METHOD AND APPARATUS FOR ALLOCATING A PLURALITY OF DATA SYMBOLS IN A WIRELESS COMMUNICATION SYSTEM

Abstract

According to one embodiment, a method for transmitting an uplink signal includes transmitting the uplink signal including a block of data symbols. The block of data symbols are mapped to at least two sets of subcarrier blocks. Each data symbol of the block of data symbols is mapped to one of subcarriers of the at least two sets of subcarrier blocks. The at least two sets of subcarrier blocks are not contiguous in frequency. The block of data symbols are mapped in sequence starting with a first data symbol to the at least two sets of subcarrier blocks and in increasing order of subcarrier index.

Claims

1. A method for receiving uplink data symbols, the method performed by a receiving end and comprising: receiving, from a transmitting end, uplink data symbols in at least two subcarrier groups; de-mapping the uplink data symbols from the at least two subcarrier groups; and demodulating the de-mapped uplink data symbols, wherein, starting with a first uplink data symbol, the uplink data symbols have been mapped in sequence to the at least two subcarrier groups in increasing order of a subcarrier index, wherein the at least two subcarrier groups are not adjacent to each other in a frequency domain between neighboring subcarrier groups, and wherein each of the at least two subcarrier groups includes subcarriers that are adjacent in the frequency domain.

2. The method of claim 1, further comprising: allocating a predetermined number of subcarriers to the transmitting end, wherein the at least two subcarrier groups are included in the predetermined number of subcarriers.

3. The method of claim 2, wherein the received uplink data symbols are processed by the transmitting end using a transform precoding.

4. The method of claim 3, wherein the transform precoding is performed by the transmitting end using a Discrete Fourier Transform (DFT).

5. The method of claim 2, wherein all of the subcarriers of the at least two subcarrier groups are orthogonal to each other.

6. The method of claim 2, wherein each of the at least two subcarrier groups varies in size.

7. The method of claim 2, wherein each of the at least two subcarrier groups are equal in size.

8. A receiving end for receiving uplink data symbols, the receiving end comprising: a receiver receiving, from a transmitting end, uplink data symbols transmitted in at least two subcarrier groups; and a subcarrier-to-symbol mapper de-mapping the uplink data symbols from the at least two subcarrier groups; and a demodulator demodulating the de-mapped uplink data symbols, wherein, starting with a first uplink data symbol, the uplink data symbols have been mapped in sequence to the at least two subcarrier groups in increasing order of a subcarrier index, wherein the at least two subcarrier groups are not adjacent to each other in a frequency domain between neighboring subcarrier groups, and wherein each of the at least two subcarrier groups includes subcarriers that are adjacent in the frequency domain.

9. The receiving end of claim 8, wherein the receiving end allocates a predetermined number of subcarriers to the transmitting end, and wherein the at least two subcarrier groups are included in the predetermined number of subcarriers.

10. The receiving end of claim 9, wherein the received uplink data symbols have been processed by the transmitting end using a transform precoding.

11. The receiving end of claim 10, wherein the transform precoding is performed by the transmitting end using a Discrete Fourier Transform (DFT).

12. The receiving end of claim 9, wherein all of the subcarriers of the at least two subcarrier groups are orthogonal to each other.

13. The receiving end of claim 9, wherein each of the at least two subcarrier groups varies in size.

14. The receiving end of claim 9, wherein each of the at least two subcarrier groups are equal in size.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are included to provide a farther understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;

[0021] FIG. 1 illustrates a block diagram of transmitting/receiving ends using an OFDMA scheme in an uplink direction;

[0022] FIGS. 2a-2c illustrate methods of mapping Nu number of subcarriers out of Nc total number of subcarriers;

[0023] FIG. 3 is a block diagram illustrating transmitting/receiving ends using a DFT spread OFDMA scheme;

[0024] FIG. 4 illustrates a subcarrier allocation method according an embodiment of the present invention; and

[0025] FIGS. 5a-5d illustrate subcarrier allocation methods according to other embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0027] Hereinafter, the descriptions of the embodiments will be made with respect to the OFDMA which is one of many a Multiple Carrier Modulation (MCM) scheme. However, that is merely an exemplary scheme and can be allocated using other types of modulation schemes.

[0028] To resolve the ICI problem as well as other problems in the DFT spread OFDMA, system, the following embodiments are provided. As illustrated in FIG. 1, a bit stream of a user (e.g., mobile station) is mapped by a constellation mapping scheme which is then converted by a serial-to-parallel converter. The descriptions provided hereafter with respect to the present invention relate to mapping the data symbols to subcarriers. In the present invention, the processed bit stream is not limited to a bit stream of a single user but can be multiplexed bit streams of more than one user (e.g., bit stream of user 1, bit stream of user 2, and bit stream of user 3). In addition, although the present invention is geared for downlink transmission, the present invention can also be applied to uplink transmissions.

[0029] FIG. 4 illustrates a subcarrier allocation method according an embodiment of the present invention. As illustrated in FIG. 4, a number of data symbols are grouped into a plurality of groups, and these groups comprised of data symbols are allocated. More specifically, in order to achieve frequency diversity in an OFDMA system, Nu number of data symbols are allocated across the entire frequency band having Ne number of subcarriers when Ns number of neighboring data symbols are formed into a group, making a total of Ng number of data symbol groups (i.e., Nu=Ng×Ns). That is, Nu number of data symbols is grouped based on proximity of data symbols (e.g., neighboring data symbols). Usually, the grouping occurs based on close proximity of the data symbols with respect to each other. The break up of Nu number of data symbols is based on Ng number of data symbol groups, which contains Ns number of elements or data symbols. For example, assuming Nu=12, if four data symbol groups are formed (Ng=4), then the data symbols that are in close proximity form a data symbol group of three data. Symbols (Ns=3). This is depicted in FIG. 4.

[0030] Thereafter, the data symbol groups are allocated to subcarrier groups. Here, each data symbol group is allocated to each subcarrier group, where each subcarrier group comprises a plurality of subcarriers. In allocating each data symbol group to each subcarrier group, an ICI should affect only the subcarriers located on the periphery of the data symbol group so as to express strong characteristics of the ICI. Preferably, the subcarrier groups are offset or spaced apart a certain distance between neighboring subcarrier groups. Furthermore, it is preferable to allocate groups by distributing the subcarrier groups across the entire frequency band.

[0031] FIGS. 5a-5d illustrate subcarrier allocation methods according to other embodiments of the present invention. More specifically, these embodiments illustrate application of the DFT spread OFDMA scheme.

[0032] In FIG. 5a, after being processed by the serial-to-parallel converter, Nu number of data symbols are precoded or spread by a precoding module. Here, the precoding module uses Nu-point DFT scheme. Thereafter, the output values (e.g., precoded data symbols) spaced apart at specified intervals (e.g., every fourth precoded data symbol) are joined to form a data symbol group. The grouping of precoded data symbols are performed until all of the precoded data symbols are placed in data symbol groups. Here, No number of precoded data symbols are grouped into Ng number of data symbol groups and each data symbol group consists of Ns number of precoded data symbols. Subsequently, these data symbol groups are allocated to subcarrier groups whose group formation corresponds to the data symbol groups. Each subcarrier group is formed by combining a certain number of subcarriers from Nc number of subcarriers. Here, the data symbols can be transmitted from more than one mobile station.

[0033] For example, if Nu=12 and Nc=24 and the DFT output values are {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, these output values are grouped into data symbol groups (e.g., {1, 5, 9}, {2, 6, 10}, {3, 7, 11}, {4, 8, 12}) where there are four (4) data symbol groups, Ng=4, and three precoded data symbols per each group, Ns=3. In this example, the size of Ns is set to 3 data symbols. However, the size of Ns can vary and does not have to be fixed. In other words, each data symbol group can have different size of Ns. For example, the data groups having different number of data symbols per group can be assembled, such as {1, 4, 9}, {2, 10}, {3, 6, 8, 11}, {5, 7, 12}.

[0034] Once the formation of the data symbol groups are completed, each data symbol group (Ng) is allocated to respective subcarrier groups (e.g., {1, 2, 3}, {7, 8, 9}, {13, 14, 15}, {19, 20, 21} or {4, 5, 6}, {10, 11, 12}, {16, 17, 18}, {22, 23, 24}) which are formed by grouping Nc number of subcarriers. Here, the subcarriers of the subcarriers groups are localized. That is, the subcarriers of each subcarrier group are adjacent to each other or put differently, are neighboring subcarriers. However, grouping of subcarriers for the subcarrier group is not limited to grouping localized or neighboring subcarriers. The subcarrier groups can group subcarriers that are not close to each other. That is, the subcarriers of each subcarrier group can have various patterns. As such, non-localized subcarriers or subcarriers that are dispersed can be grouped to form each subcarrier group. (e.g., {1, 9, 17}, {3, 11, 19}, {5, 13, 21}, {7, 15, 23}).

[0035] In addition, the size of each subcarrier group which corresponds to the size of the data symbol group does not have to be fixed. As described above, each data symbol group size can vary. Accordingly, to correspond with the varying data symbol group size, the subcarrier group can vary as well. That is, each subcarrier group can be of different size (e.g., {1, 2}, {6, 7, 8, 9}, {14, 15, 16}, {19, 20, 21, 22})

[0036] By combining the non-localized subcarriers with different subcarrier group size, it is also possible for the subcarrier group to have different size subcarrier groups, in which the subcarrier groups are dispersed and not localized. For example, the subcarrier groups can be {1, 7}, {4, 9, 15, 24}, {2, 10}, {5, 12, 21}).

[0037] As described above, the data symbol groups can have a fixed as well as a varying group size. In addition, the subcarrier groups can also be fixed and/or varying as well. This is true since the size of subcarrier groups correspond to the size of the data symbols. Moreover, the subcarriers included in the subcarrier groups are either localized subcarriers or non-localized (dispersed) subcarriers. Here, the detailed description of the data symbol groups and the subcarrier groups is not limited to FIG. 5a but can also be applied to the embodiments of FIGS. 5b-5d.

[0038] In FIG. 5b, after being processed by the serial-to-parallel converter, Nu number of data symbols are precoded (or spread) by a precoding module. Here, the precoding module uses Nu-point DFT scheme. Thereafter, Ns number of neighboring DFT output values are grouped, totaling Ng number of data symbol groups. Here, the neighbor DFT output values represent values that are close each other. Thereafter, the data symbol groups, consisting of the DFT output values coded data symbols), are allocated to subcarriers groups, each of which correspond to each data symbol group. Each subcarrier group is formed by combining a certain number of subcarriers from Nc number of subcarriers and has the same group formation as the data symbol group.

[0039] For example, if Nu=12 and Nc=24 and the DFT output values (i.e., precoded data symbols) are {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, these output values or data symbols are grouped into data symbol groups (e.g., {1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10, 11, 12}) where there are four (4) data symbol groups, Ng=4, and three data symbols per group, Ns=3. Once the formation of the data symbol groups are completed, each data symbol group is allocated to subcarrier groups (e.g., {1, 2, 3}, {7, 8, 9}, {13, 14, 15}, {19, 20, 21} or {4, 5, 6}, {10, 11, 12}, {16, 17, 18}, {22, 23, 24}) which are formed by grouping Nc number of subcarriers.

[0040] In FIG. 5c, after being processed by the serial-to-parallel converter, Nu number of data symbols are spread (precoded) by Ng number of precoding or spreading modules. Here, the precoding module uses Ng-point DFT spreading scheme. Thereafter, the precoded data symbols are outputted to different parts of the frequency band. For example, if there are four outputted values from a precoding module, each of these four outputted data symbols are spread apart so that they are evenly spaced apart across the frequency band. As illustrated in FIG. 5c, there are Ng number of precoding modules, and each precoding module processes Ns number of data symbols. The outputted precoded data symbols from each precoding module are spaced apart in equal intervals. Thereafter, precoded data symbols from each precoding module spaced apart at specified intervals are grouped into data symbol groups to which subcarriers groups are allocated. Preferably, for example, each data symbol group combines only one outputted precoded data symbol from each precoding module. Each subcarrier group is formed by combining a certain number of subcarriers from Nc number of subcarriers.

[0041] For example, if Nu=12 and Nc=24 and a 4-point DFT output values are, in order, {1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, the output values are grouped into four data symbol groups (e.g., {1, 5, 9}, {2, 6, 10}, {3, 7, 11}, {4, 8, 12}) where Ng=4 having three precoded data symbols in each data symbol group, Ns=3. Once the formation of the data symbol groups are completed, each data symbol group is allocated to subcarrier groups (e.g., {1, 2, 3}, {7, 8, 9}, {13, 14, 15}, {19, 20, 21} or {4, 5, 6}, {10, 11, 12}, {16, 17,18}, {22, 23, 24}) which are formed by grouping Nc number of subcarriers.

[0042] in FIG. 5d, after being processed by the serial-to-parallel converter, Nu number of data symbols are spread by Ng number of precoding modules. Here, the precoding module employs Ns-point DFT scheme. Thereafter, the precoded data symbols are outputted to different parts of the frequency band. As illustrated in FIG. 5d, there are Ng number of precoding modules, each module processing Ns number of data symbols. Here, Ns number of outputted precoded data symbols, considered to be neighboring DFT output values, are grouped, totaling Ng number of data symbol groups. Here, the neighbor DFT output values represent values that are close each other. Thereafter, the data symbol groups are allocated to subcarrier groups. Each subcarrier group is formed by combining a certain number of subcarriers from Nc number of subcarriers.

[0043] For example, if Nu=12 and Nc=24 and a 3-point DFT output values are, in order, {1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10, 11, 12}, the output values are grouped into data symbol groups where Ng=4 and Ns=3. Once the formation of the data symbol groups are completed, each data symbol group is allocated to subcarrier groups (e.g., {1, 2, 3}, {7, 8, 9}, {13, 14, 15}, {19, 20, 21} or {4, 5, 6}, {10, 11, 12}, {16, 17, 18}, {22, 23, 24}) which are formed by grouping Nc number of subcarriers.

[0044] in another embodiment of the present invention, an apparatus for allocating the data symbols can he found. The apparatus includes a subcarrier-to-symbol mapping module through which the data symbols are grouped and mapped to at least one subcarrier group. The apparatus further includes a transmitting module for transmitting the data symbols on the subearriers of the at least one subcarrier group to a receiving end. Since the operations are same as described above with respect to FIGS. 5a-5d, further discussions of the operations will be omitted. For details, refers to the descriptions of FIGS. 5a-5d.

[0045] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.