| 摘要 |
Near on-demand delivery of digital signals is accomplished by first dividing the signals into sequences of N numbered fragments, where the length of each fragment is equal to the broadcast time interval. The fragments are broadcast so that the first fragment is repeated every broadcast time interval, the second fragment is repeated every two time intervals, and so forth until the Nth fragment is repeated at least every Nth time interval. A fractal channel packing algorithm is preferably used to sequence the fragments over a plurality of channels to reduce the variability in peak bandwidth caused by fragmentation. The fragments are locally downloaded and stored during successive time intervals in response to a subscriber's request so that the first fragment is available within one time interval from the request, and the higher numbered fragments are available within their respective periods. The fragments are read out in order and integrated to seamlessly deliver the requested signal. As a result, the average bandwidth of the delivered signal increases only logarithmically, instead of linearly, as the broadcast time interval is reduced. If a portion of the delivered signal is pre-stored at the receiving site, the required broadcast bandwidth has a finite bound, regardless of how much the broadcast time interval is reduced.
|
