Distributed-queueing Request Update Multiple Access Research Articles

Supporting Real-Time Service in Packet-Switched Wireless Networks

The requirement of providing real-time data service by wireless networks is a critical issue in the design of current wireless networks. Distributed Queueing Request Update Multiple Access (DQRUMA) has been proposed as a demand assignment medium access control (MAC) protocol to efficiently control the medium sharing by multiple mobile users. With the help of a packet transmission policy, DQRUMA has a potential to provide QoS service for the time-constrained burst data traffic. In this article, we study the problem of providing real-time service to fixed-size packets with or without time constraints in wireless networks. In particular, we propose a novel scheduling scheme for the DQRUMA protocol to control the packet transmission in packet-switched wireless networks. We have conducted extensive simulation experiments to evaluate the performance of the proposed algorithm and to compare its real-time performance with those of other packet transmission policies. This study proves that the new algorithm is an efficient transmission policy for the DQRUMA to support real-time service in wireless networks.

Performance analysis of an enhanced DQRUMA/MC-CDMA protocol for voice traffic

The original distributed-queueing request update multiple-access (DQRUMA)/multicode code-division multiple-access (MC-CDMA) protocol was developed as a channel access protocol for wireless packet CDMA networks. This protocol has recently attracted considerable attention. We modify the original protocol, which was designed for data traffic only, to additionally accommodate voice traffic and call it the A-Protocol. We propose a new packet CDMA protocol that enhances the A-Protocol by improving the utilization of receivers in a base station and call it the E-Protocol. In the E-Protocol, an access request is attempted with a randomly chosen code at a request minislot. We analytically evaluate the performance of both protocols and compare analytical results with computer simulation. Analytical results agree well with simulation results.

Performance analysis of a multi-rate mobile in a wireless packet network

A cell in wireless packet networks with a variety of mobiles servicing multi-rate traffic is considered. The network system incorporates distributed-queueing request update multiple access for demand assignment, and multi-code CDMA protocol for multiple transmission in parallel without self-interference. One multi-rate mobile in the network is modelled as a discrete-time queueing system with a set-up time and batch service where the service batch size is a random variable depending on the present queue size. The probability distribution of the queue size at steady state, and the waiting time distribution are obtained. Mobiles in are a cell classified into several classes according to their transmitter capability, traffic characteristic and QoS requirement, and then the set-up time distribution of a mobile is obtained in each class. Finally, the analytic results are shown to match quite well with simulations.

A nonpreemptive priority-based access control scheme for broadband ad hoc wireless ATM local area networks

The DQRUMA (distributed-queueing request update multiple access) protocol has been considered as an access protocol for the BAHAMA (broadband ad hoc wireless ATM local area network). However, it cannot support the service discipline of integrated multimedia traffic since it does not include any priority and access control policy. In this paper, we propose a nonpreemptive priority-based access control scheme for the DQRUMA protocol. Under such a scheme, modifying the CSMA/CA protocol in the contention period supports many levels of priorities such that user mobility (handoff) can be supported in BAHAMA. Besides, the proposed transmit-permission policy and adaptive bandwidth allocation scheme provide various QoS (quality-of-service) guarantees while maintaining high bandwidth utilization. Simulations show that it provides a good performance in ad hoc wireless ATM LAN environments.

Channel access and interference issues in multi-code DS-CDMA wireless packet (ATM) networks

Multi-Code Direct-Sequence Code-Division-Multiple-Access (MC-CDMA) has been proposed as a flexible multiple access scheme for wireless packet networks that support a large variety of mobiles with different and even time-varying rates. Using MC-CDMA, traffic streams with significantly different transmission rates can be easily integrated into a unified architecture, with all the transmissions occupying the same bandwidth and having the same spread spectrum processing gain. In this paper, we address medium-access and interference issues in MC-CDMA wireless packet networks. For medium access, we propose and study Multi-Code CDMA (MC-CDMA) with Distributed-Queueing Request Update Multiple Access (DQRUMA) to form a unified bandwidth-on-demand fair-sharing platform for multi-rate wireless services. DQRUMA is an efficient demand-assignment multiple access protocol for wireless access and scheduling. Pseudo-Noise (PN) codes (primary codes) and optimal power levels are allocated to the mobiles on a slot-by-slot basis, and a Maximum Capacity Power Allocation (MCPA) criterion exploits the sub-code concatenation property of the MC-CDMA transmission. Simulation results show that the system provides close to ideal-access performance for multi-rate mobiles, both with homogeneous traffic characteristics and with a mix of heterogeneous traffic characteristics. Finally, we analyze the effects of MC-CDMA intercell interference on the reverse link (i.e., mobile to cell site) and investigate interference reduction by using the Maximum Capacity Power Allocation (MCPA) criterion. Our results show significant reduction in reverse-link MC-CDMA intercell interference is possible using the MCPA criterion.

An efficient demand-assignment multiple access protocol for wireless packet (ATM) networks

In a wireless packet (ATM) network that supports an integrated mix of multimedia traffic, the channel access protocol needs to be designed such that mobiles share the limited communications bandwidth in an efficient manner: maximizing the utilization of the frequency spectrum and minimizing the delay experienced by mobiles. In this paper, we propose and study an efficient demand-assignment channel access protocol, which we call Distributed-Queueing Request Update Multiple Access (DQRUMA). The protocol can be used for a wide range of applications and geographic distances. Mobiles need to send requests to the base station only for packets that arrive to an empty buffer. For packets that arrive to a non-empty buffer, transmission requests are placed collision-free by piggybacking the requests with packet transmissions. The simulation results show that even with the “worst possible” traffic characteristics, the delay-throughput performance of DQRUMA is close to the best possible with any access protocol. In addition, explicit slot-by-slot announcement of the “transmit permissions” gives the base station complete control over the order in which mobiles transmit their packets. This important feature helps the base station satisfy diverse Quality-of-Service (QoS) requirements in a wireless ATM network.