Partial-information multiple access (PIMA) is an orthogonal multiple access (OMA) uplink scheme where time is divided into frames, each composed of two parts. The first part is used to count the number of users with packets to transmit, while the second has a variable number of allocated slots, each assigned to multiple users to uplink data transmission. We investigate the case of correlated user activations, wherein the correlation is due to the retransmissions of the collided packets, modeling PIMA as a partially observable-Markov decision process. The assignment of users to slots is optimized based on the knowledge of both the number of active users and past successful transmissions and collisions. The scheduling turns out to be a mixed integer nonlinear programming problem, with a complexity exponentially growing with the number of users. Thus, sub-optimal greedy solutions are proposed and evaluated. Our solutions show substantial performance improvements with respect to both traditional OMA schemes and conventional PIMA.

翻译：部分信息多址接入（PIMA）是一种正交多址接入（OMA）上行链路方案，其中时间被划分为帧，每帧由两部分组成。第一部分用于统计有待发送数据包的用户数量，第二部分则包含数量可变的分配时隙，每个时隙被分配给多个用户用于上行数据传输。我们研究了用户激活具有相关性的情况——这种相关性源于冲突数据包的重传，并将PIMA建模为部分可观测马尔可夫决策过程。基于活跃用户数量以及历史成功传输与冲突的信息，对用户至时隙的分配进行优化。该调度问题本质上是混合整数非线性规划问题，其复杂度随用户数量呈指数增长。因此，我们提出并评估了次优贪心解决方案。实验表明，我们的方案相较传统OMA方案及常规PIMA均取得了显著的性能提升。