Hacking_and_Penetration_Testing_with_Low_Power_Devices

156 CHAPTER 7 Building an army of devices
IEEE 802.15.4 devices may operate in a number of frequency bands. Frequencies
range from 779 to 10, 234 MHz. Devices only communicate with other devices on
the same band. The most common band and the one we will use in this book is the
2.4 GHz band. Devices using this band can transmit at speeds up to 250 kbps. Some
of the other bands provide longer range, but cannot be used in all countries.
IEEE 802.15.4 devices operating in the 2.4 GHz band communicate on one of 16
available channels. The channels are numbered 11 through 26. Center frequencies
vary from 2.405 to 2.480 GHz. Each channel is 5 MHz wide.
USING IEEE 802.15.4 NETWORKING
Digi International (http://digi.com) is one of the top manufacturers of IEEE 802.15.4
hardware. Digi markets IEEE 802.15.4 devices under the XBee brand name. Today,
the XBee name is used to refer to the form factor of a family of radios (some of which
are not IEEE 802.15.4 devices) sold by Digi. The XBee form factor utilizes two parallel
10-pin 2.00 mm pitch pins separated by 22.0 mm. Some people refer to all IEEE
802.15.4 devices as XBee devices even though this is not technically correct.
Digi produces low-power devices known simply as XBee modems with ranges of
up to 300 feet (90 m). They also make high-powered devices known as XBee-PRO
modems with ranges of up to one mile (1.6 km) for devices in the 2.4 GHz band. The
low-power non-PRO modems are preferred where possible for any device that is run
from battery power. XBee and XBee-PRO modems from the same series operating
on the same band can interoperate.
There are several series of XBee devices manufactured by Digi. For simple peerto-peer
or point-to-multipoint networking, the Series 1 adapters are the easiest
option. Implementing mesh networking is most easily accomplished with Series 2
or ZB modems. In this book, we will use Series 1 and Series 2 adapters exclusively.
As previously mentioned, IEEE 802.15.4 allows peer-to-peer and star networks
to be defined. A mesh networking standard known as ZigBee built on top of the IEEE
802.15.4 standard was initially released in 2004. This ZigBee standard is maintained
by the ZigBee Alliance (http://www.zigbee.org/). Both of these standards will be discussed
in this chapter.
POINT-TO-MULTIPOINT NETWORKING
All XBee devices can be operated in a peer-to-peer or point-to-multipoint (star) network.
The same cannot be said of mesh networks that require non-Series 1 XBee
devices. Before discussing point-to-multipoint network, we will consider the simplest
case of two devices in a peer-to-peer network.
In its simplest form, XBee can be used to replace a wired serial connection. This
functionality is very easily obtained using two XBee Series 1 adapters operating in
transparent mode. In transparent mode, all data sent to the XBee modem UART