modulation that gives a data rate to
2.1 Mb/s. With 8DPSK modulation,
the data rate tops out at 3 Mb/s.
Version 3.0 -- known as Bluetooth
High Speed -- uses the same
transmission protocol, but employs a
Wi-Fi 802.11 radio link to get a data
rate up to 24 Mb/s.
Version 3.0 was created as a way
to let the Bluetooth protocol operate
over a Wi-Fi connection if available.
Bluetooth radios incorporate an
alternate MAC/PHY that is able to
dynamically select either the
Bluetooth radio or the Wi-Fi radio
based on the need for faster
transmission, or not.
More recent additions to
Bluetooth are versions 4.0/4.1. They
feature ultra-low power consumption
and encrypted connections. Also
called Bluetooth Low Energy (BLE),
these radios use very little power and
can run for months — even years —
on a single coin cell. BLE is also
known as Bluetooth Smart.
The BLE versions target anything
mobile or portable, including people.
The goal is to create wearable
wireless devices in watches, running
shoes, and medical monitoring
devices. Many of the newer
Bluetooth chips contain the standard
Bluetooth transceiver in addition to a
BLE transceiver.
Two newer BLE profiles or
applications are the heart rate profile
and the temperature profile. Both are
designed to enable the wireless
monitoring of body functions. They
provide a simple way to collect,
interpret, and display heart rate and
temperature data for training
purposes. Other similar applications
are on the way.
Aside from the health and fitness
areas, the Bluetooth 4.0/4.1 versions
also find use in PC peripherals like
mice and keyboards, or smart home
monitoring and control. BLE is
incorporated into smart watches that
link to a smartphone, and is also at
the heart of beacons — wireless
devices that sense when another
Bluetooth device is nearby, and
transmit location or other information
like ads. ICs like the one shown in
Figure 1 make BLE/smart applications
easier to develop.
The latest version of Bluetooth is
4. 2. It offers greater privacy, security,
and reliability of data transfers —
even lower power consumption,
increased speed, and IP connectivity.
It includes BLE features and is
backward compatible with previous
versions. The main data rate of BLE (1
Mb/s) is boosted to 2. 5 Mb/s.
However, the big feature of 4. 2 is the
ability of a Bluetooth device to
connect to the Internet.
This new feature uses a protocol
called 6Lo WPAN with IPv6 to let a
Bluetooth device connect through a
compatible gateway. This feature —
called the Internet Protocol Support
Profile (IPSP) — is an application for
4. 2 devices. This now makes
Bluetooth a prime candidate for Io T
applications.
ZIGBEE 3.0
ZigBee, like Bluetooth is another
short-range wireless standard that has
been around a while. It is based on
the IEEE’s popular 802.15.4 standard.
This standard provides the basic PHY
and MAC layers of the protocol,
while ZigBee adds more layers to
implement the applications. The
802.15.4 standard permits operation
in the 868 MHz band in Europe, the
902-928 MHz band in the US, and
the 2. 4 GHz band worldwide.
The most popular version shares
the 2. 4 GHz band with Bluetooth,
Wi-Fi, and a bunch of other wireless
technologies.
The standard provides 16 5 MHz
bandwidth channels. Modulation is
direct sequence spread spectrum
(DSSS) with BPSK or O-QPSK. The
access mode is carrier sense multiple
access with collision avoidance
(CSMA-CA). The power level is
typically 0 dBm, but up to + 20 dBm
can be used.
The range is 10 to 100 meters,
depending on the power level and
the environment. The data rate is 250
kb/s. A key feature of this standard —
and ZigBee — is its very low power
consumption.
ZigBee is a standard of the
ZigBee Alliance. It adds network and
application layers to the PHY and
MAC layers of 802.15.4. It
implements enhancements such as
authentication of valid nodes,
encryption for security and data
routing, and forwarding capability
that permits mesh networking.
Mesh networking lets any node
talk to any other node (if not directly,
then indirectly) by relaying messages
Go to www.nutsvolts.com/index.php?/magazine/article/March2015_OpenCommunication
to comment on this article.
March 2015 65
THE LATEST IN NETWORKING AND WIRELESS TECHNOLOGIES
■ FIGURE 1. This is Nordic Semiconductors’ nRF51822 integrated circuit
incorporating a complete Bluetooth smart transceiver, an ARM 32-bit Cortex
M0 processor with RAM, and special software that makes BLE applications
easier to implement.
