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Unformatted text preview: across samples, i.e., the samples at the receiver are perturbed by additive white Gaussian noise.
For onoff signaling, V0 = 0 and V1 = V . The linearity of the channel then ensures that for bipolar signaling
V0 = −V and V1 = V .
The receiver decides on whether a “0” or “1” was sent by comparing the average value of the M samples in
any bit slot with a threshold voltage Vth . If the average is below Vth , the receiver decides a “0” was sent; if
the average is above Vth , the receiver decides a “1” was sent.
Suppose we are using bipolar signaling and M = 1, i.e., only a single sample is taken in each bit slot.
Then you’ve seen that the probability of the receiver making an error in deciding whether a “0” or “1” was
sent in any particular bit slot, i.e., the bit error rate (BER), is minimized by choosing Vth = 0, with the
corresponding BER being given by
V
BERbipol = 0.5 erfc √ .
σ2
1. [2 points]: If V is doubled from its original value, by what maximum factor can the...
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This document was uploaded on 03/17/2014 for the course ELECTRICAL 6.02 at MIT.
 Fall '12
 GeorgeVerghese

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