You are required to write a C++ program that simulates the basic
functionality of a spread spectrum transmission mechanism, commonly
employed in IEEE802.11 Wireless Local Area Networks (WLANs). This
particular example will involve the transmission, autocorrelation and
reception of a seven-element alpha numeric data string.
Initial design ideas
Figure 1 outlines a systemic view of what should be developed:
Figure 1, System overview
The pseudorandom sequence generator (PRSG), and exclusive OR circuits
can be developed from figure 2. (The PRSG should be developed as a
stand-alone function)
Figure 2. Pseudorandom sequence generator and exclusive OR circuits
The autocorrelation function for an 11 bit pseudorandom binary
sequence (PRBS) in figure 1, can be developed from figure 3. (the
autocorrelation function should also be developed as a stand alone
function) Note: the sync signal in figure 3 provides a measure of
autocorrelation i.e. in this example the system is fully correlated
and synchronised when 11 ?A? are obtained in the middle register.
Figure 3. The Autocorrelation function
Program requirements / functionality
1. When executed the program should prompt the user for a seven
element alphanumeric data string.
2. The program should then automatically check for a valid input,
convert the user input to a binary equivalent, and then generate a
PRBS that is a factor of ten times the size of the user input.
3. Having combined the user input with the PRBS via an exclusive OR
function, the data should then pass into the autocorrelation function.
(Note in software this should exist as a looping function that
displays to the user graphically or numerically the process of
autocorrelation)
4. The program user should then prompt the user for a bit stream
offset value (0 to the maximum size of the PRBS) so that the process
of autocorrelation can be observed.
5. Having synchronised the incoming data stream with the known PRBS
the data should then be decoded and displayed to the user. |
