Applying switching and multiple access model for reducing packet loss and network overheads in watm

Dynamic bandwidth assignment schemes for TDMA (time division multiple access) based wireless ATM (asynchronous transfer mode) systems are discussed. TDMA generally requires hand-shake based protocols for time slot assignment which increases connection set-up time. This connection setup delay degrades the throughput performance of the wireless system if variable burst traffic, often encountered in ATM, is carried. To improve the throughput performance, this paper proposes two dynamic bandwidth assignment schemes, the autonomous assignment and release (AAR) scheme and the centralized assignment control (CAC) scheme, for TDMA-based wireless ATM and compares their throughput and delay performance.

The increasing importance of portable computing/telecommunications applications has motivated the studies on broadband wireless network technologies such as wireless ATM (Asynchronous Transfer Mode) or WATM. Orthogonal Frequency Division Multiplexing (OFDM) is especially suitable for high-speed communication due to its resistance to Inter Symbol Interference ISI. This paper describes an ATM network with wireless access for multimedia communications. The network has been specifically designed to serve as a testbed on which evaluate the effect of OFDM wireless channel. The paper overviews and simulates the ATM technology concepts and the requirements of wireless ATM from mobility and modulation technique.

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.

The world of wireless telecommunications is rapidly changing. The capabilities of wireless networks are improving at a steady pace. This paper presents two possible protocols for implementing mobility for wireless users in an asynchronous transfer mode (ATM) network. The vision of the authors is of one "wireless ATM telecommunications network" that is capable of supporting a variety of today's applications with room to grow for advanced applications of the future. We first visit database architectures that can support mobility in a wireless ATM network. We then discuss one of two signaling architecture alternatives, the "overlay signaling," for overlay support of mobile users in the ATM-based wireless telecommunications network. "Overlay signaling" aims at minimizing the modification needed to the existing ATM protocols. We then describe a native "migratory signaling" approach that further integrates wireless and wireline users into one global wireless ATM network at the expense of requiring some modifications to the existing ATM protocols. A performance analysis of the proposed signaling architecture alternatives is also presented. We conclude by pointing out some challenges in merging ATM with wireless telecommunications.

This paper proposes algorithms for handoff, location, and connection management in a wireless asynchronous transfer mode (ATM) local-area network (LAN). Fast handoffs while maintaining cell sequence and quality-of-service (QoS) guarantees are achieved by distributing switching functionality to base stations, and using a networking scheme based on provisioned virtual trees. A new distributed location management scheme using a minimal registration procedure and broadcasts on wired links is proposed for this LAN. The detailed signaling procedures that support the algorithms for mobility and connection management are described. Finally, an implementation of these procedures and an analysis of the measured data is presented. Measurements of service times obtained from this implementation indicate that over 100 calls/s. can be handled by each node in 50-node network with a high-percentage of mobiles (75%) relative to fixed endpoints. This is comparable to current wired ATM switch call handling throughputs, in spite of the fact that these nodes perform additional handoff and location management functions. The data also indicates handoff latency times of 1.3 ms. This validates our proposal for maintaining cell sequence while performing handoffs.

In future broadband networks based on asynchronous transfer mode (ATM) transmission and switching technology, the dominant kind of impairment is expected to be packet (ATM cell) losses. The use of forward error correction (FEC) codes has been proposed as a way to overcome these losses. However, the maximum length of a lost packet string that a packet loss recovery scheme can be designed to recover highly depends upon the temporal behavior between the adjacent packet loss bursts. Thus, a realistic model for describing the packet loss process is needed. The Gilbert model proposed for such purpose turns out to be an unrealistic model, since it fails to consider some important characteristics during the packet loss process. A more realistic model is advanced in this paper.

This paper presents a dynamic anchor scheme in wireless ATM (asynchronous transfer mode) networks, which improves the location registers (LR) scheme, in which LR’s are hierarchically structured. This dynamic anchor scheme introduces the CCR (communication-to-computation cost ratio) term in the LR scheme. The proposed scheme reduces computation cost by introducing the active LR. There are at most two active LR’s in a hierarchical arrangement of LR’s and the location of one active LR is static and the location of another active LR called as anchor LR is dynamically selected among the LRs in the hierarchy in order to minimize a total location management cost. The total location management cost is calculated depending on the CCR as well as the CMR (call-to-move ratio). Numerical results show that the proposed scheme can reduce the location management cost compared with the original LR scheme for the different values of the CCR and the CMR.KeywordsWireless ATMLocation Managementanchor scheme

Dynamic slot assignment protocol for QoS support on TDMA-based mobile networks

This paper describes current and proposed protocols for mobility management for public land mobile network (PLMN)-based networks, mobile Internet protocol (IP) wireless asynchronous transfer mode (ATM) and satellite networks. The integration of these networks will be discussed in the context of the next evolutionary step of wireless communication networks. First, a review is provided of location management algorithms for personal communication systems (PCS) implemented over a PLMN network. The latest protocol changes for location registration and handoff are investigated for mobile IP followed by a discussion of proposed protocols for wireless ATM and satellite networks. Finally, an outline of open problems to be addressed by the next generation of wireless network service is discussed.

Wireless Asynchronous Transfer Mode (ATM)

Wireless Asynchronous Transfer Mode (ATM)

Provisioning multicast QoS for WDM-based optical wireless networks

High speed Asynchronous Transfer Mode (ATM) wireless networks are assuming a growing interest in the personal communication area [1–6]. This paper describes the design of a wireless ATM system, which is being implemented in the ’’MEDIAN‘‘ project belonging to the European Community (EC) Advance Communications Technologies and Services (ACTS) programme. The Medium Access Control (MAC) aims at providing a simple and efficient transport for ATM cells from a Base Station (BS), interfaced with the ATM Broadband Integrated Service Digital Network (B-ISDN), to ATM Portable Stations (PSs) and vice versa. A Time Division Duplex (TDD) scheme is adopted in which uplink and downlink frame durations can be varied frame-by-frame, in order to fit the present uplink/downlink traffic mix. Moreover, in the uplink, a contention-free based technique is considered in which the slots are assigned to the calls depending on the present load of the PS uplink buffers. The proposed interworking with the ATM network is based on the concept of intercepting the ATM Signalling and Management Cells at the BS, in order to deduce from the ATM Q.2931 messages information relevant to the registration, the call set-up and the MAC procedures.

A new method to recover (8/spl times/8) block losses for JPEG compressed images is proposed, which can be used in wireless UMTS and asynchronous transfer mode (ATM) networks. The problem of image reconstruction with (8/spl times/8) block losses is transformed to a system of linear equations using two-dimensional trigonometric polynomials. The simulation results show the feasibility of this method. The sensitivity analysis of the proposed method shows that this method is robust against additive noise.

This paper describes the design of reliable wireless Asynchronous Transfer Mode (ATM) System to be used by the U.S. military and the commercial marketplace. This system, called Survivable ATM, consists of three main components: (1) Transmission Error Control System (TECS), (2) Reliable ATM Adaptation Layer (AAL), (3) Network Management System. These three components deliver a set of previously unavailable capabilities to achieve and maintain reliable performance of commercial ATM technology in wireless environments. These components collectively provide reliable end-to-end operation of ATM communication systems in deployed wireless terrestrial and satellite networks. At the data link layer, the TECS dynamically selects data link packet length and the strength of Forward Error Correction (FEC) coding. The result of this adaptive error control mechanism allows for the maximum utilization of bandwidth for wireless terrestrial and satellite communication systems. Higher performance can be achieved by pushing down the error correction lower on the protocol stack. The Reliable AAL, referred to as AAL X, provides for residual error recovery during cases of ATM congestion, where the TECS cannot detect this type of condition. Environments with limited bandwidth capabilities, such as the U.S. military, can truly benefit from the Survivable ATM System.