Method and apparatus for operating an indoor CDMA telecommunications system

A communication system transparently operable within the coverage area of a second communication system, the second communication system using a first frequency band for uplinking signals and a second frequency band for downlinking signals, the communication system comprising:

• a base station transceiver within the coverage area of the second communication system, wherein the second communication system remains unaffected by the operation of the communication system;
• a mobile station transceiver for communicating with the base station transceiver;
• a monitoring means associated with the base station for monitoring the first frequency band and the second frequency band to determine a plurality of candidate spreading codes orthogonal to those used in the second communication system of one of either the first frequency band or the second frequency band;
• and
• a means for selecting one spreading code of said plurality of candidate spreading codes for use in the communication between said base station transceiver and said mobile station transceiver.

A method of minimizing interference in a first communication system operable within the coverage area of a second communication system using a spreading code to identify a channel within a first frequency band for uplinking signals and a second frequency band for downlinking signals, said first communication system comprising a base station transceiver and a mobile station transceiver, the method comprising:

• (a) monitoring the first frequency band and the second frequency band by said base station transceiver to determine a plurality of candidate frequencies;
• (b) selecting one candidate frequency of said plurality of candidate frequencies for use in communication between said base station transceiver and said mobile station transceiver;
• (c) communicating information about said one candidate frequency from said base station transceiver to said mobile station transceiver;
• (d) communicating in a TDD format between said base station 16 transceiver and said mobile station transceiver using said one candidate frequency;
• and
• (e) repeating steps (a) through (d) during a periodic time frame to allow the second communication system to re-select the one candidate frequency in response to use of the selected one candidate frequency by the first communication system.

A method establishing a communication between a base station and a mobile station transceiver of a first communication system operating within a coverage area of a second communication system, the second communication system using a first frequency band for uplinking signals and a second frequency band for downlinking signals, the method comprising:

• monitoring the first frequency band and the second frequency band by said base station transceiver to determine a strongest interfering signal from the second communication system;
• identifying a first phase which the strongest interfering signal from the second communication system reaches said mobile station transceiver;
• identifying a second phase which a signal transmitted from said base station transceiver reaches said mobile station transceiver;
• calculating a phase error which indicates a difference between the first phase and the second phase;
• and
• adjusting a transmission timing of said base station transceiver to minimize any difference between said phase error and a predetermined optimal phase difference;
• and
• establishing communication between said base station transceiver and said mobile station transceiver by synchronizing the communication with the strongest interfering signal from the second communication system, wherein the base station transceiver utilizes the adjusted transmission timing.