Communication system and method
AssigneeCambridge Broadband Networks Limited
InventorsJohn David Porter, Richard Mark Barden
Life of this patent
Estimating the term…
Abstract
In a communications system a transmitter is arranged to transmit asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled. In order to minimize the bandwidth required at lease some of the ATM cells include one or more switch command(s) (12) that indicate a change in the activation state of one or more STM channels (11-0 to 11-n). The switch commands (12) and STM channels (11) fill the ATM cell from opposite ends of the cell. Activate switch commands comprise two bytes, a high byte including a pointer (18) pointing to the start of a block of STM channels (11) and a low byte that includes a pointer (19) that points to the channel within a block of STM channels (11) to which the switch command applies.
Claims92
A communications system comprising
- a transmitter,
- a receiver, and
- a transmission medium between the transmitter and the receiver,
- the transmitter being arranged to transmit asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled;
- wherein at least some of the ATM cells include a switch command,
- the switch command indicating a change in an activation state of an STM channel, the switch command comprising two bytes,
- a first byte including a pointer pointing to the start of a block of STM channels, and
- a second byte including a pointer pointing to the channel within the block of STM channels to which the switch command applies.
A transmitter arranged to transmit asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled;
- wherein at least some of the ATM cells include a switch command,
- the switch command indicating a change in an activation state of an STM channel, the switch command including two bytes,
- a first byte including a pointer pointing to the start of a block of STM channels, and
- a second byte including a pointer pointing to the channel within the block of STM channels to which the switch command applies.
The receiver for receiving asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled;
- wherein at least some of the ATM cells include a switch command, the switch command indicating a change in an activation state of an STM channel, the switch command including two bytes,
- a first byte including a pointer pointing to the start of a block of STM channels, and
- a second byte including a pointer pointing to the channel within the block of STM channels to which the switch command applies;
- and
- wherein the receiver is arranged to detect from the switch command those STM channels that are active and to assemble the STM channels from successive ATM cells.
A communications method comprising the steps of:
- packing a synchronous transfer mode (STM) frame comprising a plurality of channels into asynchronous transfer mode (ATM) cells for transmission,
- inserting into each ATM cell in which an activation state of an STM channel changes, a switch command indicating whether a single STM channel is active or inactive, the switch command including two bytes, a first byte containing an offset value identifying the start of an STM frame in that ATM cell and a second byte identifying the channel within the STM frame to which the switch command corresponds,
- transmitting the ATM cells including switch commands, and
- receiving the ATM cells, using the switch commands to enable unpacking of the STM channels from ATM cells.
The method of transmitting asynchronous transfer mode (ATM) cells in which synchronous transfer mode (STM) channels are assembled comprising the step of transmitting the ATM cells including a switch command in at least some of the ATM cells, the switch command indicating a change in an activation state of an STM channel, the switch command including two bytes, a first byte including a pointer pointing to the start of a block of STM channels and a second byte including a pointer pointing to the channel within the block of STM channels to which the switch command applies.
The method of receiving for receiving synchronous transfer mode (STM) channels assembled in asynchronous transfer mode (ATM) cells at least some of which include one or more switch commands, each switch command indicating a change in an activation state of an STM channel and comprising two bytes, a first byte including a pointer pointing to the start of a block of STM channels and a second byte including a pointer pointing to the channel within the block of STM channels to which the switch command applies the method comprising the steps of:
- detecting from the switch command those STM channels that are active, and
- assembling the STM channels from successive ATM cells using the state of the STM channels derived from the switch commands.
Dependencies are inferred from the claim text.