An Efficient Relay Node Placement Scheme for Two-Way MIMO Multi-Hop Networks in Practical Indoor Environments

Relay deployment has been gaining attention for network designers. Recently, MIMO Two-way Multi-hop Network (M2WMN) where all links share the same frequency is introduced as a relaying scheme which achieves higher spectral efficiency than other conventional multi-hop schemes. A power control strategy for M2WMN has been proposed to alleviate the frequency-sharing interference problem which degrades the scheme´s performance. However, for ease of analysis, the past studies on M2WMN just theoretically assumed Rayleigh fading model for all links of the network. This assumption is far from reality where the channels of different links might experience different pathloss conditions including shadowing. This paper conducts 3D ray-tracing simulation in a U-shaped corridor environment to attain practical propagation channels. Based on the channel data, this paper studies the performance of different multi-hop schemes and investigates an open problem of choosing optimal relay placement which can maximize the performance of M2WMN in real environments. Our results show that without power control, the optimal locations are where adjacent nodes are both in Line-of-Sight (LOS). Interestingly, the optimal locations are no more LOS environments when power control is applied. In addition, this paper also proposes a sub-optimal relay placement search algorithm relaxing the complexity of exhaustive search.