Wireless transmission protocols using relays for broadcast and information exchange channels

Relays have been used to overcome existing network performance bottlenecks in meeting the growing demand for large bandwidth and high quality of service (QoS) in wireless networks. This thesis proposes several wireless transmission protocols using relays in practical multi-user broadcast and information exchange channels. The main theme is to demonstrate that efficient use of relays provides an additional dimension to improve reliability, throughput, power efficiency and secrecy. First, a spectrally efficient cooperative transmission protocol is proposed for the multiple-input and singleoutput (MISO) broadcast channel to improve the reliability of wireless transmission. The proposed protocol mitigates co-channel interference and provides another dimension to improve the diversity gain. Analytical and simulation results show that outage probability and the diversity and multiplexing tradeoff of the proposed cooperative protocol outperforms the non-cooperative scheme. Second, a two-way relaying protocol is proposed for the multi-pair, two-way relaying channel to improve the throughput and reliability. The proposed protocol enables both the users and the relay to participate in interference cancellation. Several beamforming schemes are proposed for the multi-antenna relay. Analytical and simulation results reveal that the proposed protocol delivers significant improvements in ergodic capacity, outage probability and the diversity and multiplexing tradeoff if compared to existing schemes. Third, a joint beamforming and power management scheme is proposed for multiple-input and multiple-output (MIMO) two-way relaying channel to improve the sum-rate. Network power allocation and power control optimisation problems are formulated and solved using convex optimisation techniques. Simulation results verify that the proposed scheme delivers better sum-rate or consumes lower power when compared to existing schemes. Fourth, two-way secrecy schemes which combine one-time pad and wiretap coding are proposed for the scalar broadcast channel to improve secrecy rate. The proposed schemes utilise the channel reciprocity and employ relays to forward secret messages. Analytical and simulation results reveal that the proposed schemes are able to achieve positive secrecy rates even when the number of users is large. All of these new wireless transmission protocols help to realise better throughput, reliability, power efficiency and secrecy for wireless broadcast and information exchange channels through the efficient use of relays

Joint power allocation for DF concatenated MIMO successive relaying scheme under network power constraints

Power efficiency is a vital consideration in wireless system. In this paper, we propose a framework for efficient power allocation in decode and forward multiple input multiple output successive relaying systems under network power constraints. Our aim is to maximize the information rate at each link by an optimal power allocation scheme via the primal dual algorithm. Then, we jointly allocate power to the source and transmitting relay under network power constraints. The simulated results show that the proposed joint power allocation scheme under network power constraint can outperform the uniform power allocation under an aggregate power constraints

Choice criteria for private tertiary programs at a private higher education institution / Nurlida Ismail...[et al.]

The objective of this study is to examine key determinants that influence students’ choice in selecting a program. The theoretical framework was adapted from Chapman’s (1981) and Cubillo, Sanchez and Cervino’s (2006) models. Our study of students’ choice criteria was conducted using the survey questionnaire method and a five-point Likert scale was employed. The sample for the testing and refinement process consisted of 299 first year tertiary students from across all three programs in a private higher education institution. All our hypotheses are supported by Multiple Linear Regression analysis. The results indicated that program evaluation is the most significant factor that influences students’ program choice. This is followed by the college is effort to communicate with students and level of educational aspiration. However, it was found that significant persons have the least influence on students’ program choice

Relay node positioning for inter-band carrier aggregation with asymmetrical coverage

Relaying and carrier aggregation are two main features for Long Term Evolution Advanced (LTE-A) that improve the signal and increase the data rate. In an inter-band carrier aggregation scenario, the use of component carriers with large frequency gaps results in asymmetrical coverage. The asymmetrical coverage leads to the capacity fairness issue, where users at the cell edge always suffer from low capacity. This paper studies the use of relay node to solve the capacity fairness issue due to asymmetrical coverage in inter-band carrier aggregation scenario with two component carrier. The effects of relay position to the capacity of cell edge user is investigated by considering various combinations of the component carrier, heights and transmit power of base station and the relay node. The simulation reveals that the relay node can be placed inside the overlapped coverage region of asymmetrical coverage in order to improve the capacity and show that for average cases the relay node should be placed close to the cell edge user

A zero-sum game approach for non-orthogonal multiple access systems: legitimate eavesdropper case

In this paper, secure communication in non-orthogonal multiple access (NOMA) downlink system is considered wherein two NOMA users with channel gain difference are paired in each transmission slot. The user with poor channel condition (weak user) is entrusted, while the user with good channel condition (strong user) is a potential eavesdropper. The weak user data can be intercepted by the strong user since the strong user needs to decode the weak user's message for successive interference cancellation operation in NOMA. To impair strong user's eavesdropping capability, weak user's information-bearing signal is merged with an artificial signal (AS). Thus, the eavesdropping process requires extra decoding step at higher power level. The secrecy outage probability of the weak user is derived and provided in closed-form expression. The weak user faces a choice between transmitting the information-bearing signal with the total power and the deploying the AS technique, whereas the strong user can choose whether to eavesdrop the weak user's message or not. To investigate users' power-secrecy tradeoffs, their interactions are modeled as a non-cooperative zero-sum game. The existence of Nash equilibria (NEs) of the proposed game is first analyzed, and pure and mixed-strategy NE profiles are provided. In addition, numerical simulations are conducted to validate the analytical results and to prove that AS-Aided proposed scheme enhances the secrecy performance of NOMA systems while maintaining the NOMA superiority over OMA systems

Cooperative non-orthogonal multiple access with physical layer network coding

Physical layer network coding (PNC) has been proposed for information exchange between a pair of users assisted by a relay. However, the spectral efficiency of PNC reduces when the number of user pairs increases due to the requirement of orthogonal channels for multi-pair operation. This paper proposes the use of cooperative non-orthogonal multiple access (NOMA) and PNC to improve the spectral efficiency and outage performance of multi-pair information exchange. Specifically, a cognitive radio inspired NOMA is considered. The quality of service of the primary user pair is guaranteed through dynamic power allocation policy, while the secondary user pair is served on best effort basis. The simulation result shows that the proposed cognitive radio inspired NOMA scheme with PNC achieves higher spectral efficiency and better outage performance if compared with the existing orthogonal multiple access schemes with PNC

Dual-Band Resonator Designs for Near-Field Wireless Energy Transfer Applications

Dual-band near-field wireless energy transfer (WET) designs outweigh single-band system with regard to either concurrent energy and data transfer or multiple wireless charging standard functionalities. There are two major approaches in resonator designs, namely, multi-coil and single-coil. This chapter presents a review on design constraints for each design approach and rectification techniques available in counteracting impediments of dual-band near-field WET systems. Challenges pertinent to link design are discussed primarily followed by methods implemented to mitigate detrimental impact on performance metrics. Front-end dual-band resonator design methods are accentuated in this chapter in lieu of end-to-end WET system. This is envisioned to offer insights for designers contemplating on design modes or developing ways to facilitate a boost in rectification options currently available

Wireless nonradiative energy transfer: antenna performance enhancement techniques.

In recent times, wireless nonradiative energy transfer has elicited considerable research interest. Its varied applications range from contactless battery charging and power delivery to sensors, near-field communications, and radio-frequency identification (RFID). Antenna performance plays a key role in the successful deployment of a wireless energy transfer strategy. This article presents an integrated survey of metrics and methods that have been employed to evaluate and improve antenna performance in nonradiative energy transfer schemes

Network NOMA for Co-existence of Aerial and Terrestrial Users

Scarcity of the radio spectrum and high inter-cell interference (ICI) are major impediments to efficient connectivity in cellular-connected unmanned aerial vehicles (UAV)s. To address these issues, we propose aerial-terrestrial network non-orthogonal multiple access (ATN-NOMA). In the proposed scheme, we pair the aerial user (AU) and terrestrial user (TU) in a NOMA setting to leverage their asymmetric channel gains and rate demands in downlink communication. The high ICI issue at the AU receiver is further managed by equipping the AU with an adjustable beamwidth directional antenna and forming a distributed beamforming among the coordinated terrestrial base stations (BSs). The proposed ATN-NOMA scheme obtains the optimal beamwidth and power allocation to maximize the TUs' sum-rate subject to the AU's Quality-of-Service (QoS) requirement. The corresponding optimization is a non-convex optimization problem for which we exploit the structure of the problem to obtain a local optimal solution. We further compare TUs' sum-rate and AU's outage probability of the proposed scheme with multiple schemes. Simulation results show that our proposed scheme significantly outperforms the existing schemes and further demonstrate a robust performance against UAV altitude variations