class Digiproc::Strategies::XORDifferentialEncodingStrategy
Class used as a strategy for differentially encoding a bitstream by XORing it with a time-delayed version of itself: Differentially encode the binary stream using the XOR operator, and then map the binary stream using the equation βn = (2l−1)π %2π, l⩽M, which gives you a mapping of 0=> −π ,1=> π The Differentially Encoded Signal => Cn = Dn ⨁ Cn−1 is the signal mapped to phase as described above. The XOR operation in seeded with a 1
Public Class Methods
Input an array of encoded bits (as strings) Output an array of decoded bits
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 74 def self.decode(bits) encoded = [] for i in 1...bits.length do encoded << (bits[i - 1].to_i.to_s.to_i(2) ^ bits[i].to_i.to_s.to_i(2)).to_s end encoded end
Input is an integer The method calls the `decode_str` method below and inputs a string of the binary of the input integer. The output will be the original bitstream encoded by this encoding strategy in string form
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 53 def self.decode_bits(bits) dencode_str(bits.to_s(2)) end
Input an encoded binary bit stream in string form Output a string of the original bitstream
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 62 def self.decode_str(bits) bits_arr = bits.split("") encoded = [] for i in 1...bits_arr.length do encoded << (bits_arr[i - 1].to_i(2) ^ bits_arr[i].to_i(2)).to_s end encoded.join end
Encoding an incoming array of bits (as strings) into an array of XOR'd bits Requires an input of an array, and has optional arguments of m (number of bits per symbol) And a beginning value (a starting reference phase angle). Outputs an array of XOR'd bits
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 38 def self.encode(arr, m = 2, beginning_val = "1") beginning_val = beginning_val.to_s(2) unless beginning_val.is_a? String encoded = [beginning_val] for i in 0...arr.length do encoded << (encoded.last.to_i(2) ^ arr[i].to_i(2)).to_s end encoded end
Accept an int reprisenting a bit stream. Encode the bits by XORing it with a time delay of itself via the `self.encode_str` method below. The first bit is seeded with a “1”
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 17 def self.encode_bits(bits) encode_str(bits.to_s(2)) end
Input a string of bits Outupt the XOR'd version of the bits, seeded with a beginning “1”
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 24 def self.encode_str(bits) bits_arr = bits.split("") encoded = ["1"] for i in 0...bits_arr.length do encoded << (encoded.last.to_i(2) ^ bits_arr[i].to_i(2)).to_s end encoded.join end
Return a lambda which transforms a bit into a phase Input an integer specifying the number of bits in a symbol Input to the returned lambda should be the symbol value in decimal form Ouptut of the lambda is the encoded phase angle
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 87 def self.phase_shift_eqn(m) ->(l){ (((2.0 * (l+1) - 1.0) / m) % 2) * Math::PI } end
Return a lambda which transforms a pahse into a symbol Input an integer specifying the number of bits in a symbol Input to the returned lambda is the encoded phase angle Output of the lambda is the binary symbol
# File lib/strategies/code/xor_differential_encoding_strategy.rb, line 96 def self.phase_to_sym(m) ->(code){ (((code / (Math::PI)) * m) + 1.0) / 2.0 - 1.0 } end