Communications Toolbox

qaskdeco

Demap a message from a QASK square signal constellation

Syntax

• msg = qaskdeco(inphase,quadr,M);
  msg = qaskdeco(inphase,quadr,M,mnmx);
  

Description

msg = qaskdeco(inphase,quadr,M) demaps the message signal msg from the M-ary quadrature amplitude shift keying (QASK) square signal constellation points given in the vectors inphase and quadr. Here inphase lists the in-phase components of the points and quadr lists the corresponding quadrature components. M must be a power of 2. qaskdeco uses the default minimum/maximum value of the in-phase component and quadrature component. The defaults corresponding to small values of M are in the table on the reference page for the function qaskenco.

Note    To see how symbols are mapped to the constellation points, generate a constellation plot using qaskenco(M).

msg = qaskdeco(inphase,quadr,M,mnmx) is the same as the syntax above, except that mnmx specifies the minimum and maximum in-phase and quadrature component values. mnmx is a 2-by-2 matrix of the form shown below.

Examples

The commands below show that qaskdeco and qaskenco are inverse operations.

• msg = [0 3 5 3 2 5]'; M = 8;
  [inphase,quadr] = qaskenco(msg,M); % Map the message.
  newmsg = qaskdeco(inphase,quadr,M) % Demap to recover data.
  
  newmsg =
  
       0
       3
       5
       3
       2
       5
  

See Also
qaskenco, decode, demodmap

primpoly

qaskenco