On TDMA Optimality in Locally Connected Networks with no CSIT

In this work, we study scenarios of wireless networks where using simple Time-Division-Multiple-Access (TDMA) is optimal if no channel state information is available at the transmitters (no CSIT). We consider single-hop locally connected interference networks where each transmitter is connected to the receiver that has the same index as well as L succeeding receivers. The considered rate criterion is the per user Degrees of Freedom as the number of transmitter-receiver pairs goes to infinity. For the case when L = 1, it was shown in previous work that TDMA is optimal, even if each message can be available at multiple transmitters and linear cooperation schemes are allowed. Here, we extend this conclusion to the case where L = 2, by proving optimality of TDMA in this case as well. We then study the problem for general values of L without allowing for cooperative transmission. We prove optimality of TDMA when each transmitter is serving the receiver with the same index, and finally conjecture based on an example that the same conclusion applies even if each receiver can be served by any single transmitter connected to it.