A unified performance model for reservation-type multiple-access schemes

This paper presents a unified performance model for the integrated voice/data wireless system using reservationtype multiple-access (MA) schemes. It is observed that although these schemes are different in the frame structure and resource assignment procedure, all of them can be described by several common state variables whose evolvement exhibits the Markovian property. Based on this observation, a general Markovian model is developed in this paper. Three performance measures, namely, voice-packet-loss probability, data throughput, and data delay are defined. As a special case, the performance evaluation model for the voice-only system is also presented. Numerical results are given and verified by simulation under both voice-only and integrated scenarios using packet-reservation MA (PRMA), dynamic time-division multiple access (D-TDMA), and resourceauction multiple access (RAMA) as examples. It is found that our analytical model is quite accurate, especially in the region of interest. The impact of system parameters (such as the voice-permission probability, data-retransmission probability, maximum number of voice slots per frame, etc.) on the integrated system performance is also investigated for these three example systems. © 1998 IEEE.published_or_final_versio

The Feasibility of ATM operations over high frequency radio and the viability of the ATM/HF architecture

High Frequency (HF) radio is still a vital part of communications networks because its low cost and long distance capabilities, and still plays important roles as primary, supplemental, or redundant backup systems. Asynchronous Transfer Mode (ATM) is increasingly becoming an important part of communications, especially with LAN Emulation (LANE) specifications. Add to this the importance and increasing interest and dependency upon wireless networking, and it becomes inevitable that research into mobile ATM networking over HF radio would be considered. To test the feasibility of ATM networking over HF radio it was decided that a simulation would be developed to collect some basic information on call blocking and throughput. In order to build the simulation it was necessary to have an architectural framework of a mobile ATM network operating over HF radio. ATM/HF (ATM over HF) is the proposed architecture. ATM/HF is a proposed architecture that provides for networking mobile ATM nodes such as ships, planes, and trucks, over HF radio. It is based upon a recommended 64 kHz bandwidth which allows for a 128 kbps data rate. The ATM/HF architecture utilizes three different Media Access Control (MAC) protocols for network startup and access from the various network states, and incorporates several recently proposed dynamic capabilities for control of bandwidth and the integration of voice, data, and video. The proposal provides frame and wireless ATM (WATM) packet structures and a reference model for flow of the cells from the ATM Adaptation Layer (AAL) through the radio. An important feature is the use of channels, called channelization, to increase both network capacity and distance. The simulation was built to represent an active network state with active nodes connecting and disconnecting calls in a dynamic way with explicit connection messages. The purpose of starting from this network state was to measure the call blocking and throughput of a single channel. Two user types were developed, one to represent telephone voice and the other to represent computer data traffic. By varying the number of users per node and by type, the level of call blocking and throughput could be changed. Graphing the levels it could be determined the maximum capacity a single channel could support and thus determine if ATM over HF radio is feasible. In addition, the same information was used to determine the viability of the ATM/HF architecture. Although the simulation did not incorporate all the dynamic features of the recommended protocols, it does dynamically assign slots, rearrange slots to utilize non-contiguous available slots, and adjust the data rate of computer connections to accommodate voice call requests. This was done to reduce the level of voice call blocking which became the determining factor in deciding feasibility. It was determined that mobile ATM networking over HF radio is possible since the voice call blocking of a single channel was at the 10% level, overall call blocking was at the 6% level, and throughput was at the 53% level. It was determined that a single channel could support six voice and a minimum of ten data users. Although throughput, which is defined as the number of available slot used, was lower than expected, the possibility exists for utilizing the unused slots by incorporating additional dynamic capabilities that would increase the number of users supportable by a single channel. Throughput can be also be increased by incorporating Available Bit Rate (ABR) and Unspecified Bit Rate (UBR) traffic. The call blocking and throughput levels prove that ATM/HF is a viable method for supporting ATM operations. Although the call blocking level achieved the voice call blocking level and exceeding the overall call blocking level, the throughput level shows that there is a lot of wasted bandwidth. Further study of the design is required to improve the throughput level. Further development of the simulation is required in order to test the MAC protocols and to test the effects of the Bit Error Rate and fading effects of HF radio. The final conclusion, however, is that ATM over HF radio is feasible, that ATM/HF is a viable architecture, and that further research should be conducted into both

Adaptive S-ALOHA CDMA as an alternative way of integrating services in mobile environments

Code-division multiple-access (CDMA) schemes appear to be very promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating nonreal-time (i.e., Internet applications) and real-time (i.e., voice) services in a multicell scenario by exploiting the potentials of CDMA under time-varying channel load conditions. The adaptive component makes data terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay, which can be analytically obtained by defining a birth-death process, is almost always achieved. Moreover, by means of a simplified cellular model, the proposed algorithm revealed the same behavior, i.e., it tries to select the most suitable transmission rate at any time slot, when it is affected by intercell interference and even by power control imperfections. Finally, in order to gain more insight into the potentials of such an access strategy, the adaptive S-ALOHA CDMA scheme is then compared to a reservation time-division multiple-access (TDMA)-based protocol (PRMA++), showing the benefits of the CDMA-based solution in terms of capacity, flexibility, and data delay performance.Peer Reviewe

A flexible medium access control framework for multimedia application support in wireless ATM

Includes bibliographical references.The field of wireless communications has seen phenomenal development over the last decade. With the current abundance of applications that use broadband multimedia over wired networks it is logical that users will want to have access to these same multimedia streams [rom a mobile terminal. Wireless solutions for connectivity to networks such as Ethernet networks already exist, however, a method of supporting access to an ATM network from a mobile terminal has not yet been standardised. Transporting ATM data over the wireless medium poses a number of problems. The Medium Access Control (MAC) layer of any proposed wireless ATM network would be responsible for resolving many of these problems. Unfortunately, research into MAC layers is hampered by the fact that most existing MAC layers cannot be modified in order to experiment with the effectiveness of the many MAC protocol techniques that exist

A MAC protocol for IP-based CDMA wireless networks.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.The evolution of the intemet protocol (IP) to offer quality of service (QoS) makes it a suitable core network protocol for next generation networks (NGN). The QoS features incorporated to IP will enable future lP-based wireless networks to meet QoS requirements of various multimedia traffic. The Differentiated Service (Diffserv) Architecture is a promising QoS technology due to its scalability which arises from traffic flow aggregates. For this reason, in this dissertation a network infrastructure based on DiffServ is assumed. This architecture provides assured service (AS) and premium service (PrS) classes in addition to best-effort service (BE). The medium access control (MAC) protocol is one of the important design issues in wireless networks. In a wireless network carrying multimedia traffic, the MAC protocol is required to provide simultaneous support for a wide variety of traffic types, support traffic with delay and jitter bounds, and assign bandwidth in an efficient and fair manner among traffic classes. Several MAC protocols capable of supporting multimedia services have been proposed in the literature, the majority of which were designed for wireless A1M (Asynchronous Transfer Mode). The focus of this dissertation is on time division multiple access and code division multiple access (TDMAlCDMA) based MAC protocols that support QoS in lP-based wireless networks. This dissertation begins by giving a survey of wireless MAC protocols. The survey considers MAC protocols for centralised wireless networks and classifies them according to their multiple access technology and as well as their method of resource sharing. A novel TDMAlCDMA based MAC protocol incorporating techniques from existing protocols is then proposed. To provide the above-mentioned services, the bandwidth is partitioned amongst AS and PrS classes. The BE class utilizes the remaining bandwidth from the two classes because it does not have QoS requirements. The protocol employs a demand assignment (DA) scheme to support traffic from PrS and AS classes. BE traffic is supported by a random reservation access scheme with dual multiple access interference (MAl) admission thresholds. The performance of the protocol, i.e. the AS or PrS call blocking probability, and BE throughput are evaluated through Markov analytical models and Monte-Carlo simulations. Furthermore, the protocol is modified and incorporated into IEEE 802.16 broadband wireless access (BWA) network

Protocols for voice/data integration in a CDMA packet radio network.

Thesis (Ph.D.)-University of Natal, Durban, 1999.Wireless cellular communications is witnessing a rapid growth in, and demand for, improved technology and range of information types and services. Future third generation cellular networks are expected to provide mobile users with ubiquitous wireless access to a global backbone architecture that carries a wide variety of electronic services. This thesis examines the topic of multiple access protocols and models suitable for modem third-generation wireless networks. The major part of this thesis is based on a proposed Medium Access Control (MAC) protocol for a Code Division Multiple Access (CDMA) data packet radio network, as CDMA technology is proving to be a promising and attractive approach for spectrally efficient, economical and high quality digital communications wireless networks. The proposed MAC policy considers a novel dual CDMA threshold model based on the Multiple Access Interference (MAl) capacity of the system. This protocol is then extended to accommodate a mixed voice/data traffic network in which variable length data messages share a common CDMA channel with voice users, and where the voice activity factor of human speech is exploited to improve the data network performance. For the protocol evaluation, the expected voice call blocking probability, expected data throughput and expected data message delay are considered, for both a perfect channel and a correlated Rayleigh fading channel. In particular, it is shown that a significant performance enhancement can be made over existing admission policies through the implementation of a novel, dynamic, load-dependent blocking threshold in conjunction with a fixed CDMA multiple access threshold that is based on the maximum acceptable level of MAl

Improving VBR voice performance in integrated services broadband wireless networks

The integration of multimedia applications into future wireless networks is expected to accelerate the demand for incorporating broadband infrastructure into wireless arena. Providing an efficient broadband wireless infrastructure capable to carry a mixture of different services brings a large set of new technical challenges. The current wireless networks that have been designed to carry low bit-rate voice and data are not able to carry bandwidth consuming and delay sensitive multimedia traffic. Consequently fundamental changes at different layers of current technology used in wireless networks are required. In this thesis we focus on Medium Access Control protocols (MAC) suitable for broadband wireless networks. Wireless ATM (WATM) has been considered in this work. This is mainly because it is widely accepted that ATM is the foundation of future broadband networks and integrating ATM into wireless networks provides a seamless interface between wired and wireless environments. We investigate the major recent proposals for MAC protocols for broadband wireless networks and propose a new reservation mechanism for the reservation part of a FDD-based MAC protocol. This novel mechanism is called “Dynamic Hybrid Partitioning with Adjustable Repeat” which helps to improve the performance of the Variable Bit Rate (VBR) voice traffic in a broadband wireless network with integrated traffic. Through a number of simulation experiments based on AKAROA2 [Ewi99J, we analyze the different aspects of our proposed mechanism and show how it improves the performance of the VBR voice traffic sources in a network with different classes of traffic

Improving VBR voice performance in integrated services broadband wireless networks

The integration of multimedia applications into future wireless networks is expected to accelerate the demand for incorporating broadband infrastructure into wireless arena. Providing an efficient broadband wireless infrastructure capable to carry a mixture of different services brings a large set of new technical challenges. The current wireless networks that have been designed to carry low bit-rate voice and data are not able to carry bandwidth consuming and delay sensitive multimedia traffic. Consequently fundamental changes at different layers of current technology used in wireless networks are required. In this thesis we focus on Medium Access Control protocols (MAC) suitable for broadband wireless networks. Wireless ATM (WATM) has been considered in this work. This is mainly because it is widely accepted that ATM is the foundation of future broadband networks and integrating ATM into wireless networks provides a seamless interface between wired and wireless environments. We investigate the major recent proposals for MAC protocols for broadband wireless networks and propose a new reservation mechanism for the reservation part of a FDD-based MAC protocol. This novel mechanism is called “Dynamic Hybrid Partitioning with Adjustable Repeat” which helps to improve the performance of the Variable Bit Rate (VBR) voice traffic in a broadband wireless network with integrated traffic. Through a number of simulation experiments based on AKAROA2 [Ewi99J, we analyze the different aspects of our proposed mechanism and show how it improves the performance of the VBR voice traffic sources in a network with different classes of traffic

Current Situation and Development Trend of Mobile Communication Systems

This paper introduces the development background of mobile communication and the development of mobilecommunication. It introduces the application principle, network structure, main technology, the advantages anddisadvantages of the three generations of mobile communication system respectively, and introduces the currentthird generation mobile communication system, including its technical support and research direction, analysis andcomparison of the European WCDMA system, the United States CDMA2000 system and China's TD-SCDMA systemtechnical characteristics. Finally, the development trend and prospect of future mobile communication system arediscussed