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A chipset including a low power asymmetrical QPSK/OOK transceiver SoC and a 15:1 JPEG image encoder IC is presented for wireless capsule endoscopy. The proposed asymmetrical bi-directional telemetry link supports high-data-rate image transmission with QPSK modulation and low-data-rate actuator control data reception with OOK modulation. To transmit high-quality images with high spectral efficiency, a low power JPEG encoder with compression ratio as high as 15:1 is employed to compress raw image data with subsampling technique in YUV color plane. Implemented in 0.18-μm CMOS, the QPSK TX consumes 5 mW at -6 dBm of output power with 3Mb/s data rate while the OOK RX achieves -60 dBm of sensitivity at 500-kb/s data rate with 6-mW power consumption. A prototype capsule system has been implemented for wireless endoscopy using the developed chipset. With duty cycling, the average power consumption of TX is 2.5 mW when transmitting at 3-fps frame rate.

As Gaussian minimum shift keying (GMSK) modulation scheme is adopted for wireless body area network (WBAN) applications, simple and noise-robust synchronisation algorithms for GMSK are desired to meet the limited resources of power, storage and size in WBAN. However, the current synchronisation algorithms for GMSK are either too complicated or have unsatisfactory performance for low signal-to-noise ratio (SNR), especially for coded GMSK systems. The authors will propose the synchronisation algorithms for general GMSK systems with three unknown synchronisation parameters, namely, timing, frequency and phase offsets estimation. By incorporating noise/interference-reduction methods, the authors propose low-complexity synchronisation algorithms for GMSK that can achieve satisfactory performance in low SNR region. Furthermore, their new feedforward timing and frequency recovery algorithms can provide much better performance than those in the literature by using reliability-measuring mechanism for timing estimation and two-phase frequency estimation. The data-aided Cramer–Rao bounds (CRBs) for the joint estimation of GMSK synchronisation parameters are also derived. The numerical results show that the performance of their proposed synchronisation algorithms is close to the CRBs. The overall bit error rate performance for both uncoded and Bose-Chaudhuri-Hocquenhem BCH-coded GMSK systems are examined. The performance loss owing to synchronisation errors can be reduced to about 1 dB with their proposed algorithms.

As Gaussian minimum shift keying (GMSK) modulation scheme is adopted for body area network (BAN) applications, fast and power efficient synchronization algorithms for GMSK are desired considering the limited resources in BAN. We propose new synchronization algorithms for GMSK with the constraints of low complexity and low signal-to-noise ratio. Our new feedforward timing and frequency recovery algorithms can provide much better performance than those with similar complexity in the literature. The overall bit error rate (BER) performance of the GMSK system is within 1 dB loss compared to that with perfect synchronization.

We propose a symbol-by-symbol (SBS) detector for Gaussian minimum shift keying (GMSK) signals in body area networks (BAN). Our detector exploits the orthogonality between adjacent GMSK-modulated symbols. By dividing the received signals into inphase-/quadrature-channels and odd-/even-streams, the strongest inter-symbol interference (ISI) from the adjacent symbols is removed. A whitened matched filter is designed, and a decision-feedback scheme is proposed to further reduce the residue ISI. This SBS detector has much lower complexity than the conventional maximum likelihood sequence detection schemes using the Viterbi algorithm. Its performance can approach the MSK/BPSK performance which results in high energy efficiency. Thus, our proposed energy-efficient, low-complexity, SBS GMSK demodulator is suitable for BAN which have very limited resources. Based on our demodulator's structure, several other SBS detectors can be obtained straightforwardly.

IEEE 802.15.4a Task Group is defining an ultra low power consumption and low cost radio for Wireless Personal Area Networks (WPANs) applications using Ultra-wideband (UWB) technology with high precision ranging capability. Ternary preamble sequences of two different lengths have been proposed and adopted in the IEEE 802.15.4a specification for ranging. In order for a IEEE 802.15.4a low cost UWB device to support multiple frequency bands across the available spectrum and ranging features, as many as twenty-four ternary sequences is required. A sizeable amount of memory is needed to store the codes. In this paper, we propose a method to generate the ternary codes using linear feedback shift registers (LFSRs) as and when it is required, resulting in significant memory savings. The ranging performance using the proposed ternary preamble sequence is evaluated through simulation.

In this paper, a new pulse-based UWB system is proposed with low power ranging. The ternary sequence based common signaling is proposed to support power efficient energy detectors, differential detectors, and coherent detectors simultaneously. The preamble for ranging is designed to have good autocorrelation properties. The on-off keying based power efficient modulation is combined with chip mapping/spreading to provide robust system performance even in a multipath fading channel. Furthermore, a low complexity energy detection receiver structure is elaborated for leading edge detection in a multipath rich channel. System simulations are performed to demonstrate the promising performance of the proposed system