Duplexing, resource allocation and inter‐cell coordination: design recommendations for next generation wireless systems

Abstract

Coexistence of different access technologies, hierarchical cellular deployment, a wide variety of data services, requirements for transparent operation across different technologies, adaptivity to varying network conditions and mobility and quality of service (QoS) constraints introduce a number of challenges in the design of future generation systems and the specification of new air interfaces, such as efficiency and flexibility in the utilization of spectrum, dynamic resource allocation and exploitation of the multiuser diversity and reconfigurable interference management and inter-cell coordination. In this paper, three critical issues for the design of next generation systems are addressed: (i) duplexing, (ii) scheduling and resource allocation and (iii) interference and inter-cell coordination. A number of research directions are presented, which constitute promising potential candidates for next generation systems specification.

Physical-layer design for next-generation cellular wireless systems

“…This can potentially exploit frequency diversity better than frequency hopping because of coherent combining across carriers (as opposed to achieving frequency diversity through coding in the frequency hopping case) for low rate transmissions or through optimum assignment of users to tones. Furthermore, with frequency reuse, the relative gains obtained from improved signal-to-interference-plus-noise ratio (SINR) characteristics on the downlink do not overcome its inherent spectral inefficiency [1]. This observation provides additional motivation for universal frequency reuse.…”

“…We propose to go beyond the paradigm of using either FDD or TDD by proposing a new duplexing scheme called band switching that blends the best characteristics of each [1]. Given paired spectrum blocks, instead of reserving a block for uplink and the other for downlink, we alternate their use every T sec, as depicted in Figure 2.…”

Making smart use of excess antennas: Massive MIMO, small cells, and TDD

“…This enables some form of implicit cooperation between all devices in the network which does not necessitate any form of data or CSI exchange. Moreover, this scheme is fully distributed, easily scalable, and realizes the additional benefi ts of TDD, such as reduced latency, the ability to operate in unpaired frequency bands, and the support of asymmetric traffi c [4]. We also consider a variant of the TDD protocol, called reverse TDD (RTDD).…”

“…Apart from that, TDD is not only the key enabler for exploiting channel reciprocity, but it also has several other advantages over FDD which are summarized here for completeness (see, e.g., [4] for more details). In contrast to FDD, TDD does not require DL feedback of CSI from the UEs, which reduces latency.…”

“…Third, more sophisticated duplexing schemes could be considered. For example, an attractive alternative to coTDD is band switching duplexing [6] (see also [4]). In this scheme, both tiers operate simultaneously on two frequency bands over which they apply TDD in reversed orders.…”