Spatial Modulation Exploited in Non-Reciprocal Two-Way Relay Channels: Efficient Protocols and Capacity Analysis

Abstract

In this paper, the concept of spatial modulation is exploited in two-way relay channels, where two single-antenna source terminals exchange information through an assisting multi-antenna relay node, and thereby two novel transmission strategies are proposed based on the decode-and-forward protocol, aiming to achieve high throughput. One strategy is to simply engage spatial modulation in the transmissions of the relay node, whereas the other is to develop transmit diversity with spatial modulation for further benefiting from the feature of two-way relaying. Neither of the strategies requires channel state information at the transmitter and, therefore, the assumption of channel reciprocity that is commonly used in two-way relay channels can be released herein. To evaluate the performance of both proposed strategies, their capacity behaviours are analysed and numerical comparisons are established in metrics of achievable rate region and sum-rate. Subsequently, the first strategy, simple spatial modulation, is generalized into the two-way relaying with multiantenna source terminals, to improve the flexibility in system design and demonstrate the tractability of spatial modulation. Illustrative discussions on bit error rate not only substantiate the validity of the proposed strategies, but also provide useful tools for the two-way relaying layout without the restriction of channel reciprocity.

Mapping-Varied Spatial Modulation for Physical Layer Security: Transmission Strategy and Secrecy Rate

“…As a consequence, the secrecy rate of the mapping-varied spatial modulation with finite-alphabet input, R s , is achieved by substituting (22) and (24) into (21). Further, based on (23) and (29), the limit of the secrecy rate in (21) at the SNR ρ → +∞ is…”

“…To begin with, we consider the metric of ergodic secrecy rate that is defined as E{C s } in the case of Gaussian-distributed input and E{R s } in the case of finite-alphabet input, where C s and R s are given by (7) and (21), respectively.…”

“…Originally, spatial modulation is initiated to improve the spectral efficiency of multi-antenna channels in an open-loop link, where the transmitter does not know the legitimate receiver's CSI [16]- [18]. The performance of this approach has been considered in various networks [19]- [21]. Recently, optimal spatial-design [22] and power allocation [23] have been developed for spatial modulation in closedloop links to further increase its achievable data rate, where the CSI over the legitimate link is available at the transmitter.…”

On the Performance of Spatial Modulation MIMO for Full-Duplex Relay Networks

“…where F |h SR | (ω) is given as follows: Finally, the expression of APEP (14) follows by inserting (53) in (52), and then subsequently solving the integral in (52) using [65,6.631] and with the aid of some simplifications. This concludes the proof.…”

“…Briefly, in [52]- [54], an FD two-way relaying scheme with SM is considered, where two sources communicates with each other using a multi-antenna relay node. In particular, in [52] and [53], the relay node operates in HD mode, and hence the system is free from the effects of SI. In [52] and [54], both the sources are multi-antenna nodes, and the demodulator is built on the assumption that no direct is available between them.…”