Wireless ATM Networks Research Articles

Transportation mobility management

Today, the world has observed a remarkable growth in the use of transportation mobile communications for road safety. While a user in a vehicle moves to a new communication cell, a wireless terminal requests a handoff for new channel in the new cell. Due to that movement, some of the challenges issues are developed such as, the increase in traffic volumes and demand for high speed transportation mobile communications call for fast, seamless and high performance handoff in mobile communications network. When a wireless user in a vehicle moves from one base station cell to another, handoff protocols reroute the existing active connections in the new transportation cell. The future challenges in next generation high speed transportation mobile networks are to minimize the packet loss and to provide efficient use of the network resources while maintaining quality of service assurances. Therefore, the performance of efficient management and a successful handoff operation in transportation mobile networks become an important issue for road safety traffic. This work shows analytical handoff management for transportation users in a high speed mobile communications network. We demonstrate the performance of handoffs with mobility consideration using several metrics including the alteration of states prior to reaching a transportation mobility cell boundary, the speed of transportation mobile terminal, and the distance between a transportation mobile terminal and a transportation cell boundary. We illustrate the performance evaluation for the factor of transportation mobility with taking into account the high speed status of a mobile vehicle user. Numerical results of the transportation performance analysis and the probability of requiring a handoff are demonstrated using Maple. Figure 1 shows a shaped region of a cellular network and the cellular handoff model with mobility. In this abstract, we modeled the cellular handoff for multimedia users with taking the high speed mobility into account in wireless mobile networks. The performance results in terms of state probabilities and the probability that a mobile terminal reached a cell boundary were investigated. The mobilized analysis involved with number of issues such as the alternation of states before a mobile unit reached a cell boundary, the distance between the mobile terminal and a cell boundary and the speed of the vehicle. Based on the assumption of the alternation of states, there were four situations for a vehicle to reach a cell boundary. Performance results were accurately analyzed based on these four situations. It was clearly showing that for a vehicle that experienced the change of states, the outcome chance of reaching a cell boundary was proportional to the distance in between the mobile terminal and a cell boundary and inversely propositional to the speed of the vehicle.

Routing Schemes for Wireless ATM Networks

In this paper, the Wireless ATM rerouting procedures are analyzed and categorized based on a standard network topology, derived from the Wireless ATM reference model. A new operational concept for a mobile ATM network called Mobile Network Architecture based on Virtual Paths (MNA VP), in which the network nodes are connected to each other via pre-established permanent virtual path connections with fixed capacity assignments is being proposed and described. Finally, the handover hysteresis concept is introduced and a hysteresis gain is defined and calculated as the factor by which the handover rate is reduced through the use of the hysteresis.

Rerouting Schemes for Wireless ATM Networks

In this paper, the Wireless ATM rerouting procedures are analyzed and categorized, based on a standard network topology, derived from the Wireless ATM reference model. A new operational concept for a mobile ATM network called Mobile Network Architecture based on Virtual Paths (MNAVP), in which the network nodes are connected to each other via pre-established permanent virtual path connections with fixed capacity assignments is being proposed and described. Finally, the handover hysteresis concept is introduced and a hysteresis gain is defined and calculated as the factor by which the handover rate is reduced through the use of the hysteresis.

Losses in Wireless ATM Networks

The standardized approach to Mobile ATM network handover is a hard backward or forward handover scheme with no guarantees for the integrity of the data stream. These handover functions are detailed in this paper and a more performant virtual connection handover protocol, using in-slot signaling techniques in order to facilitate loss less handover, is introduced. The QoS aspects related to this scheme are discussed and its OAM implementation is presented.

Performance Measures Of Wireless Protocols For Atm Networks

The concept of wireless ATM is now being actively considered as a potential framework for nextgeneration wireless communication networks capable of supporting integrated multimedia services with different QoS requirements. Several key subsystem design issues for wired ATM and wireless networks needs to be readdressed in the scope of the wireless ATM, which has the capability to extend the statistical multiplexing of wired ATM network into the wireless medium. One of the key subsystem issues is the development of appropriate medium access control (MAC) protocol. The extension of the ATM network into wireless environment faces many interesting problems. The original ATM network was designed for high speed, noiseless, and reliable channels. None of these characteristics are applicable to the wireless channel. One of the critical aspects of a wireless ATM network is the Medium or Multi Access Control (MAC) Protocol used by the Mobile station (MS) to request service from the BS, which has to consider the Quality of Service (QoS) of the specific applications. This paper analyses recently proposed MAC protocols, particularly those of Demand Assignment Multiple Access protocols using TDMA technique with Frequency Division Duplex (FDD). It also gives performance measures of two best suited protocols for wireless network environment Distributed Queuing Request Update Multiple Access (DQRUMA) protocol and Adaptive Request Channel Multiple Access (ARCMA) protocol.

On the effect of handover mechanisms on the performance of video communications in WATM networks

A handover mechanism defines the steps involved in the transfer of all information and resource allocation enabling a mobile terminal to remain connected to the wireless network infrastructure. A large number of handover mechanisms have been reported in the literature for Wireless ATM (WATM) networks. In this paper, we carry out a comprehensive QoS performance study of the handover mechanisms as proposed in the literature and a performance evaluation of various buffer management schemes used to compensate for service disruption caused during the handover phase.

HASP Overlay Cell Over Wireless ATM Microcellular Networks: A Proposed Architecture for Priority Subscribers

Wireless ATM (W-ATM) microcellular networks encounter severe problems during handovers. Microcellular solutions in W-ATM networks increase the network traffic control as a result of frequent handover requests. This paper presents a two-layer microcellular ATM architecture which optimizes the handoff blocking probability performance of priority subscribers (PS) in a congested urban area. The lower layer of the proposed architecture is based on a microcellular ATM solution for normal subscribers (NS) while the higher layer is based on a high altitude stratospheric platform (HASP) overlay solution for absorbing the traffic load of the existed handoff calls of PS. Analysis is performed using Markov state diagrams, in order to optimize the performance of W-ATM networks.

Different mac protocols for next generation wireless atm networks

Different mac protocols for next generation wireless atm networks

Layouts for mobility management in wireless ATM networks

In this paper, we present a new model that combines quality of service and mobility aspects in wireless ATM networks. Namely, besides the hop count and load parameters of the basic ATM layouts, we introduce a new notion of distance that estimates the time needed to reconstruct the virtual channel of a wireless user when he moves through the network. Quality of service guarantee dictates that the rerouting phase must be imperceptible, that is, the maximum distance between two virtual channels must be maintained as low as possible. Therefore, a natural combinatorial problem arises in which suitable trade-offs must be determined between the different performance measures. We first show that establishing the existence of a layout with maximum hop count h , load l and distance d is NP-complete, even in the very restricted case h = 2 , l = 1 and d = 1 . We then provide optimal layout constructions for basic interconnection networks, such as chains and rings.

Novel DLC model for QoS enhancement of bursty VBR traffic in wireless ATM networks

AbstractSeveral data‐link control (DLC) protocol procedures have been proposed in order to provide reliable data transmission over powerless radio links. However, many quality of service (QoS) issues still need to be achieved such as balance between cell transfer delay (CTD) and cell loss rate (CLR), absence of cell delay variation (CDV) and network traffic utilisation. The main problem with wireless ATM is how to overcome the unreliability of the wireless link in order to maintain QoS requirements especially for variable bit rate (VBR) application. Here, we propose a model that provides QoS support for ATM virtual connections (VC) and solves the unreliability problem of the wireless ATM through an efficient DLC protocol for bursty VBR traffic. This model mainly concerns with enhancing QoS to gain error‐free wireless transmission and regulating VBR Traffic. Copyright © 2008 John Wiley & Sons, Ltd.

The performance of TCP/IP over wireless ATM network

This paper investigates the most important packet discarding schemes that have been designed for best-effort traffic in wireless ATM and IP networks, and performs modeling and simulation work based on Early Packet Discarding using a Pair Buffer Allocation schemes on different traffic environments, including a mix of packets sizes, buffers sizes, diverse types of data and traffic flow models with the aim of establishing a framework for enhancing the performance of these schemes to improve the overall throughput of TCP/IP as a transport mechanism over wireless ATM networks. The simulation is carried out using MATLAB Simulink software. The simulation results show that a high effective throughput was obtained which is above 50% as compared with existing scheme which is lesser. The proposed scheme improves the effective throughput performance by reducing cell loss to a minimal level.

Handover Strategies Challenges in Wireless ATM Networks

Abstract— To support us er mobilityfor a wireless n twork newmechanisms are needed and are fundamental, such as paging, location updating, routing, and handover. Also an important key feature is mobile QoS offered by the WATM. Several ATM network protocols should be updated to implement mobility management and to maintain the already ATM QoS over wireless ATM networks. A survey of the various schemes and types of handover is provided. Handover procedure allows guarantee the terminal connection reestablishment when it moves between areas covered by different base stations. It is useful to satisfy user radio link transfer without interrupting a connection. However, failure to offer efficient solutions will result in handover important packet loss, severe delays and degradation of QoS offered to the applications. This paper reviews the requirements, characteristics and open issues of wireless ATM, particularly with regard to handover. It introduces key aspects of WATM and mobility extensions, which are added in the fixed ATM network. We propose a flexible approach for handover management that will minimize the QoS deterioration. Functional entities of this flexible approach are discussed in order to achieve minimum impact on the connection quality when a MT crosses the BS.

Evaluation of Handover Protocols in Wireless ATM Networks

Evaluation of Handover Protocols in Wireless ATM Networks

A Novel Centralized Flow Control Scheme for ABR Service in Wireless ATM Networks

In this paper, we propose a novel Centralized Flow Control Scheme (CFCS) for ABR service in WATM network. The goal is to provide Quality-of-Service (QoS) guarantee to the users and to reduce the computational complexity at switches. A novel concept of monitoring the network status in the centralized controller in the form of rate allocation tables for flow control is the main theme of our algorithm. CFCS operates in ATM switches placed in the backbone of WATM network. The Network Controller Switch (NCS) monitors the current status of VC and bandwidth availability as well as tracking the current number of active sessions contending for capacity, to adjust the explicit bound in the source transmission rates. The simulation results show that the scheme is stable and efficient in achieving maximum utilization of bandwidth occupancies, enhancing average throughput and achieving robustness under continuously varying network conditions. The simulation experiments also demonstrate the superiority of the proposed scheme to the other schemes in dealing with switch complexity.

Handover Optimization in Wireless Microcellular ATM Networks

Microcellular solutions in wireless ATM networks increase the network traffic control as a result of frequent handover requests. The blocking probability or the forced termination probability presents a quality of service criterion for evaluation of certain handover techniques. This paper presents a handover protocol that can avoid cell loss and guarantee cell sequence, and a two layer wireless call admission control is studied, using Markov state diagrams, in order to optimize the performance of wireless ATM networks.

Study on Traffic Shedding for Soft-Handoff Using MC-CDMA in Wireless ATM Networks

In wireless ATM mobile communication environments, an abrupt increase in the number of mobile users in a specific base station (BS) will overload the BS and turn it into a so-called hot-spot cell, which causes an unbalanced traffic load condition if the traffic load in the neighboring BSs is light. In order that efficiently allevates to utilize a limited bandwidth, it is necessary to use a good mobile handoff strategy to alleviate unbalanced traffic load condition. This paper proposes a complete traffic shedding algorithm (CTSA) for soft handoff efficiently to alleviate the overloaded traffic in a hot-spot cell by adjusting handoff parameters, which virtually reduces the service coverage of the heavy loaded BS without adjusting the transmission power. Mobile terminals (MT) located in the outer area of the hot-spot cell will be handed off early to the neighboring BSs with light traffic load; and MTs in the neighboring BSs will not be handed off to the hot-spot cell, so that the traffic load of the hot-spot cell can be decreased. After analyzing the proposed algorithm and comparing the other methods, variable threshold soft handoff (VTSH) and enhanced soft handoff (ESH), by simulation, the performance of CTSA is better than the others. CTSA obviously increases system throughput and decreases soft handoff call dropping ratio, new call blocking ratio, and total call refusing ratio.

A New Hybrid ARQ-FEC Scheme For Wireless ATM Networks

Wired ATM (Asynchronous Transfer Mode) networks are designed taking into account an optical link in the physical layer. The main problem to implement a wireless ATM network is the fact that its radio link bit error rate is high and variable, demanding the use of an additional error control mechanism. The usual techniques for error control are ARQ (Automatic Repeat Request) and FEC (Forward Error Correction). ARQ works better than FEC if the channel bit error rate is low, and is worse if it is high, thus indicating that hybrid ARQ-FEC techniques can improve the radio link performance. A new hybrid ARQ-FEC scheme with multiple FEC states is proposed in this paper. The performance of the proposed scheme is compared with non-adaptive ARQ and FEC schemes, which have similar complexities, and with an ideal adaptive FEC scheme. It is shown that the proposed scheme works better than the non-adaptive schemes, and that the hybrid and the ideal adaptive FEC schemes have similar performances. Moreover, the hybrid scheme does not require an estimate of the bit error rate in the channel, leading to a less complex implementation.

Controle de Erros em Redes ATM sem Fio

ATM networks have been designed considering the use of optical links in the physical layer, which present low bit error rate. The main problem in implementing wireless ATM networks is the high and variable bit error rate in the radio link. To overcome this problem, it is necessary to use an additional error control mechanism in the wireless link. The traditional techniques for error control are ARQ (Automatic Repeat Request) and FEC (Forward Error Correction). Using FEC or ARQ techniques in the wireless link decreases the residual bit error rate, increases the delay in transmitting a packet and decreases the throughput, due to overhead of the error control mechanisms. This paper presents a comparison of the performances of ARQ and FEC techniques in wireless ATM networks considering adaptive and non-adaptive systems and real-time and nonreal time applications. The criteria to compare the performances are: the delay to transmit a PDU (Protocol Data Unit), for real-time applications, and, for non-realtime applications, the throughput and the average and maximum cell transference delays.

Dynamic resource allocation for handoff using MC-CDMA in wireless ATM networks

Focusing on the characteristics of WATM networks based on multicarrier code-division multiple access technique, an improved optimised cell-scheduling algorithm and a dynamic resource allocation scheme with a resource compensation method to improve performance are proposed. Performance measurements are obtained by an analytical model and simulation experiments and compared for different schemes such as handoff call-dropping probability and new call-blocking probability. The results obtained by the proposed algorithms perform better than other algorithms.

Call-Admission-Control and Traffic- Policing Mechanisms for the Transmission of Videoconference Traffic From MPEG-4 and H.263 Video Coders in Wireless ATM Networks

In this paper, we explore, via an extensive simulation study, the performance of a call-admission-control (CAC) and traffic-policing mechanisms proposed for transmitting multiple quality encoded videoconference movies over a wireless asynchronous transfer mode channel of high capacity, depending on the user's needs and requests. Both the CAC algorithm and the traffic-policing mechanism are novel mechanisms proposed for the first time in this paper. For their implementation, we use an estimation of the equivalent bandwidth of the movies, which has been introduced in the past. We focus on both MPEG-4 and H.263 coded movies, as the integration of such video streams has not been studied in the relevant literature. In the case of H.263 movies, our scheme achieves high aggregate channel throughput, while preserving the very strict quality-of-service requirements of the video traffic.