Channel Models Flashcards
Memoryless Channel
A channel is said to be memoryless if the probability distribution of the output depends only on the input at that time and is conditionally independent of previous channel inputs or outputs.
Symmetric Channel
It has a channel transition matrix where all columns are permutations of each other and all rows are permutations of each other
Name the common channel models
Binary Symmetric Channel
Binary Erasure Channel
Z-Channel
AWGN Channel
Explain the uses of the binary symmetric channel
Used for modelling hard-decision channels
Explain the uses of the binary erasure channel
Used for modelling channels with erasures (e.g. networks with packet losses) or channels with high SNRS and three-level quantization
Explain the uses of the Z-Channel
Very simple model for free-space optical communications
Explain the uses of AWGN Channel
Most common model for most kind of communications systems with analog physical transmissions
Explain the relationship between Es/N0 and Eb/N0
Es: the energy per transmitted code bit
Eb: energy per information bit u
We have k information bits and then when we encode the information, we get n code bits.
Explain the concept of hard decision in BI-AWGN channel
If y tilda is positive = 0
if y tilda is negative = 1
Define the coding gain and net coding gain
Coding gain; the gain in Es/No at a defined target BER compared with uncoded transmission
Net coding gain; gain in Eb/No “ “
Why is the net coding gain smaller?
In the coding gain, we are looking at the raw numbers.
In the net coding gain, we take into account for extra energy/bandwidth to transmit extra energy (parity or dedundant bits)
What does the bhattacharya parameter tell us?
It quantifies the “closeness” of two random samples.
