Global Positioning System Reference
In-Depth Information
L1C). The transmitted power is shared between two channels. Therefore, if the acquisition
is performed on both channels, then the better sensitivity improvement can be obtained. In
literature, (Mattos, 2005; Ta et al., 2010) use this approach for Galileo E1 OS signal acquisition.
Essentially, for the channel combining acquisition approach (common or different
frequencies), in each involved channel, an acquisition strategy belonging to either the
stand-alone or the external-aiding approach is performed. Then the acquisition outputs from
all the channels are combined in different ways. In Section 6, the joint data/pilot acquisition
strategies for Galileo E1 OS signal is introduced as an example for this approach.
4. Stand-alone approach: Generalized differential combination technique
4.1 Technique description
As seen in (19), the decision variable of the Conventional Differential Combination (CDC)
technique is an accumulation of the products between two consecutive correlator outputs
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. In a broader manner, the Generalized Differential Combination (GDC) has been
introduced (Corazza & Pedone, 2007; Shanmugam et al., 2007). This technique considers the
products of two consecutive correlator outputs as in CDC as well as the products of two
correlator outputs at all sample distances or referred as all possible spans, see Fig. 6(a). Let us
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Fig. 6. Differential Post Correlation Processing Architecture: (a) Differential operations; (b)
Conventional Differential Combination (CDC); (c) Generalized Differential Combination
(GDC); (d) Modified Generalized Differential Combination (MGDC)
define a span-i term as:
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