Signal construction, detection and estimation techniques for use in uplink
timing synchronization and access control in an orthogonal frequency division multiplexed
(OFDM) wireless system or other type of wireless communication system. In accordance
with an illustrative embodiment of the invention, timing and access signals to
be transmitted in designated timing and access intervals are constructed from orthogonal
multitone signals. The multitone signals may be similar to multitone signals used
in OFDM data transmission, except that a cyclic prefix associated with reception
of the signals in a base station is extended to cover the timing errors of mobile
stations not yet synchronized. The invention also provides design techniques which
optimize the time resolvability and peak-to-average ratio of the multitone signals,
an efficient fast Fourier transform (FFT) based technique for maximum likelihood
timing estimation, and a robust linear filtering technique for averaging timing
estimates from different synchronizations.
