Roman Merz

Performance comparison of UWB impulse-based multiple access schemes in indoor multipath channels

In this paper, we consider an impulse-based ultra- wideband (UWB) receiver and assess the performance of different multiple access and modulation schemes, including time-hopping pulse position modulation (TH-PPM), time-hopping binary phase shift keying (TH-BPSK), and BPSK-BPSK, under both the additive white Gaussian noise (AWGN) and indoor multipath (CM3) channel assumptions. The assumed receiver combines the received pulses to increase the signal to noise ratio (SNR) and correlates the summed signal with the locally generated template. The performance of the different techniques are estimated using Monte-Carlo simulations and validated by comparing them with the theoretical results obtained for the AWGN channel with the characteristic function (CF) method presented in [1], Amongst other results, we show that the AWGN channel assumption provides rather optimistic results as compared to the more realistic CM3 indoor channel assumption.

Multiuser interference during synchronization phase in UWB impulse radio

This paper analyzes the receivers ability to differentiate between multiple users in ultra-wideband (UWB) impulse radio (IR) during the initial synchronization phase after a cold start, i.e., when the receiver is not yet synchronized with the user of interest. Because of multiple access interference (MAI), the receiver may combine the pulses of other users in a partially coherent way. In this case, the receiver should be able to reject all the interfering users in order to synchronize with the user of interest. For pseudo-random time-hopping (TH) spreading codes, the expected performance of the receiver to differentiate between the user of interest and the interfering users is analyzed and some relations with the code properties are shown. Numerical results for a multipath propagation channel and MAI are provided.

Low power ASIC transmitter for UWB-IR radio communication and positioning

This paper describes a low power Ultra-Wideband Impulse Radio (UWB-IR) Application Specific Integrated Circuit (ASIC) transmitter implemented in UMC 0.18 µm. This transmitter has been designed for low data rate communication applications and indoor positioning systems. It is powered by 1.8 V and its current consumption is 20 mA during pulse transmission and lower than 45 µA the rest of the time. This leads to an average power for the transmitter of less than 85 µW for a 288-pulse burst at a burst repetition rate of 1 Hz. The center frequency and bandwidth of the pulse generated by this transmitter are compliant with the current international regulations (FCC/ECC).

A low-power, low data-rate, Ultra-wideband receiver architecture for indoor wireless systems

In this paper, a novel architecture for a low data-rate, low power consumption Impulse Radio (IR) Ultra-Wideband (UWB) receiver is presented in which the received UWB signal is downconverted to a given intermediate frequency (IF) rather than at baseband. This way, the requirement to implement two separate paths for the in-phase and the quadrature components is removed and the power consumption can be reduced. From the IF, the signal is converted to the digital domain by a set of 24 Redundant Signed Digit (RSD) Analog to Digital Converters (ADCs) working at the pulse repetition rate. The digitized signal is then correlated with a predefined template prior to be fed to the bit detector. The trade-offs for the selection of the IF are highlighted and the BER performance of the proposed receiver is evaluated using simulations in 802.15.3a multipath channels. The expected power consumption for the implementation of the receiver using a CMOS process is also provided.

A programmable receiver for communication systems and its application to impulse radio

The design of a programmable receiver for an ultra wideband (UWB) communication is presented. The receiver is using a fast analog to digital converter (ADC) and a field programmable gate array (FPGA) allowing a rapid performance evaluation for various system architectures and signal processing algorithms. To demonstrate the performance and the versatility of the receiver, a simple communication system and a localization system are implemented. The accuracy of the latter is presented for an indoor environment.

Performance of an Impulse Radio Communication System in the Presence of Gaussian Jitter

In this paper, the bit error rate (BER) performance for an ultra-wide bandwidth (UWB) impulse radio in an additive white Gaussian noise (AWGN) transmission channel and with Gaussian jitter is estimated. The assumed receiver combines the received pulses to increase the signal to noise ratio (SNR) and correlates the received signal with a locally generated template. The resulting performances are discussed separately for a large number and a small number of combined pulses. In the former case, the BER is derived analytically and verified using numerical simulations, and in the latter case, lower bounds for the BER are provided for low and large SNRs. Simulation results are shown to approach asymptotically the provided bounds.

A novel low complexity data demodulation algorithm for pulse position modulation

In this paper, a low complexity data demodulation algorithm is proposed that requires time of arrival information of the received signal exclusively. As an application example, the algorithm is applied to an ultra-wideband impulse radio communication system with pulse position modulation. The algorithm is insensitive to a common time delay for all pulses, that means, it does not require an accurate synchronization between the transmitter and the receiver. For the performance estimation, only a symbol synchronization is assumed, i.e., that there is a priori knowledge which pulse marks the beginning of a received data symbol. The performance of the proposed algorithm is evaluated for straightforward time of arrivals estimators, such as a maximum detector or a threshold detector. It is shown that the proposed algorithm outperforms a least squares algorithm in all considered scenarios. In particular, an increased robustness against additive white Gaussian noise, impulse like noise, and multiuser interference is demonstrated as well as an improved performance for multipath propagation channels.