Coordinated Direct and Relay Transmission With NOMA and Network Coding in Nakagami-m Fading Channels

Abstract

Although the use of coordinated direct and relay transmission (CDRT) in non-orthogonal multiple access (NOMA) can extend the coverage, its duplicated transmission reduces the spectrum efficiency (SE) of NOMA. To improve the SE, we propose a spectrum-efficient scheme for NOMA-based CDRT over Nakagami-m fading channels. In this scheme, the base station (BS) connects with a cell-center user (CCU) directly while communicating with a cell-edge user (CEU) via a relay and the CCU. Then, the relay and the CCU use network coding to process and retransmit the signals sent by the BS first and the CEU later. Finally, the BS and the relay simultaneously broadcast downlink signals. We derive the closed-form expressions for the average SE, the user fairness index and the energy efficiency (EE) as well as the asymptotic average SE using both perfect and imperfect successive interference cancellation (SIC). Simulations verify the correctness of our theoretical analysis and the superiority of the proposed scheme in SE and EE.

A Coordinated Direct AF DF Relay-Aided NOMA Framework for Low Outage

“…All the aforementioned works [10], [13], [15]- [17], [21]- [24], [26], [27] have laid a solid foundation for the use of C-NOMA and CDRT to improve the FU's performance, but there has been little effort to to improve the NU's performance. Several multimedia-type applications impose a low outage QoS, and it might not be possible to satisfy NU's constraints using these CDRT approaches (they only guarantee a diversity of one at the NU [21]).…”

“…IoT-assisted NOMA CDRT was analyzed in terms of outage probability and ergodic sum capacity in [23]. In [24], the SE and user fairness index of CDRT NOMA were derived considering perfect and imperfect SIC at NU. Coordinated uplink transmission for cooperative NOMA system was studied in [25].…”

Energy Efficiency Optimization of Cognitive UAV‐Assisted Edge Communication for Semantic Internet of Things

“…Furthermore, with the large-scale use of mobile IoT devices, such as wearable devices, driverless cars, and intelligent terminals, the problem of making the GBS cover more communication terminals needs to be solved urgently. The coordinated direct and relay transmission (CDRT) system is investigated to extend the communication coverage in [2]. In order to improve the spectrum efficiency, the uplink and downlink transmissions are designed jointly via network coding.…”

Adaptive modulation based on steady-state mean square error for underwater acoustic communication

“…Multipath propagation and limited bandwidth place significant constraints on the achievable throughput of underwater acoustic communication (UAC) systems. The bandwidth efficiency is an important system indicator [6][7][8], to increase the bandwidth efficiency of UAC systems, adaptive modulation (AM) schemes, which have the ability to adjust modulation modes according to channel conditions, can be employed.The investigation on the application of AM to underwater acoustic communications has been limited in comparison to the extensive investigations for terrestrial radio communication. In [9], an AM scheme based on channel prediction is proposed, in which the channel state information (CSI) of future time is predicted with the estimated CSI of a previous time and then used to adjust the modulation mode.…”

“…Multipath propagation and limited bandwidth place significant constraints on the achievable throughput of underwater acoustic communication (UAC) systems. The bandwidth efficiency is an important system indicator [6][7][8], to increase the bandwidth efficiency of UAC systems, adaptive modulation (AM) schemes, which have the ability to adjust modulation modes according to channel conditions, can be employed.…”