Nauman F. Kiyani

9.7 A 0.33nJ/b IEEE802.15.6/proprietary-MICS/ISM-band transceiver with scalable data-rate from 11kb/s to 4.5Mb/s for medical applications

The introduction of the IEEE802.15.6 standard (15.6) for wireless-body-area networks signals the advent of new medical applications, where various wireless nodes in, on or around a human body monitor vital signs. Radio communication often dominates the power consumption in the nodes, thus low-power transceivers are desired. Most state-of-the-art low-power transceivers support only proprietary modes with OOK or FSK modulations, and have poor sensitivity or low data rate [1,2]. In this work, a 15.6-compliant transceiver with enhanced performance is proposed. First, the data-rate is extended to 4.5Mb/s to cover multi-channel EEG applications. Second, while a best-in-class energy efficiency of 0.33nJ/b is achieved in the high-speed mode, a dedicated low-power mode reduces the RX power further in low-data-rate operation. Third, a sensitivity 5 to 10dB better than the 15.6 specification is targeted to accommodate extra path loss due to shadowing effects from human bodies.

A 0.33 nJ/bit IEEE802.15.6/Proprietary MICS/ISM Wireless Transceiver With Scalable Data Rate for Medical Implantable Applications

This paper presents an ultra-low power wireless transceiver specialized for but not limited to medical implantable applications. It operates at the 402-405-MHz medical implant communication service band, and also supports the 420-450-MHz industrial, scientific, and medical band. Being IEEE 802.15.6 standard compliant with additional proprietary modes, this highly configurable transceiver achieves date rates from 11 kb/s to 4.5 Mb/s, which covers the requirements of conventional implantable applications. The phase-locked loop-based transmitter architecture is adopted to support various modulation schemes with limited power budget. The zero-IF receiver has programmable gain and bandwidth to accommodate different operation modes. Fabricated in 40-nm CMOS technology with 1-V supply, this transceiver only consumes 1.78 mW for transmission and 1.49 mW for reception. The ultra-low power consumption together with the 15.6-compliant performance in term of modulation accuracy, sensitivity, and interference robustness make this transceiver competent for various implantable applications.

Performance analysis and measurement results of an ultra-low power wakeup radio in the presence of interference

Wakeup radios (also referred to as event-driven radios) is a paradigm for low-cost, low-energy identification radios to assist the main radio for continuous channel monitoring without sacrificing the latency requirements. Wakeup radios show the potential to extend considerably the life-time of the main radios. In this paper, we present the design, and measurement results of an ultra low-power wakeup radio. The designed wakeup radio achieves excellent performance in terms of probability of miss-detection and probability of false alarm. The designed radio is also analyzed in the presence of co-channel continuous wave and modulated interferer in a wide variety of deployment scenarios. The performance is considerably better than other low-power implementations available in the market.

A 3.72μW ultra-low power digital baseband for wake-up radios

In order to minimize power consumption without sacrificing much latency performance, wake-up radios are employed to assist the main radio for low power channel monitoring. This paper presents the design and implementation of an ultra-low power digital baseband (DBB) circuit for a wake-up radio. In a 90nm CMOS process, the circuit running at a 800kHz clock consumes 3.72μW with a standard 1.2V supply voltage, and achieves very good packet detection performance. The circuit is fully functional at 0.6V supply consuming 0.9μW.

Performance Analysis of OOK Modulated Signals in the Presence of ADC Quantization Noise

This paper investigates the word length requirement of an analog-to-digital (ADC) converter for coherent and non-coherent detection of On-Off Keying (OOK) schemes. The paper presents closed-form expressions for coherent and non-coherent detection in terms of bit error rate in the presence of quantization noise (QN) and additive white Gaussian noise (AWGN) channels. The analytical models show that for coherent as well as non-coherent demodulation of OOK schemes in AWGN channels and affected by QN, a 4-bit ADC is able to provide close to optimum performance. As OOK is popularly being employed in event-driven radios, we extend our analysis to these radios. Our analysis shows that for event-driven radios (also referred to as wakeup radios) a 4-bit ADC is able to provide close to optimum performance. Furthermore, in the paper all the analytical models are in close agreement with the simulation results.

Improving energy-efficiency in building automation with event-driven radio

Sensor, actuator, and radio constitute the three basic components in a building automation system. Among all the three, radio consumes a significant part of the total power. In this paper, an ultra-low power event-driven radio is proposed as a solution to minimize the power consumption of a building automation system. Generic system architecture is formalized according to the application scenario. Event-driven radio is compared against other commercial low power radios. Our analysis shows that significant energy efficiency enhancement is achieved by an event-driven radio. Based on the state of the art micro power technology, possibility of implementing autonomous radio is also investigated in the building automation scenario.

A 3.5mW 315/400MHz IEEE802.15.6/proprietary mode digitally-tunable radio SoC with integrated digital baseband and MAC processor in 40nm CMOS

An energy-efficient, flexible radio SoC with RF front-end (RFFE), digital baseband (DBB) and microcontroller (MCU) for medical/healthcare applications in 315/400 MHz bands is presented. The SoC is fully-compliant with the IEEE 802.15.6 standard in 400MHz bands, and also supports proprietary modes, including high data rate (HDR) modes with x2/4/8 data rates (max 3.6Mb/s) to support applications like EEG, and low-power modes with 1/16 data rate to minimize sensor node power consumption. The total power consumption of 3.5mW (RX, 3.6Mb/s, −77dBm sensitivity) enables best-in-class power efficiency of 1nJ/bit.

Modulation diversity benefits in cooperative communications

In this paper we propose modulation diversity as a candidate diversity scheme for uncoded cooperative communication in wireless networks with decode-and-forward (DF) communication protocol. A performance analysis of such a scheme in Nakagami-m fading channels in the presence of additive white Gaussian noise (AWGN) is presented. An upper bound on the average probability of bit error (Pb) and average probability of symbol error (Ps) is derived for M-ary phase shift keying (MPSK) modulation schemes. It is shown that the system employing employing modulation diversity is able to provide a performance improvement of 5 dB at a bit error rate of 10−4 as compared to the conventional cooperative communication systems. We introduce a power allocation factor and show that equal power allocation is not the optimal solution. Furthermore, we also analyze the effect of different rotation angles and power allocation on the system performance.

Radio channel characterization for 400 MHz implanted devices

The wireless communication channel around/in the human body is a difficult propagation environment. This paper presents measurement and simulation results to characterize such a channel. A fluid human body model is employed to emulate the inside of a human body. The paper details the fluid human model and path loss model parameters at 400 MHz (MICS band). It is shown that the simulated and measured results are in a close agreement, for instance at a distance of 20 cm and a implant depth of 10 cm, the measurement results in a path loss of -42.1 dB and the simulation in -43.0 dB. The effect of human model shape on measured path loss is analyzed. Furthermore, simulations are employed to characterize this effect. Using the path loss model a top-level link budget is evaluated to determine the feasibility of a given implant device compliant to IEEE802.15.6-WBAN-400 MHz standard.

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.