Device for reassembling cell data device for circuit emulation service and method of ATM synchronization control
AssigneeNEC Corporation
InventorYoshio Shirasaki
Life of this patent
Estimating the term…
Abstract
A device and method are disclosed for correctly restoring a read clock when there are a plurality of STM data stream transmission sources. In a CES device of an ATM communication system, ATM cells from respective connections, which are to be delivered to the same outgoing line, are accumulated in a reassembly buffer memory and a PLO control unit aggregates the amount of ATM cells accumulated in the reassembly buffer memory for each connection. Subsequently, the PLO control unit calculates the frequency of a read clock based on the amount of accumulated ATM cells for each connection. A PLO restores the read clock which is applied to read data from the reassembly buffer memory for delivery to an STM network.
Claims13
An ATM cell reassembly device having an AAL1 terminator for receiving an ATM cell from each connection through an ATM network for termination, and a shared reassembly buffer memory for accumulating an AAL1 payload of said ATM cell received from said AAL1 terminator for absorbing a delay, said ATM cell reassembly device comprising:
- an accumulated amount aggregating unit for aggregating the amount of said AAL1 payload data accumulated in said reassembly buffer memory for each said connection;
- a target value managing unit for holding a target value for said accumulated amount for each said connection;
- a clock calculating unit for calculating a read clock frequency, said unit is operative for a first connection to receive said accumulated amount from said accumulated amount aggregating unit and said target value from said target value managing unit, respectively, and to start a correction of a read clock in a comparison of said target value with a count value for said accumulated amount when the count value for said accumulated amount reaches said target value, said clock calculating unit operative for second and subsequent connections to compare a total sum of count values for so far corrected connections and a current count value with a total sum of previous target values and a target value for a current connection to correct the read clock frequency;
- a clock restoring unit for restoring said read clock based on the frequency calculated by said clock calculating unit;
- and
- a data reading unit driven by said read clock restored by said clock restoring unit to read said AAL1 payload data from said reassembly buffer memory.
An ATM synchronization control method for receiving an ATM cell from each connection through an ATM network for termination, accumulating AAL1 payload data of said ATM cell in a shared reassembly buffer memory for absorbing a delay, and reading the accumulated AAL1 payload data in response to a read clock, said method comprising the steps of:
- previously holding a target value for the amount of said AAL1 payload data accumulated in said reassembly buffer memory for each said connection;
- aggregating the amount of said AAL1 payload data accumulated in said reassembly buffer memory for each said connection;
- calculating the frequency of said read clock based on said accumulated amount and said target value for a first connection;
- comparing a total sum of count values for the accumulated amounts up to the preceding connection and a current count value with a total sum of target values up to the preceding connection and a target value for a current connection to correct said read clock by said calculated frequency, and restoring said read clock for a second and subsequent connections;
- and
- reading said AAL1 payload data from said reassembly buffer memory in response to said restored read clock.
Dependencies are inferred from the claim text.