南通大学学报（自然科学版）

为了解决第六代移动通信系统的超大规模机器类通信场景中海量设备突发性并发接入导致的网络拥塞、接入冲突、成功率下降及能耗上升问题，提出一种基于接入类别限制辅助的随机接入方案。该方案首先根据实时请求接入的设备数量动态判定是否执行接入类别限制检查；当请求接入设备数量不超过最大前导码数量时，所有设备直接发起随机接入，否则设备需通过接入类别限制检查。通过检查的设备依据业务特性划分为时延敏感型与时延容忍型两类，并分别采用两步随机接入过程和四步随机接入过程，这两类设备共享同一前导码池。在满足设备接入时延约束的前提下，以最大化随机接入效率为目标，动态调整接入类别限制因子、前导码数量及某个设备被判定为时延敏感型设备的最优概率。仿真结果表明，当请求接入设备数量超过最大前导码数量时，所提方案的平均随机接入效率显著高于传统随机接入方案、结合两步-四步随机接入的方案及联合接入控制和资源分配方案；平均接入时延相较于传统随机接入方案降低约50%，且低于结合两步-四步随机接入的方案和联合接入控制和资源分配方案；平均能耗在四种方案中最低，且随设备数量增加的增长幅度最为平缓。该方案通过动态接入控制、差异化随机接入过程与共享前导码机制，有效缓解了高负载条件下的接入拥塞与冲突问题，提升了系统接入容量与资源利用效率。此外，通过引入不同最大重传次数条件下的平均随机接入效率对比分析，验证了所提方案在不同重传限制下仍能保持稳定的性能优势。

In ultra-massive machine-type communication scenarios for sixth-generation mobile communication systems， burst concurrent access from massive devices leads to network congestion， access collisions， reduced access success rates， and increased energy consumption. To address these issues， an access class barring (ACB)-assisted hybrid random access scheme is proposed.In this scheme， whether to perform an ACB check is dynamically determined based on the real-time number of devices requesting access. When the number of requesting devices does not exceed the maximum number of preambles， all devices initiate random access directly; otherwise， devices must pass an ACB check. The devices that pass the check are classified into delay-sensitive and delay-tolerant types according to their service characteristics， and they adopt the two-step and four-step random access procedures， respectively， while sharing the same preamble pool. Under the constraint of device access delay， the ACB factor， the number of preambles， and the optimal probability of a device being classified as delay-sensitive are dynamically adjusted to maximize the random access efficiency. The simulation results show that when the number of requested access devices exceeds the maximum number of preamble codes， the average random access efficiency of the proposed scheme is significantly higher than that of the traditional random access scheme， the scheme combining two-step - four-step random access， and the joint access control and resource allocation scheme. The average access delay is reduced by approximately 50% compared to the traditional random access scheme， and is lower than that of the scheme combining two-step to four-step random access and the joint access control and resource allocation scheme. The average energy consumption is the lowest among the four schemes， and the growth rate with the increase in the number of devices is the most moderate. Through dynamic access control， differentiated random access procedures， and shared preamble mechanism， the proposed scheme effectively alleviates access congestion and collision problems under high-load conditions， thereby improving system access capacity and resource utilization efficiency.Furthermore， by introducing a comparative analysis of average random access efficiency under different maximum retransmission times， it was verified that the proposed scheme can still maintain stable performance advantages under different retransmission constraints.