Control channel signalling for triggering the independent transmission of a channel quality indicator

Abstract

A communication apparatus has a receiver and a transmitter. The receiver, in operation receives a control signal including a Modulation and Coding Scheme (MCS) Index, a channel quality indicator (CQI) trigger and information indicating uplink resource blocks. The transmitter in operation, determines whether to multiplex an aperiodic CQI report with data in an uplink signal based on the MCS Index, the channel quality indicator trigger, the information indicating uplink resource blocks, and a threshold number of resource blocks, and transmits the uplink signal.

Claims

1. A terminal, comprising: a receiver, which, in operation, receives control channel signals transmitted by a base station, the control channel signals including a modulation and coding scheme (MCS) index, uplink resource block assignment information and a channel quality indicator trigger; and a transmitter, which, in operation, transmits a channel quality indicator report to the base station in response to the channel quality indicator trigger, wherein a transmission mode of the channel quality indicator report is selected from a plurality of channel quality indicator report transmission modes based on a comparison of a number of resource blocks indicated by the uplink resource block assignment information to a threshold number of resource blocks.

2. The terminal of claim 1, comprising a buffer, which, in operation, buffers data to be transmitted to the base station in response to reception of the control channel signals, and the transmitter, in operation, waits for a signal from the base station before resuming data transmission.

3. The terminal of claim 1 wherein the plurality of channel quality indicator report transmission modes include an aperiodic channel quality indicator reporting mode, in which the transmitter, in operation, transmits an aperiodic channel quality indicator to the base station without multiplexing the aperiodic channel quality indicator with user data in an uplink transport block.

4. The terminal of claim 3 wherein the control channel signals indicate a redundancy/constellation version parameter of a user data retransmission and the transmitter, in operation, transmits the channel quality indicator report using the aperiodic channel quality indicator reporting mode in response to the redundancy/constellation version parameter being equal to a determined value.

5. The terminal of claim 4 wherein the determined value of the redundancy/constellation version parameter is 1.

6. The terminal of claim 1 wherein the plurality of channel quality indicator report transmission modes have a same indication of spectral efficiency.

7. The terminal of claim 1 wherein the plurality of channel quality indicator report transmission modes are associated with code rates that are equal to or larger than a threshold code rate.

8. A method, comprising: receiving, by a terminal, control channel signals transmitted by a base station, the control channel signals including a modulation and coding scheme (MCS) index, uplink resource block assignment information and a channel quality indicator trigger; selecting, by the terminal, a channel quality indicator report transmission mode from a plurality of channel quality indicator report transmission modes based on a comparison of a number of resource blocks indicated by the uplink resource block assignment information to a threshold number of resource blocks; and transmitting, by the terminal and using the selected channel quality indicator report transmission mode, a channel quality indicator report to the base station in response to the channel quality indicator trigger.

9. The method of claim 8, comprising: buffering data to be transmitted to the base station in response to reception of the control channel signals; and waiting for a signal from the base station before resuming data transmission.

10. The method of claim 8 wherein the plurality of channel quality indicator report transmission modes include an aperiodic channel quality indicator reporting mode, in which the transmitter, in operation, transmits an aperiodic channel quality indicator to the base station without multiplexing the aperiodic channel quality indicator with user data in an uplink transport block.

11. The method of claim 10 wherein the control channel signals indicate a redundancy/constellation version parameter of a user data retransmission and the aperiodic channel quality indicator reporting mode is selected in response to the redundancy/constellation version parameter being equal to a determined value.

12. The method of claim 11 wherein the determined value of the redundancy/constellation version parameter is 1.

13. The method of claim 8 wherein the plurality of channel quality indicator report transmission modes have a same indication of spectral efficiency.

14. The method of claim 8 wherein the plurality of channel quality indicator report transmission modes are associated with code rates that are equal to or larger than a threshold code rate.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) In the following, the invention is described in more detail in reference to the attached figures and drawings. Similar or corresponding details in the figures are marked with the same reference numerals.

(2) FIG. 1 shows an exemplary data transmission to users in an OFDMA system in localized mode (LM) having a distributed mapping of L1/L2 control signaling,

(3) FIG. 2 shows an exemplary data transmission to users in an OFDMA system in localized mode (LM) having a distributed mapping of L1/L2 control signaling,

(4) FIG. 3 shows an exemplary data transmission to users in an OFDMA system in distributed mode (DM) having a distributed mapping of L1/L2 control signaling,

(5) FIG. 4 exemplarily highlights the interrelation between transport block/protocol data unit and its different redundancy versions as well as the transport block size/protocol data unit size, and

(6) FIG. 5 shows a mobile communication system according to one embodiment of the invention, in which the ideas of the invention may be implemented.

DETAILED DESCRIPTION OF THE INVENTION

(7) The following paragraphs will describe various embodiments of the invention. For exemplary purposes only, most of the embodiments are outlined in relation to an (evolved) UMTS communication system according to the SAE/LTE discussed in the Technical Background section above. It should be noted that the invention may be advantageously used, for example, in connection with a mobile communication system such as the SAE/LTE communication system previously described or in connection with multi-carrier systems such as OFDM-based systems, but the invention is not limited to its use in this particular exemplary communication network. In particular, the invention can be implemented in any type of communication system comprising a base station and a terminal, not necessarily a mobile terminal. For instance, a desktop PC with a UMTS/LTE card may serve as a terminal. Alternatively, the terminal may be collocated within an access station (static) for the last mile transmission using other than UMTS/LTE system.

(8) Before discussing the various embodiments of the invention in further detail below, the following paragraphs will give a brief overview on the meaning of several terms frequently used herein and their interrelation and dependencies.

(9) In general, the transport format (TF) in 3GPP defines the modulation and coding scheme (MCS) and/or the transport block (TB) size, which is applied for the transmission of a transport block and is, therefore, required for appropriate (de)modulation and (de)coding. The L1/L2 control signaling may only need to indicate either the transport block size or the modulation and coding scheme. In case the modulation and coding scheme should be signaled, there are several options how to implement this signaling. For example, separate fields for modulation and coding or a joint field for signaling both, the modulation and coding parameters may be foreseen. In case the transport block size (TBS) should be signaled, the transport block size is typically not explicitly signaled, but is rather signaled as a TBS index. The interpretation of the TBS index to determine the actual transport block size may, for example, depend on the resource allocation size.

(10) In the following, the transport format field on the L1/L2 control signaling is assumed to be indicating either the modulation and coding scheme or the transport block size. It should be noted, that the transport block size for a given transport block typically does not change during transmissions. However, even if the transport block size is not changed, the modulation and coding scheme may change between transmissions, e.g., if the resource allocation size is changed (as apparent for the described relationship above).

(11) It should be also noted that in some embodiments of the invention, for retransmissions the transport block size is typically known from the initial transmission. Therefore, the transport format (MCS and/or TBS) information (even if the modulation and coding scheme changes between transmissions) does not have to be signaled in retransmissions, since the modulation and coding scheme can be determined from the transport block size and the resource allocation size, which can be determined from the resource allocation field.

(12) A redundancy version denotes a set of encoded bits generated from a given transport block, as shown in FIG. 4. In systems, where the code rate for the data transmission is generated by a fixed rate encoder and a rate matching unit (e.g., in HSDPA of UMTS or LTE systems), different redundancy versions are generated for a single transport block (or protocol data unit) by selecting different sets of available encoded bits, where the set size (number of selected bits) depends on the actual code rate (CR) for the data transmission. In case the actual code rate for a transmission (or retransmission) is higher than the encoder rate, a redundancy version is constructed out of a subset of encoded bits. In case the actual code rate for a transmission (or retransmission) is lower than the encoder rate, a redundancy version is typically constructed out of all encoded bits with selected bits being repeated. It should be noted that the figure is simplified for easier understanding. The actual content of the redundancy version may differ from the depicted case. For example, RV0 may contain only part of or all systematic bits as well as only part or all of parity bits. Likewise, RV1 and other RVs are not constrained to contain only non-systematic bits.

(13) It should be noted that for simplicity it is referred to transport format and redundancy version in most of the examples herein. However, in all embodiments of this invention the term “transport format” means either one of “transport format”, “transport block size”, “payload size” or “modulation and coding scheme”. Similarly, in all embodiments of this invention the term “redundancy version” can be replaced by “redundancy version and/or constellation version”.

(14) The present invention aims at providing a possibility for signaling a Channel Quality Indicator (CQI) reporting mode with impact as small as possible on the scalability of resource allocation and signaling of other control parameters. In particular, the CQI reporting mode relates to an aperiodic reporting of CQI that is not multiplexed with user data even if the buffer is not empty, which will be further referred to as “CQI-only mode”.

(15) From a certain perspective, a PMI is not fundamentally different from a CQI—the PMI suggests basically a precoding to use for good exploitation of the physical resource, and a CQI suggests basically an MCS or TBS as mentioned previously to the same end. Therefore, it should be obvious to those skilled in the art that any following description of the invention with respect to CQI can be easily adapted mutatis mutandis to be used for PMI, or combinations thereof or with other information.

(16) A main idea of the invention relies on using a predetermined transport format for signalizing the CQI-only reporting mode only in selected conditions. Accordingly, a control channel signal from a base station to a terminal is defined, which comprises the predetermined transport format.

(17) The control channel signal further comprises a CQI trigger signal for triggering a transmission of a CQI by the terminal. The interpretation of the selected transport format by the terminal depends on the status of one or more CQI trigger bits in the CQI trigger signal comprised in the control channel signal. In case the CQI trigger signal indicates to the terminal to transmit a CQI report and the value of transport format parameter corresponds to the predetermined value, the terminal interprets this combination as a command to transmit such CQI in the predetermined mode, i.e., here the CQI-only mode, to the base station. If, on the other hand, the value of transport format parameter does not correspond to the predetermined value, even if CQI trigger is set, the terminal will interpret the CQI trigger as well as the transport format parameter in their usual meaning. Those skilled in the art will recognize that this usual meaning may be a multiplexing of CQI with user data in an uplink transmission.

(18) The main advantage of the invention relies in that the overall structure and content of the MCS/TBS table is preserved for Uplink and Downlink. An MCS level is not spent completely for signalling the CQI reporting mode. Full flexibility for Downlink is retained and full flexibility for Uplink data-only transmission, i.e., without multiplexing CQI, is retained as well. Further, the invention allows to implement a CQI-only reporting mode without wasting a whole MCS level or any other unconditional value of any other parameter. This provides more flexibility for the Uplink scheduler, which results in better spectral efficiency.

(19) According to a preferred embodiment of the invention, the indicated predetermined mode for reporting the channel quality indicator is an aperiodic channel quality indicator reporting mode, wherein the aperiodic channel quality indicator is to be transmitted by the terminal to the base station without multiplexing with user data. This thus allows for signalling to the terminal to transmit a so-called “CQI-only” report to the base station.

(20) A preferred embodiment of the invention will be described in the following by referring to the MCS entries illustrated in the example of Table 6.

(21) Since the CQI report is present in uplink only, the MCS table entries 29-31 shown in Table 6 are used for signalling the redundancy version (RV) of a retransmission. Usually, without a grant for a retransmission, the ordered sequence of RV parameters for transmissions is established to achieve the best decoding performance using the least number of transmissions. For LTE/SAE, said ordered sequence has been established as RV={0, 2, 3, 1}, since the use of the RV parameters 2 and 3 before using the RV parameter 1 has a better performance. As a result, the RV parameter 1 is usually the least frequently used RV value, and consequently RV1 is the least frequently used redundancy version.

(22) Hence, according to a preferred embodiment of the invention, only the reception of a control channel signal signalling a predetermined RV value, preferentially the RV value 1, together with a CQI trigger signal and a predetermined MCS index (transport format parameter value), will be interpreted by the terminal as meaning that a CQI-only report shall be transmitted to the base station on PUSCH. In case a control channel signal signalling the RV parameter 1 is received by the terminal without a CQI trigger signal, the terminal interprets it as meaning that a transmission using the RV parameter 1 shall be performed.

(23) This is summarized in the following Table 7, where the predetermined transport format selected is the MCS entry 29:

(24) TABLE-US-00007 TABLE 7 MCS Index Interpretation 0-28 As before (MCS/TBS, . . .) 29 DL: Implicit TBS signaling with QPSK UL with CQI Trigger: CQI-only transmission (=no data) UL without CQI Trigger: Transmission using RV1 30 DL: Implicit TBS signaling with 16QAM UL: Transmission using RV2 31 DL: Implicit TBS signaling with 64QAM UL: Transmission using RV3

(25) The basic idea of the invention is further extensible by using other conditional parameter values additionally to the transport format (e.g., MCS index) and CQI trigger. This enables even higher efficiency of resource utilization.

(26) A further embodiment of the invention will now be described in the following.

(27) The control channel signal contains information on resource blocks used for the transmission from the terminal to the base station on the PUCCH. The transmission of the channel quality indicator CQI using the predetermined mode defined above is to be triggered by the terminal only in case the information on the resource blocks indicates a number of resource blocks that is smaller or equal to a predetermined resource block number.

(28) Indeed, the signalling of CQI-only mode is advantageous for small resource block assignments, since the coding rate for large resource block assignments CQI-only would become unnecessarily low. Hence, according to this embodiment of the invention, the terminal shall transmit a CQI without multiplexing with user data only for a small number of resource block assignments.

(29) An example will be presented in the following for illustration purposes by referring to Table 8. In this example, the RV parameter is selected to be 1 as illustrated above. Even though 10 resource blocks is chosen herewith, this is meant only for exemplary purposes and any other value could be chosen instead.

(30) TABLE-US-00008 TABLE 8 MCS Index Interpretation 0-28 As before (MCS/TBS, . . .) 29 DL: Implicit TBS signaling with QPSK UL CQI Trigger Set, <=10 RBs assigned: CQI-only transmission (=no data) UL CQI Trigger Set, >10 RBs assigned: Transmission using RV1, multiplexing of data and CQI UL without CQI Trigger: Transmission using RV1 30 DL: Implicit TBS signaling with 16QAM UL: Transmission using RV2 31 DL: Implicit TBS signaling with 64QAM UL: Transmission using RV3

(31) As apparent from Table 8, the transmission of a CQI-only is triggered by the terminal only when the CQI trigger signal is signalled and the RV is set to 1 (corresponding to MCS index value of 29) and if the number of assigned resource blocks is smaller than or equal to 10. In case the number of assigned resource blocks is larger than 10, even if the CQI trigger signal is signalled, the terminal will not transmit a CQI-only but will transmit the CQI report along with multiplexed data, using, for example, the redundancy version parameter having a value of 1.

(32) Furthermore, a UE experiencing good channel conditions, i.e., being assigned a large MCS, is likely to be allocated a lot of Resource Blocks, so that it is preferable to not lose flexibility for those cases by interpreting such a signal as meaning CQI-only. Consequently, it may be preferable to use the cases where a number of Resource Blocks are allocated to a terminal greater than a predetermined threshold Resource Block value and an MCS value that is representing a spectral efficiency below a predetermined MCS or spectral efficiency threshold value to signal a CQI-only transmission.

(33) An alternative embodiment of the invention will now be presented in the following by referring to Table 9, which, instead of using the predetermined RV parameter value, and preferentially the RV1 entry, proposes to use one of two transport formats, i.e., MCS indexes signalizing the modulation and coding combination, in the example of Table 9, that have an identical spectral efficiency.

(34) TABLE-US-00009 TABLE 9 Coding MCS Index Modulation rate × 1024 Efficiency 0 2 120 0.2344 1 2 157 0.3057 2 2 193 0.377 3 2 251 0.4893 4 2 308 0.6016 5 2 379 0.7393 6 2 449 0.877 7 2 526 1.0264 8 2 602 1.1758 9 (DL) 2 679 1.3262 9 (UL without 2 679 1.3262 CQI trigger) 9 (UL with CQI-only transmission (=no data) CQI trigger) 10 4 340 1.3262 11 4 378 1.4766 12 4 434 1.69535 13 4 490 1.9141 14 4 553 2.1602 15 4 616 2.4063 16 4 658 2.5684 17 6 438 2.5684 18 6 466 2.7305 19 6 517 3.0264 20 6 567 3.3223 21 6 616 3.6123 22 6 666 3.9023 23 6 719 4.21285 24 6 772 4.5234 25 6 822 4.8193 26 6 873 5.1152 27 6 910 5.33495 28 6 948 5.5547 29 DL: Implicit TBS signaling with QPSK UL: Transmission using RV1 30 DL: Implicit TBS signaling with 16QAM UL: Transmission using RV2 31 DL: Implicit TBS signaling with 64QAM UL: Transmission using RV3

(35) As apparent from Table 9, the MCS entries 9 and 10 have an identical spectral efficiency of 1.3262. Further, the MCS entries 16 and 17 each have the same spectral efficiency of 2.5684. Such overlapping entries (in terms of spectral efficiency) are foreseen, since a higher modulation scheme is more beneficial in a frequency-selective environment (see 3GPP RAN1 meeting 49bis R1-073105, “Downlink Link Adaptation and Related Control Signalling” for more details).

(36) The transmission of an independent CQI report without multiplexed data is more advantageous for small resource block assignments, where the channel is rather flat. Hence, an MCS entry representing a higher-order modulation scheme with the same spectral efficiency as an MCS entry representing a lower spectral efficiency should be replaced. For example, with respect to Table 6, the respective “upper” MCS entry, i.e., 10 or 17, should be replaced.

(37) The transmission of a CQI report with multiplexed data costs Uplink data redundancy. In order to multiplex data and CQI, some redundancy that is added for the data part by means of forward error correction coding has to be taken out to make room for the CQI. Obviously, the more redundancy is added, the easier and less notable is it to take out a few bits for the to-be-multiplexed CQI. The “upper” entries have more redundancy to offer than the “lower”, so it is less likely that a “lower” entry can support multiplexing a CQI report with data efficiently. In extreme cases, the added redundancy for the data could be smaller than what is necessary for a CQI. In such a case, multiplexing CQI could raise the resulting coding rate for the data above 1, since it is not sufficient to remove added redundancy, but systematic information has to be removed. This would result in an automatic transmission failure for the data, since the receiver cannot reconstruct the whole data from the received information. Therefore, an MCS entry that offers more redundancy than another MCS entry is preferably replaced to be used for a CQI-only transmission. Consequently, in relation to Table 6 the “lower” MCS entries 9 or 16 can be advantageously replaced and used for the transmission of a CQI report without multiplexed data.

(38) Furthermore, the embodiment described with respect to Table 8 can be applied and used in combination with the embodiment described with respect to Table 9.

(39) In general, any MCS index value may be used in combination with a CQI trigger to signal the CQI-only reporting mode. As another example, it may be beneficial to replace an MCS entry associated with a very small spectral efficiency, such as MCS Index 0 in Table 6, in conjunction with a set CQI trigger signal to trigger a CQI-only report. In such a case, since a very small spectral efficiency is replaced, the loss for the system in terms of how much data is not transmitted, since there is no data to be multiplexed with the CQI, is negligible.

(40) Another alternative embodiment of the invention will now be presented in the following by referring to Table 10, which, instead of using the predetermined RV parameter, and preferentially the RV1 entry, proposes to select a predetermined transport format that is associated with a high code rate.

(41) TABLE-US-00010 TABLE 10 MCS Coding Index Modulation rate × 1024 Efficiency 0 2 120 0.2344 1 2 157 0.3057 2 2 193 0.377 3 2 251 0.4893 4 2 308 0.6016 5 2 379 0.7393 6 2 449 0.877 7 2 526 1.0264 8 2 602 1.1758 9 2 679 1.3262 10 4 340 1.3262 11 4 378 1.4766 12 4 434 1.69535 13 4 490 1.9141 14 4 553 2.1602 15 4 616 2.4063 16 4 658 2.5684 17 6 438 2.5684 18 6 466 2.7305 19 6 517 3.0264 20 6 567 3.3223 21 6 616 3.6123 22 6 666 3.9023 23 6 719 4.21285 24 6 772 4.5234 25 6 822 4.8193 26 6 873 5.1152 27 6 910 5.33495 28 (DL) 6 948 5.5547 28 (UL without 6 948 5.5547 CQI trigger) 28 (UL with CQI-only transmission (=no data) CQI trigger) 29 DL: Implicit TBS signaling with QPSK UL: Transmission using RV1 30 DL: Implicit TBS signaling with 16QAM UL: Transmission using RV2 31 DL: Implicit TBS signaling with 64QAM UL: Transmission using RV3

(42) Instead of using the predetermined RV parameter, and preferentially the RV1 entry, as described in the embodiment above, an MCS entry associated with a high code rate is used, according to the present embodiment, for reporting a CQI report only. As apparent from Table 10, the selected MCS entry 28 is associated with a code rate that is equal to or larger than a predetermined code rate.

(43) Indeed, multiplexed CQI costs Uplink data redundancy. Since an MCS entry that offers a high code rate provides very little redundancy, multiplexing a CQI report with data at such a high code rate is relatively expensive, as already mentioned herein before. Consequently, according to this embodiment of the invention, an MCS entry associated with a high code rate such as the MCS entry 28 in Table 6 can be advantageously replaced and used for transmitting a CQI report only without multiplexing with data.

(44) Furthermore, the embodiment described with respect to Table 8 can be applied and used in combination with the embodiment described with respect to Table 10.

(45) In accordance with the present invention, also another parameter can be additionally set to signal the desired CQI reporting mode, preferentially the signalling of an independent CQI report. Examples of other possible parameters could be, among others, an antenna parameter (MIMO), a HARQ process number, a Constellation Number of a Modulation or another parameter.

(46) In another embodiment, a CQI-only report may be signalled by using multiple signals, e.g., in time or frequency domain. For example, setting the CQI trigger in two consecutive sub-frames could trigger a CQI-only report. As another example, assigning an MCS entry assigned with a low spectral efficiency to a terminal in consecutive sub-frames can be used to trigger a CQI-only report.

(47) In another embodiment, the MCS entry replaced to trigger a CQI-only report in conjunction with a set CQI trigger signal is selected depending on different terminal capability classes. Generally, a communication system supports different classes of terminal capabilities. For example, some terminals may not support the transmission of 64-QAM in the uplink. Consequently, for such terminals any MCS associated with a modulation scheme of 64-QAM is usually meaningless. Therefore, for such terminals a set CQI trigger signal in conjunction with an MCS entry which is not within the scope of the terminal's capability can be used to trigger a CQI-only report. Terminals that support the full scope are preferably employing any of the other embodiments described herein.

(48) In the previous embodiments, the term “predetermined” is used to describe e.g., a value with a special meaning that is known to both sides of a communication link. This can be a fixed value in a specification, or a value that is negotiated between both ends e.g., by other control signalling.

(49) In the following, the amendments to the Hybrid Automatic Repeat reQuest (HARQ) operation induced by the definition of the control channel signalling according to the invention will be presented.

(50) Since the triggering of a CQI-only report prevents the PUSCH from being used for data transmission in the usual way, the HARQ operation is influenced as well. First, the principles governing HARQ operation in uplink will be summarized. Then, an amended HARQ protocol operation according to the invention will be described.

(51) A Physical HARQ Indicator CHannel (PHICH) carrying ACK/NACK messages for an Uplink data transmission may be transmitted at the same time as a Physical Downlink Command CHannel PDCCH for the same terminal. With such simultaneous transmission, the terminal follows what the PDCCH asks the terminal to do, i.e., performs a transmission or a retransmission (referred to as adaptive retransmission), regardless of the PHICH content. When no PDCCH for the terminal is detected, the PHICH content dictates the HARQ behaviour of the terminal, which is summarized in the following.

(52) NACK: the terminal performs a non-adaptive retransmission, i.e., a retransmission on the same uplink resource as previously used by the same process.

(53) ACK: the terminal does not perform any Uplink (re)transmission and keeps the data in the HARQ buffer for that HARQ process. A further transmission for that HARQ process needs to be explicitly scheduled by a subsequent grant by PDCCH. Until the reception of such grant, the terminal is in a “Suspension state.”

(54) This is illustrated in the following Table 11:

(55) TABLE-US-00011 TABLE 11 HARQ feedback seen by the PDCCH seen UE (PHICH) by the UE UE behaviour ACK or NACK New New transmission according to Transmission PDCCH ACK or NACK Retransmission Retransmission according to PDCCH (adaptive retransmission) ACK None No (re)transmission, keep data in HARQ buffer and a PDDCH is required to resume retransmissions NACK None Non-adaptive retransmission

(56) The Uplink HARQ protocol behaviour corresponding to the reception of a PDCCH requesting a “CQI-Only” amended according to the invention will now be described.

(57) Upon reception of a control channel signal requesting the transmission of an independent CQI report, the terminal considers the received CQI-only carrying PDCCH as an ACK and goes into “suspension state.” The terminal does not perform any Uplink (re)transmission from the MAC point of view and keeps the data in the HARQ buffer, if any data is pending for retransmission. A PDCCH at the next occurrence of the HARQ process is then required to perform a retransmission or initial transmission, i.e., a non-adaptive retransmission cannot follow. In this way, the behaviour of a CQI-only on the PDCCH is treated by the UE in the same way as an ACK on the PHICH without a PDCCH.

(58) The amended HARQ protocol operation at the terminal is summarized in the following Table 12:

(59) TABLE-US-00012 TABLE 12 HARQ feedback seen by the PDCCH seen UE (PHICH) by the UE UE behaviour ACK or NACK New New transmission according to Transmission PDCCH ACK or NACK Retransmission Retransmission according to PDCCH (adaptive retransmission) ACK None No (re)transmission, keep data in HARQ buffer and a PDDCH is required to resume retransmissions NACK None Non-adaptive retransmission ACK or NACK “CQI-Only” No (re)transmission, keep data in HARQ buffer and a PDDCH is required to resume retransmissions

(60) Next, the operation of the transmitter of the control channel signal according to one of the various embodiments described herein and the receiver thereof will be described in further detail, thereby exemplarily relating to the case of downlink data transmission. For exemplary purposes a mobile network as exemplified in FIG. 5 may be assumed. The mobile communication system of FIG. 5 is considered to have a “two node architecture” consisting of at least one Access and Core Gateway (ACGW) and Node Bs. The ACGW may handle core network functions, such as routing calls and data connections to external networks, and it may also implement some RAN (Radio Access Network) functions. Thus, the ACGW may be considered as to combine functions performed by GGSN (Gateway GPRS Support Node) and SGSN (Serving GPRS Support Node) in today's 3 G networks and RAN functions as, for example, radio resource control (RRC), header compression, ciphering/integrity protection.

(61) The base stations (also referred to as Node Bs or enhanced Node Bs=eNode Bs) may handle functions as, for example, segmentation/concatenation, scheduling and allocation of resources, multiplexing and physical layer functions, but also RRC functions, such as outer ARQ. For exemplary purposes only, the eNodeBs are illustrated to control only one radio cell. Obviously, using beam-forming antennae and/or other techniques the eNodeBs may also control several radio cells or logical radio cells.

(62) In this exemplary network architecture, a shared data channel may be used for communication of user data (in form or protocol data units) on uplink and/or downlink on the air interface between mobile stations (UEs) and base stations (eNodeBs). This shared channel may be, for example, a Physical Uplink or Downlink Shared CHannel (PUSCH or PDSCH) as know in LTE systems. However, it is also possible that the shared data channel and the associated control channels are mapped to the physical layer resources as shown in FIG. 2 or FIG. 3.

(63) The control channel signals/information may be transmitted on separate (physical) control channels that are mapped into the same subframe to which the associated user data (protocol data units) are mapped or may be alternatively sent in a subframe preceding the one containing the associated information. In one example, the mobile communication system is a 3GPP LTE system, and the control channel signal is L1/L2 control channel information (e.g., information on the Physical Downlink Control CHannel—PDCCH). Respective L1/L2 control channel information for the different users (or groups of users) may be mapped into a specific part of the shared uplink or downlink channel, as exemplarily shown in FIGS. 2 and 3, where the control channel information of the different users is mapped to the first part of a downlink subframe (“control”).

(64) Another embodiment of the invention relates to the implementation of the above described various embodiments using hardware and software. It is recognized that the various embodiments of the invention may be implemented or performed using computing devices (processors). A computing device or processor may, for example, be general purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, etc. The various embodiments of the invention may also be performed or embodied by a combination of these devices.

(65) Further, the various embodiments of the invention may also be implemented by means of software modules, which are executed by a processor or directly in hardware. Also a combination of software modules and a hardware implementation may be possible. The software modules may be stored on any kind of computer readable storage media, for example, RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.

(66) Furthermore, it should be noted that the terms terminal, mobile terminal, MS and mobile station are used as synonyms herein. A user equipment (UE) may be considered one example for a mobile station and refers to a mobile terminal for use in 3GPP-based networks, such as LTE. Moreover, the terminal is not limited to a mobile station, it can be, e.g., a PC card or a fixed access point of another system.

(67) In the previous paragraphs various embodiments of the invention and variations thereof have been described. It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described.

(68) It should be further noted that most of the embodiments have been outlined in relation to a 3GPP-based communication system and the terminology used in the previous sections mainly relates to the 3GPP terminology. However, the terminology and the description of the various embodiments with respect to 3GPP-based architectures is not intended to limit the principles and ideas of the inventions to such systems.

(69) Also the detailed explanations given in the Technical Background section above are intended to better understand the mostly 3GPP specific exemplary embodiments described herein and should not be understood as limiting the invention to the described specific implementations of processes and functions in the mobile communication network. Nevertheless, the improvements proposed herein may be readily applied in the architectures described in the Technical Background section. Furthermore, the concept of the invention may be also readily used in the LTE RAN currently discussed by the 3GPP.