Importance

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Abstract

In a two-way cable television (CATV) contention system peak upstream loading is accommodated by varying the length of the upstream transmission window during which a subscriber may randomly transmit for improved subscriber access to the CATV headend. Following an upstream transmission, the subscriber waits a predetermined period for a message receipt acknowledgment from the headend. Failure to receive this acknowledgment results in an upstream retransmission by the subscriber at a randomly selected time within a transmission window, the length of which is a function of the upstream message traffic load. The transmission window is initially short to permit rapid retransmissions upstream in order to avoid interfering noise bursts of short duration. The upstream transmission window is then increased in length to a maximum value to string out upstream transmissions during a peak access period for reducing upstream message collisions. Following upstream transmissions during the maximum transmission window, the window is then reduced in length to accommodate reduced upstream traffic following successful upstream communication by the majority of subscribers. This upstream transmission distribution arrangement improves subscriber headend access, namely system throughput, by increasing the transmission window during periods of peak access and shortening the window length following peak access periods in order to reduce the time required for a successful upstream transmission.

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