Provisioning of Parameterized Quality of Service in 802.11e Based Wireless Mesh Networks

There has been a growing interest in the use of wireless mesh networks. Today’s wireless technology enables very high data rate up to hundreds of Megabits per second, which creates the high demand of supporting real-time multimedia applications over wireless mesh networks. Hence it is imperative to support quality of service (QoS) in wireless mesh networks. In this paper, we design a framework to provide parameterized QoS in 802.11e based wireless mesh networks. Our framework consists of admission control algorithms and scheduling algorithms, which aim at supporting constant bit-rate (CBR) traffic flows, as well as variable bit-rate (VBR) traffic flows. We first present deterministic end-to-end delay bounds for CBR traffic. We then prove that the delay of VBR traffic can be bounded if the traffic flow conforms to a leaky-bucket regulator. We further study different admission control algorithms for VBR traffic. Our simulation results show that, by taking advantage of statistical multiplexing, much more traffic flows can be admitted.     

On delay constrained CAC scheme and scheduling policy for CBR traffic in IEEE 802.11e wireless LANs

CBR (constant bit rate) traffic is expected to be an important traffic source in wireless networks. Such sources usually have stringent jitter or delay requirements and in many cases they should be delivered exactly as they were generated. In this paper, we propose a strictly guaranteed QoS (quality‐of‐service) provisioning CAC (call admission control) scheme with a polling‐based scheduling policy for CBR traffic in IEEE 802.11e wireless LANs. Under such a scheme, the proposed transmit‐permission policy for HCCA (HCF controlled channel access) method can forecast the maximum suffered delay for each packet and derive sufficient conditions so that all the CBR sources satisfy their time constraints to provide deterministic QoS guarantees. A simple analytical model is carried out to estimate the average queueing delay of the proposed scheme. In addition to theoretical analysis, simulations are conducted to validate its promising performance. Our simulation results show that the proposed scheme maintains a high throughput with respect to the whole range of system load. Copyright © 2009 John Wiley & Sons, Ltd.     

Design and Implementation of a QoS Oriented Data-Link Control Protocol for CBR Traffic in Wireless ATM Networks

This paper presents a QoS oriented Data Link Control (DLC) framework for transporting Constant Bit Rate (CBR) traffic over wireless ATM links. Data link control is usually omitted in fixed ATM networks because cell corruption due to channel error is extremely rare for reliable media like copper wire and optical fiber. However, for wireless, higher bit error rates are quite common due to shadowing and other fading effects. The purpose of DLC in wireless is to provide error-free transport to the higher layers by recovering corrupted cells at the link layer. A selective reject (SREJ) automatic repeat request (ARQ) based DLC protocol is used for CBR error recovery. For an ARQ based scheme, higher recovery rates can be achieved with larger cell transfer delay, caused by cell retransmissions. Since cell transfer delay and DLC recovery rate both translate to user-perceivable Quality-of-Service (QoS), it is important for the DLC to strike a balance between these two, depending on the application's requirements. To achieve this in our protocol, the retransmission procedure for a CBR cell is constrained to complete within a recovery time interval which is specified by the application at call-setup time. Also, a novel jitter removal scheme that reduces the cell delay variation caused by cell loss and retransmissions, is incorporated as a part of the DLC protocol. The proposed protocol is implemented on NEC's WATMnet prototype system. The implementation and its experimental results are reported for illustrating the performance and feasibility of the presented CBR DLC protocol. The experimental results show that the DLC protocol can be successfully applied for QoS-constrained error recovery of CBR traffic on a per-connection basis. These also indicate that the DLC can be programmed to attain a desirable tradeoff between cell transfer delay and cell recovery rate.     

一种新的用于IEEE 802.11e EDCA中提供QoS的方法

该文提出了一种新的应用于IEEE 802.11e EDCA (Enhanced Distributed Channel Access)中提供QoS(Quality of Service)的方法。这种方法是将几个时隙组合起来构成一个超时隙,每个超时隙的开始分配给不同的业务来进行发包。时隙的分配是根据各种业务的不同优先级来实现的。这种方法可以保证高优先级业务具有较大的吞吐量,较少的MAC延时和较低的丢包率。与802.11e EDCA草案中提出的不同冲突窗口大小的方法相比,这种方法具有可以提高吞吐量,降低丢包率,并能减小站点数目变化对高优先级业务吞吐量的影响等优点。这种新的提供QoS的方法优于不同冲突窗口大小的方法,在IEEE 802.11e EDCA中应用超时隙方法可以大大提高EDCA的性能。     

A hierarchical HFC network with QoS guaranteed traffic policy

The rapid growing of the Internet makes multimedia and broadband services closer to the users. For people at home, two typical networks are available to access the Internet: telephone network and CATV network. This paper presents a hierarchical tree-based structure for the hybrid fiber-cable (HFC) network where the traditional HFC network is partitioned into segments. Each segment is coordinated by a central traffic controller (CTC). A reservation-based traffic policy is also proposed for the CTC to schedule the data transmissions within the segment to provide guaranteed QoS, such as constant bit rate (CBR) service and variable bit rate (VBR) service. The CTC also furnishes the bridging function so that local traffic within the controlled segment is filtered to save the network bandwidth. Based on the segmentation concept and filtering function, the bandwidth can be reused efficiently and the system performance is improved significantly. Simulation results indicate that the proposed hierarchical HFC network performs much better than the traditional HFC network in terms of delay, delay jitter and channel utilization. Through the proposed traffic policy, the hierarchical HFC network also offers guaranteed QoS for the users     

A QoS aware joint design for wireless mesh networks

Wireless mesh networks (WMNs) provide Internet access to remote areas and wireless connections on a metropolitan scale. In this paper, we focus on the problem of improving the gateway throughput in WMNs while achieving fairness and supporting quality-of-service (QoS) differentiation for end-users. To address this problem, we propose a new distributed dynamic traffic scheduling algorithm that supports different QoS requirements from different users. We also develop a joint weight-aware channel assignment and minimum expected delay routing mechanism. Simulation results demonstrate the performance of the proposed work in terms of the achieved throughput and minimized packet loss ratio and delay.     

A calculus for network delay. II. Network analysis

For pt.I see ibid., vol.37, no.1, p.114-31 (1991). A method to analyze the flow of data in a network consisting of the interconnection of network elements is presented. Assuming the data that enters the network satisfies burstiness constraints, burstiness constraints are derived for traffic flowing between network elements. These derived constraints imply bounds on network delay and buffering requirements. By example, it is shown that the use of regulator elements within the network can reduce maximum network delay. It is also found that such a use of regulator elements can enlarge the throughput region where finite bounds for delay are found. Finally, it is shown how regulator elements connected in series can be used to enforce general burstiness constraints     

Hybrid offset‐time and burst assembly algorithm (H‐OTBA) for delay sensitive applications over optical burst switching networks

Optical burst switching (OBS) is the most favourable switching paradigm for future all‐optical networks. Burst assembly is the first process in OBS and it consists of aggregating clients packets into bursts. Assembled bursts wait for an offset time before being transmitted to their intended destinations. Offset time is used to allow burst control packet reserve required resources prior to burst arrival. Burst assembly process and offset‐time create extra delay in OBS networks. To make OBS suitable for real time applications, this extra latency needs to be controlled. This paper proposes and evaluates a novel offset time and burst assembly scheme to address this issue. Constant bit rate (CBR) traffic that has stringent end‐to‐end delay QoS requirements is used in this study. The proposed scheme is called hybrid offset‐time and burst assembly algorithm (H‐OTBA). The objective of the paper is achieved by controlling maximum burst transfer delay parameters of CBR. The proposed scheme was evaluated via network simulation. Simulation results demonstrate that, H‐OTBA has effectively reduced end‐to‐end delay for CBR traffic compared with current solutions. Copyright © 2014 John Wiley & Sons, Ltd.     

Distributed probabilistic medium access with multipacket reception and Markovian traffic

Enabling multipacket reception (MPR) at the physical layer is a promising way to achieve higher bandwidth efficiency while reducing the complexity of the medium access control layer in distributed wireless networks. We study distributed probabilistic access where transmitting nodes access the shared wireless medium with a probability based on the node’s information about the aggregate traffic carried by the network. We model bursty traffic by rate-controlled two-state Markov sources and introduce a parameter that describes the “burstiness” level of the offered traffic. A throughput-optimal medium access strategy utilizing limited feedback is then described and its performance is examined for traffic with different levels of burstiness. It is shown that the bursty nature of the traffic in data networks allows for improvement of the bandwidth efficiency. Bounds on the system throughput are proposed and the queuing delay is analyzed.     

QoS in WiMAX hybrid schedulers for heterogeneous traffic and their performance comparison

ABSTRACT

Worldwide Interoperability for Microwave Access (WiMAX), based on IEEE 802.16, provides first-mile wireless access for broadband users and is capable of satisfying the Quality of Service (QoS) requirements of voice, video and data traffic (triple-play services). This paper proposes two WiMAX hybrid schedulers, developed by integration of homogeneous schedulers, for providing QoS to triple-play services. The Markovian model is solved analytically to derive various performance metrics, which are then compared with an existing scheduler. The splitting of FTP traffic, before scheduling, provides improved throughput as compared to the proposed first hybrid scheduler, making this an exclusive component of the proposed second hybrid scheduler. The results show that the second proposed model provides an improvement of mandatory QoS parameters; reduction in voice traffic mean queuing delay by 68.18%, and improvement in FTP traffic throughput by 67.27% as compared to the first designed model. The first considered scheduler gives high inter-class fairness; however, it does not provide satisfactory QoS performance. The proposed hybrid schedulers are better in overall performance than other schedulers proposed recently, as they not only satisfy the QoS demands of different types of services but also improve the fairness among services.     

On the effects of traffic mixtures in direct broadcast satellite networks

In this paper we present a multi‐criterion control simulation in a realistically complex environment of a satellite network, involving non‐symmetric up and downlinks. Direct broadcast satellite (DBS) networks carrying heterogeneous traffic is characterized with challenges, such as high traffic burstiness, wireless channel dynamics, and large, but limited capacity. On the other hand, there are system characteristics that can be leveraged to address these challenges such as in centralized topology, different levels in quality of service (QoS) and priorities, availability of side information about channel conditions, flexibility in delivery of delay insensitive traffic, etc. We have developed an adaptive resource allocation and management (ARAM) system that takes the advantage of such characteristics to maximize the utilization of the available capacity on the forward DBS link, while maintaining QoS in the presence of channel effects and congestion in the network. Since variable‐bit‐rate (VBR) video traffic is given priority over available‐bit‐rate (ABR) data traffic in the ARAM concept, in this paper we investigate the impact of the fraction of VBR load in overall load. Copyright © 2002 John Wiley & Sons, Ltd.     

A Bandwidth Reservation Multiple Access Protocol for Wireless ATM Local Networks

A bandwidth reservation multiple access scheme(BRMA) is proposed to resolve contention and assignbandwidth among multiple users trying to gain access toa common channel such as in mobile users contending for resources in an ATM-based cellular networkor a wireless local area network (LAN) with shortpropagation delays. The protocol is best suited tosupport variable-bit-rate (VBR) traffic that exhibits high temporal fluctuations. Each mobile user isconnected end-to-end to another user over virtualchannels via the base station that is connected to thewired ATM B-ISDN network. The channel capacity is modeled as a time frame with a fixed duration.Each frame starts with minislots, to resolve contentionand reserve bandwidth, followed by data-transmissionslots. Every contending user places a request for data slots in one of the minislots. If therequest is granted by the base station through adownlink broadcast channel, the user then startstransmission in the assigned slot(s). The number ofassigned slots varies according to the required qualityof service (QoS), such as delay and packet lossprobability. A speech activity detector is utilized inorder to indicate the talkspurts to avoid wastingbandwidth. Due to its asynchronous nature, BRMA is ratherinsensitive to the burstiness of the traffic. Since theassignment of the minislots is deterministic, therequest channels are contention-free and the data channels are collision-free. Hence, in spite ofthe overhead (minislots) in each frame, BRMA provideshigher throughput than Packet Reservation MultipleAccess (PRMA) for the same QoS, especially for high-speed systems. A better delay performance is alsoachieved for data traffic compared to Slotted Alohareservation-type protocol PRMA. In addition, BRMAperforms better in terms of bandwidth efficiency thanthe conventional TDMA or the Dynamic TDMA, wherespeech activity detectors are very difficult toimplement.     

一种改善IP网络中基于类的数据服务QoS的调度方法

IP网络中基于类的数据服务QoS支持一般包括包的延时、吞吐量和丢失率,目前的研究成果大都集中于对其中某一个指标的确保或支持。该文提出一种在IP网络中一个网络路由器节点上同时考虑类间流量带宽、包丢失和延时区分的队列管理调度算法,称为动态比例自适应算法(Dynamic Proportional Adaptive Algorithm,DPAA)。该算法是针对比例区分服务PDS(Proportional Differentiated Services)中流量负载频繁变化的情况提出的。仿真实验通过与前人提出的基于比例区分服务模型的调度算法比较,证明了DPAA 算法的有效性。     

一种基于IEEE802.11支持QoS自适应调度器模型和算法

这篇文章提出了能够有效支持QoS的IEEE802．11自适应调度器模型。和以往的支持QoS的调度器模型相比，这里根据在主控接入点(MAP：Master Access Point)和用户终端(UT：User Termination)的各自延时需求对满足不同的传输机制的分组流进行自适应调度。这种机制不仅完全兼容当前支持QoS的IEEE802．11MAC协议标准，而且能够有效减少由于实时传输带来的分组延时，增加满足不同信道负载和带宽要求的数据流的吞吐率。实时测试得到的数据基本验证了这个要求。     

A QoS Aware Dynamic Scheduling Scheme Using Fuzzy Inference System for IEEE 802.16 Networks

Providing quality of service (QoS) for diverse multimedia services is an important issue in IEEE 802.16 (WiMAX) networks. A scheduling mechanism that satisfies the QoS requirements has become more important for multimedia networks. In addition, scheduling algorithms for wireless networks are much more complex than that of wired networks because of channel quality variations and radio resource limits. This paper introduces a QoS Aware Scheduling System, based on fuzzy logic, for traffic management in WiMAX point-to-multi-point (PMP) networks. The proposed method attempts to guarantee delay and throughput QoS criteria. It considers QoS criteria and radio quality of each user in decision making processes. A series of simulation experiments have been carried out to evaluate the performance of the proposed scheduling system. The results show that the proposed method performs effectively to achieve QoS criteria and attains significant system performance for different types of traffic.     

Provisioning QoS controlled media access in vehicular to infrastructure communications

The emerging IEEE 802.11p standard adopts the enhanced distributed channel access (EDCA) mechanism as its Media Access Control (MAC) scheme to support quality-of-service (QoS) in the rapidly changing vehicular environment. While the IEEE 802.11 protocol family represents the dominant solutions for wireless local area networks, its QoS performance in terms of throughput and delay, in the highly mobile vehicular networks, is still unclear. To explore an in-depth understanding on this issue, in this paper, we develop a comprehensive analytical model that takes into account both the QoS features of EDCA and the vehicle mobility (velocity and moving directions). Based on the model, we analyze the throughput performance and mean transmission delay of differentiated service traffic, and seek solutions to optimally adjust the parameters of EDCA towards the controllable QoS provision to vehicles. Analytical and simulation results are given to demonstrate the accuracy of the proposed model for varying EDCA parameters and vehicle velocity and density.     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.     

无线信道动态树碰撞解决算法的性能分析

一般的随机访问信道(RACH)，延时特性只有均值，很难有明确的上限保证，所以对部分实时业务性能难以保证。树型算法则可以对日前处理的业务提供明确的延时上限，然而一般的固定树型算法对于无线信道的业务波动情况没有适应能力，例如树型分支固定，只能适合一定强度的到达业务，其他情况下会导致信道利用率下降和延时增加。本文针对随机访问信道协议，在固定树型算法的基础上，结合随机接续协议，给出了一种混合动态树型算法，目的是提高一般树型算法的信道利用率，保证延时指标的上限。