Baseband Hardware Designs in Modernised GNSS Receivers - Global Navigation Satellite Systems: Signal,Theory and Applications - page 51

6. Summary
This chapter analysed the core correlator complexities of modernised GNSS receiver baseband
hardware. A core correlator architecture description has been given and the number of bits
for the accumulator has been derived. Power consumption estimates were provided for the
new signals at the core correlator level and at the channel level.
It was shown that a GPS and Galileo civil signal receiver baseband would consume
approximately 38 times the power of a GPS L1 C/A baseband. The dominant contributor
to this increased complexity and power consumption is the Galileo E5 AltBOC signal. In
addition, implementation of the core baseband signal processing blocks in FPGA hardware
reveals up to eight times the resource requirement compared to the GPS L1 C/A only
correlator.
It is possible to optimise the hardware targeting the power consumption with the help of
resampling and external aiding. However, the performance trade-off should be carefully
looked into. Because the enormous resource and power consumption for the Galileo E5
AltBOC correlator is due to the signal structure itself, it is of interest to explore efficient
alternatives to the AltBOC signal and one such attempt is made in Shivaramaiah (2011).
Even if a dedicated Application Specific Integrated Circuit (ASIC) replaces the FPGA
baseband hardware, as a rule of thumb, and the authors' own experience with multiple
generations of GPS L1 C/A correlator ASIC design, there will be a best case reduction of the
FPGA power consumption by a factor of 5. In other words, a baseband ASIC will consume
about 100 mW for the L1-L5 and about 200-mW for the all civil GPS+Galileo baseband.
This power consumption is very high given that it is only for the baseband hardware and
not for the entire receiver. Finally, if other global and regional satellite navigation systems
(such as GLONASS, Compass, QZSS, IRNSS) are included, then, the “200 times” estimate
of Dempster (2007) would not be far away. Hence it can be concluded that development
of a baseband hardware for the commercial general purpose multi-GNSS receiver is still a
challenging task. A direction towards a promising solution would be to explore the correlator
level reconfigurability across the GNSS signals.
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