A benchmark for D2D in cellular networks: The importance of information

Many new mobile applications create traffic among cellular users. We define intra-cellular traffic as the traffic from one cellular user to another user in the same cellular network. This type of traffic introduces new challenges for cellular network operators. Most work in the literature focuses on the possibility to utilize the direct links between those users, if they are close to each other (this is called device-to-device (D2D) communication), to by-pass the base station. However, implementing D2D is not easy, especially because detecting that a traffic is intracellular is difficult. In this paper, we assume that we know how to detect if a traffic is intra-cellular or not and focus on designing a type-aware scheduler (i.e., a scheduler which has the information on the type of traffic) in a case where direct communications between users is not enabled. This scheduler can be seen as the benchmark against the case where direct communications are allowed. We show that performance gain can be obtained by jointly scheduling the uplink and downlink with respect to the case where the scheduler is blind to the types. We show for a homogeneous network that when the traffic types are known to a scheduler, a significant performance gain (up to 28%) can be achieved compared to the case where the traffic types are not known. We also analyze heterogeneous networks that consist of macro cells and small cells and show that up to a 36% performance gain can be obtained by performing type-aware user association jointly with user scheduling.