function - how to fix this easy digital communication excercise using MATLAB -

function - how to fix this easy digital communication excercise using MATLAB -

i have problem in writing in matlab programme modulates info bits, adds noise demodulates , calculate bit error , symbol error rate. modulation used first should qpsk. have done following,

n=100; databits = randi([0 3],n,1); hmodulator = comm.qpskmodulator; hmodulator.phaseoffset = pi/4; txsig = step(hmodulator, databits); scatterplot(txsig) grid on snrdb=-10 rxsig = awgn(txsig,snrdb); h = comm.qpskdemodulator hh.phaseoffset = pi/4; symdecoded=step(h,rxsig) symerr(symdecoded,databits) biterr(symdecoded, databits)

my first question don't think doing bit error rate , symbol error rate correctly, can help me spot problem is? missing out?

i asked repeat same problem create changes needed create work 16-qam , 64-qam changing parameter called constellation.

i have tried using demod , ddemodce these 2 functions removed matlab? know how proceed?

i dont know why using snrdb=-10 db? seek illustration positive numbers 0 10 20 30, , may save symerr , biterr function proposes [number,ratio] = symerr(x,y) number= numb of error , ratio = bitstx/bitsrx m-qam improve utilize modem.qammod seek help in matlab

best regards , luck

function communication matlab bits