high data rate internet service over medium voltage power...
TRANSCRIPT
High Data Rate Internet Service over Medium Voltage Power Lines
Jae-Jo Lee, Young-Jin Park, Soon-Won Kwon, Hui-Myong Oh, Hae-soo Park, Kwan-Ho Kim
Korea Electrotechnology Research Institute (KERI) Euwang Shi, KOREA
Dae-Young Lee*, Young-Hwa Jeong** * Dept. of EE Engineering , Kyung-Hee University, Korea
** Dept. of Information & Comm. Engineering, Nam-Seoul University, Korea
Abstract—During the last several years, interest in broad-band power line communications (PLC) has been grown over medium voltage lines as well as low voltage lines. This paper introduces a medium voltage PLC test field that is set up in the suburbs of Euiwang city in Korea. This test field could be used not only to measure communication channel environment but also to serve of internet and VoIP (Voice over IP) service. This paper shows the configuration of MV test field with network devices and the results of service performance with network management system.
Keywords; Medium voltage power line, power line communications(PLC)
I. INTRODUCTION Recently, the demand for broadband Internet service is
increasing dramatically. In case of wired Internet access network, xDSL and cable networks are available in communi- cation market. Also, for wireless Internet networks, a wireless local area network is used and WiBro such as a future techno- logy is addressed. Unfortunately, however, these services are usually given to urban areas since building cost of networks is very high, thus the services are not profitable in rural areas. Due to the above reasons of the high cost establishment, a power line communication using pre-established power lines becomes more attractive for high data rate Internet and VoIP services. In other words, due to the usage of pre-established power line network nearly in the whole country, high data rate Internet access network can be realized easily with low installation cost.
Actually, as it is well known, 10Mbps and 100Mbps class modems have already come to markets. However, practical test of modem products, such as performance test and proof, system security and improvement should be done in advance for deployment of PLC network. For this purpose, a real practical PLC test field to test the developed PLC modem is necessary. In this work, a medium voltage PLC test field is set up for this reason. This test field could be used not only to test new modems but also to find their problems. Using the test field, we showed measurements of communications channel parameters such as noise, line impedance, and impulse response[1]-[5]. It is expected that the results are very useful for establishing PLC
subscriber networks and applying to developing high data rate modems.
In the paper, high data rate Internet service over overhead medium voltage (MV:22.9 kV) power lines will be introduced. This paper is organized as follows: In Section II, we described configuration of MV PLC Network and components. And in Section III, network management system is introduced with the structure of network and the actual performance results. Finally, it presented conclusions in Section IV.
II. TEST FIELD SETUP IN MEDIUM VOLTAGE LINES The test field has been constructed over about 5km at
Chunggae area located in the suburbs of Euiwang city near Seoul, Korea as shown in Fig. 1. This test field has been used efficiently for measurement of EMI environment, for service of internet and VoIP as a PLC subscriber networks.
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Fig. 1. Configuration of Medium voltage PLC test field.
As an overhead MV power line cable in the test field of PLC on MV power lines, an ACSR-OC (Aluminum Conductor Steel Reinforced Outdoor Cross-linked Polyethylene insulated Wires) cable is used. The cable consists of mainly three concentric layers of six aluminum cores, a steel core of 3.5 mm diameter in the middle of the six aluminum cores to reinforce the aluminum cores, and a dielectric insulator of cross-linked (XL) polyethylene. Also, it should be pointed out that a wire-to-ground (WTG) arrangement is applied, as is shown in Fig. 2.
0-7803-8844-5/05/$20.00 c 2005 IEEE. 405
Medium Voltage Power Lines, 22.9kV
COS
CouplingUnit
CoaxialCable
CouplingUnit Coupling
Capacitor
Drain Coil
Cut Off Switch
Signal Line
MV PLC Equipment
ImpedanceMatchingTransformer
Medium Voltage Power Lines, 22.9kV
COS
CouplingUnit
CoaxialCable
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Capacitor
Drain Coil
Cut Off Switch
Signal Line
MV PLC Equipment
Medium Voltage Power Lines, 22.9kV
COS
CouplingUnit
CoaxialCable
CouplingUnit Coupling
Capacitor
Drain Coil
Cut Off Switch
Signal Line
MV PLC Equipment
ImpedanceMatchingTransformer
Fig. 2. Illustration of signal coupling with MV coupling unit.
A. Coupling unit and MV PLC equipment Fig. 2 shows the way of coupling signals with 22.9 kV MV
power lines by way of a coupling unit. The coupling unit is composed of a capacitor of 2 nF for communication signals in the frequency band between 1 MHz and 30 MHz(less than 1dB attenuation) and an inductor of 1 mH in order to prevent a high-voltage power of 60 Hz from MV power lines. Due to harsh communication conditions of MV power lines, a cut-off-switch (COS) is used for protecting the coupling unit. A coupling unit is connected to a PLC modem through a coaxial cable of 75 Ω characteristic impedance and about 13 m long. Fig. 3. shows a photograph of overhead MV power lines and a coupling unit. In Fig. 4, it shows the photograph of installed MV network equipment with surge protection circuits.
Fig. 3. Photograph of a installed MV coupling unit
Fig. 4. Configuration of MV PLC equipment
B. Impedacne matching It is true that MV power lines are not suitable for a proper
communication media from the point of much noise and hard impedance matching. Particularly, impedance matching plays an important role on not only signal transmission, but also noise measurement[1].
In Fig. 6, input impedance looking into a 75 Ω coaxial cable from a PLC modem has been reported. The result will include the effect of the whole coaxial of MV power lines, a coupling unit, and MV power lines. As is shown, the signal is reflected periodically. By simple calculation of the resonance frequencies, it can be derived that the impedance mismatch is occurring at connection points between the upper end of the coaxial cable and the end of a coupling unit. Thus, impedance matching is necessary at the point between the coupling unit and the upper end of coaxial cable.
A broadband impedance matching technique is developed using a ferrite toroidal core and a flat cable in the frequency bandwidth from 1MHz to 30MHz. Several matching transform- ers with 75 Ω, 200 Ω, 300 Ω, 460 Ω, and 800 Ω are made. In Fig. 5, a broadband matching transformer is presented. Due to its compact volume, it is able to be equipped with the coupling unit together without increasing the volume and cost seriously.
Flat cable
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Fig. 5. Configuration of impedance matching transformer built in the coupling
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Fig. 6. Investigation of reflection behavior with different matching transformers.
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Cable Modem
EMS AgentSurge Protection Circuit
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Matching transformers are tested at different points in the test field. Some measured results are displayed in Fig. 6 and Fig. 7. In Fig. 6, the comparison of reflection is shown with three different matching transformers of 50Ω, 200 Ω, and 300 Ω. It should be noted that the case of 50 Ω is not using any matching transformer.
In Fig. 7, the results say that with an aid of matching transformers, the coupling unit has a good performance in terms of signal injection. In addition, it should be pointed that impedance matching result of about 300 Ω is better than any others. In the future work, we will develop the manual or automatic impedance matching device to adapt at various impedance environments.
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Frequency (MHz) Fig. 7. Investigation of input impedance behavior with different matching
transformers.
C. Specification of PLC modem The modems used for internet service were provided by
Xeline Co. Ltd.(Korea) that developed a single chip solution ‘XPLC21’ and produced several equipments, such as MV/LV modems, repeaters, couplers and EMS units for power line communications.
The XPLC21A, the core chip of modem, which adopted DMT(Discrete Multi-Tone) modulation and Hierarchical MAC(Medium Access Control) algorithm, can be used for all kinds of PLC transceiver units - Master, Slave and Repeater - with a simple firmware change for the embedded ARM9 processor.
DMT modulation performs well in the time varying power line channel and is easy to adopt an adaptive bit-loading method. Hierarchical MAC patented by Xeline makes the service coverage wider by multi-master and repeater functions. The XPLC21A has also a lot of useful functions; channel scanning, automated procedure for optimum rout search, adaptive bit-loading and power allocation, programmable notch filter, support of EMS(Element Management System) based on SNMP(Simple Network Management Protocol), data encryption, and so on.
It can support high data rate up to 24Mbps using frequency band of 2~23MHz. Its specifications are showed in Table 1 as numerical values and functional features[8].
Table 1. Specifications of PLC modems Data Rate Up to 24Mbps Modulation Type DMT based on PSK The Number of Sub-carriers 256
Frequency Band 2~23MHz Bit Loading 0/1/2/3 bits, adaptively Forward Error Correction Codes
Concatenated with Convolutional and RS Code
Multiple Access CSMA/CA Topology Master/Slave CMOS Technology 0.18um
Hierarchical MAC Channel Scanning function Automated Routing Procedure Co-existance of multiple master Programmable notch filter Adaptive Power allocation Changeable network configuration 56-bit DES encryption
Special Features
Half duplex by time division Package 100-pin TQFP package (14x14mm2)
III. NETWORK MANAGEMENT SYSTEM (NMS) A. Network configuration
The simple network management protocol(SNMP)[6] is a widely used standard for management of devices in IP networks. In network management using SNMP, a central NMS (Network Management System) gets management information in MIB (Management Information Base) by polling repeatedly embedded SNMP agents in remote devices to monitor the network resources. The manager monitors and controls a network by analyzing management information.
Fig. 8. Network Management System Structure
Fig. 8 shows NMS structure and how the manager gets management information of PLC modems or power line
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channel. PLC modems haven’t embedded SNMP agent. Therefore, the agent periodically communicates with master modems of Medium voltage Master(MM) and Low voltage Master(LM) to gather network management information. In the same way, MM and LM will ask Medium voltage Slave(MS) and Low voltage Slave(LS), respectively, for network management information such as performance, configuration, and so on. In this way, agents collect network management information of each modem. Then the manager patiently asks for the management information to the agents using SNMP, at each poll cycle, and the agents return the values of the requested MIB variables.
B. Management of Configruration, Performance For Internet service to tens of houses using the MV PLC
network, a PLC subscriber network is designed for supporting managements of configuration, performance, fault and security. Fig. 9 shows the screen view of configuration management of MV PLC subscriber network at Chunggae area point D. The manager is made by Web NMS platform[7], which is a management framework for building custom network management applications. As shown in Fig. 9, the PLC subscriber network consists of MV PLC network and LV PLC network, and the PLC modems are master-slave architecture. The modems are divided into 8 groups from 0 to 7, and each group can have one master, three repeaters, and 28 slaves.
Fig. 9. Screen view of configuration management
Performance management is an important part of the NMS and provides the means of measurement and presentation of various PLC network performance aspects. The various parameters, such as Transmit packet, received Bytes, AGC gain, puncturing flag and Bit Per Symbol can be measured and displayed. All parameters can store not only current performance data but also historical performance data. Fig. 10 shows the historical performance graph of received bytes in MV PLC modem. And “-S(Station)” is the value of download and “-SP(Station Parent)” is the value of upload. The original values of “ReceivedCumulative-xx” MIB variables are cumulated. But those in “Received Bytes graph” are result subtract previous value from current value. By default, historical data for the last 24 hours is displayed. It can choose among Today, Last one week, and Custom based on the range
of data you are looking for. The usual service speed is approximately between 3 and 5Mbps at every service point.
Fig. 10. Performance graph of received bytes in MV PLC modem
IV. Conclusion
Power line communication technology over medium voltage distribution line is attractive to build the access network. In the paper, it showed the result of field trial over medium voltage network. In the first, it showed the MV PLC network structure and the method of signal coupling to MV power line. Especially, MV signal coupler with impedance matching transformer was well matched for medium voltage power line with PLC network equipments in the communi- cation frequency band. Finally, it showed that PLC network over medium voltage is able to service from 3 to 5 Mbps internet speed at every point. In the future, we will develop the MV PLC network device to serve more reliable service and stable management and operations.
REFERENCES [1] Yu Jung-Hun, et al., "Impedance Measurement and Matching Technique
for Medium-Voltage Powerline Communcation", International Conference on Electrical Engineering, ICEE-188 ,2003.
[2] Hui-Myung Oh, Kwan-Ho Kim, Won-Tae Lee, and Jae-Jo Lee, “A Fundamental Study for Establishment of Channel Data Base in Power-Line Communications,” Trans. on KIEE, Vol. 52D, No. 2, pp.107-111, Feb. 2003.
[3] M. Zimmerman and K. Dostert, “Analysis and modeling of impulsive noise in broad-band powerline communications," IEEE Trans. on Electromagnetic Compatibility, vol. 44, no. 1, pp.249-258, Feb. 2002.
[4] Yong-Hwa Kim, Hak-Hoon Song, Jong-Ho Lee, and Seong-Cheol Kim, “Wideband Channel Measurements and Modeling for In-House Power Line Communication,” Proc. of International Symposium on Power-Line Communications and Its Applications, March 2002.
[5] J. J. Lee, et al. “Measurement of the communications environment in medium voltage power distribution lines for wide-band power line communications”, ISPLC 2004, Zaragoza, Spain, Mar/Apr. 2004, pp. 69-73.
[6] W. Stallings, “SNMP, SNMPv2, SNMPv3, and RMON 1 and 2,” Third edition, Addison-Wesley, Reading, MA, USA, 1999.
[7] http:://www.adventnet.com [8] http://www.xeline.co.kr
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