Journal of High Speed Networks

In this paper, we optimize the usage of both control and traffic channels of a CDMA system by switching the MAC states of a service. In particular, we find the optimal transition timers for a cdma2000 system supporting integrated voice and data traffic. This is achieved by optimizing a composite performance metric defined as a multi‐objective function of channel utilization, waiting time and the saving in the signalling overhead. First, we try to characterize wireless data as a mix of of Poisson‐distributed voice packets and Pareto‐distributed data packets, and study the effect of the composition of the mix and the shape parameter of Pareto distribution on the system performance. Then we derive analytical expressions for the composite performance metric with a goal to obtain the optimal values of expiration timers at which the MAC states should be switched such that the system performance is maximized. Since a closed form solution could not be obtained due to the transcendental nature of the analytical expression, simulation experiments are conducted to confirm the analysis.

In the future, we are likely to see a tremendous rise in mobile computing and communications as ubiquitous applications incorporate multimedia information. These mobile multimedia applications will have QoS requirements; resource provisioning algorithms utilize current system resource availability information to ensure that these applications meet their QoS requirements. Information collection algorithms collect and maintain current system resource information and are vital in performing efficient resource provisioning. In this paper, we present a novel information collection technique for mobile environments – the ABIC (aggregation‐based information collection) algorithm. This algorithm derives aggregate mobility from individual user mobility, then utilizes the aggregation to drive the information collection process and adjust the related parameters in the process. A feedback loop allows the information collection process to utilize feedback from the resource provisioning process in further decision making. We compare the ABIC approach to other proposed information collection algorithms under different workloads and mobility patterns. Our experimental results show that the aggregation based information collection algorithm exhibits superior performance under most mobility criteria and request patterns.

This paper presents results from the Cellular IP Project at Columbia University on Internet micromobility. Cellular IP complement Mobile IP with support for fast, seamless and local handoff control, and IP paging. We discuss the design, implementation and evaluation of the Cellular IP protocol using simulation, analysis and experimentation. We report on the ability of Cellular IP to offer seamless mobility for TCP and UDP applications operating in highly mobile environments. We present a comparison of a number of IP micromobility protocols using the Columbia IP Micromobility Software (CIMS) ns‐2 extension that supports separate programming models for Cellular IP, Hawaii and Hierarchical Mobile IP. We discuss simulation results to illustrate the performance of these micromobility protocols. The source code for CIMS and the Cellular IP experimental testbed are freely available from the Web (comet.columbia.edu/cellularip).

In this paper, we propose a mechanism that supports the high quality streaming and adaptation of stored, constant‐quality video across best‐effort networks. The difficulty in the delivery of such traffic over best‐effort networks is the fact that both the bandwidth required from the stream and the bandwidth available across the network vary considerably over time. Our proposed approach has a number of useful features. First, it uses the a priori information from the video stream to drive that adaptation policy. Second, it does not rely on any special handling or support from the network itself, although any additional support from the network will indirectly help increase the video quality. Third, it can be built on top of TCP, which effectively separates the adaptation and streaming from the transport protocol. This makes the question of TCP‐friendliness much easier to answer. Using actual MPEG encoded video data at multiple qualities, we show through experimentation that this approach provides a viable alternative for streaming media across best‐effort networks.