Transmitter, receiver, communication system, and communication method employing spread spectrum communication technique

A receiver employing a spread spectrum communication technique, comprising:

• a first reception system for despreading transmitted data with a first code;
• a second reception system for despreading transmitted data with a second code;
• reception format control means for determining whether data transmission has been performed in a first transmission mode or a second transmission mode;
• selection means for selecting and outputting either data output by said first reception system or data output by said second reception system, whichever has better communication quality, when data is transmitted in said first transmission mode, and;
• combining means for combining data output by said first reception system with data output by said second reception system when data is transmitted in said second transmission mode.

A communication system employing a spread spectrum communication technique, comprising:

• a transmitter including:
• transmission format control means for deciding whether to perform data transmission in a first transmission mode or in a second transmission mode;
• data division means for dividing data for transmission into a first portion and a second portion in the event that data is to be transmitted in said second transmission mode;
• a first transmission system which uses a first code for spreading said data for transmission in the event that the data is to be transmitted in said first transmission mode, or which uses said second code for spreading said first portion of the data in the event that the data is to be transmitted in said second transmission mode, and which transmits the data, and
• a second transmission system which uses a second code for spreading said data for transmission in the event that data is to be transmitted in said first transmission mode, or which uses the first code for spreading said second portion of the data in the event that the data is to be transmitted in said second transmission mode, and which transmits the data, and
• a receiver including:
• a first reception system for despreading transmitted data with a first code;
• a second reception system for despreading transmitted data with a second code;
• reception format control means for determining whether data transmission has been performed in a first transmission mode or a second transmission mode;
• selection means for selecting and outputting either data output by said first reception system or data output by said second reception system, whichever has better communication quality, when data is transmitted in said first transmission mode, and
• combining means for combining data output by said first reception system with data output by said second reception system when data is transmitted in said second transmission mode;
• wherein communication is performed in one of said first transmission mode and said second transmission mode.

A communication method employing a spread spectrum communication technique, comprising:

• a transmission mode decision step whereby the first transmission mode or the second transmission mode is selected for data transmission;
• a first spreading step whereby, in the event that data is to be transmitted in said first transmission mode, the same data is subjected separately to spreading with a first code and to spreading with a second code, and each of these coded forms is output;
• a division step whereby, in the event that data is to be transmitted in said second transmission mode, the data is divided into a first portion and a second portion;
• a second spreading step whereby the data of said first portion is spread using said first code and output, and the data of said second portion is spread using said second code and output;
• a despreading step whereby transmitted data is despread with said first code and with said second code;
• a transmission mode determination step whereby a determination is made as to whether data transmission has taken place in said first transmission mode or in said second transmission mode;
• a selection step whereby, in the event that it is determined that the data has been transmitted in said first transmission mode, either the data that has been despread with said first code in said despreading step or the data that has been despread with said second code is selected, depending upon which has the better communication quality, and;
• a combining step whereby, in the event that it is determined that the data has been transmitted in said second transmission mode, the data that has been despread with said first code in said despreading step is combined with the data that has been despread with said second code, and output.