| 摘要 |
<p>Within a desired service area, multiple transmitters (TX1-N) at separately located sites broadcast the same multi-channel, multi-program digital video signal. Broadcast waves from the transmitters (TX1-N) propagate throughout substantially overlapping portions of the service area. Obstructions in the service area, e.g. mountains, buildings, trees, etc., may block reception from one or more of the transmitters (TX1-N) at certain receiving sites. However, at most receiving sites, the receiving antenna (31) can receive a clear-line-of-sight transmission from one of the transmitters (TX1-N) via a directional antenna having a narrow field of view. Some receiving antennae will receive direct transmissions from at least one of the transmitters (TX1-N). To compensate for differences in propagation time to such receiving antennae, time delays of predetermined amounts are imposed between broadcasts by two or more of the respective transmitters (TX1-N). In the preferred implementation, the channels are 6MHz wide channels broadcast in the upper high-frequency microwave portion of the spectrum. Each such channel carries a mutiplexed digital data stream containing packets of information for a plurality of programs, e.g. TV programs.</p> |
