Baseband Hardware Designs in Modernised GNSS Receivers - Global Navigation Satellite Systems: Signal,Theory and Applications - page 43

number of accumulators remains the same if the CM and CL correlation values are combined
(the spreading codes can be combined in time similar to what is done at the transmitter).
However, the combination will lead to data bit ambiguity problem (Dempster, 2006). When
the components are combined, the increase in the power consumption with respect to the
L2C- CM only signal case is negligible. If both the CM and the CL signal components are
processed independently then the resource utilisation almost doubles compared to the CM
only processing.
4.3 Galileo E1
4.3.1 Single signal component (E1b or E1c)
Because of the use of memory codes, the baseband can eliminate the shift register and store
the local spreading code in memory. Therefore there is a small saving in terms of the
flip-flops/registers compared to the GPS L1 C/A architecture. However, because of the 8
MHz sampling frequency requirement assumption, one expects to see an increase in the power
consumption.
4.3.2 Both the signal components (E1b and E1c)
Here two sets of memory codes are used each occupying 4092 bits. In addition the number
of local reference mixers and accumulators are not only doubled, but also need to operate at
higher frequencies due to the higher sampling frequency. For this reason the expected power
consumption is close to twice that of the single signal component (E1b or E1c).
4.4 GPS L5 (pilot and data)
For the GPS L5 signal, the code generator shift register requires 13 bits, which is not a
significant increase from the 10-bits of GPS L1 C/A. However, the major difference is the
higher chipping rate which demands a higher sampling frequency and in turn a higher
correlator operating frequency. Due to the longer code length, the accumulators also have
to be wide compared to that of the GPS L1 C/A correlator. As a result of the increased
operating frequency, the power consumption requirement is expected to drastically increase
though the resource utilisation would go up only slightly more than twice that of the GPS L1
C/A correlator.
4.5 Galileo E5
4.5.1 Galileo E5a or E5b (pilot and data)
For the Galileo E5a and E5b signals, the code generator shift register requires 14-bits. This
is only a 1-bit change from the case of GPS L5 correlator and hence all the other circuit
parameters (such as bit widths) will be very close to that of the GPS L5 correlator. Hence
the expected power consumption for E5a or E5b signal when processed individually, would
be close to that of the GPS L5 correlator.