X hits on this document

PDF document

DigitalCommons@University of Nebraska - Lincoln - page 49 / 69





49 / 69


Chapter 7 Jamming with Noise and Fading Channels

7.1 Introduction

This chapter investigates a sub-optimal method to improve the SESS under the jamming

conditions. The method makes a soft decision on the chip values rather than the bit values

like the systems in the pervious chapters. The only problem with this system is that in

previous simulations, the noise of the channel was assumed to be irrelivate. By adding the

noise and fading into the jamming channel the flaws in the new sub-optimal method are


7.2 Analysis

By looking at the way the PNJ works, we can develop methods to defeat the jammer.

The method that proposed in this section makes decisions on each chip rather than each bit.

Looking at the jammer at the lower jamming duty cycles, it is effective because it is jamming

one chip a large amount, which then gets factored into the decision of the bit. If a decision is

made at the chip level, then each chip is weighed evenly at the bit level. This means that when

the jammer heavily jams one chip, the chip decision will be made and it will only effect the bit

decision by the change on that one chip. In other words, only 1 of the N chips is going to be

wrong. The final bit decision has a better chance of correcting the jammed chip since the

jammed chip contributes a value of 1/N to the final bit decision, rather than the actual jammed

amount. So, the chip values get changed from the receiver voltage to either -1 or 1. Normally

Document info
Document views101
Page views101
Page last viewedMon Oct 24 12:33:34 UTC 2016