Distributed Relay Selection Scheme Research Articles

Bandwidth allocation and distributed relay selection for multiple‐user and multiple‐relay cooperative systems using Stackelberg game

SummaryCooperative communication is an ongoing research area which lies on the basic idea of transmission of information from the transmitter to the receiver with the assistance of a virtual array of relay nodes in between, which will eventually provide the spatial diversity. This paper deals with the resource allocation (bandwidth in this case) among multiple users (source‐ destination pairs) in a cooperative communication environment along with the relay selection when there are multiple relay nodes to assist the transmitting nodes to pass on their data signal to respective receivers. A multi‐user, multi‐relay system model is considered here on which Amplify‐and‐Forward relaying scheme is applied. The bandwidth allocation and relay selection are done based on the Stackelberg game according to which transmitting nodes are treated as purchasers and relaying nodes are treated as vendors. By this planned approach, the transmitting nodes can discover the relays at comparatively better positions and can purchase the optimal bandwidth from those helping relays. By this approach, the relays which are competing with each other can increase their own utilities by demanding the optimal prices and the multiple users which are competing with each other can maximize their own utilities by demanding the optimal bandwidths. Distributed relay selection scheme is applied here which does not require precise information of channel state information as opposed to Centralized scheme and it gives comparable results, too.

System Design, DMT Analysis, and Penalty for Non-Coherent Relaying

In a two-hop system with multiple amplify-and-forward (AF) relays, the instantaneous channel state information (CSI) is usually required at the relays to achieve a coherent combining at the destination. In this paper, we investigate the design of non-coherent relaying systems, where no CSI is available at the relays. It will be shown that non-coherent relaying can achieve the optimal diversity and multiplexing tradeoff (DMT) of coherent relaying systems with no penalty in the coding length, but incurs a loss of combining gain. To illustrate the practicality of non-coherent relaying, we propose a simple spreading-based non-coherent relaying scheme which achieves the optimal diversity gain. However, the spreading scheme demonstrates a unique non-coherent penalty, namely, the inclusion of one non-coherent relay may introduce negative contribution to the receive SNR. To handle this penalty, a distributed relay selection scheme, which can achieve a better outage performance with less energy, is proposed.

Efficient and Reliable Broadcast in Intervehicle Communication Networks: A Cross-Layer Approach

Broadcast transmission is an effective way to disseminate safety-related information for cooperative driving in intervehicle communication (IVC). However, it is fraught with fundamental challenges such as message redundancy, link unreliability, hidden terminals, and broadcast storms, which greatly degrade network performance. In this paper, we introduce a cross-layer approach to design an efficient and reliable broadcast protocol for emergency message dissemination in IVC systems. We first propose a novel composite relaying metric for relay selection by jointly considering geographical locations, physical-layer channel conditions, and moving velocities of vehicles. Based on the relaying metric, a distributed relay-selection scheme is proposed to assure that a unique relay is selected to reliably forward the emergency message in the desired propagation direction. We further apply IEEE 802.11e enhanced distributed coordination access (EDCA) medium-access control (MAC) to guarantee quality-of-service (QoS) provisioning to safety-related services. In addition, an analytical model is developed to study the performance of the proposed cross-layer broadcast protocol (CLBP) in terms of the relay-selection delay and the emergency message access delay. Network Simulator (NS-2) simulation results are given to validate our analysis. It is shown that the CLBP not only can minimize the broadcast message redundancy but can quickly and reliably deliver emergency messages in IVC as well.