Frequency and time hopping PPM UWB multiple access communication scheme

In this paper we propose frequency and time hopping pulse position modulation (FTH-PPM) ultra wideband (UWB) for multiple access communications.We have derived and investigated the bit error probability for the multi-user synchronous transmitter case in multipath channels with Additive White Gaussian Noise (AWGN). Simulation results show that bit error probability performance of FTH-PPM UWB out performs the time hopping pulse position modulated (TH-PPM) UWB system. It also show that multiuser capacity of FTH-PPM UWB system is much better than TH-PPM UWB system

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

Approximation of L\"owdin Orthogonalization to a Spectrally Efficient Orthogonal Overlapping PPM Design for UWB Impulse Radio

In this paper we consider the design of spectrally efficient time-limited pulses for ultrawideband (UWB) systems using an overlapping pulse position modulation scheme. For this we investigate an orthogonalization method, which was developed in 1950 by Per-Olov L\"owdin. Our objective is to obtain a set of N orthogonal (L\"owdin) pulses, which remain time-limited and spectrally efficient for UWB systems, from a set of N equidistant translates of a time-limited optimal spectral designed UWB pulse. We derive an approximate L\"owdin orthogonalization (ALO) by using circulant approximations for the Gram matrix to obtain a practical filter implementation. We show that the centered ALO and L\"owdin pulses converge pointwise to the same Nyquist pulse as N tends to infinity. The set of translates of the Nyquist pulse forms an orthonormal basis or the shift-invariant space generated by the initial spectral optimal pulse. The ALO transform provides a closed-form approximation of the L\"owdin transform, which can be implemented in an analog fashion without the need of analog to digital conversions. Furthermore, we investigate the interplay between the optimization and the orthogonalization procedure by using methods from the theory of shift-invariant spaces. Finally we develop a connection between our results and wavelet and frame theory.Comment: 33 pages, 11 figures. Accepted for publication 9 Sep 201

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

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

Characterization of Ultra Wideband Multiple Access Performance Using Time Hopped-Biorthogonal Pulse Position Modulation

The FCC\u27s release of its UWB First Report and Order in April 2002 spawned renewed interest in impulse signaling research. This work combines Time Hopped (TH) multiple access coding with 4-ary UWB Biorthogonal Pulse Position Modulation (TH-BPPM). Multiple access performance is evaluated in a multipath environment for both synchronous and asynchronous networks. Fast time hopping is implemented by replicating and hopping each TH-BPPM symbol NH times. Bit error expressions are derived for biorthogonal TH-BPPM signaling and results compared with previous orthogonal TH-PPM work. Without fast time hopping (NH = 1), the biorthogonal TH-BPPM technique provided gains equivalent to Gray-coded QPSK; improved BER at a given Eb/No and an effective doubling of the data rate. A synchronized network containing up to NT = 15 transmitters yields an average BER improvement (relative to an asynchronous network) of approximately -6.30 dB with orthogonal TH-PPM and approximately 5.9 dB with biorthogonal TH-BPPM. Simulation results indicate that doubling the number of multipath replications (NMP) reduces BER by approximately 3.6 dB. Network performance degrades as NT and NMP increase and synchronized network advantages apparent in the NMP = 0 case diminish with multipath interference present. With fast time hopping (NH \u3e 1) improves BER performance whenever NMP \u3c NH while reducing effective data rate by 1/NH. Compared to the NH = 1 synchronized network, TH-BPPM modulation using NH = 10 provides approximately 5.9 dB improvement at NMP = 0 and approximately 3.6 dB improvement at NMP = 5. At NMP = 10, the BER for the hopped and NH = 1 cases are not statistically different; with NH = 10 hops, BER improvement varies from approximately 0.57 to 0.14 dB (minimal variation between synchronous and asynchronous network performance)

Time-Hopping Multicarrier Code-Division Multiple-Access

A time-hopping multicarrier code-division multiple-access (TH/MC-CDMA) scheme is proposed and investigated. In the proposed TH/MC-CDMA each information symbol is transmitted by a number of time-domain pulses with each time-domain pulse modulating a subcarrier. The transmitted information at the receiver is extracted from one of the, say $M$, possible time-slot positions, i.e., assuming that $M$-ary pulse position modulation is employed. Specifically, in this contribution we concentrate on the scenarios such as system design, power spectral density (PSD) and single-user based signal detection. The error performance of the TH/MC-CDMA system is investigated, when each subcarrier signal experiences flat Nakagami-$m$ fading in addition to additive white Gaussian noise (AWGN). According to our analysis and results, it can be shown that the TH/MC-CDMA signal is capable of providing a near ideal PSD, which is flat over the system bandwidth available, while decreases rapidly beyond that bandwidth. Explicitly, signals having this type of PSD is beneficial to both broadband and ultra-wide bandwidth (UWB) communications. Furthermore, our results show that, when optimum user address codes are employed, the single-user detector considered is near-far resistant, provided that the number of users supported by the system is lower than the number of subcarriers used for conveying an information symbol

Performance Evaluation of Impulse Radio UWB Systems with Pulse-Based Polarity Randomization

In this paper, the performance of a binary phase shift keyed random time-hopping impulse radio system with pulse-based polarity randomization is analyzed. Transmission over frequency-selective channels is considered and the effects of inter-frame interference and multiple access interference on the performance of a generic Rake receiver are investigated for both synchronous and asynchronous systems. Closed form (approximate) expressions for the probability of error that are valid for various Rake combining schemes are derived. The asynchronous system is modelled as a chip-synchronous system with uniformly distributed timing jitter for the transmitted pulses of interfering users. This model allows the analytical technique developed for the synchronous case to be extended to the asynchronous case. An approximate closed-form expression for the probability of bit error, expressed in terms of the autocorrelation function of the transmitted pulse, is derived for the asynchronous case. Then, transmission over an additive white Gaussian noise channel is studied as a special case, and the effects of multiple-access interference is investigated for both synchronous and asynchronous systems. The analysis shows that the chip-synchronous assumption can result in over-estimating the error probability, and the degree of over-estimation mainly depends on the autocorrelation function of the ultra-wideband pulse and the signal-to-interference-plus-noise-ratio of the system. Simulations studies support the approximate analysis.Comment: To appear in the IEEE Transactions on Signal Processin