Abstract-This paper considers a two-way half-duplex decode-and-forward relaying system, where multiple pairs of single-antenna users exchange information via a multiple-antenna relay. Assuming that the channel knowledge is nonideal and the relay employs maximum ratio processing, we derive a largescale approximation of the sum spectral efficiency (SE) that is tight when the number of relay antennas M becomes very large. Furthermore, we study how the transmit power scales with M to maintain a desired SE. In particular, three special powerscaling cases are discussed and the corresponding asymptotic SE is deduced with clear insights. Our elegant power-scaling laws reveal a tradeoff between the transmit powers of the user/relay and pilot symbol. Finally, we formulate a power allocation problem in terms of maximizing the sum SE and obtain a local optimum by solving a sequence of geometric programming problems. Index Terms-Decode-and-forward, geometric programming, massive MIMO, power-scaling law, two-way relaying.
Our previous work of REF has revealed this tradeoff for the decode-and-forward relaying system.
Multipair Two-Way Half-Duplex DF Relaying With Massive Arrays and Imperfect CSI
IEEE Transactions on Wireless Communications
IEEE Transactions on Wireless Communications
Computer Science Mathematics