Method and apparatus for performing soft handoff between cells of large differing radii

A method of coordinating a handoff of a mobile station between a serving transmitter and a target transmitter in respective cells having large differing radii in a system in which transmitters each transmit a known identification code with a respective offset, in which mobile stations search for the identification code of a particular transmitter on,the basis of its particular offset, and in which a mobile station has a time reference which is based on a standard transmitter time reference plus a propagation delay between the serving transmitter and the mobile station, the method comprising:

• identifying to the mobile station a virtual offset which differs from the target transmitter's actual offset which compensates for a difference between the propagation delay between the mobile station and the serving transmitter and a propagation delay between the mobile station and target transmitter.

A method of compensating for a large difference in propagation delay between a first signal sent with a first propagation delay and a second signal sent with a second propagation delay comprising sending information which makes a receiver search for the second signal at a time which is substantially equal to the second signal shifted by the large difference in propagation delay, within plus or minus half a mobile search window size.

A control node for participating in the control of a plurality of transmitters, the control node comprising:

• for each of a plurality of transmitters a respective first memory field for storing a respective real code identifier and for at least one of the plurality of transmitters a respective second memory field for storing a respective virtual code identifier;
• wherein for a particular transmitter, the virtual code identifier and the real code identifier differ in a manner which permits a mobile receiver to find a pilot transmission from the particular transmitter notwithstanding a large difference in propagation delay between (the mobile receiver and the particular transmitter) and (the mobile receiver and a transmitter from which the mobile receiver derived a time reference).