This paper proposes a new multiuser communication model in which a source with broadcast capabilities wants to transmit two different messages to two different destinations in the case that no direct links between the source and its destinations. In this channel model, two parallel half-duplex relays are used to extend the transmission. For this communication model, an outer bound to the achievable capacity is initially derived. Then, two distinctive transmission schemes are characterized such that the source can transmit to the two destinations. In each scheme, the transmission is split into two phases. Specifically, in the first phase, the source can broadcast different messages to the two relays. Then, in the second phase, the two relays can forward the source’s signals into their destinations. Based on the transmission on each scheme, the achievable rate region is characterized. Further, we derive the optimal duration of each phase. The theoretical analyses are followed by many numerical examples that compare between the different transmission techniques and also show the points at which the capacity is achieved.

本文提出了一种新的多用户通信模型，其中具有广播功能的源希望在源与其目标之间没有直接链接的情况下，将两个不同的消息发送到两个不同的目标。在此信道模型中，两个并行的半双工中继器用于扩展传输。对于此通信模型，最初会得出可实现容量的外部界限。然后，表征两个独特的传输方案，以使源可以传输到两个目的地。在每种方案中，传输都分为两个阶段。具体来说，在第一阶段，源可以向两个中继广播不同的消息。然后，在第二阶段，两个中继可以将源的信号转发到其目的地。根据每个方案的传输情况，表征了可达到的速率区域。此外，我们得出每个阶段的最佳持续时间。理论分析之后是许多数值示例，这些示例对不同的传输技术进行了比较，并显示了达到容量的要点。