Baseband Hardware Designs in Modernised GNSS Receivers - Global Navigation Satellite Systems: Signal,Theory and Applications - page 48

L1

L1+E1

L5+E5a

L1+L2

E1+E5a

E1+E5

L1+L2+L5

L1+E1+L5+E5

L1+L2+E1+L5 +E5a

L1+L2+E1+L5 +E5

0 200 400 600 800 1000

Power consumption estimate (mW)

Fig. 7. Power consumption for different multi-signal configurations

reduced fanout requirements due to increased clock period etc.) However, if the reduction in
the operating frequency demands a modification in the signal processing chain, then resource
requirements may go up. On the other hand, reduction in the resource utilisation will almost
always help reduce the power consumption.

The next few paragraphs explore some techniques that enable some progress in overcoming
these challenges.

5.4 Resource and power consumption reduction opportunities

5.4.1 Design optimisation of the core correlator blocks

One example of resource reduction is the reference signal mixer for the Galileo E5 signal. The
reference signal mixer should be carefully designed to address the complexity vs. propagation
delay trade-off.

An architecture for the AltBOC(15,10) modulation (used in Galileo E5 and Compass B3 for
example) is shown in Fig. 8. In Fig. 8 it is assumed that the input and the local carrier use two
bits and the succeeding stage is not the last arithmetic operation in the chain and hence the
carrier mixer output can be encoded with three bits. The local reference signal is assumed to
be 2-bit wide which is obtained from a 2-bit subcarrier and 1-bit local code.

The implementation shown in Fig. 8 offers a good trade-off between the complexity
and propagation delay requirements compared to both the brute-force logic type of
implementation and the brute-force single large-size LUT implementation.