Patent ID: 11916668
Assignee: nan
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 4:
5. A method for communicating over a wireless network supporting train control, the method comprising:
receiving a radio frequency (RF) signal transmitting a packet of data comprising a sequence of bits using a modulation scheme that provides for at least 16 possible discrete symbols, each symbol comprising a group of at least 4 bits, each of the at least 4 bits occupying a predefined bit position in the symbol;
demodulating the RF signal according to the modulation scheme and generating for each received symbol a soft decision of which of the at least 16 possible discrete symbols was received; and
decoding the soft decisions to recover the data in the packet;
wherein demodulating comprises,
generating for received symbol a bit value and reliability information reflecting a probability of the bit value being correct, the reliability information determined by calculating for the bit position a logarithmic likelihood ratio (LLR) of the probability of the bit value being 0 given the received symbol to the probability of the bit value being a 1 value given the received symbol, the LLR being calculated on a basis of all possible symbols that could have a 0 value in the bit position and all possible symbols that could have a 1 in the bit position; and
correcting a bias in the LLR calculation for any one of the bit positions resulting from a difference in the number symbols in a first set of all possible symbols that could have a value of 0 in the bit position and a second set of all possible symbols that could have a value of 1 in the bit position.