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Future wireless networks need to support different service requirements. Ho-sever, the exiting methods of specifying QoS commitments, namely qualitative commitment and quantitativ e commitment are not perfect for a wireless communication environment. In this paper, we propose a new concept called compound QoS commitment which combines qualitative and quantitative commitments within a single service commitment. As such, the proposed concept can provide a practical approach to deal with the highly variable wireless netw ork capacijr. Since each compound QoS commitment has tw o degrees of freedom, it m\ also increase the fiexibilit y in committing an ahievable QoS. In order to show the feasibility of the proposed concept, we present a scheduling algorithm whic hcan sim ultaneouslypro vide a proportional dropping ratio guarantee and a deterministic upper delay guarantee to a flow. Numerical results confirm that the algorithm is capable of delivering the tw o guarantees simultaneously.

For various advantages including better utilization of radio spectrum (through frequency reuse), lower mobile transmit power requirements, and smaller and cheaper base station equipment, future wireless mobile multimedia networks are likely to adopt micro/picocellular architectures. A consequence of using small cell sizes is the increased rate of call handoffs as mobiles move between cells during the holding times of calls. In a network supporting multimedia services, the increased rate of call handoffs not only increases the signaling load on the network, but makes it very difficult for the network to guarantee the quality of service (QoS) promised to a call at setup or admission time. This paper describes an adaptive QoS handoff priority scheme which reduces the probability of call handoff failures in a mobile multimedia network with a micro/picocellular architecture. The scheme exploits the ability of most multimedia traffic types to adapt and trade off QoS with changes in the amount of bandwidth used. In this way, calls can trade QoS received for fewer handoff failures. The call level and packet level performance of the handoff scheme are studied analytically for a homogeneous network supporting a mix of wide-band and narrow-band calls. Comparisons are made to the performance of the nonpriority handoff scheme and the well-known guard-channel handoff scheme.

In order to sustain relatively differentiated QoS over time-varying shared wireless medium with location-dependent errors, we propose in this paper a wireless fair scheduling algorithm which tries to both provide short-term fairness in the rate proportional guarantee sense and maintain a reasonable system throughput. Different implementation issues are discussed and performance is compared to alternative found approaches in the literature in which short term fairness is sacrificed for system throughput maximization

A scheme supporting voice and data calls with some grade of service (GoS)1 guarantee in mobile multiservice networks is proposed. In this system, voice calls have preemptive priority over data calls. Preempted data calls can wait in a queue for a random patience time after which they leave the queue. A data call can be preempted only if there is space left in the finite size queue. To assess the performance of this system, an analytical model is given and performance metrics such as call blocking, call dropping and call non-completion probabilities are investigated. Although this scheme is a generic model, it can be easily adapted to take into account the specific definitions of practical and commercial data service standards in wireless mobile networks such as GPRS or DECT. © J.C. Baltzer AG, Science Publishers.

Almost a decade ago, Singapore started crafting and implementing its IT2000 master plan to transform the city-state into an information-technology-based intelligent island. Since 1997, the main infrastructure of a high-speed ATM-based backbone network, called SingaporeONE, has been in place along with a host of commercial and governmental application service sites providing a plethora of online services. Because of its small size and extensive wired infrastructure, broadband access to homes and offices is currently provided via ADSL and cable modems. There is, however, interest in the use of wireless broadband communication technologies to access SingaporeONE, motivated primarily by its lower cost and faster deployment. In this article we describe some of our R&D activities motivated by the above interest to provide wireless broadband access to SingaporeONE. Specifically, we describe our study of LMDS, and the design and development of a wireless ATM LAN.

This paper presents a new distributed scheduling architecture for wireless ATM networks. Usually, in WATM scheduling architectures, a fixed order is defined among the different connections through their ATM service category (CBR>VBR>ABR>UBR). We argue that although this static priority is easier to implement, this type of precedence is not necessarily a good choice for the MAC layer. The MAC layer scheduling should define an order such that it uses efficiently the resources while providing quality of service (QoS) guarantees. In this spirit, our architecture delays (without violating their QoS) the real time connections in order to improve the performance of non real time connections.

Future wireless mobile multimedia networks are likely to adopt micro/pico cellular architectures. A consequence of using small cell sizes is the increased rate of call handoffs as mobile terminals move between cells during the holding times of the calls. In a network supporting multimedia services, the increased rate of call handoffs makes it very difficult for the network to guarantee the quality of service (QoS) promised to a call at setup. This paper describes a handoff priority scheme which reduces the probability of call handoff failures in such a mobile multimedia network. The impact of this admission control policy on packet level performance is studied analytically for a homogeneous network supporting a mix of wideband and narrowband calls

This paper proposes a MAC protocol which incorporates direct sequence spread spectrum (DSSS) technology and a hybrid automatic repeat request (ARQ) scheme with variable length protocol data unit (PDU) for efficient transmission in wireless home networks with error-prone indoor wireless channel. By using multiple code channels simultaneously, the protocol is capable of delivering high bit rates without sacrificing processing gain. The protocol combines reservations, time division duplexing and dynamic time division multiple access (TDD/DTDMA) to arbitrate the access of variable length packets from various appliances. A soft blocking prevention scheme is also developed to reduce the failure probability of reservation requests which are submitted in code division multiplexing (CDM) manner.

With the recent developments in the field of wireless hand-held mobile terminals, and the diversity of new services that are being introduced in wireless personal communication systems progressively, high bandwidth requirements are likely to be expected in the very near future. On the other hand, due to the inherent bandwidth scarceness on the air interface (spectrum limitations, etc), micro/picocellular architectures are likely to be the most attractive solution, because of the high frequency reuse they allow. As a direct result, the rate of call handoffs increases dramatically as now even users moving at a very low speed (walking) have a higher probability of moving between cells while a call is ongoing. In this paper, channel reservation based on the handoff probability of a call arriving in an adjacent cell is proposed as a more flexible and dynamic means of providing handoff priority in mobile micro/picocellular networks. A basic dynamic channel reservation scheme is described and shown to yield improvements in performance, notably in terms of blocking probability, dropping probability and call non-completion probability, over the well known guard channel scheme.