Network Convergence for Underground Mines.doc


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Network Convergence for Underground Mines.doc

  1. 1. Network Convergence for Underground Mines Authors Mr. Matthew R. Ward, P.Eng., Varis Ms. Anita Masuskapoe, Varis Abstract This paper aims to describe the reasons and methods to extend enterprise networks into underground mines. Currently mines use a number of communication networks for telephones, PLCs, two-way VHF radio and computer networking. Each system can have different wiring, protocols, converters and interfaces all which require expansion and maintenance. The convergence of voice, video and data using Ethernet and TCP/IP has the very real benefit of one “wire” for underground networks. Now that the majority of underground equipment can communicate using TCP/IP, network convergence can offer reduced network expansion and maintenance costs. Cost savings are good, but the truly exciting aspect of network convergence using Ethernet is the low-cost, high speed wireless networking now available. These wireless networks offer an opportunity to facilitate mining automation even on a small budget. How would mine operators change they way they operate if they could gather vehicle location and data in real time? What about controlling equipment remotely? The list of applications is long and includes traffic control, dispatching, real-time ore blending, tele-operation, automated production reporting, vehicle health monitoring, elimination of paper forms and immediate network access for surveyors and geologists. An ideal converged network for underground mining would be robust, inexpensive, easy to expand, enable fast and secure connections while keeping voice communication performance equivalent or better than what is now provided by VHF radio. Network Convergence – Ethernet What could explain the fact that modern computers rely on a communication network developed in 1972? Robert Metcalfe of Xerox was looking for a way to share printers, not define the way the world would communicate for the next fifty years. The reason Ethernet is alive and well today is that it has become a non- proprietary standard with readily available specifications, namely IEEE 802.3. TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of communications standards running over Ethernet and this combination is the basis for the Internet. Any computer connecting to the Internet is using TCP/IP, regardless if the connection is dial-up, DSL, cable, power line or wireless. Ethernet and TCP/IP are already used at mines for corporate networks. Some mines have introduced derivatives such as Modbus/TCP and EtherNet/IP into their PLC networks to take advantage of the low cost of Ethernet network cards, switches, routers and cabling. Anyone that paid $3000 to a PLC vendor for a network card knows why a $15 non- proprietary alternative is attractive. In addition to data communication, Ethernet and TCP/IP can be used to carry digitized voice and video signals. Digital voice communication using TCP/IP is referred to as VoIP (Voice over Internet Protocol), and digital video using TCP/IP is referred to as IP video. IP video equipment is significantly less expensive to deploy than dedicated coaxial or fiber networks and opens up new monitoring possibilities for operators. This is what is meant by convergence – a single network, Ethernet, which carries voice, video and data. Wireless Ethernet In 1999 a new standard, IEEE 802.11 was created to add wireless capability to Ethernet networks. Referred to as Wi-Fi hotspots or WLAN, these networks consist of one or more wireless Access Points (AP) hardwired to a Ethernet network. WLAN client devices include computers, PDA’s, bar code scanners, telephones, and cameras. WLAN networks are optimized for high speed/short range communications. The data rate (bandwidth) that can be attained depends on the version of 802.11, the antennas on each device, the distance between AP and the client and how many other wireless clients are requesting bandwidth.
  2. 2. Table 1 - WLAN Standards, Frequencies and Data Rate (Goldhammer, 2004) Standar Frequency Maximum Data Rate Useable Data Rate (3 m range) d 802.11a 5.8 GHz 54 Mbps 23 Mbps 802.11b 2.4 GHz 11 Mbps 6 Mbps 802.11g 2.4 GHz 54 Mbps 23 Mbps Radio propagation tests through 150 meters of underground drifts shows the 2.4 GHz 802.11b/g signal would have 30 dB less signal loss than the 5.8 GHz 802.11a signal (Emslie, 1975). Above 1 GHz increasing frequencies incur greater loss around corners, which eliminates 802.11a from further consideration in underground applications. The wireless data rate varies inversely with the distance between the AP and the client devices. Maximum data rates are attainable only within a small radius from the AP. As the client device moves further from the AP the data rate drops until the wireless connection is lost and data communication stops. Figure 1 - 802.11g Data Rate vs. Distance, PC Magazine, November 2004 25 20 Data Rate (Mbps) 15 10 5 0 0 20 40 50 Distance (m) Each wireless client connected to the same Access Point must share its bandwidth. There is documented degradation in speed for all clients when one client is far away from the AP (Duda, 2003). When this happens the AP lowers its bit rate in order to work with the weak signal of the distant client. The unintended consequence of this is that the data rate for all other clients slows to the speed of the distant client. As powerful as these new WLANs are, there are problems as described above. They can be avoided by limiting the number of clients in each hotspot, and avoiding distant communication where possible. Wireless Data Applications WLAN high speed data can be used in any number of applications underground. Vehicles can be fitted with WLAN modems and controllers to report load weighing and vehicle health (Dasys, 2003). Tele-operation becomes a practical option with real data rates over 5 Mbps enabling high quality IP video streaming. Wireless enabled hand held computers or PDAs can be used to eliminate paper forms within WLAN hotspots. Surveyors and geologists would be able to access the corporate network from hotspots located at the working face. Not all areas of the mine require high speed data access. Probable hotspot locations are garages, lunchrooms, refuge stations and production areas. WLAN hotspots could be easily moved to follow the mining activity. Production monitoring could be accomplished with APs at the draw and dump points.
  3. 3. Adding resource tracking capabilities would enable dispatching, traffic control and real time ore blending. Varis’ Smart Tag readers plug directly into the Ethernet network and can detect up to 50 tags traveling at 50 km/ hr. The mining industry has been talking about these applications for years, but Ethernet WLAN will make their implementation much easier. IP Video Conventional video transmission uses dedicated fiber optic or coaxial cable. Leaky feeder can also be used to transmit up to 8 channels of video. In the case of a dedicated network the expense is in the installation and maintenance of the cabling. With leaky feeder the expense is the modulator and where required, PTZ (Pan, Tilt, Zoom) controls. IP video eliminates the cabling, modulator and PTZ control costs. PoE (Power over Ethernet) can also be used to power IP cameras, which enables cameras to be located up to 100 meters from the nearest AC source. Sony PTZ IP video cameras cost approximately $1600, which is less than half of the conventional method’s cost. IP video quality is dependent on lighting, encoding/compression scheme and the image update rate. MPEG-4 encoding provides a high quality image while using less than 1 Mbps bandwidth. As the image size and update rate are reduced the required bandwidth drops significantly so that several dozen low and medium quality images can be transmitted. Extending Ethernet Underground Several methods can be used to extend Ethernet networks, however this paper will only consider three as they are the best suited for implementation in underground mines and tunnels: • Twisted pair cabling • Fiber optic cabling • Cable modem Inexpensive twisted pair cabling can support Ethernet up to 100 Mbps (Cat 5) or 1000 Mbps (Cat 6) however the maximum length of the cable is limited to 100 meters. To extend Ethernet over twisted pair beyond this distance requires an Ethernet switch to be installed and powered every 100 meters which increases the system cost, complexity and IT support requirements. Voice communication is attained with overlapping WLAN hotspots and wired or wireless VoIP phones.
  4. 4. Figure 2 – Ethernet over Twisted Pair Cabling on Mine Level Plan Fiber has almost unlimited bandwidth/speed and is immune to noise. Multi mode fiber can run 2000 meters between Ethernet switches and single mode fiber can run 5000 meters. Fiber optic cabling can be armored and composite fiber/copper cables can provide AC/DC power to network devices. Fiber optic Ethernet switches and routers are commercially available from several vendors. Drawbacks with fiber include cost and that its fragile nature requires trained installers. Voice communication is attained with overlapping WLAN hotspots and wired or wireless VoIP phones. Figure 3 – Ethernet over Fiber Optic Cabling on Mine Level Plan
  5. 5. Cable modems carry TCP/IP over cable TV networks to deliver high speed networking, Internet access and VoIP services. DOCSIS 2.0, the current standard for cable modems provides 54 Mbps downstream and 41 Mbps upstream. Mines with an existing Varis Smart Com leaky feeder network can be configured to carry Ethernet by adding the CMTS (Cable Modem Termination Service) controller, cable modems and frequency translators. The frequency translators are required as leaky feeder networks have a different bandsplit than cable TV networks. Cable modem and frequency translators are installed wherever a high speed wireless network is required. Voice communication is attained using two-way VHF radios and optionally, wired or wireless VoIP phones. Figure 4 – Overview of Ethernet over Leaky Feeder Figure 5 – Ethernet over Leaky Feeder System
  6. 6. DHCP Server HEAD END 4 upstream Router ports each capable of 16 way 54/41 Mbps SPL O O Rx RFOUT O O CMTS O O O O O I O O OO O O O OUT IN Frequency Translator 2 way Diplexer SPL H O C I L O PC Network connection Cable Modem, IN OUT through CAT5 cable Router, Frequency Leaky Feeder or wireless network Access Point card Translator CAT5 Cable Coaxial Cable To decide which method of extending Ethernet is best we also need to consider the quality of the voice communication that each method provides. Stationary Voice Communication POTS (Plain Old Telephone Service) telephones require a separate fiber and/or copper network. Over time these networks become maintenance intensive due to cable damage and corrosion. Telephone wiring repair is eliminated with VoIP, as proven by the 90+% maintenance cost decrease at Kidd Creek Mine (Nortel, 2003). VoIP systems can call sister sites that also have VoIP without incurring toll charges. It is quite possible to reduce the number of incoming lines leased from telephone service providers (Nortel, 2003) as the inter-site calls are no longer routed over leased lines. VoIP requires a sizable amount of technology investment but there is a potential to realize a reasonable payback. All three methods of Ethernet network extension will support desktop VoIP telephones. The network must be designed and maintained properly for VoIP to function properly. VoIP is a digital system which has specific network requirements for voice prioritization, bandwidth, packet loss, latency, jitter and end-to-end delay. These requirements must be addressed when designing the Ethernet network and the network must be monitored and maintained to ensure acceptable VoIP performance. Mobile Voice Communication Mobile voice communication is a very important service in underground mining. Mobile voice networks are used for dispatch, traffic control, emergency response, worker safety verification and general production communication. The quality, coverage and ease of use of mobile voice services are important considerations in determining how to extend Ethernet underground. Fiber optic and twisted pair networks provide mobile voice service using multiple WLAN Access Points and wireless VoIP handsets. Each Access Point installation requires trained technicians to determine its location, antenna configuration, range and speed. In order to roam between Access Points without dropping calls there needs to be overlapping WLAN coverage between Access Points. There is a maximum number of voice calls that any AP can support and will vary with several factors with the most critical being distance between AP and handset. Voice applications need traffic consistency as voice packets need to arrive relatively quickly together in
  7. 7. order to prevent jitter and drop-offs. Wireless VoIP will improve once the IEEE 802.11e Quality of Service standard is ratified and implemented so that wireless voice data will have priority over asynchronous functions like file transfer. Handset maker Spectralink SVP protocol currently performs this function in the absence of the 802.11e standard however only for 11 Mbps 802.11b Access Points. There are currently no wireless VoIP handset manufacturers delivering industrial-grade equipment. In contrast leaky feeder is an analog radio system specifically designed for mining and tunneling communication and is used at over 300 sites worldwide. It is a radiating cable network that provides continuous mobile voice coverage regardless of mine size, drift size, wall and support adsorption properties and mobile obstacles such as trucks. Leaky feeder can be installed by miners and its maintenance is facilitated by effective local and remote diagnostics. Either conventional or trunked VHF radios can be used and industrial-grade portable and vehicular (mobile) radios are available from several vendors. Accessories to facilitate radio use in industrial environments include cases, speaker microphones, headsets and throat microphones. Both VoIP and VHF radio can be equipped with PTT (push to talk) to effectively coordinate tasks. VoIP phones and VHF trunking radio with keypads provide private conversations between parties. VoIP phones have some features that radios do not including voice mail and SMS messaging. Conclusion The widespread adoption of Ethernet and TCP/IP is a powerful driver in “one wire” convergence. This one wire can be a new fiber optic or twisted pair cable or an existing leaky feeder network, or a combination of all three. Underground mine operators need to understand the cost saving and productivity benefits that can be attained with an underground converged network that supports high speed wireless networking. Hotspots can be strategically located to gather vehicle data and provide wireless networking at the face. Location systems coupled with vehicle data can be used to improve processes and reporting. The decision on how to provide mobile voice communications is critical to safety and productivity. Wireless VoIP systems are still in their infancy and require expert installation and tight control of the network traffic to provide equivalent voice capabilities to VHF radios and leaky feeder. The durability of wireless VoIP handsets is a question mark and there is a lack of handset accessories to suit the underground environment. References EMSLIE, A.G., 1975. Theory of the Propagation of UHF Radio Waves in Coal Mine Tunnels, IEEE Transactions on Antennas and Propagation, Vol. AP-23, No. 2, March 1975. DASYS, A., 2003, Implementing an Iredes based payload monitoring system, CIM 2003 GOLDHAMMER, S., 2004. Wireless System Design. Nortel Networks, 2003. Success Story Falconbridge Limited, WACLAWSKY, John, 2004. Cisco Systems DUDA, Andrzej, 2003. IEEE , 2003