Channel Training Algorithms for Two-Way MIMO Relay Systems

Abstract

Two-way relay systems are known to be capable of providing higher spectral efficiency compared with conventional one-way relay systems. However, the channel estimation problem for two-way relay systems is more complicated than that of one-way relay systems. In this paper, we propose and compare two channel estimation algorithms, namely the superimposed channel training scheme and the two-stage channel estimation algorithm, for two-way multiple-input multiple-output (MIMO) relay communication systems, where the individual channel state information (CSI) for the first-hop and second-hop links is estimated. For both algorithms, we derive the optimal structure of the source and relay training sequences which minimize the mean-squared error (MSE) of channel estimation. In the superimposed channel training scheme, the power allocation between the source and relay training sequences is optimized. For the two-stage channel estimation algorithm, we optimize the power allocation at the relay node between two stages to improve the performance of the algorithm. Numerical examples are shown to demonstrate and compare the performance of the proposed channel training algorithms.

Joint Transceiver Optimization for Two-Way MIMO Relay Systems With MSE Constraints

“…Such quasi-static channel model has been widely used in two-way MIMO relay communications [6]- [8]. Two destination nodes can know the channel state information (CSI) of H i,r and H r,i , i = 1, 2, through channel training and estimation [12]. One of the source nodes takes the responsibility for the optimization of B 1 , B 2 , and F, and then transmits them to other nodes.…”

“…Now the original joint source, relay, and receive matrices optimization problem (10)- (11) can be solved using the proposed iterative algorithm. This algorithm starts at random feasible B 1 , B 2 , and F. At each iteration, we first optimize W 1 and W 2 based on B 1 , B 2 , and F from the previous iteration using (12). Then we update F with given B i and W i , i = 1, 2, by solving the problem (19)-(21).…”

Channel Estimation for Two-Way Relay Networks in the Presence of Synchronization Errors

“…Most existing channel estimation techniques for TWRNs have assumed perfect synchronization between the two source nodes, such that the two training sequences sent by the two sources can be perfectly superimposed at the relay [13]. However, in practice, the two sources cannot synchronize with each other perfectly, and inevitable synchronization errors will occur [14].…”

Blind estimation of MIMO relay channels

“…However, the instantaneous CSI is unknown in real wireless communication systems, and thus, has to be estimated at the destination node. One of the possible solutions is by sending known training sequences to assist in the estimation of the instantaneous CSI [3]- [4]. The main problem with the training-based channel estimation algorithms is the high cost involved in sending the training sequences, considering the limited bandwidth available for wireless communication.…”