Soft Handoff and Uplink Capacity in a Two-Tier CDMA System

TL;DR

This paper analyzes how soft handoff improves uplink capacity in a two-tier CDMA system with macrocell and microcell, showing a 20% capacity increase over hard handoff through analytical and simulation methods.

Contribution

It introduces exact and approximate analytical methods for calculating uplink capacity in a two-tier CDMA system with soft handoff, demonstrating significant capacity gains.

Findings

20% increase in user capacity with soft handoff

Approximate methods accurately estimate capacity

Soft handoff outperforms hard handoff in uplink capacity

Abstract

This paper examines the effect of soft handoff on the uplink user capacity of a CDMA system consisting of a single macrocell in which a single hotspot microcell is embedded. The users of these two base stations operate over the same frequency band. In the soft handoff scenario studied here, both macrocell and microcell base stations serve each system user and the two received copies of a desired user's signal are summed using maximal ratio combining. Exact and approximate analytical methods are developed to compute uplink user capacity. Simulation results demonstrate a 20% increase in user capacity compared to hard handoff. In addition, simple, approximate methods are presented for estimating soft handoff capacity and are shown to be quite accurate.