%%%%%%%%%%%%%%%%%%%%%%%%%%%%%?SIMULATION?OF?A?DMT?SYSTEM?%%%%%%%%%%%%%%%%%%%
%%?This?program?starts?off?with?assigning?the?number?of?bits?to?each?subchannel?
%?（bit-loading）in?the?DMT?system.?Since?the?SNR?of?each?subchannel?is?unavailable?
%?this?allocation?is?done?in?a?random?manner.

%?A?random?data?is?generated?for?transmission?through?each?sub-channel.
%?Constellation?Encoding?and?Decoding?were?done?with?the?help?of?a?piece?
%?of?code?available?on?the?Internet.
%?Y.?SRIRAJA?DEC?2001

clear?all;
clc;close?all;
%?For?each?of?N?channels?assign?no.?of?bits?and?genration?of?the?data?stream
%?such?that?sum?of?all?（bits/subchannel）?=?the?data?length.
N=32;?%No.?of?sub-channels
v=5;?%?Cyclic?prefix?length
h1=[1?0.5?0.3?0.2?-0.1?0.02?0.05?0.08?0.01];?%?channel?impulse?response.
k=input（‘1?Ideal?Channel\n??2?Channel?with?length?v+1?\n??3?Channel?with?length?greater?than?v+1?\n‘）;

if?k==1?
????h=[1];
elseif?k==2
????h=h1（1:6）;
elseif?k==3?
????h=h1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%?Bit?Allocation?and?data?generation?%%%%%%%%%%%%%%%%%%%%%
for?i=1:N-1
????%Since?the?SNR?of?each?subchannel?is?unknown?bit?loading?is?random
????bit_channel（i）=ceil（rand*15）;
end
bar（bit_channel‘w‘）;
title（‘Bit?Distribution‘）;
xlabel（‘Channel?Number‘）;
ylabel（‘bits/channel‘）;

fprintf（‘Press?Enter?to?continue‘）
pause
clc
%?Data?assignment?in?each?channel
for?i=1:N-1
????data_channel=[];
????%?data_channel?is?the?particular?data?assigned?to?the?subchannel.
????for?j=1:bit_channel（i）
????????val=round（rand）;
????????data_channel=[data_channel?val];
????end
????%?data?conatains?all?the?data_channel?values.
????data{i}=data_channel;
end
clear?i?j;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%?CONSTELLATION?ENCODING?%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%?Calculate?the?intersymbol?spacing?（based?on?a?transmit?
	%?symbol?energy?of?1）.
for?i=1:N-1
????d?=?sqrt?（6/（（2^bit_channel（i））-1））;
????%?The?number?of?bits?sent?to?the?top?and?bottom?DACs
	bits_top?=?ceil（bit_channel（i）/2）;
	bits_bot?=?floor（bit_channel（i）/2）;
????%?The?actual?binary?data?sent?to?the?top?and?bottom?DACs
	data_top?=?[data{i}（1:bits_top）];
	data_bot?=?[data{i}（bits_top+1:bit_channel（i））];

	%?The?decimal?value?of?the?data?at?the?top?and?bottom?DACs
????
	v_top?=?sum（data_top（1:bits_top）.*（2.^（0:（bits_top-1））））;
	v_bot?=?sum（data_bot（1:bits_bot）.*（2.^（0:（bits_bot-1））））;

	%?The?output?values?of?the?top?and?bottom?DACs
	d_top?=（v_top*d）-（（（2^bits_top-1）/2）*d）;
	d_bot?=（v_bot*d）-（（（2^bits_bot-?1）/2）*d）;

	%?Since?the?top?DAC?output?is?the?amplitude?of?the?cosine?wave
	%?and?the?bottom?DAC?output?is?the?amplitude?of?the?sine?wave?
	%?we?can?consider?them?to?be?the?inphase?and?quadrature?
	%?components?of?the?complex?QAM?symbol.
	i_comp（i）=d_top;
	q_comp（i）=d_bot;
complex_symbol