Multi-hop WiMAX Research Articles

Performance Impact of Relay Selection in WiMAX IEEE 802.16j Multi-hop Relay Networks

Worldwide Interoperability for Microwave Access network accepts the challenge of last mile wireless access for internet. IEEE 802.16 standard, commercially known as WiMAX provide wireless broadband experience to the end subscribers and challenges many wired solutions like Digital Subscriber Line (DSL) and cable internet. Wireless network has many inherent issues like coverage holes; capacity optimization and mobility are few of them. Adding relays to multi-hop WiMAX IEEE 802.16j network present an effective solution to address them to some extent but this amendment does not elaborate any algorithm regarding the relay selection and narrate no performance guarantees. In this work, we proposed linear model that fairly allocates wireless resources among subscribers in 802.16j network. A relay selection algorithm is also presented to optimally select nodes with higher signal-to-noise ratio as relay station for nodes with lower signal-to-noise ratio objectively maximize overall network capacity. This scheme further extends network coverage area and improves network availability. We also did extensive performance evaluation of the proposed linear model. Results show that optimal relays selection scheme do provide a substantial increase of up to 66% in overall network capacity in the fixed WiMAX network. This improvement is substantial at places where network condition is not optimal. Investigating the problem further leads to the conclusion that the relay selection criterion is the key to achieve maximum network capacity.

An Opportunistic Packet Scheduling Algorithm for Load Balancing (LoBO) in IEEE 802.16j Multi-hop Relay-Enhanced Mobile WiMAX Network

We consider a IEEE 802.16j multi-hop relay-enhanced Mobile WiMAX network with a full frequency-reuse capability, in which an orthogonal frequency division multiple access-based time-division duplex...

Multi-Hop WiMAX Networks: A New Opportunistic Algorithm Using AMC and PUSC Mode for Different Mobility Users

Resource allocation algorithms play the main role in provisioning high throughput in broad band wireless communications. The previous studies in WiMAX networks have considered either AMC or PUSC techniques for the resource allocation algorithms. In this way, AMC based algorithms have presented high throughput for low speed users. Conversely, PUSC based algorithms have not been affected by users' speed, whilst the throughput is low. To date, the importance of presenting proportional fair and maintaining the network throughput for the users with different speeds has not been acknowledged yet. This paper presents a novel opportunistic algorithm which is suitable for the users with different mobility speeds. The new algorithm uses two modes of AMC and PUSC simultaneously. The simulation results reveal that in comparison to similar algorithms, the proposed algorithm presents more proportional fair throughput when there are both high and low speed users.

A Novel Scheduling Algorithm for Low and High Mobility Users in Multi-hop WiMAX Network

QoS provisioning and high capacity for high mobility users are considered as the distresses of broadband wireless communications (BWC) and specifically the key technology of WiMAX. Hence, the scheduling and resource allocation algorithms play the main role in this regard. In the research conducted on scheduling algorithms in WiMAX network, two principal methods of AMC and PUSC are used. The high capacity in AMC mode algorithms is achieved by considering the low speed users. Conversely, in PUSC mode algorithms, speed does not affect the network performances; however, the capacity is low. To date, the importance of presenting QoS and maintaining the network capacity for the users with different speeds has not been acknowledged yet. This paper presents novel scheduling algorithms and also new frame partitioning scheme which are proper for the users with different mobility speeds. The new algorithm uses two modes of AMC and PUSC simultaneously to maintain the high capacity of the network. QoS is also provided. The simulation results reveal that our algorithm increases capacity while it presents low packet delay and packet loss rate in the presence of both high and low mobility speed users.

A New Distributed Scheduling Algorithm for Bandwidth Allocation in IEEE 802.16 Mesh Networks

Multi-hop WiMAX networks has the potential of easily providing high-speed wireless broadband access to areas with little or no existing wired infrastructure. IEEE 802.16 incorporates the quality of service (QoS) mechanisms at the Media Access Control (MAC) level, but it doesn’t define a specific allocation algorithm. The implementation was left open to the service providers’ diligence. Scheduling in WiMAX became one of the most challenging issues, since it was responsible for distributing available resources of the network among all users. Providing QoS in multi-hop WiMAX networks such as WiMAX mesh or mobile multihop relay networks is challenging as multiple packets can collide if they are scheduled at the same time. To warranty the QoS requirements, the 802.16 equipment must run some algorithm to allocate slots for connections. We propose an efficient distributed algorithm for packets scheduling in multi-hop WiMAX mobile networks. It is based on the 802.16e parameters, bandwidth request sizes and QoS requirements. The algorithm ensures a dynamic bandwidth allocation for the 802.16 various service classes. Assuming that the packets arrivals follow a Poisson process we build an algorithm witch calculate the number of time slots required for each packet according to its service class and its length.

Secure and Service-Oriented Framework for WiMAX Network

WiMAX is a Worldwide Interoperability for Microwave Access wireless communication system, which provides broadband access with large-scale coverage. To effectively set up multihop WiMAX networks, security is one of the major challenges that must be addressed. Another important issue is how to support different services and applications in WiMAX networks. In this article, we propose a service-oriented and secure network control framework for WiMAX networks. In the design of this framework, we consider both the security requirements of the communications and services WiMAX applications that have not been fully addressed previously in the network layer design. The proposed framework consists of two basic components: a service-aware control framework and a unified routing scheme. This paper can provide a guideline for the design of a more secure and practical WiMAX network.

Fairness Time-Slot Allocation and Scheduling with QoS Guarantees in Multihop WiMAX Mesh Networks

The WiMAX technology has been defined to provide high throughput over long distance communications and support the quality of service (QoS) control applied on different applications. This paper studies the fairness time-slot allocation and scheduling problem for enhancing throughput and guaranteeing QoS in multihop WiMAX mesh networks. For allocating time slots to multiple subscribe stations (SSs), fairness is a key concern. The notion of max-min fairness is applied as our metric to define the QoS-based max-min fair scheduling problem for maximizing the minimum satisfaction ratio of each SS. We formulate an integer linear programming (ILP) model to provide an optimal solution on small-scale networks. For large-scale networks, several heuristic algorithms are proposed for better running time and scalability. The performance of heuristic algorithms is compared with previous methods in the literatures. Experimental results show that the proposed algorithms are better in terms of QoS satisfaction ratio and throughput.

QoS aware transmission control scheme for multihop WiMAX network

SUMMARYThe IEEE 802.16j Mobile Multihop Relay (MMR) WiMAX network allows the number of hops between the end user and the base station to be more than two hops. It supports non‐real‐time Polling Service, which considers the minimum reserved rate and the maximum sustained rate as a QoS requirements. The reliability of sending the data over MMR WiMAX is achieved by using Transmission Control Protocol (TCP) in transport layer and automatic repeat request in the link layer. However, the use of automatic repeat request in the link layer makes the round trip time fluctuate rapidly, which increases the possibility of retransmission timeout (RTO) expiration. TCP performance degrades because of frequent timeout, and hence the QoS transmission rates cannot be satisfied. Therefore, this paper presents an RTO smoothing scheme and QoS aware transmission control to enhance the performance of data transmission over MMR WiMAX networks. The RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold and maximum congestion window are adjusted to satisfy the required QoS and it provides transmission rate fairness for the users at different hops. The results showed that, the proposed schemes reduce the timeout, and improve the utilization of the allocated resources and TCP throughput. Copyright © 2012 John Wiley & Sons, Ltd.

DiffServ-Aware Pricing for Wireless Internet

In this work we propose a new pricing scheme for the wireless Internet services over WiMAX system. First, let us review the characteristics of wireless network which is based on multi-hop relay WiMAX system. Next, we show why usage-based and QoS-aware pricing scheme is needed in the wireless Internet. After that, we propose a theoretical model for the price of multimedia services called a DAP (DiffServ-aware pricing) scheme for the WiMAX multimedia network which takes into account the consumed radio resource of WiMAX system as well as the supported QoS in the IP backbone network. Finally, we present explicit formulae for the packet price, price of consumed radio resource, and price of consumed bytes.

Effects of Novel Long Life Routing Algorithms on IEEE 802.16 Throughput Improvement Methods for Various Vehicular Velocities

In this paper, effects of Fastest Path Routing, Ant-Colony Routing, Associativity Based Routing (ABR) and other novel proposed Associativity Based Long Life Routing algorithms, on novel proposed throughput improvement algorithm Most Congested Access First (MCAF), minimizing the packet loss ratio and improving the throughput of a multi-hop mobile WIMAX network are investigated for various vehicular velocities. The proposed Long Life Routing algorithms are shown to provide more throughput improvement for all vehicular velocities and provide longer life routes.

Admission Control and Flow Scheduling for IEEE 802.16 WiMAX Networks with QoS Requirements

Multihop WiMAX networks show a lot of promise as the last mile in broadband connections for streaming audio and video to users. Such WiMAX networks are based on IEEE 802.16, which specifies the service classes for Q u a l i t y o f S e r v i c e ( QoS), but leaves the admission and scheduling mechanisms open. This paper presents a flow admission control and scheduling scheme for multihop WiMAX networks based on IEEE 802.16. Our admission control and scheduling scheme ensures that the various QoS parameters for the 802.16 service classes are met. We present our flow admission control and scheduling scheme and simulation results for this scheme. We then compare it in terms of QoS provided, with a simple admission and scheduling scheme and an admission scheme proposed by Ghosh et al. in [1]. Simulation results show that our scheme indeed guarantees the QoS parameters (minimum assured bandwidth, maximum allowable packet delay, maximum allowable packet jitter) needed by the different service classes of 802.16.

Analysis of Transparent and non-Transparent relay modes in IEEE 802.16j Mobile Multi-Hop relay networks

Two different relay modes are defined in IEEE 802.16j WIMAX standard: transparent mode and non-transparent mode. The non transparent mode is used to extend the coverage area of base stations, where low cost relay station of equal capacity as that of base station is placed at suitable position. Time taken to accept mobile stations and Bandwidth allocation are main problems in non transparent mode. In this we have studied the IEEE 802.16j standard multi hop relay WIMAX networks. We have used relay stations to extend the coverage of base stations. We have also analyzed the throughput between mobile stations with in the coverage area and outside coverage area of base stations. We have simulated the IEEE 802.16j transparent and non transparent mode multi hop WIMAX relay networks using NCTUns Tool.

Effects of routing algorithms on novel throughput improvement of mobile ad hoc networks

A cognitive method called most congested access first (MCAF), minimizing the packet loss ratio and improving the throughput of a multihop mobile WiMAX network, is proposed. MCAF combines both the time division multiple access and the orthogonal frequency division multiple access methods. MCAF additionally uses spectral aid and buffer management methods, which are proposed in this paper, to manage both spectrum access and packets in the buffers. By using these novel methods, real-time video and voice packet transmission is achieved, data packet loss rate is minimized, and the system throughput per node is improved. Effects of fastest path and ant colony routing algorithms on throughput improvement methods are investigated. It is shown that the fastest path routing algorithm provides higher throughput values than the ant colony routing algorithm.

Architectures and protocols for wireless mesh, ad hoc, and sensor networks

Welcome to this special issue of the Wiley’s Wireless Communications and Mobile Computing Journal. This special issue is devoted to the topic of the latest research and development in the field of wireless communications and networking. During the last few years, we have witnessed a tremendous interest from academia, industry, and standardization bodies in wireless mesh, ad hoc, and sensor networking. With several appealing characteristics, such as dynamic self-configuration, self-organization, self-healing, easy maintenance, and high scalability, wireless mesh networks have been prodded as a cost-effective approach to support high-speed last mile connectivity and ubiquitous broadband access in the context of home, enterprise, and community networking. Wireless ad hoc networks have also shown applications in a variety of situations, such as battlefields, disaster recovery/rescue operations, and entertainment. At the same time, wireless sensor networks are being deployed and actively researched for various forms of environmental monitoring, home automation, military, and civilian applications. Despite recent advances, and the technical accumulations from more than a decade’s research effort in wireless networking, many research issues remain open in all protocol layers of wireless mesh, ad hoc, and sensor networks. For example, the foreseen multi-channel, multi-radio, and multi-antenna hybrid architectures (infrastructure and ad hoc) have brought new challenges in the design of physical, MAC, and routing protocols. New application scenarios are urging researchers to address enhanced quality of service support and various security issues in the design of different protocol layers for wireless mesh, ad hoc, and sensor networks. This special issue is dedicated to various aspects of wireless mesh, ad hoc, and sensor networks. We selected eight papers to show the recent advances in architectures and protocols. The papers cover both topical and innovative areas. A detailed overview of the selected papers is given below. In “Radio resource management of self-organizing OFDMA wireless mesh networks,” Chu et al. present a cognitive resource management system for wireless mesh networks with self-organizing base stations to optimize the available spectrum. The authors first present the concept of radio resource management based on an extensive literature survey and then highlight the challenges to achieve the best performance of such systems in future wireless mesh networks. In “IP address assignment in wireless mesh networks,” extending a work that received a best paper award in LCN 2008, Zimmermann et al. introduce and evaluate a novel auto-configuration protocol for wireless mesh networks, dubbed DWCP for Dynamic WMN Configuration Protocol. The proposed protocol deals with assigning unique addresses, managing the free and assigned addresses, reacting autonomously to failures and features support of conventional Dynamic Host Configuration Protocol (DHCP) clients. The proposed protocol has been deployed and evaluated in a real testbed and showed a good potential. In “CORE: centrally optimized routing extensions for efficient bandwidth management and network coding in the IEEE 802.16 MeSH mode,” Mogre et al. propose CORE, a new system that targets the optimization of routing, scheduling and bandwidth savings via network coding. Based on new heuristics, CORE has been evaluated through simulations and the obtained results demonstrated its performance. In “Study of Patching-based and Caching-based videoon-demand in mutli-hop WiMax mesh networks,” Xie et al. provide a study of two cross layer techniques, the Patching-based scheme and the Caching-based scheme, to provide video-on-demand in multi-hop WiMax mesh networks. Both approaches employ a novel joint solution of admission control and channel scheduling for video streams in the lower layers. This joint solution guarantees the data rate for the admitted video streams, which is crucial for real-time video streaming application. Their extensive simulations showed a good performance of this joint solution under real system settings. In “A security framework for wireless mesh networks,” Mogre et al. develop a holistic approach toward securing the wireless mesh networks with a particular focus on the network layer. They provide a set of solutions that guarantee the integrity and authenticity of routing messages, detect misbehaviors in forwarding data or routing messages, and dynamically manage reputation of nodes throughout the network. The combination of these building blocks enables a secure and self-organizing wireless mesh networks as they demonstrated it through their implementation and tests of a realistic IEEE 802.16 mesh network.

Variable Quantum Deficit Round Robin Scheduling for Improved Fairness In Multihop Networks

To increase the coverage area, Multichip WiMAX networks are particularly useful without the need to deploy expensive base stations. One of the most common variants in Multihop WiMAX is the Wireless Mesh Networks.Scheduling algorithms for WiMAX has been a topic of interest for a long time since the very inception of WiMAX networks. Though a lot of literature is available for scheduling in point–tomultipoint (PMP) networks, relatively less emphasis has been on scheduling in Multihop networks. One problem inherent with Multihop networks is unfairness between users with different service class types. This problem is even worse with real time bursty traffic. This necessitates the need for a scheduling algorithm that allows a fair share of resources among the users. In this work, we propose a vqDRR based scheduling mechanism that provides Quality of Service while at the same time maintaining fairness among users in a Multi-hop networks. We compare the performance of the proposed algorithm with the fair distributed credit based scheduler in terms of latency, throughput utilization and fairness.

Ubiquitous fair bandwidth allocation for multimedia traffic on a WiMAX mesh network with multi-channels

WiMAX technology can be used as ''last mile ubiquitous'' broadband connections to deliver streaming audio or video to clients. Thus, Quality of Service (QoS) is very important for WiMAX networks. Providing QoS in multi–hop WiMAX networks such as WiMAX mesh networks is challenging since the WiMAX mesh networks MAC is connectionless based. The scheduling function plays a crucial role in QoS support. However, multimedia traffic is bursty in nature, therefore, in this paper, we will discuss the potential unfairness that bursty traffic may be subjected to and propose a new frame–based packet scheduling algorithm.

Analytical Model of QoS-Based Fast Seamless Handoff in IEEE 802.16j WiMAX Networks

The IEEE 802.16 standard adopts a centralized resource-allocation mechanism to poll nodes with three polling modes, i.e., the unicast, multicast, and broadcast polling modes, depending on the residual bandwidth of the base station (BS). In the multicast and broadcast polling modes, the BS uses the truncated binary exponential backoff (TBEB) algorithm as the contention-resolution process (CRP) for mobile nodes to access the wireless network while the traffic load increases up to saturation. The random contention-based TBEB used in the initial ranging and bandwidth request suffers from high collision probability under a high traffic load. TBEB thus significantly degrades the grade of service (GoS), particularly while performing handoff in the mobile (IEEE 802.16e) or multihop relay WiMAX (IEEE 802.16j) networks. Additionally, WiMAX's TBEB exhibits two critical problems. First, TBEB neglects the node priority (i.e., the new or handoff node) and the service flow class (i.e., the real-time or nonreal-time service class); thus, it cannot achieve the optimal network revenue. Second, all different-priority connections immediately transit to the same minimum contention windows (CWs) after winning contentions and then easily lead to high collision probability at succeeding contentions. Therefore, this paper first proposes an efficient contention-resolution algorithm that consists of three key contributions: 1) providing the adaptive minimum-maximum backoff-value algorithm (AM^2) to partition collision domains; 2) supporting a dynamic waiting-penalty algorithm (DWP) for successful contentions; and 3) differentiating the decrements of CWs (DDW) to avoid collisions, even though the contentions randomly choose the same CW value. Second, we model the proposed approach as a discrete-time Markov chain model and then mathematically analyze several important metrics, i.e., the collision probability, access delay, GoS, and throughput. Numerical results indicate that the analytical results are very close to the simulation results, which justify the accuracy of the analytical model. Additionally, the proposed approach outperforms IEEE 802.16 and all compared approaches in collision probability, delay, GoS, and network throughput.

The Research of Security Network Group Key Management

To improve the security and applicable capability of the group key management in 802.16e standard, the traditional group key management mechanism is discussed and the current security owing to lack of considering comprehensive factors, some security solutions designed also bring some problems. To solve these issues, Current multi-hop Wimax group key management security solutions were described firstly, then One-way Function Tree group key management mechanism is analyzed; An efficient group key management scheme based on one-way function is proposed, which can be used in multi-hop Wimax network system to enhance the security of group management effectively. Analysis result shows that, compared with the methods of One-way Function Tree, he proposed scheme has better performance in key storage, key updating and key calculation cost, which provides an effective solution for group key management in Wimax network and has better application value.

Improvement of Channel Assignment Scheme for WiMax Mesh Networks

The IEEE 802.16 standard, also known as Worldwide Interoperability for Microwave Access (WiMax), provides a mechanism for deploying high-speed wireless mesh network in metropolitan areas, and Quality of Service (QoS) is thus very important for WiMax networks. While being scheduled at the same time, the multiple links may interfere with one another that makes it challenging to provide QoS in multi-hop WiMax mesh networks. In this paper, we propose the LMDFS (Layered Maximum Degree First Select) algorithm for channel assignment in multi-channel single-transceiver WiMax mesh network. The goal is to eliminate the interference, to allow multiple non-interfering links to be scheduled at the same time and to increase the throughput of traffic flows. The simulation results show that this proposed algorithm greatly reduces the length of scheduling and improves the throughput and the average delay from network nodes to the BS in insufficient channels.

Dynamic hybrid automatic repeat request (DHARQ) for WiMAX – Mobile multihop relay using adaptive power control

Wireless multihop network is currently attracting much attention as a new wireless broadband access technology due to numerous benefits. This work proposes a power control scheme for WiMAX multihop relay system. In contrast to existing power control and optimization approaches, our proposed method uses an adaptive Channel Quality Measurement for a relay station to reduce interferences to other mobile station (MS) or relay station (RS) within the same cell and hence increase the number of hops per link and consequently maximize the spatial reuse. The proposed power control is applied to a new dynamic HARQ algorithm for adaptive channel quality enhancement. Simulation results have indicated that the proposed approach achieves superior BER/PER performance enhancement in comparison to previous related works.