Opportunistic Relay Selection Protocol under Multi-User Environment

Abstract

In this paper, a relay selection issue is studied to improve data rate performance in a multi-user environment. Previous opportunistic relay selection protocols only consider channel condition in relay selection. However, the target performance is affected by other system attributes, such as delay and load in relay node (RN). The proposed relay selection scheme, which is based on analytic hierarchy process (AHP), adopts signal-to-noise ratio (SNR), switching, and the number of connections to RN as a selection criteria. Also, a special form of eigenvector is proposed and proved analytically. From the proposed eigenvector, the computational complexity is obviously reduced. Target system performance is examined under different weighting parameter values to the above attributes. This work shows that average data rate can be maximized corresponding to the number of RN. Simulation results reveal the benefits of the proposed scheme over the conventional opportunistic relay selection scheme and the threshold-based relay switching selection scheme. The performance of our scheme is verified in terms of average data rate and distribution of the data rate.

Parallelised relaying protocol with opportunistic priority assignment for enhanced spectral efficiency in cross‐relay interference

“…A conventional OPS protocol [11] is based on the orthogonal two‐phase transmission to avoid the cross‐relay interference. Thus, in the OPS protocol, the received signal at the relay in phase 1 can be expressed as where denotes the transmitted symbol from the source and denotes the additive white Gaussian noise (AWGN) at the relay k in phase 1.…”

“…Note that the large‐scale fading effect is also considered in these transmit SNRs. The conventional OPS protocol is to select a relaying pair with the highest effective SNR among the relays at every time [11]. Thus, the relay selection algorithm to maximise the spectral efficiency (or instantaneous capacity) is given by However, in the OPS protocol, another relaying pair does not transmit (or receive) the data to its destination (or from the source) while the selected relaying pair transmits the data.…”

“…Therefore, the relaying system has been considered as one of the core technologies for the fifth generation cellular mobile communications [3], and its applications can be extended to device‐to‐device [4], vehicle‐to‐everything [5], and internet of things [6]. In order to improve the spectral efficiency, various conventional relaying schemes have been investigated [7–11]. In [7–10], several different approaches have been proposed for optimal power allocation with channel state information (CSI) between the source and the relay to maximise the signal‐to‐noise ratio (SNR).…”

“…In [7–10], several different approaches have been proposed for optimal power allocation with channel state information (CSI) between the source and the relay to maximise the signal‐to‐noise ratio (SNR). In [11], an opportunistic relay selection scheme was proposed to improve the data rate. However, since the conventional relaying system has a condition in that it needs to distinguish between the transmission time from the source to the relay and the time from the relay to the destination, it leads to a reduction in the spectral efficiency of the relaying system.…”

Inter-Relay Interference Mitigation for Chirp-Based Two-Path Successive Relaying Protocol

“…In the relay power allocation technique, since the relay power controls not only the transmission coverage but also the transmission performance, various research has been done to optimize the relaying power [13,14]. In the relay selection technique, since a wireless channel environment is randomly fluctuated, an opportunistic relay selection (ORS) protocol that selects the optimal relay among multiple relays based on channel state has been proposed [15]. In order to operate the ORS protocol, there are several objectives for selecting the optimal single relay, such as the minimum bit error rate (BER), the maximum system throughput [16], and the minimum power consumption [17].…”