TY - JOUR
T1 - Optimal training design for MIMO-OFDM two-way relay networks
AU - Kang, Jae Mo
AU - Kim, Il Min
AU - Kim, Hyung Myung
N1 - Publisher Copyright:
© 1972-2012 IEEE.
PY - 2017/9
Y1 - 2017/9
N2 - In this paper, we study a training design problem for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) two-way relay networks. Unlike the existing studies, we assume the spatially correlated fading and consider the nonreciprocal channel condition, which is a more practical assumption but makes the training problem more challenging. The equivalent channels of bidirectional relaying links, which consist of self-interfering channels and information-bearing channels, are estimated at each source node based on a linear minimum mean square error (LMMSE) approach. The total mean square error (MSE) of the channel estimation is minimized under the transmit power constraints at the source nodes and at the relay. To solve this problem, we first derive an optimal structure of the training signals, and then, convert the optimization problem into a tractable convex form, from which the optimal training scheme is designed efficiently. Furthermore, for a practical special case, the optimal training design is derived in semi-closed form, which provides useful insights. To reduce the required complexity, a low-complexity training scheme is also derived in closed-form. This scheme is shown to be asymptotically optimal in the high signal-to-noise ratio (SNR) regime and gives further insights into the optimal training. The performance of the proposed schemes is demonstrated through numerical simulations.
AB - In this paper, we study a training design problem for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) two-way relay networks. Unlike the existing studies, we assume the spatially correlated fading and consider the nonreciprocal channel condition, which is a more practical assumption but makes the training problem more challenging. The equivalent channels of bidirectional relaying links, which consist of self-interfering channels and information-bearing channels, are estimated at each source node based on a linear minimum mean square error (LMMSE) approach. The total mean square error (MSE) of the channel estimation is minimized under the transmit power constraints at the source nodes and at the relay. To solve this problem, we first derive an optimal structure of the training signals, and then, convert the optimization problem into a tractable convex form, from which the optimal training scheme is designed efficiently. Furthermore, for a practical special case, the optimal training design is derived in semi-closed form, which provides useful insights. To reduce the required complexity, a low-complexity training scheme is also derived in closed-form. This scheme is shown to be asymptotically optimal in the high signal-to-noise ratio (SNR) regime and gives further insights into the optimal training. The performance of the proposed schemes is demonstrated through numerical simulations.
KW - Amplify-and-forward relay
KW - channel estimation
KW - MIMO-OFDM
KW - spatial fading correlation
KW - training design
KW - two-way relay
UR - http://www.scopus.com/inward/record.url?scp=85030129133&partnerID=8YFLogxK
U2 - 10.1109/TCOMM.2017.2679194
DO - 10.1109/TCOMM.2017.2679194
M3 - Article
AN - SCOPUS:85030129133
SN - 1558-0857
VL - 65
SP - 3675
EP - 3690
JO - IEEE Transactions on Communications
JF - IEEE Transactions on Communications
IS - 9
M1 - 7873263
ER -