Opportunistic Multicast Scheme Research Articles

A Range-Division User Relay Selection Scheme and Performance Analysis in NOMA-based Cooperative Opportunistic Multicast Systems

The original user relay (UR) selection scheme of non-orthogonal multiple access-based cooperative opportunistic multicast scheme, which realizes inter-group cooperation between two multicast groups, ignores the distribution trend of candidate UR in the cell and adopts fixed efficient relay selection range (ERSR) to select UR. It results in high UR selection ratio. Then the coverage efficiency, defined as the ratio of successfully received users to URs, is low. To tackle this problem, a range-division user relay (RDUR) selection scheme is proposed in this paper. Firstly, it divides the circular coverage range of base station into several continuous annular areas (AAs). Secondly, different ERSRs are assigned to unsuccessfully received users in different AAs. Under different ERSR assignments, the performances of UR selection ratio and coverage ratio are analyzed. Lastly, the radius set of ERSR that optimizes system coverage efficiency is used to perform UR selection. From simulation results, with different radius sets, analytical results of UR selection ratio and coverage ratio match well with their simulated ones. It is proved that ERSR allocation affects UR selection ratio and coverage ratio. With RDUR scheme, coverage efficiency increases by at least 14% and capacity efficiency has also been improved.

Multicast Resource Allocation with Opportunistic Scheduling in LTE Networks

Long Term Evolution (LTE) and beyond networks offer high bitrates with low latencies which makes them the best choice to handle the growing demand on multicast mobile services such as video streaming, and news broadcasting. In Conventional Multicast Scheme (CMS), the gain of multicast is exploited by transmitting data to all users simultaneously using the rate of Worst Channel Gain (WCG), which wastes network resources. In this paper, to better balance the tradeoff between the multicast gain and multiuser diversity, we propose a mechanism to select a threshold to split users into two subgroups and exploits the Opportunistic Multicast Scheme (OMS) to transmit the data. Simulation results show that the proposed mechanism improves the multicast performance in terms of increased throughput, decreased delay and Packet Loss Ratio (PLR) compared to existing mechanisms from the literature.DOI: http://dx.doi.org/10.5755/j01.eie.24.5.21850

NOMA-Based Cooperative Opportunistic Multicast Transmission Scheme for Two Multicast Groups: Relay Selection and Performance Analysis

The orthogonal frequency division multiple access (OFDMA)-based cooperative multicast (CM) technology realizing the intra-cooperation of multicast group (MG) has improved the performance in throughput and coverage. In the MG scenario, users are uniformly distributed. Due to the small effective transmission range of relay user (RU), the cooperation is hindered, which limits the performance of CM. Therefore, non-orthogonal multiple access (NOMA)-based two MGs joint cooperative opportunistic multicast scheme (termed as COM-NOMA) is proposed. In COM-NOMA scheme, two MGs are served as one quasi-MG. First, on the same frequency band, base station (BS) opportunistically multicasts the superposition signal, which is formed by two MGs’ signals, to the users with good channel conditions in the two MGs using NOMA way. Second, some successfully receiving users are selected as RUs. The superposition signal is forwarded to the other users by Device-to-Device multicast way. Then, according to the coverage ratio of BS and the decode condition of NOMA, the signal to interference and noise ratio threshold for RU selection is given. Finally, the spectral efficiency of COM-NOMA is analyzed and the approximate expression of system coverage ratio is derived. The simulation results show that, spectral efficiency at unit transmit power (spectral efficiency per watt) and system coverage ratio is improved in comparison with other OFDMA-based CM schemes.

Transmission Rate Scheduling and Stopping Time for Time-Sensitive Multicast Stream Traffic in Cellular Networks

Opportunistic multicast schemes for time-sensitive stream traffic are studied for cellular networks where erasure coded packets are transmitted over discrete-time quasi-static forward-link fading channels. Assume that to successfully decode a transmitted stream fragment, it suffices that one receives k packets from the fragment. Two important issues are thus raised on when to stop transmitting a fragment and how to minimize the stopping time (ST) through transmission rate scheduling. Based on available channel state information and scheduled history, we tackle them particularly for small k required for short latency. If the distribution of IID channel states is available, the scheme is to compute and use the optimal constant transmission rate and minimum fixed ST subject to a reliability constraint. We show that the minimum ST grows with the logarithm of multicast group size. If channel state information is available, we propose to minimize random ST through selecting each optimal instantaneous transmission rate for a utility function. The utility function is specifically designed to exploit system transient states and dynamics. Results show that the scheme with an exponential weighted residual work achieves the least mean ST but the scheme maximizing instantaneous effective sum throughput has an edge of low complexity.