Research On The Optimal Access Control Algorithm In LTE Random Access

With the growing demand for internet access and high-speed data services, mobile communication technology has evolved from3G to4G. LTE(Long Term Evolution) as quasi-4G technology, high spectrum efficiency, low communication latency and high-speed data transfer rates, has become one of hotspots of the new mobile telecommunications technology. In LTE system, random access is an important part of the physical layer and the MAC layer, which process has a directly impact on the performance of the system capacity and access delay. In order to reduce access delay, how to dispose collision users is one of keys of LTE random access technology. We have done the following research work about the problem.1. Researched Pseudo Bayesian Algorithm based on the Optimal Access Control Algorithm. Pseudo Bayesian Algorithm can estimate the users of channel according to channel state, the paper first has analyzed convergence, stability and latency of Pseudo Bayesian Algorithm. Next, this paper has improved MFpBA--Dynamic Estimate Algorithm. When there were some collision state in channel, we set Nk+1=(Nk+1)/2. We have done this because it can expand adjustment range and make the estimate close to the actual faster. The Dynamic Estimate Algorithm can cut down the average delay time and adjustment time that system reached maximum throughput, at the same time it applied to variable load system.2. Proposed User Access Control Algorithm based on multichannel. There were two methods in multichannel, one was that Pseudo Bayesian Algorithm was used independently in each channel, another was that channel included new transmission channels and retransmission channels, Pseudo Bayesian Algorithm was only used in retransmission channels. Based on the second way, the paper has brought up User Access Control Algorithm, the new algorithm can availably reduce average latency.3. Proposed Adaptive Access Algorithm based on change the number of PRACH resources. In TD-LTE system, there are at most six PRACH resources, which can be multiplexed in frequency domain. PRACH Configuration Index decides the number of PRACH resources. First, we have done statistical analysis the users arrival rate of different times in a cell, and make a file of users arrival rate. Then, the eNodeB configured the value of PRACH Configuration Index that the eNodeB changed the number of PRACH resources, the user selected a resource at random from available PRACH resources to launch random access. Adaptive Access Algorithm can effectively reduce the probability of collision.