1 files changed, 143 insertions, 0 deletions
diff --git a/gr-trellis/src/examples/test_turbo_equalization.py b/gr-trellis/src/examples/test_turbo_equalization.py
new file mode 100755
index 000000000..ff0497e2b
--- /dev/null
+++ b/gr-trellis/src/examples/test_turbo_equalization.py
@@ -0,0 +1,143 @@
+#!/usr/bin/env python
+
+from gnuradio import gr
+from gnuradio import audio
+from gnuradio import trellis
+from gnuradio import eng_notation
+import math
+import sys
+import fsm_utils
+
+
+def make_rx(fg,fo,fi,dimensionality,tot_constellation,K,interleaver,IT,Es,N0,type):
+    metrics_in = trellis.metrics_f(fi.O(),dimensionality,tot_constellation,trellis.TRELLIS_EUCLIDEAN) # data preprocessing to generate metrics for innner SISO
+    scale = gr.multiply_const_ff(1.0/N0)
+    gnd = gr.vector_source_f([0],True);
+
+    inter=[]
+    deinter=[]
+    siso_in=[]
+    siso_out=[]
+
+    # generate all blocks
+    for it in range(IT):
+      inter.append( trellis.permutation(interleaver.K(),interleaver.INTER(),fi.I(),gr.sizeof_float) )
+      siso_in.append( trellis.siso_f(fi,K,0,-1,True,False,type) )
+      deinter.append( trellis.permutation(interleaver.K(),interleaver.DEINTER(),fi.I(),gr.sizeof_float) )
+      if it < IT-1:
+        siso_out.append( trellis.siso_f(fo,K,0,-1,False,True,type) )
+      else:
+        siso_out.append( trellis.viterbi_s(fo,K,0,-1) ) # no soft outputs needed
+
+    # connect first stage
+    fg.connect (gnd,inter[0])
+    fg.connect (metrics_in,scale)
+    fg.connect (scale,(siso_in[0],1))
+
+    # connect the rest
+    for it in range(IT):
+      if it < IT-1:
+        fg.connect (metrics_in,(siso_in[it+1],1))
+        fg.connect (siso_in[it],deinter[it],(siso_out[it],1))
+        fg.connect (gnd,(siso_out[it],0))
+        fg.connect (siso_out[it],inter[it+1])
+        fg.connect (inter[it],(siso_in[it],0))
+      else:
+        fg.connect (siso_in[it],deinter[it],siso_out[it])
+        fg.connect (inter[it],(siso_in[it],0))
+   
+    return (metrics_in,siso_out[IT-1])
+
+
+def run_test (fo,fi,interleaver,Kb,bitspersymbol,K,dimensionality,tot_constellation,Es,N0,IT,seed):
+    fg = gr.flow_graph ()
+
+    # TX
+    src = gr.lfsr_32k_source_s()
+    src_head = gr.head (gr.sizeof_short,Kb/16) # packet size in shorts
+    s2fsmi = gr.packed_to_unpacked_ss(bitspersymbol,gr.GR_MSB_FIRST) # unpack shorts to symbols compatible with the iouter FSM input cardinality
+    enc_out = trellis.encoder_ss(fo,0) # initial state = 0
+    inter = trellis.permutation(interleaver.K(),interleaver.INTER(),1,gr.sizeof_short)
+    enc_in = trellis.encoder_ss(fi,0) # initial state = 0
+    # essentially here we implement the combination of modulation and channel as a memoryless modulation (the memory induced by the channel is hidden in the innner FSM)
+    mod = gr.chunks_to_symbols_sf(tot_constellation,dimensionality)
+
+    # CHANNEL
+    add = gr.add_ff()
+    noise = gr.noise_source_f(gr.GR_GAUSSIAN,math.sqrt(N0/2),seed)
+    
+    # RX
+    (head,tail) = make_rx(fg,fo,fi,dimensionality,tot_constellation,K,interleaver,IT,Es,N0,trellis.TRELLIS_MIN_SUM) 
+    fsmi2s = gr.unpacked_to_packed_ss(bitspersymbol,gr.GR_MSB_FIRST) # pack FSM input symbols to shorts
+    dst = gr.check_lfsr_32k_s(); 
+    
+    fg.connect (src,src_head,s2fsmi,enc_out,inter,enc_in,mod)
+    fg.connect (mod,(add,0))
+    fg.connect (noise,(add,1))
+    fg.connect (add,head)
+    fg.connect (tail,fsmi2s,dst)
+    
+    fg.run()
+
+    ntotal = dst.ntotal ()
+    nright = dst.nright ()
+    runlength = dst.runlength ()
+    #print ntotal,nright,runlength 
+    
+    return (ntotal,ntotal-nright)
+
+
+
+
+def main(args):
+    nargs = len (args)
+    if nargs == 3:
+        fname_out=args[0]
+        esn0_db=float(args[1])
+        rep=int(args[2])
+    else:
+        sys.stderr.write ('usage: test_turbo_equalization.py fsm_name_out Es/No_db  repetitions\n')
+        sys.exit (1)
+
+    # system parameters
+    Kb=64*16  # packet size in bits (multiple of 16)
+    modulation = fsm_utils.pam4 # see fsm_utlis.py for available predefined modulations
+    channel = fsm_utils.c_channel # see fsm_utlis.py for available predefined test channels
+    fo=trellis.fsm(fname_out) # get the outer FSM specification from a file
+    fi=trellis.fsm(len(modulation[1]),len(channel)) # generate the FSM automatically
+    if fo.O() != fi.I():
+        sys.stderr.write ('Incompatible cardinality between outer and inner FSM.\n')
+        sys.exit (1)
+    bitspersymbol = int(round(math.log(fo.I())/math.log(2))) # bits per FSM input symbol
+    K=Kb/bitspersymbol # packet size in trellis steps
+    print 'size = ',K
+    interleaver=trellis.interleaver(K,666) # construct a random interleaver
+    tot_channel = fsm_utils.make_isi_lookup(modulation,channel,True) # generate the lookup table (normalize energy to 1)
+    dimensionality = tot_channel[0]
+    tot_constellation = tot_channel[1]
+    if len(tot_constellation)/dimensionality != fi.O():
+        sys.stderr.write ('Incompatible FSM output cardinality and lookup table size.\n')
+        sys.exit (1)
+    N0=pow(10.0,-esn0_db/10.0); # noise variance
+    IT = 3 # number of turbo iterations
+
+    tot_s=0 # total number of transmitted shorts
+    terr_s=0 # total number of shorts in error
+    terr_p=0 # total number of packets in error
+
+    for i in range(rep):
+        (s,e)=run_test(fo,fi,interleaver,Kb,bitspersymbol,K,dimensionality,tot_constellation,1,N0,IT,-long(666+i)) # run experiment with different seed to get different noise realizations
+        print s
+        tot_s=tot_s+s
+        terr_s=terr_s+e
+        terr_p=terr_p+(terr_s!=0)
+        if ((i+1)%10==0) : # display progress
+            print i+1,terr_p, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)
+    # estimate of the (short or bit) error rate
+    print rep,terr_p, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)
+
+
+
+if __name__ == '__main__':
+    main (sys.argv[1:])
+