Concerning the collision and access failure which are very likely to occur when the intensity of the users' access increases, a random access packet-based strategy was proposed. The users were divided into several groups according to the strategy; certain sub-frames formed a super-frame to enable different users to send Uplink Synchronization Code (SYNC UL) to the corresponding sub-frame of super-frame when the users needed random access information, and based on it, priority was set for the users from different groups. Compared with the general strategy, packet-based strategy has greatly improved the success rate of the users' access, and grouping based on priority was adopted to ensure a higher success rate for advanced users. The theoretical analysis and simulation results show that the proposed packet-based strategy can significantly improve the system Quality of Service (QoS) and could be an effective measurement for decreasing the probability of collision in random access.%在用户接入强度大时,容易产生碰撞导致随机接入失败.针对这个问题,提出一种基于分组的随机接入策略.该策略将用户分为若干组,若干子帧组成一个超帧,用户进行随机接入时,在超帧对应子帧上发送上行同步码,在此基础上,为不同组别用户设定不同优先级.与一般不分组的情况进行对比,基于分组的随机接入策略提高了用户接入成功率,基于优先级的分组进一步保证了高优先级用户更高的接入成功率.理论分析和仿真结果表明,所提出的分组策略能够明显改善系统的服务质量,是一种有效降低随机接入碰撞概率的方法.
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