Efficient Power Allocation and Relay Selection Schemes for Two-Way AF Relay Systems and Their Application to Wireless Multihop Networks

• Main Authors: Cho, Ting-Nan, 卓庭楠
• Other Authors: Wang, Chin-Liang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/03413356423685313632

博士 === 國立清華大學 === 通訊工程研究所 === 102 === Two-way relaying, using relays to accomplish information exchange between two source nodes, has been extensively investigated in recent years because it not only can obtain spatial diversity gain but also can provide the same channel utilization efficiency as end-to-end transmission. Because building communication links between the two sources in two-way relaying depends on the relays, system performance in turn depends on using the relays as efficiently as possible. In this dissertation, we develop efficient power allocation (PA) and relay selection (RS) schemes based on overall symbol error probability (OSEP) for two-way amplify-and-forward (AF) relay systems, in which multiple single-antenna relays and reciprocal channels are considered and only one relay will cooperate with two source nodes. We first analyze an asymptotic OSEP (AOSEP) with closed-form in terms of second-order channel statistics and the transmit power of each participating node with M-ary quadrature amplitude modulation (M-QAM) and M-ary phase-shift keying (M-PSK) modulation schemes, and then introduce a statistical channel state information (SCSI)–based PA scheme by minimizing the AOSEP with a total transmit power constraint. In addition, using the SCSI-based PA, we propose a RS scheme by selecting one relay for cooperation in achieving the minimum OSEP value, which has diversity order one. Note that both the individual symbol error probabilities (SEPs) at the two sources are the same when using the SCSI-based PA; that is SEP balancing. To further improve system performance in terms of OSEP, we then present an instantaneous channel state information (ICSI)–based PA scheme using the SEP balancing approach; the PA scheme leads to the instantaneous received signal-to-noise ratios (SNRs) at the two sources being balanced. Following this observation, we then develop an ICSI-based RS scheme that finds one relay for transmission that has the maximum balanced received SNR and provide an achieved diversity order analysis of the ICSI-based schemes by deriving the lower and upper bounds of asymptotic overall outage probability. We also provide simplified PA-RS schemes by incorporating a path-loss model into the SCSI-based schemes, i.e., geographic information (GI)–based PA-RS schemes. Using the GI-based PA-RS schemes, we then study the maximum transmission coverage and the relaying area under a given OSEP requirement; the results show that the optimal relay location for maximizing the transmission coverage is at the center coordinates of the two sources, and that the relaying area shrinks as the geographic distance between the two sources increases. Furthermore, we apply the proposed PA-RS schemes to wireless two-way multihop AF relay networks. We first propose a cooperative multihop transmission structure for the networks, in which a number of single-antenna relays are addressed and distributed between two sources. The proposed transmission structure can decompose the multihop networks to several independent two-way two-hop AF relay systems; therefore, the proposed PA-RS schemes can be adopted for use in the systems to enhance the transmission reliability of the networks. Our data show that the proposed transmission structure provides more effective throughput performance than a related method with almost the same frame error rate, whether or not the proposed PA-RS schemes are used. Moreover, according to the structure characteristics, we present a cooperative two-way routing protocol that consists mainly of a GI-based forwarder selection part and a SCSI/ICSI/GI-based RS part, where the forwarder selection part is used to reduce the number of transmission hops, and the RS part is applied for enhancing the reliability of the communication links.