After years of development, technology to deliver high-speed data over the existing electric power delivery network has emerged in the marketplace. Called broadband over power line (BPL), this technology offers an alternative means of providing high-speed internet access, Voice over Internet Protocol (VoIP), and other broadband services, using medium- and low- voltage lines to reach customers’ homes and businesses.
Broadband over Power Line (BPL), also known as Power Line Communications (PLC) is a disruptive communications technology that enables power line infrastructure landlords (electric utilities & property owners) and their system operator partners to deliver a suite of Internet Protocol (IP) based services using their existing power distribution infrastructure.
BPL transmits high frequency data signals through the same power cable network used in carrying electrical power to household/or business subscribers. In order to make use of BPL, subscribers install a modem that plugs into an ordinary electrical wall outlet and pay a subscription fee similar to those paid for other types of Internet service.
1.1 Evolution of BPL
BPL is based on PLC technology developed in 1928 by AT&T Bell Telephone Laboratories, and which has been used for internal and low-speed data communication applications since that time by the electric power utilities. Based on PLC technology, some customer premises equipment (CPE) such as intercom systems, have used the embedded electrical wire to avoid the cost of special wiring. In Europe and most of the rest of the world, PLC standards allow for communications over the 220-240 volt power grid at frequencies of 30 KHz to 150 KHz. In the United States, the standards for the 120 volt power grid allow the use of frequencies above 150 KHz as well. Power utilities use the frequencies below 490 KHz for internal applications such as telemetry and monitoring and control of equipment at remote sub-stations. In the 1990s, development began on broadband over power line (BPL), which has since then been regionally standardized.
Despite the spread of broadband technology in the last few years, there are significant areas of the world that don't have access to high-speed Internet. When weighed against the relatively small number of customers Internet providers would gain, the incremental expenditures of laying cable and building the necessary infrastructure to provide DSL or cable in many areas, especially rural, is too great. But if broadband could be served through power lines, there would be no need to build a new infrastructure. Anywhere there is electricity there could be broadband. Technology to deliver high-speed data over the existing electric power delivery network is closer to reality in the marketplace. By combining the technological principles of radio, wireless networking, and modems, developers have created a way to send data over power lines and into homes at speeds between 500 kilobits and 3 megabits per second (equivalent to DSL and cable). The technology evolution in the next few years is important from a perspective of future competitive position of BPL as new networks are built and alternative technologies emerge.
Broadband access and services are delivered using a variety of technologies, network architectures and transmission methods. The most significant broadband technologies include:
· Digital Subscriber Line (DSL)
· Coaxial Cable
· Satellite
DSL is a very high-speed connection to Internet that uses the same wires as a regular telephone line. A standard telephone installation in the United States consists of a pair of copper wires. This pair of copper wires has sufficient bandwidth for carrying both data and voice. Voice signals use only a fraction of the available capacity on the wires. DSL exploits this remaining capacity to carry information on the wire without affecting the line’s ability to carry voice conversations.
But there are several limitations of DSL describe below :
· The quality of connection depends upon the proximity to the provider’s central
office, closer the better
· Receiving data is faster than sending data over the internet
· DSL is not available everywhere
For millions of people, television brings news, entertainment and educational programs into their homes. Many people get their TV signal from cable television (CATV) because cable TV provides better reception and more channels.
Many people who have cable TV can now get a high-speed connection to the Internet from their cable provider. Cable modems allow subscribers to access high-speed data services over cable systems that are generally designed with hybrid fiber-coaxial (HFC) architecture. Cable modem service is primarily residential, but may also include some small business service.
The disadvantage of coaxial cable is that when there are heavy-access users, are
connected to the channel, you will have to share the entire bandwidth, and may see your performance degrade as a result. It is possible that, in times of heavy usage with many connected users, performance will be far below the theoretical maximums.
Satellite Internet access is ideal for rural Internet users who want broadband access. Satellite Internet does not use telephone lines or cable systems, but instead uses a satellite dish for two-way (upload and download) data communications. Upload speed is about one-tenth of the 500 kbps download speed. Cable and DSL have higher download speeds, but satellite systems are about 10 times faster than a normal modem. Two-way satellite Internet consists of approximately a two-foot by three-foot dish, two modems (uplink and downlink), and coaxial cables between dish and modem. The key installation planning requirement is a clear view to the south, since the orbiting satellites are over the equator area. And, like satellite TV, trees and heavy rains can affect reception of the Internet signals.
1.2 Architecture of BPL
Broadband over Power Lines network is overlaid on the medium-voltage and low-voltage segments of the power distribution system. High-speed backhaul connections can be brought to the BPL network at substations or elsewhere along the medium voltage circuit. An Ambient node provides connectivity between the backhaul connection and the medium voltage segment of the BPL network. High speed data travels over this medium-voltage segment to remote locations where is it transferred to the low-voltage segment or to a wireless interface for the final leg to the end user or network element being managed. A simplified view is shown is Figure 1.2.
The diagram below (Inductive Coupling Injection Technique) shows how the BPL injector converts the IP data traffic into an RF signal in a signal cable. The signal is then injected into the MV or LV cable by induction using ferrite cores. This is known as “inductive coupling” and can be done without switching off power. An alternative injection technique, known as “conductive coupling” connects the signal cable directly to the electricity cables but requires the power to be switched off during connection for safety reasons.
The end-user simply connects a BPL modem to any power socket in the building for access to the BPL RF signal. The BPL modem converts the RF signal back into IP data. The enduser user then connects the BPL modem into a computer, server, switch, or wireless access point.
1.3 COMPONENTS OF BPL NETWORK
The entire BPL network can be built from a few basic types of components:
• Couplers that transfer the communications signal to and from power lines.
• Nodes that receive and transmit the signal from the medium and low voltage power lines. Nodes can be either terminal (receiving and transmitting between medium and low voltage lines), Repeaters (receiving and transmitting on a medium voltage line), or a combination of both.
• Modems that transfer the communications signal to and from end users. The modem is typically connected to either a router or the user's personal computer. In addition to an Ethernet interface, some models of Ambient's BPL modems contain a standard telephone jack for internet telephony applications.
NICs convert the digital data to communication signals appropriate for the power lines and convert the broadband over power lines signals back into digital data. NICs also provide error correction and security functions. Each node can contain up to three NICs, depending upon the node's function. Each NIC is connected to either a primary (medium voltage) or secondary (low voltage) power line through a coupler.
1.4 Working of BPL
In order to provide data communication, the initial BPL systems coupled radio frequency (RF) data signals into the existing electric power lines. The high frequency data signals are transmitted through the same power lines that carry low frequency electricity to the household or business. This enables both signals to coexist on the same wire.
From the specific technological perspective, the basic idea of BPL technology is to modulate a radio signal with data and send it through power lines in a band of frequencies which are not used for supplying electricity. The frequencies used and the encoding scheme have a significant influence on the efficiency and the speed of BPL service. The encoding scheme which is used by most of the BPL providers is Orthogonal Frequency Division Multiplexing (OFDM). OFDM is a technique used for transmitting large amounts of digital data over a radio wave. OFDM splits the radio signals into multiple smaller sub-signals that are then transmitted at different frequencies to the receiver. The transmission of data by OFDM along several of the carrier frequencies simultaneously increases speed and reliability. Data loss occurs when electrical distribution is interrupted by electrical devices turned on and off. OFDM uses small packets to deliver data within the home, losing only small amounts of data rather than the whole signal.
Another encoding scheme which is used in BPL is Direct Sequence Spread Spectrum (DSSS). DSSS is one of two types of “spread spectrum techniques” wherein a data signal at the transmitter is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio. The chipping code is a redundant bit pattern for each bit that is transmitted, which increases the signal’s resistance to interference. The redundancy of data helps in recovering the bits that are corrupted during data transmission.
From the system engineering perspective, BPL provides effective data communication through a combination of the electric network within the home or office, the power distribution grid, and the backbone network which transfers the data signal from the Internet Service Provider (ISP) to the power lines. BPL systems take advantage of one of the largest and the most pervasive networks, the power distribution grid.
The power distribution grid is made up of a number of components aimed at delivering electricity to customers, and includes overhead and underground Medium Voltage (MV) and Low Voltage (LV) power lines and associated transformers. First, power is generated at power stations and distributed around a medium to large geographical area via High Voltage (HV) lines. Second, in areas where power needs to be distributed to consumers, transformers will be used to convert this high voltage into a lower voltage to transport over MV power lines. These transformers are generally located at electrical sub-stations operated by the utility or power supplier. Such MV power lines will be used to transport electricity around smaller geographical areas such as small towns. Finally, for the purposes of using electricity in the home or business a transformer is used to reduce the voltage down to safer and more manageable voltages at the customer’s house or business premises. This power is usually transported over LV power lines. These LV power lines include the lines that traverse a customer’s home or business.
Figure 1.4 shows the simplified Medium Voltage (MV) BPL access network. The BPL signal in this network is transmitted over the MV system from a head-end in the local network, and for the purpose of final distribution of BPL service to the end user, either a local repeater to counter the signal-blocking effect of the local transformer, or alternatively a Wi-Fi wireless LAN access point can be used. In such countries as the United States where the local electricity supply is 120V, medium voltage (MV) systems deliver power very close to many premises with a very localised transformer providing the final 120V supply to relatively few premises, which can be as low as between one and six homes in rural areas.
Figure 1.5 shows the Low Voltage (LV) BPL access network, common in Europe and parts of Asia- Pacific. In this case, the system head-end is the local step-down transformer, and the LV wire is used for the broadband data distribution. In countries where the local electricity supply is 220-240V, the local step down transformer is usually located further from the final customer, and can distribute power to typically tens of hundreds of customers.
TAXONOMY OF BPL
BPL can be broadly categorized into two types:
- Access BPL
- In-House BPL
2.1 ACCESS BPL
Access BPL systems utilize the power distribution network, owned, operated and controlled by an electricity service provider, as the means of broadband delivery to and from premises such as the home or office. Access BPL systems use injectors, repeaters, and extractors to deliver high-speed broadband services to the end-user.
The Access BPL network belongs to broadband service providers. In this, the service provider with the help of some injection devices injects data signals into the medium and low voltage power distribution power network in order to provide Internet access. BPL signals may be injected onto power lines in several ways on or between different conductors. Since BPL signals cannot usually pass through an electric distribution transformer, additional equipment is usually required to allow the data signal to bypass distribution transformers, or to regenerate data, in order to get the data signal into a consumer’s home.
2.1.1 End to End Access BPL
End-to-end Access BPL systems use either a combination of MV and LV power lines or LV power lines only. These systems represent the classical architectures for Access BPL. In this case the BPL signal is injected onto and carried by the MV power line. The BPL signal is then transferred to the LV power line via couplers or through the LV transformer and delivered directly to the end-user. In the case of LV only BPL systems, the BPL signal is injected onto the LV power line at the transformer or the utility meter.
2.1.2 Hybrid Access BPL
Hybrid systems use a combination of power lines and wireless transmission. For example, a hybrid system may inject a BPL signal onto an MV power line and use a special extractor to translate the signal into a wireless channel which is delivered to the end-user.
As shown in Figure 2.2, the hybrid Access BPL system uses repeaters and extractors which are capable of transmitting and receiving wireless signals to and from end-users.
2.2 IN-HOUSE BPL
In-house BPL systems utilize electric power lines not owned, operated or controlled by an electricity service provider, such as the electric wiring in a privately owned building. Broadband devices are connected to the in-building wiring and use electrical sockets as access points
The only thing that the user has to do is plug the modem into the socket and connect it to the computer.
In-House BPL makes use of indoor adapters to transmit data signals over existing interior electric wires within a home, and to connect the data signals to various appliances.
In-house BPL systems use the electrical outlets available within a building to transfer information between computers and other home electronic devices and appliances which eliminate the need to install additional wires among devices.
Customer premise equipment (CPE)
There are such customer premise equipment in BPL network, which is describe below.
· USB Home Plug
Home Plug Additional Adapter with Ethernet or USB port – Internet access extension and home networking using your existing household power circuit.
· Ethernet Home plug
As shown in Figure 2.5, a BPL modem is plug_and_play and is roughly the size of a common power adapter. It plugs into a common wall socket, and an Ethernet cable running to your computer finishes the connection. Wireless versions are also available.
Because of low speed, low functionality and high development cost, BPL technology was never seriously considered as a communication medium, even though it has been operational since the 1930s. Historically, BPL was not only a control mechanism for electrical utilities, but also was originally designed to send simple commands over power lines at such low frequencies as 100-180 kHz. Such a mechanism makes both remote monitoring and diagnostics possible even over long distances. More recently, BPL has been used in “smart homes”. Smart homes can provide such automated applications as entry, entertainment, and comfort systems, and can be networked and controlled from a central location. A simple form of BPL also provides the basis for intercom systems.
In the mid 1980s, experiments on higher frequencies were carried out to analyze the technological characteristics of the electric power grid as a medium for data transfer. Frequencies especially in the range of 5-500 kHz were tested. In these tests, both the signal to noise levels and the attenuation of the signal by the power grid were important topics for measurements. These tests were undertaken both in Europe and in the United States.
3.1 Technological complexity and its challenges
The introduction of BPL technologies around the world has not been received with universal, unbridled enthusiasm due largely to interference concerns. The interference characteristics associated with BPL can be divided into two broad categories: (1) conducted and (2) radiated. In the FCC Report & Order 04-245, Access BPL systems are exempted from the conducted emissions limits in FCC Part 15 rules because measuring the conducted emissions presents a safety hazard due to the 1-40 kilovolt energy on the power lines. Instead, the FCC has focused on compliance with established radiated emission requirements.
3.2 Technological Issue
Power lines were not designed for data transmission, but were originally created to deliver power at 50 to 60 Hz. Broadband data can be transmitted at different frequencies, over the same wires, however, in order to enable high-speed and long-distance transmission of data on power lines several technological obstacles have to be overcome. These include data interference or electrical signal interference, the distance over which data can travel while still providing good quality, and the lack of international standards and specifications. The technological issues of BPL in this section deal with how BPL should be implemented to minimize interference with other services such as amateur radio frequencies and international standardization efforts for BPL technology to increase reliability, interoperability, and security of broadband transmission over power lines.
RFI has been one of the most serious potential obstacles to BPL. BPL systems have been shown to produce RF interference with nearby radio receivers, within up to 75 meters for mobile radios and 150 meters for fixed radios, according to the American Radio Relay League (ARRL). Also, various elements or structures in or near the powerlines readily become radiators or antennas at the high frequencies at which BPL data are transmitted. This presents a problem of interference with a variety of radio services.
BENEFITS OF BPL
Despite the proliferation of broadband access methods in many countries, some advantages could still be attained by rolling out BPL.
· Reduction in cost and weight as compared to ordinary wiring
Since it uses the existing infrastructure, BPL could mean that low-cost broadband could be made a reality in areas that cannot get DSL, cable or wireless broadband. Even homes in extremely remote areas could now potentially get broadband, without having to resort to the high latency satellite broadband.
According to a report conducted by the Shpigler Group, results suggest that BPL may be in the middle of the pack as far as deployment costs are concerned.
· Possibility of its use for smart appliances
The idea behind this is that you can control appliances with your PC. While these devices could potentially be connected with Ethernet to a DSL connection, BPL offers a much neater solution, since a single plug acquires both the device’s electricity and its data. Some propose this as an aid for people with mobility problems.
· Wireless Communication can be possible
One possible alternative is to use BPL as the backhaul for wireless communications, by for instance hanging Wi-Fi access points or cell phone base stations on utility poles, thus allowing end-users within a certain range to connect with equipment they already have. In the near future, BPL might also be used as a backhaul for WiMAX networks.
· Power Company can use BPL for system data communication needs
Automated metering.
Voltage control.
Remote equipment monitoring.
Energy management.
· High speed network
Media Fusion amazed customers and ISPs with promises of speeds up to 2.5 Gbps. However, to date, the company has failed to bring such promises to market. Instead, speeds of approximately 13 Mbps are standard. Such a system would quickly saturate but manufacturers are working on improving the technology to provide connections of greater speed, potentially making the technology viable.
PROBLEMS & SOLUTIONS
BPL technology has some problems and its solutions also, describe below.
5.1 PROBLEMS
BPL is more expensive, because more complex technologies are to be used in the chips. The power lines would need repeaters to maintain signal integrity and since the data signal cannot pass through transformers (in which case it would be lost), they must be bypassed.
Routing data around transformers can be costly. Since power supply networks vary from country to country, the cost of transformer bypassing can vary.
To generalize, houses take in a low voltage (LV), so the medium voltage (MV) used for transmission must pass through a MV/LV transformer before it can enter a house.
The cost of transformer bypassing is not the sole economic headache for potential providers. Since powerlines were never intended to be used for piggybacking data, a number of problems arose when trying to do so. These include high attenuation at high frequencies and noise (internal and external). As has been mentioned earlier, this leads to the necessity for a lot of error correction/prevention in any protocols using power lines as a physical layer.
One thing that cannot be resolved however is a failing in the electrical properties of the powerlines themselves. They act as aerials because they are not shielded. This means that they can pick up noise and transmit it on as well as emit interference. Unfortunately, BPL operates at the same frequencies as short wave radio and low-band VHF. This can render various radio systems including those of governments unusable. Amateur radio enthusiasts the world over seem to be united in their distaste for what BPL does to the airwaves. This interference has historically scuppered BPL trials. A good example of this is the Nor. Web trial that began in 1998 in Manchester. Despite complaints about the interference and warnings from the Radio communications Agency, the company consistently rubbished criticism and insisted that the roll out would take place. By the end of 1999, the company had been closed down. In Japan, the technology will not be adopted because of the interference problem.
Another problem with BPL is security. Since it transmits on a shared medium, like cable broadband, this makes it easier to snoop the line. Even though European operators have to spend less on transformer bypasses as has been already explained, the fact that the LV signal can potentially go to several hundred homes is not very secure. The same line going into many homes means the same traffic going down that line. This provides an opportunity for hackers to acquire sensitive data.
5.2 SOLUTIONS
The only proposed solution to the radio interference BPL causes is one proposed by Corridor Systems. They propose to use microwaves instead of the lower frequency bands to transmit the data, meaning that radio equipment should not be interfered with. Supposedly, this could lead to data rates of up to 216 Mbps.
In the US, the National Association for Amateur Radio (or ARRL, which has been one of BPL’s most vehement critics) has acknowledged that such a technology would not interfere with radio signals used by amateur radio enthusiasts. The electromagnetic spectrum is quite congested, however, and using the 2-20 GHz bands may just spawn more opponents to BPL.
Radio astronomers, who make use of several protected frequency bands from 13 MHz all the way up to 275 GHz, may be BPL’s next opponents. Given that the 1-10 GHz bands are especially important in this field of study, and that Corridor Systems’ 2-20 GHz BPL has not yet undergone extensive trials (or even been implemented?), we can only speculate at this time.
APPLICATIONS
Following are the various applications of BPL.
1. BPL can provide communications connectivity for Distribution Automation applications such as remote capacitor control, automatic meter reading and remote ON/OFF capabilities, among others.
2. BPL can be used to create an IP access network to solve the "Last-Mile" dilemma. Since the Grid is available throughout the country, BPL is simply an add-on to that existing electrical infrastructure which will allow every consumer to gain access to the Internet. Customer applications such as WWW access, Voice over Internet Protocol, video on demand. There are a number of basic applications for this BPL technology: telemedicine, and distance learning can be established on these systems.
3. Since the BPL network touches all of the electrical components connected to the electrical grid, there is an opportunity to install monitoring and security devices anywhere on the Grid which has been BPL enabled. The BPL network provides 2-way high-speed communications to all of these devices. Devices could include:
— Security Cameras
— Biological Contaminant detection
— Gas / Chemical detection
— Corrosion monitoring
— Pipeline Monitoring
6.1 GLOBAL BPL USAGE
A large number of utilities throughout the world are currently conducting trials or commercial operations of BPL. Some have already begun commercial operations
1. In Germany, the service is commercially offered by: "Vype", "Piper-Net" "PowerKom”, "EVOpowerline".
2. In Austria, the service is commercially offered in the city of Linz under the brand name "Speed-Web".
3. In Scotland, the service is offered in the cities of Crieff and Campbeltown under the name of "Broadband".
4. In the US, the service is offered by: Pennsylvania Power & Light, Cinergy, Progress Energy, City of Manassas (municipal owned utility), Central Virginia Co-op.
Other commercial deployments are already in operation in China, Hong Kong, Singapore and Korea.
CONCLUSION
As it is emerging technology, the next few years will decide whether BPL can compete in the broadband market.
BPL offers a method of broadband access for those living in isolated areas, who have no other viable means of broadband access. Therefore, it seems plausible that when BPL will become available in rural areas, it will be a moderate success. However, this success is unlikely to be long-term, since telecommunications companies are already contemplating rolling out FTTH (Fiber to the Home) connections to all of their customers sometime in the future. Therefore, it appears that BPL will be little more than a stopgap solution.
This was a really great read, appreciation for taking the time to put it together! Touched on some very good...
ReplyDelete