US 5,331,641 AGranted

Methods and apparatus for retiming and realignment of STS-1 signals into STS-3 type signal

AssigneeTranSwitch Corporation

InventorsBidyut Parruck, Robert W. Hamlin, Jr.

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Abstract

Apparatus and methods for retiming an STS-3 type signal are provided. The SPE of an incoming STS-3 type signal is demultiplexed into three STS-1 payloads and fed to three FIFOs, and a byte which is synchronous with the TOH is tracked through the three FIFOs to provide an indication of the FIFO depth. A frame count is also kept to track the number of frames since a last pointer movement. Stuffs or destuffs are generated based on the FIFO depth as well as based on the frame count, with a stuff or destuff generated as quickly as four frames from a previous pointer movement if the FIFO is close to full or close to empty, and less quickly (e.g., at thirty-two frames from a previous pointer movement) if the FIFO is only starting to empty or to fill. Where the STS-3 type signal is a STS-3C signal, the decision on whether to stuff or destuff is made with reference to all three depth measurement circuits as all the STS-1 payloads must be stuffed or destuffed together. Also, to realign the STS-1 components of the STS-3C signal, the J1 bytes of the signal are tracked through the FIFOs, and a logic circuit is provided having phase 3 of the outgoing STS-3 clock, and the three J1 byte control signals as inputs. The logic circuit inhibits a read of a J1 byte from any particular FIFO unless all FIFO's have a high J1 signal at phase 3 of the clock.

Claims29

Dependent claims

An apparatus for retiming an incoming STS-3 type signal having a first STS-3 rate into a second STS-3 type signal having a second STS-3 rate similar to but not exactly equalling said first STS-3 rate, comprising:

a) demultiplexer means for receiving a synchronous payload envelope data signal of said incoming STS-3 type signal, an associated synchronous clock of said incoming STS-3 type signal, and at least two control signals including a synchronous payload envelope control signal of said incoming STS-3 type signal, and a first byte control signal which is synchronous with one TOH byte of said incoming STS-3 type signal, said demultiplexer means for demultiplexing said incoming STS-3 type signal into three STS-1 type signals each accompanied by a byte control signal related to said first byte control signal which accompanies at least one byte of each of said three STS-1 type signals;
b) three FIFO means coupled to said demultiplexer means, each of said FIFO means for receiving one of said STS-1 type signals;
c) three frame counting means coupled to said demultiplexer means, each frame counting means for counting a number of STS-1 data frames since a last pointer movement relating to said STS-1 type signal;
d) three FIFO depth measurement means, one coupled to each of said FIFO means, each said FIFO depth measurement means receiving said related byte control signal and determining at least therefrom a number of bytes in said FIFO means;
e) logic means coupled to said three FIFO depth measurement means and to said three frame counting means, for generating for a particular one of said STS-1 type signals a destuff signal p-x frames after a determination by said logic means that the number of bytes in a particular one of said FIFO means which receives said particular one of said STS-1 type signals exceeds a first threshold value, where p is a integer greater than two, and x equals the number of frames since the last pointer movement or p-1 whichever is smaller, and for generating a destuff signal q-y frames after a determination by said logic means that the number of bytes in said particular one of said FIFO means exceeds a second threshold value, where q is a integer greater than one, and y equals the number of frames since the last pointer movement or q-1 whichever is smaller, wherein said first threshold is smaller than said second threshold, and q is smaller than p, and wherein said destuff signal triggers a pointer movement;
and
f) multiplexer means for reading data from each of said FIFO means according to said second STS-3 signal rate, and multiplexing said data from each of said FIFO means into an STS-3 payload.

4 more elements

A method for retiming an incoming STS-3 type signal having a first STS-3 rate into a second STS-3 type signal having a second STS-3 rate similar to but not exactly equalling said first STS-3 rate, comprising:

a) receiving a synchronous payload envelope data signal of said incoming STS-3 type signal, an associated synchronous clock of said incoming STS-3 type signal, and at least two control signals including a synchronous payload envelope control signal of said incoming STS-3 type signal, and a first byte control signal which is synchronous with one TOH byte of said incoming STS-3 type signal;
b) demultiplexing said incoming STS-3 type signal into three STS-1 payload signals each accompanied by a byte control signal related to said first byte control signal which accompanies at least one byte of each of said three STS-1 payload signals;
c) sending said three STS-1 payload signals and the related byte control signal to three FIFO means;
d) for each STS-1 payload counting frames of the incoming signal, and resetting the count upon a pointer movement for the particular STS-1 payload;
e) measuring the depth of each FIFO by tracking the related byte control signal;
f) based on the measured depth of the particular FIFO and the related frame count, generating for each STS-1 payload signal a destuff signal p-x frames after determining that a number of bytes in the particular FIFO means exceeds a first threshold value, where p is an integer greater than two and x equals the number of frames since the last pointer movement or p-1 whichever is smaller, and generating a destuff signal q-y frames after a determination that the number of bytes in the particular FIFO means exceeds a second threshold value, where q is an integer greater than one and y equals the number of frames since the last pointer movement or q-1 whichever is smaller, wherein said first threshold is smaller than said second threshold, and q is smaller than p, and wherein the destuff signal triggers a pointer movement;
and
g) multiplexing the STS-1 payload data from each of said FIFO means into said second STS-3 type signal at said second STS-3 signal rate.

5 more elements

An apparatus for retiming an incoming STS-3C type signal having a first STS-3 rate into a second STS-3C type signal having a second STS-3 rate similar to but not exactly equalling said first STS-3 rate, comprising:

a) demultiplexer means for receiving a synchronous payload envelope data signal of said incoming STS-3C type signal, an associated synchronous clock of said incoming STS-3C type signal, and at least two control signals including a synchronous payload envelope control signal of said incoming STS-3C type signal, and a first byte control signal which is synchronous with one TOH byte of said incoming STS-3C type signal, said demultiplexer means for demultiplexing said incoming STS-3C type signal into three STS-1 payload signals each accompanied by a byte control signal related to said first byte control signal which accompanies at least one byte of each of said three STS-1 payload signals;
b) data storage means coupled to said demultiplexer means, said data storage means for separately storing said STS-1 payload signals;
c) frame counting means coupled to said demultiplexer means, said frame counting means for counting a number STS-3C data frames since a last pointer movement relating to said second STS-3C type signal;
d) data storage measurement means coupled to said data storage means, said data storage measurement means for receiving said related byte control signal and determining at least therefrom a number of bytes for each of said STS-1 payload signals in said data storage means;
e) logic means coupled to said data storage means and said frame counting means, for generating a destuff signal p-x frames after a determination by said logic means that the number of bytes for each of said STS-1 payload signals in said data storage means exceeds a first threshold value, where p is an integer greater than two and x equals the number of frames since the last pointer movement or p-1 whichever is smaller, and for generating a destuff signal q-y frames after a determination by said logic means that the number of bytes in said data storage means for at least one of said STS-1 payload signals exceeds a second threshold value and that the number of bytes in said data storage means of the other STS-1 payload signals exceed a third threshold, where q is an integer greater than one and y equals the number of frames since the last pointer movement or q-1 whichever is smaller, wherein said first threshold is smaller than said second threshold, and said third threshold is smaller than said second threshold, and q is smaller than p, and wherein said destuff signal triggers a pointer movement for said second STS-3C type signal;
and
f) multiplexer means for reading said separately stored data in said data storage means at said STS-3 signal rate, and multiplexing said separately stored data into an STS-3C payload.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/848,384Filed 9 Mar 1992 · continuation in part
Priority: 27 Jul 1990
Granted: 19 Jul 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H04J 3/076
Using pulse stuffing for systems with different or fluctuating information rates or bit rates: bit and byte stuffing, e.g. SDH/PDH…
G06F 5/12
Having a sequence of storage locations each being individually accessible for both enqueue and dequeue operations, e.g. using random access…
H04J 3/0623
Synchronisation of signals having the same nominal but fluctuating bit rates, e.g. using buffers: synchronous multiplexing systems, e.g.…
H04J 3/1611
Fixed allocated frame structures: synchronous digital hierarchy [SDH] or SONET