Communication system, communication terminal, communication method, chip clock generation method, and orthogonal code generation method

A communication system, comprising

• a base station radio-transmitting to multiple communication terminals;
• and
• multiple communication terminals receiving signals transmitted from the base station and radio-transmitting to the base station,
• wherein the communication terminals each comprise:
• a time acquirer acquiring reference time information common to the multiple communication terminals;
• a clock generator generating a chip clock on the basis of the reference time information;
• a code generator generating orthogonal codes in time with the timing of the chip clock;
• a signal generator spreading transmission signals with the orthogonal codes to generate code division multiple access signals;
• a carrier wave generator generating a carrier wave;
• and
• a transmitter modulating the carrier wave generated by the carrier wave generator with the code division multiple access signals and transmitting the carrier wave to the base station, wherein
• the base station and multiple communication terminals transmit to each other via a satellite,
• the communication terminals each comprise a location acquirer acquiring location information of the communication terminal and satellite, and
• the code generator subtracts the delay time difference corresponding to the difference between the distance from the location of the communication terminal to the satellite and a reference distance from the reference time information to determine the times to generate the orthogonal codes.

A communication terminal that is one of multiple communication terminals receiving signals transmitted from a base station and radio-transmitting to the base station, comprising:

• a time acquirer acquiring reference time information common to the multiple communication terminals;
• a clock generator generating a chip clock on the basis of the reference time information;
• a code generator generating orthogonal codes in time with the timing of the chip clock;
• a signal generator spreading transmission signals with the orthogonal codes to generate code division multiple access signals;
• a carrier wave generator generating a carrier wave;
• and
• a transmitter modulating the carrier wave generated by the carrier wave generator with the code division multiple access signals and transmitting the carrier wave to the base station, wherein
• the clock generator generates a chip clock having a chip duration of which the allowable error is larger than the time accuracy of the reference time information.

A communication terminal that is one of multiple communication terminals receiving signals transmitted from a base station and radio-transmitting to the base station, comprising:

• a time acquirer acquiring reference time information common to the multiple communication terminals;
• a clock generator generating a chip clock on the basis of the time reference information;
• a code generator generating orthogonal codes in time with the timing of the chip clock;
• a signal generator spreading transmission signals with the orthogonal codes to generate code division multiple access signals;
• a carrier wave generator generating a carrier wave;
• and
• a transmitter modulating the carrier wave generated by the carrier wave generator with the code division multiple access signals and transmitting the carrier wave to the base station, wherein
• the communication terminal mutually communicates with the base station via a satellite,
• the communication terminal comprises a location acquirer acquiring location information of the communication terminal and satellite, and
• the code generator subtracts the delay time difference corresponding to the difference between the distance from the location of the communication terminal to the satellite and a reference distance from the reference time information to determine the times to generate the orthogonal codes.