Why user swapping could be the best coordination mechanism in a cellular network?

We propose a technique that can be used to improve the throughput offered to cellular users, in particular cell-edge users. Often, base stations (BSs) of different network operators are not co-located. Because of this, more spatial diversity is available by considering multiple cellular networks. Users who do not have a high SINR in their home network might see a much better SINR in another network because of the spatial diversity. Hence, to improve the performance of their cell-edge users, network operators can “swap” (exchange) them. In essence, we want to allow roaming between operators for other reasons than pure coverage. This paper aims at quantifying the gains that can be obtained by such swapping techniques. We propose a swapping scheme, “Operator-Based Swapping”, in which a central controller decides which users should be exchanged between two operators assuming the number of users served by an operator does not change. Although implementing such a centralized scheme would be difficult, it helps us to understand the potential gain of such a “swapping” technique. Our numerical results show that high throughput gains (e.g., 80%) are achievable for the 10% worst users for both operators if the two networks are spatially diverse. We then propose a second swapping technique, called “BS-Based Swapping”, that restricts the number of exchanged users to be equal on a pair of BS-basis. We believe that this scheme might be easier to implement. We compare the performance of this scheme under different configurations representing different levels of spatial diversity and allocated resources including time and frequency. Our numerical results show that this second swapping technique works almost as well as the first one. Our results show the potential of a technique based on a generalization of roaming as a mean to improve user performance.