}_1,}\left[\begin{array}{c}{X}_{m,1,}^{}\\ X_{m,2,}^{}\\ .Math.\\ X_{m,K,}^{}\end{array}\right].& \mathrm{Equation}\left(54\right)\end{array}$

[0149] Here, H.sub..sub.1.sub., is a matrix of size NM.

[0150] In the signal component separation and channel estimation step, knowledge of the received signals, is used for =1, 2, . . . , T and for m=1, 2, . . . , M (i.e. the signals received during the coding time interval .sub.1) and the codewords used by the DCSs, namely c.sub.1, c.sub.2, . . . , c.sub.D are used in order to obtain for each user k the non-DCS signal H.sub.0,k,X.sub.m,k, and the DCS signals H.sub.DCS.sub.1.sub.,k,X.sub.m,k,, H.sub.Dcs.sub.2.sub.,k,X.sub.m,k,, . . . , H.sub.DCS.sub.D.sub.,k,X.sub.m,k,, and to further estimate the non-DCS channel H.sub.0,k,, and the DCS channels H.sub.DcS.sub.1.sub.,k,, H.sub.DCS.sub.2.sub.,k,, . . . , H.sub.DCS.sub.D.sub.,k,.

[0151] Stacking the TM observations for =1, 2, . . . , T and for m=1, 2, . . . , the received signals can be rewritten as follows:

[00049]$\begin{array}{cc}{Y}_{{}_1,}=\left[\begin{array}{cccc}{Y}_{{}_1^1,}& Y_{{}_1^2,}& .Math.& Y_{{}_1^M,}\\ Y_{{}_2^1,}& Y_{{}_2^2,}& .Math.& Y_{{}_2^M,}\\ .Math.& .Math.& .Math.& .Math.\\ Y_{{}_T^1,}& Y_{{}_T^2,}& .Math.& Y_{{}_T^M,}\end{array}\right]=\left[\begin{array}{c}{I}_N,c_1^1{I}_N,...,c_D^1{I}_N\\ I_N,c_1^2{I}_N,...,c_D^2{I}_N\\ .Math.\\ I_N,c_1^T{I}_N,...,c_D^T{I}_N\end{array}\right]\left[\begin{array}{cccc}{H}_{0,1,}& H_{0,2,}& .Math.& H_{0,K,}\\ H_{{\mathrm{DCS}}_1,1,}& H_{{\mathrm{DCS}}_1,2,}& & H_{{\mathrm{DCS}}_1,K,}\\ .Math.& .Math.& & .Math.\\ H_{{\mathrm{DCS}}_D,1,}& H_{{\mathrm{DCS}}_D,2,}& .Math.& H_{{\mathrm{DCS}}_D,K,}\end{array}\right][\begin{array}{cccc}{X}_{1,1,}^{}& X_{2,1,}^{}& .Math.& \text{?}\\ X_{1,2,}^{}& X_{2,2,}^{}& & \text{?}\\ .Math.& .Math.& & .Math.\\ X_{1,K,}^{}& X_{2,K,}^{}& .Math.& \text{?}\end{array}\text{?}& \mathrm{Equation}\left(55\right)\end{array}$$\text{?}\text{indicates text missing or illegible when filed}$