SWITCHING DEVICE FOR A CABLE DISTRIBUTION RACK

Field of the Invention

The present invention generally relates to a telecommunications apparatus and network, and more particularly to an apparatus for efficient migration from legacy equipment and services to new equipment and services in a telecommunications network.

Background of the Invention Current telecommunications networks can supply a variety of telecommunications services to customers via a Multi-Service Access Node (MSAN). The MSAN can provide services such as Plain Old Telephone Services (POTS), Digital Subscriber Lines (DSL), or Integrated Services Digital Network (ISDN) lines. These services are supplied via customer subscriber lines, which are typically copper cables connected to a customer Main Distribution Frame (MDF). The customer MDF is usually located in a service box at a location near to the customer's premises (often in a form of well known street cabinets). The MSAN is connected to a provider- MDF that is also located in the service box. To supply a particular telecommunications service to a customer, the service provider must make connections between the customer- MDF and the provider-MDF. A service engineer, who must visit the service box and make the connections, typically makes such connections manually. New connections are required to be made each time a new service is provided to a customer or an existing service is changed.

When new services or a new equipment is installed in the central office and the subscribers are to be switched to the new services offered by the new equipment the legacy equipment can be taken out of operation. The solutions known in the art require manual switching of connection from the MDF providing legacy services to the Multi-Service Access Node. This has several disadvantages. One of them is that the manual switching in the process of migration is very expensive, as it requires the

service engineer to be physically present at the location of the equipment. It is also time consuming and this is something that is very important from the point of view of the quality of service provided by the telecom operator. When subscriber pays for the service he expects that the service will be available when required. The solutions known in the art require long "down time" and in the case of additional unit added (e.g. in the form of a board or blade connected in a rack) the whole service is interrupted.

The disadvantage of the solutions known in the art is that they are time consuming and therefore not cost effective, they do not allow for simple scalability (additional unit cannot be added without causing interruption).

Hence, an improved switching unit would be advantageous and in particular one that allows for the migration from one type of services to another one to be made with as little of manual work as possible and therefore with reduced the down-time of part of the telecommunications network.

Summary of the Invention

Accordingly, the invention seeks to preferably mitigate, alleviate or eliminate one or more of the disadvantages mentioned above singly or in any combination.

According to a first aspect of the present invention there is provided a switching unit for use in telecommunications and/or data networks as defined in claim 1.

The switching unit according to the first aspect of the present invention comprises a distribution matrix and a first group of switching elements, wherein each one of said switching elements is adapted to be connected on one side to a main cable and on the opposite side is adapted to establish a connection either to a Main Distribution Frame or to said distribution matrix. Said distribution matrix is adapted to

connect to a Multi-Service Access Node a line switched from the first group of switching elements.

According to a second aspect of the present invention there is provided a switching apparatus as defined in claim 13.

The switching apparatus according to the second aspect of the present invention comprises at least one switching unit having a distribution matrix and a first group of switching elements, wherein each one of said switching elements is adapted to be connected on one side to a main cable and on the opposite side is adapted to establish a connection either to a Main Distribution Frame or to said distribution matrix. Said distribution matrix is adapted to connect to a Multi-Service Access Node a line switched from the first group of switching elements. The apparatus also comprises a backplane, wherein at least part of the lines for connection between the distribution matrix and a Multi-Service Access Node go via said backplane.

According to a third aspect of the present invention there is provided a telecommunications and/or data network as defined in claim 15.

The telecommunications and/or data network according to the third aspect of the present invention includes a switching apparatus for providing telecommunication and/or data services, wherein said apparatus comprises at least one switching unit having a distribution matrix and a first group of switching elements. Each one of said switching elements is adapted to be connected on one side to a main cable and on the opposite side is adapted to establish a connection either to a Main Distribution Frame or to said distribution matrix. Said distribution matrix is adapted to connect to a MultiService Access Node a line switched from the first group of switching elements.

Further features of the present invention are as claimed in the dependent claims.

The telecommunications networks that operate today were originally created several decades ago and have been upgraded with the developments of the telecommunications technologies. However, due to enormous sizes and requirement of providing services with as little interruption as possible, when a new technology or service is rolled out in a network it is not a single operation. In many cases the old and new technologies co-exist. The operation of upgrading or installing new devices in a network in many cases requires making thousands of electrical connections. These types of operations take time and it would be very beneficial if the operation of adding new device to a network could be carried out in shortest possible time.

The present invention beneficially allows for a very simple and quick migration from legacy services to new services provided by the telecom operator with very limited disruption to the service. The solution is also easily scalable and adding new components does not cause interruption to the service provided. The scalability also allows for reducing control and processing performance by sharing resources. The aspect of resource sharing can be explained as follows. Assuming that there are X relays to control per module one need about 2xsqrt(X) control lines per module. For K modules, in solutions known in the art, the total effort is Kx2xsqrt(X) control lines. With the new solution according to the present invention with also X relays per blade one need in total only K + 2xsqrt(X) control lines. In the solution known in the art, it is necessary to have one control block as well as one power supply block per module. In the new solution there is a centralized control and power supply block, which is only slightly bigger than the one used for one module in the prior art as there is anyway only one matrix element at a time switching and consuming power. In the prior art solution the control and power block has a cost of P per module so KxP in total. In the new solution the total cost for the control and power block is (1 ... 1.5) xP.

Brief description of the drawings

The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a diagram illustrating a switching apparatus in one embodiment of the present invention;

FIG. 2 is a diagram illustrating arrangement of switching elements in a distribution matrix in accordance with one embodiment of the present invention;

FIG. 3 is a diagram illustrating a 1 x 2 switching element used in a device in accordance with one embodiment of the present invention; FIG. 4 is a diagram illustrating a 2 x 2 switching element used in a device in accordance with one embodiment of the present invention;

FIG. 5a - c are diagrams illustrating arrangement and operation of relay elements in an X-Y matrix in accordance with one embodiment of the present invention; FIG. 6 is a schematic illustration of the situation with a fully equipped four- slot shelf;

FIG. 7 is a schematic illustration of the situation with a sub-equipped four-slot shelf.

Description of embodiments of the invention

The term "main cable" herein below refers to a cable that goes from a central office to a street cabinet.

The term "blade" herein below refers to a switching unit 100, as this is the term often used in telecommunications industry.

The term "shelf herein below refers to a switching apparatus 200, as this is the term often used in telecommunications industry.

With reference to FIG. 1 a switching apparatus 200 and a switching unit 100, in one embodiment of the present invention, are presented. For the sake of clarity the drawing presents the embodiment of the invention in a very schematic way with elements and lines not essential for understanding the invention omitted.

The switching apparatus 200 is to be used in a central office and allows for easy switching between legacy services and newly introduced services. However it is also within contemplation of the present invention that said invention can be also successfully used in a co-location to the MSAN installation, either in central office or in street cabinets, where applicable due to limitations in signal reach.

The switching unit 100 comprises a distribution matrix 102 and a first group 104 of switching elements. Each one of said switching elements is connected on one side to a main cable 106 and on the opposite side is adapted to establish a connection either to a Main Distribution Frame 108 or to said distribution matrix 102. The switching elements of the first group 104, in a simplest embodiment, are 1 x 2 type switching elements 402 as illustrated in FIG. 3. The 1 x 2 switch 402 is very simple and has relay 404 for connecting port G either to port E or to port F. This allows for connection of a line from the main cable connected to port G either to the distribution matrix 102 or to the Main Distribution Frame (MDF) 108. The function of the MDF is provision of the legacy services to the network. Therefore lines that initially have been connected to the legacy services via the MDF 108 can be quickly switched over to the distribution matrix 102, which in turn is connected to a Multi-Service Access Node 110. Once the switching is made, the line connected to port G of the switching element 402 of the first group 104 is able to provide services from the Multi-Service Access Node 110. In a preferred embodiment the switching elements in the first group 104 are controlled independently per line. Also preferably the relays 404 used for the switching elements 404 of the first group 104 are latching ones, i.e. even in the case of power disruption for the whole unit 200 the service provisioning to the line stays in its current position.

Because one line consists of two twisted copper wires said one line requires two switching elements to correctly switch the line between ports, but for the sake of clarity only one switching element per line is presented in the figures.

In one embodiment the switching unit 100 comprises a test bus 114 for diverting the connected line through a testing equipment, which in a simplest embodiment comprises a second 116 and a third 118 group of 1 x 2 type switching elements 402. The switching elements in the second and third groups can be in "normal" position when the signal goes straight through the switching elements or in a "test " position when a in the line break is created and can be re-connected only via said test bus, which means that the line is operational when an additional circuit is connected to the appropriate ports of the test bus. The switching elements in the first 104, second 116, and third 118 groups are controlled independently per line and from each other. The switching elements of the second 116 and third 118 group, in a preferred embodiment, comprise non-latching relays, i.e. in case of a power disruption the relays return into their "normal" position. This prevents them from staying in the "test" position and disrupting the normal service for an "infinite" time.

When the switching unit is implemented in a telecommunications network, in a preferred embodiment, it forms a switching apparatus 200 that comprises at least one switching unit 100 and a backplane 202 and at least part 110 of the lines for connection between the distribution matrix and a Multi-Service Access Node go via said backplane 202. The switching unit 100 in this embodiment is in a form of a blade connected to the backplane 202 on a standard rack (e.g 19 inch rack, however rack sizes and other solutions are also possible).

In one embodiment the invention allows for scalable switching solutions to be deployed in a network. In such a solution a number N of outputs 120 and a number N of inputs 122 of the distribution matrix 102 are connected to other distribution

matrices of other switching units. When at least two switching units form the switching apparatus said lines 120, 122 connecting inputs and outputs of one distribution matrix with other distribution matrices go via said backplane 202.

With reference to FIG. 2 one implementation of a distribution matrix 102 is shown. In the illustrated example the distribution matrix has 64 inputs and 64 outputs. Switching within the matrix 102 is carried out by a plurality of 2 x 2 switching elements 502 arranged in banks and interconnected as illustrated in FIG. 2, wherein FIG. 5 provides enough information for one skilled in the art to implement the distribution matrix in practice.

The 2 x 2 switching elements 502 have their relays 504 and 506 operated together, which means that they can only establish passthrough and crossover connections.

In an alternative embodiment, for further flexibility, the distribution matrix 102 has at least one output port connected 120 to one input port of another distribution matrix (e.g. in FIG. 1 the distribution matrix 102 is connected by means of connection 120 to a backplane 202 and then to another distribution matrix (not shown)). The connection 122 coming from the backplane 202 to the input port of the distribution matrix represents connection that comes from another distribution matrix 102 of other switching unit. It is, however, within contemplation of the present invention that the number of connections 120, 122 between the distribution matrices can be higher than 1.

In the embodiment shown in FIG. 2 the arrangement of the 2x2 switching elements 502 allows switching of line connected to any one input to the following number of outputs (numbers given below are valid for unconfigured distribution matrix): each of the 64 inputs can reach 24 outputs,

the first 16 outputs (outputs 1 - 16) can be reached by all 64 inputs, the second 16 outputs (outputs 17 - 32) can be reached by 16 different inputs the remaining 32 outputs (outputs 33 - 64) can be reached by 8 different inputs.

It is, however, within contemplation of the present invention that distribution matrices with different internal structure can be used in alternative embodiments of the present invention.

In another alternative embodiment the switching unit 100 comprises a fourth group 602 of switching elements. The switching elements of the fourth group are connected to at least part of output ports of the distribution matrix 102 (as the distribution matrix 102 illustrated in FIG. X). Each one of said switching elements of the fourth group directs connection from an individual output it is connected to one of two possible directions. In this embodiment part of the output ports have connected 1x2 switching elements 402 in a way that port G of the 1x2 switching element is connected to one output port of the matrix 102. This modification of the distribution matrix results in the number of ports at the north side (output) of the distribution matrix 102 being greater than at the south (input) side. This provides a configurable connectivity either to the spider network in the backplane or to the MSAN ports. It is, however, within contemplation of the present invention that other solutions for directing connections from the output of the distribution matrix 102 to one from two or more destinations are possible without the need for undue experimentation, e.g. with use of half of a Benes network. Benefit of this embodiment is increased flexibility of configuration of connections and possibility to reduce the number of backplane variants and using them in sub-equipped shelves.

The so-called sub-equipped shelves are explained below by comparison with fully equipped shelves and with reference to FIG. 6 and FIG. 7. For the sake of clarity in the arrangement illustrated in FIG. 6 and FIG. 7 only the matrices 102 are shown.

With reference to FIG. 6 a fully equipped four-slot shelf is presented. Lets assume a shelf for four blades. For simplicity, in the drawing, the blade is represented only by the distribution matrix 102. The same applies to the description below, where for the sake of clarity only distribution matrices 102 are referred to, but the whole discussion is applicable to switching units 100. Each blade has M outputs towards backplane 202 for MSAN access and S outputs to each of the blades (including S outputs connected to S inputs of the same blade) so in total 4xS + M outputs per blade. In this embodiment, with four blades 100 on one shelf 200, the number of outputs 120 and a number of inputs 122 of the distribution matrix 102 that are connected to other distribution matrices 102 of other switching units 100 is N and N = 4xS. The whole shelf has 4xM outputs for MSAN access. The switching matrix 102 as illustrated in FIG. 2 (i.e. without the 1 x 2 switching elements connected to the outputs) installed has a width of 4xS+M outputs. M + S matrix ports are connected directly to the backplane, for the other 3xS matrix port there are 3xS 1 x 2 switching elements 404 to switch it either to the spider part (if the corresponding blade is equipped) or to the MSAN bus (else). As it is illustrated in FIG. 7, if only a single blade is in a shelf all 3xS 1 x 2 switching elements are switched towards the MSAN ports. For 2 blades 2xS elements are switched to the MSAN and S elements to the spider. For 3 blades it is just the other way round and for 4 blades all 3xS elements are switched towards the spider. With reference to FIG. 7 a sub-equipped four-slot shelf is presented. If full flexibility is not required, i.e. 1, 2, 3 or 4 blades, but instead, for example, a minimum of 50% blades is always equipped the number of 1 x 2 switching elements 402 can be reduced.

It is however within contemplation of the present invention that in one embodiment all of the output ports of the matrix 102 illustrated in FIG. 2 have connected 1 x 2 switching elements 402 in a way that port G of the 1 x 2 switching element is connected to one output port of the matrix 102.

In a preferred embodiment the switching elements 502 for switching connections within said distribution matrix 102 and switching elements 402, 502 of the first 104, second 116, third 118 and fourth 602 group are controlled from a remote location. With reference to FIG. 5 a - c it is shown how the relays of the switching elements 402, 502 are controlled. The control of said relays is optimised in a way that it is not necessary to control n relays independently by n drivers but in the worst case only by 2-times square root of n. In effect e.g. 100 relays don't need 100 controllers but, in the worst case, 2x10 = 20 drivers. It is the number of relay elements (irrelevant if they are 1 x 2 or 2 x 2) and the number of states they can have that determine the number of drivers required to control them. If all n 2 x 2 elements have only two states and if they are organized in one single control matrix according to FIG. 5 then it is necessary to have only sqrt(n) drivers. If a 2 x 2 element needs to have 3 - 4 states then it is necessary to drive the relays independently, which means the contribution to n is doubled. A 1 x 2 element can always have only two states. The fact that not all relays can be toggled together is not a problem because switching all relays at the same time could destroy the device due to very high power consumption. In consequence it would require power supply resources, which would be most of the time unused. The shown diodes 606, 608 and the coil 610 (for simplicity additional components have been left out) represent a logical gate (NOR function) in a way that there is only current through the coil 610 if both diodes 606, 608 have low potential. Operation and implementation in practice of the arrangement of FIG. 5 a - c is clear for one skilled in the art.

When more than one switching unit (or blade) 100 is comprised in one switching apparatus (or shelf) 200 the improvement of control of the whole apparatus is clearly visible. With one blade 100 requiring 2xsqrt(X) control lines per blade the switching apparatus 200 in accordance with the present invention comprising K blades requires only K + 2xsqrt(X), where X is the number of relays to control in one blade.

Installation of a device in accordance with one of the embodiments of the present invention in a working telecommunications network is easy and causes very limited interruption in service. The whole operation is limited to cutting the existing cable connecting the MDF in the central office and a street cabinet. The device is to be connected in on its main cable side to the lines from the cable going to the street cabined and on the MDF side to the lines going to said MDF. Remaining connections (i.e. to MSAN, power and control) are to be made before cutting the cable and therefore the connection of the device is limited to the very simple operation of cutting and connection, whereas the operation of configuration and switching from the legacy services to the new ones can be performed afterwards without disruption of the service. By using the solution of the present invention the down-time of the network is significantly shorter that in case of manual switching from one type of services to another one.

The functionality defined in the present invention may be implemented in a plurality of units or as part of other functional units. In consequence, the invention may be physically and functionally distributed between different units. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit. Singular references do not exclude a plurality. Thus references to "a", "an", "first", "second" etc do not preclude a plurality.