Network control system for controlling relative errors between network nodes

A network control system for controlling a plurality of nodes respectively corresponding to, and provided in, a plurality of radio zones, each of the plurality of nodes having a plurality of corresponding adjacent nodes without other nodes positioned between the respective node and each of the plurality of corresponding adjacent nodes, each node having a corresponding base station, where a mobil station travels among the plurality of radio zones and communicates with the base station of a respective node when travelling in a radio zone corresponding to the respective node, each base station transmitting a transmission signal for the corresponding node to the plurality of corresponding adjacent nodes and receiving transmission signals transmitted from the base stations of the plurality of corresponding adjacent nodes, each of the base stations comprising:

• a reception automatic frequency control unit receiving the transmission signal of each of the base stations respectfully corresponding to the plurality of corresponding adjacent nodes, performing an automatic frequency control operation for each received transmission signal in accordance with the transmission frequency of the respective received transmission signal, and producing a corresponding frequency signal for each received transmission signal;
• a frequency error detection unit receiving the frequency signals produced by the reception automatic frequency control unit, detecting a frequency error between the frequency of each frequency signal produced by the reception automatic frequency control unit and a frequency obtained by adding a nominal frequency gap between base stations to the transmission frequency of the transmission signal of the node corresponding to the frequency error detection unit, and producing corresponding output signals;
• an averaging unit receiving the output signals of the frequency error detection unit, spatially filtering the frequency errors, and providing an output signal indicating a spatial mean value corresponding to the spatially filtered frequency errors;
• and
• a transmission frequency control unit receiving the output signal of the averaging unit and controlling the transmission frequency of the node corresponding to the transmission frequency control unit in accordance with the spatial mean value, to substantially eliminate the frequency errors.