Suitable Relay Node Research Articles

TREE: Routing strategy with guarantee of QoS for industrial wireless sensor networks

SUMMARYAs considerable progress has been made in wireless sensor networks (WSNs), we can expect that sensor nodes will be applied in industrial applications. Most available techniques for WSNs can be transplanted to industrial wireless sensor networks (IWSNs). However, there are new requirements of quality of service (QoS), that is, real‐time routing, energy efficiency, and transmission reliability, which are three main performance indices of routing design for IWSNs. As one‐hop neighborhood information is often inadequate to data routing in IWSNs, it is difficult to use the conventional routing methods. In the paper, we propose the routing strategy by taking the real‐time routing performance, transmission reliability, and energy efficiency (TREE, triple R and double E) into considerations. For that, each sensor node should improve the capability of search range in the phase of data route discovery. Because of the increase of available information in the enlarged search range, sensor node can select more suitable relay node per hop. The real‐time data routes with lower energy cost and better transmission reliability will be used in our proposed routing guideline. By comparing with other routing methods through extensive experimental results, our distributed routing proposal can guarantee the diversified QoS requirements in industrial applications. Copyright © 2012 John Wiley & Sons, Ltd.

Distributed interference-aware relay selection for IEEE 802.11 based cooperative networks

Cooperative communication has been recently proposed as a way to mitigate fading in wireless networks. Analytical results indicate that network performance improvement by cooperative communication heavily depends on selecting suitable relay nodes. Previous work on relay selection fails to consider the impact of inter-node interference among transmissions, which potentially results in a degradation of network performance. In this study, it is shown how the use of relay nodes may degrade rather than improve network performance (e.g. throughput) in scenarios where inter-node interference is not accounted for. In this approach, inter-node interference is embedded into our relay selection strategy through a newly proposed distributed interference-aware relay selection (DIRS) algorithm for IEEE 802.11-based wireless networks with multiple source–destination pairs. Under DIRS algorithm, each source–destination pair will select an optimal relay based on both the channel quality and the interference information, which can be obtained locally without the knowledge of topology information. The simulation results demonstrate the effectiveness of our proposal and show that inter-node interference can be mitigated by optimising relay selection.

A relay path selection method for video streaming on shared terminals

As broadband network services and video streaming systems become more common, high-definition (HD) quality stream format has become increasingly popular in live video distribution. Today’s video streaming systems are used for a variety of purposes, but those systems require much bandwidth and CPU power for video streams. In this paper, we focus on the design of a relay path selection method on community-based resource sharing networks, which is able to select and use suitable stream paths cooperatively in sharing resources. On live video distribution, a candidate relay path list is created when users request to receive live video streams, and the best path is selected. If a new relay node is required, the suitable relay node is placed on a shared terminal in consideration of available resource status. Our experiments by a prototype system show that our method is successful in realisation of the suitable relay path selection and live video streaming on shared terminals.

OFDMA Cellular Networks with Opportunistic Two-Hop Relays

We investigate the benefits of two-hop opportunistic relay in time division duplex (TDD) OFDMA cellular network configurations. The paper starts with a short analytical model for the two-hop opportunistic relay. The model expresses the probability of finding a suitable relay node in the presence of lognormal fading and it allows the computation of the expected number of out-of-coverage nodes, as well as the end-to-end spectrum efficiency increase due to opportunistic relaying. The paper then presents results for Monte Carlo simulations of opportunistic relay in some realistic scenarios. Specifically, the simulations consider two scenarios. The first scenario uses the propagation model and a wide-area 19-cell configuration specified in 802.16 OFDMA cellular standard evaluation methodologies. In the second scenario, a Manhattan-like 19-cell topology is used. Our simulations show 11% to 33% in throughput increase when the opportunistic relay technology is used. Our results evaluate the benefits of the opportunistic relay in both scenarios in terms of coverage extension and throughput increase.

A Relay-Based MAC Protocol for Multi-Rate and Multi-Range Infrastructure Wireless LANs

Auto rate adaptation mechanisms have been proposed to improve the throughput in wireless local area networks with IEEE 802.11a/b/g standards that can support multiple data rate at the physical layer. However, even with the capability of transmitting multi-packets with multi-rate IEEE 802.11 PHY, a mobile host near the fringe of the Access-Point's (AP's) transmission range still needs to adopt a low-level modulation to cope with the lower signal-to-noise ratio (SNR), Thus, it can not obtain a data rate as high as that of a host near AP in most cases. According to the characteristics of modulation schemes, the highest data rate between a pair of mobile hosts will be inversely proportional with the transmission distance. Considering these factors, we here demonstrate a Relay-Based Adaptive Auto Rate (RAAR) protocol that can find a suitable relay node for data transmission between transmitter and receiver, and can dynamically adjust its modulation scheme to achieve the maximal throughput of a node according to the transmission distance and the channel condition. The basic concept is that the best modulation schemes are adaptively used by a wireless station to transmit an uplink data frame, according to the path loss condition between the station itself and a relay node, and that between the relay node and AP, thus delivering data at a higher overall data rate. Evaluation results show that this scheme provides significant throughput improvement for nodes located at the fringe of the AP's transmission range, thus remarkably improving overall system performance.

An Opportunistic Relay Method for Increasing Throughput in Multirate IEEE 802.11 Wireless LAN

In this letter, we demonstrate a Relay-based Adaptive Auto Rate (RAAR) protocol that can find a suitable relay node for data transmission between transmitter and receiver, and can dynamically adjust its modulation scheme to achieve the maximal throughput of a node according to the transmission distance and the channel condition. Evaluation results show that this scheme provides significant throughput improvement for nodes located at the fringe of the AP's transmission range, thus remarkably improving overall system performance.