Maximum likelihood decoding

A method of maximum likelihood decoding for detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of a communication system in which there are N co-channel transmit antennas and M co-channel receive antennas where N and M are integers, comprising the steps of:

• receiving a signal at the M co-channel receive antennas and plotting a corresponding received signal point (y) in an M-dimensional output signal space;
• mapping the received signal point to a corresponding noise corrupted transmit signal point (τ) in an N-dimensional input signal space;
• constructing an orthotope (22) in the input signal space centered on the noise corrupted transmit signal point and having sides parallel to the axes of the input signal space large enough to encompass at least one candidate from an array of possible transmit signal points in the input signal space;
• transforming all the candidate transmit signal points located inside the orthotope into the output signal space to form a set of candidate received signal points;
• calculating the Euclidean distance between each of the candidate received signal points and the received signal point (y);
• and
• selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (y) to be the detected received signal point.

Computer readable media storing a computer program for installation and execution in a digital processor of a receiver detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of a communication system in which there are N co-channel transmit antennas and M co-channel receive antennas where N and M are integers, the computer program containing instructions when executed in the digital processor for carrying out the steps of:

• receiving a signal at the M co-channel receive antennas and plotting a corresponding received signal point (y) in an M-dimensional output signal space;
• mapping the received signal point to a corresponding noise corrupted transmit signal point (τ) in an N-dimensional input signal space;
• constructing an orthotope in the input signal space centered on the noise corrupted transmit signal point, which orthotope has sides parallel to the axes of the input signal space;
• selecting possible transmit signal points from an array of possible transmit signal points in the input signal space by selecting only those possible transmit signal points located inside the orthotope;
• processing the limited candidate set of possible transmit signal points to determine a detected received signal point.

Computer readable media storing a computer program for installation and execution in a digital processor of a receiver of a Multiple-Input-Multiple-Output (MIMO) channel of a communication system in which there are N co-channel transmit antennas and M co-channel receive antennas where N and M are integers for detecting the signals transmitted over the MIMO channel, the computer program containing instructions when executed in the digital processor for carrying out the steps of:

• receiving as an input a signal received from the M co-channel receive antennas and identifying a corresponding received signal point (y) in an M-dimensional output signal space;
• mapping the received signal point to a corresponding noise corrupted transmit signal point (τ) in an N-dimensional input signal space;
• constructing an orthotope (22) in the input signal space centered on the noise corrupted transmit signal point and having sides parallel to the axes of the input signal space large enough to encompass at least one candidate transmit signal point of an array of possible transmit signal points in the input signal space;
• transforming all the candidate transmit signal points located inside the orthotope into the output signal space to form a set of candidate received signal points;
• calculating the Euclidean distance between each of the candidate received signal points and the received signal point (y);
• and
• selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (y) to be the detected received signal point.

A method of maximum likelihood decoding for detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of a communication system in which there are N co-channel transmit antennas and M co-channel receive antennas where N and M are integers, comprising the steps of:

• generating an N-dimensional array of possible transmit signal points in an N-dimensional input signal space and generating a corresponding M-dimensional array of possible receive signal points in an M-dimensional output signal space;
• receiving a signal at the M co-channel receive antennas and plotting a corresponding received signal point (y) in the output signal space;
• constructing a hypersphere (18) in the output signal space centred on the received signal point and having an initial radius (c1/2);
• transforming the hypersphere into the input signal space to construct a corresponding hyperellipsoid (20) in the input signal space;
• constructing an orthotope (22) in the input signal space which is the smallest orthotope which contains the hyperellipsoid (20) and which has sides which are parallel to the axes of the input signal space;
• assessing the array of possible transmit signal points in the orthotope and discarding those which are outside the orthotope to generate a set of candidate transmit signal points;
• transforming the set of candidate transmit signal points into the output signal space to generate a set of candidate receive signal points;
• calculating the Euclidean distance between each of the candidate received signal points and the received signal point (y);
• and
• selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (y) to be the detected received signal point.

Computer readable media storing a computer program for installation and execution in a digital processor of a receiver of a Multiple-Input-Multiple-Output (MIMO) channel of a communication system in which there are N co-channel transmit antennas and M co-channel receive antennas where N and M are integers for detecting the signals transmitted over the MIMO channel, the computer program containing instructions when executed in the digital processor for carrying out the steps of:

• generating an N-dimensional array of possible transmit signal points in an N-dimensional input signal space and generating a corresponding M-dimensional array of possible receive signal points in an M-dimensional output signal space;
• receiving as an input a signal received from the M co-channel receive antennas and identifying a corresponding received signal point (y) in the output signal space;
• constructing a hypersphere (18) in the output signal space centred on the received signal point and having an initial radius (c1/2);
• transforming the hypersphere into the input signal space to construct a corresponding hyperellipsoid (20) in the input signal space;
• constructing an orthotope (22) in the input signal space which is the smallest orthotope which contains the hyperellipsoid (20) and which has sides which are parallel to the axes of the input signal space;
• assessing the array of possible transmit signal points in the orthotope and discarding those which are outside the orthotope to generate a set of candidate transmit signal points;
• transforming the candidate transmit points into the output signal space to generate a set of candidate receive signal points;
• calculating the Euclidean distance between each of the candidate received signal points and the received signal point (y);
• and
• selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (y) to be the detected received signal point.

A receiving apparatus of a single entity of a communications system which apparatus comprises a digital processor for detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of the communication system, which digital processor comprises:

• means for plotting a received signal point (y) in an M-dimensional output signal space corresponding to a set of signals received at the M co-channel receive antennas of the receiving apparatus;
• and
• means for mapping the received signal point to a corresponding noise corrupted transmit signal point (τ) in an N-dimensional input signal space where N and M are integers;
• means for constructing an orthotope in the input signal space centered on the noise corrupted transmit signal point, which orthotope has sides parallel to the axes of the input signal space;
• and
• means for selecting possible transmit signal points from an array of possible transmit signal points in the input signal space by selecting only those possible transmit signal points located inside the orthotope;
• and
• processing the limited candidate set of possible transmit signal points to determine a detected received signal point.

A receiving apparatus of a single entity of a communications system which apparatus comprises a digital processor for detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of the communication system which channel is sent by N co-channel transmit antennas, the receiving apparatus having M co-channel receive antennas for receiving the signals transmitted over the MIMO channel where N and M are integers, which digital processor comprises:

• means for receiving as an input a signal received from the M co-channel receive antennas and identifying a corresponding received signal point (y) in an M-dimensional output signal space;
• means for mapping the received signal point to a corresponding noise corrupted transmit signal point (τ) in an N-dimensional input signal space;
• means for constructing an orthotope (22) in the input signal space centered on the noise corrupted signal point and having sides parallel to the axes of the input signal space large enough to encompass at least one candidate transmit signal point of an array of possible transmit signal points in the input signal space;
• means for transforming all candidate transmit signal points located inside the orthotope into the output signal space to form a set of candidate received signal points;
• means for calculating the Euclidean distance between each of the candidate received signal points and the received signal point (y);
• and
• means for selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (y) to be the detected received signal point.

A receiving apparatus of a single entity of a communications system which apparatus comprises a digital processor for detecting signals transmitted over a Multiple-Input-Multiple-Output (MIMO) channel of the communication system which channel is sent by N co-channel transmit antennas where N and M are integers, the receiving apparatus having M co-channel receive antennas for receiving the signals transmitted over the MIMO channel, which digital processor comprises:

• means for generating an N-dimensional array of possible transmit signal points in an N-dimensional input signal space and generating a corresponding M-dimensional array of possible receive signal points in an M-dimensional output signal space;
• means for receiving as an input a signal received from the M co-channel receive antennas and identifying a corresponding received signal point (y) in the output signal space;
• means for constructing a hypersphere (18) in the output signal space centered on the received signal point and having an initial radius (c1/2);
• means for transforming the hypersphere into the input signal space to construct a corresponding hyperellipsoid (20) in the input signal space;
• means for constructing an orthotope (22) in the input signal space which is the smallest orthotope which contains the hyperellipsoid (20) and which has sides which are parallel to the axes of the input signal space;
• means for assessing the array of possible transmit signal points in the orthotope and discarding those which are outside the orthotope to generate a set of candidate transmit points;
• means for transforming the set of candidate transmit signal points into the output signal space to generate a set of candidate receive signal points;
• means for calculating the Euclidean distance between each of the set of candidate received signal points and the received signal point (y);
• and
• means for selecting the candidate received signal point having the smallest Euclidean distance from the received signal point (v) to be the detected received signal point.