Method for detecting and restoring underload and overload slip

A pointer, cell technology, applied in the field of detection and recovery of underload and overload slip, can solve the problem of not considering buffering and so on

Inactive Publication Date: 2002-10-09
ZARLINK SEMICON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0024] The slip detection routine is designed for SDT (Structured Data Transfer) operation and does not take into

Method used

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  • Method for detecting and restoring underload and overload slip
  • Method for detecting and restoring underload and overload slip
  • Method for detecting and restoring underload and overload slip

Examples

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Embodiment Construction

[0037] Detailed Description of Preferred Embodiments

[0038] Referring now to Figure 1, in "normal" or basic SDT (Structured Data Transfer) operation, cells arrive at the SDT receive SAR (RX_SAR) at an equal rate, and some cell delay variation occurs due to varying delays in the transmission circuit ( CDV). Since cells arrive at an "average" equal rate, they are usually written to the circular buffer at an average distance from the read pointer (the average distance is -CDV). Cells may arrive slower or faster than average due to cell delay variations, but if there are always multiple cells equal to the CDV in the buffer, slippage should not occur. Only in extreme cases (for example, the virtual circuit is severed, or the receiver and transmitter clocks deviate significantly) will slippage occur.

[0039] In Fig. 1, the operation of the buffer in SDT mode is shown, invalid bytes represent bytes that have been read, or in the case of startup, not written. In the normal state...

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Abstract

A method of managing buffers in a SAR (Segmentation and Reassembly) device in a cell-relay network in dynamic bandwidth circuit emulation mode involves reading out TDM data from a buffer at a location determined by a read pointer, and writing data from incoming cells commencing at a buffer location determined by a write pointer. The write pointer is incremented as data from incoming cells arc written into said buffers. On arrival of an incoming cell a determination is made as to the location of said write pointer. If the location of the write pointer lies between a first value equal to the location of the read pointer plus a predetermined maximum lead plus a predetermined DBCES buffer less the number of bytes per active channel and a second value equal to the location of the read pointer plus said predetermined DBCES buffering, an overrun condition is declared. If the location of said write pointer exceeds the location of the read pointer plus the predetermined maximum lead plus the predetermined DBCES buffer, an underrun condition is declared. This method takes into account additional buffering that is required to prevent underruns and overruns when operating in DBCES mode.

Description

field of invention [0001] The invention relates to the field of digital communication, in particular to a method for detecting and recovering underload and overload slippage when writing into a circular buffer in a dynamic bandwidth circuit emulation service. Background of the invention [0002] ATM (Asynchronous Transfer Mode) is a service that carries data in small fixed-size packets or cells over a packet-switched network. The cells are statistically multiplexed on fixed physical links between network nodes and virtual circuits are established on the network between the endpoints. ATM includes specifications, of which AAL1 (ATM Adaptation Layer 1) establishes a standard for carrying time-sensitive data such as voice or video images on virtual circuits between endpoints. This is called Circuit Emulation (CES) because it provides multiple voice channels that appear to the user like a time-division multiplexed channel. [0003] DBCES is a mode of dynamic bandwidth applicat...

Claims

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Application Information

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IPC IPC(8): H04L12/54H04L12/70
CPCH04L12/5602H04L2012/5649H04L2012/5652H04L2012/5654H04L2012/5681
Inventor 道恩·芬乔治·杰弗里
Owner ZARLINK SEMICON CORP
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