23 research outputs found
Efficient transmission design for machine type communications in future wireless communication systems
With a wide range of potential applications, the machine type communication (MTC) is gaining
a tremendous interest among mobile network operators, system designers, MTC specialist
companies, and research institutes. The idea of having electronic devices and systems automatically
connected to each other without human intervention is one of the most significant
objectives for future wireless communications. Low data rate transmission and the requirement
for low energy consumption are two typical characteristics for MTC applications. In terms of
supporting low cots MTC devices, industrial standards will be more efficient if designers can
re-use many features of existing radio access technologies. This will yield a cost effective solution
to support MTC in future communication systems. This thesis investigates efficient MTC
waveform and receiver designs for superior signal transmission quality with low operational
costs.
In terms of the downlink receiver design, this thesis proposes a novel virtual carrier (VC) receiver
system for MTC receivers, which aims to reduce the maximum bandwidth to improve
the data processing efficiency and cost-efficiency by using analogue filters to extract only sub-carriers
of interest. For the VC receiver systems, we thus reduce the sampling rate in order
to reduce the number of subsequent processing operations, which significantly reduces the
analogue-to-digital converter (ADC) cost and power consumption while providing high signal
to interference noise ratio (SINR) and low bit to error rate (BER) to support low data rate
MTC devices. Our theoretical equations account for the interference effect of aliasing on the
sub-carrier location, and this helps the system designer to evaluate what kind of filters and
receiver sampling rate can be used to balance the energy cost and detection performance.
In terms of the uplink waveform design, considering the enhanced number of MTC devices
in the future communication systems, i.e. the fifth generation (5G) communications, the same
tight synchronisation as used in today appears not to be cost-effective or even possible. Synchronisation
signals, which aim to provide a perfect time or frequency synchronisation in the
current fourth generation (4G) communication systems (known as the long-term evolution,
LTE), is much more costly for low data rate MTC transmissions. The system bandwidth will be
significantly reduced if a base station tries to synchronise all received signals among hundreds
or thousands MTC devices in one transmission time period. In terms of relaxing the synchronisation
requirements, this thesis compares and analyses the side-lobe reduction performance
for several candidate multi-carrier waveforms to avoid these problems. We also propose the
infinite impulse response universal filtered multi-carrier (UFMC) system and the overlap and
add UFMC system, which significantly reduce the processing complexity compared with the
state of the art UFMC techniques. This thesis derives closed-form expressions for the interference
caused by time offsets between adjacent unsynchronised MTC users. Our analytical
equations can be used in both simple and complex time-offset transmission scenarios, and enable
the system designer to evaluate the SINR, the theoretical Shannon capacity and the BER
performance