Information Technology Reference
In-Depth Information
receiver must be less than 30°. Despite this important drawback, IrDA is the
current standard for infrared connections, being very common in notebooks,
PDAs, cellular phones and other mobile devices.
The data transfer rate of IrDA connections can be up to 4 Mbps, but it can
reach 16 Mbps with the latest version of the standard (fast infrared, FIr).
IrDA can be also used for serial connections (serial infrared, SIr). In this
case, it can reach a maximum data transfer speed of 155 Kbps.
The intrinsic drawbacks of IrDA, mainly due to its short operational
range, are often exploited as security features. In fact, it is almost impossible
to hack an IrDA connection with active or passive attacks (such as man-in-
the-middle or sniffing), unless the hacker is very close (and within the sight
constraints) to the attacked hosts.
5
HomeRF
HomeRF is a wireless technology designed for domestic applications. It is a
standard developed by the HomeRF Working Group, which is also part of
the Bluetooth SIG [13], and it uses the same frequency band as Bluetooth
and Wi-Fi (ISM 2.4 GHz). HomeRF is supported by big companies such as
Motorola, Intel and Compaq, all of them are producers of digital communica-
tion devices for home applications.
HomeRF is based on the Shared Wireless Access Protocol (SWAP),
which allows for six voice channels (according to the DECT standard) and a
Wi-Fi data channel. The first versions of these devices had a maximum data
transfer rate of 2 Mbps, but the newer appliances achieve higher transfer
rates, up to 10 Mbps, by means of the SWAP version 2.0.
HomeRF uses the FHSS modulation to increase security and reliability,
and to reduce interferences. Since it does allow for ad-hoc point-to-point
connections only, there is no need of APs and the needed hardware is quite
simple. This makes HomeRF a cheap choice for home wireless networks.
Lower costs and simpler hardware have a negative effect on the covered
range (less than 30 m) and interoperability with any existing wired
network.
6
Wireless technologies comparison
The comparison of above-discussed technologies is not easy, because some
technologies are complementary rather than competing.
Table 1 shows a comparison of wireless technologies for home automa-
tion, indicating the applications they were originally designed for, the modu-
lation, the maximum bit rate and the standard issuers.
