mirror of
https://github.com/jhshi/openofdm.git
synced 2024-12-19 05:38:10 +00:00
85 lines
2.2 KiB
Python
85 lines
2.2 KiB
Python
|
|
||
|
|
# Authors: Veeresh Taranalli <veeresht@gmail.com>
|
||
|
|
# License: BSD 3-Clause
|
||
|
|
|
||
|
|
"""
|
||
|
|
==================================================
|
||
|
|
Sequences (:mod:`commpy.sequences`)
|
||
|
|
==================================================
|
||
|
|
|
||
|
|
.. autosummary::
|
||
|
|
:toctree: generated/
|
||
|
|
|
||
|
|
pnsequence -- PN Sequence Generator.
|
||
|
|
zcsequence -- Zadoff-Chu (ZC) Sequence Generator.
|
||
|
|
|
||
|
|
"""
|
||
|
|
__all__ = ['pnsequence', 'zcsequence']
|
||
|
|
|
||
|
|
from numpy import array, empty, zeros, roll, exp, pi, arange
|
||
|
|
|
||
|
|
def pnsequence(pn_order, pn_seed, pn_mask, seq_length):
|
||
|
|
"""
|
||
|
|
Generate a PN (Pseudo-Noise) sequence using a Linear Feedback Shift Register (LFSR).
|
||
|
|
|
||
|
|
Parameters
|
||
|
|
----------
|
||
|
|
pn_order : int
|
||
|
|
Number of delay elements used in the LFSR.
|
||
|
|
|
||
|
|
pn_seed : string containing 0's and 1's
|
||
|
|
Seed for the initialization of the LFSR delay elements.
|
||
|
|
The length of this string must be equal to 'pn_order'.
|
||
|
|
|
||
|
|
pn_mask : string containing 0's and 1's
|
||
|
|
Mask representing which delay elements contribute to the feedback
|
||
|
|
in the LFSR. The length of this string must be equal to 'pn_order'.
|
||
|
|
|
||
|
|
seq_length : int
|
||
|
|
Length of the PN sequence to be generated. Usually (2^pn_order - 1)
|
||
|
|
|
||
|
|
Returns
|
||
|
|
-------
|
||
|
|
pnseq : 1D ndarray of ints
|
||
|
|
PN sequence generated.
|
||
|
|
|
||
|
|
"""
|
||
|
|
# Check if pn_order is equal to the length of the strings 'pn_seed' and 'pn_mask'
|
||
|
|
|
||
|
|
pnseq = zeros(seq_length)
|
||
|
|
|
||
|
|
# Initialize shift register with the pn_seed
|
||
|
|
sr = array(map(lambda i: int(pn_seed[i]), xrange(0, len(pn_seed))))
|
||
|
|
|
||
|
|
for i in xrange(seq_length):
|
||
|
|
new_bit = 0
|
||
|
|
for j in xrange(pn_order):
|
||
|
|
if int(pn_mask[j]) == 1:
|
||
|
|
new_bit = new_bit ^ sr[j]
|
||
|
|
pnseq[i] = sr[pn_order-1]
|
||
|
|
sr = roll(sr, 1)
|
||
|
|
sr[0] = new_bit
|
||
|
|
|
||
|
|
return pnseq.astype(int)
|
||
|
|
|
||
|
|
def zcsequence(u, seq_length):
|
||
|
|
"""
|
||
|
|
Generate a Zadoff-Chu (ZC) sequence.
|
||
|
|
|
||
|
|
Parameters
|
||
|
|
----------
|
||
|
|
u : int
|
||
|
|
Root index of the the ZC sequence.
|
||
|
|
|
||
|
|
seq_length : int
|
||
|
|
Length of the sequence to be generated. Usually a prime number.
|
||
|
|
|
||
|
|
Returns
|
||
|
|
-------
|
||
|
|
zcseq : 1D ndarray of complex floats
|
||
|
|
ZC sequence generated.
|
||
|
|
"""
|
||
|
|
zcseq = exp((-1j * pi * u * arange(seq_length) * (arange(seq_length)+1)) / seq_length)
|
||
|
|
|
||
|
|
return zcseq
|