Enhancing the bit error rate performance of ultra wideband systems using time-hopping pulse position modulation in multiple access environments

Ultra-Wide Band (UWB) technology is one of the possible solutions for future short-range indoor data communication with uniquely attractive features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. A major challenge when designing UWB systems is choosing a suitable modulation technique. Data rate, transceiver complexity, and BER performance of the transmitted signal are all related to the employed modulation scheme. Several classical modulation schemes can be used to create UWB signals, some are more efficient than others. These schemes are namely, Pulse Position Modulation (PPM), Pulse Amplitude Modulation (PAM), Binary Phase Shift Keying (BPSK), and On-Off Keying (OOK) are reviewed. In the thesis, the performance of PPM system, combined with Time Hopping Spread Spectrum (THSS) multiple access technique is evaluated in an asynchronous multiple access free space environment. The multiple access interference is first assumed to be a zero mean Gaussian random process to simulate the scenario of a multi user environment. An exact BER calculation is then evaluated based on the characteristic function (CF) method, for Time Hopping-Pulse Position Modulation Ultra Wide Band (TH-PPM UWB) systems with multiple access interference (MAI) in AWGN environment. The resulting analytical expression is then used to assess the accuracy of the MAI Gaussian Approximation (GA) first assumed. The GA is shown to be inaccurate for predicting BERs for medium and large signal-to-noise ratio (SNR) values. Furthermore, the analysis of TH-PPM system is further extended to evaluate the influence of changing and optimising some of the system or signal parameters. It can be shown how the system is greatly sensitive to variations in some signal parameters, like the pulse shape, the time-shift parameter associated with PPM, and the pulse length. In addition, the system performance can be greatly improved by optimising other system parameters like the number of pulses per bit, Ns, and the number of time slots per frame, Nh. All these evaluation are addressed through numerical examples. Then, we can say that, by improving signal or system parameters, the BER performance of the system is greatly enhanced. This is achieved without imposing exact complexity to the transceiver and with moderate computational calculations

A low-cost time-hopping impulse radio system for high data rate transmission

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special Issue on UWB - State of the Art

Performance of Bit Error Rate and Power Spectral Density of Ultra Wideband with Time Hopping Sequences.

This thesis focuses on several modulation methods for an ultra wideband (UWB) signal. These methods are pulse position modulation (PPM), binary phase shift keying (BPSK), on/off key shifting (OOK), and pulse amplitude modulation (PAM). In addition, time hopping is considered for these modulation schemes, where the capacity per time frame of time hopping PPM is studied using different spreading ratios. This thesis proves that with the addition of time hopping to all types of modulated UWB signals, the performance of power spectral density improves in all aspects, despite the increase of data per time frame. Note that despite the increase of data per frame, the bit error rate remains the same as standard non-time hopping UWB modulated signals

Performanse višeimpulsno-pozicijske amplitudne modulacije za TH IR-UWB komunikacijske sustave

The multi pulse position amplitude modulation scheme for time-hopping multiple access impulse radio ultrawideband communication systems has been presented in this paper. Multi pulse position amplitude modulation is a hybrid modulation technique, which combines multi pulse position modulation and pulse amplitude modulation. It is shown that multi pulse position amplitude modulation significantly outperforms pulse position modulation with respect to bandwidth efficiency. The multi pulse position amplitude modulation error probability over IEEE 802.15.3a multipath fading channels in multiuser environment is derived. The system analysis shows that the proper selection of modulation parameters can improve the system performance at the cost of hardware complexity (and vice versa).U ovom je radu predstavljena višeimpulsno-pozicijska amplitudna modulacijska shema za impulsne ultraširokopojasne radiokomunikacijske sustave, zasnovana na višekorisničkom pristupu s vremenskim skakanjem. Višeimpulsno-pozicijska amplitudna modulacija je hibridni modulacijski postupak, koji je kombinacija višeimpulsno-pozicijske modulacije i impulsno-amplitudne modulacije. Pokazano je da višeimpulsno-pozicijska amplitudna modulacija značajno nadmašuje impulsno-pozicijsku modulaciju u pogledu pojasne učinkovitosti. Izvedena je vjerojatnost pogreške višeimpulsno-pozicijske amplitudne modulacije u kanalu IEEE 802.15.3a s višestaznim rasprostiranjem i iščezavanjem signala u višekorisničkom okruženju. Analiza sustava pokazuje da odgovaraju ći izbor parametara modulacije može poboljšati performanse sustava uz povećanje složenosti sklopovlja (i obrnuto)

Comparison of Bit Error Rate and Power Spectral Density on the Ultra Wideband Impulse Radio Systems

Ultra-Wideband (UWB) is defined as a wireless transmission scheme that occupies a bandwidth of more than 25% of its center frequency. UWB Impulse Radio (UWB-IR) is a popular implementation of the UWB technology. In UWB-IR, information is encoded in baseband without any carrier modulation. Pulse shaping and baseband modulation scheme are two of the determinants on the performance of the UWB-IR. In this thesis, both temporal and spectral characteristics of the UWB-IR are examined because all radio signals exist in both the time and frequency domains. Firstly, the bit error rate (BER) performance of the UWB-IR is investigated via simulation using three modulation schemes: Pulse position modulation (PPM), on-off shift keying (OOK), and binary phase shift keying (BPSK). The results are verified for three different pulse shaping named Gaussian first derivative, Gaussian second derivative, and return-to-zero (RZ) Manchester. Secondly, the effects of the UWB-IR parameters on the power spectral density (PSD) are investigated because PSD provides information on how the power is distributed over the radio frequency (RF) spectrum and determines the interference of UWB-IR and the existing systems to each other in the spectrum. The investigated UWB-IR parameters include pulse duration, pulse repetition rate, modulation scheme, and pseudorandom codes

Multi Detector Fusion of Dynamic TOA Estimation using Kalman Filter

In this paper, we propose fusion of dynamic TOA (time of arrival) from multiple non-coherent detectors like energy detectors operating at sub-Nyquist rate through Kalman filtering. We also show that by using multiple of these energy detectors, we can achieve the performance of a digital matched filter implementation in the AWGN (additive white Gaussian noise) setting. We derive analytical expression for number of energy detectors needed to achieve the matched filter performance. We demonstrate in simulation the validity of our analytical approach. Results indicate that number of energy detectors needed will be high at low SNRs and converge to a constant number as the SNR increases. We also study the performance of the strategy proposed using IEEE 802.15.4a CM1 channel model and show in simulation that two sub-Nyquist detectors are sufficient to match the performance of digital matched filter