The physical uplink channels of the long term evolution (LTE for short) system include a physical random access channel (PRACH for short), a physical uplink shared channel (PUSCH for short) and a physical uplink control channel (PUCCH for short). Wherein, the PUSCH has two different cyclic prefix (CP for short) lengths which are respectively a normal cyclic prefix (Normal CP for short) and an extended cyclic prefix (Extended CP for short). Each sending subframe of the PUSCH is composed of two time slots. For different cyclic prefix lengths, the location of the demodulation reference signal (DMRS for short) in the subframe will be different. FIG. 1 is a schematic diagram of a time domain location of a demodulation reference signal according to the related art. As shown in FIG. 1, each subframe contains two DMRS symbols. FIG. 1 (a) is a schematic diagram of the time domain location of the DMRS when adopting the normal cyclic prefix, each subframe contains 14 orthogonal frequency division multiplexing (OFDM for short) symbols, and the 14 OFDM symbols include the DMRS symbols, wherein, the OFDM symbols represent the time domain location of one subframe; FIG. 1 (b) is a schematic diagram of the time domain location of the DMRS when adopting the extended cyclic prefix, and each subframe contains the OFDM symbols of 12 time domains.
In the LTE system, a physical downlink control channel (PDCCH for short) is used to bear the uplink and downlink scheduled information, and the uplink power control information. A base station (e-Node-B, eNB for short) can configure the user equipment (UE for short) through the downlink control information, or the user equipment accepts the configuration from the higher layers, which is also called as configuring the UE through the high layers signaling. The format of the downlink control information (DCI for short) includes DCI format 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 3 and 3A, etc., wherein,
the DCI format 0 is used to indicate scheduling of the PUSCH;
the 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;
the DCI format 2 and 2A are used for different transmission modes of space division multiplexing of the downlink PDSCH;
the DCI format 3 and 3A are used for transmission of power control instructions of the PUCCH and the PUSCH.
The transport block size of the above-mentioned DCI format 0, 1A, 3 and 3A are same, wherein, the DCI format 0 and 1A adopts 1 bit to distinguish the format.
The format of the DCI format 3 is as follows:                transmission power control command 1, transmission power control command 2, . . . , transmission power control command N,        
wherein,
      N    =          ⌊                        L                      format            ⁢                                                  ⁢            0                          2            ⌋        ,Lformat 0=format 0 plus a bit number before the cyclical redundancy check (CRC for short) (including additional padding bit(s)), and the parameter tpc-Index given by the high layers determines the transmission power control command (TPC command) of the given UE.
If
            ⌊                        L                      format            ⁢                                                  ⁢            0                          2            ⌋        <                  L                  format          ⁢                                          ⁢          0                    2        ,the DCI format 3 will be added 1 bit ‘0’.
The process of a blind detection of the PDCCH in the LTE system is described as follows briefly, the control channel element (CCE for short) is a minimum element bearing the PDCCH resource, and the control area is composed of a series of CCEs.
The blind detection range of the PDCCH is defined by a search space, and the search space is divided into a public search space and an UE dedicated search space. The search space Sk(L) is defined as:L·{(Yk+m)mod └NCCE,k/L┘}+i, 
wherein, L is the aggregation grade of the CCE, and Lε{1, 2, 4, 8}; for the public search space, Yk=0, i.e., searching from CCE=0˜15; and for the UE dedicated search space, Yk=(A·Yk-1)mod D, Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, ns represents the time slot number 0˜19. i=0,L, L−1, m=0,L, M(L)−1, M(L) is the number of PDCCH candidates after L is given in the search space.
Wherein, the nRNTI represents the radio network temporary identifier (RNTI for short), and nRNTI corresponds to one of the following radio network temporary identifiers:
system information-RNTI (SI-RNTI for short),
random access-RNTI (RA-RNTI for short),
paging-RNTI (P-RNTI for short),
cell-RNTI (C-RNTI for short),
semi-persistent scheduling RNTI (SPS-RNTI for short), and
temporary cell-RNTI (Temporary C-RNTI).
Which kind of RNTI the nRNTI selects specifically is configured by the high layers signaling, and the specific value is also specified by the corresponding signaling and data. The value of the RNTI refers to the following Table 1. The search space defined according to the aggregation grade is shown in Table 2. When the UE is blind detected, the detection is performed according to the DCI format corresponding to the transmission mode of the downlink. The 16-bit CRC of each downlink control information DCI is scrambled by using the above-mentioned RNTI. Different UEs can configure different RNTIs to perform the scrambling to the CRC, thus it can distinguish the DCI of different UEs.
TABLE 1RNTI valueValue (Hex)Frequency DivisionTime DivisionDuplexing (FDD)Duplexing (TDD)RNTI0000-00090000-003BRadom access RNTI (RA-RNTI)000A-FFF2003C-FFF2C-RNTI, Semi-PersistentScheduling C-RNTI, TemporaryC-RNTI, TPC-PUCCH-RNTIand TPC-PUSCH-RNTIFFF3-FFFCReservedFFFEP-RNTIFFFFSI-RNTI
TABLE 2the PDCCH candidates monitored by UESearch space Sk(L)The number ofAggregationPDCCH candidatesTypegrade LSize [CCEs]M(L)UE166dedicated21264828162Public41648162
In the LTE system, the multiplexing process of the DCI is shown in FIG. 2. Every DCI corresponds to one medium access control identifier (MAC id), i.e., corresponds to one RNTI. The original information bit of the DCI is added with the CRC scrambled by the RNTI, and then performed channel coding and rate matching, thus a plurality of DCIs of the PDCCH are multiplexed together. System information (SI for short) performs the resource allocation through the DCI format 1A/1C. The blind detection of the SI is only performed in the public search space, and the CRC of the DCI of the SI is scrambled by adopting the unique SI-RNTI.
The broadcast information of the LTE system is divided into a master information block (MIB for short) and a system information block (SIB for short), wherein, the MIB is transmitted on the physical broadcast channel (PBCH for short), and the SIB is transmitted on the PDSCH (also called scheduled information (SI)).
The SRS is a signal used for measuring radio channel state information (CSI for short) between the user equipment and the base station. In the long term evolution system, the UE sends an uplink SRS in the last data symbol of the sent subframe regularly according to parameters, such as the bandwidth, the frequency domain location, the sequence cyclic shift, the period and the subframe offset, etc., instructed by the eNB. The eNB judges the UE uplink CSI according to the received SRS, and performs operations, such as frequency domain selection scheduling and closed-loop power control, etc., according to the obtained CSI.
In the LTE system, an SRS sequence sent by the UE is obtained by performing the cyclic shift α in time domain to one root sequence ru,v(n). Different SRS sequences can be obtained by performing different cyclic shifts α to the same root sequence, and these obtained SRS sequences are mutual orthogonal. Therefore, these SRS sequences can be allocated to different UEs for using, to realize the code division multiple access among the UEs. In the LTE system, the SRS sequence defines 8 cyclic shifts α, which is provided through the following formula (1):
                    α        =                  2          ⁢          π          ⁢                                          ⁢                                    n              SRS              cs                        8                                              Formula        ⁢                                  ⁢                  (          1          )                    
wherein, nSRScs is indicated by signaling of 3-bit, as 0, 1, 2, 3, 4, 5, 6 and 7 respectively. That is to say, with the same time-frequency resource, the UE in the cell has 8 available code resources, and the eNB can configure at most 8 UEs to send the SRS at the same time on the same time-frequency resource. Formula (1) can be regarded as dividing the SRS sequence into 8 pieces with same interval in the time domain, however, since the length of the SRS sequence is a multiple of 12, so the minimum length of the SRS sequence is 24.
In the LTE system, the frequency domain bandwidth of the SRS adopts a tree structure to configure. Every SRS bandwidth configuration corresponds to one tree structure, and the SRS-Bandwidth on the highest layer (or called the first layer) corresponds to the maximum SRS bandwidth of the SRS bandwidth configuration, or is called as the SRS bandwidth range. The UE calculates and obtains its own SRS bandwidth according to the signaling indication of the base station, and then determines a frequency domain initial position for sending the SRS by itself according to an upper layer signaling frequency domain location nRRC sent by the eNB. FIG. 3 is a schematic diagram of a frequency domain initial position of a UE allocated with different nRRC sending the SRS in the related art. As shown in FIG. 3, the UE allocated with different nRRC will send the SRS in different areas of the SRS bandwidth of the cell, wherein, the UE1 determines the frequency initial position to send the SRS according to nRRC=0, the UE2 determines the frequency initial position to send the SRS according to nRRC=3, the UE3 determines the frequency initial position to send the SRS according to nRRC=4, and the UE4 determines the frequency initial position to send the SRS according to nRRC=6.
The sequence used by the SRS is selected from a demodulation pilot frequency sequence group. When the SRS bandwidth of the UE is 4 resource blocks (RB for short), it uses a computer generated (CG for short) sequence with the length being 2 RBs; and when the SRS bandwidth of the UE is larger than 4 RBs, it uses a Zadoff-Chu sequence with the corresponding length.
In addition, in the same SRS bandwidth, the sub-carrier of the SRS is placed with intervals, that is to say, sending of the SRS adopts a comb structure. The number of the frequency comb in the LTE system is 2, which also corresponds to the repetition factor (RPF for short) of the time domain of 2. FIG. 4 is a schematic diagram of a comb structure of the SRS in the related art. As shown in FIG. 4, when each UE sends the SRS, only one of the two frequency combs is used, comb=0 or comb=1. In this way, the UE, according to the location indication of the frequency comb (comb=0 or comb=1) of 1-bit upper layer signaling, only uses the sub-carrier with frequency domain index being the even number or odd number to send the SRS. This comb structure allows more UEs to send the SRS in the same SRS bandwidth.
In the same SRS bandwidth, a plurality of UEs can use different cyclic shifts in the same frequency comb, and then sends the SRS through the code division multiplexing; and also two UEs send the SRS in different frequency combs through the frequency division multiplexing. For example, in the LTE system, for the UE sending the SRS in a certain SRS bandwidth (4 RBs), cyclic shifts able to be used by the UE are 8 and frequency combs able to be used by the UE are 2, thus the UE has 16 resources that can be used for sending the SRS, that is to say, in that SRS bandwidth, at most 16 SRSs can be sent at the same time. Since the LTE system does not support single user multiple input multiple output (SU-MIMO for short), the UE can only have one antenna to send the SRS at every moment; so one UE only needs one SRS resource. Therefore, in the above-mentioned SRS bandwidth, the system at most can multiplex 16 UEs at the same time.
The LTE-Advanced (LTE-A for short) system is the next generation evolved system of the LTE system, supports the SU-MIMO in the uplink, and can use at most 4 antennas as uplink transmitting antennas. That is to say, the UE can simultaneously send the SRS on a plurality of antennas at the same moment, while the eNB needs to estimate the state on each channel according to the SRS received on each antenna.
In the case of the LTE-A carrier aggregation, a variety of carrier types are introduced. The LTE-A carrier types can be divided into three types: backwards compatible carrier, non-backwards compatible carrier and extension carrier.
The extension carrier has two kinds of meanings: 1) as a part of component carrier (CC for short); 2) as an independent component carrier. The extension carrier cannot work alone, and must be a part of a group of component carrier set; and at least one of the component carriers in the set can work alone. The extension carrier is invisible for the LTE UEs.
In order to design simply, and considering various possible application scenarios, the extension carrier is most likely configured to have no PDCCH. Then the DCI corresponding to the system information of the extension carrier needs to be sent on other component carriers. Besides, the LTE-A has also introduced the concept of resident carrier, that is, the carrier accessed by the UE initially, and after the access succeeds, it can reconfigure the resident carrier for the UE through the high layers signaling, to guarantee load balancing.
In the case of the LTE-A carrier aggregation, a PDCCH component carrier set (PDCCH CC set) is defined, and the UE needs to perform the blind detection in the PDCCH CC set; a downlink component carrier set (DL CC set for short) is defined also, and the PDSCH of the UE can be sent on any CC in the DL CC set. In the case of the LTE-A carrier aggregation, cross carrier scheduling is allowed, that is, the PDCCH on a certain component carrier can schedule the PDSCH or the PUSCH on a plurality of component carriers.
It is proposed in the existing research of the LTE-A that: in the uplink communication, the non-precoding (i.e., antenna-dedicated) SRS should be used, while the precoding is performed to the DMRS of the PUSCH. The base station, by receiving the non-precoding SRS, can estimate the uplink original CSI, but the base station cannot estimate the uplink original CSI through the precoding DMRS. At the moment, when the UE uses multi-antenna to send the non-precoding SRS, the SRS resource required by each UE will increase, which causes the number of the UEs which can be multiplexed in the system at the same time to decrease. In addition, except keeping the original periodic of the LTE to send SRS, in order to improve the utilization rate of the SRS resource and enhance the flexibility of resource scheduling, the UE aperiodically sending the SRS can also be configured through the downlink control information or the high layers signaling. Therefore, there are the periodic SRS and the aperiodic SRS in the LTE-A system, and how to reasonably design the downlink control information or the high layers signaling to configure the SRS resource, to realize aperiodically sending the SRS effectively and timely, save the signaling overhead and reduce the complexity of the UE blind detection at the same time, is a problem to be solved.