Research On Mobile Random Access

While in the process to the direction of the communication with more data and IP, more and more data will be transmitted through random access channels. Random access will be much more important in mobile communication networks day by day. So, we should study and improve the present random access schemes.In present mobile communication systems or standards, random access adopt re-transmission schemes, it is a blank field in study for random access without retransmission. But we think, when using UDP protocol, it i s not essential to make affirmation and retransmission, so we can adopt random access schemes without retransmission.Therefore, this article is about to study and improvement of the random access with two directions. One is slotted-ALOHA without retransmission, while another is slotted-ALOHA with retransmission. The main contributions are in three field s.(1) In this paper, slotted-ALOHA without retransmission is studied, and dual-transmission r andom a ccess s cheme i s p roposed t o u se i n 1 ight 1 oad zone o f mobile communication. We derive the success ratio and throughput rate in ideal and actual channels. The results and simulations show, for same specifications, this scheme can decrease frequency resources needed and improve the resisting ability against channel low quality comparing with traditional slotted-ALOHA.(2) In respect of slotted-ALOHA with retransmission, we prove that the return point of the channel output figure is the best working point of the channel, and the success ratio at this position is 0.368, then give the methods for detecting success ratio by station. On the basis of these, we propose the slotted-ALOHA with station control s cheme for r andom a ccess. In t his s cheme, t he s tation c ontrol t he d egree o f retransmission backoff according to the success ratio detected, so the channel working point could be keep at the best position. Analysis and simulations show this scheme is applicable, and can improve the random access performance to ideal boundary.