A cellular radio system in which a base station receiver can receive, on the
reverse
link, data from a mobile terminal in one of four control modes. In the first mode,
the mobile terminal sends an independent user pilot, not synchronized with the
base station, on the reverse link and the user data channel is synchronized to
this independent user pilot. In the second mode, the mobile terminal slaves its
user pilot to the pilot it receives from the base station and the user data channel
is synchronized with this slaved user pilot. This second mode allows the user terminal
to receive round trip delay information for purposes of geolocation and rapid reacquisition.
In the third mode, the mobile terminal slaves its user pilot to the incoming base
station pilot, as in the case of mode two, but the user data channel operates in
the orthogonal mode using the ranging information received from the base station.
The phase relationship between the user pilot channel and the user data channel
is calibrated. The user pilot carrier is also the carrier for the user data channel
and can be used as the carrier reference for detecting the user data channel. In
the fourth mode, the slaved pilot implementation of mode three is used for acquisition
but, after acquisition, the user pilot code is phase shifted to be synchronous
with the user data channel, thus also making it an orthogonal channel. In this
mode, the pilots no longer contribute interference to the user data channels, within
the cell, and can be transmitted at higher power levels.
