Analysis and Design of SCMA-Based Hybrid Unicast-Multicast Relay-Assisted Networks

Abstract

This paper studies a multi-user network model based on sparse code multiple access (SCMA), where both unicast and multicast services are considered. In the direct transmission scheme, the communication between the base station (BS) and the users is completed with one stage, in which the relay is inexistent. In the two-stage cooperative transmission scheme, any number of relays are placed to improve the reliability of wireless communication system. The BS broadcasts the requested message to users and relays in the first stage, and the successful relays forward the message to unsuccessful users in the second stage. To characterize the performance of these two schemes, we derive the exact and approximate expressions of average outage probability. Furthermore, to take full advantage of the cooperative diversity, an optimal power allocation and relay location strategy in the high signal-to-noise ratio (SNR) regime is studied. The outage probability reaches the minimum value when the first stage occupies half of the total energy consumed. Simulation and analysis results are presented to demonstrate the performance of these two schemes. The results show that the two-stage cooperative scheme effectively reduce the average outage probability in SCMA network, especially in the high SNR region.

A Survey on Non-Orthogonal Multiple Access: From the Perspective of Spectral Efficiency and Energy Efficiency

“…Many works investigated the NOMA relaying, including the UE and dedicated relays, in numerous scenarios targeting the SE and EE enhancement [97][98][99][100][101][102][103]. The SCMA was recently considered in cooperation with relaying [104][105][106]. In particular, the authors of [105] proposed a joint optimization of power allocation, codebook assignment, and subcarrier pairing to maximize the sum rate in an SCMA-based UL network, while the outage probability analysis for UEs in an SCMA relaying system was reported in [106].…”

Medium Access-Based Scheduling Scheme for Cyber Physical Systems in 5G Networks

“…F-OFDM also offers resource allocation flexibility as bandwidth can be parted into variable sized subbands for different applications by applying dynamic numerology, as compared to the persistent numerology of OFDM for the whole spectrum [12]. The time-frequency resource sharing feature of code division multiple access (CDMA) and the division of bandwidth into subbands for multiple users feature of orthogonal frequency division multiple access (OFMDA) are combined to achieve sparse code multiple access (SCMA) mechanism for air interface in 5G [13]. The idea of resource sharing via code domain was pitched quite some time ago in [14].…”

Resource Allocation for SCMA-Based IoT Systems With Layered Multicast

“…Motivated by this fact, reference [22] proposed an analytical approach to obtain a tight upper bound of the BER for the multicast SCMA system. The work in [23] proposed a cooperative multicast scheme for SCMA networks. However, reference [22], [23] focused only on nonlayered multicast, which does not consider the heterogeneity among multiple receivers.…”

“…The work in [23] proposed a cooperative multicast scheme for SCMA networks. However, reference [22], [23] focused only on nonlayered multicast, which does not consider the heterogeneity among multiple receivers. As different receivers have heterogeneous and time-varying channel conditions, nonlayered multicast that uses fixed rate and coding schemes cannot better serve all multicast receivers simultaneously [24].…”