Synchronization of ATM-based network system using variable bit rate ATM adaptation layer protocols
AssigneeNokia Telecommunications Oy
InventorTopi Johannes Kaaresoja
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Abstract
A system and method for synchronizing variable bit rate traffic between a source and destination in an Asynchronous Transfer Mode (ATM) network. The method includes designating a variable bit rate ATM Adaptation Layer (AAL) protocol to define ATM cell traffic flow from the source to the destination. A synchronous residual timestamp (SRTS) value indicative of the timing of a source clocking function is encoded and transmitted with an ATM cell using a variable bit rate AAL, such as AAL2 or AAL5. The ATM cells and associated SRTS values are received and decoded at the destination ATM interface, and the destination clock is synchronized with the source clock by modifying the destination clock according to the SRTS values.
Claims15
A method for synchronizing variable bit rate traffic between a source and destination in an Asynchronous Transfer Mode (ATM) network, comprising:
- designating a variable bit rate ATM Adaptation Layer (AAL) protocol, AAL5, to define ATM cell traffic flow from the source to the destination;
- encoding a synchronous residual timestamp (SRTS) value indicative of the timing of a source clocking function using one or more sequence numbers and one or more portions of the SRTS value;
- creating an SRTS field in an AAL5 Common Part Convergence Sublayer Protocol Data Unit (CPCS-PDU) trailer to occupy at least a portion of the SRTS value;
- creating a sequence number (SN) field in the AAL5 CPCS-PDU trailer to occupy a sequence number corresponding to a sequence and completion status of segmented portions of the SRTS value;
- transmitting the CPCS-PDU, including the sequence number and the segmented portion of the SRTS value from the CPCS-PDU trailer, using the AAL5 protocol;
- receiving the ATM cells and corresponding SRTS values at the destination;
- decoding the SRTS value for use at the destination;
- and
- synchronizing a destination clocking function with the source clocking function by modifying the destination clocking function according to the SRTS values.
A cellular communications system for communicating voice information over a core network using Asynchronous Transfer Mode (ATM) technology and variable bit rates (VBR), the system comprising:
- at least one a base transceiver station (BTS) to communicate with at least one mobile station (MS), the BTS having a first ATM interface coupled to the core network;
- an Inter Working Function (IWF) having a second ATM interface coupled to the core network to communicate with the first ATM interface in the BTS via the core network;
- processing means for synchronizing variable bit rate traffic between the first and second ATM interfaces, the synchronization means comprising:
- means for designating a variable bit rate ATM Adaptation Layer (AAL) protocol to define ATM cell traffic flow between the first and second ATM interfaces;
- means for encoding a synchronous residual timestamp (SRTS) value indicative of the timing of a source clocking function using one or more sequence numbers and one or more portions of the SRTS value;
- means for creating an SRTS field in an AAL5 Common Part Convergence Sublayer Protocol Data Unit (CPCS-PDU) trailer to occupy at least a portion of the SRTS value;
- means for creating a sequence number (SN) field in the AAL5 CPCS-PDU trailer to occupy a sequence number corresponding to a sequence and completion status of segmented portions of the SRTS value;
- means for transmitting the CPCS-PDU, including the sequence number and the segmented portion of the SRTS value from the CPCS-PDU trailer, using the AAL5 protocol;
- means for receiving the ATM cells and corresponding SRTS values at a destination ATM interface;
- and
- means for synchronizing a destination clocking function with the source clocking function by modifying the destination clocking function according to the SRTS values.
Dependencies are inferred from the claim text.