UWB communication systems acquisition at symbol rate sampling for IEEE standard channel models

For ultra-wideband (UWB) communications, acquisition is challenging. The reason is from the ultra short pulse shape and ultra dense multipath interference. Ultra short pulse indicates the acquisition region is very narrow. Sampling is another challenge for UWB design due to the need for ultra high speed analog-to digital converter.A sub-optimum and under-sampling scheme using pilot codes as transmitted reference is proposed here for acquisition. The sampling rate for the receiver is at the symbol rate. A new architecture, the reference aided matched filter is studied in this project. The reference aided matched filter method avoids using complex rake receiver to estimate channel parameters and high sampling rate for interpolation. A limited number of matched filters are used as a filter bank to search for the strongest path. Timing offset for acquisition is then estimated and passed to an advanced verification algorithm. For optimum performance of acquisition, the adaptive post detection integration is proposed to solve the problem from dense inter-symbol interference during the acquisition. A low-complex early-late gate tracking loop is one element of the adaptive post detection integration. This tracking scheme assists in improving acquisition accuracy. The proposed scheme is evaluated using Matlab Simulink simulations in term of mean acquisition time, system performance and false alarm. Simulation results show proposed algorithm is very effective in ultra dense multipath channels. This research proves reference aided acquisition with tracking loop is promising in UWB application

Compressive Sampling based Multiple Symbol Differential Detection for UWB Communications

Compressive sampling (CS) based multiple sym- bol differential detectors are proposed for impulse-radio ultra- wideband signaling, using the principles of generalized likelihood ratio tests. The CS based detectors correspond to two communica- tion scenarios. One, where the signaling is fully synchronized at the receiver and the other, where there exists a symbol level synchro- nization only. With the help of CS, the sampling rates are reduced much below the Nyquist rate to save on the high power consumed by the analog-to-digital converters. In stark contrast to the usual compressive sampling practices, the proposed detectors work on the compressed samples directly, thereby avoiding a complicated reconstruction step and resulting in a reduction of the implemen- tation complexity. To resolve the detection of multiple symbols, compressed sphere decoders are proposed as well, for both com- munication scenarios, which can further help to reduce the sys- tem complexity. Differential detection directly on the compressed symbols is generally marred by the requirement of an identical measurement process for every received symbol. Our proposed detectors are valid for scenarios where the measurement process is the same as well as where it is different for each received symbol

Realization Limits of Impulse-Radio UWB Indoor Localization Systems

In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them

Antenna and radio channel characterisation for low‐power personal and body area networks

PhDThe continuous miniaturisation of sensors, as well as the progression in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to new usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body. Body-centric wireless communications (BCWCs) is a central point in the development of fourth generation mobile communications. Body-centric wireless networks take their place within the personal area networks, body area networks and sensor networks which are all emerging technologies that have a wide range of applications (such as, healthcare, entertainment, surveillance, emergency, sports and military). The major difference between BCWC and conventional wireless systems is the radio channels over which the communication takes place. The human body is a hostile environment from a radio propagation perspective and it is therefore important to understand and characterise the effects of the human body on the antenna elements, the radio channel parameters and, hence, system performance. This thesis focuses on the study of body-worn antennas and on-body radio propagation channels. The performance parameters of five different narrowband (2.45 GHz) and four UWB (3.1- 10.6 GHz) body-worn antennas in the presence of human body are investigated and compared. This was performed through a combination of numerical simulations and measurement campaigns. Parametric studies and statistical analysis, addressing the human body effects on the performance parameters of different types of narrowband and UWB antennas have been presented. The aim of this study is to understand the human body effects on the antenna parameters and specify the suitable antenna in BCWCs at both 2.45 GHz and UWB frequencies. Extensive experimental investigations are carried out to study the effects of various antenna types on the on-body radio propagation channels as well. Results and analysis emphasize the best body-worn antenna for reliable and power-efficient on-body communications. Based on the results and analysis, a novel dual-band and dual-mode antenna is proposed for power-efficient and reliable on-body and off-body communications. The on-body performance of the DBDM antenna at 2.45 GHz is compared with other five narrowband antennas. Based on the results and analysis of six narrowband and four UWB antennas, antenna specifications and design guidelines are provided that will help in selecting the best body-worn antenna for both narrowband and UWB systems to be applied in body-centric wireless networks (BCWNs). A comparison between IV the narrowband and UWB antenna parameters are also provided. At the end of the thesis, the subject-specificity of the on-body radio propagation channel at 2.45 GHz and 3-10 GHz was experimentally investigated by considering eight real human test subjects of different shapes, heights and sizes. The subject-specificity of the on-body radio propagation channels was compared between the narrowband and UWB systems as well