Diagram for Operation of WSNs

 Diagram for Operation of WSNs

 Diagram for Operation of WSNs

Acronyms Related to Wireless Sensor Network

ACK	Acknowledgement	Packet or transmission got through OK
ACL	Access Control List
AM	Amplitude Modulation
AP	Access Point
ARQ	Automatic Repeat reQuest	Sometimes called link level ACK or L2 ACK
ASK	Amplitude Shift Keying	A form of AM communication
BER	Bit Error Rate
CDMA	Code Division Multiple Access
CMOS	Complementary Metal Oxide Semiconductor	The standard family of processes used to manufacture integrated circuits.
CSMA	Carrier (or Channel) Sense Multiple Access	The channel is sensed before transmission is initiated. If the channel is busy, transmission is delayed. In some cases (e.g. Ethernet) the channel can be sensed during communication as well, in which case collisions can be detected (CSMA-CD). In wireless this is generally not possible, and only a subset of collisions can be avoided (CSMA-CA).
dB	decibel	One tenth of a Bell. 1 Bell = a factor of 10 in power.
dBm	deciBels relative to a milliWatt	1 Bell is an order of magnitude in power, so 10 deciBels relative to a milliWatt is 10mW. -10 dBm = 0.1mW. -90dBm = 1 picoWatt
ESA	Electrically Small Antenna	Any antenna for which 2pa/l < 1, where 2a is the maximum dimension of the antenna.
FEC	Forward Error Correction
FER	Frame Error Rate
FM	Frequency Modulation
FSK	Frequency Shift Keying	A form of FM communication
IETF	Internet Engineering Task Force	The organization that defines all of the internet protocols like IP, TCP, http, ftp, (www.ietf.org)
ITU	International Telecommunications Union	Major standards body
MAC	Medium Access or Medium Access Control	The Medium Access Layer is a sub-layer of the Data Link Layer, layer 2
MAC	Message Authentication Code	In wireless communications this is usually called a MIC to avoid confusion with the Medium Access layer.
MIC	Message Integrity Code
NACK	Negative ACK	Packet or transmission did not get through OK.
NET	Network layer
OOK	On Off Keying	A form of AM communication
OQPSK	Offset QPSK	RF modulation used by 802.15.4 in the 2.4GHz band
OSI	Open System Interconnection	A 7 layer model for representing the hierarchy of communication systems. Generally given as: application, presentation, session, transport, network, data link, physical
PDR	Packet Delivery Rate (or Ratio)	The fraction of packets that make it through a single hop with no errors.
PDU	Protocol Data Units	Data exchanged between layers in an OSI stack.
PER	Packet Error Rate
PHY	Physical layer
PM	Phase Modulation
PSDU	Physical layer Service Data Unit
PSK	Phase Shift Keying	A type of RF modulation, contrast AM and FM
QPSK	Quadrature PSK
RF	Radio Frequency
RSSI	Received Signal Strength Indicator	RSSI is a measure of how much power was received by the radio. Usually this is during reception of a packet, but sometimes just sampling the noise on the channel. RSSI is usually measured in dBm
TDMA	Time Division Multiple Access
TDOA	Time Difference of Arrival	Used in RF location systems
TOF	Time of Flight
TSMP	Time Synchronized Mesh Protocol
WSN	Wireless Sensor Networks

Block Diagram of Basic Node Components

Image for Block Diagram of Basic Node Components

Basic Node Configuration

A modular design approach provides a flexible and versatile platform to address the needs of a wide variety of applications.For example, depending on the sensors to be deployed, the signal conditioning block can be re-programmed or replaced. This allows for a wide variety of different sensors to be used with the wireless sensing node. Similarly, the radio link may be swapped out as required for a given applications' wireless range requirement and the need for bidirectional communications. The use of flash memory allows the remote nodes to acquire data on command from a base station, or by an event sensed by one or more inputs to the node. Furthermore, the embedded firmware can be upgraded through the wireless network in the field. The microprocessor has a number of functions including: 1) Managing data collection from the sensors 2) Performing power management functions 3) Interfacing the sensor data to the physical radio layer 4) Managing the radio network protocol A key feature of any wireless sensing node is to minimize the power consumed by the system. Generally, the radio subsystem requires the largest amount of power. Therefore, it is advantageous to send data over the radio network only when required. This sensor event-driven data collection model requires an algorithm to be loaded into the node to determine when to send data based on the sensed event. Additionally, it is important to minimize the power consumed by the sensor itself. Therefore, the hardware should be designed to allow the microprocessor to judiciously control power to the radio, sensor, and sensor signal conditioner

Block Diagram Of a typical Node

Image of typical wireless sensor node.

 

Image of typical wireless sensor node.