Block 2

Question 1

BER - Bit Error Rate

Answer 1

In digital communications the BER is the number of bits received in error divided by the number of bits transmitted

Question 2

FEC - Forward Error Correction

Answer 2

FEC is a method of error control whereby a receiver can correct errors in received data without the need for requesting data re-transmission.

FEC allows errors to be corrected where there is no return channel and without the delay incurred by requesting re-transmission.

Question 3

(n,k) notation

Answer 3

n this is the digits in the code word
k this is the message digits

n - k = m
m is the parity digits

Question 4

code rate in n k notation

Answer 4

The code rate is k/n

The higher the code rate the lower the redundancy as more of the code is used for message digits

Question 5

Code redundancy

Answer 5

Code redundancy

R = (n-k) / n

Where
R is the code redundancy
n is the digits in the code word
k is the message digits

Question 6

Hamming code expressed as an equation

Answer 6

n = 2^m - 1

Where
n is the digits in the code word
m is the parity digits

Question 7

Parity Check

Answer 7

A further bit is added to a code word. This is the parity bit. It is chosen so that the total number of 1’s in the code word are even. That is, Even parity.

Odd parity is the same principle however the resulting code word will have an uneven number of 1’s