Implementation of the low latency random access detector for 4g cellular system

Abstract

This dissertation presents a hardware design of high throughput, low latency preamble detector for 3GPP LTE physical random access channel (PRACH) receiver. The main objective of this research is to reduce the detection latency time of LTE random access preamble detection procedure. In typical configuration of LTE system, the network latency time is approximately 80ms for "Idle to Connected mode" and 14.5ms for "Dormant to Active state" transit. And physical layer related latency consumes 8.5ms among these uplink network latency. Therefore, we can improve the network latency performance by reducing the preamble detection latency time. Reducing the preamble detection time also can extend eNB`s ability of supporting various cell size. For larger cell, computational complexity for preamble detection will be increased due to increased number of used root sequences. Therefore, efficient and low latency preamble detector can enable eNB to support these larger cell without performance degradation. Reducing detection latency time also affects the PRACH burst period time and this means an eNB can locate PRACH subframes more frequently, so that the random access capacity of eNB can be increased. In this dissertation, we will show the preamble detection flow with analytical formulation and analyze the effect of Doppler frequency on preamble detection. The preamble detection performance using Zadoff-Chu (ZC) sequence is degraded due to Doppler effect and we using power delay profile (PDP) combining method to overcome this problem. The presented PRACH receiver exploits pipelined structure to improve the throughput of power delay profile (PDP) generation which is executed multiple times during preamble detection procedure. In addition, to reduce detection latency, we propose instantaneous preamble detection method. The proposed preamble detection method can detect all existing preambles directly and instantaneously from power delay profile (PDP) output. Therefore, preamb...