In the process of LTE-R random access, the user's access request may surge in a flash. Excessive access request and limited access resources would increase the collision in accessing, thus resulting in significant increase of user-access failure rate. In accordance with the characteristics of random access process in LTE-R communication system, the two-division Preamble is used to realize the priority random access algorithm. This algorithm divides different priority levels for high-speed railway users and ordinary users, so that they can get different access effect when accessing. Matlab simulation results indicate that the proposed algorithm is fairly good in performance, and could ensure higher system throughput when the high-speed railway users arrive during the whole random access process, and also reduce the access-failure rate and access delay of high-speed railway users, thus to fairly guarantee the QoS.%在LTE-R随机接入过程中,用户的接入请求会在瞬时激增.过大强度的接入请求和有限的接入资源使得接入时的碰撞增加,导致用户接入失败率明显升高.针对LTE-R通信系统随机接入过程中的特点,采用二次划分Preamble实现区分优先级的随机接入算法.该算法为高速铁路用户与普通用户划分不同的优先级,使二者在接入时获得不同的接入效果.Matlab仿真的验证结果显示,所提算法性能较好,能够使高速铁路用户到达时的系统通过量更高,并降低高速铁路用户的接入失败率和接入时延,较好地保障QoS.
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