Broadband over Power Lines (BPL), also known as Power Line Communications,is a rapidly evolving market that provides high speed broadband data communications at low cost. BPL systems couple radio frequency (RF) data signals onto the existing electric power lines to provide high speed data communication. The high frequency (1MHz – 30 MHz) data signals are transmitted through the same power lines that carry low frequency electricity (50 or 60 Hz) to household or business. This enables both the signals to coexist on the same wire .BPL provides effective data communication through the 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) onto the power lines.
One of the primary advantages of BPL is that most of the last mile infrastructure is in place. The last mile refers to the final segment of delivering communications connectivity to the home or office. BPL system takes advantage of one of the largest and the most pervasive networks on the earth.Power lines pass within 100 meters of almost every home or building in the United States. BPL offers to the residential and the business customers not only voice, video, and data services but also other incentives such as mapping and home management abilities that work more reliably and faster than in the past .
COMPONENTS OF BPL SYSTEM
The BPL network, like other high speed communication network requires the use of modems,routers and switches to provide a segmentation of the network. At the onset of the network deployment, the number of subscribers will be low, thus it will be cost effective to bridge the network segments. However, as the number of subscribers increase, network switches or routers can be used to maximize the bandwidth availability to the user. At higher subscriber densities,bandwidth can be maintained by using additional backhaul connectivity points. The data communication network overlays the utility distribution network and hence it requires a number of intermediate devices:
? S-Node positioned at the substation
? R-Node positioned mid span as repeaters
? X-Node positioned at the distribution transformer
? GW-Node positioned in the subscriber home in the form of customer premises equipment or gateway
The S-Node is used to connect the BPL network to the backhaul network which could be the Internet or the voice network or the data center. It is generally installed in the medium voltage substations where multiple medium voltage distribution lines areconnected. The S-Nodes can also be provided at any other point on the power distribution system, where the backhaul connection is required. The data from the SNode is injected into the distribution system by the use of a coupler.
The function of the transformer node is to transfer the information from the medium voltage to the low voltage lines. The distribution transformers highly attenuate the radio frequency (RF) signals used for power line communication. The RF signals bypass the distribution transformer through the transformer X-Node to deliver the signal to the customer premises. The transformer X-Node can also function as a repeater along the medium voltage line.Through the addition of a card, the X-Node can act as a repeater at a small incremental cost.
The RF signals, as they traverse through the power lines get attenuated and the signal strength reduces with distance. The repeaters are used at regular intervals to regenerate the signal. The signal from the repeater is extracted by a coupler, regenerated by the repeater and again injected into the power lines by a coupler .
The broadband over power lines is provided at the customer premise with the help of the GW-Node. It consists of an interface that connects to the electrical outlet inside the home through a standard electrical plug. It is modular in nature and supports a variety of other interfaces for in-home services such as data networks or telephony .