Method for determining reference phase in radio communication system which uses orthogonal M-ary modulation, and coherent detection method using the same

A demodulation method in a radio communication system including a plurality of base stations and terminals, said plurality of base stations and terminals being connected via spread spectrum communications, and which uses a code division multiple access system, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation, said demodulation method comprising the steps of:

• determining an in-phase component and a quadrature component by de-spreading a received signal;
• determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• carrying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and said in-phase component and quadrature component determined by said despreading;
• determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• and
• converting to a data signal a Hadamard matrix corresponding to the maximum value of said determined correlation value.

A demodulation method in a radio communication system including a plurality of base stations and terminals, said plurality of base stations and terminals being connected via spread spectrum communications, and which uses a code division multiple access system, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation, said demodulation method comprising the steps of:

• determining an in-phase component and a quadrature component by de-spreading a received signal in each of a plurality of receiving branches and fingers;
• determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• carrying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and the in-phase component and quadrature component determined via said despreading;
• determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• combining said determined correlation value with correlation values from other branches and fingers;
• and
• converting to a data signal a Hadamard matrix corresponding to the maximum value of the combined correlation values of said plurality of receiving branches and fingers.

A radio communication system, comprising a plurality of base stations and terminals, said plurality of base stations and terminals being connected via spread spectrum communications, and using a code division multiple access, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation, wherein each of said plurality of base stations includes:

• a circuit determining an in-phase component and a quadrature component by de-spreading a received signal sent from said terminal;
• a circuit determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• a circuit computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• a circuit selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• a circuit carrying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and said in-phase component and quadrature component determined via said de-spreading;
• a circuit determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• and
• a circuit converting to a data signal a Hadamard matrix corresponding to the maximum value of said determined correlation value.

A radio communication system comprising:

• a plurality of base stations and terminals, said plurality of base stations and terminals being connected via spread spectrum communications, and using a code division multiple access system, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation,
• each of said plurality of base stations including a plurality of receiving branches and fingers, and said plurality of receiving branches and fingers having:
• a circuit determining an in-phase component and a quadrature component by de-spreading a received signal sent from said terminal;
• a circuit determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• a circuit computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• a circuit selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• a circuit carriying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and the in-phase component and quadrature component determined via said de-spreading;
• a circuit determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• a circuit converting to a data signal a Hadamard matrix corresponding to the maximum value of said determined correlation value;
• a circuit combining said determined correlation value with correlation values from other branches and fingers;
• and
• a circuit converting to a data signal a Hadamard matrix corresponding to the maximum value of the synthesized correlation values of said plurality of receiving branches and fingers.

A base station utilizing a radio communication system that uses a code division multiple access system, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation, said base station comprising:

• means for determining an in-phase component and a quadrature component by de-spreading a spread spectrum signal sent from a terminal;
• means of determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• means for computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• means for selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• means for carrying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and the in-phase component and quadrature component determined by said de-spreading;
• means for determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• and
• means for converting to a data signal a Hadamard matrix corresponding to the maximum value of said determined correlation value.

A base station, which utilizes a radio communication system that uses a code division multiple access system, which performs orthogonal M-ary modulation on a data signal, followed by spread modulation, said base station, comprising:

• a plurality of receiving branches and fingers, each of said plurality of receiving branches and fingers including:
• means for determining an in-phase component and a quadrature component by de-spreading a received signal sent from a terminal;
• means for determining correlation values of said in-phase component and quadrature component, which correspond to respective Hadamard matrices resulting from either a fast Hadamard transform or an inverse Hadamard transform performed on said in-phase component and quadrature component;
• means for computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component;
• means for selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs the maximum value of said computed sum of the squares;
• means for carrying out coherent detection by complex multiplication of said selected fast Hadamard transform or inverse Hadamard transform output, and the in-phase component and quadrature component determined via said de-spreading;
• means for determining the correlation value by performing either a fast Hadamard transform or an inverse Hadamard transform on said coherent detection output;
• means for converting to a data signal a Hadamard matrix corresponding to the maximum value of said determined correlation value;
• means for combining said determined correlation value with correlation values from other branches and fingers;
• and
• means for converting to a data signal a Hadamard matrix corresponding to the maximum value of the combined correlation values of said plurality of receiving branches and fingers.