A bandwidth allocation/sharing/extension protocol for multimediaover IEEE 802.11 ad hoc wireless LANs

We propose a novel bandwidth allocation/sharing/extension (DBASE) protocol to support both asynchronous traffic and multimedia traffic with the characteristics of variable bit rate (VBR) and constant bit rate (CBR) over IEEE 802.11 ad hoc wireless local area networks. The overall quality of service (QoS) will be guaranteed by DBASE. The designed DBASE protocol will reserve bandwidth for real-time stations based on a fair and efficient allocation. Besides, the proposed DBASE is still compliant with the IEEE 802.11 standard. The performance of DBASE is evaluated by analysis and simulations. Simulations show that the DBASE is able to provide almost 90% channel utilization and low packet loss due to delay expiry for real-time multimedia services     

Mobility Management for VoIP on Heterogeneous Networks: Evaluation of Adaptive Schemes

The introduction of the IP multimedia subsystem on 3G cellular networks and the integration with other widely deployed wireless networks based on the IEEE 802.11 protocol family require support for both mobility and quality of service. When mobile systems move across heterogeneous networks, ongoing real-time sessions are affected not only by handoff delay but also by different packet delay and bit rate. In this paper, we propose a cross-layer mechanism that takes into account mobility at different layers of the network stack in order to yield better quality for VoIP, videoconferencing, and other real-time applications. We describe our cross-layer architecture, adaptation techniques, a prototype implementation, and experimental results.     

QoS Performance Bounds and Efficient Connection Admission Control for Heterogeneous Services in Wireless Cellular Networks

Quality-of-Service (QoS) performance and connection admission control (CAC) for heterogeneous services in wireless multiple access networks are investigated. The heterogeneous services include constant bit rate (CBR), variable bit rate (VBR) and available bit rate (ABR) services. Multiple access control is handled by a polling-based scheme with non-preemptive priority. Tight delay variation (jitter) bounds for CBR connections and delay bounds for VBR connections are derived. A CAC scheme based on the derived bounds is developed. The CAC makes use of user mobility information to reserve an appropriate amount of system resources for potential handoff connections to achieve low handoff connection dropping rate (HCDR). Simulation results show that the proposed CAC scheme can achieve both low HCDR and high resource utilization.     

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.     

一种无线ATM网络的MAC协议

主要研究了无线ATM网络对MAC的需求，并介绍了适用于无线ATM的一种新的MAC方案。该协议支持不同类型信息传输，比如恒定比特率（CBR），可变比特率（VBR），可用比特率（ABR），未指定比特率（UBR）。另外此协议还提供了对宽带ATM主干网的无缝连接。同时也支持与ATM相关的QoS级别。对于该协议关注的各种情况的主要原理进行了讨论。     

The Analysis of System Capacity of VoIP System Supporting CBRand VBR Traffic in IEEE802.11b WLAN Under DCF Mode

1IntroductionVoIP over IEEE802 .11[1]WLANis supposedto be-come an i mportant application. The IEEE 802 .11 hastwo different channel accessing mechanisms , namely,the DCFand Point Coordination Function (PCF) .DCFis based onthe Carrier Sense Multiple Access with Colli-sion Avoidance (CSMA/CA) channel accessing mecha-nism, while PCF is based on the polling technique .Here we only consider that the wireless networks oper-ate using the DCF MAC protocol ( without theRTS/CTS mech…     

Seamless SIP-based mobility for multimedia applications

Application-level protocol abstraction is required to support seamless mobility in next-generation heterogeneous wireless networks. Session initiation protocol (SIP) provides the required abstraction for mobility support for multimedia applications in such networks. However, the handoff procedure with SIP suffers from undesirable delay and hence packet loss in some cases, which is detrimental to applications like voice over IP (VoIP) or streaming video that demand stringent quality of service (QoS) requirements. In this article we present a SIP-based architecture that supports soft handoff for IP-centric wireless networks. Soft handoff ensures that there is no packet loss and that the end-to-end delay jitter is kept under control.     

Dynamic reservation TDMA protocol for wireless ATM networks

A dynamic reservation time division multiple access (DR-TDMA) control protocol that extends the capabilities of asynchronous transfer mode (ATM) networks over the wireless channel is proposed in this paper. DR-TDMA combines the advantages of distributed access and centralized control for transporting constant bit rate (CBR), variable bit rate (VBR), and available bit rate (ABR) traffic efficiently over a wireless channel. The contention slots access for reservation requests is governed by the framed pseudo-Bayesian priority (FPBP) Aloha protocol that provides different access priorities to the control packets in order to improve the quality-of-service (QoS) offered to time sensitive connections. DR-TDMA also features a novel integrated resource allocation algorithm that efficiently schedules terminals' reserved access to the wireless ATM channel by considering their requested bandwidth and QoS. Integration of CBR, voice, VBR, data, and control traffic over the wireless ATM channel using the proposed DR-TDMA protocol is considered in this paper. Simulation results are presented to show that the protocol respects the required QoS of each traffic category while providing a highly efficient utilization of approximately 96% for the wireless ATM channel     

Design and evaluation of an efficient traffic control scheme for integrated voice,video, and data over asynchronous transfer mode networks: Explicit allowed rate algorithm

Asychronous transfer mode (ATM) networks are high‐speed networks with guaranteed quality of service. The main cause of congestion in ATM networks is over utilization of physical bandwidth. Unlike constant bit‐rate (CBR) traffic, the bandwidth reserved by variable bit‐rate (VBR) traffic is not fully utilized at all instances. Hence, this unused bandwidth is allocated to available bit‐rate (ABR) traffic. As the bandwidth used by VBR traffic changes, available bandwidth for ABR traffic varies; i.e., available bandwidth for ABR traffic is inversely proportional to the bandwidth used by the VBR traffic. Based on this fact, a rate‐based congestion control algorithm, Explicit Allowed Rate Algorithm (EARA), is presented in this paper. EARA is compared with Proportional Rate Control Algorithm (PRCA) and Explicit Rate Indication Congestion Avoidance Algorithm (ERICA), in both LAN and WAN environments. Simulations of all three algorithms are conducted under both congestion and fairness configurations with simultaneous generation of CBR, rt‐VBR, nrt‐VBR and ABR traffic. The results show that, with very small over‐head on the switch, EARA significantly decreases the required buffer space and improves the network throughput. Copyright © 1999 John Wiley & Sons, Ltd.     

突发业务下的移动自组织网DSR协议仿真性能分析

移动自组织网络是一组由移动节点组成的无线网络。它的性能已经被广泛的进行了研究,但是这些研究主要是针对节点的移动性和网络的规模来展开的。近年来,移动自组织网在传输视频、音频、数据、图像等多媒体上的应用越来越多,因此自组织网在传输不同业务模型时的性能分析也引起了人们的广泛关注。本文中,我们主要研究分析了移动自组织网DSR协议在传输VBR业务时的性能,并且将仿真结果和传输CBR业务时的结果进行了比较。通过进一步的分析,我们得出与传输VBR业务相比,在传输CBR业务时,移动自组织网DSR协议性能明显提高。     

Flexible optical fiber CDMA networks using strict opticalorthogonal codes for multimedia broadcasting and distributionapplications

Flexible optical fiber code-division multiple-access (CDMA) networks are proposed to support real-time multimedia communication services of constant bit rate (CBR) and variable bit rate (VBR)/multiple bit rate (MBR). Since strict optical orthogonal codes (OOCs) are employed in incoherent optical fiber CDMA networks, their use can strictly guarantee the correlation constraint λ to be the minimum value (i.e., an unit “1”) for multimedia applications. This is achieved without increasing any system complexity compared with the use of conventional OOCs. Moreover, optimal strict OOCs can have the same length as optimal conventional OOCs or a slightly longer length than the latter. It is shown that the proposed optical fiber CDMA networks have a distinguishing feature of high bit-rate flexibility and fast access tunability. Consequently, this can effectively support both VBR and CBR video communications as well as multimedia broadcasting/distributions in a given network without any violation of the minimum correlation constraint λ=1. The proposed network can be also used as a backbone to interconnect various local-area networks with different data bit rates. However, conventional OOC-based optical CDMA networks do not possess such characteristics because of violation of λ=1 for VBR or MBR communications     

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.     

Mobility management architectures based on joint mobile IP and SIP protocols

In the all-IP wireless networks beyond the third generation, mobility management can be effectively achieved by applying mobile IP (MIP) and the session initiation protocol (SIP) jointly. Nevertheless, an efficient combination of both protocols remains an open research issue. Conventional hybrid MIP-SIP mobility architectures operate MIP and SIP almost independently, resulting in significant redundant costs. This article investigates the representative hybrid MIP-SIP architectures and explores the joint optimizations between MIP and SIP for a more cost-efficient mobility support whilst utilizing their complementary power. Two novel design approaches are presented. The first approach culminates in a tightly integrated architecture, which merges the redundant mobility entities in MIP and SIP to yield maximum system efficiency. The other approach leads to a loosely integrated architecture, where necessary interactions are introduced between MIP and SIP mobility servers while their physical entities are kept intact. Major mobility procedures, including location update, session setup and handoff, are discussed in these architectures. The analytical results demonstrate that both proposed architectures outperform typical hybrid MIP-SIP architectures in terms of clear-cut reduced signaling costs     

SIP mediated services

In this paper we discuss how we can use the session initiation protocol (SIP) to offer advanced services for mobile users over BT’s 21st Century Network (21CN). We provide a brief overview of the advantages of using SIP and describe how SIP can play a vital role in today’s and future heterogeneous networks, such as BT’s 21CN. We demonstrate some advantages of using SIP for handover in these varied networks and we compare it against using other methods for handover, e.g. mobile IP. With the current and anticipated demand for users with multiple devices, we introduce the benefits of using SIP for personal mobility, including the concept of transferring sessions between a user’s many and varied devices. We then consider quality of service issues that present themselves when moving frequently between varied, particularly wireless, networks with varying capabilities and congestion. We describe how we have used codec switching to cope with these adverse conditions, and consider the benefits of shifting the control of this adaptation to the network. This work centres on a custom-built test-bed together with our own real-time SIP-based videoconferencing application with codec switching capability. We present this test-bed, and results based on its use.     

Supporting service differentiation for real-time and best-effort traffic in stateless wireless ad hoc networks (SWAN)

We propose SWAN, a stateless network model which uses distributed control algorithms to deliver service differentiation in mobile wireless ad hoc networks in a simple, scalable and robust manner. The proposed architecture is designed to handle both real-time UDP traffic, and best effort UDP and TCP traffic without the need for the introduction and management of per-flow state information in the network. SWAN supports per-hop and end-to-end control algorithms that primarily rely on the efficient operation of TC/IP protocols. In particular, SWAN uses local rate control for best-effort traffic, and sender-based admission control for real-time UDP traffic. Explicit congestion notification (ECN) is used to dynamically regulate admitted real-time sessions in the face of network dynamics brought on by mobility or traffic overload conditions. SWAN does not require the support of a QoS-capable MAC to deliver service differentiation. Rather, real-time services are built using existing best effort wireless MAC technology. Simulation, analysis, and results from an experimental wireless testbed show that real-time applications experience low and stable delays under various multihop, traffic, and mobility conditions.     

Providing deterministic packet delays and packet losses in multimedia wireless networks

‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment. Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees. In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay. We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.     

IP multimedia services: analysis of mobile IP and SIP interactions in 3G networks

Third-generation cellular networks have been designed to provide a variety of IP data services. Both IPv4 and IPv6 are supported in order to provide future-proof solutions. Mobility is supported through both cellular-specific and IP mechanisms. Mobile IP is becoming a key technology for managing mobility wireless networks. At the same time, the session initiation protocol is the key to realizing and provisioning services in IP-based cellular networks. The need for mobility of future real-time service independent of terminal mobility requires SIP to seamlessly interwork with mobile IP operations. In this article, we investigate the issues related to interworking between SIP and mobile IP, with a focus on IPv6 and the applicability to 3G networks being standardized in 3GPP and 3GPP2.     

SIP-based vertical handoff between WWANs and WLANs

Future-generation wireless networks have been envisioned as the integration of various wireless access networks, including both wireless wide area networks and wireless local area networks. In such a heterogeneous network environment, seamless mobility support is the basis of providing uninterrupted wireless services to mobile users roaming between various wireless access networks. Because of transparency to lower-layer characteristics, ease of deployment, and greater scalability, the application-layer-based session initiation protocol has been considered the right candidate for handling mobility in heterogeneous wireless networks. However, SIP entails application-layer transport and processing of messages, which may introduce considerable delay. As a case study of the performance of mobility management protocols in the heterogeneous wireless networks, we analyze the delay associated with vertical handoff using SIP in the WLAN-UMTS internetwork. Analytical results show that WLAN-to-UMTS handoff incurs unacceptable delay for supporting real-time multimedia services, and is mainly due to transmission of SIP signaling messages over erroneous and bandwidth-limited wireless links. On the other hand, UMTS-to-WLAN handoff experiences much less delay, mainly contributed by the processing delay of signaling messages at the WLAN gateways and servers. While the former case requires the deployment of soft handoff techniques to reduce the delay, faster servers and more efficient host configuration mechanisms can do the job in the latter case.     

Efficient Traffic Scheduling for Real Time VBR MPEG Video Transmission Over DOCSIS-Based HFC Networks

Data-over-cable service interface specifications (DOCSIS), the de facto standard in the cable industry, defines a scheduling service called real-time polling service (rtPS) to provision quality of service (QoS) transmission of real-time variable bit rate (VBR) videos. However, the rtPS service intrinsically has high latency, which makes it not applicable to real-time traffic transport. In this paper, we present a novel traffic scheduling algorithm for hybrid fiber coax (HFC) networks based on DOCSIS that aims to provide QoS for real-time VBR video transmissions. The novel characteristics of this algorithm, as compared to those described in published literatures, include 1) it predicts the bandwidth requirements for future traffic using a novel traffic predictor designed to provide simple yet accurate online prediction; and 2) it takes the attributes of physical (PHY) layer, media access control (MAC) layer and application layer into consideration. In addition, the proposed traffic scheduling algorithm is completely compatible with the DOCSIS specification and does not require any protocol changes. We analyze the performance of the proposed traffic predictor and traffic scheduling algorithm using real-life MPEG video traces. Simulation results indicate that 1) the proposed traffic predictor significantly outperforms previously published techniques with respect to the prediction error and 2) Compared with several existing scheduling algorithms, the proposed traffic scheduling algorithm surpasses other mechanisms in terms of channel utilization, buffer usage, packet delay, and packet loss rate.     

A multiple access scheme for multimedia traffic in wireless ATM

This paper proposes a multiple access scheme for the forthcoming wireless ATM (Asynchronous Transfer Mode) system. Such ATM compatible wireless systems are motivated by the rapidly increasing demand for wireless extensions to broadband networks, which are expected to support mixed broadband services including Constant Bit Rate (CBR), Variable Bit Rate (VBR), and Available Bit Rate (ABR) traffic. Since these different traffics have very different performance requirements, the multiple access scheme design is very challenging. In this paper, we propose a multiple access scheme called Dynamic Time Division Multiple Access with Piggybacked Reservation (DTDMA/PR), attempting to achieve higher statistical multiplexing efficiency in the mixed VBR/CBR/ABR traffic scenario. The basic idea is to exploit two levels of reservation. The first level deals with the isochronous nature of CBR and VBR traffic and the bursty nature of ABR traffic by using the ALOHA reservation procedure. The second level exploits the piggybacked reservation approach to cope with the dynamic feature of VBR traffic in order to increase the multiplexing efficiency. An analytical model is also developed in this paper and verified by simulation. Numerical examples are given to gain some insight into the protocol itself.