Broadband distribution system and method therefor

• US 5,920,800 A
• Filed: 03/18/1996
• Issued: 07/06/1999
• Est. Priority Date: 03/28/1995
• Status: Expired due to Fees

• Current Assignee: Alcatel NV (Nokia Corporation)
• Original Assignee: Alcatel NV (Nokia Corporation)
• Inventors: Schafer, Johann-Peter
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Lo, Linus H.
• Application Number:
  US08/617,297
• Time in Patent Office: 1,205 Days
• Field of Search: 348/12, 348/13, 348/7, 348/10, 348/6, 348/8, 455/3.1, 455/5.1, 455/4.2, 455/6.2, 455/6.3, 370/442
• US Class Current: 725/121
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

In a broadband distribution system (SYS) for distributing television signals (TVS) and video signals (VOD), the return channel provided for requesting video signals is divided among the subscribers (TN) of the broadband distribution system (SYS) in such a way, that each group of subscribers (TN) is assigned a part of the return channel using time-division multiplexing, and the individual subscribers (TN) of a group have equal access to the part of the return channel assigned to the respective group. Access by the individual subscribers (TN) is monitored by a control unit (CONTROL) in the center (ZE) of the broadband distribution system (SYS). To synchronize the signals transmitted by the subscribers (TN) over the return channel using time-division multiplexing, the center (ZE) has a synchronizer (SYNC) which compensates for phase differences produced by differences in transit time.

Claims

1. A broadband distribution system (SYS) for distributing television and video signals, comprising

a center (ZE),

a plurality of broadband network terminations (BONT), and

a plurality of subscribers (TN),

wherein the broadband network terminations (BONT) are connected to the center (ZE) wherein separate groups of subscribers (TN) are connected to each broadband network termination (BONT), wherein television and video signals are transmittable from the center (ZE) to the plurality of subscribers (TN) over downstream channels, and wherein request signals are transmittable from the plurality of subscribers (TN) to the center over a return channel,

characterized in that

the return channel is divisible among groups of subscribers (TN) using time-division multiplexing, that the individual subscribers (TN) of a respective group are permitted simultaneous access to a time slot of the return channel assigned to that respective group,

that simultaneous transmission of request signals by different subscribers (TN) of a group is detectable via a control unit, and

that said control unit inhibits forwarding of colliding simultaneous request signals.

2. A broadband distribution system (SYS) as claimed in claim 1, characterized in that the control unit (CONTROL) is located at the center (ZE).

3. A broadband distribution system (SYS) as claimed in claim 1, characterized in that the center (ZE) includes a synchronizer (SYNC), that each of the broadband network terminations (BONT) includes a delay device (VE), and that via the synchronizer (SYNC) and the delay devices (VE), the request signals transmitted by the broadband network terminations (BONT) are synchronized with the time-division multiplexed return channel.

4. A broadband distribution system (SYS) as claimed in claim 3, characterized in that delays provided by the delay device (VE) are so adjustable that the request signals transmitted to the center (ZE) are receivable at the center (ZE) in phase.

5. A broadband distribution system (SYS) as claimed in claim 1, characterized in that the part of the return channel assigned to the respective groups is variable in time duration for each respective group.

6. A broadband distribution system (SYS) as claimed in claim 3, characterized in that the delay device (VE) comprises a clock generator (CLK), a shift register (REG), a multiplexer (MUX), and a controller (UNIT).

7. A broadband distribution system (SYS) as claimed in claim 3, characterized in that the delay device (VE) comprises a clock generator (CLK), a counter (COUNT), two comparators (KOMP), and a controller (UNIT).

8. A broadband distribution system (SYS) as claimed in claim 1, characterized in that each broadband network termination (BONT) has a control unit (CONTROL).

9. A broadband distribution system (SYS) as claimed in claim 1, characterized in that if different subscribers (TN) transmit request signals simultaneously, the control unit (CONTROL) transmits a message indicative thereof to all subscribers (TN) connected to the respective broadband network termination (BONT).

10. A method of transmitting request signals from subscribers (TN) to a center (ZE) of a broadband distribution system (SYS) for transmitting television and video signals,

wherein the request signals are transmitted in a return channel of the broadband distribution system (SYS), and

wherein the television and video signals are transmitted in a downstream channel of the broadband distribution system (SYS),

characterized in that

the return channel is divided among groups of subscribers (TN) using time-division multiplexing, that

the individual subscribers (TN) of a respective group are permitted simultaneous access to a time slot of the return channel assigned to the respective group,

that simultaneous transmission of request signals by different subscribers (TN) of a group is detected via a control unit, and

that said control unit inhibits forwarding of colliding simultaneous request signals.

11. A center (ZE) of a broadband distribution system (SYS) for transmitting television and video signals over a downstream channel to a plurality of subscribers, and for receiving request signals over a return channel, characterized in that

the center (ZE) has at least one control unit (CONTROL),

that the return channel to said center is divided among groups of said subscribers by allocating a respective time slot to each group using time-division multiplexing, and

that each control unit (CONTROL) is able to receive request signals from a group of subscribers (TN) and to detect a transmission of request signals in the same time slot from different subscribers (TN) in a group and is able to inhibit forwarding of colliding request signals in a same time slot.

12. A center (ZE) as claimed in claim 11, characterized in that the center (ZE) additionally comprises a synchronizer (SYNC) for synchronizing said subscriber groups, said synchronizer having

a clock generator (CLK), and, connected in series,

a demodulator,

a phase comparator,

a controller unit, and

a modulator coupled to an output of the synchronizer,

said clock generator having an output connected to inputs of said phase comparator and of said modulator.