Wireless ATM Networks Research Articles

Bandwidth-efficient wireless OFDM

Due to ever-increasing bandwidth demands in future wireless service, the radio frequency band becomes more and more invaluable. In this paper, we address channel equalization for bandwidth-efficient wireless orthogonal frequency-division multiplexing (OFDM). First, we show that in order to be free of both interchannel interference and interblock interference, wireless OFDM has to occupy a bandwidth wider than the Nyquist rate and use insufficient statistics in symbol demodulation. Thus, the conventional OFDM gains computational efficiency using the discrete Fourier transform (DFT) in demodulation at the cost of low efficiency of bandwidth usage and degradation in symbol error performance. Then we consider the OFDM that achieves high efficiency of bandwidth usage, allows interchannel interference and interblock interference to exist, and uses sufficient statistics in symbol demodulation. A one-tap decision feedback equalizer (DFE) is proposed for equalization of the bandwidth efficient OFDM system. Simulation and numerical evaluation for an indoor wireless asynchronous transfer mode network are carried out. It is demonstrated that though occupying a narrower bandwidth, the one-tap DFE-based bandwidth-efficient OFDM system achieves lower symbol error rate and higher mutual information than the conventional DFT-based OFDM system. The proposed OFDM system presents a monotonically increasing symbol error rate, and convex-down achieved mutual information with respect to increasing efficiency of bandwidth usage.

Design and implementation of a QoS oriented data-link control protocol for CBR traffic in wireless ATM networks

This paper presents a QoS oriented Data Link Control (DLC) framework for transporting Constant Bit Rate (CBR) traffic over wireless ATM links. Data link control is usually omitted in fixed ATM networks because cell corruption due to channel error is extremely rare for reliable media like copper wire and optical fiber. However, for wireless, higher bit error rates are quite common due to shadowing and other fading effects. The purpose of DLC in wireless is to provide error-free transport to the higher layers by recovering corrupted cells at the link layer. A selective reject (SREJ) automatic repeat request (ARQ) based DLC protocol is used for CBR error recovery. For an ARQ based scheme, higher recovery rates can be achieved with larger cell transfer delay, caused by cell retransmissions. Since cell transfer delay and DLC recovery rate both translate to user-perceivable Quality-of-Service (QoS), it is important for the DLC to strike a balance between these two, depending on the application's requirements. To achieve this in our protocol, the retransmission procedure for a CBR cell is constrained to complete within a recovery time interval which is specified by the application at call-setup time. Also, a novel jitter removal scheme that reduces the cell delay variation caused by cell loss and retransmissions, is incorporated as a part of the DLC protocol. The proposed protocol is implemented on NEC's WATMnet prototype system. The implementation and its experimental results are reported for illustrating the performance and feasibility of the presented CBR DLC protocol. The experimental results show that the DLC protocol can be successfully applied for QoS-constrained error recovery of CBR traffic on a per-connection basis. These also indicate that the DLC can be programmed to attain a desirable tradeoff between cell transfer delay and cell recovery rate.

Local and Global Handovers Based on In-Band Signaling in Wireless ATM Networks

This paper presents a handover protocol for wireless ATM networks, which makes use of in-band signaling, i.e., of ATM resource management cells, to process network handovers and guarantee the in-sequence and loss-free delivery of the ATMcells containing user data. The goal of the proposed approach is to minimize the modifications of the ATM signaling standard required to overlay user mobility onto the fixed network infrastructure, and provide for a gradual upgrade of the fixed network to handle mobility. The proposed protocol handles both local handovers, in which the connection access point needs not migrate to a new ATM local exchange, and global handovers, in which the connection access point must migrate to a new local exchange. The handover scheme is devised so as to grant in-sequence delivery of cells. The performance of the network during handover is analyzed in case of connections requiring loss-free operation. The considered performance figures are the cell transmission delay introduced by the handover and the cell buffering requirements posed to the network. The behavior of the proposed protocol in presence of multiple handovers is studied via simulation, while a simple analytical method is derived for the performance evaluation of a single handover in isolation.

Broadband satellite networks-the global IT bridge

Next-generation broadband satellite networks are being developed to carry bursty Internet and multimedia traffic in addition to the traditional circuit-switched traffic (mainly voice) on a global basis. These satellites provide direct network access for personal applications as well as interconnectivity to the terrestrial remote network segments. The main requirement in success of these networks is that they should be able to transmit high data rate traffic with prescribed quality of service (QoS). Thus, the broadband satellite network has no choice other than the rise of ATM technology and to be optimized for Internet-based traffic. ATM is the promising technology for supporting high-speed data transfer potentially suitable for all varieties of private and public telecommunications networks. IP, on the other hand is the fast-growing Internet layer protocol that is applicable over any data link layer Internet-based applications are the emerging source of traffic in the future wireless networks and broadband satellite networks should consider Internet as the primary service. In this paper, we discuss the traditional ATM and wireless ATM networks and explain the characteristics of the wireless IP networks. The paper then uses those concepts in defining the criteria for the broadband satellite networks such as the QoS and traffic management. Application of the broadband satellite networks is also proposed.

Connection Rerouting for Wireless ATM Networks

Wireless ATM (Asynchronous Transfer Mode) is an emerging technology designed to provide multimedia and other Quality of Service-oriented applications to mobile users by extending ATM connections to...

An Efficient Location Management Protocol for Wireless ATM Customer Premises Networks

In this paper we present a new location management protocol for wireless ATM networks, called LMCP (Location Management and Control Protocol). This protocol is based on the PNNI (Private Network-to-Network Interface) routing functionality to advertise the movement of mobile terminals within pre-defined areas. Moreover, LMCP uses specialized entities to store and retrieve the current location area of mobile terminals. These entities are located in mobility enhanced switches that control the execution of other mobility procedures (e.g. handovers). The main benefit from the application of LMCP is the establishment of connections that do not contain any misrouted segments. Furthermore, it requires minor modifications to the PNNI and enables its inter-working with other location management mechanisms. The protocol is compared with other similar mechanisms, and its efficiency is demonstrated by the results of an analytical model.

Delay performance of voice and MMPP video traffic in cellular wireless ATM network

An approximate analysis is derived of real-time voice and Markov modulated Poisson process (MMPP) video traffic over an enhanced time division multiple access with dynamic reservation (TDMA/DR) MAC protocol in a wireless ATM setting. This yields the mean delay and the delay distribution of such traffic under light loads (less than 60% of the total channel capacity). The reasonableness of the approximate analysis is verified by simulation. Numerical results indicate that the delay performances of voice and MMPP video traffic types are well within the respective delay tolerance for real-time services. The results lead to the conjecture that the enhanced TDMA/DR is a viable MAC protocol for handling real-time services in an integrated services wireless ATM system.

A comprehensive approach to signaling, transmission, and traffic management for wireless ATM networks

We propose and evaluate a signaling and transmission algorithmic system for wireless digital networks, in conjunction with a Traffic Monitoring Algorithm (TMA) for dynamic capacity allocation in multimedia ATM environments. The deployed signaling protocol is stable, and two transmission techniques are compared: a Framed Time-Domain Based (FTDB) technique and a Framed CDMA (FCDMA) technique. The overall signaling/transmission/traffic monitoring proposed system has powerful performance characteristics, while the TMA-FTDB combination is superior to the TMA-FCDMA combination in environments where message lengths are relatively short and the speed of the transmission lines is relatively low. We also evaluate a system deploying the Ethernet protocol as a signaling protocol, instead. In the presence of relatively tight admission delay constraints in signaling, the latter is significantly inferior to our proposed signaling technique. As the above admission delay constraints diminish, the Ethernet protocol breaks down, while our proposed signaling technique maintains its high performance characteristics.

Performance evaluation of multiple access control schemes for wireless multimedia services

Multiple access control (MAC) protocols for a wireless ATM network are required to handle the diverse traffic characteristics in CBR, VBR and ABR data. Considerable research effort expended in tackling the problem has resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how these different protocols compare with each other on a unified basis. Seven recently proposed TDMA-based MAC protocols for integrated wireless data and voice services are quantitatively compared. Using a time-varying channel model, the protocols are evaluated by simulations. It is found that exploiting the synergy between the MAC and physical layers can lead to a higher performance.

Dynamic location management scheme for locationregisters in wireless ATM networks

The authors propose an enhanced location management scheme for the location register (LR) scheme in wireless ATM networks. The main distribution is the use of at most two active LRs and the dynamic scope-limiting parameter S depending on the communication-to-computation cost ratio (CCR) as well as the call-to-move ratio (CMR). As a result, the proposed scheme can reduce the location management cost compared with the original LR scheme for the different CCR value and CMR value.

Multiple access control with intelligent bandwidth allocation for wireless ATM networks

Two major challenges pertaining to wireless asynchronous transfer mode (ATM) networks are the design of multiple access control (MAC), and dynamic bandwidth allocation. While the former draws more attention, the latter has been considered nontrivial and remains mostly unresolved. We propose a new intelligent multiple access control system (IMACS) which includes a versatile MAC scheme augmented with dynamic bandwidth allocation, for wireless ATM networks. IMACS supports four types of traffic-CBR, VBR, ABR, and signaling control (SCR). It aims to efficiently satisfy their diverse quality-of-service (QoS) requirements while retaining maximal network throughput. IMACS is composed of three components: multiple access controller (MACER), traffic estimator/predictor (TEP), and intelligent bandwidth allocator (IBA). MACER employs a hybrid-mode TDMA scheme, in which its contention access is based on a new dynamic-tree-splitting (DTS) collision resolution algorithm parameterized by an optimal splitting depth (SD). TEP performs periodic estimation and on-line prediction of ABR self-similar traffic characteristics based on wavelet analysis and a neural-fuzzy technique. IBA is responsible for static bandwidth allocation for CBR/VBR traffic following a closed-form formula. In cooperation with TEP, IBA governs dynamic bandwidth allocation for ABR/SCR traffic through determining the optimal SD. The optimal SDs under various traffic conditions are postulated via experimental results, and then off-line constructed using a back propagation neural network (BPNN), being used on-line by IBA. Consequently, with dynamic bandwidth allocation, IMACS offers various QoS guarantees and maximizes network throughput irrelevant to traffic variation.

LINK-STATE AWARE DYNAMIC TRAFFIC SCHEDULING FOR PROVIDING PREDICTIVE QoS IN WIRELESS MOBILE MULTIMEDIA NETWORKS

The performance of a centralized traffic priority based dynamic burst-level cell scheduling scheme is investigated in a correlated fading channel. The scheduling scheme is designed for the transmission of multiservice traffic over TDMA (Time Division Multiple Access)/TDD (Time Division Duplex) channels in a WATM (Wireless ATM) network. In this scheme, the number of slots allocated to a VC (Virtual Circuit) during a frame-time is changed dynamically depending on the traffic type, system traffic load, TOE (Time of Expiry) value of the data burst and data burst length. While allocating bandwidth, the channel error status is also taken into consideration. SR-ARQ (Selective Repeat - Automatic Repeat Request)-based link-level error control is assumed for all the traffic types in a multiservice traffic environment. The performance of the proposed scheme under correlated Rayleigh fading is evaluated using computer simulation for realistic voice, video and data traffic models and the QoS (Quality of Service) requirements of different traffic classes in a wireless mobile network. Simulation results show that the proposed scheduling framework can provide reasonably high channel utilization with predictive QoS guarantee in a multiservice traffic environment. The channel utilization and the perceived QoS for different services is highly affected by the traffic burstiness of the corresponding traffic type. Such a scheme can result in an energy efficient TDMA/TDD medium access control protocol for broadband wireless access.

Polling- and contention-based schemes for TDMA-TDD access to wireless ATM networks

The design of an efficient MAC protocol is of paramount interest for the definition of a wireless ATM (WATM) access. In the case of TDMA-TDD WATM access, the current trend in the standardization bodies is to adopt frames of fixed duration, whose slots are shared among uplink and downlink connections under the control of a MAC scheduler located in the base station. In this paper, we first compare polling and contention techniques, in order to identify the best access scheme to serve ATM connections. Then, since the knowledge of the queue status of the portable terminals can be used by the centralized scheduler to increase the efficiency of the slot assignment procedure, we propose different algorithms to code the buffer occupancy status. Moreover, we compare their performance by considering two different scenarios; the first loaded with ON-OFF sources served by nrt-VBR ATM connections, and the second with TCP/IP sources served by UBR ATM connections. The results show the superiority of the contention access and the advantages of the buffer status notification for the scheduler at the base station.

Contention-free distributed dynamic reservation MAC protocol with deterministic scheduling (C-FD/sup 3/R MAC) for wireless ATM networks

This paper proposes a novel MAC protocol for wireless ATM networks, which is characterized by a contention-free mechanism of the reservation request and a deterministic nature of mobile-assisted (distributed) uplink scheduling under a framework of the dynamic reservation TDMA, as discussed in the current standardization activities of ETSI Project BRAN (broadband radio access network) and the wireless ATM working group in the ATM Forum. The design objective of the proposed MAC protocol is to guarantee the real-time constraint of the real-time VBR (rt-VBR) traffic class while maximizing the multiplexing gain among all ATM traffic classes, especially with a fixed length frame. The proposed deterministic scheduling scheme for the rt-VBR traffic class lends itself to implementing the minimal configuration of control data units for reservation request as desired under the limited wireless resources. Simulation experiments using statistically multiplexed MPEG-2 video streams are performed for a 25 Mbits/s wireless ATM access link scenario. It has been shown that the proposed framework guarantees the delay constraint of rt-VBR sessions along with its cell loss rate significantly reduced, while improving the average delay performance of the nrt-VBR in the range of 10%-30% without compromising the channel utilization as compared to the DSA++ system.

The Impact of Handover Protocols on the Performance of ABR Flow‐Control Algorithms in a Wireless ATM Network

AbstractConsidering the high‐speed data transfer by the ABR service class in a wireless ATM network, we investigate the impact of forward and backward hard handover protocols on the performance of the three rate‐based ABR flow‐control schemes Explicit Rate Indication for Congestion Avoidance (ERICA+), Fuzzy Explicit Rate Marking (FERM) and a new promising adaptation of FERM, called FERMA. We evaluatc the performance of these flow‐control protocols by means of an object‐oriented simulation modcl of a basic client‐scrvcr architecture. Considering a standard hard handover protocol in a wircless ATM nctwork. wc show that our proposcd enhanced signaling schemes based on a congestion‐awarencssconceptand their integratibn into thc ABR flow control have a positive influence on the stability and efficiency of the cell transfer by ABR connections. Morcovcr, we point out that the new adaptation of the fuzzy‐control scheme FERM provides a promising altcrnativc lo the ERICA+ algorithm.

An efficient handoff management scheme for mobile wireless ATM networks

A new handoff management scheme for wireless ATM networks is proposed. In this scheme, all cells are connected to their neighboring cells by permanent virtual circuits (PVCs) and to the access switch (AS) by switched virtual circuits (SVCs) which are only for new calls. Some carefully chosen cells, called rerouting cells, are also connected to the AS by PVCs. In summary, if a mobile roams to an ordinary neighboring cell, its traffic path is simply elongated by a PVC connecting the old and new cells. If a mobile roams to a rerouting cell, its traffic path is rerouted to a PVC between the AS and rerouting cell. By using PVC's for handoff calls, we can guarantee fast and seamless handoff. At the same time, our scheme improves the path efficiency by limiting the maximum number of hops that a path can be extended. Also, allowing path rerouting at a suitable time means the network resources are more efficiently utilized.

An adaptive approach to manage traffic in CDMA ATM networks

Wireless Asynchronous Transfer Mode ( WATM) systems are becoming an important field in recent days due to their increasing use and applications. A WATM system is the result of synergy between wireless networks and asynchronous transfer mode ( ATM) technologies. Designing an efficient mobile communication system is considered as a challenging task, given its complexity and operation environments. A major task activity related to these systems addresses the call admission control and resource management. In this paper, we consider these issues in wireless ATM networks integrating the Code Division Multiple Access ( CDMA) technology. An approach for a dynamic resource management is proposed using heterogeneous traffic descriptors as well as the concept of signal-to-interference rate, computed at the base station receivers. An adaptive monitoring scheme that is based on an estimation algorithm and driven by a measurement of the signal-to-interference and predicted traffic parameters of the admitted connections is established. The Dynamic control that we propose at the user network interface, UNI, provides information about the instantaneous bit rate of a source allowing more effective flow control and achieves a good match in terms of predicting the congestion of any switch. It is able to police implicit resource management, which is used for both Constant Bit Rate ( CBR) and Variable Bit Rate ( VBR) traffics as well as explicit resource management that is used for Available Bit Rate ( ABR) traffic.

Design of multicode CDMA systems for 3-D stereoscopic video over wireless ATM networks

This paper investigates the application of multicode spread-spectrum code-division multiple-access (SS-CDMA) techniques to three-dimensional (3-D) stereoscopic video transmission over wireless asynchronous transfer mode (ATM) networks. Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. Such services allow users to share the virtual reality (VR) world without any geographical restrictions. In order to create a 3-D system with two images (left and right) that should be transmitted over a bandlimited mobile channel simultaneously, a cost-effective motion picture experts group (MPEG)-based wavelet multiresolution coding with a joint motion and disparity compensation is developed to reduce a large amount of information contained in the images to meet the low-transmission rate limitation of mobile channels. However, the rapidly variable bit rate (VBR) characteristics of the MPEG-based 3-D videos seems a weakness to the transmission of such videos via a constant bit-rate (CBR) mobile channel. The ATM technique is especially well suited for VBR MPEG-based 3-D video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a limited channel capacity, the overall capacity of the traditional ATM-based SS-CDMA system may not be sufficient to accommodate the MPEG-based 3-D video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide VBR MPEG-based 3-D video services by varying the number of spreading codes assigned to the 3-D video to meet its dynamic throughput requirement. Powerful forward error correction (FEC) codes are necessary to protect the video data so that it can be successfully transmitted at an acceptable signal power level. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing 3-D video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure correct delivery and low cell loss rate (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to the priority of the payload data in 3-D videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate to minimize the extra bandwidth for FEC overhead.

Distributed control of wireless ATM networks using CORBA

This paper reports the design, implementation, and performance evaluation of a CORBA based distributed control architecture for signalling and mobility management in the Wireless ATM Research project (WARP). The distributed control architecture makes use of open signalling to manipulate the various network resources to realise network services such as call control, multicast, and mobility management. Open signalling provides the flexibility and ease in creating new network services as opposed to standard signalling approaches such as the ATM Forum signalling. The network control architecture provides inter-working with the ATM Forum UNI signalling. The open signalling is found to be more flexible compared to the UNI-PNNI based signalling and yields comparable delay performance.

Efficient call admission control for heterogeneous services in wireless mobile ATM networks

An efficient call admission control scheme for handling heterogeneous services in wireless ATM networks is proposed. Quality-of-service provisioning of jitter bounds for constant bit rate traffic and delay bounds for variable bit rate traffic is used in the CAC scheme to guarantee predefined QoS levels for all traffic classes. To reduce the forced handoff call dropping rate, the CAC scheme gives handoff calls a higher priority than new calls by reserving an appropriate amount of resources for potential handoff calls. Resource reservation in the CAC scheme makes use of user mobility information to ensure efficient resource utilization. Simulation results show that the proposed CAC scheme can achieve both low handoff call dropping rate and high resource utilization.