Ad hoc In wireless networking, Ad hoc refers to a network's ability to dynamically organize, or adapt to changes in the

node population without prior planning.

AES Advanced Encryption Standard. A U.S. standard FIPS approved encryption algorithm with a 128-bit cipher block

and symmetric keys of 128, 192 or 256 bits.

API Application Programming Interface. A collection of software procedures that simplify application code

development by abstracting the hardware interfaces.

ASK Amplitude Shift Keying. An RF modulation technique which varies the amplitude of the carrier signal to logically

represent ones and zeros.

Balun An impedance matching transformer typically used to convert differential voltages to single-ended voltages for use

with an antenna.

BAN Body Area Network. A wireless network composed of sensors in or around the human body, generally used for

sports, medical, or fitness equipment.

Bluetooth LE Bluetooth Low Energy, formerly called Wibree from Nokia. A 2009 update from the Bluetooth SIG (aka Bluetooth

4.0) which provides for an ultra low power, low data rate version of Bluetooth for WPANs. BLE uses the 2.4GHz

ISM band and FHSS modulation to provide up to 1Mb/s data rates.

BPSK Binary Phase Shift Keying. Also called 2-PSK. A type of PSK modulation which uses two phase shift values e.g. 0

and π.

Carrier Frequency The primary output frequency from an RF transmitter that is modulated by various methods to affect the transfer

of information.

CCA Clear Channel Assessment. A function of the PHY that indicates whether a selected channel is busy or idle.

Cluster Also called cluster-tree. In wireless networking, a cluster is a group of star-connected nodes with a master node

belonging to another superset of nodes in the hierarchy.

CSMA Carrier Sense Multiple Access. In wireless networks, is a low level protocol running at the MAC layer to ensure

clear access to a shared RF channel. The IEEE 802.15.4 radio uses CSMA/CA, a variation that includes a random re-

try delay on busy channels to reduce the probability of collisions.

dBm A unit of measure of RF power in decibels relative to one milliwatt i.e. 0 dBm = 1mW, 20 dBm = 100mW

D-QPSK Differential QPSK. A variation of QPSK modulation technique which a change in phase to indicate a logical one or

zero.

DSSS Direct Sequence Spread Spectrum. An RF encoding technique which replaces an information bit with a sequence

of much shorter pseudo-random bit "chips" prior to carrier modulation, thus spreading the original data across a

broader RF spectrum. This technique is used in 802.15.4 radios.

ED Energy Detect. A function of an RF receiver that indicates an external transmission is occurring on the RF band of

interest. Used as part of the channel selection algorithm.

ETSI European Telecommunications Standards Institute

FCC (United States) Federal Communications Commission

FFD Full Function Device. In IEEE 802.15.4 lexicon, an FFD is a network node that can operate as a coordinator or an

end device and includes routing capability. An FFD can communicate with other FFDs or RFDs.

FHSS Frequency Hopping Spread Spectrum. An RF modulation technique which divides the available RF bandwidth into a

number of sub-bands, and uses a coordinated schedule of "hops" between sub-bands to spread the original data

across a broader RF spectrum. This technique is used in Bluetooth radios.

FSK Frequency Shift Keying. An RF modulation technique which varies the frequency of the carrier signal to logically

represent ones and zeros.

HART Highway Addressable Remote Transducer protocol. A standardized (wired) sensor communication protocol that

provides digital data across a 4-20mA analog interface. Also see WirelessHART.

HVAC Heating Venting and Air Conditioning. Equipment that manages the indoor environment.

ISM A group of RF frequency bands reserved for unlicensed use for industrial, scientific and medical applications,

including 915MHz, 2.4GHz and 5.8GHz.

A Glossary of Wireless Sensor Network Terms

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MAC Media Access Control. The first protocol management layer immediately above the physical layer (PHY). The MAC

is responsible for operating the algorithm that ensures fair access to a shared medium.

MEMS Micro-Electro-Mechanical Systems. Micron-scale mechanical devices manufactured using IC fabrication

techniques, typically for gyroscopes, accelerometers and other miniaturized sensors.

Mesh In its strictest sense, a fully connected mesh network allows any node to communicate directly with any other

node. In practical wireless networking, variations with intermediate routing are still described as mesh networks

because of their ability to create large interconnected networks where any node can (ultimately) communicate

with any other node via multiple pathways.

Modulation The technique used to vary an RF carrier signal to encode the information being transmitted. Modulation

techniques generally fall into three categories - amplitude, frequency or phase modulation.

Multi-path fade Occurs when multiple copies of the original RF signal, reflected from alternate pathways and thus delayed in time,

combine out of phase to partially cancel each other at the receiver node, possibly causing receive errors.

Nonce Number used once. For network security, a pseudo-random number, often a time stamp, used to authenticate a

data transmission. Typically, subsequent transmissions use a new nonce.

NWK Network layer of the protocol stack which provides packet routing services.

OOK On-Off Keying. An RF modulation technique which uses the presence or lack of presence of the carrier signal to

represent logical ones and zeros.

O-QPSK Offset-QPSK. A variation of the QPSK modulation technique which uses stepped phase shifts to limit any single

phase change to 90°.

OSI Open System Interconnection. The OSI model provides a nomenclature describing seven layers of a network

architecture - Application, Presentation, Session, Transport, Network, Data-Link, and Physical. In practice, most

network architectures combine one or more layers for simplicity.

PA Power Amplifier. In wireless nodes, the PA is a specialized high frequency amplifier that boosts the power of the

transmitted RF signal.

PHY Physical Layer. In the OSI seven layer networking model, the PHY is the lowest layer, defining the electrical

signaling requirements for the actual physical medium of the network.

Piezoelectric effect Explains the generation of electric potential in the molecular lattice of certain ceramic materials when under

mechanical strain. Vibration energy harvesters exploit this effect, generating an AC voltage from a flexing

mechanical system tuned to specific resonant frequencies.

Protocol Stack In wireless networks, the protocol stack is a collection of software or firmware modules that govern the interaction

of nodes on the network to ensure interoperability. ZigBee and WirelessHART are two examples.

PSK Phase Shift Keying. An RF modulation technique which varies the phase of the carrier signal to logically represent

ones and zeros.

QAM Quadrature Amplitude Modulation. An RF modulation technique which uses a combination of PSK and ASK to

represent multiple bits per symbol.

QPSK Quadrature Phase-Shift Keying. Also called 4-PSK. A type of PSK modulation which uses four phase shift values e.g.

0, π/2, π, and 3π/2, to represent two logical bits per transmitted symbol.

RF Radio Frequency.

RFD Reduced Function Device. In IEEE 802.15.4 lexicon, an RFD is a network node that can only operate as an end

device. An RFD can only communicate with one FFD coordinator node, not other RFDs.

RSSI Received Signal Strength Indicator. A feature of RF receivers that provides an analog DC or digital indication of

received RF power in the band of interest. If other propagation factors are known, the RSSI can be used in

lateration techniques to estimate distance to a transmitter.

RTLS Real Time Locating Systems use various RF signal processing techniques to locate and track a tagged item in real

time within a wireless network. The IEEE 802.15.4a amendment adds RTLS capability to the 802.15.4 radio.

Seebeck effect Explains the generation of electric current from the transfer of charge carriers across a junction of two dissimilar

metals when subjected to a temperature gradient This effect is exploited in thermal energy harvesters, which

generate small amounts of electric power from devices maintained under a thermal differential.

Self-healing The ability of the network to detect and recover from faults appearing in either network

nodes or communication links, without human intervention.

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Self-organizing The ability of network nodes to detect the presence of other nodes and to organize into

a structured, functioning network without human intervention

SoC System-on-Chip. An IC that combines multiple functions such as a microcontroller, analog and integrated radio on

a single chip to create a complete functional system for a specialized task such as wireless sensors.

Stack see Protocol Stack

Star In wireless networks, a star topology is a group of nodes with independent links to a single master analogous to a

wheel with a hub and spokes. The master manages all slave nodes and all upstream communication.

TDMA Time Division Multiple Access. A technique which divides access to a shared channel or frequency into multiple

synchronized time slots, with each node transmitting only during its uniquely assigned time slot.

UWB Ultra-wideband. An RF transmission technique characterized by fast-edged data pulses rather than modulation of

a carrier wave, thus spreading the transmitted energy across a wide swath of bandwidth. UWB radios provide

more precise time-of-flight measurement for real time locating systems.

Wi-Fi™ The wireless LAN protocol based on the IEEE 802.11 standard and maintained by the Wi-Fi Alliance. The 802.11

radio uses DSSS modulation and the 2.4GHz and 5GHz frequency bands and provide data rates up to 600 Mb/s.

WirelessHART A WSN protocol maintained by the HART Communications Foundation which extends the wired HART protocol to

wireless sensors. The protocol utilizes the 2.4GHz ISM band and the IEEE 802.15.4 radio and supports a self-

organizing, self-healing mesh topology.

WPAN Wireless Personal Area Network. The IEEE 802.15 Working Group develops and maintains standards for short

distance wireless networks and Personal Area Networks to ensure interoperability for portable and mobile

computing devices.

WSN Wireless Sensor Network

ZigBee A wireless protocol suite, governed by the ZigBee Alliance, for low cost, low power remote monitoring and control

applications. ZigBee relies on the IEEE 802.15.4 radio for operation in the 868/915MHz and 2.4GHz ISM bands to

provide data rates up to 250Kb/s. It provides multi-vendor interoperability for self organizing, self healing

networks in a variety of topologies and application profiles.

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