Abstract: A method for measuring channel delay measures the delay for a message to propagate from a prime site (100, 400) to a remote site (200, 500) via the channel (300, 600). The prime site includes a clock for providing a first value, T1, based on the current time at the prime site. The remote site includes a clock for providing a second value, T2, based on the current time at the remote site. Both clocks are synchronized with a common timing source, such as a GPS satellite timing signal. Therefore, T2 equals T1. In one embodiment, the prime site determines T1, and simultaneously sends a message to the remote site via the channel, the message including T1. Upon receiving the message, the remote site simultaneously determines T2. The remote site decodes the message to determine T1, and then determines the delay based on the difference between T2 and T1.

Abstract: An improved synchronization method and apparatus, according to the invention, is provided. According to the invention, in a simulcast system having a remote site receiving frames from a base site, each frame containing a predetermined number (k) of transmit sample periods, and the transmit sample clock and remote synchronization clock frequencies known (f.sub.tx and f.sub.pps respectively), the remote site synchronizes a frame as follows. First, it receives a frame from the base site. Second, it determines the sequence number n for the frame. Third, it determines the launch time the first frame was to be broadcast from the remote site. Fourth, it computes a realignment time based on [(n-1)*(k)+launch time for first frame] MOD (f.sub.tx f.sub.pps). Fifth, it transmits the first bit of the frame at the realignment time.

Abstract: An adaptive digital equalization filter is provided to remedy the differential time delay problem in a digital simulcast system. The digital simulcast system includes an adaptive digital equalization filter with N coefficients, and a fixed analog anti-alias filter. According to the invention, the adaptive digital equalization filter first measures the amount of delay contributed to the output signal by the fixed anti-alias filter. This is accomplished by exciting the anti-alias filter with a unit impulse, and measuring the resulting impulse response. The adaptive filter next determines the characteristics needed to compensate for the amount of measured delay contributed to the output signal by the fixed filter. This is accomplished by computing a new set of N coefficients using the Levinson-Durbin algorithm. The adaptive filter next adjusts its coefficients based on these determined characteristics. Further, the adaptive filter periodically determines when it is time to update the N coefficients.