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US 5,963,564 AGranted
Synchronizing the transmission of data via a two-way link
AssigneeTelefonaktiebolaget LM Ericsson
InventorsLars Goran Petersen, Mikael Kundel
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AssigneeTelefonaktiebolaget LM Ericsson
InventorsLars Goran Petersen, Mikael Kundel
Estimating the term…
Transmission is synchronized in a cell based switch of user cells which can include different numbers of data bits. The transmission is performed via a two-way link between functional entities which each includes a link control function containing functions for starting and controlling transmission of data on the link by sync cells which are exchanged between the link control functions. The exchange of sync cells is controlled by a sync state machine having three states. In a HUNT state, the link control function investigates a sync cell coming in from the link for establishing whether it agrees with a predetermined pattern for sync cells. In a PRESYNC state that starts after a sync cell contains the predetermined pattern has been found in the HUNT state, the link control function investigates a predetermined number thereafter incoming consecutive sync cells for establishing whether they contain the predetermined pattern. If this is not the case, the control process returns to the HUNT state. In a SYNC state that starts after the predetermined number of sync cells containing the predetermined pattern has been found in the PRESYNC state, transmission of data on the link is admitted while supervising data with respect to faults. If faults are found the control process is started again in the HUNT state.
A synchronizing system in a data transfer system for synchronizing transfer of data in the form of a bit stream between functional entities via a two-way link, each functional entity having means for applying arriving user data, which shall be transferred on the link, in user cells in which the number of data bits depends upon the magnitude of the respective user data, comprising:
A method for synchronizing, in a cell based switch, transmission of user cells, in which the number of data bits depends upon the magnitude of the respective user data, between switch ports and a switch core via a two-way link, comprising the steps of starting and supervising transmission of data on the link by means of sync cells which are exchanged between functional entities and each contains a synchronizing pattern, by means of which the sync cell can be identified, and control data which by the functional entities can be set to values admitting mutual checking that synchronism prevails, or a value that in a state of operation on the link is apprehended as implying loss of synchronism, forcing the functional entities to take measures for reinstating synchronism, wherein starting two-way transmission of data is preceded by the functional entities sending a predetermined number of consecutive sync cells to each other, the control data of which imply a request for return of a sync cell, the control data of which has a value confirming presence of synchronism.
A method for synchronizing, in a cell based switch, transmission of user cells, in which the number of data bits depends upon the magnitude of the respective user data, between switch ports and a switch core via a two-way link, comprising the steps of starting and supervising transmission of data on the link by means of sync cells which are exchanged between functional entities and each contains a synchronizing pattern, by means of which the sync cell can be identified, and control data which by the functional entities can be set to values admitting mutual checking that synchronism prevails, or a value that in a state of operation on the link is apprehended as implying loss of synchronism, forcing the functional entities to take measures for reinstating synchronism, wherein the mutual check of synchronism being present is performed by the functional entities regularly sending sync cells to each other, the control data of which implies a request for return of a sync cell, the control data of which has a value confirming presence of synchronism.
A method for synchronizing, in a cell based switch, transmission of user cells, in which the number of data bits depends upon the magnitude of the respective user data, between switch ports and a switch core via a two-way link, comprising the steps of starting and supervising transmission of data on the link by means of sync cells which are exchanged between functional entities and each contains a synchronizing pattern, by means of which the sync cell can be identified, and control data which by the functional entities can be set to values admitting mutual checking that synchronism prevails, or a value that in a state of operation on the link is apprehended as implying loss of synchronism, forcing the functional entities to take measures for reinstating synchronism, wherein the value forcing the functional entities to take measures for reinstating synchronism is included in a predetermined number of sync cells being sent by the functional entity that has detected loss of synchronism and means a request for return of a sync cell the control data of which has a value confirming presence of synchronism.
A method for synchronizing, in a cell based switch, transmission of user cells, in which the number of data bits depends upon the magnitude of the respective user data, between switch ports and a switch core via a two-way link, comprising the steps of the starting and supervising transmission of data on the link by means of sync cells which are exchanged between functional entities and each contains a synchronizing pattern, by means of which the sync cell can be identified, and control data which by the functional entities can be sent to values admitting mutual checking that synchronism prevails, or a value that in a state of operation on the link is apprehended as implying loss of synchronism, forcing the functional entities to take measures for reinstating synchronism, wherein the value forcing the functional entities to take measures for reinstating synchronism, is included in a predetermined number of sync cells being sent the functional entity having detected loss of synchronism and involves a request to the other functional entity to break transmission of data and send a sync cell the control data of which has a value confirming presence of a synchronism.
A method for synchronizing, in a cell based switch, transmission of user cells in which the number of data bits depends upon the magnitude of the respective user data between functional entities via a two-way link, comprising a link control function included in each functional entity containing functions for starting and controlling the transmission of data on the link by means of sync cells which are exchanged between the link control functions controlled by sync state machine that has three states, including
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Software-defined switches: hybrid ATM switches, e.g. ATM&STM, ATM&Frame Relay or ATM&IP
Special codes used as synchronising signal: detectors therefor, e.g. correlators, state machines
In which the allocation is indicated by an address the different channels being transmitted sequentially: aTM or packet multiplexing
Speed or phase control by synchronisation signals: arrangements for initial synchronisation
Term ended 13 Jun 2016 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
According to a first aspect the present invention relates to a method and a system for synchronizing, in a cell based switch, transmission of user cells which can include different numbers of data bits, between switch ports and switch core via a two-way link.
According to a second aspect the invention relates to a system for synchronizing in a data transfer system the transmission of data in the form of a bit stream between functional entities via a two-way link, each functional entity having means for applying data arriving from users and intended for transmission on the link, in user cells which can include different numbers of data bits depending upon the size of the respective user data.
In many data transmission systems different functional entities are connected together via a link. In particular this is the case in telecommunication systems. The link cost in many cases depends upon the number of physical interconnections. The more interconnections the higher the cost will be. It is therefore a usual practice to apply all information required on a single physical connection carrying a digital signal. This makes it necessary to reconstruct the logical structure at the receiving end of the link. For performing this implicit information must be transferred that points to the structure on different levels.
The invention will now be described more closely below with reference to the attached drawings on which
FIG. 1 schematically shows a telecommunication switch intended for both ATM and STM line connections, in which the invention can be used,
FIG. 2 more in detail and on a larger scale shows a part of the switch according to FIG. 1, including a two-way transmission link between a switch port and the switch core, for illustrating some main aspects of the inventive idea,
FIG. 1 shows a cell based telecommunication switch intended for both ATM (Asynchronous Transfer Mode) and STM (Synchronous Transfer Mode) line connections. The switch includes a plurality of switch ports 102.sub.1 -102.sub.n connected to a switch core 104 via each a two-way link 106.sub.1 -106.sub.n. The switch ports 102 are connected to e.g. a communication network that can contain e.g. incoming lines 107 and 108, processors etc. The lines 107 and 108 can carry ATM cells or STM time slots. The switch ports 102.sub.1 and 102.sub.2 are shown schematically as an example to be located on a line interface circuit card 110.sub.1 for STM line connection and a line interface circuit card 110.sub.2 for ATM line connection, respectively. The line interface circuit cards 110.sub.1 and 110.sub.2 are also shown schematically as containing each a respective line termination 112.sub.1 and 112.sub.2 which via a respective link 114.sub.1 and 114.sub.2 for user data is connected with the corresponding switch port 102.sub.1 and 102.sub.2, respectively. The switch port 102.sub.n is schematically shown as an example to be located on a server card 110.sub.n which includes a processor 116 connected to the switch port via the link 114.sub.n for user data.
FIG. 2 illustrates the two-way traffic between e.g. the switch port 102.sub.n and the switch core 104 via the link 106.sub.n more in detail. The switch port 102.sub.n applies arriving user data in user cells. The size of these user cells is chosen so as to suit the user data. For an ATM cell of 53 octets a user cell size of 56 octets can thus be chosen, i.e. 53 bytes plus cell size information plus checksums. STM time slots are applied in smaller cells. The user cell is then guided from a switch port to another one through the switch core. For a more detailed description of the technique of applying user data in user cells, and different circumstances in this context reference is made to Swedish patent application No. 9402051-8.
The switch port 102.sub.n contains a link control function 202 that receives user cells based upon user data arriving from the outside to be forwarded on the link 106.sub.n, and emits user cells arriving from the link, the data of which shall be sent out on e.g. the network, indicated by double arrow 204. The traffic between the switch port 102.sub.n and the switch core 104 proceeds between the link control function 202 and a link control function 206 in the switch core. The link control functions 202 and 206 manage the cell synchronization, as will be described more closely below.