Wireless ATM Networks Research Articles

Rerouting scheme with dynamic resource reservation in wireless ATM networks

A new handoff rerouting scheme with dynamic resource reservation in wireless ATM networks is proposed. The availability of network links is represented by normalised weight values and optimal paths are chosen based on those normalised weight values under the constraint of maximum allowable delay.

A New Scheme for Seamless Inter-Cluster Handoffs in Wireless ATM Networks

Many schemes to reduce the inter-cluster handoff delay in wireless ATM networks have been proposed, but the previous schemes waste relatively large network resources to decrease the path rerouting delay. In this paper, we propose the 2-layered cluster concept, where the seamless inter-cluster handoff can be supported regardless of path rerouting time. As a result, the waste of wired resources and the rate of the inter-cluster handoff can be reduced. From the performance analysis and simulation, the inter-cluster handoff rate for non-real-time traffic is only about 1/3 of the conventional result. Such advantageous features of the proposed scheme neither incur any increase of the total handoff rate nor require additional ATM switches.

Handovers in wireless ATM networks: in-band signaling protocols and performance analysis

The first part of this paper presents a novel scheme for handover provisioning in wireless asynchronous transfer mode (W-ATM) networks based on in-band signaling. First, the network architecture and principles of in-band signaling are described, discussing advantages and interaction with other procedures and signaling techniques. Then, loss-free protocols for the handover procedures are presented and compared with existing proposals. The second part of the paper is devoted to performance analysis of the handover procedures. A general methodology for evaluating handover delays and required buffer capacity is introduced and exemplified for one of the protocols introduced before. Numerical results give insight into the handover procedure characteristics and are compared with estimates provided by detailed discrete event simulations for validation purposes. Finally, additional simulation results are presented for parallel, concurrent handovers, evaluating the requirements posed to the network by different handover procedures.

Security issues for wireless ATM networks

To be able to fulfil the need of user in wireless ATM, the system has to acquire features. One of the system features for the wireless ATM is functionality especially the security aspect. There is so far tittle, if not none, security consideration in the developing of wireless ATM standard. Therefore a wide range of features in security functions is in consideration. This paper tried to define the features of security in wireless ATM networks considering it features from existing fixed ATM network and wireless network security provided. It does not attempt to define the cryptographic system, but rather provide a template in making cryptographic systems for those required features.

Extended performance evaluation of PRADOS: a scheduling algorithm for traffic integration in a wireless ATM network

The MAC protocol, known as MASCARA (Mobile Access Scheme based on Contention And Reservation for ATM), is an infrastructure-based, adaptive TDMA scheme, which combines reservation- and contention-based access methods to provide multiple access efficiency and Quality-of-Service (QoS) guarantees to wireless ATM terminal connections that share a common radio channel. Radio channel sharing is performed by the PRADOS (Prioritized Regulated Allocation Delay Oriented Scheduling) algorithm. In this paper we assess the capability of PRADOS to guarantee to voice and data traffic types the QoS they need. The analysis leads to the conclusion that PRADOS cannot avoid the interference between the various types of traffic. A criterion to alleviate this drawback is also outlined at the end of the paper.

ARCMA—adaptive request channel multiple access protocol for wireless ATM networks

AbstractWe propose a new multiple access protocol based on demand assignment. This protocol is designed to reduce contention in the request phase while minimizing transmission delay under various network (ATM) environments. Our protocol uses an adaptive scheme that changes under heavy traffic conditions, and also provides priority to certain delay‐sensitive traffic. Copyright © 2001 John Wiley & Sons, Ltd.

Mobility management and control in intelligent wireless ATM networks

This paper shows how the Asynchronous Transfer Mode (ATM) signaling and the Intelligent Network (IN) concept can be exploited to support mobility in an ATM-based network with wireless access parts and mobile users. The proposed architecture exploits the enhanced service control processing features offered by the IN technology to support location management. The access signaling protocol structure is based on the principles of separation between call and bearer channel control, employed in fixed broadband access networks. The design objective is to minimize the changes required to the wired network signaling, by taking advantage of the well-developed capability sets. This allows the easy introduction of the wireless ATM technology (W-ATM) into the real world. It is shown that the proposed signaling protocol model provides cost-effective implementations without degrading the agreed Quality of Service (QoS) and the system's performance. A comparative signaling performance evaluation is carried-out to demonstrate the impact of the proposed signaling protocol architecture onto various performance measures and to quantify the relative gains. The obtained results can be used for network design purposes in a large-scale private installation supporting many users. The signaling protocol architecture aims for private W-ATM networks, but can be readily extended to fulfill the signaling requirements of public environment broadband wireless systems.

High-speed PVC-based handover control in wireless ATM networks

Wireless ATM is expected to provide significantly high bit-rate services to meet the demand for handling multimedia information. In this paper, we propose a handover control scheme utilizing Permanent Virtual Connection (PVC) to reduce handover latency. Handover provisioning is an important function of the mobile wireless ATM network. The reestablishment-based schemes require a new partial path or a completely new connection to be set-up. This might result in being slow and inefficient. So the proposed scheme removes reestablishment procedure reserving PVCs between neighboring mobility enhanced ATM switches for handover. A simple analytical methodology is presented for overall system organization and for demonstrating the effectiveness of the proposed scheme.

A two‐phase combined QoS‐based handoff scheme in a wireless ATM network

AbstractWe describe the QoS‐based rerouting algorithm that is designed to implement a two‐phase inter‐switch handoff scheme for wireless ATM networks. We propose to use path extension for each inter‐switch handoff, and invoke path optimization when the handoff path exceeds the delay constraint or maximum path extension hops constraint. We study three types of path optimization schemes: combined QoS‐based, delay‐based and hop based path rerouting schemes. Copyright © 2001 John Wiley & Sons, Ltd.

On improving CBR service playback buffer mechanism in WATM networks

AbstractThe commonly recommended approach to meet the Constant Bit Rate (CBR) service requirements in ATM networks is to use the playback buffer mechanism implemented at the AAL layer [1],[2],[3]. This solution was originally proposed for the fibre optics ATM networks, where cell loss ratio is negligible (e. g. 10—9). However, for the wireless ATM network concept the designers have to take into account the fact that an essential part of sending cells can be simply lost due to transmission errors and these losses can also occur in bursts (despite applying error protection mechanisms). Moreover, the variation of cell transfer delay is expected to be significantly larger and this is mainly due to radio access protocol behaviour. As a consequence, the above leads to a need to modify the playback buffer mechanism in order to improve its functionality in the wireless ATM network environment. The solution proposed in this paper is based on some enhancements of the dummy cell insertion (instead of lost cells) algorithm and on the K times extension of AAL1 PDU numbering range, by assigning the same number to K consecutive cells. The justification of the approach is provided in terms of theoretical considerations and simulation results.

Performance models of handover protocols and buffering policies in mobile wireless ATM networks

Due to the connection-oriented nature of the asynchronous transfer mode (ATM), one of the challenges in mobile wireless ATM (WATM) systems is the management of terminal handovers. When ATM connections are reestablished to follow terminals moving between areas covered by distinct base stations, seamless handover protocols are necessary to guarantee that ATM cells are delivered to terminals in the correct order, with cell loss rate and delay that satisfy the contracted quality of service (QoS). A promising approach to meet QoS requirements is based on the use of handover buffers at the (destination) base station, where transmitted cells are stored while the connection is being reestablished. Up to date, only simulation and experimental results are available to determine the performance of such protocols and buffering schemes. This paper presents the first attempt to develop an analytical modeling approach to estimate the performance of handover protocols making use of handover buffers at the base station. By incorporating several approximations, the proposed models allow designers to simultaneously take into account numerous system parameters, including handover buffer size, sustainable and peak cell rates of the ATM connection, terminal offered load, and time needed to reestablish the ATM connection. Analytical performance predictions are shown to closely match results of detailed simulation experiments, thus demonstrating the suitability of the proposed modeling framework for the selection of the most adequate solution to handle handover and provide the QoS required by end users.

Stochastic control of path optimization for inter-switch handoffs in wireless ATM networks

One of the major design issues in wireless ATM networks is the support of inter-switch handoffs. An inter-switch handoff occurs when a mobile terminal moves to a new base station connecting to a different switch. Apart from resource allocation at the new base station, inter-switch handoff also requires connection rerouting. With the aim of minimizing the handoff delay while using the network resources efficiently, the two-phase handoff protocol uses path extension for each inter-switch handoff, followed by path optimization if necessary. The objective of this paper is to determine when and how often path optimization should be performed. The problem is formulated as a semi-Markov decision process. Link cost and signaling cost functions are introduced to capture the tradeoff between the network resources utilized by a connection and the signaling and processing load incurred on the network. The time between inter-switch handoffs follows a general distribution. A stationary optimal policy is obtained when the call termination time is exponentially distributed. Numerical results show significant improvement over four other heuristics.

Wireless ATM network architectures

AbstractEmulated LAN technology supports mobile hosts in wireless ATM networks. This paper introduces virtual LAN (VLAN) services using ATM LAN emulation technology which operates on a client/server model. One of the attractive features of the VLAN is the capability to group users into a broadcast domain. The focus of this paper is the issue of supporting quality of service to mobiles in a wireless ATM network. Copyright © 2001 John Wiley & Sons, Ltd.

A quantitative comparison of multiple access control protocols for wireless ATM

The multiple access control (MAC) problem in a wireless network has intrigued researchers for years. For a broad-band wireless network such as wireless ATM, an effective MAC protocol is very much desired because efficient allocation of channel bandwidth is imperative in accommodating a large user population with satisfactory quality of service. Indeed, MAC protocols for a wireless ATM network in which user traffic requirements are highly heterogeneous (classified into CBR, VBR, and ABR), are even more intricate to design. Considerable research efforts expended in tackling the problem have resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how time different protocols compare against each other on a unified basis. In this paper, we quantitatively compare seven previously proposed TDMA-based MAC protocols for integrated wireless data and voice services. We first propose a taxonomy of TDMA-based protocols, from which we carefully select seven protocols, namely SCAMA, DTDMA/VR, DTDMA/PR, DQRUMA, DPRMMA, DSA++, and PRMA/DA, such that they are devised based on rather orthogonal design philosophies. The objective of our comparison is to highlight the merits and demerits of different protocol designs.

A non-disruptive handoff protocol for wireless ATM networks

This paper presents a non-disruptive handoff protocol with dynamic channel reservation for wireless ATM networks. A mobile host (MH) in a wireless network is highly possible to travel from one radio cell to another radio cell. It is therefore very important to design an efficient handoff protocol for wireless ATM networks to re-establish ATM virtual circuit as soon as handoff request is initiated. In our protocol design, an MH sends a handoff request to its original basestation (BS), which in turn forwards this request to its control function. One of the innovative designs of this protocol is to perform non-disruptive handoff with dynamic channel reservation over ATM virtual circuit, regardless of which radio cell the MH is moving to. For the purpose of evaluation, a three-dimensional Marcov chain is built to analyze the handoff blocking probability with and without dynamic channel reservation. The analytical results are verified by a simulation study, which has shown that a non-disruptive handoff with dynamic channel reservation does achieve much lower blocking probability under high traffic load and significantly reduce the average waiting time during handoff.

An adaptive QoS guaranteeing MAC protocol for real-time traffic in TDMA-based wireless ATM networks

This paper presents a new media access control (MAC) protocol based on forward error control (FEC), which is appropriate for supporting real-time traffic with strict QoS requirements in wireless ATM networks. As the channel BER in wireless environments is very high and varying 10 −5–10 −2, previous schemes that use powerful FEC have combated to overcome this noisy channel condition at the cost of valuable bandwidth. As most previous works have been dedicated to maximize the channel efficiency, they were not able to meet QoS requirements of real-time applications in wireless networks. A new MAC protocol proposed in this paper is designed to guarantee the throughput requested by a real-time traffic user while keeping the bandwidth consumption at a minimum. The proposed scheme is for a TDMA system and uses adaptive FEC. We analyze the wireless channel and model it as a two-state error control system to design an efficient MAC protocol. We use simulation experiments to show how the proposed scheme provides QoS guarantees, and compare it with the CDMA system in terms of capacity, i.e. the number of users that can be supported.

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.

An adaptive reservation scheme for VBR voice traffic in wireless ATM networks

A reservation scheme, named dynamic hybrid partitioning, is proposed for the Medium Access Control (MAC) protocol of wireless ATM (WATM) networks operating in Time Division Duplex (TDD) mode. The goal is to improve the performance of the real-time Variable Bit Rate (VBR) voice traffic in networks with mixed voice/data traffic. In most proposed MAC protocols for WATM networks, the reservation phase treats all traffic equally, whether delay-sensitive or not. Hence, delay-sensitive VBR traffic sources have to compete for reservation each time they wake up from idle mode. This causes large and variable channel access delays, and increases the delay and delay variation (jitter) experienced by ATM cells of VBR traffic. In the proposed scheme, the reservation phase of the MAC protocol is dynamically divided into a contention-free partition for delay-sensitive idle VBR traffic, and a contention partition for other traffic. Adaptive algorithms dynamically adjust the partition sizes to minimize the channel bandwidth overhead. Simulation results show that the delay performance of delay-sensitive VBR traffic is improved while minimizing the overhead.

An adaptive FEC scheme for data traffic in wireless ATM networks

In this paper, a new adaptive forward-error-correction scheme (AFEC) is introduced at the link layer for TCP/IP data traffic in wireless ATM networks. The fading and interference in wireless links cause high and variable error rates, as well as bursty errors. The purpose of the AFEC scheme is to provide a dynamic error-control mechanism by using the Reed-Solomon coding to protect the ATM cell payload, as well as the payload type indicator/cell loss priority fields in the ATM cell header. In order to enhance the error tolerance in cell framing and correct delivery, the AFEC scheme functions within a new concept called LANET framing and addressing protection mechanisms. The AFEC scheme has been validated using a simulation testbed of a low-speed wireless ATM network.

Integration of Video and Data Bursty Traffics in Wireless ATM Networks

Future wireless systems will allow a mobile access to Asynchronous Transfer Mode (ATM) networks. Towards this end, one of the main problems is the management of different traffics, each of them having specific Quality of Service (QoS) requirements. This paper proposes a novel Medium Access Control (MAC) protocol coordinated by a controller at the access point. In particular, a polling technique is considered to enable cyclically the transmissions of different terminals. The maximum number of packets that each source can send at each cycle is regulated by a token bucket scheme. We have considered the joint management of real time-Variable Bit Rate (rt-VBR) traffics and bursty Available Bit Rate (ABR) traffics. The controller estimates the congestion of the rt-VBR buffers and accordingly adapts the cycle order. The obtained MAC scheme, called Adaptive Token Bucket – priority based Round Robin (ATB-RR), has permitted to achieve satisfactory QoS levels for both rt-VBR and ABR traffics also in the presence of a scenario with mixed real-time sources.