Smart Buildings Systems for Architects, Owners and Builders

radio frequencies, 2.4 GHz and 5 GHz. The Institute for Electrical and Elec-
tronics Engineers (IEEE) has set three standards for Ethernet communica-
tions via these frequencies, whicharecommonlyreferredtoasIEEE
802.11a, operating in the 5-GHz frequency, and IEEE 802.11b and 802.11g,
operating in the 2.4-GHz frequency. These standards can provide “optimal”
throughput of 11 Mbps (a measure of bandwidth, megabits per second) and
54 Mbps. Another standard, IEEE 802.11n, has been proposed and is
expected to be approved in late 2009. IEEE 802.11n will have a throughput
of 110 Mbps (Fig. 2.6).
The user’s distance from the antenna, the utilization of the same unlicensed
frequencies by other devices, obstacles inside buildings, and building structures
that interfere with the radio signals all affect the communications bandwidth
received from the Wi-Fi antenna.
Typical coverage areas indoors for omnidirectional Wi-Fi antenna are 100
to 300 feet. Each wireless access point (WAP) or gateway can generally serve
10 to 20 users depending on their applications. This technology and wireless
“hot spots” are now common in public buildings, airports, businesses, hotels,
restaurants and homes. The marketplace for Wi-Fi equipment is moving
toward “wire-line–class” security, high-performance, reliability, and enter-
prise-scale manageability of systems.

Audio

AM Broadcast

Short Wave Radio FM Broadcast

Television

Cellular (840 MHz)

NPCS (1.9 GHz)

Infrared Wireless LAN

902–928 MHz

26 MHz

(lEEE 802.15.4)

2.4–2.4835 GHz

83.5 MHz

(lEEE 802.11b/g)

(lEEE 802.15.4)

5 GHz

(lEEE 802.11a)

Ultra

High

Super

High

Extremely

Low

Ver y

Low Low Medium High

Ver y

High Infrared

Visible

Light

Ultra-

violet X-rays

Figure 2.6 Radio frequencies for Wi-Fi.

The Foundations of a Smart Building 17