Sonet payload pointer processing and architecture

• US 5,717,693 A
• Filed: 01/03/1994
• Issued: 02/10/1998
• Est. Priority Date: 05/21/1992
• Status: Expired due to Term

• Current Assignee: Alcatel Network Systems India Limited (Nokia Corporation)
• Original Assignee: Alcatel Network Systems India Limited (Nokia Corporation)
• Inventors: Weeber, William B., Baydar, Ertugrul
• Primary Examiner(s): Kizou, Hassan
• Application Number:
  US08/176,309
• Time in Patent Office: 1,499 Days
• Field of Search: 370/84, 370/55, 370/100.1, 370/102, 370/105.1, 370/105.4, 370/110.1, 370/112, 370/105.3, 370/506, 370/509, 370/514, 370/516, 370/535, 370/545, 375/114, 375/118, 375/365, 375/362, 375/371, 375/372, 375/354, 359/115, 359/135
• US Class Current: 370/514
• CPC Class Codes: H04J 3/0623 Synchronous multiplexing systems, e.g. synchronous digital hierarchy/synchronous optical network (SDH/SONET), synchronisation with a pointer process

Abstract

A SONET network element receives incoming SONET signals with a receive line interface (2) which stores the incoming data in an elastic store at the recovered line rate while a local interface reads the stored data at the local network element rate, which may vary slightly from the recovered line rate, and which adjusts the received pointers according to the difference between the line and local rates or phase, allowing the payload data to "float" with respect to the boundaries of frames containing both payload data and overhead with pointers; an elastic store monitor performs the comparison between the receive payload rate and the local clock by comparing write addresses at the recovered line rate and read addresses at the local network element rate by a subtraction process which causes pointer adjustments to be made in response to the subtracted difference exceeding selected memory limits. A process for carrying out VT/TU and/or STS/STM pointer interpretation and generation is shown.

Claims

1. A synchronous optical network line interface (2), comprising:

a synchronous transport signal pointer interpreter (2e), responsive to an incoming signal (5) and to a line clock signal (6), for providing a first elastic store write address signal (2d), a virtual tributary number signal (2i) indicative of a virtual tributary count in a frame of the incoming signal, and a synchronous payload envelope synchronizing signal (2k);

a virtual tributary pointer interpreter (2j), responsive to the incoming signal (5) and responsive to said synchronous payload envelope synchronizing signal (2k), for providing a plurality of elastic store write address signals (2h) and a corresponding plurality of virtual tributary synchronizing signals (2mp);

an elastic store write address multiplexer (2g), responsive to said elastic store write address signals (2h) and to said virtual tributary number signal (2i), for providing a selected one (2f) of said elastic store write address signals (2h) as a second write address signal;

an elastic store write address multiplexer (2c), responsive to said first elastic store write address signal (2d) and to said second write address signal and responsive to a selected interface mode signal (2n) indicative of synchronous payload envelope or virtual tributary interface mode, for providing a multiplexed write address signal (9);

a virtual tributary synchronizing signal multiplexer (2mn), responsive to said virtual tributary synchronizing signals (2mp) and to said virtual tributary number signal (2i), for providing a selected virtual tributary synchronizing signal (2m); and

a synchronizing signal multiplexer (2b), responsive to said selected interface mode signal (2n), said selected virtual tributary synchronizing signal (2m) and said synchronous payload envelope synchronizing signal (2k), for providing a synchronizing signal (2a) to an elastic store (3) for synchronizing the multiplexed write address signal (9) with the incoming signal (5).

2. A synchronous optical network local interface (4) responsive to an input data signal (4a) from an elastic store (3), comprising:

a synchronous transport signal pointer generator (4b), responsive to a local clock signal (8) having a local clock rate, an output synchronizing signal (4k) from the elastic store (3), a mode signal (2n) indicative of a selected synchronous payload envelope or virtual tributary mode, an elastic store near full signal (3c) from a first elastic store monitor (3a), and an elastic store near empty signal (3b) from the first elastic store monitor, for providing a first elastic store read address signal (4e), a virtual tributary number signal (4j) indicative of a virtual tributary count in a frame of the input data signal (4a) and a payload envelope pointer signal (4m);

a virtual tributary pointer generator (4c), responsive to said output synchronizing signal (4k), a first plurality of virtual tributary near full signals (3f) from a second elastic store monitor (3d) and a corresponding first plurality of near empty signals (3e) from the second elastic store monitor (3d), for providing a first plurality of read address signals (4h) and a first plurality of pointer signals (4np);

a virtual tributary pointer multiplexer (4nq), responsive to said pointer signals (4np) and to said virtual tributary number signal (4j), for providing a selected virtual tributary pointer signal (4n);

a read address multiplexer (4g), responsive to said first plurality of read address signals (4h) and to said virtual tributary number signal (4j), for providing a second elastic store read address signal (4f);

a read address multiplexer (4d), responsive to said mode signal (2n), said first elastic store read address signal (4e) and said second elastic store read address signal (4f), for providing a multiplexed elastic store read address signal (10) for reading said input data signal (4a) from the elastic store (3); and

an output multiplexer (4p), responsive to said payload envelope pointer signal (4m), said selected virtual tributary pointer signal (4n) and said data output signal (4a) from the elastic store, for providing a multiplexed data output signal (7).

3. A receive device (1) for a synchronous optical network, comprising:

a receive line interface (2), responsive to a recovered line clock signal (6), and to a data input signal (5), for providing an elastic store write address signal (9), and for providing an elastic store synchronizing signal (2a);

an elastic store (3), responsive to said elastic store write address signal (9), said data input signal (5), said elastic store synchronization signal (2a) and an elastic store read address signal (10), for providing a data output signal (4a) having a local clock signal rate and for providing a pointer generator synchronizing signal (4k) having said local clock signal rate;

a first elastic store monitor (3a), responsive to a local clock signal (8), said elastic store write address signal (9) and said elastic store read address signal (10), for providing an elastic store near full signal (3c) and an elastic store near empty signal (3b); and

a receive local interface (4), responsive to said local clock signal, said pointer generator synchronizing signal (4k), said data output signal (4a), said elastic store near full signal (3c) and said elastic store near empty signal (3b), for providing a multiplexed data output signal (7) timed to said local clock signal; and

wherein said receive line interface (2) further comprises;

a synchronous transport signal pointer interpreter (2e), responsive to said data input signal (5) and to said recovered line clock signal (6), for providing a first elastic store write address signal (2d), a virtual tributary number signal (2i) indicative of a virtual tributary count in a frame of the data input signal (5) and a synchronous payload envelope synchronizing signal (2k);

a virtual tributary pointer interpreter (2j), responsive to said data input signal (5) and to said synchronous payload envelope synchronizing signal (2k), for providing a plurality of elastic store write address signals (2h) and a corresponding plurality of virtual tributary synchronizing signals (2mp);

a virtual tributary synchronizing signal multiplexer (2mn), responsive to said plurality of virtual tributary synchronizing signals (2mp) and to said virtual tributary number signal (2i), for providing a selected virtual tributary synchronizing signal (2m);

a write address multiplexer (2g), responsive to said plurality of elastic store write address signals (2h) and responsive to said virtual tributary number signal (2i), for providing a selected one (2f) of said plurality of elastic store write address signals (2h);

a write address multiplexer (2c), responsive to said first elastic store write address signal (2d) and to said selected one (2f) of said plurality of elastic store write address signals (2h) and responsive to a selected interface mode signal (2n) indicative of a selected synchronous payload envelope or virtual tributary interface mode, for providing said elastic store write address signal (9) to said elastic store (3); and

a synchronizing signal multiplexer (2b), responsive to said selected interface mode signal (2n), said selected virtual tributary synchronizing signal (2m) and said synchronous payload envelope synchronizing signal (2k), for providing said elastic store synchronizing signal (2a); and

wherein said receive local interface (4) further comprises;

a synchronous transport signal pointer generator (4b), responsive to said local clock signal (8), said pointer generator synchronizing signal (4k), said selected interface mode signal (2n), said elastic store near full signal (3c), and said elastic store near empty signal (3b), for providing a first elastic store read address signal (4e), a second virtual tributary number signal (4j) indicative of a virtual tributary count in a frame of the data input signal (5) and a payload envelope pointer signal (4m);

a virtual tributary pointer generator (4c), responsive to said pointer generator synchronizing signal (4k), a first plurality of virtual tributary near full signals (3f), and a first plurality of virtual tributary near empty signals (3e), for providing a first plurality of read address signals (4h) and a first plurality of pointer signals (4np);

a virtual tributary pointer multiplexer (4nq), responsive to said first plurality of pointer signals (4np) and to said second virtual tributary number signal (4j), for providing a selected virtual tributary pointer signal (4n);

a read address multiplexer (4g), responsive to said first plurality of read address signals (4h) and to said second virtual tributary number signal (4j), for providing a second elastic store read address signal (4f);

a read address multiplexer (4d), responsive to said selected interface mode signal (2n), said first elastic store read address signal (4e) and said second elastic store read address signal (4f), for providing said elastic store read address signal (10) for reading said data output signal (4a) from said elastic store (3); and

an output multiplexer (4p), responsive to said payload envelope pointer signal (4m), said selected virtual tributary pointer signal (4n) and said data output signal (4a), for providing said multiplexed data output signal (7); and

wherein said receive device (1) further comprises;

a second elastic store monitor (3d), responsive to said local clock signal (8), said plurality of elastic store write address signals (2h) and said first plurality of read address signals (4h), for providing said first plurality of virtual tributary near full signals (3f) and said first plurality of virtual tributary near empty signals (3e).