Cross-layer analysis of the random access mechanism in Universal Terrestrial Radio Access

In 3GPP Universal Terrestrial Radio Access, a user equipment uses the Random Access Channel (RACH) for uplink transmission if it does not have a pre-established dedicated channel. RACH is a contention-based transport channel in which access control and open-loop power control functionalities are provided under the interactions between Medium Access Control (MAC) and physical layers. This paper develops a Markov chain model to analyze complex cross-layer interactions in RACH procedures, which is crucial to understanding the RACH performance. Besides, the Markov chain accurately describes the time-synchronized RACH behavior in slot level. The presentation of this time-synchronized behavior is simplified by merging multiple sub-states, each of which corresponds to a slot delay, into a single state. Finally, the proposed model analytically evaluates the RACH performance in Rayleigh fading channels in terms of throughput and delay.