Radio channel characterisation and system-level modelling for ultra wideband body-centric wireless communications

PhDThe next generation of wireless communication is evolving towards user-centric networks, where constant and reliable connectivity and services are essential. Bodycentric wireless network (BCWN) is the most exciting and emerging 4G technology for short (1-5 m) and very short (below 1 m) range communication systems. It has got numerous applications including healthcare, entertainment, surveillance, emergency, sports and military. The major difference between the BCWN and conventional wireless systems is the radio channel over which the communication takes place. The human body is a hostile medium from the radio propagation perspective and it is therefore important to understand and characterise the effect of the human body on the antenna elements, the radio propagation channel parameters and hence the system performance. In addition, fading is another concern that affects the reliability and quality of the wireless link, which needs to be taken into account for a low cost and reliable wireless communication system for body-centric networks. The complex nature of the BCWN requires operating wireless devices to provide low power requirements, less complexity, low cost and compactness in size. Apart from these characteristics, scalable data rates and robust performance in most fading conditions and jamming environment, even at low signal to noise ratio (SNR) is needed. Ultra-wideband (UWB) technology is one of the most promising candidate for BCWN as it tends to fulfill most of these requirements. The thesis focuses on the characterisation of ultra wideband body-centric radio propagation channel using single and multiple antenna techniques. Apart from channel characterisation, system level modelling of potential UWB radio transceivers for body-centric wireless network is also proposed. Channel models with respect to large scale and delay analysis are derived from measured parameters. Results and analyses highlight the consequences of static and dynamic environments in addition to the antenna positions on the performance of body-centric wireless communication channels. Extensive measurement i campaigns are performed to analyse the significance of antenna diversity to combat the channel fading in body-centric wireless networks. Various diversity combining techniques are considered in this process. Measurement data are also used to predict the performance of potential UWB systems in the body-centric wireless networks. The study supports the significance of single and multiple antenna channel characterisation and modelling in producing suitable wireless systems for ultra low power body-centric wireless networks.University of Engineering and Technology Lahore Pakista

Modelling, performance analysis and design of WPAN systems

This paper covers the main issues that must be solved in order to design and analyse the performance of Wireless Personal Area Networks (WPANs) with the aid of simulation tools. We review state-of-the-art channel models to account for small- and large-scale propagation conditions in waveform- and system-level simulations. When dealing with waveform simulations, we also look at Montecarlo and importance sampling techniques that allow efficient estimation of error probabilities. Additionally, discrete channel models are introduced to efficiently link both waveform- and system-level approaches and we point out some methods to obtain the model parameters that are suitable for the wireless environment. The discussion of these techniques is complemented with two application examples that show the use of the different simulation levels for system design and performance study. With the paradigm of Bluetooth piconets we illustrate the usefulness of discrete channel models and we consider the design of an OFDM-based WPAN system to exemplify simulation from a waveform-level point of view.This work has been partially funded by European Commission (IST-2001–34157), Spanish Government (TIC2002–03498) and Madrid Community (UC3M-TEC-05–027).Publicad

Bit error rate estimation in WiMAX communications at vehicular speeds using Nakagami-m fading model

The wireless communication industry has experienced a rapid technological evolution from its basic first generation (1G) wireless systems to the latest fourth generation (4G) wireless broadband systems. Wireless broadband systems are becoming increasingly popular with consumers and the technological strength of 4G has played a major role behind the success of wireless broadband systems. The IEEE 802.16m standard of the Worldwide Interoperability for Microwave Access (WiMAX) has been accepted as a 4G standard by the Institute of Electrical and Electronics Engineers in 2011. The IEEE 802.16m is fully optimised for wireless communications in fixed environments and can deliver very high throughput and excellent quality of service. In mobile communication environments however, WiMAX consumers experience a graceful degradation of service as a direct function of vehicular speeds. At high vehicular speeds, the throughput drops in WiMAX systems and unless proactive measures such as forward error control and packet size optimisation are adopted and properly adjusted, many applications cannot be facilitated at high vehicular speeds in WiMAX communications. For any proactive measure, bit error rate estimation as a function of vehicular speed, serves as a useful tool. In this thesis, we present an analytical model for bit error rate estimation in WiMAX communications using the Nakagami-m fading model. We also show, through an analysis of the data collected from a practical WiMAX system, that the Nakagami-m model can be made adaptive as a function of speed, to represent fading in fixed environments as well as mobile environments

Logistic regression for BLER prediction in 5G

In this work, a block error rate (BLER) predictor for 5G based on logistic regression is presented. The regression is fed with transmission parameters and channel statistics. With these features, the predictor can model the behaviour of the transmission chain, including the low parity channel code (LDPC). In particular, for each modulation and coding scheme (MCS), the regression model uses as features the mean of the SINR over the allocated resources and the squared distance to the mean. Moreover, a single model able to cope with a set of modulation and coding schemes (MCSs) at the expense of certain accuracy loss is also proposed, and its performance evaluated. Possible applications for the regression models such as end-to-end modelling or as part of the adaptive modulation and coding (AMC) function are explored. Results show that the model has excellent accuracy in a wide set of scenarios