Joint Impact of Hardware Impairments and Imperfect Channel State Information on Multi-Relay Networks

Abstract

In this paper, we investigate the performance of dual-hop (DH) decode-and-forward (DF) multi-relay networks, for which two practical deleterious factors are taken into account, namely hardware impairments (HIs) and imperfect channel state information (ICSI). The communication between the source and the destination is realized with the aid of DF multi-relays, where both hops are assumed to be independent but non-identically distributed α-µ fading. Aiming at improving the system performance, three representative relay selection strategies are considered, in which the best relay is selected according to the link quality of source-to-relay and/or relay-to-destination. To characterize the performance of the proposed strategies, two key performance metrics, namely outage probability (OP) and ergodic capacity (EC), are analyzed insightfully. We first derive closed-form expressions for both exact and asymptotic OPs. Utilizing the derived results, diversity orders achieved at the destinations are obtained. We demonstrate that the OPs of considered networks are limited by HIs and ICSI, and the diversity orders are zeros due to the presence of ICSI. Then, we study the ECs of the proposed relay selection schemes, and upper bounds for the EC and asymptotic expressions for the EC in the high signal-to-noise ratio (SNR) regime are derived. To obtain more insights, the affine expansions for the EC are involved by two metrics of high-SNR slope and high-SNR power offset. It is shown that there are rate ceilings for the EC due to HIs and ICSI, which result in zero high-SNR slopes and finite high-SNR power offsets. INDEX TERMS α − µ fading channels, hardware impairments, imperfect CSI, relay selection. I. INTRODUCTION A. BACKGROUND Cooperative communication has been identified as one of the core technologies in the current and future wireless communication networks [1]. With the aid of relays, we can potentially extend the coverage of wireless networks, improve quality of service (QoS) and reduce energy consumption [2]. For these reasons, it thus has attracted considerable interests from both The associate editor coordinating the review of this manuscript and approving it for publication was Rui Wang.

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“…Thus, we generate a local copy of the distortion vector received by the targeted users on the transmitter side, so that it can be used to adapt the precoded vector s and would be canceled when the latter is amplified and passed through the channel. To calculate the distortion vector, we use an initial estimate of the vector s 0 using the direct approximate models PAs which introduce the NL distortion on the signal (10), in the same way as the real PAs in the real transmission, i.e., expressed by d = F (s) − Ws.…”

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