Proportional bandwidth adjustment using BER ratios, in a two‐tier hierarchical NEMO system

Abstract

In this paper, we present a proportional bandwidth adjustment (PBA) scheme using bit‐error‐rate (BER) ratios in a two‐tier hierarchical NEMO system, composed of an access router (AR), mobile routers (MRs), and visiting mobile nodes (MNs). Depending on the location, an MN may use direct link to AR (Tier‐0) or indirect link to AR via MR (Tier‐1). To increase system utilization, sessions generated by high‐speed MNs in one tier are allowed to use a certain amount of free bandwidth in another tier. Since Tier‐1 traffic can be temporarily buffered at MR, to reduce the blocking probability of Tier‐0, the bandwidth between Tier‐0 and Tier‐1 can be proportionally adjusted based on BER. In other words, more bandwidth is allocated to the tier with smaller BER. For the purpose of performance evaluation, we build a mathematical model with 6D Markov chains to analyze session blocking probabilities, system utilization, and normalized goodput. Analytical results are validated through a simulation. Both results demonstrate that the proposed PBA can significantly reduce the session blocking probabilities and increase the overall normalized goodput when BER ratio between Tier‐0 and Tier‐1 is very different. Copyright © 2010 John Wiley & Sons, Ltd.