On 1/3/2015 6:19 PM, austin aigbe wrote:
I am currently implementing the LTE physical layer in Python (ver 2.7.7).
For the qpsk, 16qam and 64qam modulation I would like to know which is more
efficient to use, between an integer comparison and a list comparison:
Integer comparison: bit_pair as an integer value before comparison
# QPSK - TS 36.211 V12.2.0, section 7.1.2, Table 7.1.2-1
def mp_qpsk(self):
r = []
for i in range(self.nbits/2):
bit_pair = (self.sbits[i*2] << 1) | self.sbits[i*2+1]
if bit_pair == 0:
r.append(complex(1/math.sqrt(2),1/math.sqrt(2)))
elif bit_pair == 1:
r.append(complex(1/math.sqrt(2),-1/math.sqrt(2)))
elif bit_pair == 2:
r.append(complex(-1/math.sqrt(2),1/math.sqrt(2)))
elif bit_pair == 3:
r.append(complex(-1/math.sqrt(2),-1/math.sqrt(2)))
return r
List comparison: bit_pair as a list before comparison
# QPSK - TS 36.211 V12.2.0, section 7.1.2, Table 7.1.2-1
def mp_qpsk(self):
r = []
for i in range(self.nbits/2):
bit_pair = self.sbits[i*2:i*2+2]
if bit_pair == [0,0]:
r.append()
elif bit_pair == [0,1]:
r.append(complex(1/math.sqrt(2),-1/math.sqrt(2)))
elif bit_pair == [1,0]:
r.append(complex(-1/math.sqrt(2),1/math.sqrt(2)))
elif bit_pair == [1,1]:
r.append(complex(-1/math.sqrt(2),-1/math.sqrt(2)))
return r
Wrong question. If you are worried about efficiency, factor out all
repeated calculation of constants and eliminate the multiple comparisons.
sbits = self.sbits
a = 1.0 / math.sqrt(2)
b = -a
points = (complex(a,a), complex(a,b), complex(b,a), complex(b,b))
complex(math.sqrt(2),1/math.sqrt(2))
def mp_qpsk(self):
r = [points[sbits[i]*2 + sbits[i+1]]
for i in range(0, self.nbits, 2)]
return r
--
Terry Jan Reedy
--
https://mail.python.org/mailman/listinfo/python-list
