A Method Performed by a Sphere Decoder Based Turbo Equalizer

A method performed by a sphere decoder based turbo equalizer, the method comprising:

• sorting, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sorting, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• selecting a QAM symbol with the minimum second distance property out of the QAM symbols of the second vector, wherein the selecting comprises labeling the selected QAM symbol as protected;
• identifying the selected QAM symbol in the first vector sorted by first distance properties;
• pruning the first vector by eliminating all QAM symbols having a larger first distance property compared to the selected QAM symbol, wherein the pruning is restricted to QAM symbols not being labeled as protected;
• and
• thereafter, selecting the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeating the identifying and the pruning.

A sphere decoder based turbo equalizer, comprising:

• at least one processing circuit configured to:
• sort, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sort, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• select a QAM symbol with the minimum second distance property in the second vector and label the selected QAM symbol as protected;
• identify the selected QAM symbol in the first vector sorted by first distance properties;
• eliminate all QAM symbols in the first vector with a larger first distance property compared to the selected QAM symbol, restricted to QAM symbols not being labeled as protected;
• and
• thereafter, selecting the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeating the identifying and the eliminating.

A sphere decoder architecture, comprising:

• a sphere decoder based equalizer, the sphere decoder based equalizer comprising
• at least one processing circuit configured to:
• sort, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sort, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• select a QAM symbol with the minimum second distance property in the second vector and label the selected QAM symbol as protected;
• identify the selected QAM symbol in the first vector sorted by first distance properties;
• eliminate all QAM symbols in the first vector with a larger first distance property compared to the selected QAM symbol, restricted to QAM symbols not being labeled as protected;
• and
• thereafter, selecting the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeating the identifying and the eliminating.

A multiple input multiple output (MIMO) receiver, comprising:

• a sphere decoder architecture;
• wherein the sphere decoder architecture comprises a sphere decoder based equalizer, wherein the sphere decoder based equalizer comprises at least one processing circuit configured to:
• sort, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sort, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• select a QAM symbol with the minimum second distance property in the second vector and label the selected QAM symbol as protected;
• identify the selected QAM symbol in the first vector sorted by first distance properties;
• eliminate all QAM symbols in the first vector with a larger first distance property compared to the selected QAM symbol, restricted to QAM symbols not being labeled as protected;
• and
• thereafter, selecting the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeating the identifying and the eliminating.

A wireless communication device, comprising:

• a MIMO receiver;
• wherein the MIMO receiver comprises a sphere decoder architecture;
• wherein the sphere decoder architecture comprises a sphere decoder based equalizer, wherein the sphere decoder based equalizer comprises at least one processing circuit configured to:
• sort, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sort, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• select a QAM symbol with the minimum second distance property in the second vector and label the selected QAM symbol as protected;
• identify the selected QAM symbol in the first vector sorted by first distance properties;
• eliminate all QAM symbols in the first vector with a larger first distance property compared to the selected QAM symbol, restricted to QAM symbols not being labeled as protected;
• and
• thereafter, selecting the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeating the identifying and the eliminating.

A computer program product stored in a non-transitory computer readable medium for controlling a sphere decoder based turbo equalizer, the computer program product comprising software instructions which, when run on at least one processing circuit of a wireless communication device, causes the wireless communication device to:

• sort, in a first vector, Quadrature Amplitude Modulation (QAM) symbols on a particular tree level based on first distance properties;
• sort, in a second vector, QAM symbols on the particular tree level based on second distance properties;
• select a QAM symbol with the minimum second distance property out of the QAM symbols of the second vector, wherein the selecting comprises labeling the selected QAM symbol as protected;
• identify the selected QAM symbol in the first vector sorted by first distance properties;
• prune the first vector by eliminating all QAM symbols having a larger first distance property compared to the selected QAM symbol, wherein the pruning is restricted to QAM symbols not being labeled as protected;
• and
• thereafter, select the QAM symbol with the next minimum second distance property as the selected QAM symbol, and repeat the identifying and the pruning.