Reservation arbitrated access for statistical multiplexing voicetraffic over dual-bus metropolitan area networks

Metropolitan area networks (MANs) are well suited to serve as broadband multiplexers for asynchronous transfer mode (ATM) networks, to facilitate enterprise networking and to support future wireless personal communication systems. We propose and analyze a novel reservation arbitrated (RA) access method which provides isochronous voice transport over dual-bus MANs while enabling statistical multiplexing among voice calls. In combination with a new cyclic capturing (CC) mechanism, RA access allows stations to capture and reserve isochronous voice channels in a fair and distributive manner. This paper presents the RA access protocol, derives an analytical model for general waste-free voice reservation protocols, and analyzes the performance of RA access by computer simulations validated by analytical calculations. To assess the actual voice quality, simulation results based on a real voice signal are also presented. Results indicate that RA access offers significant improvements in channel utilization, as compared to prearbitrated (PA) access, while providing an acceptable quality of service. Therefore, RA access offers an efficient voice transport mechanism for existing switched multimegabit data service (SMDS) networks employing the IEEE 802.6 protocol, as well as emerging ATM/MAN-based broadband networks     

An architecture of ATM‐based PCS network: Signaling traffic and capacity

In this paper, we propose an ATM‐based Personal Communication Service (PCS) network architecture with ring‐based access networks. We also propose a simple ring management scheme using ATM Add‐Drop‐Multiplexers (ADM). The ring has a Virtual Star topology, and we manage its bandwidth at two levels: Virtual Path (VP) level and Virtual Channel (VC) level. We consider four different types of configurations according to the locations of visitor location register (VLR) and mobile switching center (MSC) functions, and obtain signaling load and processing load. A 150 Mb/s‐dual ring can support about 5,500 homogeneous ON–OFF voice sources. This ring capacity corresponds to covering approximately 180 cells in the case of 30 connections per cell. Even though we are here concerned with evaluating the proposed network for voice traffic, we can extend this study to the analysis of the proposed ATM‐based PCS network accommodating various types of multimedia traffic as a further study. This revised version was published online in August 2006 with corrections to the Cover Date.     

A signaling architecture for wireless ATM access networks

A multiservice wireless Asynchronous Transfer Mode (ATM) access system is considered from a signaling protocol viewpoint. In an attempt to generalize and extend results and experiences obtained from the specification, design, and implementation of fixed ATM‐based access networks, we extend the concept of the broadband V interface (referred to as VB) for application to wireless ATM access networks. The proposed architecture follows the signaling structure of Broadband ISDN (B‐ISDN) User–Network Interface (UNI), thus offering the possibility for integration of the wireless ATM access system into fixed B‐ISDN. It is shown that the use of the proposed access signaling architecture provides cost effective implementations without degrading the agreed Quality of Service (QoS), and simplifies call/connection and handover control. The evaluation of the proposed access signaling protocol structure yields results that fall within acceptable ATM signaling performance measures. A performance comparison of our approach with an alternative access signaling configuration is also carried out to quantify the relative gains. This revised version was published online in August 2006 with corrections to the Cover Date.     

LMDS/LMCS hub interconnection alternatives and multiple access issues

LMDS/LMCS is a broadband wireless local loop, millimeter‐wave alternative to emerging integrated multiservice access networks. Significantly large amounts of bandwidth – in the order of one GHz of spectrum – are made available to residential subscribers or supported business users respectively that employ highly directional antennas and signal polarization to establish communication with a central hub. Besides the requirement for dynamic bandwidth allocation capabilities, these networks should be able to guarantee negotiated quality of service (QoS) levels to a number of constant‐length (ATM) – and possibly variable length (TCP/IP) – packet streams. In this context, we analyze the performance of contention, polling/probing and piggybacking mechanisms that will be used by the LMDS MAC protocol for the dynamic support of both real‐time and non‐real‐time traffic streams. More specifically, we focus on the end‐to‐end performance of a real‐time variable bit rate connection for which the LMDS link is only the access component of a multi‐link path through an ATM network. Results are presented on maximum end‐to‐end cell delays under a Weighted Round Robin service discipline and buffer requirements are calculated for no‐loss conditions. In parallel, we also consider the case in which variable length IP packet traffic is supported as such by the same wireless access network. Backbone interconnection alternatives of LMDS hubs, multiple access proposals and scheduling algorithms are addressed in this framework. This revised version was published online in July 2006 with corrections to the Cover Date.     

Design and analysis of low‐power access protocols for wireless and mobile ATM networks

This paper describes the design and analysis of a low‐power medium access control (MAC) protocol for wireless/mobile ATM networks. The protocol – denoted EC‐MAC (energy conserving medium access control) – is designed to support different traffic types with quality‐of‐service (QoS) provisions. The network is based on the infrastructure model where a base station (BS) serves all the mobiles currently in its cell. A reservation‐based approach is proposed, with appropriate scheduling of the requests from the mobiles. This strategy is utilized to accomplish the dual goals of reduced energy consumption and quality of service provision over wireless links. A priority round robin with dynamic reservation update and error compensation scheduling algorithm is used to schedule the transmission requests of the mobiles. Discrete‐event simulation has been used to study the performance of the protocol. A comparison of energy consumption of the EC‐MAC to a number of other protocols is provided. This comparison indicates the EC‐MAC has, in general, better energy consumption characteristics. Performance analysis of the proposed protocol with respect to different quality‐of‐service parameters using video, audio and data traffic models is provided. This revised version was published online in August 2006 with corrections to the Cover Date.     

A spread‐slotted random‐access protocol with multi‐priority for personal and mobile communication networks carrying integrated traffic

This paper describes and analyzes a medium access protocol for wireless personal communication networks serving integrated traffic. A multipriority mechanism, which is implemented and controlled explicitly by the users and without any involvement from the network is incorporated into the protocol. We examine the proposed protocol under reservation and nonreservation policies and evaluate its performance when handling integrated voice and data traffic. The proposed protocol is suitable to be used in Personal Communication Systems aiming to provide integrated (voice/data) services.     

Integration of Mobile-IP and OLSR for a Universal Mobility

Trends in fourth generation (4G) wireless networks are clearly identified by the full-IP concept where all traffic (data, control, voice and video services, etc.) will be transported in IP packets. Many proposals are being made to enhance IP with the functionalities necessary to manage the mobility of nodes, so that networks can provide global seamless roaming between heterogeneous wireless and wired networks. In this paper, we focus on the management of universal mobility, including both large scale macro-mobility and local scale micro-mobility. We propose a hierachical architecture (i) extending micro-mobility management of a wireless access network to an ad-hoc access network, (ii) connecting this ad-hoc network to the Internet and (iii) integrating Mobile IP and OLSR, a routing protocol for ad-hoc networks, to manage universal mobility. This architecture is validated by an implementation based on DynamicsMobile-IP and OLSR version 7. We show how the brodcast of Mobile-IP Agent Advertisement can be optimized using OLSR MPR-flooding.     

Performance evaluation of integrated services interworking: The ATM-DQDB case

Performance studies on LAN/MAN-BISDN interworking have mainly focused on the requirements of isochronous and connectionless services. In this paper we extend performance results to cover also the case of non-isochronous connection oriented (CO) services supported by the queued arbitrated (QA) mode of access of the DQDB protocol. Using this case we stress the more general issue of service integration impact on the interworking unit (IWU) architecture design in terms of protocol stacks and expected performance. We herein evaluate the performance of IWU architectures tailored to relay information in the lowest possible layer while implementing several service priority schemes and buffer management policies towards QoS objectives. The conditions under which the IWU design is efficient regarding performance, protocol complexity and implementation cost in this integrated services environment are identified.     

A new ATM adaptation layer for TCP/IP over wireless ATM networks

This paper describes the design and performance of a new ATM adaptation layer protocol (AAL‐T) for improving TCP performance over wireless ATM networks. The wireless links are characterized by higher error rates and burstier error patterns in comparison with the fiber links for which ATM was introduced in the beginning. Since the low performance of TCP over wireless ATM networks is mainly due to the fact that TCP always responds to all packet losses by congestion control, the key idea in the design is to push the error control portion of TCP to the AAL layer so that TCP is only responsible for congestion control. The AAL‐T is based on a novel and reliable ARQ mechanism to support quality‐critical TCP traffic over wireless ATM networks. The proposed AAL protocol has been validated using the OPNET tool with the simulated wireless ATM network. The simulation results show that the AAL‐T provides higher throughput for TCP over wireless ATM networks compared to the existing approach of TCP with AAL 5. This revised version was published online in July 2006 with corrections to the Cover Date.     

A two-level stochastic approximation for admission control andbandwidth allocation

In an access node to a multiservice network [e.g., a base station in an integrated services cellular wireless network or the optical line terminal (OLT) in a broad-band passive optical network (PON)], the output link bandwidth is adaptively assigned to different users and dynamically shared between isochronous (guaranteed bandwidth) and asynchronous traffic types. The bandwidth allocation is effected by an admission controller, whose goal is to minimize the refusal rate of connection requests as well as the loss probability of cells queued in a finite buffer. Optimal admission control strategies are approximated by means of backpropagation feedforward neural networks, acting on the embedded Markov chain of the connection dynamics; the neural networks operate in conjunction with a higher level bandwidth allocation controller which performs a stochastic optimization algorithm. The case of unknown, slowly varying input rates is explicitly considered. Numerical results are presented that evaluate the approximation and the ability to adapt to parameter variations     

Wavelength division multiplexing-based video-on-demand systems

Serving video-on-demand (VOD) traffic via isochronous transmission service is highly desirable because of the characteristics of VOD traffic. This paper proposes a mechanism to transfer VOD traffic over wavelength division multiplexing (WDM) networks by employing isochronous transmission service. Based on the proposed mechanism, the problem of scheduling isochronous and asynchronous traffic for single-star WDM networks with multiple receivers and transmitters is investigated. The lower bounds on the total switching duration and the number of switching modes for the isochronous and asynchronous traffic scheduling problem are derived. An optimal scheduling algorithm is presented for the cases where only asynchronous traffic exists; and a heuristic algorithm is also proposed for the cases where both the isochronous and asynchronous traffic coexist in the WDM networks. Simulation results indicate that the average switching duration and the average number of switching modes obtained by the proposed algorithm are close to the lower bounds, which implies that the proposed scheduling algorithm is effective     

Distributed source control: a network access control for integratedbroadband packet networks

The authors propose a congestion control strategy called distributed source control (DSC), designed to address the integration of diverse traffic types in broadband packet networks. DSC is a rate-based network access control implemented at the asynchronous transfer mode (ATM) layer as a feedforward control, in conjunction with an adaptive end-to-end control between network edges. The authors examine the performance of high-speed data traffic such as large file transfers, still images, and document retrievals. The authors study DSC's integrability with real-time traffic such as voice and video. With the help of a simulation model of a broadband packet network (150 Mb/s), the authors quantify the improvement in network performance due to DSC. An analytic model for an access node under DSC is developed, and guidelines for sizing of buffers in the switch and for choosing the end-to-end window size are provided     

Mobile multicasting in wireless ATM networks

Multicasting is a desired function in both wired and wireless networks. Currently, multicasting‐based applications have pervasive presence and influence in our Internet. Wireless ATM aims to support different traffic types over a high speed wireless network. In particular, traditional approaches towards multicasting in wired networks cannot be directly applied to mobile ATM networks. This includes the mechanism proposed to handle mobility in wired networks. In this paper, we address the issues behind multicasting in wireless ATM networks and the underlying mechanisms to support handoffs of both unicast and multicast connections. Through simulation, we evaluated the performance of optimal core‐based tree (CBT), late‐joined CBT, optimal source‐based tree (SBT), and late‐joined SBT during changing multicast host membership conditions. In addition, we evaluated the impact of multicast receivers' migration on the total link cost of the resultant multicast tree. Simulation results revealed that source‐based trees incur more total link costs under both dynamic host membership and receivers' migration scenarios. However, it generates less control messages than the distributed CBT and SBT approaches. This revised version was published online in June 2006 with corrections to the Cover Date.     

A simulation tool to validate and compare satellite TDMA access schemes

This paper proposes an architecture design for a tool suitable for emulating DA‐TDMA (demand‐assignment‐time division multiple access) satellite access schemes. The tool presented, named FRACAS, is particularly suitable for comparing the performance of different satellite channel allocation policies. Using FRACAS, a service provider can choose from different policies for sharing a satellite channel among a number of users. Some allocation policies, selected from those available in the literature, are built‐in, while others can be designed from scratch and added without much effort. The parameters of the built‐in allocation policies can easily be changed in order to exploit the full potential of the allocation schemes. FRACAS's features permit the optimisation of satellite resource usage in accordance with the traffic pattern supported. FRACAS enables research teams and students to explore and compare different multiple access schemes, and to develop simulation runs for various kinds of service‐induced traffic, including aggregate traffic, which is typical in a local area network (LAN) interconnection environment. This revised version was published online in June 2006 with corrections to the Cover Date.     

An isochronous and asynchronous traffic scheduling algorithm fordual-star WDM networks

In this paper, based on the concept of wavelength reusing, a new architecture for interconnecting two wavelength division multiplexing (WDM) star networks is proposed. According to this architecture, the problem of scheduling isochronous as well as asynchronous traffic is investigated. The lower bounds for the problem of minimizing the switching duration and the number of switching modes are derived. A transmission scheduling algorithm for the proposed architecture to efficiently reuse the wavelength is also proposed. For only asynchronous traffic, the analytical result shows that the proposed scheduling algorithm produces solutions equal to the lower bounds. For both isochronous and asynchronous traffic, simulation results show that the average switching duration and the average number of switching modes obtained by the proposed algorithm are quite close to the lower bounds. Simulation results also show that given the same number of users and available wavelengths, the solutions (in terms of the average switching duration and the average number of switching modes) obtained by the proposed scheduling algorithm on the dual-star WDM networks are better than the solutions obtained by the two-phase algorithm on the similar dual-star WDM networks     

Cross-layer resource allocation for integrated Voice/Data traffic in wireless cellular networks

A major task in next-generation wireless cellular networks is provisioning of quality of service (QoS) over the bandwidth limited and error-prone wireless link. In this paper, we propose a cross-layer design scheme to provide QoS for voice and data traffic in wireless cellular networks with differentiated services (DiffServ) backbone. The scheme combines the transport layer protocols and link layer resource allocation to both guarantee the QoS requirements in the transport layer and achieve efficient resource utilization in the link layer. Optimal resource allocation problems for voice and data flows are formulated to guarantee pre-specified QoS with minimal required resources. For integrated voice/data traffic in a cell, a hybrid time-division/code-division medium access control (MAC) scheme is presented to achieve efficient multiplexing. Theoretical analysis and simulation results demonstrate the effectiveness of the proposed cross-layer approach.     

Optimal policies for handoff and channel assignment in networks of LEO satellites using CDMA

In this paper, we formulate the combined handoff and channel assignment problems in a CDMA LEO satellite network as a reward/cost optimization problem. The probabilistic properties of signals (channel fading as function of satellite elevation angle) and of the traffic in the footprints are used to formulate a finite‐horizon Markov decision process. The optimal policy is obtained by minimizing a cost function consisting of the weighted sum of the switching costs and blocking costs of traffics subject to a bit‐error‐rate or outage probability constraint. A backward induction algorithm is applied to derive the optimal policy. Performance of the optimal policy and the direct threshold policy are compared. This revised version was published online in June 2006 with corrections to the Cover Date.     

Call control and traffic transport for connection-oriented highspeed wireless personal communications over metropolitan area networks

A distributed circuit-switched approach for supporting the deployment of high speed wireless personal communication services in urban areas through the interconnection of base stations via metropolitan area networks (MANs) is proposed. Broadband MANs minimize traffic congestion by dynamic sharing of link capacity and by serving as distributed switches for partitioning call control functions. While the DQDB protocol readily supports distributed packet-switching over the IEEE 802.6 MAN, isochronous traffic such as voice and video is best supported by circuit-switched connections. The authors present an enhanced bi-state pre-arbitrated (PA) transport mechanism, and associated call control and handoff management techniques, which enable distributed circuit-switching over the MAN. These capabilities are not currently addressed in the 802.6 standards. The bi-state PA transport mechanism facilitates statistical multiplexing of variable rate isochronous traffic sources. The network capacity is constrained by the call setup delay performance, and is analyzed by simulations. Alternative signaling architectures, involving different placements of call control network elements, are evaluated. The effects of erasure nodes, and close bus versus open bus architectures, are considered. The overlap inter-MAN call setup procedure is proposed to reduce delays. Different call handoff procedures are formulated according to the type of handoff and the resulting change in call connectivity. Most handoffs are intra-MAN, requiring simple procedures with short delays     

A call admission control framework for voice over WLANs

In this article a call admission control framework is presented for voice over wireless local area networks (WLANs). The framework, called WLAN voice manager, manages admission control for voice over IP (VoIP) calls with WLANs as the access networks. WLAN voice manager interacts with WLAN medium access control (MAC) layer protocols, soft-switches (VoIP call agents), routers, and other network devices to perform end-to-end (ETE) quality of service (QoS) provisioning and control for VoIP calls originated from WLANs. By implementing the proposed WLAN voice manager in the WLAN access network, a two-level ETE VoIP QoS control mechanism can be achieved: level 1 QoS for voice traffic over WLAN medium access and level 2 QoS for ETE VoIP services in the networks with WLANs as the local access. The implementation challenges of this framework are discussed for both level 1 and level 2. Possible solutions to the implementation issues are proposed and other remaining open issues are also addressed.     

Air interface switching and performance analysis for fast vertical handoff in cellular network and WLAN interworking

The integration of wireless local area network (WLAN) hotspot and the 3G cellular networks is imminently the future mode of public access networks. One of the key elements for the successful integration is vertical handoff between the two heterogeneous networks. Service disruption may occur during the vertical handoff because of the IP layer handoff activities, such as registration, binding update, routing table update, etc. In this paper, the network interface switching and registration process are proposed for the integrated WLAN/cellular network. Two types of fast vertical handoff protocols based on bicasting and non‐bicasting supporting real‐time traffic, such as voice over IP, are modeled. The performance of a bicasting based handoff scheme is analyzed and compared with that of fast handoff without bicasting. Numerical results and the simulation are given to show that packet loss rate can be reduced by the bicasting during handoff scheme without increasing bandwidth on both wireless interfaces. Copyright © 2006 John Wiley & Sons, Ltd.