Introduction
In the global sense the networks are divided into two types: wired and wireless. At present time the second type survives stormy bloom, but also usual wires are still capable of astonishing by the novelty of the technical solution. Of course this does not relate to classics of the genre – twisted pair and coaxial cable, but entirely – to the usual powerline, which also can come out in the role of the medium of the transmission of data. With the unquestionable advantages typical networking (twisted pair and coaxial) possess one essential deficiency: the necessity to be installed, i.e. to previously thinking over infrastructure, to plan the acquisition of wires and different active net equipment, to conduct nontrivial construction work and to finally connect everything together. The issue of mobility is not discussed in this case: in the situation, when it is required for the office, let us say, to move to another placement, at the new place the entire history of the installation of local network is repeated accurately vice versa: planning, cable laying and their commutation. Unfortunately, this can not be avoided, since the result nevertheless costs the preparation: the decent speed of transmission of data and the reliability of entire network as a whole cost that to the question of installation would be given the closest attention. In any matter does that factor is the same when the performance is not an issue or when the network is not a large scale type?
Background
It is not accidental that the use of powerline for organizing the local network interested engineers long ago. For solving the wide circle of near-electrical tasks was created the organization “HomePlug Powerline Alliance”: in March 2000 the most important IT- companies were combined for the purpose of development and advance of the corresponding standards, and today the number of participants in the alliance approached hundred.
Methods of Realization
The industrial standard HomePlug 1.0 provides the use for the transmission of data the OFDM (Orthogonal Frequency Division Multiplexing) method, which implies the frequency channel separation into several orthogonal subcarriers (there are 84 be subcarriers used) in the range from 4,3 to 20,9 MHz. For modulation of subcarriers relative quadrature-phase modulation is adapted with the shifting (Differential Quadrature Phase Shift Keying). As a protocol of access to the medium (MAC level) the CSMA/CA method (which the collective access with the detection by carrier and by avoiding collisions) is used. An increase in the noise immunity of connection is accomplished due to the tracking of coefficient “signal/noise” for each of sub-carrier frequencies and exception “noisy” channels, and also as a result of the use of excessive ultra-precise coding (speed 1/2 or 3/4) and applying Viterbi decoder on the assuming side. The packets of data are sent simultaneously in different carrier frequencies, which gives an increase in both the speed and the reliability. If interference arises and one frequency will fall out, it [chipset] will open this channel. Thus a similar Ethernet- connection on the electrical installation is achieved. In terms of security “Privacy is established by creating logical networks through the use of encryption. HomePlug’s privacy and security scheme are based on the 56-bit Data Encryption Standard (56-bit DES). Each station maintains a table of encryption keys and associated Encryption Key Select (EKS) values.” (Home plug white paper, p.7).
The HomePlug powerline alliance has set the following specifications:
- HomePlug 1.0 – Released June 2001 — Specification for linking hardware. Theoretical speed is 14 Mbit/s.
- HomePlug 1.0 Turbo – Unofficial specification for linking hardware. Theoretical speed is 85 Mbit/s.
- HomePlug AV — Released December 2005 — Designed for transmitting HDTV and VoIP around the home. Theoretical PHY information speed of up to 189 Mbit/s.
- HomePlug Command & Control (HPCC) — Released October 9, 2007 — It’s a low-speed, very low-cost technology proposed to match the alliance’s higher-speed powerline infrastructure technologies.
The technology of HomePlug 1.0 or AV will change the customary appearance of houses, networks and the quality and accessibility of networking. It will ensure the real possibility of distributing the data and specifically the multimedia content between the devices and will make domestic network as simple as inserting the device in electrical wall socket.
Conclusion
Although HomePlug AV – is a promising technology, it will encounter significant problems. It goes without saying, it is necessary to consider as real alternative to other net technologies (Wi-Fi, Ethernet, coaxial cable), which attempt to conquer the nascent market for multimedia domestic networks. The application of Wi-Fi more- is less justified as the method of flexible access to Internet, but when the discussion turns to the more moved applications (for example, on the transfer of video- and audio information on the domestic network), they require the alternative solutions. However, Andy Melder considers that HomePlug AV has significant advantages over competitors. The present domination of the technology of Wi-Fi in the domestic networks will end, as soon as people realize its limitedness from the point of view of the transfer of multimedia traffic. Especially serious problems can arise with the uniformity of the transfer of the flows of data on the wireless network.
Works Cited
HomePlug 1.0 Technology White Paper. (2005). HomePlug Powerline Alliance, Inc.
Palenchar, J. (2006). HomePlug AV Gets CES Demo; Products Seen As Early As Q2. Twice.com.
Katar, S., Krishnam, M., Newman, R., & Latchman, H. (2006). Harnessing the potential of powerline communications using the HomePlug AV standard. BroadBand Technology.
M. K. Lee , R. E. Newman , H. A. Latchman , S. Katar and L. Yonge. HomePlug 1.0 Powerline Communication LANs. (2000). INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, 00:1-6, 2-8.