DEPARTMENT OF ELECTRICAL ENGINEERING
MAHANT BACHITTAR SINGH COLLEGE OF ENGINEERING & TECHNOLOGY
Over the past few years advances in signal processing technology have enabled the advent of modem chips that are able to overcome the transmission difficulties associated with sending communications signals over electrical power lines. In the United States, this capability has been termed ―Broadband over Power Lines‖ or BPL. There are two predominant types of BPL communications configurations: Access BPL and In-Home BPL. Access BPL is comprised of injectors (used to inject High Frequency (HF) signals onto medium or low voltage power lines), extractors (used to retrieve these signals) and repeaters (used to regenerate signals to prevent attenuation losses). In addition to taking advantage of the power line infrastructure, In-Home BPL modems utilize the existing house wiring to provision a Local Area Network (LAN) that can be used throughout the home. One of the largest commercial markets for BPL is the ability to provide Internet Services by means of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocols, which can support voice, data, and video services. Another significant benefit of BPL is the ability to employ ―intelligent‖ power line networks that make use of Supervisory Control and Data Acquisition (SCADA) devices, dynamic provisioning, and other forms of modernized electrical power networks. A SCADA system can save time and money by reducing the need for service personnel to physically visit each site for inspection, data collection, and routine logging or even to make adjustments. The benefits also include the ability for real-time monitoring, system modifications, troubleshooting, increased equipment life, and automatic report generating.
The Federal Communications Commission (FCC) monitors approximately 59,000 frequencies for military, National Security & Emergency Preparedness (NS/EP), and other purposes. A key concern associated with BPL is that coupling of HF signals onto unshielded wiring, such as that used for outdoor power lines, may generate interference signals that could impact licensed services such as amateur radio, or ―hums‖. Public safety agencies including fire, police, the Red Cross and other agencies also depend on the use of the special propagation properties found only in the HF radio spectrum. This Technical report examines the architecture and considers possible benefits and concerns of BPL technology with respect to the National Communications System (NCS) and the communication requirements for NS/EP.
Broadband over Power Lines (BPL) is a term used to describe the use of existing electrical lines to provide the medium for a high speed communications network. BPL, also known as Power Line Communications (PLC) is achieved by superimposing the voice or data signals onto the line carrier signal using Orthogonal Frequency Division Multiplexing.
There are two main categories of BPL: in-house and access. In-house BPL is broadband access within a building or structure using the electric lines of the structure to provide the network infrastructure. Home Plug (Home plug, 2005) is an alliance of several vendors of in-house BPL products which has authored a standard for device compliance. Products conforming to the Home Plug standard have been commercially available since 2002. For example, Linksys offers the PLEBR10 (Linksys, 2005), an adapter which connects an existing router (which accepts the in-coming broadband from Cable or DSL) to the electric lines of the house. Other computers in the building can then connect to the network simply by attaching their computer's network card to an adapter (e.g. Linksys PLUSB10) plugged into a wall outlet. Access BPL is the use of the electrical transmission lines to deliver broadband to the home. AccessBPL is considered a viable alternative to Cable or DSL to provide the 'final mile' of broadband to end users. A BPL coupler placed at the pole converts the transmission medium from fiber (originating at the substation) to medium voltage power lines. Broadband signals traverse the medium voltage power lines, bypassing transformers, with repeaters placed every mile along the transmission path. At the final pole, a BPL wireless device can deliver the broadband to home-installed BPL wireless receivers, or, the signal can be sent to the individual homes via the low-voltage electrical lines and made available through any BPL wired receiver.
Despite the spread of broadband technology in the last few years, there are significant areas of theworld 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. Broadband overPower line is positioned to offer 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. 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). By modifying the current power grids with specialized equipment, the BPL developers could partner with power companies and Internet service providers to bring broadband to everyone with access to electricity. 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. (See Table 3.5 for comparison of access technologies). Fiber and advanced wireless broadband are the new alternative broadband access systems that are most likely to emerge in the next few years. These could also become a part of an integrated BPL system. Federal policy support is also strengthening the potential for BPL deployment. The FCC and others have hailed BPL as a potential ―third wire‖ that may help increase the availability and affordability of broadband services in a market dominated by digital subscriber line (DSL) and cable modem service. As part of the federal effort to remove barriers to BPL implementation, the FCC issued a change to Part 15 rules for measures to mitigate radio interference caused by broadband over power line. The FCC ruling on October 14, 2004 would essentially help to overcome BPL‘s potential to cause interference with radio and telecommunications signals. However, a number of jurisdictional and classification issues remain open. For example, are the broadband services offered via BPL considered an information service or a telecommunications service? This has implications since telecommunications services are subject to regulations under the Telecommunications Act of 1996, most notably common carrier requirements. As of October 2004, the FCC has two proceedings that address the issue of broadband regulatory classification: one deal with
cable modem services and another addressing all wire line broadband Internet access services generally. If classified as an information services, BPL service would be free frommany if not all common carrier regulations except, contribution to the universal service fund (USF). Reliability and safety of the power delivery system and provision of quality service are the main concerns for state commissions. In addition, affiliate transaction policies and cross subsidization issues are major concerns. State Commissions are obligated to prevent the unfair use of an asset developed with ratepayer funds for the benefit of shareholders. They are also obligated to ensure that electric utilities do not have an unfair advantage over competitors. Thus several solutions such as creation of unregulated BPL subsidiaries or implementation of accounting rules that guard against cross subsidization may be considered. The state regulators will also need to address rights of way, and access to poles issues. For instance, some municipalities may seek to charge fees for BPL rights of way. Pole attachment rules may also need to be addressed because of potential interference problems. The technical feasibility, the FCC rulemaking mitigating interference and the announcements of the commercial-scale tests of BPL have stimulated considerable interest in BPL among electric utilities, with several now evaluating deployment of BPL. The market trials and commercial deployments will reveal business case attractiveness of BPL compared to established DSL and cable services. However, there is also interest in BPL‘s potential to serve as a communications system that can support the network management of the power delivery system. The electric utilities will determine if the combined benefits of a system allowing for consumer telecom services, other consumer services, and core utility network communications help make the business model attractive for BPL. Utilities can consider applying three basic simplified business case models:
The Landlord Model – leasing the conduit and assets to a third party, probably with amaintenance arrangement
The Developer Model– a partnership or contract with an Internet service provider (ISP);the utility builds and owns the infrastructure, and the ISP handles all aspects of marketing, selling to and servicing the customer
The Service Provider Model– utility manages the system, including serving as theInternet service provider
Each utility will assess BPL according to its own business objectives, risk tolerance, andprocedures. The factors to evaluate are cost, market size and price, differentiating features of BPL, bundled services and average revenue per user, and the utility applications.