Patent ID: 8472399

Claim:
In a wireless communication network employing orthogonal frequency division multiplexing (OFDM) for uplink data communications between mobile terminals and a base station, a method of performing periodic ranging between a mobile terminal and said base station, the method comprising: defining a periodic ranging channel for use by said mobile terminal, said periodic ranging channel comprising a plurality N of blocks of sub-carrier frequencies of an OFDM frequency band, said N blocks of sub-carrier frequencies being non-contiguous within said OFDM frequency band, said channel further comprising a time slot, within a particular OFDM subframe, within which ranging transmissions shall be sent from said mobile terminal to said base station using said N blocks of sub-carrier frequencies, said time slot spanning one or more OFDM symbol periods but being less that a duration of said OFDM subframe; and periodically sending a ranging transmission over said periodic ranging channel from said mobile terminal to said base station, said sending comprising transmitting said ranging transmission within said time slot as a spread signal, said spread signal being spread across the sub-carrier frequencies of said N blocks, wherein a duration of said ranging transmission is less than the duration of said OFDM subframe, wherein the number of OFDM symbol periods comprising said time slot is configured based on an estimated or determined maximum ranging delay between said mobile terminal and said base station.