A quantitative analysis of the throughput gains and the energy efficiency of multi-radio transmission diversity in dense access networks

Densification of mobile network infrastructure and integration of multiple radio access technologies are important approaches to support the increasing demand for mobile data traffic and to reduce energy consumption in future 5G networks. In this paper, the benefits of multi-radio transmission diversity (MRTD) are investigated by modelling the radio access link throughputs as uniform- and Rayleigh-distributed random variables and evaluating different user schedulers and resource allocation strategies. We examine different strategies for the allocation of radio accesses to individual users ranging from independent utilisation of the radio accesses to MRTD-enabled schemes. The schemes are compared by considering the statistics of the system throughput and energy consumption of the mobile devices. It is shown that MRTD can increase the throughput significantly through two types of diversity gain: Firstly by having multiple radio accesses to choose from for each user and secondly by having more available users to choose from for each radio access. The increased throughput also helps to reduce the energy consumption per bit, but this comes at a cost of increased energy consumption for channel measurement and reporting.