Home Is Home: The Physical Practicalities - Smart Home Automation with Linux and Raspberry Pi - page 146

Wireless Points
Wireless is an addition to a wired network, not a replacement for it, so the WiFi routers and repeaters should exist to
provide access primarily in those places where a wired network isn't already available. This often includes the kitchen,
porch, and shed. Additionally, having wireless access in the main living spaces makes it easier to move around when
the communal areas get too busy or noisy to work in. Consequently, placing an access point in rooms at the back of
the house may be preferable. It doesn't need to be located in Node0, because it is wireless; therefore, provided it is
connected to the wired network at some point, you will be fine. As noted earlier, there will be some instances when
Node0 cannot physically provide WiFi coverage to the necessary areas of the house.
The position of the access point, however, is not an obvious choice since its range is affected by interference and
obstructions, as well as distance. And these can only be determined empirically. Begin by placing the access point
near the ceiling in a central part of the house, because this will give the best “line-of-sight” connection to most of the
building, and then test the signal strength. You can buy specific devices for this, but unless you can borrow one, it's
cheaper and no more difficult to walk around the house with a laptop.
WiFi signals are lost by two methods, absorption and reflection, and although walls cannot be avoided in a home,
partition walls have less absorption effects than structural ones made of brick. Shiny surfaces, including glass, mirrors,
and metal should also be avoided because the reflection of the signal introduces more internal protocol collisions and
therefore less bandwidth and more dropped connections.
I've mentioned some of the devices operating in the WiFi 2.4GHz range, such as TV senders, cordless phones,
microwave ovens, and baby monitors, which can also create interference, but you should not forget that other electrical
devices, such as motors, fan heaters, and fluorescent lighting, can also have a negative affect.
Instead of WiFi, you can achieve pseudowireless connectivity by using Ethernet over Power to limit these
problems. There are several EoP devices on the market (such as the MicroLink dLAN) where each unit plugs into both
the wall socket and a networked device. Since this uses the same idea as X10, whereby a signal is hidden on the mains
supply, it is susceptible to the same noise and interference.
Audio Cabling
Chapter 3 covered the idea of remote processing, whereby the music is decoded on a PC and the resultant signal is fed
over standard audio cables to other speakers or amplifiers. The process of adding this wiring is fairly simple, since the
cables are fewer in number, thinner, and more flexible than Cat5, which requires smaller holes and less mounting at
each end. A standard stereo pair consists of only four wires, with two connectors at each end for left and right. You can
use any connector you prefer, but phono sockets are good enough quality, easy to mount, and cheap.
The face gang plates for AV are more expensive than you'd expect, especially when compared to the cost of the
(more complex) Cat5 sockets, but they usually come with extra sockets for SVGA monitors and composite video. With
a drill, however, you can build your own using a standard blank facing plate, as shown in Figure 4-3 .