In the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) system, transmission on a Physical Uplink Shared Channel (PUSCH) of a User Equipment (UE) is controlled by means of centralized scheduling of the base station.
Uplink scheduling information of the PUSCH is sent to a target UE from the base station through a Physical Downlink Control Channel (PDCCH). The uplink scheduling information comprises control information, such as resource allocation related to the channel, modulation and coding solution, and cyclic shift for a Demodulation Reference Signal (DMRS for short).
The PDCCH is used for bearing uplink and downlink scheduling information as well as uplink power control information. Downlink Control Information (DCI) has the following several formats:
DCI format 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 3, 3A, and so on.
DCI format 0 is used for indicating scheduling of a Physical Uplink Shared Channel (PUSCH for short);
DCI format 1, 1A, 1B, 1C and 1D are used for different transmission modes of a Physical Downlink Shared Channel (PDSCH for short) of a single Transport Block (TB);
DCI format 2 and 2A are used for different transmission modes in space division multiplexing; and
DCI format 3 and 3A are used for transmission of power control instructions on a Physical Uplink Control Channel (PUCCH) and the PUSCH.
An LTE-Advanced system (LTE-A system for short) is the next generation evolution system of the LTE system. In technologies related to the LTE, uplink scheduling DCI format 0 does not support uplink multi-antenna transmission, in the scenario of LTE-A uplink multi-antenna transmission, in order to enhance the function of signaling indication, it is required to add a new format which is called as DCI format X into the uplink scheduling DCI, or to extend the length of the signaling based on the existing signaling type of DCI format 0.
In the LTE system, DCI format 0 comprises the following specific information:                Flag for distinguishing the DCI format 0 and the DCI format 1A;        Frequency hopping flag;        Resource block assignment and frequency hopping resource assignment;        Modulation and Coding Scheme (MCS) and Redundancy Version (RV);        New Data Indicator (NDI);        Transmission Power Control (TPC) command for the scheduled PUSCH;        Cyclic shift for the Demodulated Reference Signal (DM RS);        Uplink (UL) index, only existing in a Time Division Duplex (TDD) system, and used when uplink-downlink configuration is 0;        Downlink Assignment Index (DAD, only existing in the TDD system, and used when the uplink-downlink configuration is 1 to 6;        Channel Status Indication (CQI) request.        
The DCI format 0 indicates the cyclic shift for the demodulation reference signal of the scheduled PUSCH, as shown in Table 1.
TABLE 1Cyclic shift field in DCI format 0n(2)DMRS000000160103011410021018110101119
In the LTE-A system, a single antenna port transmission or a multi-antenna port transmission can be used for the PUSCH. FIG. 1 shows a schematic diagram for processing a transmitting end baseband signal of a physical uplink shared channel in an existing LTE-A employing multi-antenna port transmission.
In FIG. 1, when the multi-antenna port transmission is performed, the LTE-A system supports one or two codewords (CW) based spatial multiplexing, each codeword corresponds to one Transport Block (TB), or the correspondence relation between the transport block and the codeword can be changed according to the transport block to codeword swap flag. Therefore, the LTE-A system supports transmission mode with a single transport block or double transport blocks.
Codewords are further mapped to layers, and each codeword is mapped into data in one or two layers. FIG. 2 shows a schematic diagram illustrating a method of mapping a codeword to a layer. Functions of a codeword-to-layer mapping module are illustrated below simply by taking two codewords and four transmitting antennas as example. When two codewords are mapped to two layers, a codeword 0 is directly mapped to the first layer and a codeword 1 is directly mapped to the second layer; when two codewords are mapped to three layers, the codeword 0 is directly mapped to the first layer, the codeword 1 is mapped to the second layer and the third layer after serial/parallel conversion; when two codewords are mapped to four layers, the codeword 0 is mapped to the first layer and the second layer after serial-parallel conversion, and the codeword 1 is mapped to the third layer and the fourth layer after serial-parallel conversion.
Before precoding, data in each layer can be processed independently or in parallel, or data in multiple spatially-multiplexed layers can be shifted on one modulation symbol or one DFT-S-OFDM symbol or one slot by adopting the Layer Shifting (LS) technology. FIG. 3 shows a schematic diagram illustrating the effect before and after layer shifting. As shown in FIG. 3, a layer shifting module is an optional configuration at the transmitting end, that is, this module can be turned off under some conditions, that is to say, the layer shifting is not enabled.
When two-codeword spatial multiplexing is employed and the layer shifting is not enabled, independent rate control, channel coding and modulation are performed on the two codewords, and the two codewords are allocated with independent Hybrid Automatic Repeat-reQuest (HARQ) process; when two-codeword spatial multiplexing is employed and the layer shifting is used, spatial bundling is performed on the two codewords, the two codewords have the same modulation and coding scheme and are allocated with one hybrid automatic repeat-request process.
The LTE-A system employs a codebook-based linear precoding technology, the precoding technology is a technology in which preprocessing is performed on the signal at the transmitting end by utilizing Channel Status Information (CSI) to improve the performance of the multi-antenna system. One way to obtain the CSI at the transmitting end is to obtain the feedback from the receiving end. In order to reduce the feedback overhead, the general way is to store identical codebooks, namely, precoding matrix sets, at the receiving end and the transmitting end. The receiving end selects a proper precoding matrix from the codebook according to the current channel situation and feeds a Precoding Matrix Index (PMI) in the precoding matrix set back to the transmitting end, while the transmitting end finds out the precoding matrix according to the fed precoding matrix index and performs precoding on sent signals. The mathematical model for data precoding is y=HWs+n, where y is a vector of a received signal, H is a channel coefficient matrix, W is a precoding matrix, s is a signal vector, and n is a noise vector.
In the LTE-A system, when the physical uplink shared channel employs multi-antenna port transmission, precoding is performed on data in each layer and a Demodulation Reference Signal (DM RS) thereof in the same way. While for the demodulation reference signals of data in different layers, including the demodulation reference signals of data in multiple layers at the same user equipment in a Single User Multi-Input Multi-Output (SU-MIMO) system and the demodulation reference signals of data in multiple layers at multiple user equipments in a Multi-User Multi-Input Multi-Output (MU-MIMO) system, different Cyclic Shifts (CSs) for demodulation reference signals and/or Orthogonal Cover Codes (OCCs) are used for orthogonalization to distinguish data in different spatially-multiplexed layers or to distinguish different users, therefore, cyclic shifts and orthogonal cover codes (n(2)DMRS, nocc) can be used to represent orthogonal resources. Wherein orthogonal cover codes (OCCs) are [+1, +1] and [+1, −1], acting on the demodulation reference signals in two slots within one subframe. Each subframe of the PUSCH comprises two slots, and each slot consists of six data symbols and one demodulation reference signal, as shown in FIG. 4.
The uplink scheduling information of the PUSCH in the LTE system comprises control information, such as the resource allocation related to the channel, the modulation and coding solution, and the cyclic shift for the Demodulation Reference Signal (DMRS). However, at present, there is no signaling indication information for the OCC. In the LTE-A system, how to reasonably design a signaling to indicate the OCC, or how to use a signaling to indicate both the CS and OCC is a problem to be solved.
USPTO Backgrounds
USPTO Backgrounds