Interactive video distribution systems – Video distribution system with upstream communication – Transmission network
Reexamination Certificate
1999-01-13
2004-03-09
Miller, John (Department: 2614)
Interactive video distribution systems
Video distribution system with upstream communication
Transmission network
C725S095000, C725S096000, C725S121000, C370S322000, C370S348000, C370S444000, C370S449000, C370S455000, C370S468000
Reexamination Certificate
active
06704932
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a multi-access communication system such as a bi-directional CATV network or passive optical star network where a center station dynamically allocates the band of an up-link to subscriber stations, and more particularly to a method for insuring the service quality on an uplink.
In the communication system including bi-directional CATV networks and passive optical star-networks, the downlink linked from a center station to subscriber stations generally is of a broadcast type while the uplink linked from a subscriber station to the center station is of a multi-access type using the time division multiplexing. The center station allocates an identifier when a subscriber station starts its operation. Next, when the subscriber station transmits up data to the center station, the center station first transmits up-band reservation permission information to a subscriber station group. Next, a subscriber station holding up data to be transmitted transmits reservation information formed of an identifier and a reserved up band to the center station. When pieces of reservation information simultaneously transmitted from plural subscriber stations collide with each other on the up line, the center station and the related subscriber stations solve the collision problem. Finally, the center station properly receives all pieces of reservation information. When holding data to be next transmitted at a data transmission time, the subscriber station adds the next reservation information to the up data and then transmits it to the center station. The center station creates up-band allocation information based on the reservation information and then informs the subscriber station of it. The subscriber station transmits the up data to the center station at an allocated up band. When the subscriber station does not require the service quality, the center station evenly allocates the up band to all subscriber stations every up transmission packet.
On the other hand, when the service quality which requires a band to be secured and the upper limit of a transmission delay amount as in the telephone and moving images communications is known, it is necessary to insure the service quality provided on the up-line every subscriber station. Conventionally, in order to insure the service quality on the up-multi-access line, the subscriber station informs the center station of a required service quality before transmitting up reservation information, whereas the center station periodically allocates the band for an up line in response to the service quality. When a plurality of up services are provided, the up-band allocation priority control is performed by specifying the service priority based on reservation permission information, reservation information or band allocation information and time-dividing the band of an uplink with the priority. As previous reports, there are “IEEE Communication Magazine”, written by James E. Dail et. al, pp. 104-112, March 1996 and “IEEE Transactions on Communications”, written by P. Papantori-Kazakos, Vol. 40, No. 3, pp. 541-555, March 1992.
Likewise the conventional multi-access communication system, the priority controlling method, which designates priority based on reservation permission information or band allocation information and then allocates an up band, requires to previously and fixedly determine various up-service-to-priority relationships between the center station and subscriber stations. Hence, the conventional system has disadvantage of being difficult to finely control the priority according to the up-service quality, thus lacking the flexibility.
Moreover, like the conventional multi-access communication system, there is the disadvantage in that when the center station insures the service quality by periodically allocating up-bands, the allocated up-band becomes wasteful. The reason is that when subscriber stations generate up data at irregular intervals, it often occurs that although the center station allocates the up-band of an uplink to a subscriber station, the subscriber station does not have up-data to be transmitted. Particularly, when the up-band data length is variable, it is difficult that the subscriber station accurately estimates an average up-data length to be reported. The problem is that when an average up-data length longer than the actual data length is reported, the up-band is excessively allocated and that when an average up-data length shorter than the actual data length is reported, the up-band allocation is delayed.
SUMMARY OF THE INVENTION
The objective of the present invention is to solve the above-mentioned tasks.
Moreover, the objective of the invention is to provide a multi-access communication system such as bi-directional CATV networks, passive optical star networks, or the like, where a center station dynamically allocates uplink bands to subscriber stations, can flexibly and effectively allocate uplink bands for the up-service quality assurance.
Furthermore, the objective of the present invention is to provide a method of flexibly and effectively allocating uplink bands in a multi-access communication system to insure the up-service assurance.
The objective of the first aspect of the present invention is achieved by a multi-access communication system comprising a center station including means for allocating identifiers to subscriber stations; means for transmitting reservation transmission permission information to the subscriber stations, means for receiving reservation information from a subscriber station; means for allocating an up band based on the reservation information from the subscriber station; means for receiving service quality request information from the subscriber station; means for allocating an identifier to a subscriber station according to a requested service quality; and means for allocating bands from data with higher priority according to the service quality designated by the identifier of reservation information from a subscriber station.
Moreover, the subscriber station includes means for receiving an identifier allocated from a center station; means for receiving reservation transmission permission information from the center station; means for transmitting reservation information to the center station at an up band designated with the reservation transmission permission information; means for receiving up-band allocation information from the center station; means for transmitting up-data to the center station at an up-band designated with the up-band allocation information; means for transmitting service quality request information to the center station; and means for adding an identifier according to the service type of the up-data to be transmitted and adding an identifier according to the service type of the up-data to be transmitted to reservation information to be transmitted to the center station.
In the multi-access communication system of the second aspect of the invention, the center station has means for periodically transmitting reservation transmission permission information to which the identifier of the service is added, to the subscriber station using a high priority service.
In the multi-access communication system of the third aspect of the invention, the center station includes means for allocating a unique identifier to each of the subscriber stations each using a high priority service and allocating a common identifier to a group of a subscriber station group using the high priority service, and means for periodically transmitting reservation transmission permission information to which a common identifier is added, to the subscriber station group using a high priority service, and the subscriber station includes means for transmitting reservation information for an up-band to the center station in response to the reservation transmission permission information if there is up-data to be transmitted corresponding to service designated by the identifier.
In the multi-access communication system of the fourth aspect of
Matsunaga Yasuhiko
Momona Morihisa
Dickstein Shapiro Morin & Oshinsky LLP.
Hoye Michael W.
Miller John
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