Power Line Communications (PLC) allows transmission of data over power lines. PLC is potentially the network with the deepest capillarity in the world, since power lines are almost ubiquitous. Powerine communications is a rapidly evolving market that utilizes electricity power lines for the high-speed transmission of data and voice services.
PLC works by transmitting high frequency data signals through the same power cable network used for carrying electricity power to household users. Such signal cannot pass through a transformer. This requires devices ("outdoor devices") that combine the voice and data signals with the low-voltage supply current in the local transformer stations to bridge the last mile. In the house, "indoor devices" (adapters) are used in order to filter out the voice and data signals and to feed them to the various applications (e.g. PC/Internet, telephone, etc.).
The technology has roots going back to the 1940s. It has been used by power utilities for simple telemetering and control of electrical equipment in their networks. What is new is the integration of activities outside the building with those inside the building at a much higher bandwidth, 2.5 mbps or higher – this means voice and data transmission via the mains supply voltage network right through to every power socket in the building, as well as in the reverse direction at high speed.
Connecting to the Internet is a fact of life for business, government, and most households. The lure of e-commerce, video on demand, and e-mail has brought 60 million people to the Internet. Once they get to the Internet, they find out what it’s really like. That includes long waits for popular sites, substantial waits for secure sites, and horrible video quality over the web.
Telephone companies have offered high bandwidth lines for many years. For the most part, the cost of these lines and the equipment needed to access them has limited their usefulness to large businesses. The lone exception has been ISDN (Integrated Services Digital Network) which has won over some residential customers. ISDN offers fast Internet access (128k) at a relatively low cost.
Here the solution is Powerline communications (or PLC). Powerline communications is a rapidly evolving market that utilizes electricity power lines for the high-speed transmission of data and voice services.
None of the available Internet access services offer the right balance of cost, convenience, and speed. Digital Powerline technology could change all that. It gives customers high speed Internet access through electrical networks. Lower costs are achieved because the service is implemented on standard electrical lines. The service is also convenient because it’s already in your home. Internet access through Digital Powerline would be at (at least) 1Mbps, 20 times faster than a standard phone/modem connection.
History
The technology has roots going back to the 1940s.It has been used by power utilities for simple telemetering and control of electrical equipment in their networks.
What is new is the integration of activities outside the building with those inside the building at a much higher bandwidth, 2.5 mbps or higher.
Overview of Technology
PLC works by transmitting high frequency data signals through the same power cable network used for carrying electricity power to household users. Such signal cannot pass through a transformer. This requires devices that combine the voice and data signals with the low-voltage supply current in the local transformer stations. The signal makes its way to neighborhoods and customers who could access either it wirelessly, through utility poles.
Digital Powerline use a network, known as a High Frequency Conditioned Power Network (HFCPN), to transmit data and electrical signals. A HFCPN uses a series of Conditioning Units (CU) to filter those separate signals. The CU sends electricity to the outlets in the home and data signals to a communication module or "service unit". The service unit provides multiple channels for data, voice, etc. Base station servers at local electricity substations connect to the Internet via fiber or broadband coaxial cable. The end result is similar to a neighborhood local area network.
The Server
The Digital Powerline base station is a standard rack mountable system designed specifically for current street electricity cabinets. Typically, one street cabinet contains twelve base station units, each capable of communicating over 1 of 40 possible radio channels. These units connect to the public telecommunications network at E1 or T1 (*see appendix D) speeds over some broadband service.
Several options, with different costs, can provide broadband Internet service to each base station. The simplest solution is connecting leased lines to each substation. This solution is potentially quite costly because of the number of lines involved. A wireless system has also been suggested to connect base stations to the Internet. This option reduces local loop fees, but increases hardware costs. Another alternative involves running high bandwidth lines, along side electric lines, to substations. These lines could be fiber (*See appendix C), ATM, or broadband coaxial cable. This option avoids local loop fees, but is beset by equipment fees. The actual deployment of Digital Powerline will probably involve a mix of these alternatives, optimized for cost efficiency in different areas and with different service providers.
These base stations typically serve approximately 50 customers, providing over 20 MHz of usable spectrum to near end customers and between 6 and 10 MHz of useable spectrum to far end customers. The server operates via IP to create a LAN type environment for each local service area.
The HFCPN Conditioning Unit
The conditioning Unit (CU) for the Digital Powerline Network is placed near the electric meter at each customer’s home. The CU uses band pass filters to segregate the electricity and data signals, which facilitate the link between a customer’s premise and an electricity substation.
The CU contains three coupling ports. The device receives aggregate input from its Network Port (NP). This aggregate input passes through a high pass filter. Filtering allows data signals to pass to a Communications Distribution Port (CDP) and a low pass filter sends electric signals to the Electricity Distribution Port (EDP).
The 50 Hz signal flows from the low pass filter, out of the EDP and to the electricity meter. The low pass filter also serves to attenuate extraneous noise generated by electrical appliances at the customer premises. Left unconditioned, the aggregation of this extraneous noise from multiple homes would cause significant distortion in the network.
The high pass filter facilitates two way data traffic to and from the customer premise. Data signals flow through the CDP to the customer’s service unit via standard coaxial cable.
Service Unit
The service unit is a wall or table mountable multi-purpose data communications box. The unit facilitates data connections via BNC connectors to cable modems and telephone connections via standard line termination jacks. The service unit provides its own line power for ringing and contains a battery backup in case of power outage. Alternative Differential Pulse Code Modulation (ADPCM) is used for speech sampling. Because Digital Powerline allows for the termination of multiple radio signals at the customer premises, the service unit can facilitate various Customer Premises Equipment (CPE) simultaneously. In a manner similar to ISDN, data (computers) and voice (telephones) devices can coexist without interfering with each other.
Digital Powerline technology is an exciting alternative to connecting to the Internet via phone and modem. Though this technology is not commercially available yet, it should be available before other broadband technologies due to the relatively low cost of its local loop. Moreover, its high speeds will provide Internet access, video on demand, local phone, and long distance phone services to customers.
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