Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions

This survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature

Initial Synchronisation in the Multiple-Input Multiple-Output Aided Single- and Multi-Carrier DS-CDMA as well as DS-UWB Downlink

In this thesis, we propose and investigate code acquisition schemes employing both colocated and cooperative Multiple Input/Multiple Output (MIMO) aided Single-Carrier (SC) and Multi-Carrier (MC) Code Division Multiple Access (CDMA) DownLink (DL) schemes. We study their characteristics and performance in terms of both Non-Coherent (NC) and Differentially Coherent (DC) MIMO scenarios. Furthermore, we also propose iterative code acquisition schemes for the Direct Sequence-Ultra WideBand (DS-UWB) DL. There is a paucity of code acquisition techniques designed for transmit diversity aided systems. Moreover, there are no in-depth studies representing the fundamental characteristics of code acquisition schemes employing both co-located and cooperative MIMOs. Hence we investigate both NC and DC code acquisition schemes in the co-located and cooperative MIMO aided SC and MC DS-CDMA DL, when communicating over spatially uncorrelated Rayleigh channels. The issues of NC initial and post-initial acquisition schemes as well as DC schemes are studied as a function of the number of co-located antennas by quantifying the attainable correct detection probability and mean acquisition time performances. The research of DS-UWB systems has recently attracted a significant interest in both the academic and industrial community. In the DS-UWB DL, initial acquisition is required for both coarse timing as well as code phase alignment. Both of these constitute a challenging problem owing to the extremely short chip-duration of UWB systems. This leads to a huge acquisition search space size, which is represented as the product of the number of legitimate code phases in the uncertainty region of the PN code and the number of legitimate signalling pulse positions. Therefore the benefits of the iterative code acquisition schemes are analysed in terms of the achievable correct detection probability and mean acquisition time performances. Hence we significantly reduce the search space size with the aid of a Tanner graph based Message Passing (MP) technique, which is combined with the employment of beneficially selected generator polynomials, multiple receive antennas and appropriately designed multiple-component decoders. Finally, we characterise a range of two-stage iterative acquisition schemes employing iterative MP designed for a multiple receive antenna assisted DS-UWB DL scenario

Proceedings of the Fall 1995 Advanced Digital Communication Systems

Coordinated Science Laboratory was formerly known as Control Systems Laborator

Initial synchronisation in the multiple-input multiple-output aided single- and multi-carrier DS-CDMA as well as DS-UWB downlink

In this thesis, we propose and investigate code acquisition schemes employing both colocated and cooperative Multiple Input/Multiple Output (MIMO) aided Single-Carrier (SC) and Multi-Carrier (MC) Code Division Multiple Access (CDMA) DownLink (DL) schemes. We study their characteristics and performance in terms of both Non-Coherent (NC) and Differentially Coherent (DC) MIMO scenarios. Furthermore, we also propose iterative code acquisition schemes for the Direct Sequence-Ultra WideBand (DS-UWB) DL. There is a paucity of code acquisition techniques designed for transmit diversity aided systems. Moreover, there are no in-depth studies representing the fundamental characteristics of code acquisition schemes employing both co-located and cooperative MIMOs. Hence we investigate both NC and DC code acquisition schemes in the co-located and cooperative MIMO aided SC and MC DS-CDMA DL, when communicating over spatially uncorrelated Rayleigh channels. The issues of NC initial and post-initial acquisition schemes as well as DC schemes are studied as a function of the number of co-located antennas by quantifying the attainable correct detection probability and mean acquisition time performances. The research of DS-UWB systems has recently attracted a significant interest in both the academic and industrial community. In the DS-UWB DL, initial acquisition is required for both coarse timing as well as code phase alignment. Both of these constitute a challenging problem owing to the extremely short chip-duration of UWB systems. This leads to a huge acquisition search space size, which is represented as the product of the number of legitimate code phases in the uncertainty region of the PN code and the number of legitimate signalling pulse positions. Therefore the benefits of the iterative code acquisition schemes are analysed in terms of the achievable correct detection probability and mean acquisition time performances. Hence we significantly reduce the search space size with the aid of a Tanner graph based Message Passing (MP) technique, which is combined with the employment of beneficially selected generator polynomials, multiple receive antennas and appropriately designed multiple-component decoders. Finally, we characterise a range of two-stage iterative acquisition schemes employing iterative MP designed for a multiple receive antenna assisted DS-UWB DL scenario.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Adaptive PN code synchronisation in DS-CDMA systems

Spread Spectrum (SS) communication, initially designed for military applications, is now the basis for many of today's advanced communications systems such as Code Division Multiple Access (CDMA), Global Positioning System (GPS), Wireless Local Loop (WLL) , etc. For effective communication to take place in systems using SS modulation, the Pseudo-random Noise (PN) code used at the receiver to despread the received signal must be identical and be synchronised with the PN code that was used to spread the signal at the transmitter. Synchronisation is done in two steps: coarse synchronisation or acquisition, and fine synchronisation or tracking. Acquisition involves obtaining a coarse estimate of the phase shift between the transmitted PN code and that at the receiver so that the received PN code will be aligned or synchronised with the locally generated PN code. After acquisition, tracldng is now done which involves maintaining the alignment of the two PN codes. This thesis presents results of the research calTied out on a proposed adaptive PN code acquisition circuit designed to improve the synchronisation process in Direct Sequence CDMA (DS-CDMA) systems. The acquisition circuit is implemented using a Matched Filter (MF) for the correlation operation and the threshold setting device is an adaptive processor known as the Cell Averaging Constant False Alarm Rate (CA-CFAR) processor. It is a double dwell acquisition circuit where the second dwell is implemented by Post Detection Integration (PDI). Depending on the application, PDI can be used to mitigate the effect of frequency offset in non-coherent detectors and/or in the implementation of multiple dwell acquisition systems. Equations relating the performance measures - the probability of false alarm (Pra ), the probability of detection (P d) and the mean acquisition time (E {Tacq}) - of the circuit are deri ved. Monte Carlo simulation was used for the independent validation of the theoretical results obtained, and the strong agreement between these results shows the accuracy of the derived equations for the proposed circuit. Due to the combination of PDI and CA-CFAR processor in the implementation of the circuit, results obtained show that it can provide a good measure of robustness to frequency offset and noise power variations in mobile environment, consequently leading to improved acquisition time performance. The complete synchronisation circuit is realised by using this circuit in conjunction with a conventional code tracking circuit. Therefore, a study of a Non-coherent Delay-Locked Loop (NDLL) code tracking circuit is also calTied out.EThOS - Electronic Theses Online ServiceGBUnited Kingdo