Jac Romme

Management of UWB picocell clusters: UCELLS project approach

In this paper the UWB cellular architecture proposed in the IST-UCELLS project is described. This architecture targets to provide Gb/s indoor connectivity employing very low-cost UWB transceivers. The picocell clustering of UWB transmitter overcomes the severe range limitation of stand-alone UWB technology. A photonic analog-to-digital converter (Ph-ADC) is developed in UCELLS for localization, fingerprinting and spectral management of UWB transceivers. This approach minimizes interferences and optimizes the user capacity in the picocell cluster area.

Method to Estimate Impulse-Radio Ultra-Wideband Peak Power

This paper provides a method for estimating peak power for impulse-radio ultra-wideband signals. By analyzing the required measurement procedure, a set of equations is derived, which are verified with simulated and measured results. The IEEE 802.15.4a standard is used as an example. The idiosyncracy of IEEE 802.15.4a is the usage of bursts of pulses. Hence, we in this paper propose a method to correctly analyze it. The deviation from the established calculation is shown together with the advantages of using this new method, which is valid for both frequency- and time-domain analysis. The latter turns out to be the preferred way of working. Using the proposed method enables usage of up to 16-24 dB more pulse amplitude, depending on the equipment available and burst width used.

UWB radio channel characterization and design for intra spacecraft communication

ESA is investigating wireless cable replacement for intra-spacecraft (IS) applications to reduce cable weight, and add flexibility to the subsystem layout. The low emission limit and robustness to highly reflective environments make UWB a potential candidate for cable replacement. Therefore, to validate these assumptions, channel measurements have been conducted in a representative spacecraft; the ESA Venus Express mock-up, which is divided in separate compartments/cavities connected by openings. Channel measurements that cover the entire 3 to 10 GHz UWB spectrum, are conducted for all cavity combinations of the Venus Express. Channel statistics are derived from the measurements. Moreover, the raw channel measurements are used in a hardware-true physical layer (PHY) simulator, based on current Holst Centre - IMEC UWB hardware platform supporting IEEE 802.15.4a standard. The used hardware specification are from the non-coherent setting, employing power detection and integrate and dump in RX for easy synchronization in a highly reflective environment, insensitivity to clock jitter, and robustness against clock offsets at cost of reduced sensitivity. The PHY results correspond well to the outage probability derived from the channel measurements when taking the actual noncoherent setting receiver hardware sensitivity into account. Since most power is in the scattered power, the most dominating factor in IS UWB communication is not the actual position or distance between the antennas, but the minimum number of openings between the cavities. The low mean loss of the measured radio channel combined with the immunity of the UWB air-interface to small-scale-fading, ensures that the signal is always well above the noise floor of the non-coherent setting of the current Holst Centre - IMEC hardware.

UWB pulse amplitude estimation method for IEEE 802.15.4a

This paper presents a novel mathematical model to relate pulse amplitude of impulse radio UWB signals to peak power as limited by regulatory bodies. In contrast to existing methods, this model explicitly takes bursts of pulses into account, as is the case for the signaling scheme in the IEEE 802.15.4a standard. Based on insights obtained using this novel model, it enables the usage of up to 16 to 24 dB higher pulse amplitude for all peak-power limited IR systems, as is the case for a majority of the data rate modes in the IEEE 802.15.4a standard.

Cognitive radio by photonic analog-to-digital conversion sensing

This paper proposes a photonic analog-to-digital converter (Ph-ADC) that can be used for localization, fingerprinting and spectral management applications, indicated for cognitive radio applications. The presented approach comprises a time-stretch Ph-ADC with an optimum configuration of optical and electrical amplification stages. This technique increases the bandwidth and sensibility of electronic ADC and can be used for detecting signals with extremely low power. The usage of the proposed Ph-ADC jointly with cognitive radio algorithms allows to minimize interference and to optimize users capacity in a given picocell cluster area.

Sub-meter UWB localization: Low complexity design and evaluation in a real localization system

Accurate indoor localization is a key component for many applications such as tracking, indoor navigation, home/industrial automation, gaming and intelligent transportation systems. Impulse radio ultrawide-band (IR-UWB) allows sub-meter accurate localization due to its inherent high time resolution. The accuracy of localization depends on the detection moment of the direct path signal (Time Of Arrival: TOA). Many studies focus only on TOA estimation without providing a close to system approach. Unlike these studies, we provide a system compatible solution which takes into account low resources design constraints. In this paper, a) we propose a design for sub-meter localization using 802.15.4a UWB compliant signals, b) we integrate our design in a real localization system and c)we evaluate its accuracy in a real scenario. The proposed design is robust to multipath environment by being on the fly adjustable to the existing channel properties. It accomplishes high accuracy and it is ideal for limited resource systems, meeting the low resources requirements of IEEE 802.15.4a standard. The measured error is around 5-10 cm in a multipath environment for 1 GHz sampling rate. This work is novel and it tries to bridge the gap between theoritical digital signal processing solutions presented in literature and the feasibility of a low cost implementation for sensor nodes.

A multi-GHz 130ppm accuracy FLL for duty-cycled systems

A frequency-locked-loop optimized for output frequency accuracy and locking time is implemented in a 90nm CMOS technology. The output frequency ranges from 7–9.8GHz with a reference frequency at 130MHz. The accuracy of the output frequency is 130ppm, achieved by minimizing and dithering the fine tuning bits of the oscillator. The estimated locking-time is below 50 reference clock cycles, thanks to the frequency locking nature. A binary frequency detector is adopted, lending the FLL naturally to a digital implementation, therefore avoiding the control voltage leakage issue. The measured phase noise @1MHz is −67dBc/Hz. The implementation offers itself a suitable solution for duty-cycled system.

Impulse radio ultra-wideband DC power modeling

Several IEEE standards for modern Wireless Sensor Network (WSN) radios make use of impulse radio ultra-wideband (IR-UWB). To keep power consumption to a minimum, pulses are grouped together in bursts. This paper presents a model used to analyze the relationship between DC power consumption, burst length and link budget for both peak and average power limited systems. Such a model is a crucial ingredient in the design of new wireless systems, when designing for maximum achievable distance with low power consumption. The main conclusions in this paper are that longer bursts turn out not to be more power efficient and an average power limited system gives a higher link budget.

Localization and Fingerprint of Radio Signals Employing a Multichannel Photonic Analog-to-Digital Converter

The fingerprint and localization of radio signals employing a multichannel photonic analog-to-digital converter (ADC) is proposed, analyzed, and demonstrated in a laboratory experiment. The photonic ADC detects the radio signals with high sensitivity in a large bandwidth without down-conversion stages. This is of special interest when processing emerging low-power wireless standards like ultra-wideband (UWB) radio. The optical processing in the multichannel photonic ADC is tailored for the localization and fingerprint of generic radio transmitters when orthogonal-frequency division multiplexing (OFDM) modulation is employed in the transmission. The photonic ADC includes engineered optical and electrical amplification. The experimental work demonstrates that detection of radio signals with -65 dBm power with signal-to-noise ratio better than 20 dB is feasible, which is in good accordance with the theoretical analysis. The multichannel photonic ADC comprises five optical channels which are precisely time-aligned in optical domain achieving 0.23-m spatial resolution (median) in the localization of radio transmitters. The experimental work also demonstrates that photonic-ADC processing is adequate for OFDM-based UWB radio-signal fingerprint including estimation of the average power, frequency band of operation, and time-frequency hopping pattern if applicable. UWB transmitter localization has been experimentally demonstrated with 0.4-m error.

Real time non-coherent synchronization method in 6–10.6 GHz IR-UWB demonstrator chipset

A theoretical model for non-coherent start-of-frame-delimiter (SFD) detection in IEEE 802.15.4a is presented and closed form solutions for SFD threshold and signal-to-noise ratio (SNR) estimation are derived. The derived results are implemented in an impulse radio ultra wide band (IR-UWB) demonstrator operating in the 6-10.6 GHz UWB band. The demonstrator is designed for low power operation (in the mW range for combined digital base band (DBB) & radio frequency (RF)). The transmitter (TX) RF is duty cycled at pulse level and the receiver (RX) RF is switched to pulse level duty cycling when possible. Moreover, digital TX and RX resources are only switched on when needed. Measurement results are in close agreement with the derived closed form solutions.