Multiple Antenna Reception for Random Access Channels, Part I: Detector Structures and Performance Analysis
01 January 2004
The system design of the Random Access Channel (RACH) entails three phases: (a) detection algorithm design, (b) dimensioning of resources per cell, (c) resource optimization. In this paper, the design of optimal detection strategies for base stations with antenna arrays is considered. This is a challenging problem given pragmatic constraints on implementation complexity. The resulting solutions depend on the spatio-temporal channel characteristics assumed for the deployment environment. In this respect, solutions of various complexities, starting from the derivation of optimal detector structure, to other simplified detection structures, are presented. Detectors tailored to different channel scattering conditions are derived and analyzed in terms of the probability of detection and false alarm. The analysis reveals design tradeoffs that are subsequently exercised to derive practical and close to optimal detector structures. One of these approaches, the fixed-beam detector, is extended so that it can handle non-white interference. Extensive link- level simulation results are presented that demonstrate the improvements obtained by spatial processing. A companion paper (Part II) will present system level results that reveal the true tradeoffs between the antenna configurations by considering the MAC-c protocol layer, and analysis of throughput and delay metrics.