A multi-hop resource scheduling algorithm for IEEE 802.16j relay networks

The IEEE 802.16j standard defines both transparent and non-transparent relay transmission mode. The present study formulates and optimizes the relay resource scheduling problem for the case of a non-transparent relay network. It is shown that the resource scheduling problem is NP-Complete. A method is proposed for optimizing the position of the zone boundary adaptively during the resource scheduling process in order to maximize the system throughput. In addition, a low time complexity algorithm designated as MRRS (multi-hop relay resource scheduling) is proposed to obtain an approximate solution for the NP-Complete scheduling problem. In the proposed algorithm, the zone boundary is adjusted adaptively in accordance with the user distribution and the channel state information in such a way as to improve the utilization of the available slots. The simulation results show that MRRS achieves a higher throughput than existing relay resource scheduling algorithms (GenArgMax and Eliminate-Repeat) with no significant loss in fairness. In addition, it is shown that the performance improvement provided by MRRS increases as the hop-count is increased.     

Efficient and adaptive resource scheduling in IEEE 802.16j transparent relay networks

Relaying is regarded as a promising technique for enhancing the system throughput and coverage of emerging broadband wireless access networks. While next generation broadband wireless standardization bodies (e.g., LTE-advanced and IEEE 802.16j) have specified the support of relays in general terms, the problem of allocating network resources in an efficient and effective manner remains a challenging issue. In this study, the utility-based resource scheduling optimization problem for IEEE 802.16j transparent relay networks is formulated mathematically and proven to be NP-hard. Two efficient heuristic algorithms, namely Relay Resource Scheduling (RRS) and Adaptive Relay Resource Scheduling (ARRS), are proposed to resolve the resource scheduling problem. RRS maximizes the system utility in networks containing direct and relay mobile stations by exploiting the benefits of optional transmissions. ARRS enhances upon the performance of RRS by adaptively determining the split ratio between the access zone and the transparent zone in the downlink subframe. The computational complexities of both algorithms are shown to be polynomial and proportional to the number of links and subchannels in the network. The simulation results show that the proposed algorithms achieve significantly better throughput and fairness performance than existing schemes such as Partial Proportional Fairness (PPF) and GenArgMAX.     

Efficient forwarding scheme for downlink broadcast messages in IEEE 802.16j multi-hop relay networks

Although the IEEE 802.16j standard introduces a connection identifier (CID)-based forwarding scheme and a tunnel-based forwarding scheme, these schemes exhibit poor performance when forwarding broadcast messages. This study considers a CID translation strategy and proposes two CID-translated forwarding schemes for IEEE 802.16 multi-hop relay networks. The basic CID-translated forwarding scheme does not require to append the relay MAC header of the tunnel-based scheme to the broadcast messages. The enhanced CID-translated forwarding scheme further divides a broadcast message into a common part and a specific part and forwards these parts in a multicast manner and a broadcast manner, respectively. Simulation results validate that the basic CID-translated forwarding scheme uses fewer resources than the tunnel-based forwarding scheme. Moreover, the enhanced CID-translated forwarding scheme outperforms the basic CID-translated forwarding scheme in terms of the system resources used and transmission latency.     

LASER: A load-aware spectral-efficient routing metric for path selection in IEEE 802.16j multi-hop relay networks

For coverage extension and throughput enhancement, the IEEE 802.16j task group has developed a novel multi-hop relay network architecture to enable typical IEEE 802.16 networks to achieve data transmission between base stations and mobile stations via a multi-hop path with relay stations deployment. How to determine an effective path for throughput gain and overhead reduction is emerging and crucial in IEEE 802.16 multi-hop relay networks. This paper introduces a load-aware spectral-efficient routing metric, called LASER, to evaluate paths, and proposes an efficient scheme to determine a proper path. Based on the LASER metric, the proposed path selection scheme formulates the path cost as the summation of cost of each link, and the path with the minimum cost will be selected as the appropriate one. Simulation results show that the proposed LASER-based path selection scheme significantly outperforms existing path selection schemes in network throughput and map overhead.     

Multiple frequency reuse schemes in the two-hop IEEE 802.16j wireless relay networks with asymmetrical topology

In this paper, throughput performance of the access links (i.e., base station to mobile station and relay station to mobile station) is analyzed for the two-hop IEEE 802.16j wireless relay networks with asymmetrical topology. In specific, three frequency reuse schemes are proposed to improve the spectrum efficiency of the access links: (1) an isolation band based frequency reuse scheme (IBFRS) which introduces an isolation band surrounding each relay station (RS) cluster (i.e, a separate RS or several adjacent RSs) so that the throughput of the access link can be improved by allowing frequency reuse between RSs and the base station (BS); (2) the dynamic frequency power partition (DFPP) scheme for reusing the frequency among RSs; (3) the selective reuse (SR) scheme for the RSs to further selectively reuse the frequency in the isolation band according to the interference measurement. Comprehensive simulation shows that by applying the proposed IBFRS+DFPP+SR, the throughput of the access link can be significantly improved.     

IEEE 802.16j中继站睡眠模式改进算法

IEEE 802.16j标准在IEEE 802.16e标准的基础上引入了中继站。中继站睡眠模式是能量节省的重要手段。其中各参数的选取关系到RS睡眠模式的效果——平均能量消耗和平均帧时延。用概率统计的方法构建了IEEE 802.16j RS睡眠模式下的能量消耗模型和帧时延模型,通过对睡眠模式各窗口参数的分析,提出了根据业务流动态改变窗口参数的算法,并且对改进前后的算法进行了仿真分析。     

Performance analysis of authentication and key distribution scheme for mobile multi-hop relay in IEEE 802.16j

Mobile multi-hop relay (MMR) network is known to be easy to install and convenient to manage because of its self-organizing and self-healing characteristics. However, MMR is vulnerable to security problems because of the same reason. In this paper, we propose a new hybrid authentication and key distribution algorithm for IEEE 802.16j MMR service. The proposed scheme uses centralized authentication when a mobile station or a relay station initially joins the MMR network and uses distributed authentication for hop-by-hop authentication between mobile nodes. We examine the procedure of the proposed scheme and its usefulness when applied to MMR networks. We also analyze the performance of the hybrid scheme. The proposed scheme can be used in any mobile multi-hop network as well as IEEE 802.16j MMR network.     

A novel radio resource allocation scheme for IEEE 802.16e multicell networks

In this paper,we propose a new media access control (MAC) protocol,which is compatible with the IEEE 802.16e-2005 Orthogonal Frequency Division Multiple Access (OFDMA) wireless interface.In this protocol,the same radio resource can be shared by neighboring cells in the wireless mesh network (WMN) and collisions can be reduced in the overlapping areas.This protocol consists of two schemes: a downlink transmission and an uplink transmission.For downlink transmission we use a cross layer adaptive radio resourc...     

IEEE 802.16j中继站睡眠模式的研究

IEEE 802.16j标准在IEEE 802.16d/e标准的基础上引入了中继站。由于有的中继站具有便携、游牧,甚至移动的特性,往往采用电池或者太阳能供电的方式,中继站的能量节省问题也随之而来。中继站睡眠模式作为能量节省的重要手段,对其进行研究是十分必要和有用的。介绍了IEEE 802.16j RS睡眠机制,并构建了中继站睡眠模式下的能量消耗模型和帧时延模型。然后用概率统计的方法对模型进行了仿真,并就各参数对平均能量消耗和平均帧时延的影响进行了分析。     

一种基于IEEE 802.16j网络的带宽调度方案*

针对IEEE 802.16j网络,提出了一种上行业务的动态联合带宽资源调度方案。根据该网络系统树状拓扑结构,在基站BS和中继站RS间采用分级分布式资源调度体制,从而既保障了业务的带宽需求,又提升了上行带宽利用率,同时还提出了针对不同类型业务采用不同的调度算法,改善了调度的公平合理性。仿真结果表明,提出的动态联合调度方案相比严格优先级调度更具灵活性,能够在兼顾用户速率公平的条件下有效地保证各种服务的QoS要求,同时也可获得较高的带宽资源利用率。     

An efficient bandwidth allocation algorithm for real-time VBR stream transmission under IEEE 802.16 wireless networks

This paper investigates variable rate control strategies for real-time multimedia variable bit rate (VBR) services over IEEE 802.16 broadband wireless networks. A data rate control mechanism is derived for the case where the uplink channel provides real-time services and the traffic rate parameter remains constant. This paper shows that the common queuing scheduling algorithms have some bandwidth allocation fairness problems for the real-time polling service (rtPS) in the MAC layer. In other words, the use of a VBR for the rtPS by a WiMAX system results in additional access latency jitter and bandwidth allocation disorder in the transmitted multimedia streams during the regular time interval polling of subscribe stations (SSs) for the contention bandwidth request period. However, the proposed scheduling algorithm solves these SSs contending with bandwidth resource allocation problems based on an extended rtPS (ertPS) of quality-of-service (QoS) pre-programming for a ranging response non-contention polling period. The adopted bandwidth allocation of max–min fairness queue scheduling uses a time constraint condition to transmit real-time multimedia VBR streaming in an IEEE 802.16 broadband wireless environment. In addition, we use the ns-2 simulation tool to compare the capacity of multimedia VBR stream and show that the proposed ertPS scheduling algorithm outperforms other rtPS scheduling algorithms.     

IEEE 802.16中改进的QoS调度算法设计

IEEE802.16标准在每个节点处都提供实时业务和非实时业务。由于基于优先级的业务的服务质量（QoS）的需求不同,因此需要对传统的调度算法进行改进使其具有更大的适应性。为了改善QoS端到端时延的性能,提出了一种混合调度算法（EDD和WFQ算法相结合）。仿真结果表明：在每个节点处,提出的混合算法比仅使用EDD算法能给实时业务产生的时延更少,并且还能够使单个BS在可允许的端到端时延范围内容纳数量更多的子SS,而且使用从BS到SS的GPSS模式的调度机制比使用GPC模式能产生更小的时延。     

基于IEEE 802.16e协议的公平调度算法

无线城域网标准IEEE 802.16e规定了系统的服务质量（QoS）框架,并把所有服务划分为五种类型,但没有规定具体的QoS调度算法。提出了在不同的业务类型间进行资源调度的算法,并把所有的业务流划分为领先、同步、滞后三种状态,根据业务流的类型以及其所处的状态,采取两级额外带宽再分配策略和补偿机制。仿真结果显示使用该算法提高了系统的资源利用率,同时公平性也得到很好的保障。     

An embedded fuzzy expert system for adaptive WFQ scheduling of IEEE 802.16 networks

WiMAX is a futuristic technology which provides simultaneous support for web, video, and voice applications. WiMAX networks are best suitable to real time traffic however the quantity of non real time and best effort traffic cannot be neglected. Distribution of resources in such heterogeneous applications is therefore a challenging task. There are many schedulers available for WiMAX but adaptive and adequate schedulers are still in growing stage of development. This paper introduces a novel method using which a system is developed based on concepts of fuzzy logic to schedule traffic in WiMAX networks. The proposed fuzzy expert system simplifies fair allocation of resources to real as well as non real time traffic. The implementation is based on changing the weights of the queues serving real and non- real time traffic adaptively. New weights will be calculated for each bandwidth request made to base station and these weights will in turn decide amount of bandwidth allocated to different traffic classes. The weights are calculated based on three parameters that are amount of real time and non real time traffic in queues, change in throughput requirement for non real time flows and latency requirement of real time input data. Results obtained by virtue of simulations justify the significance of the proposed method.     

Power-aware opportunistic downlink scheduling in IEEE 802.16 wireless networks

The IEEE 802.16 is a standard for fixed and mobile Broadband Wireless Access (BWA). In this paper, we deal with two key challenges of 802.16-based networks. First, terminals close to cell edge experience poor channel quality, due to severe path-loss and high interference from concurrent transmissions in nearby cells. To address this issue, we propose a framework based on a static partitioning of bandwidth into chunks with different transmission power levels. Terminals with impaired channel conditions can then benefit from being allocated a higher amount of transmission power than the others. Secondly, transmissions should be scheduled according to Quality of Service (QoS) requirements to keep users with real-time video or voice calls satisfied, while best-effort connections should fairly share the remaining capacity. To this aim, we propose a scheduling algorithm, called Power-aware Opportunistic Downlink Scheduling (PODS), that aims at meeting both the QoS and fairness requirements, while taking into account the different power levels of the bandwidth chunks. The performance of the proposed scheduler is assessed through detailed packet-level simulation in realistic scenarios and compared with well-known scheduling algorithms. Results confirm that PODS is able to exploit power boosting to provide real-time connections with the desired level of QoS, irrespectively of their MSs’ channel quality.     

IEEE802.16e的实时上行链路调度服务优化算法

深入分析了IEEE802.16e建议的三种实时调度服务算法：UGS、rtPS、ertPS，并在此基础上提出了一种优化的实时调度服务算法：irtPS。该优化的调度服务算法在保证变化数据率实时上行链路的延时性能基础上，最大限度地提高了实时上行链路的资源利用率。数学建模分析结果显示，在保证延时性能的前提下，该优化的调度服务算法的系统容量较IEEE802.16e建议算法的系统容量有显著增加。     

IEEE 802.16中改进的VoIP服务调度算法设计

提出了一种应用于IEEE 802.16系统的改进的VoIP服务上行链路调度算法,此算法是一种基于语音活动检测的调度算法,BS根据SS的语音状态转换来分配上行链路资源。它可以弥补传统的调度算法中的一些不足,例如对上行链路资源的浪费、增大MAC负载和引入附加的接入时延等。就系统的吞吐量和接入时延两方面分别对传统的算法和提出的算法作了具体地分析和仿真,结果表明,提出的算法在吞吐量和系统容量方面具有更优的性能。     

An efficient broadcast scheduling algorithm for TDMA ad-hoc networks

In this paper, we propose an efficient algorithm to find a collision-free time slot schedule in a time division multiple access frame. In order to minimize the system delay, the optimal schedule must be defined as the one that has the minimum frame length and provides the maximum slot utilization. The proposed algorithm is based on the sequential vertex coloring algorithm. Numerical examples and comparisons with the algorithm in previous research have shown that the proposed algorithm can find near-optimal solutions in respect of the system delay.Scope and purposeAn ad-hoc network was introduced in order to apply packet switching communication to a shared radio channel. Using a radio channel as the broadcast medium to interconnect users, an ad-hoc network provides flexible data communication services among a large number of geographically distributed, possibly mobile, radio units. In an ad-hoc network, since all users share a single channel by multiple access protocol, unconstrained transmission may lead to the time overlap of two or more packet receptions, called collision, resulting in damaged useless packets at the destination. Collided packets increase the system delay because they must be retransmitted. Therefore, the transmission for each station must be scheduled to avoid any collision, that is, collision-free transmission should be guaranteed. The time division multiple access (TDMA) technology can be used to schedule collision-free transmission. In this paper, we propose an efficient algorithm to find a collision-free time slot schedule in a TDMA ad-hoc network.     

An efficient message scheduling algorithm for WDM lightwave networks

Two important issues that need to be addressed when designing medium access control (MAC) protocols for Wavelength Division Multiplexing networks are message sequencing and channel assignment. Channel assignment addresses the problem of choosing an appropriate data channel via which a message is transmitted. This problem has been addressed extensively in the literature. On the other hand, message sequencing, which addresses the order in which messages are sent, has rarely been addressed. In this paper, we propose a new reservation-based message scheduling algorithm called RO-EATS that addresses both the channel assignment and message sequencing during its scheduling process. We formulate an analytical model and conduct extensive simulations to evaluate the performance of this algorithm. We compare the performance results of a well-known algorithm which only addresses the channel assignment issue with those of our new algorithm. The comparison shows that our new algorithm gives significant improvement over scheduling algorithms that do not consider message sequencing. As a result, we anticipate that these research results will lead to new approaches to message scheduling on WDM networks.     

中继网络一种改进的QAPF调度算法研究*

本文针对QAPF调度算法存在的吞吐量与公平性矛盾的问题,提出了一种改进的QAPF调度准则(RQAPF),该准则利用队列门限值降低了队列状态信息对调度准则的影响,保证了用户的公平性。但与QAPF调度准则相比,降低了系统吞吐量,进一步提出了具有载波配对的RQAPF调度算法(SubPairRQAPF),仿真表明该算法在满足系统公平性要求的同时能够提高频谱利用率。