Motorola Shows You the Network Through the Powerlines

Using cable network infrastructures to connect to the Internet is not always possible. The reasons for avoiding the classic approach to networking range from the company having moved into new offices that haven't been designed with a cable network or the overall costs of cabling the office would blow the budget to pieces.

Motorola's Powerline Multiple-Unit (MU) Gateway eliminates the hassle of maintaining a cable architecture and offers a comfortable method of providing buildings with LAN connectivity over the mains electricity supply. Ethernet signals are converted into the HomePlug protocol and then injected into the building's electrical system.

Injection can be done using two methods, namely inductively coupled injection or capacitive injection. The former consists of non-conductive ferrite rings wrapped around the electric cables in the mains cabinet, without any direct contact to the main power lines. The signal diffuses through the insulation and propagates along. The latter method uses capacitive cords that are directly plugged into the mains outlet.

The gateway operates in the 4-21MHz spectrum and is available for use both in single-phase and three-phase power systems. The low-voltage design prevents the unit from working on powerlines that exceed 230 volts / 50 Hz specifications. As the power lines are an open network, the Powerline MU Gateway secures the data using the 56bit Data Encryption Standard.

The LAN-Over-Mains can deliver raw data rates around 85Mbit/s with a real threshold situated at about 8-12Mbit/s per gateway. The signal can range up to 100 meters from the gateway, but Motorola optionally provides additional modem distribution units that act as repeaters to increase signal strength over the powerlines.

The network settings can be managed via the gateway interface. It allows the user to manage the network encryption keys, the DHCP settings as well as the authentication servers. The software offers a network map showing the current modems in use and their state.

The gateway is useful when classical networks are unavailable. However, the provided speed is much lower than in the UTP networking. The Motorola MU base kit costs around $2115, not to mention the "optional" repeaters - which prove themselves essential at ranges over 100 meters. The overall classification would be "less-effective and much more expensive than a normal network: only if you really have to do without cables".