Igbafe Orikumhi

Implementation of Relay-Based Emergency Communication System on Software Defined Radio

The loss of communication system during natural disaster is known to hamper the efficiency of disaster response. In most cases, the paralyzed communication system often appears as one of the factors which delays the disaster response and complicates the rescue operation. However, if the communication systems including the mobile network are in working conditions, they are usually congested. Hence there is a need for an improved emergency communication system (ECS) to provide reliability and improve system performance during emergency. Furthermore, most of the works on ECS are based on theoretical simulations which can not capture the real world scenario. Taking into account the structure of the internet of things, which includes sensing, computing and communicating, this paper presents an ECS which consists of a wireless relay node, a disaster sensing and detection system. The relay node serves as a temporary communication station to help victims equipped with mobile phones to maintain a reliable communication link with the next available base station in the vicinity. Meanwhile, the sensors are used to detect abnormal changes in environmental parameters such as temperature and water level. The design is implemented on software defined radios. The simulated and measured results shows significant improvement in terms of data and bit error rate over the direct communication scheme.

Wireless Information and Power Transfer in MIMO Virtual Full-Duplex Relaying System

Interrelay interference (IRI) is known to degrade the performance of virtual full-duplex (FD) relaying schemes. Although interference avoidance and cancelation strategies have been proposed in the existing literature, most studies reflect the traditional information theoretical viewpoint of interference as a degrading factor on information decoding (ID). However, from energy harvesting (EH) perspective, the IRI could be beneficial. This motivates the study of simultaneous wireless information and power transfer in decode-and-forward multiple input multiple output virtual FD relaying system, where the IRI serves as an additional source of energy to the relay. To manage the degrading effect of the IRI on the ID receiver, transmit antenna selection is proposed at the relay. In addition, precoding matrices that optimize the ID and EH receivers are jointly designed. The simulated results show that although IRI could be a degrading factor from the information viewpoint, it can be properly managed and exploited for EH at the relay while maintaining the end-to-end data rate. In addition, the results show that the end-to-end information rate and harvested energy can be simultaneously achieved using the proposed precoders.

Reliable Virtual Full-Duplex Relaying in the Presence of Interrelay Interference

Interrelay interference (IRI) is known to limit the performance of virtual full-duplex (VFD) relaying schemes. Available interference cancelation schemes are unable to simultaneously improve the diversity and maintain the multiplexing gain of VFD relaying schemes in multiple antennas scenarios. In this paper, we propose a technique to improve the reliability of multiantenna VFD relaying scheme, while maintaining the multiplexing gain in the presence of IRI. In the proposed scheme, the source and interrelay channels are concatenated and their signals are jointly decoded at the relay. A superposition of the decoded messages is forwarded to the destination. To reduce the effect of IRI on the receiving relay, two suboptimal relay transmit antenna selection schemes, namely, random antenna selection and maximum capacity antenna selection, are investigated. The system capacity and outage probability bounds of the proposed scheme are derived in closed form. The diversity and multiplexing tradeoff is also characterized. The analytical and numerical results show that the proposed scheme can achieve full diversity and maintain the multiplexing gain of the full-duplex relaying scheme. Also, the proposed scheme can outperform conventional VFD relaying scheme in terms of reliability even in the presence of IRI.

Beamforming and antenna selection for successive relaying with inter-relay interference

The performance of multiple input multiple output (MIMO) successive relaying (SR) scheme, is degraded by inter-relay interference. When there is no direct link between the source and the destination, improving the performance requires exploring the full diversity provided by the participating relays. However, to achieve the full diversity, the multiplexing gain has to be traded off. In this paper, we propose a spectral efficient MIMO SR cooperative scheme, using concatenated channels and superposition coding at the relay. The proposed scheme can achieve higher capacity when compared to other conventional SR scheme while maintaining the same multiplexing gain. The diversity and multiplexing tradeoff of the proposed scheme can outperform the conventional SR scheme without interference.

On the sparsity-aware partial-update NLMS algorithms for UWB channel estimation

Partial updating of filter coefficients is an effective method for reducing computational load and power consumption in adaptive filter implementation. In this paper, we present a class of MMax partial update NLMS algorithms suitable for estimating UWB channels, whose characteristics have shown to vary between highly sparse and dense depending on the channel environment under consideration and the measured bandwidth. Simulation results show improved performance of the proposed algorithms in terms of convergence speed, and computational complexity.