Location based services are the hottest applications on mobile devices nowadays and the growth is continuing. Indoor wireless positioning is the key technology to enable location based services to work well indoors, where GPS normally could not work. Bluetooth has been widely used in mobile devices like phone, PAD etc. therefore Bluetooth based indoor positioning has great market potential. Radio Signal Strength (RSS) is a key parameter for wireless positioning. New Bluetooth standard (since version 2.1) enables RSS to be discovered without time consuming pre-connection. In this research, general wireless positioning technologies are firstly analysed. Then RSS based Bluetooth positioning using the new feature is studied. The mathematical model is established to analyse the relation between RSS and the distance between two Bluetooth devices. Three distance-based algorithms are used for Bluetooth positioning: Least Square Estimation, Three-border and Centroid Method. Comparison results are analysed and the ways to improve the positioning accuracy are discussed.

This paper investigates an unmanned aerial vehicle (UAV)-enabled wireless communication network with multiple pairs of source-destination ground users (GUs), where the rotary-wing UAV acts as an aerial mobile relay to transfer information from the source GUs to corresponding destination GUs when the direct terrestrial communication is blocked. On the premise of satisfying the communication requirements of all GUs, we intend to minimize the total energy consumption of supporting the propulsion and communication by jointly optimizing communication time, UAV transmit power allocation and UAV trajectory. To tackle the formulated non-convex problem, we first transform the original problem into a more tractable form with a finite number of optimization variables using the path discretization approach. Then, we decompose the joint optimization problem into three subproblems to find a near optimal solution. Finally, these subproblems can be efficiently solved via the proposed iterative algorithm based on block coordinate descent and successive convex approximation (SCA) techniques. As the initial UAV trajectory has significant influence on the final results, we put forward a novel trajectory initialization scheme by combining the classic Pickup-and-Delivery Problem with fly-hover-communication protocol. Numerical results demonstrate that our proposed design contributes to significant performance enhancement compared with other two benchmarks.

Wireless multimedia traffic has increased considerably in recent years, and it has become urgent to propose new approaches to deliver multimedia application in an energy-efficient manner. In wireless networks, observations show that some multimedia streams requested by users in a certain geographical area for a certain period exhibit very similar behavior. By exploiting the similarity, we can significantly reduce power consumption in wireless cellular networks. In this article, we present the description of user behavior in HCN and then propose an architecture for multimedia transmission over HCN. Based on this architecture, an energy-efficient multimedia transmission scheme is proposed to optimize energy efficiency by exploiting user behavior. In this scheme macrocells and small cells cooperatively multicast/unicast multimedia steams without QoS degradation. Illustrative results indicate that the exploitation of user behavior and base station cooperation is able to bring green multimedia transmission for HCN.

This paper investigates a UAV-enabled wireless communication system with multiple UAVs (multi-UAVs), where the UAVs are dispatched to collect information from a group of ground terminals (GTs) that are energy-constrained. In particular, we consider that UAVs may differ so that each UAV can be individually designed. Besides, for the sake of collision avoidance of these multi-UAVs, an effective security flight mechanism is designed. To achieve a fair performance between GTs, this paper aims to maximize the minimum GT throughput by jointly optimizing the communication scheduling, power allocation, and UAVs’ trajectories. However, the formulated problem is shown to be a mixed integer non-convex optimization problem that is hard to solve. To tackle this problem, we first decompose it into two subproblems, and then, an efficient iterative algorithm is proposed by applying the block coordinate descent, relaxation, as well as successive convex optimization techniques. The proposed algorithm can be effectively utilized in wireless communication and networks. Moreover, a benchmark is set for the purpose of illustrating the superiority of the proposed design. Finally, numerical results show that the proposed design achieves a significant performance gain as compared with the benchmark.

Wireless communications with unmanned aerial vehicles (UAVs) is a promising technology offering potential high mobility and low cost. This paper studies a UAV-enabled communication system, in which a fixed-wing UAV is deployed to collect information from a group of distributed ground terminals (GTs). Considering the requirements for quality of service (QoS) (i.e., the throughput of each GT is above a given threshold) and GT scheduling, we maximize the energy efficiency (EE) of the UAV in bits/Joule by optimizing the UAV’s flight trajectory. In this paper, a mixed integer nonconvex optimization problem is formulated. As that is difficult to solve, we divide the formulated problem into two subproblems and apply standard linear programming (LP) and successive convex optimization techniques. We further propose an efficient iterative algorithm that jointly optimizes GT scheduling and the UAV’s trajectory. Moreover, we set two special cases as benchmarks to measure the performance of the proposed design. The numerical results show that our proposed design achieves much better performance than the other two benchmark designs.