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.