Non-transparent Relay Stations Research Articles

Cooperative data transmission framework for IEEE 802.16j mobile multihop relay networks

IEEE 802.16j Mobile Multihop Relay specification is an amendment of the IEEE 802.16 standard and it is developed to extend IEEE 802.16e. Quality of Service (QoS) constrained service flow management is an important issue related to these networks. In the situation where the link quality between a superordinate station and one of its subordinate Non-Transparent Relay Stations (NTRSs) is poor then it is difficult to fulfill the QoS requirements of the flows that are passing through that NTRS. To handle such situations, in this paper, a novel Cooperative Data Transmission (CDT) framework is proposed. It uses the Transparent Relay Stations (TRSs) which are the common neighbors of the NTRSs and their superordinate stations to fulfill the QoS requirements of the flows that are passing through the NTRSs. The changes required to the network entry, path establishment, bandwidth allocation and data transmission processes of the IEEE 802.16j standard for the CDT framework are proposed in this paper. Also, the performance gains achievable with the proposed CDT framework in terms of the throughput are analyzed numerically. The upper and lower bounds on the throughput gain are obtained. Through simulations, the performance of the proposed CDT framework is studied and compared with the performance of the normal data transmission where no cooperation from TRSs is involved in the data transmission. The CDT framework showed significant performance advantages when compared with the normal data transmission method.

English

Mobile Multi-hop Relay (MMR) WiMAX network uses Relay stations (RSs) to extend the cell coverage, and enhances the link quality and the throughput. In MMR WiMAX networks, the number of hops between the Subscriber stations (SSs) and the Base station (BS) is allowed to be more than two hops when Non transparent RS (NT-RS) is used. However, this requires modification to the frame structure of NT-RS to reduce the delay of relaying the data packets across multiple hops. Therefore, this paper presents a new NT-RS frame structure aimed to decrease the multi-hop relaying delay in order to improve the performance of the data transmission over MMR WiMAX network. The proposed frame structure serves the sub-ordinate SSs as well as NT-RSs in the access zones, while using the relay zones to communicate with its super-ordinate stations. The performance of the proposed frame structure is tested through a simulation work. The results showed that,the forwarding delay is reduced, and hence the link layer and the Transmission control protocol (TCP) throughput are improved significantly.   Key words: IEEE 802.16j, transmission control protocol (TCP) performance, non transparent relay stations (NT-RS), frame structure.

Optimal Max–Min Fair Resource Allocation in Multihop Relay-Enhanced WiMAX Networks

In this paper, an optimal resource allocation scheme is proposed for WiMAX networks that are enhanced with nontransparent relay stations (RSs). We first focus on two-hop relaying networks, because this scenario has the largest throughput gain. Furthermore, several researchers have proposed different resource allocation schemes in two-hop relaying networks, and thus, we can compare the performance of our proposed scheme with the following two well-known schemes in terms of cell throughput, outage rate, and computational time: 1) orthogonal and 2) overlapped . We then explore an extension of the proposed scheme to a general multihop relaying scenario by taking into account spatial reuse in both the access and relay zone periods. The numerical results show that the highest cell throughput can be achieved by the proposed optimal scheme while maintaining the fairness and lower outage performance of the orthogonal scheme at a higher computational cost. Moreover, the cell throughput degradation from increasing the number of hops from two to three hops, under the proposed optimal scheduling scheme, is only 12% and 19% when six and nine RSs are deployed, respectively.

Orthogonal frequency division multiple access resource allocation in mobile multihop relay networks using an adaptive frame structure

ABSTRACTFor wireless mobile multihop relay (MMR) networks, we have chosen orthogonal frequency division multiple access (OFDMA) and time division duplex as a multiple access scheme and a duplex communication technique, respectively. We have also selected nontransparent relay stations (nt‐RSs) as relay nodes to extend the MMR network coverage. Through the nt‐RSs, far‐off subscriber stations (SSs) or hidden SSs can communicate with a base station (BS) that is connected to backhaul networks. In these MMR networks, the way in which a BS and nt‐RSs use OFDMA resources (e.g., OFDMA symbols and subcarriers) and share them might reduce system capacity and network throughput. Therefore, we proposed a new adaptive OFDMA frame structure for both the BS and the nt‐RSs. The proposed scheme is the first approach that incorporates the adaptive technique for wireless MMR networks. Based on the proposed adaptive OFDMA frame structure, an adaptive OFDMA resource allocation for SSs within a BS as well as nt‐RSs was proposed. To derive the maximum OFDMA resource that nt‐RSs can be assigned and to synchronize access zones and relay zones between a superior station and its subordinate nt‐RSs, three properties are introduced: a data relay property, a maximum balance property, and a relay zone limitation property. In addition, we propose max‐min and proportional fairness schemes of the proposed adaptive frame structure. Our numerical analysis and simulations show that the proposed OFDMA allocation scheme performs better than the nonadaptive allocation scheme in terms of network throughput and fairness especially in the asymmetric distribution of subscriber stations between access zones and relay zones in the MMR networks. Copyright © 2011 John Wiley & Sons, Ltd.

Secure and Efficient Multicast Rekeying Approach for Non-Transparent Relay-Based IEEE 802.16 Networks

Many emerging applications that depend on secure group communications demand the privacy of participants and access control at the multicast server. The multicast and broadcast services in IEEE 802.16 are efficient and power saving mechanisms, which no doubt also provide subscribers with strong and powerful security protection from the theft of service by encrypting broadcast connections between subscriber station (SS), relay station (RS), non-transparent relay station (NRS) and Multihop relay base station (MR-BS). However, the existing multicast and broadcast rekeying algorithm (MBRA) not only facing forward secrecy, backward secrecy and scalability problems for IEEE 802.16e but also for multi- hop relay based networks both in centralized as well as distributed zone. Although many researches try to give solutions for the above problems, all of them focus mainly on IEEE 802.16e networks and none of paper is published on distributed relay-based Wimax networks. This paper illustrates the main security problem of MBRA in general which is scalability, backward and forward secrecy and proposes a new Secure and efficient distributed Relay- based Rekeying Algorithm (SEDRRA) scheme for non- transparent Multihop IEEE 802.16 networks. The proposed scheme uses non-transparent decode and forward relays. Both analysis and performance evaluation show that our scheme can significantly reduce the complexity and solve all of the above problems in an efficient way.

Adaptive Cost-Based with Max–Min AMC Routing Algorithm for Increasing Utilization and Reducing Blocking in IEEE 802.16j WiMAX Networks

Based on the IEEE 802.16e standard, WiMAX has proposed a relay-based mechanism, namely IEEE 802.16j, to extend the service area of the Multihop Relay Base Stations (MR-BSs) and to improve the Received Signal Strength quality. IEEE 802.16j thus can achieve two significant advantages: extending the WiMAX service area with a low-cost solution and compatible with the existing WiMAX specifications. The Relay Station (RS) can be classified into three types: Fixed RS, Nomadic RS and Mobile RS according to diverse features of mobility and relaying range. A multihop-relay WiMAX network including various types of RSs exhibits a critical routing issue, i.e., how to determine an efficient relay-based routing path between a Mobile Station (MS) and a MR-BS. This paper thus proposes an IEEE 802.16j-conformed relay-based adaptive competitive on-line routing approach that focuses on the Non-Transparent Relay-Station (NT-RS) mode, where the path with the least cost and the highest AMC coding rate will be selected in terms of the link bandwidth, path length and channel conditions. Numerical results indicate that the proposed routing approach significantly outperforms other approaches in Fractional Reward Loss, network utilization and average end-to-end path delay.

Relay Performance Analysis of TTR and STR Relay Modes in IEEE 802.16j MMR System

The IEEE802.16j standard uses non-transparent relay stations to extend coverage. There are two types of non-transparent relay modes, that is, the time-division transmit and receive (TTR) relay mode which can operate with one of two types of frame structures, a single-frame and multiframe structure, and the simultaneous transmit and receive (STR) relay mode. In this paper, we analyze the relay performance of TTR and STR relay modes in IEEE 802.16j MMR system. We also propose a fair resource allocation scheme for the downlink relay frame. Numerical results show that relay performance of the TTR with a single-frame or a multiframe structure and that of the STR relay modes are almost the same in a two-hop system. However, in a three-hop system, the TTR mode with a single-frame structure outperforms other relay modes.