Method and apparatus for detecting forward and reverse link imbalance in digital cellular communication systems

A method of detecting link imbalances in a digital cellular communication system comprising a plurality of wireless units and a plurality of base stations, wherein transmissions from the base stations to the wireless units are made using forward radio communication links and wherein transmissions from the wireless units to the base stations are made using reverse radio communication links, and wherein each forward link includes control and forward traffic channels, and each reverse link includes control and reverse traffic channels, the method comprising the steps of:

• detecting a link failure in a first radio communication link between a wireless unit and a first base station during a call initiation, the step of detecting the link failure comprising the step of determining whether the failure in the first radio communication link comprises a reverse link failure or a forward link failure;
• determining whether the link failure is due to a link imbalance in the first radio communication link;
• instructing the wireless unit to switch to a second radio communication link if the link imbalance exists;
• determining if the forward link failure is due to a weak forward link, wherein the step of determining if the forward link failed due to a weak forward link includes the steps of:
• a) determining whether the control channel transmitted by the first base station was lost and proceeding to step (b) if the control channel was not lost, else proceeding to step (c);
• b) determining whether the wireless unit produced a traffic channel initialization (TCI) time out and instructing the wireless unit to return to normal operation if a TCI time out was not produced, else proceeding to step (c);
• c) measuring a forward channel signal strength received by the wireless unit from the first base station and proceeding to step (i) if the forward channel signal strength is sufficient, else proceeding to step (d) if the forward channel signal strength is insufficient;
• d) determining whether the wireless unit received a sufficiently strong second signal from a second base station and proceeding to step (g) if a sufficiently strong second signal was received, else proceeding to step (e);
• e) determining whether a received signal strength indicator received by the wireless unit is less than a predetermined threshold value;
• f) entering by the wireless unit an idle operational mode if received signal strength indicator is greater than the threshold value, else initiating by the wireless unit communication on a secondary system;
• g) determining whether the second base station is a neighbor base station to the wireless unit;
• h) exiting by the wireless unit the digital communication system if the second base station is not a neighbor to the wireless unit;
• and
• i) performing by the wireless unit an idle handoff and initiating communication with the second base station on a second radio communication link if the second base station is a neighbor to the wireless unit.

An apparatus for detecting link imbalances in a wireless communication system, comprising:

• a processor;
• and
• a storage medium coupled to the processor and containing instructions executable by said processor to:
• detect a link failure in a first radio communication link between a wireless unit and a first base station during a call initiation;
• determine whether the link failure is due to a link imbalance in the first radio communication link;
• and
• initiate communication using a second radio communication link if the link imbalance exists,
• wherein said processor determines whether the link failure is due to a link imbalance in the first radio communication link if a forward link failed by:
• determining whether the control channel transmitted by the first base station failed;
• and
• determining whether a traffic channel initialization time out occurred if the control channel transmitted by the first base station did not fail.

A method of detecting link imbalances in a digital cellular communication system comprising a plurality of wireless units and a plurality of base stations, wherein transmissions from the base stations to the wireless units are made using forward radio communication links and wherein transmissions from the wireless units to the base stations are made using reverse radio communication links, and wherein each forward link includes control and forward traffic channels, and each reverse link includes control and reverse traffic channels, the method comprising the steps of:

• detecting a link failure in a first radio communication link between a wireless unit and a first base station during a call initiation, the step of detecting the link failure comprising the step of determining whether the failure in the first radio communication link comprises a reverse link failure or a forward link failure;
• determining whether the link failure is due to a link imbalance in the first radio communication link, wherein said determining whether the link failure is due to a link imbalance in the first radio communication link if a forward link failed comprises:
• determining whether a control channel transmitted by the first base station failed;
• and
• determining whether a traffic channel initialization time out occurred if the control channel transmitted by the first base station did not fail;
• and
• instructing the wireless unit to switch to a second radio communication link if the link imbalance exists.