The Omitted Dimension: Exploiting Multiuser Diversity in Multi-Radio Access Technology Data Cellular Communication Systems

Abstract

Performance of cellular communication systems is typically enhanced by leveraging the three dimensions of system transmission bandwidth, area frequency reuse, i.e. system access point (AP) density, and spectral efficiency of employed radio air interface, referred to as the radio access technology (RAT). In particular, refined RATs are continuously introduced to compensate for limited spectrum availability and restrictions on system AP densification in cellular communication systems. While the performance of cellular communication systems is maximized by employing a single RAT providing maximal spectral efficiency, varying capabilities of user equipment compels the co-deployment of multiple RATs in cellular communication systems and entails fragmenting system radiofrequency resources between co-deployed RATs. Nevertheless, the inefficient structuring of multi-RAT systems as independently operated collocated single-RAT subsystems results in unbalanced system loading, suboptimal spectrum utilization, and the omission of multiuser diversity as a performance enhancement dimension in multi-RAT systems. The omitted dimension of multiuser diversity is exploited in this paper, through multiple means and techniques, to further enhance the performance of multi-RAT data cellular communication systems. Unifying the architectural structure of multi-RAT systems is proposed to eliminate the redundant duplication of radio access network functions and elements, reduce system deployment costs and operational complexity, improve system scalability, and enable the joint execution of non-radio transmission functions for all co-deployed RATs. By fully exploiting system multiuser diversity, the joint allocation of system radiofrequency resources under autonomous spectrum assignment is shown to substantially enhance the performance of all employed RATs, in addition to the overall performance of multi-RAT systems, without extending any of the three typical performance enhancement dimensions of cellular communication systems.INDEX TERMS Cellular communication systems, multi-radio access technology systems, radio access networks, radio access technologies, radio resource allocation, spectrum management, user access, user equipment. a cellular communication system thus requires employing the most spectrally efficient RAT to connect all system users. However, large variations in UE capabilities compels the co-deployment of multiple RATs to maintain user connectivity in cellular communication systems [23]-[25]. Nevertheless, the design and structuring of classical cellular communication systems assumes the employment of a single RAT to connect system users [1]- [3]. Such an assumption implies fixed user diversity and effectively eliminates the feasibility of exploiting system multiuser diversity as a performance enhancement dimension in multi-RAT cellular communication systems. On the other hand, structuring multi-RAT systems as groups of independently operated collocated single-RAT subsystems leads to a multitude of inefficiencies in system o...