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shift registers of N taps, where N is the number of bits in the decoding sequence, to provide an

estimate of the spreading sequence required for signal de-spreading. The shift register contents

at the transmitter and the receiver should be set initially to be identical.

3.3 SESS Performance Analysis

The issue with SESS is that the performance is impacted at low signal to noise ratios by

error propagation. When the receiver detects a bit incorrectly that error is inserted into the

decoding sequence and it continues to affect the decoding process until it is shifted out of the

sequence N bits later. The signal attenuation depends on the chip length. This means for large

N, a chip error would remain in the register longer, but would contribute to a smaller attenuation.

Inversely, for a small N value a chip error would rotate out of the register quickly, but would

contribute to a larger attenuation. Figure 6 below shows the effects of the sequence length.

Figure 6 Effects of Chip Length on SESS

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