Wireless ATM Networks Research Articles

Characterization of adaptive modulators in fixed wireless ATM networks

The various challenges to realize a fixed wireless ATM network are discussed and some solutions for these challenges are presented. In this paper, the capacity allocation in wireless ATM, the wireless link impact on ATM traffic, and the optimum utilization of the wireless network resources for a line of sight (LOS) wireless ATM link are studied. An adaptive MQAM modulator is introduced to provide a suitable solution to these issues. The modulator level is adjusted using a unique QoS metric in a wireless network. The metric, termed modified effective bandwidth, takes into account the bandwidth demand, QoS requirements, and outage conditions of the wireless ATM link. A performance study using VBR MPEG-1 video traffic in a fixed wireless channel (Ricean channel) demonstrates the advantages of the proposed system.

Centralized transmission probability control scheme for non-real-time traffic in wireless ATM networks

This article proposes a contention-based reservation medium access control protocol for transporting bursty traffic efficiently in wireless ATM networks. The proposed protocol is characterized by a contention-based transmission of the reservation request and a contention-free transmission of the bursty traffic. The design objective of the proposed protocol is to reduce the contention delay while maximizing the channel utilization. In order to reduce the collision of reservation request packets, the base station calculates and broadcasts the transmission permission probability of reservation request packets. The calculation of the transmission permission probability is based on the estimated load of reservation requests and the number of random access minislots. The wireless terminal, which has a bursty traffic, selects a random access minislot and transmits its reservation request packet with the received transmission permission probability. Based on the successfully received reservation packets, the scheduler allocates the uplink data slots to the wireless terminal. Simulation results are presented to show that the proposed protocol provides high channel utilization, and furthermore, maintains a constant delay performance in a heavy traffic environment.

Provisioning multicast QoS for WDM-based optical wireless networks

Wavelength division multiplexing (WDM)-based optical technique is becoming the right choice for the next-generation Internet infrastructure to transport high-speed Internet Protocol traffic. Today, wireless asynchronous transfer mode (WATM) network plays the leading role; undoubtedly it will be replaced with wireless WDM (WWDM) network to provide higher quality of service for mobile users. In addition many conventional and emerging applications, such as teleconferencing and distributed games, require multicasting increasingly. Many efforts to support multicasting for WATM networks have been offered, yet there are rarely addressed on WWDM networks. Moreover, conventional operations to set up and tear down optical connections in WDM networks are unable to apply directly to WWDM networks. User's mobility may make the operating optical-multicast-tree to change into very inefficient. The tree may expand and consume excessive resources, and even lost connection due to violating the associated QoS constraints. In this paper, a Constrained Optical Tree Migration Scheme (COTMS) is proposed to support real-time multicast services for WWDM networks. COTMS efficiently deals with the constrained tree migration problem and adapts easily to the operations of WDM. Simulation results reveal that COTMS can markedly reduce the resources used by per optical tree, thus achieving both low handoff-dropping/join-blocking rate and high-resource utilization. Moreover, COTMS is also suitable for ad-hoc networks with multiple different frequencies for multicast routing.

Link-Level Traffic Scheduling for Providing Predictive QoS in Wireless Multimedia Networks

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes are evaluated by computer simulation for realistic voice, video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme, Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.

A location management scheme to provide IP mobility over wireless ATM

Increasing user demand for more bandwidth over wireless communications has motivated a new challenge to utilize benefits of wireless ATM technology. This paper focuses on how to provide IP services to a mobile user over wireless ATM networks. By enhancing the NHRP standard, we improve several shortcomings that are resulted from the naı̈ve combinations of mobile IP over ATM or IP over wireless ATM. This paper presents a mobile location management algorithm that is referred to as the mobile NHRP scheme. The performance analysis is given by formulating equations for costs. We estimate the total costs per move and per setup over ATM/IP overlaid networks.

Multimedia call admission control in mobile networks: a dynamical reservation-pool approach

The effective delivery of Multimedia traffic in next generation mobile cellular communication environment will become an increasingly important issue as cell sizes shrink to accommodate continuously large demand for high capacity. To provide the guaranteed mobile QoS for arriving multi-class calls, we should not only consider the regular latency requirement, but also minimize the dropping rate of handoff calls while at the same time controlling the blocking rate of new calls. In this paper, a new multi-class call admission control mechanism is proposed that is based on dynamically forming a reservation-pool for handoff requests. The prerequisite of this scheme is that wireless components can estimate future trajectory of mobile hosts with high degree of accuracy, which is possible in today’s increasingly improved position location techniques such as GPS. In this work, we first develop the notion of servicing various multi-class connections based on priority determined using the combined analysis of mobile movement information and the desired QoS requirements of multimedia traffic. We also provide a practical framework for determining the occurrence time of handoff request reservations. For our simulation experiments, three kinds of timers are introduced for controlling the progress of discrete events. The simulation results show that the individual QoS criteria of multi-class traffic such as the handoff call dropping probability can be achieved within a targeted objective and the new call blocking probability is constrained to be below a given level. The proposed scheme is applicable to channel allocation of multi-class calls over high-speed multimedia wireless ATM networks.

Performance of a hybrid multilevel error control with an early-stop ARQ protocol for wireless ATM networks

This paper proposes an effective hybrid multilevel error control (HMEC) with an early-stop automatic repeat request (ARQ) scheme for wireless asynchronous transfer mode (ATM) networks. In this scheme, the source traffic is segmented into a number of blocks, each with m cells, then encoded into k(k>m) cells. The transmission of one block may be finished as long as m out of the k cells are received correctly. The ARQ protocol is applied only when too many cells are dropped or corrupted due to uncorrectable error in the radio channel. This paper also provides a detail study of the proposed scheme. In particular, the throughput efficiency with parameters (m,k) are derived analytically for the white Gaussian and Rayleigh fading channels. Simulation results show a very close match with theoretical results. All the results show that the HMEC scheme can reduce cell-retransmission probability and improve network throughput over a wide range of channel error rates when appropriate values of parameters m and k are chosen.

Performance evaluation of ABR flow-control protocols in a wireless ATM network

Using an object-oriented simulation model of a basic client-server scenario in a wireless ATM network, we study the impact of handover and error-control protocols on the performance of high-speed data communication by the ABR service class. We present performance results of the ABR flow-control protocols ERICA and ERICA+ and discuss some implications for the protocol design.

A wireless atm mac protocol with combined hybrid arq and adaptive scheduling with analysis

A combined hybrid automatic repeat request (ARQ) error control and adaptive scheduling scheme is proposed for time-division multiple access/time-division duplex medium access control (MAC) protocols in wireless asynchronous transfer mode (ATM) networks. Specifically, with the aid of proper channel modeling, the performance of various error-control schemes is evaluated. Accordingly, type-II hybrid ARQ is chosen as the error recovery scheme to combat fading effects, while adaptive fair-queueing is designed to achieve a fair and efficient resource allocation in wireless channels. In particular, the weight of a connection used in the fair-queueing algorithm dynamically adapts in terms of varying channel conditions and the types of services. Various simulations are conducted in typical indoor wireless ATM networks. It is shown that the proposed scheme can achieve a high throughput and transfer reliability with minimized delay and cell loss rate when compared with the conventional MAC layer control.

Hardware/Software Co-Design of Complex Embedded Systems: An Approach Using Efficient Process Models, Multiple Formalism Specification and Validation via Co-Simulation

This paper presents a hardware/software co-design approachwhere different specification languages can be used in parallel, allowingeffective system co-modeling. The proposed methodology introduces a processmodel that extends the traditional spiral model so as to reflect the designneeds of modern embedded systems. The methodology is supported by an advancedtoolset that allows co-modeling and co-simulation using SDL, Statecharts andMATRIXX, and interactive hardware/software partitioning. The effectivenessof the proposed approach is exhibited through two applicati on examples: thedesign of a car window lift mechanism, and the design of a MAC layer protocolfor wireless ATM networks.

A distributed multicast tree using share link migration scheme for wireless asynchronous transfer mode network

In recent years, wireless asynchronous transfer mode networks have become popular and are in widespread use for supporting various types of data transmission. To minimize the cost in setting up routes and to meet the QoS constraint in time-sensitive traffic, in addition to bandwidth capacity, this paper focuses on the optimization of the number of shared links to reduce the call-blocking rate and the handoff failure rate for intercell roaming. The average longest path length and the average of the average path length of the constructed multicast trees are shown to be stable when the network load becomes heavy.

DRA: a new buffer management scheme for wireless atm networks using aggregative large deviation principle

In this paper, we present a buffer management scheme called Dynamic Resource Allocation (DRA) that provides TCP traffic control guarantees to VCs carrying multiple dynamic discard thresholds (Multiple Dynamic Thresholds—MDT) over a wireless CDMA ATM network. It is assumed that we have TCP wireless ATM networks integrating the Code Division Multiple Access (CDMA). A major task activity related to these systems addresses the call admission control and resource management The MDT scheme classifies the traffic into several classes and maintains a separate dynamic threshold buffer for each class. DRA is used on a FIFO buffer shared by several VCs. Each VC can carry traffic from one or more TCP connections. The DRA scheme offers an intelligent, dynamic, policy-based approach to traffic prioritizing, load balancing, and accounting that controls the most critical areas of the TCP rate monitoring using the large deviation principle. Through its advanced traffic control algorithms, the DRA assures guaranteed traffic flows, minimal packet loss or retransmissions, optimizes TCP throughput, and assures that the network is always used to its maximum potential.

A novel delineation mechanism for the ATM adaptation layer 2 over wireless ATM networks

AbstractThe ATM adaptation layer 2 (AAL2) has been standardized by the ITU‐T for the support of low data rate and delay‐sensitive applications, such as voice, over ATM networks. One of the main characteristics of the AAL2 standard is the support for multiplexing information at the expense of introducing a new frame structure inside the payload of the ATM cells. The AAL2 standard introduces a mechanism for the delineation of the AAL2 packets and it has been found that the delineation mechanism reduces the performance of AAL2 in the presence of channels with high bit error rates. In this paper, a novel delineation mechanism is proposed for AAL2 to be used over highly error‐prone channels, such as wireless links. The proposed mechanism improves the performance (i.e. reduces packet loss) of the AAL2 standard in the presence of bit errors and in some cases reduces the overhead required for the delineation of the AAL2 packets. Copyright © 2002 John Wiley & Sons, Ltd.

A genetic algorithm for solving dual-homing cell assignment problem of the two-level wireless ATM network

In this paper, we investigate the optimal assignment problem, which assigns cells in Personal Communication Service to switches on Asynchronous Transfer Mode network in an optimum manner. The cost has two components: one is the cost of handoffs that involve two switches, and the other is the cost of cabling. This problem is model as dual-homing cell assignment problem, which is a complex integer programming problem. Since finding an optimal solution of this problem is NP-hard, a stochastic search method, based on a genetic approach, is proposed to solve this problem. In this paper, domain-dependent heuristics are encoded into crossover operations, mutations of genetic algorithm (GA) to solve this problem. Simulation results show that GA is robust for this problem.

무선 ATM망에서 rt-VBR 서비스를 위한 동적 슬롯 할당 기법

본 논문에서는 무선 ATM망에서 rt-VBR 서비스를 위한 동적 슬롯 할당 기법을 제안한다. 제안된 방식에서는 슬롯 할당을 요구하기 위한 예약 요청 패킷을 경쟁 기반으로 전송하고, 예약 요청이 성공하면 단말기에서는 비 경쟁 방식으로 동적 매개변수를 전달한다. 기지국 스케줄러는 예약이 성공한 단말기들이 잔여수명과 요청하는 슬롯 수와 같은 동적 매개변수를 전송하기 위한 DPS 미니슬롯을 할당한다. 한편 기지국 스케줄러는 단말기들이 전송한 잔여수명을 기반으로 잔여수명이 가장 짧은 단말기에게 상향 데이터 슬롯을 우선적으로 할당한다. 본 논문에서는 제안한 방식의 성능을 시뮬레이션을 통하여 분석하였다. 시뮬레이션의 결과, 제안한 동적 슬롯 할당 기법은 셀 손실률을 낮게 유지하면서 rt_VBR 서비스가 요구하는 전송 지연을 보장하고 있음을 알 수 있다. This paper proposes the dynamic slot allocation method for real-time VBR (rt-VBR) services in wireless ATM networks. The proposed method is characterized by a contention-based mechanism of the reservation request, a contention-free polling scheme for transferring the dynamic parameters. The base station scheduler allocates a dynamic parameter minislot to the wireless terminal for transferring the residual lifetime and the number of requesting slots as the dynamic parameters. The scheduling algorithm uses a priority scheme based on the maximum cell transfer delay parameter. Based on the received dynamic parameters, the scheduler allocates the uplink slots to the wireless terminal with the most stringent delay requirement. The simulation results show that the proposed method guarantee the delay constraint of rt-VBR services along with its cell loss rate significantly reduced.

Reducing signaling traffic in wireless ATM networks through handoff scheme improvement

AbstractWe propose a new handoff call management scheme which reduces signaling traffic in wireless ATM networks and improves the efficiency of the virtual channel. Chaining followed by a make‐break algorithm is a suitable handoff scheme for various situations. In the chaining part of the scheme, a chain routing algorithm is studied and compared with the hop‐limiting scheme. When the algorithm is implemented in our scheme, it improves the performance of the existing scheme in call drop rates so as to reduce the signaling traffic in wireless ATM networks. Copyright © 2002 John Wiley & Sons, Ltd.

무선 ATM에서 핸드오프 동안 실시간 VBR 서비스를 위한 전송 지연의 최소화 방안

일반적으로 유선 및 무선 ATM망에서 서비스 품질(QoS)에 대한 요구 사항은 서비스 유형에 따라 다르며, 실시간 비디오 서비스는 셀 손실보다 셀 전송 지연에 더 민감하다. 셀 손실 방지를 강조하고 있는 기존 핸드오프 방안들은 QoS를 만족시키기 위해 셀 전송 지연이 큰 단점을 가지고 있었다. 본 논문에서는 실시간 VBR 서비스에서 핸드오프 동안 새로운 기지국으로 전달될 셀 들 중에서 ATM 셀 헤더의 셀손실 우선순위(CLP)가 낮은 셀은 전달하고 CLP가 높은 셀은 폐기함으로써 셀 전송 지연을 최소화하는 방안을 제안한다. 제안된 방안은 MPEG 비디오 프레임을 대상으로 시뮬레이션을 통해 실시간 VBR 서비스의 QoS를 만족시키고 신속한 핸드오프에 적절하다는 것을 보여 주었다. In general, requirements for QoS are different according to the type of services in wire-line and wireless ATM networks, and real-time video service is more sensitive to cell transmission delay than to cell loss. Existing handoff schemes emphasizing prevention of cell loss had limitations in cell transmission delay to satisfy QoS. In this paper, a novel scheme to transmit ATM cells with low CLP(when CLP = 0) prior to others and discarding cells with high CLP(when CLF = 1) in ATM cell header among cells to be forwarded to new base station during handoffs in real-time VBR service is proposed. The proposed scheme is proven to be suitable for the satisfaction of QoS of real-time VBR service and appropriate for fast handoffs by giving high CLP value to less meaningful MPEG frames through simulations.

Rerouting for handoff based on the distance in wireless ATM networks

Whenever handoff for a mobile user occurs in wireless ATM network, its connection must be reestablished in the new area. This paper proposes a new path rerouting scheme based on the incremental reestablishment approach. It decides the crossover node by comparing the distances between each node in the existing path and the new location, while traversing the path backward. This scheme allows us to efficiently decide a new path whose length is close to the shortest path. In order to realistically evaluate and compare the proposed scheme, we model the distance a mobile user travels based on move speed and call duration statistics and propose a new approach for generating realistic random network. Comprehensive computer simulation for various random networks shows that the proposed scheme outperforms the previous schemes in terms of path efficiency and handoff delay. We also obtain path reuse efficiency of higher than 80%. The proposed scheme can be implemented using the information in the routing table of the underlying network.

Heuristic and simulated annealing algorithms for solving extended cell assignment problem in wireless ATM networks

Heuristic and simulated annealing algorithms for solving extended cell assignment problem in wireless ATM networks

Heuristic and simulated annealing algorithms for solving extended cell assignment problem in wireless ATM networks

AbstractIn this paper, we investigate the extended cell assignment problem which optimally assigns new adding and splitting cells in Personal Communication Service (PCS) to switches in a wireless Asynchronous Transfer Mode (ATM) network. Given cells in a PCS network and switches on an ATM network (whose locations are fixed and known), we would like to do the assignment in an attempt to minimize a cost criterion. The cost has two components: one is the cost of handoffs that involve two switches, and the other is the cost of cabling. This problem is modeled as a complex integer programming problem, and finding an optimal solution to this problem is NP‐hard. A heuristic algorithm and a simulated annealing algorithm are proposed to solve this problem. The heuristic algorithm, Extended Assignment Algorithm (EEA), consists of two phases, initial assigning phase and cell exchanging phase. First, in the initial assigning phase, the initial assignments of cells to switches are found. Then, these assignments are improved by performing cell exchanging phase in which two cells are repeatedly exchanged in different switches with great reduction of the total cost. The simulated annealing algorithm, ESA (enhanced simulated annealing), generates constraint‐satisfied configurations, and uses three configuration perturbation schemes to change current configuration to a new one. Experimental results indicate that EAA and ESA algorithms have good performances. Copyright © 2002 John Wiley & Sons, Ltd.