Cross-Layer Modeling of Randomly Spread CDMA Using Stochastic Network Calculus

TL;DR

This paper introduces a stochastic network calculus-based method to analyze the maximum traffic capacity of multiuser CDMA networks under QoS constraints, considering physical layer adaptations and channel variability.

Contribution

It presents a novel cross-layer modeling approach combining stochastic network calculus and large system analysis for CDMA with QoS considerations.

Findings

Delay requirements significantly reduce capacity.

Higher user load decreases traffic carrying capacity.

Adaptive modulation improves capacity under QoS constraints.

Abstract

Code-division multiple-access (CDMA) has the potential to support traffic sources with a wide range of quality of service (QoS) requirements. The traffic carrying capacity of CDMA channels under QoS constraints (such as delay guarantee) is, however, less well-understood. In this work, we propose a method based on stochastic network calculus and large system analysis to quantify the maximum traffic that can be carried by a multiuser CDMA network under the QoS constraints. At the physical layer, we have linear minimum-mean square error receivers and adaptive modulation and coding, while the channel service process is modeled by using a finite-state Markov chain. We study the impact of delay requirements, violation probability and the user load on the traffic carrying capacity under different signal strengths. A key insight provided by the numerical results is as to how much one has to back-off from capacity under the different delay requirements.