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The emergence of in-body medical devices has provided a means of capturing physiological or diagnostic information and streaming this information outside of the body. Currently, electromagnetic-based communications make up the bulk of in-body medical device communication protocols. Traditional electromagnetic-based solutions are limited in their data rates and available power. Recently, ultrasound was investigated as a communication channel for through-tissue data transmission. To achieve real-time video streaming through tissue, data rates of ultrasound need to exceed 1 Mbps. In a previous study, we demonstrated ultrasound communications with data rates greater than 30 Mbps with two focused ultrasound transducers using a large footprint laboratory system through slabs of lossy tissues. While the form factor of the transmitter is also crucial, it is obvious that a large, focused transducer cannot fit within the size of a small in-body medical device. Several other challenges for achieving high-speed ultrasonic communication through tissue include strong reflections leading to multipath effects and attenuation. In this work, we demonstrate ultrasonic video communications using a mm-scale microcrystal transmitter with video streaming supplied by a camera connected to a Field Programmable Gate Array (FPGA). The signals were transmitted through a tissue-mimicking phantom and through the abdomen of a rabbit in vivo. The ultrasound signal was recorded by an array probe connected to a Verasonics Vantage system and decoded back to video. To improve the received signal quality, we combined the signal from multiple channels of the array probe. Orthogonal frequency division multiplexing (OFDM) modulation was used to reduce the receiver complexity under a strong multipath environment. [ABSTRACT FROM AUTHOR]

A novel reception antenna configuration is proposed for achieving high gain and broad beam coverage at the same time. This is accomplished by combining a multibeam array antenna with a diversity receiver. Signals from different beams are merged by diversity receiver in the baseband level using the maximal ratio combining scheme. The proposed approach is implemented by integrating a dual-channel digital TV receiver, a four-dipole array, and a 4 × 4 Butler matrix. Two outputs of the array, which have beam maxima pointing away from the boresight by ±14°, are connected to the two receiver inputs. Sensitivity measurements are conducted for different incident angles to find lowest transmitter power levels permissible for DTV signal demodulation. Measured results of a reference single-beam antenna validates that its angular sensitivity profile is proportional to the antenna gain pattern, and the ones of the diversity receiver-based array confirm that the proposed method can combine receptions of the two beams coherently. The effective 3 dB beamwidth of the implemented antenna is doubled, and the gain maximum is comparable with the single-beam array. [ABSTRACT FROM AUTHOR]

This paper presents an integrated 802.11a compliant receiver integrated circuit (IC), which is capable of processing four antenna signals using RF multiple-input multiple-output (RF-MIMO) schemes. Following four low-noise amplifiers, the weighting is performed using Cartesian vector modulators, whose output signals are combined and down-converted. The baseband filters, variable gain amplifiers (VGAs), a quadrature voltage-controlled oscillator, and digital interfaces are integrated. Experimental results demonstrate the performance of the individual components, as well as the RF-MIMO capabilities of the whole chip. The IC achieves a receiver noise figure of 3.6 dB, a phase noise of -\113 dBc/\Hz at 1-MHz offset, and an equivalent Cartesian weighting precision of 6\,\times\,6 bit. An RF input signal of up to -\35.3 dBm (1-dB compression) can be processed, while the maximum RF path gain amounts to 28.6 dB. The baseband VGA provides further 9–61-dB gain in 64 steps. [ABSTRACT FROM PUBLISHER]

Mobility can induce significant signal-to-noise ratio (SNR) performance degradation in optical wireless (OW) systems based on diffuse as well as spot-diffusing configurations. Two methods (beam angle and beam power adaptation) are introduced to the design of OW multibeam systems to effectively mitigate the mobility-based performance degradation in the presence of ambient light noise, multipath propagation, and shadowing. Simulation results indicate that in an angle diversity multibeam system, the SNR is independent of the transmitter position and can be maximized at all receiver locations when our new methods are implemented. A multibeam power and angle adaptive system (MBPAAS) offers a significant SNR improvement of 29 dB over the traditional line strip multibeam system (LSMS) at a transmitter-receiver separation of 6 m, when both systems employ an angle diversity receiver and operate at 50 Mbit/s. This improvement comes at the cost of complexity. The complexity can be reduced by increasing the beam angle adaptation step size from 2.3° to 26.6° resulting in a typical search time reduction from 12.5 ms to 80 µs when our modified MBPAAS replaces the main MBPAAS. However, a power penalty of 11.7 dB at receiver locations near the room edges and 1.3 dB elsewhere can be induced. An increase in the channel bandwidth from 647 MHz (LSMS) to 5.57 GHz can also be achieved when the two new methods (beam angle and beam power adaptation) are implemented. The increase in channel bandwidth and SNR can enable the OW system to achieve higher data rates and 2.5 Gbit/s and 5 Gbit/s mobile OW systems are shown to be feasible. Furthermore, simulation results prove that our modified MBPAAS can sufficiently combat shadowing and signal blockage. [ABSTRACT FROM AUTHOR]

Optimal receiver diversity combining employing linear channel estimation is examined. Based on the statistical properties of least-squares (LS) and minimum mean square error (MMSE) channel estimation, an optimal diversity receiver for wireless systems employing practical linear channel estimation on Rician fading channels is proposed. The new receiver structure includes the conventional maximal ratio combining receiver as a special case. Exact analytical expressions for the symbol error rates (SERs) of LS and MMSE channel estimation aided optimal diversity combining are derived. It is shown that, if an optimal detector is used, an MPSK wireless system with MMSE channel estimation has the same SER when the MMSE channel estimation is replaced by LS estimation. This is an interesting counter- example to the common perception that channel estimation with smaller mean square error leads to smaller SER. Extensive simulation results validate the theoretical results. [ABSTRACT FROM AUTHOR]

A new method is developed to analyze the performance of partially coherent PSK systems in wireless channels with equal-gain combining diversity receiver. Two performance criteria are considered: the average bit error probability and the probability distribution of the combiner SNR (SNR reliability). Tikhonov-distributed phase error processes are assumed and generalized fading channels including Rayleigh, Rician, and Nakagami-m are investigated. We evaluate the detection loss suffered by the carrier recovery for different SNR reliability levels when BPSK and QPSK systems are used in wireless channels. The analysis is based on a convergent infinite series for the distribution of the sum of random variables. The convergence rate of the proposed series is investigated and the analytical results are presented along with providing results obtained by simulation. [ABSTRACT FROM PUBLISHER]

This synchronous quadrature-phase-shift keying (QPSK) receiver concept allows us to process signals in parallel after electronic demultiplexing. An automatic electronic polarization control with a control time constant in the low microsecond range is provided. It is followed by a phase-locked loop free carrier recovery. An intermediate frequency linewidth tolerance of up to 10-3 times the QPSK symbol rate is expected. Commercially available distributed feedback lasers shall, therefore, suffice. [ABSTRACT FROM PUBLISHER]