Methods and apparatus for extracting symbols from an SC-FDMA digital communications signal using a maximum likelihood detector

A system for a radio receiver, the system comprising:

• a signal receiving unit configured to receive a digital communication input comprising at least one digital communication signal that includes M data streams of symbols from a N single carrier frequency division multiple access (“SC-FDMA”) transmitters, where M and N are integers and are not necessarily equal to each other, said N transmitters being included in at least one user device;
• and
• a signal processing unit, where the signal processing unit includes:
• a Fourier transform component configured to apply a Fourier transform to the received digital communication input;
• a pre-processing component configured to apply a pre-processing equalization algorithm to the digital communication input after the Fourier transform;
• an inverse Fourier transform component configured to apply an inverse Fourier transform to the digital communication input after the pre-processing;
• an estimating component configured to determine from the inverse transformed digital communication input after the inverse Fourier transform an initial estimate of at least one symbol included in the digital communication input;
• and
• a maximum likelihood detection component configured to receive the initial estimate and to simultaneously model and extract a plurality of the symbols included in the digital communication input using a reduced-complexity maximum likelihood detection (“RC-MLD”) algorithm, where the RC-MLD algorithm is reduced in complexity by incorporating the initial estimate, and by applying the RC-MLD only to a search window that is limited in time within the digital communication input, thereby modeling only a subset of the symbols included in the digital communication input.

A non-transitory computer readable medium storing a computer program, executable by a machine, for operating a radio receiver, the computer program comprising executable instructions which when executed by the machine cause the machine to perform the steps of:

• applying a Fourier transform to a received digital communication input comprising at least one digital communication signal that includes M data streams of symbols transmitted by N single carrier frequency division multiple access (“SC-FDMA”) transmitters, where M and N are integers and are not necessarily equal to each other, said N transmitters being included in at least one user device;
• applying a pre-processing equalization algorithm to the digital communication input after the Fourier transform;
• applying an inverse Fourier transform to the digital communication input after the pre-processing;
• determining from the digital communication input after the inverse Fourier transform an initial estimate of at least one symbol included in the digital communication input;
• and
• using a reduced-complexity maximum likelihood detection (“RC-MLD”) algorithm to simultaneously model and extract a plurality of the symbols included in the digital communication input, where the RC-MLD algorithm is reduced in complexity by incorporating the initial estimate, and by applying the RC-MLD only to a search window that is limited in time within the digital communication input, thereby modeling only a subset of the symbols included in the digital communication input.