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Notice the performance in relation to the AWGN line in Figure 16. With the jamming

duty cycle at 100 percent, the performance is the same as in an AWGN channel (See Figure 10

on page 24). The improvement of the system can be seen when comparing Figure 16 against

Figure 14. The SESS with the iterative detector improves the worst-case jamming by 6 db at a

BER of 10-3 (difference can also be seen in Equations 12 and Equation 13).

6.3 Discussion

The Rayleigh fading of SESS and the worst-case jamming are very close in terms of

channel performance. The 6 db improvement of the iterative detector in worst-case jamming still

lacks the 15 db improvement that was seen in the Rayleigh fading channel (Figure 12 on page

25). At a first glance it appears that since the PNJ uses band-limited white Gaussian noise, the

performance of the iterative in the presence mocks that of the AWGN as they both use white

Gaussian noise. However, by investigating the way the hard bit decision is made in the SESS

systems can give insight to the possible difference in the BER performance.

In a DSSS system, the data is multiplied with the spreading sequence to effectively

spread the signal over a larger bandwidth. To retrieve the data on the receiver side, the dot

product, or summing the products of their respective components (For example if = (, ) and

  • = (, ), the dot product is represented as:  ∙  =  ∗  +  ∗ ), is taken from the received

signal and the spreading code. An example of this can be found by letting = -1 stand for the

bit to be transmitted and letting = (1, 1,1,1) represent the spreading sequence. In order to

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