DMRS Design and Channel Estimation for LTE-Advanced MIMO Uplink

A novel type II relay-assisted retransmission scheme for uplink of LTE-advanced system

“…For control information detection, the eNodeB estimates H MB (k) from (16) by filtering out the reference signal of the relay in the time domain, e.g., using the method in [16], and then uses the estimated channel for control information detection according to (18).…”

“…It is noted that there is no need to inform eNodeB about whether the relay conducts retransmission or not. eNodeB can always use the same channel estimation algorithm (e.g., algorithm in [16]) to estimate the channel response for control information detection, i.e., eNodeB performs filtering to location of reference signal of relay in time domain even if relay does not perform the retransmission. Therefore, regardless the relay conducts retransmission or not, eNodeB can always get correct channel estimation for control information detection and the proposed method does not introduce any additional signaling overhead.…”

“…From (28) and (30), eNodeB can perform channel estimation to obtain the superposed equivalent channel of data transmission of the UE m, e.g., using the method in [16]. After obtaining the equivalent channels (in total N × M) of all UEs, eNodeB can construct an equivalent MIMO channel matrix and perform MIMO detection to detect the data packets of M UEs.…”

“…To be more specific, if eNodeB performs fast Fourier transform to the overlapped reference signals, the two channel responses, i.e., UE-to-eNodeB channel and relay-to-eNodeB channel, will have different locations in time domain due to the different cyclic shifts. Therefore, eNodeB can filter out the reference signal of relay in time domain (e.g., using the method in [16]) and thus can have an accurate estimation of the UE-to-eNodeB channel. Because the actual channel of the control information transmission is the UE-to-eNodeB channel, eNodeB can conduct detection of the control information with the estimated channel.…”

Demodulation Reference Signal Design and Channel Estimation for LTE-Advanced Uplink

“…Therefore, the estimation accuracy of traditional DFT-based channel estimation will deteriorate significantly in practice. In order to mitigate the aforementioned problems, an improved DFT-based channel estimation was proposed for LTE(-A) uplink (Hou et al, 2009), which is illustrated in Fig. 5 for each receive antenna of eNB.…”