Mingming Li

Resource Allocation with Subcarrier Cooperation in OFDM-Based Wireless Multicast System

In this paper, we investigate resource allocation issue in OFDM-based wireless multicast system and joint subcarrier and power allocation scheme is proposed. The optimal solution of the combinable allocation has high computational complexity, so the solution is divided into two steps. In the first step, the subcarriers are allocated to the multicast services, and all the users that have subscribed to one service share the same subcarriers. In order to increase the system capacity, a subcarrier cooperation and user grouping method is proposed. To further lower the computational complexity, a simplified method is derived. In the second step, the water-filling method is adopted to get further capacity improvement. The simulation results show that the proposed scheme performs better than the existing schemes, and the proposed simplified scheme can get a similar performance. Besides, the resource allocation schemes with multi-dimension water-filling allocation notably outperform the schemes with equal power allocation.

Round-robin resource sharing algorithm for device-to-device multicast communications underlying single frequency networks

Device-to-device (D2D) multicast communication is a useful way to improve the communication efficiency of user equipments which are located close to each other. In this paper, the frequency resource sharing problem of D2D multicast communications underlying single frequency network (SFN) system is investigated. Firstly, to avoid the interference between D2D and cellular communication and without consuming more frequency resources, we assume that D2D multicast groups do not share frequency with cellular user equipments (CUEs) in the same SFN, but reuse frequency with CUEs in other SFNs. Then, according to a pre-setting threshold of signal to interference ratio (SIR) of D2D communication, a reuse safe distance is confirmed. Finally, a round-robin resource allocation algorithm is proposed. Simulation results show that the proposed resource sharing algorithm can significantly reduce the outage probability of both D2D and cellular communication and enhance the throughput of system.

Adaptive user selection of opportunistic multicast scheduling in wireless networks

In this study, an adaptive user selection of opportunistic multicast scheduling system (OMS-AUS) scheme is proposed to improve the system throughput performance of opportunistic multicast scheduling system. Different from the previous literatures, the user selection ratio would no longer be a constant, but would vary as the number of users that have not received multicast bits changes, which can exploit the system transmission ability better. The objective is to obtain the optimal values of user selection fractions. (i) For the case without instantaneous channel state information (CSI), a channel gain distribution-based OMS-AUS is proposed. Firstly, a system throughput matrix (STM) is formulated to imitate the user grouping process. Secondly, the value of each element in STM is derived according to the channel gain distribution. Finally, by fully searching the elements in STM, the optimal solution is obtained. To reduce the computational complexity, a suboptimal heuristic searching scheme is also proposed. (ii) For the case with instantaneous CSI, an improved approach based on both the channel gain distribution and instantaneous CSIs is proposed. Simulation results show that both of the two proposed approaches can obtain better performance compared to the existing schemes.

Feedback load reduction scheme in OFDM-based wireless multicast systems

To reduce the feedback load of OFDM-based wireless multicast systems, an opportunistic feedback scheme (OFS) is proposed. OFS aims to only feed the key channel gains that can significantly affect the system throughput back to the base station (BS). By mathematical derivation, the key channel gains are proved to belong to a channel gain interval, which can be estimated by a proposed statistical method. Simulation results show that OFS can significantly reduce the feedback load of OFDM-based multicast system, while remaining 99% multicast throughput performance compared with the full feedback scheme. Besides, the channel fading type of the BS-user link is not required, which would be more realistic.

Round-Robin Resource Sharing Algorithm for Device-to-Device Communications Underlying SFN System

In this paper, the resource sharing problem of device-to-device (D2D) communications underlying evolved multimedia broadcast multicast service (EMBMS) system is investigated, and a novel round- robin resource sharing algorithm (RRSA) is proposed. To avoid the interference between D2D user equipments (DUEs) and cellular user equipments (CUEs) without consuming more frequency resources, in this study, we assume that DUEs do not share frequency with CUEs in the same single frequency network (SFN), but reuse frequency with CUEs in other SFNs. The contribution is threefold: 1) D2D communication is introduced to the SFN in EMBMS system for the first time, 2) the system performance is significantly improved without additional frequency resource costing, and 3) the QoS requirement of high level user is ensured. Simulation results show that the proposed resource sharing algorithm can significantly reduce the outage probability of D2D receivers and enhance the throughput of system.

Outage Analysis of Opportunistic Cooperative Multi-Antenna Multicast Based on Space-Time Coding

Two Opportunistic Multi-antenna Relay Selection (OMRS) strategies are proposed and analyzed in Decode-and-Forward (DF) relay networks for cooperative multicast using space time codes, assuming multiple antennas are available at the relay nodes. These two strategies select the best relay based on (i) maximizing the average SNR and (ii) maximizing the minimum SNR respectively. The closed-form expressions of multicast outage probability for the two strategies are studied over Rayleigh fading channel. Simulations are provided to verify the correctness of the theoretical analysis. Our multicast outage probability results reveal that OMRS based on maximizing the minimum SNR is outage-optimal among multi-antenna relay selection schemes and approaches the space time codes scheme. Moreover, it can be found that compared with previous single-antenna Opportunistic Relaying (OR) scheme, OMRS brings remarkable performance improvement obtained from maximum ratio combining (MRC) and space-time coding, which proves that multiple antennas at the relays could provide more array gain and diversity gain.

Performance Analysis for Decode-and-Forward Two-Way Relay Networks with Limited Feedback Beamforming

In this paper, we study the performance of fixed decode-and-forward (DF) two-way relay cooperative networks with multi-antenna sources employing limited feedback beamforming (LFBF) for signal transmission. The closed-form expressions for the overall outage probability and sum symbol error rate (SSER) are derived using the moment generation function (MGF) of the signal- to-noise-ratio (SNR) at the relay. Subject to total power constraint, we also explore an optimal power allocation scheme between sources and relay to minimize the system outage probability and symbol error rate. Simulations are given to verify the correctness of the theoretical derivations. Results show that the proposed LFBF scheme can achieve considerable tradeoff between performance and complexity.

Joint Relay-and-Antenna Selection for Two-Way Decode-and-Forward MIMO Relay Networks

In this paper, two novel joint relay-and-antenna strategies are proposed and analyzed for multi- relay two-way multiple-input multiple-output (MIMO) decode-forward (DF) networks, namely, joint OR-TAS(Opportunistic Relaying -Transmit Antenna Selection) and joint SC-TAS (Selection Cooperation-Transmit Antenna Selection). For each joint selection scheme, the best transmit antenna at the two sources, a best relay, and a single best antenna at the selected relay are jointly determined in an optimum sense. The performance of these strategies is quantified by deriving the overall outage probability. For OR- TAS, we derive its outage probability directly, while for SC-TAS, we obtain its outage probability by proving that it is identical to that of OR-TAS. Also, the diversity orders is derived by presenting the upper bound and the lower bound of the overall outage probability, and the results show that the proposed selection strategies achieve the full diversity order. Finally, simulations are given to verify the correctness of the theoretical analysis.

Feedback Load Reduction Scheme for Opportunistic Multicast Scheduling in OFDM-Based Systems

This letter addresses the problem of feedback load reduction for opportunistic multicast scheduling (OMS) in OFDM-based systems. We investigate two scenarios, multicast service with large group size and multicast service with small group size, and derive two practical schemes respectively. The superiorities of the proposed schemes are: 1) no precise knowledge of the wireless fading channel is required, and 2) feedback load can be significantly reduced while the throughput performance remains comparable with the case of full feedback.