Indoor Positioning with GNSS-Like Local Signal Transmitters - Global Navigation Satellite Systems: Signal,Theory and Applications - page 329

antenna. A new problem arises: since a high level of interference can occur because of
simultaneous broadcasting of different signals. This can induce severe interference that can
disrupt the signal. If one observes the ACF at the receiver end (see figure 22), there is no
longer one maximal peak for each code length, but N peaks if N is the number of
transmitting repealites (assuming that all the transmissions are included in one code length,
but note that this is necessary for the system).

Repealite Correlation figure with 20 chips delay

1.2

1

0.8

0.6

0.4

0.2

0

-0.2

-20 -10 0 10 20 30 40 50 60 70 80
Delay (code chips)

Fig. 22. The resulting auto-correlation function at the receiver

The system shown in figure 23 uses a signal generator that ensures the synchronisation. A
single signal is sufficient, as in the case of repeaters.

Δ cable Δ cable Δ cable Δ cable Δ 12 Δ 12 Δ 12 Δ 12 Δ 23 Δ 23 Δ 23 Δ 23 Δ 34 Δ 34 Δ 34 Δ 34

Signal
Generator

Signal
Generator

d 3 d 3 d 3 d 3

d 4 d 4 d 4 d 4

d 2 d 2 d 2 d 2

d 1 d 1 d 1 d 1

PRI k = PR j + Δ cable + Σ Δ uw + d k PRI k = PR j + Δ cable + Σ Δ uw + d k PRI k = PR j + Δ cable + Σ Δ uw + d k PRI k = PR j + Δ cable + Σ Δ uw + d k

Receiver Receiver

Fig. 23. The repealite system

With 4 delayed channels the terminal is able to carry out 4 indoor pseudo-range
measurements. These measurements lead to the equations of the system (the notations of
figure 23 are used):