Julien Ryckaert

Ultra-wideband channel model for communication around the human body

Using ultra-wideband (UWB) wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no detailed models describing the UWB radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have measured radio propagation around the body in a typical indoor environment and incorporated these results into a simple model. We then implemented this model on a computer and compared experimental data with the simulation results. This paper proposes a simple statistical channel model and a practical implementation useful for evaluating UWB body area communication systems.

Ultra-wide-band transmitter for low-power wireless body area networks: design and evaluation

The successful realization of a wireless body area network (WBAN) requires innovative solutions to meet the energy consumption budget of the autonomous sensor nodes. The radio interface is a major challenge, since its power consumption must be reduced below 100 /spl mu/W (energy scavenging limit). The emerging ultra-wide-band (UWB) technology shows strong advantages in reaching this target. First, most of the complexity of an UWB system is in the receiver, which is a perfect scenario in the WBAN context. Second, the very little hardware complexity of a UWB transmitter offers the potential for low-cost and highly integrated solutions. Finally, in a pulse-based UWB scheme, the transmitter can be duty-cycled at the pulse rate, thereby reducing the baseline power consumption. We present a low-power UWB transmitter that can be fully integrated in standard CMOS technology. Measured performances of a fully integrated pulse generator are provided, showing the potential of UWB for low power and low cost implementations. Finally, using a WBAN channel model, we present a comparison between our UWB solution and state-of-the-art low-power narrow-band implementations. This paper shows that UWB performs better in the short range due to a reduced baseline power consumption.

Human++: autonomous wireless sensors for body area networks

This paper gives an overview of the results of BMECs Human++ research program. This program aims to achieve highly miniaturized and autonomous sensor systems that enable people to carry their personal body area network. The body area network will provide medical, lifestyle, assisted living, sports or entertainment functions. It combines expertise in wireless ultra-low power communications, packaging, 3D integration technologies, MEMS energy scavenging techniques and low-power design techniques.

Characterization of the ultra wideband body area propagation channel

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. In developing these sensors, detailed knowledge of the communication channel is essential. However, there are currently very few measurements describing propagation around the body. To address this problem, we have measured electromagnetic waves traveling near the torso to derive a simple pathless law. The pathless law is then extended to include the influence of arm movements and a surrounding office environment. This paper describes our measurement campaign and the basic characteristics of the body area radio channel.

A 0.65-to-1.4 nJ/Burst 3-to-10 GHz UWB All-Digital TX in 90 nm CMOS for IEEE 802.15.4a

We propose an all-digital UWB transmitter architecture that exploits the low duty cycle of impulse-radio UWB to achieve ultra-low power consumption. The design supports the IEEE 802.15.4a standard and is demonstrated for its mandatory mode. A digitally controlled oscillator produces the RF carrier between 3 and 10 GHz. It is embedded in a phase-aligned frequency-locked loop that starts up in 2 ns and thus exploits the signal duty cycle that can be as low as 3%. A fully dynamic modulator shapes the BPSK symbols in discrete steps at the 499.2 MHz chip rate as required by the standard. The transmitter can operate in any 499.2 MHz band of the standard between 3.1 and 10 GHz, and the generated signal fulfills the emission spectral mask. The jitter accumulation over a burst is below 6 psRMS, which is within specifications. The transmitter was realized in a 1 V 90 nm digital CMOS technology, and its power consumption drawn from a 1 V supply is from 0.65 mW at 3.1 GHz to 1.4 mW at 10 GHz for a 1 Mb/s data rate.

A 2-mm

A software-defined radio (SDR) should theoretically receive any modulated frequency channel in the (un)licensed spectrum, and guarantee top performance with energy savings, while still being integrated in a digital CMOS technology. This paper demonstrates a practical 0.1-5 GHz front-end implementation for such an SDR concept, including receiver and local oscillator (LO), with only 2-mm2 core area occupation in a 45-nm CMOS process. This scalable radio uses shunt-shunt feedback LNAs, a passive mixer with enhanced out-of-band IIP3, and a fifth order low-area 0.5-20 MHz baseband filter. LO quadrature signals are generated from a dual-VCO 4-10 GHz fractional-N PLL. With noise figure between 2.3 dB and 6.5 dB, out-of-band IIP3 between -3 dBm and -10 dBm, and total power consumption between 59 and 115 mW from a 1.1-V supply voltage, the presented prototype favorably compares with state-of-the-art dedicated radios while enabling, for the first time, wideband reconfigurable performance and energy scalability.

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Using wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no models describing the radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have simulated electromagnetic wave propagation around the body and incorporated these results into a simple model. We then compared this model with measurements taken around the human torso and with previous studies in the literature. This paper proposes a simple statistical channel model useful for evaluating both UWB and (after resampling) narrow-band body area communication systems.

0.1–5 GHz Software-Defined Radio Receiver in 45-nm Digital CMOS

A low-power impulse-radio ultra-wideband receiver is demonstrated for low data-rate applications. A topology selection study demonstrates that the quadrature analog correlation is a good receiver architecture choice when energy consumption must be minimized. The receiver operates in the 3.1-5 GHz band of the UWB FCC spectrum mask on channels of 500 MHz bandwidth. The pulse correlation operation is done in the analog domain in order to reduce the ADC sampling speed down to the pulse repetition rate, thereby reducing the power consumption. The receiver comprises a low-noise amplifier with full on-chip matching network, an RF local oscillator generation, two quadrature mixers, two analog baseband chains followed by two ADCs, and a clock generation network. The receiver is implemented in 0.18 mum CMOS technology and achieves 16 mA power consumption at 20 Mpulses/s pulse repetition rate.

Ultra wide-band body area channel model

This paper gives an overview of results of the Human++ research program [1]. This research aims to achieve highly miniaturized and autonomous transducer systems that assist our health and comfort. It combines expertise in wireless ultra-low power communications, 3D integration technologies, MEMS energy scavenging techniques and low-power design techniques.

A CMOS Ultra-Wideband Receiver for Low Data-Rate Communication

A sixth-order RF bandpass DeltaSigma ADC operating on the 2.4 GHz ISM band, which is suitable for RF digitization is presented. The bandpass loop filter is based on digitally programmable Gm-LC resonators that can be calibrated online to adjust the RF center frequency. By sampling below the input Nyquist frequency, the clock in the system was reduced to 3 GHz, allowing a large reduction of the power consumption. Implemented in a standard 90 nm CMOS process, the IC achieves 40 dB and 62 dB of SNDR and SFDR, respectively, on a 60 MHz bandwidth with 40 mW of power consumption leading to a FoM of 245 GHz/W (4.1 pJ/conversion step). This implementation paves a possible way towards direct RF digitization receiver architectures.