TCP-aware resource allocation in CDMA networks

ABSTRACT

TCP is the dominant transport protocol over both wired and wireless links. It is however, well known that TCP is not suitable for wireless networks and several solutions have been proposed to rectify this shortcoming. In this work, we explore cross-layer optimization of the rate adaptation feature of cellular networks to optimize throughput of a single long-lived TCP session. Modern cellular networks rate RF technology that allows them to dynamically vary the wireless channel rate in response to user demand and channel conditions. However, the set of data rates as well as the scheduler's rate adaptation policy are typically chosen to optimize throughput for inelastic applications. In order to optimize such a system for TCP, we propose a two state TCP-aware scheduler that switches between two chanrates as a function of the TCP sending rate. We develop a fluid model of the steady-state behavior of a TCP session in such a system and derive analytical expressions for TCP throughput that explicitly account for rate variability as well as the dependency between the scheduler and TCP. Using the model we choose RF layer parameters that, in conjunction with the TCP-aware scheduler, improve term throughput of a single TCP flow by 15.25%. We also compare our analytical results against those obtained from ns-2 simulations and confirm that our model indeed closely approximates TCP behavior in such an environment.

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INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.2 Network Protocols

General Terms:
Design, Performance

Keywords:
TCP throughput, cross-layer optimization, rate adaptation, wireless networks