Ultrasound data communication system for bioelectronic medicines

PhD ThesisThe coming years may see the advent of distributed implantable devices to support bioelectronic medicinal treatments. Such treatments could be complementary and, in some cases, may even prove superior to pharmaceutical treatments for certain chronic disease conditions. Therefore, a significant research effort is being undertaken in the bioelectronics domain. Target conditions include diabetes, inflammatory bowel disease, lupus, and arthritis. Modern active medical implantable devices require communications to transmit information to the outside world or other implantable sub-systems. This can include physiological data, diagnostics, and parameters to optimise the therapeutic protocol. However, the communication scheme can be very challenging especially for deeper devices. Challenges include absorption and scattering by tissue, and the need to ensure there are no undesirable heating effects. Wired connectivity is undesirable and tissue absorption of traditional radio frequency and optical methods mean that ultrasound communications have significant potential in this niche. In this thesis, a reliable and efficient ultrasonic communication telemetry is presented. An omnidirectional transducer has been employed to implement intra body communication inside a model of the human body. A prototype has been implemented to evaluate the system performance in saline and up to 30 distance between the transmitter and receiver. Short pulses sequences with guard intervals have been employed to minimise the multipath effect that leads to an increase in the bit and thus packet error rates with distance. Error detection and correction code have been employed to improve communication at a low signal to noise ratio. The data rate is limited to 0.6 due to the necessary guard intervals. Energy per bit and current consumption for the transmitter and receiver main parts are presented and discussed in terms of battery life. Transmission can be achieved at an energy cost of 642 per bit data packet using on/off power cycling in the electronics

Microelectronic Implementation of Dicode PPM System Employing RS Codes

Optical fibre systems have played a key role in making possible the extraordinary growth in world-wide communications that has occurred in the last 25 years, and are vital in enabling the proliferating use of the Internet. Its high bandwidth capabilities, low attenuation characteristics, low cost, and immunity from the many disturbances that can afflict electrical wires and wireless communication links make it ideal for gigabit transmission and a major building block in the telecommunication infrastructure. A number of different techniques are used for the transmission of digital information between the transmitter and receiver sides in optical fibre system. One type of coding scheme is Pulse Position Modulation (PPM) in which the location of one pulse during 2M time slots is used to convey digital information from M bits. Although all the studies refer to advantages of PPM, it comes at a cost of large bandwidth and a complicated implementation. Therefore, variant PPM schemes have been proposed to transmit the data such as: Multiple Pulse Position Modulation (MPPM), Differential Pulse Position Modulation (DPPM), Pulse Interval Modulation (PIM), Digital Pulse Interval Modulation (DPIM), Dual Header Pulse Interval Modulation (DH-PIM), Dicode Pulse Position Modulation (DiPPM). The DiPPM scheme has been considered as a solution for the bandwidth consumption issue that other existing PPM formats suffer from. This is because it has a line rate that is twice that of the original data rate. DiPPM can be efficiently implemented as it employs two slots to transmit one bit of pulse code modulation (PCM). A PCM conversion from logic zero to logic one provides a pulse in slot RESET (R) and from one to zero provides a pulse in slot SET (S). No pulse is transmitted if the PCM data is unvarying. Like other PPM schemes, DiPPM suffers from three types of pulse detection errors wrong slot, false alarm, and erasure. The aim of this work was to build an error correction system, Reed Solomon (RS) code, which would overcome or reduce the error sources in the DiPPM system. An original mathematical program was developed using the Mathcad software to find the optimum RS parameters which can improve the DiPPM system error performance, number of photons and transmission efficiency. The results showed that the DiPPM system employing RS code offered an improvement over uncoded DiPPM of 5.12 dB, when RS operating at the optimum code rate of approximately ¾ and a codeword length of 25 symbols. Moreover, the error performance of the uncoded DiPPM is compared with the DiPPM system employing maximum likelihood sequence detector (MLSD), and RS code in terms of number of photons per pulse, transmission efficiency, and bandwidth expansion. The DiPPM with RS code offers superior performance compared to the uncoded DiPPM and DiPPM using MLSD, requiring only 4.5x103 photons per pulse when operating at a bandwidth equal to or above 0.9 times the original data rate. Further investigation took place on the DiPPM system employing RS code. A Matlab program and very high speed circuit Hardware Description language (VHDL) were developed to simulate the designed communication system. Simulation results were considered and agreed with the previous DiPPM theory. For the first time, this thesis presents the practical implementation for the DiPPM system employing RS code using Field Programmable Gate Array (FPGA)

Hybrid pulse interval modulation-code-division multiple-access for optical wireless communications.

The work in this thesis investigates the properties of the IR diffuse wireless link with regard to: the use of sets of signature sequences with good message separation properties (hence providing low BER), the suitability of a hPIM-CDMA scheme for the IR diffuse wireless systems under the constraint of eye safety regulations (i.e. when all users are transmitting simultaneously), the quality of message separation due to multipath propagation. The suitability of current DS-CDMA systems using other modulation techniques are also investigated and compared with hPIM-CDMA for the performances in power efficiency, data throughput enhancement and error rate.A new algorithm has also been proposed for generating large sets of (n,3,1,1)OOC practically with reduced computation time. The algorithm introduces five conditions that are well refined and help in speeding up the code construction process. Results for elapsed computation times for constructing the codes using the proposed algorithm are compared with theory and show a significant achievement. The models for hPIM-CDMA and hPPM-CDMA systems, which were based on passive devices only, were also studied. The technique used in hPIM-CDMA, which uses a variable and shorter symbol duration, to achieve higher data throughput is presented in detail. An in-depth analysis of the BER performance was presented and results obtained show that a lower BER and higher data throughput can be achieved. A corrected BER expression for the hPPM-CDMA was presented and the justification for this detailed. The analyses also show that for DS-CDMA systems using certain sets of signature sequences, the BER performance cannot be approximated by a Gaussian function