WO2015006836A1

WO2015006836A1 - Network node and communications system utilising one or more of said nodes

Info

Publication number: WO2015006836A1
Application number: PCT/AU2014/050139
Authority: WO
Inventors: Christopher Snell
Original assignee: Mine Site Technologies Pty Ltd
Priority date: 2013-07-18
Filing date: 2014-07-18
Publication date: 2015-01-22

Abstract

The present invention concerns a network node comprising: first and second modems and a digital switch having one or more ports for attaching peripheral devices, the switch being interposed between the first and second modems, first and second cables being' respectively connectable to the first and second modems, wherein the network node is operable as a point-to-point link Further, the invention concerns a network of such nodes, connected by cables to form a series of point -to "point links. The invention allows a new, cable-based network topology of point-to-point links, which finds particular application in environments such as underground mines, subways and tunnels.

Description

Network node and commtmications system utilising one or more

of said nodes

Meld of the invention

[0001] The invention relates to a network node. More particularly, the present invention relates to a network node that can be utilised to provide network communications to environments such as underground mines, subways or tunnels. The invention also concerns a communication system that utilises one or more of the network nodes.

Background of the invention

[0002] In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date part of common general knowledge, or known to be relevant to an attempt to solve an problem with which this specification is concerned.

[0003] Communication systems for environments such as underground mines, subways or tunnels are often provided by leaky feeder cables. As known to those skilled in the art, leaky feeders involve the use of coaxial cables with discontinuous shieldin that allow reception and emission of radio waves. The cable functions as an antenna and carries radio frequency signals along its length. The signal is usually picked u by portable radio transceivers that are carried by mining personnel. Amplifiers are required at various locations along the length of the cable to compensate for signal loss due to the

discontinuous shielding. VHF and UH F frequencies are employed on leaky feeder radio systems that are deployed in underground minin environments. VHF systems utilise the 172/154 MHz frequency bands (for downstream and upstream communications respectively), whereas UHF systems utilise the 455/485 MHz frequency bands (for downstream and upstream

communications e sp ecti vely) .

[0004] More recently, attempts have been made to provide more

sophisticated communication systems (such as broadband data communication systems) to the underground mining environment. For example, WO

2012/099754 describes a communication system formed from an Ethernet, headend, Ethernet modem and a leaky feeder cable. The headend and modem transmit communication signals between each othe using a 60 MHz upstream channel and a 125 MHz downstream channel. The system includes a dual band, bi-directional amplifier that communicates Ethernet data over the leaky feeder cable as well as passing conventional radio communications.

[0005] The system described in WO 2012/099754 suffers from a number of disadvantages. Principally,, the signal emanating from the Ethernet modem is broadb nd and is difficult to amplify over long distances without introducing significant distortion. In addition, when several amplifiers are placed in.

series, system noise is accumulated which causes a correspondin decrease in the effective rate of data transmission.

[0006] Another disadvantage of the system described in WO 2012/099754 arises from the fact that damage to one section of the cable adversely affects communication across the entire system. This is a deficienc of leaky feeder systems generally.

Summary of the invention

[0007] Accordin to a first aspect of the present invention, there is provided a network node comp rising- first and second modems; and

a digital switch having one or more ports for attaching peripheral devices, the switch being interposed between the first and second modems, first and second cables being respectively connectable to the first and second modems, wherein the network node is operable as a point-to-point link.

[0008] The present invention takes an alternative approach to the provision of Ethernet services in underground mining or similar environments. Rather than attempting to implement Ethernet over the existing communication medium (for example a leaky feeder communication system), the invention creates a new, cable-based network topology of point-to-point links. This is in contrast to the approach of both leaky feeder and power line communication systems, which both involve the sharing of single backbone cabl amongst all of the network nodes.

[0009] The invention allows thousands of ports (inclu ding Ethernet ports and Wrfi access points) to be cost- effectively deployed in underground mines, including hard rock mines. Such mining environments can thus be provided with near ubiquitous network coverage. In addition, networks that incorporate nodes according to the invention are easy to deploy and troubleshoot due to the nodes combining to form a series of point-to-point links as opposed to a. single large shared medium. Such networks are also significantl more scalable than existing networks. The total cost of ownership i often low enough for sites to deploy blanket Ethernet and Wi-Fi coverage throughout the entire

underground tunnel environment. In turn, blanket network coverage enables services such as continuous tracking, voice communications, video

surveillance, remote automation, supervisory control and monitoring of environmental conditions and general purpose data services , to be provided to underground mining environments.

[0010] Preferably, the first and second modems are broadband modems. Typically, the broadband modems are power line modems, although other classes of broadband modems that operate over copper conductors (such as DSL modems and cable modems) can also be used. Power line modems are preferred due to the superior data rates that are achievable over the non- twisted-pair conductors that are typically installed i underground mining environments .

[0011] The digital switch may be of an suitable form that is cap ble of receiving and delivering digital packets to and from the modems. Ethernet switches are preferred due to their tight coupling with power line modems and their rich variety of inbuilt switching protocols.

[0012] Preferably, the network node includes an analogue device connected in parallel with the first and second modems, the device connecting the first and second cables and being operable to process signals received on one or other cable. Providing an analogue device allows a duel digitaVanalogue network to be constructed using two o more network nodes according to this embodiment of the invention. Selected analogue signals received on one or other cable can be directed through the analogue device for processing and remain in analogue form, rather than being directed to one of the modems at which the signal is converted to digital form.

[0013] Typically, the analogue device is an amplifier that is operable to amplify signals received on one or other cable. According to some

embodiments, the amplifier is a bi-directional line amplifier.

[0014] Optionally, the network node includes first and second dividin components to which the first and second dividing components to which the first and second cables are respectively connectable, the dividing components being configured to divide the node into an analogue path containing the analogue device and a digital path containing the modems and digital switch. According to some embodiments, each dividing component is a diplexer.

[0015] According to other embodiments of the invention, the network node includes one or more additional modems operatively connected to the digital switch, one or more additional cables being respectively connectable to the additional modems.

[0016] According to a second aspect of the present invention, there is provided a -network comprising one of more nodes in accordance with the first aspect of the invention, the nodes being connected by cables, such that the network is a series of point-to-point links.

[0017] Optionally, the cables are leaky feeder cables.

[0018] Typically, the parallel analogue device/s in one or more of the nodes are configured to be selectivel switched i and out of the network, such that network redundancy can be provided to the analogue section of the network. [0019] The digital switch may utilises a suitable Ethernet Protocol, such as the Kapid Spanning Tree Protocol to provide the network redundancy to the analogue section of the network.

[0020] According' to some embodiments, the network includes one or more access nodes, each of which includes a modem and a digital switch.

[0021] According to a third aspect of the present invention, there is provided a network node comprising first and second modems connected back-to-back, first and second cables being respectively connectabie to the first and second modems, wherein the network node is operable as a point-to-point link.

[0022] According to a fourth aspect of the present invention, there is

provided a network comprising one or more nodes in accordance with the third aspect of the invention, the nodes being connected by leaky feeder cables, such that the network is a series of point-to-point links.

Brief description of the drawings

[0023] The invention will now be further explained and illustrated with reference to an example embodiment and to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a network node in accordance with an embodiment of the present invention;

Figure 2 is a schematic illustration of a first network implemented with the nodes described n Figure i;

Figure 3 is a schematic diagram of an access node in accordance with an embodiment of the present invention; and

Figure 4 is a schem tic illustration of an alternative network topology implemented with the nodes described in Figure 1.

Detailed description of the drawings

[0024] Turning to Figure 1, a network node 10 in accordance with an embodiment of the inventi on is illustrated. Node 10 includes a pai of ports (not shown) into which two separate cables 12 (downstream) and 14 (upstream) are attached. Cables 12 and 1 are typically two-conductor copper cables and carry both power and signals modulated thereon.

[0025] Each cable 12 and 14 attaches to a respective diplexer 16 and 18, that together divide node 10 into parallel upper and lower paths 20 and 22. Upper path 20 carries signals at frequencies in excess of 120 MHz, whereas lower path carries signals at frequencies below 120 MHz.

[0026] A leak feeder amplifier 24 is provided in upper path 20. Amplifier 24 amplifies radio frequenc signals received on either cable 12 or 14 up to an acceptable level for transmission to the next network node. Downstream signals are typically of a frequency between 145MHz to 160MHz, and are received on cable 12 , travel alon the upper path of amplifier 24 and exit network node 10 (after amplification) on cable 14. Correspondingly, upstream signals are received on cable 14, travel along the lower path of amplifie 24 and exit network node 10 (after amplification) on cable 12. Upstream signals are typically of a frequency bet ween 176 MHz to 185 MHz. Amplifier 24 includes suitable filters that are located on either side of each of the upper and lower amplifying components. Such leaky feeder VHP amplifiers are well known in the industry and will not be further described here.

[0027] Alternatively , a UHF leaky feeder amplifier can be used which operates in the same maimer as leaky feeder amplifier 24 but uses a 455 MHz frequency band for downstream communications and a 485 MHz frequency for upstream communications.

[0028] Lower path 22 includes a first power line communications (PLC) modem 26, an Ethernet switch 28 and a second PLC modem 80, connected in series. A series connection of a first and second modem and an interposed digital switch provides that the switch is on the digital side of each modem. In use (and as discussed below in greater detail), analogue signals arriving on either cable 12 o 14..are demodulated and converted to the form of digital frames at respective modems 26 and 30. The frames thus converted are then delivered to Ethernet switch 28 for re-conditioning and processing in

accordance with the applicable switching protocol running thereon. The processed and re-conditioned digital frames ar delivered from Ethernet switch 28 to one of the modems 26 or 30 for conversion to analogue form and modulation onto a respective cable 12 or 14 for delivery to an adjacent node.

[0029] Ethernet switch 28 includes conventional ports 29A-29D for establishing wired connections with Ethernet-capable devices, such as

embedded systems, laptop computers, IP phones, IP cameras and the like. Ethernet switch 28 also includes a management processor 36 with built in WiFi point for providing network services to WiFi-enabled devices, such as mobile phones, RFID scanners and similar. WiFi devices can also be used as a component in tracking and management services for underground

production vehicles.

[0030] Ethernet switch 28 is operable to filter and forward frames received from a other switch that is located in an adjacent node. As known to those skilled in the art, communication between Ethernet switches (as opposed to hubs) is on a point-to-point rather than a broadcast basis.

[0031] Delivery of Ethernet frames between devices 29A-29D is performed by Ethernet switch 28 utilising Etherne protocols that are know to those skilled in the ait.

[0032] Frame delivery to and from device 29A-29D to destinations and origins outside of node 10 are implemented in the following manner .

[0033] Inbound data-bearing signals arriving on cable 12 are directed by diplexer 16 to PLC modem 26, at which the signal is demodulated and the frames recovered. The recovered frames are transmitted via a suitable interface such as Reduced Media Independent Interface (RMII) to Ethernet switch 28 for processing. Similarly, inbound data-bearing signals arrivin on cable 14 are directed by diplexer 18 to PLC modem 30, at which the signal is demodulated and the frames recovered. Again, the recovered frames are forwarded to Ethernet switch 28 for processing.

[0034] Outbound data from devices 29A-29D or Ethernet switch 28 is transmitted from node 10 to an adjacent node using one of PLC modems 26 or 30. In either case, data frames ar delivered by Ethernet switch 28 to a PLC modem for modulation onto a suitable power carrier. Whether modem 26 or 30 is used is dependent on the adjacent node to which the data is to be transmitted. This is implemented in accordance with a suitable switching or routing algorithm, as will be understood by those skilled in the art.

[0035] It will be apparent that, each modulated data signal that exits node 10 is a newly-generated PLC signal. This PLC signal is effectively

reconditioned by node 10 to a digital signal before being converted to analogue and remodulated by one of PLC modems 26 or 30. Moreover, the point-to-point network topology ensures that the modulated signal need only travel to an adjacent node, rather than the entire length of a shared cable, such as a leaky feeder cable.

[0036] In addition, it will be realised that node 10 is a managed Ethernet switch, and as such, is able to implement suitable Ethernet protocols at the node level, such as Link Layer Discovery Protocol (fo automatically mapping the underground network)and Rapid Spanning Tree Protocol (RSTPXfor building redundant network links). Virtual LANs can also be created as necessary, whereby traffic can be inspected, prioritised and assigned to a VLAN based on designated traffic classes.

[0037] Furthermore, quality of service mechanisms provided as standard Ethernet utilities, can be used to prioritise different traffic classes (for example between voice, control systems, automation systems, data, and systems management).

[0038] Turning to Figure 2, an example network 40 that utilises network nodes in accordance with the invention is illustrated. Network 40 is

particularly suitable for installation in underground mining and other tunnel environments. As described above, leaky feeder communication systems are commonly deployed in such environments. Dedicated copper cablin (such as coaxial cable or DC power cable) for network 40 can be installed alongside an existing leaky feeder communication system , in which case the amplifier component 24 is not required inside each node. Alternatively, network 40 can utilise leaky feeder coaxial cables as the communication backbone. As described below, such an embodiment allows both Ethernet/WiFi services and leaky feeder radio communication to be provided simultaneously over the same infrastructure, allowing retrofitting of the nodes of the invention into an existing leaky feede network, such that each existing leaky feeder amplifier can be replaced by a node in accordance with the present invention.

[0039] Nodes 1 OA- 101 are placed at intervals of approximately 350 meters and serve as distribution nodes for the network 40. Network 40 is operably connected to a suitable core network 41 that backhauls data from underground network 40 to the surface. The backhaul network is typically fibre-based, with the inter-connection from network 40 to the core network, being by way of Gigabit Ethernet.

[0040] It is desirable that the length of cable between adj acent nodes lOA- 101 is no more than about 500 metres. Restricting the cable length in this way allows the PLC modems to be operated at close to their maximum data rate (currently around 500 MbpsX In turn, this enables a 500 Mbps (full duplex) data-rate network to span an entire underground tunnel system.

[0041] Access nodes 42 can be spliced into the backbone cable a needed at locations between access nodes where additional Ethernet o Wifi services are required. As illustrated in Figure 3, unlike distribution nodes 1 OA- 101, access nodes 42 include onl a single modem 43 and no VHF amplifier. Access node 42 also includes an Ethernet switch 45 with a single outlet and a management CPU 51 with integrated WiPi access port 53. Access node 42 taps power and data directly from the particular cable 55 to which it is connected.

[0042] Power inserters 44 place DC power on the backbone cables at suitable locations, depending on the number and location of Ethernet devices that are connected to the distribution and access nodes.

[0043] Data communication between adjacent nodes 10A-10I (and

ultimately to and from the backhaul network) operates by successive PLC modems forming a point-to-point pair of transceivers. For example PLC modem 30 from node 10A forms a transceiver pair with PLC modem 26 from node 10B. These transceiver pairs are formed at eac link in the network chain. For the sake of simplicity network 40 is illustrated as a linear topology. However, networks that are deployed in underground mining and tunnel environments generally include numerous branches, as the nodes and cables are installed throughout the tunnel system,

[0044] Being comp osed of a series of point-to-point links, r ather th an a single shared medium as per. the prior art, breakdown in one part of the network is localised and does not adversely effect othe parts of the network, A branched network can even continue to operate normally after a complete failure of one or more of the nodes or connecting- cables. Even if the network is completely linear, a variety of IP communications services (such as VoIP and machine automation) that do not need to communicate with a central server (due to the use of multicast) can continue to operate even if isolated from the backhaul network.

[0045] The leaky feeder communication system operates in parallel with the Ethernet network. This is achieved by the uppe paths 20 in each node 10A- 101 operatively joining the individual cables into a single cable. The parallel PLC modems on the lower path simultaneously terminate those same cables so as to provide a point-to-point Ethernet data link.

[0046] Upstream signals travel from leak feede VHF radio transceivers (not shown.) into the leaky feeder cable and are transmitted up to a suitable headend (not shown) at a frequency of -around 170 MHz. Downstream signals travel from the headend at a lower frequency (around 150 MHz) and exit the cable to be detected by the radio transceivers. Alternatively, UHF frequency bands (455MHz/4S5 MHz) can be used over the leaky feede system.

[0047] An alternative network topology 52 is illustrated in Figure 4,

Network 52 comprises nodes lOA-lOF joined by cables, but includes a number of redu dant loops. In particular, there are three redundant loops, namely-

Loop i: 10A, 10F, 10B Loop : lOA, lOF, 10E, lOD, IOC, 10B

Loop 3: lOF, IDE, 10D, IOC, 10B

[00 1] These redundant loops can provide a backup path in the event of failure of one of the network nodes or interposed cables. Redundant loops can be provided on network 52 due to each node in the network implementing the RSTP protocol. RSTP selectively disables network nodes to ensure a loop-free topology, while allowing the alternative path to be activated when required.

[0042] An advantage of the present invention is that it allows such redundancy in the Ethernet infrastructure to be used to make intelligent switching decisions in the leaky feeder communication systems. Such functionality is not possible with existing systems due to the shared nature of the leaky feeder cable. In contrast, network, nodes according to the invention, when ope ating in accordance with, the RSTP protocol, can selectively switch upper paths 20 in and out of the network, if and. as required under the control of the RSTP utility provided in Ethernet switch 28. This allows redundancy to be provided to the leaky feeder system. Alternative topologie can be designed to accommodate different levels of redundancy as required.

[0043] The word 'comprising' and forms of the word 'comprising' as used in this description and in the claims do not limit the invention claimed to exclude any variants or additions. Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.

Claims

1. A network node comprising-

.first and second modems; and

a digital switch havin one or more ports for attaching periphera devices, the switch being interposed between the first and second modems, first and second cables being respectively connectable to the first and second modems, wherein the network node is operable as a. point-to-point link.

2. A network node according to claim 1, wherein the first and second

modems are broadband modems.

3, A network node according to claim 2, wherein the broadband modems are power line modems.

4, A network node according to any preceding claim, wherein the digital switch is an Ethernet switch.

5. A network node according to an precedin claim, including an analogue device connected in parallel with the first and second modems, the device connecting said first and second cables and being operable to process signals received on one or other cable.

6, A network node according to claim 5, wherein the analogue device is an amplifier that is operable to amplify signals received on one or other cable,

7, A network node according to claim 6, wherein the amplifier is a bidirectional line amplifier,

8. A network node according to any one of claims 5 to 7, including first and second dividing components to which the first and second cables are respectively connectable, the dividing components being configured to divide the node into an analogue path containing the analogue device and a digital path containing the modems and digital switch.

9. A network node according to claim 8, wherein the dividing components are diplexers.

10. A network node according to claim 8 or claim. 9, wherein each dividing component selectively directs a signal received on one or other cable to either the analogue path or digi tal path on the basis of the received, signal's frequency,

11. network node according to any preceding claim, including one or more additional modems operatively connected to the digital switch, one o more additional cables being respectively connectable to the additional modems.

12. A network comprising one or more nodes in accordance with an

preceding claim, the nodes being connected by cables, such that the net work is a series of point-to-point links.

13. A network according to claim 12, wherein the cables are leaky feeder cables.

14. A network according to claim 12 or claim 13, when directly or indirectly dependent on claim 5. wherein the parallel analogue devices in one or more of the nodes are configured to be selectivel switched in and out of the network, such that network redundancy can be provided to the analogue section of the network.

15. A network according to claim 14, wherein the digital switch utilises an Ethernet Protocol to selectively switch the analogue devices in one or more of the nodes in and out of the network.

16. A network according to claim 15, wherein the Ethernet Protocol is the Rapid Spanning Tree Protocol.

17. A network according to any one of claims 8 to 16, including one or more access nodes, each node including a modem and a digital switch.

18. A network node comprising first and second modems connected back-to- back, first and second cables being respectively connectable to the first and second modems, wherein the network node is operable as a point-to- point link.

19. A network comprising one or more nodes in accordance with claim 18, the nodes being comiected by leaky feeder cables, such that the network is a series of point-to-point links.