QoS-based device-to-device communication schemes in heterogeneous wireless networks

This study considers spectrum sharing problems in the heterogeneous wireless networks where different device-to-device (D2D) users coexist with the cellular users. The authors propose a novel scheme, called `spectrum partition-based D2D transmission´ (SPDT), to improve spectrum efficiency of the D2D and cellular networks. In SPDT, the D2D users assist the cellular transmissions to gain some spectrum released from the cellular system. Then, the obtained spectrum is divided into several frequency bands and each band is assigned to a different D2D pair for its data transmission. Under the quality-of-service (QoS) constraints of both the D2D and cellular users, the authors exploit the tradeoff in the power allocation of the D2D transmitters and show that the number of the allowed accessing D2D pairs can be maximised by optimising the D2D transmitters power for SPDT. For comparison the power optimisation problem is also investigated with the objective of maximising the number of allowed users accessing D2D pairs in the power control scheme, called `underlay D2D transmission´ (UDT). This is where the D2D users access the spectrum being used by the cellular users with power control while ensuring that the QoS of the cellular transmissions is satisfied. Finally, the simulation results show evident performance gains of the proposed SPDT scheme over the UDT scheme.