Design of a GMSK Receiver Prototype on a Heterogeneous Real-time Multiprocessor Platform

Veer, D. van der (2016) Design of a GMSK Receiver Prototype on a Heterogeneous Real-time Multiprocessor Platform.

Abstract:As computers become faster and smaller, there is an increasing demand for low power computing devices. These devices are used in a broad spectrum of applications; this includes heart rate monitors, home automation and environmental monitoring like air quality measurements. In many cases these devices need to operate for months or years on a small battery. This requires a new generation of ultra low power communication chips. Bluetooth has an update of the standard, Bluetooth Low Energy Long Range (BLR), which increases the range for the low energy mode of Bluetooth. Bluetooth Low Energy and the long range successor are designed specifically for these ultra low power applications. An embedded system which does wireless communication processing must combine high processing speed with low power consumption. The multiprocessor system-on-chip (MPSoC) is increasingly used in low power embedded systems. By integrating multiple processors into one system, high computation power can be achieved while keeping power consumption low. In the CAES research group at the University of Twente research is done on the design of heterogeneous multiprocessor embedded platforms for real-time stream processing applications. One prominent example of these systems is called Starburst. This thesis describes an implementation of a BLR receiver on the Starburst platform. The receiver performs non-coherent differential detection. The different tasks of the receiver are implemented as separate accelerators, connected to the communication ring. An equalizer, convolutional decoder and repetition decoder were added to the receiver and the bit error rate (BER) performance of different receiver configurations was measured. The receiver configuration with the best BER performance is the equalizer with matched filter, which performs 2.5dB less 1 than the theoretical DQPSK BER curve. A receiver architecture was designed and implemented where a different filter can be used for frame detection than for decoding. This increases the frame detection rate when the receiver is used with the matched filter and makes the receiver more resilient to frequency offset. The throughput of the receiver on the Starburst platform was analyzed. The receiver was initially implemented as software tasks running on the Microblaze processors, but was running 6 to 34 times too slow. An implementation of hardware accelerators connected to the communication ring is fast enough and each task required less hardware than a Microblaze processor. The fully functional receiver is able to communicate wireless with a transmitter to play an audio stream. It was used as a demonstrator at the University Booth at the Design, Automation and Test in Europe (DATE) 2015 conference[15]. Further research is required on the low BER performance of the repetition decoder. It would also be interesting to investigate increasing the coding gain of the convolutional decoder. Both repetition and convolutional coding are part of the BLR standard, and the gain of the codes is intended to increase the range. However, the gain of both decoders is lower than expected in the current receiver implementation. It would be interesting to investigate to cause of this and research possible improvements. Another possible way to improve the sensitivity of the receiver is to do coherent detection. There is potentially a significant improvement in sensitivity with coherent detection. It is however not clear how difficult it is to do the phase synchronization required for coherent detection, and how much the increase in hardware costs is.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology, 54 computer science
Programme:Embedded Systems MSc (60331)
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