Efficient Placement of an Aerial Relay Drone for Throughput Maximization

Unmanned aerial vehicle (UAV) communication can be used in overcrowded areas and either during or postdisaster situations as an evolving technology to provide ubiquitous connections for wireless devices due to its flexibility, mobility, and good condition of the line of sight channels. In this paper, a single UAV is used as an aerial relay node to provide connectivity to wireless devices because of the considerable distance between wireless devices and the ground base station. Specifically, two path loss models have been utilized; a cellular-to-UAV path loss for a backhaul connection and an air-to-ground path loss model for a downlink connection scenario. Then, the tradeoff introduced by these models is discussed. The problem of efficient placement of an aerial relay node is formulated as an optimization problem, where the objective is to maximize the total throughput of wireless devices. To find an appropriate location for a relay aerial node that maximizes the overall throughput, we first use the particle swarm optimization algorithm to find the drone location; then, we use three different approaches, namely, (1) the equal power allocation approach, (2) water filling approach, and (3) modified water filling approach to maximize the total users’ throughput. The results show that the modified water filling outperforms the other two approaches in terms of the average sum rate of all users and the total number of served users. More specifically, in the best-case scenario, it was observed that the average sum rate of the modified water filling is better than the equal power allocation and ensuring 100% coverage. In contrast, the water filling provides a very close average sum rate to the modified water filling, but it only provides a 28% user coverage.

Transceiver Design for MIMO Systems with Individual Transmit Power Constraints

This paper investigate the transceiver design for single-user multiple-input multipleoutput system (SU-MIMO). Joint transceiver design with an improper modulation is developed based on the minimum total mean-squared error (TMSE) criterion under two different cases. One is equal power allocation (EPA) and other is the power constraint that jointly meets both EPA and total transmit power constraint (TTPC) (i.e ITPC). Transceiver is designed based on the assumption that both the perfect and imperfect channel state information (CSI) is available at both the transmitter and receiver. The simulation results show the performance improvement of the proposed work over conventional work in terms of bit error rate (BER).

Optimized Power Allocation and Relay Location Selection in Cooperative Relay Networks

An incremental selection hybrid decode-amplify forward (ISHDAF) scheme for the two-hop single relay systems and a relay selection strategy based on the hybrid decode-amplify-and-forward (HDAF) scheme for the multirelay systems are proposed along with an optimized power allocation for the Internet of Thing (IoT). Given total power as the constraint and outage probability as an objective function, the proposed scheme possesses good power efficiency better than the equal power allocation. By the ISHDAF scheme and HDAF relay selection strategy, an optimized power allocation for both the source and relay nodes is obtained, as well as an effective reduction of outage probability. In addition, the optimal relay location for maximizing the gain of the proposed algorithm is also investigated and designed. Simulation results show that, in both single relay and multirelay selection systems, some outage probability gains by the proposed scheme can be obtained. In the comparison of the optimized power allocation scheme with the equal power allocation one, nearly 0.1695 gains are obtained in the ISHDAF single relay network at a total power of 2 dB, and about 0.083 gains are obtained in the HDAF relay selection system with 2 relays at a total power of 2 dB.

Repetition Coding and Equal Power Allocation Scheme for JPEG Image Transmission over MIMO Systems

Multiple transmit and receive antenna systems have improved the reliability as well as data rate in a wireless communication system. Such advanced wireless architectures have empowered smart devices to fulfill the demand of multimedia content. Image is a major user generated content in wide range of applications, hence reliable transmission of image is an important research problem. New transmission and coding schemes that explore advantages of multiple antenna systems matched with source statistics have been developed. Based on a similar idea, an equal power allocation scheme for transmission of compressed images over multiple-input multiple-output (MIMO) systems employing partial repetition coding is proposed. The JPEG compression algorithm divides image into different quality layers. The proposed system repeats transmission of high quality data from more than one antenna as compared to the lower quality data which is transmitted using one antenna at most, in a particular time slot. A heuristic spatial multiplexing scheme is also proposed to optimally divide the bit stream chunks for transmission. Extensive simulations have shown that equal power allocation and repetition coding scheme is better as compared to reference schemes.

Study on the Resource Scheduling Algorithm for LTE-Advanced Downlink Systems

In the paper, the resource scheduling algorithm in the downlink of LTE-Advanced (LTE-A) assuming equal power allocation among subcarriers which adopted the technology of carrier aggregation (CA) is investigated. When the independent scheduling (INS) scheme is applied, the LTE users will acquire few resources because they cannot support CA technology. And the fairness of the system is disappointing. Focusing on the problem, a novel proportional fair (PF) scheduling algorithm based on INS is proposed. In the proposed method, the system fairness is well improved without bringing high complexity to the system. And also, we design a weigh factor which is related to the number of the carriers and the percentage of LTE users in the method. The simulation results show that the proposed algorithm can effectively increase the throughput of LTE users and improve the system fairness.

Energy-Efficient Dual-Iteration Power Allocation for Two-Phase Relay System with Massive Antennas

This paper considers the scenario where multiple source nodes communicate with multiple destination nodes simultaneously with the aid of an amplify-and-forward relay equipped with massive antennas. In order to achieve optimal energy efficiency (EE) of the entire relay system, this paper investigates the power allocation problem for the multiple pairs of nodes at both the source nodes and the relay node, where the relay employs the backward and forward zero-forcing filters. Since the EE optimization problem cannot be solved analytically, we propose a two-phase power allocation method. Given power allocation of one phase, the optimal power allocation is derived for the other phase. Furthermore, two dual-iteration power allocation (DIPA) algorithms with performance approaching that of optimal EE are developed based on the instantaneous and statistic channel state information, respectively. Numerical results show that the proposed DIPA algorithms can greatly improve EE while guaranteeing spectrum efficiency (SE) when compared with the equal power allocation algorithm. Moreover, both algorithms suggest that deploying a rational number of antennas at the relay node and multiplexing a reasonable number of node pairs can improve on the EE and SE.