Wireless Sensor Network

Network technologies are developing fastly with this improvements sensor has promoted.  

At first all sensor has one connection with host machine, but this method is occurs high cost, configuration management is difficult.

With wireless sensor network, sensors connected with each other and create a network this method is reduce costs and complexity.


They are autonomous devices and monitoring physical or environmental conditions such as:

  Temperature
Sound
Vibration 
Pressure
Motion

Sensor network is typically equipped with radio transceiver or other wireless communications device, a small microcontroller, an energy source, usually a battery.

The cost of sensor nodes is similarly variable, hundreds of dollars to a few cents, depending on the size, weight, energy consumption, sensitivity, speed and bandwidth.


The development of wireless sensor networks was originally for military applications such as battlefield surveillance.

However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.

Satellite-Related Terms

Earth Stations – antenna systems on or near earth

Uplink – transmission from an earth station to a satellite

Downlink – transmission from a satellite to an earth station

Transponder – electronics in the satellite that convert uplink signals to downlink signals

Mobile Switching Center (MSC) Databases

Home location register (HLR) database – stores information about each subscriber that belongs to it

Visitor location register (VLR) database – maintains information about subscribers currently physically in the region

Authentication center database (AuC) – used for authentication activities, holds encryption keys

Equipment identity register database (EIR) – keeps track of the type of equipment that exists at the mobile station

Cellular Systems Terms

Base Station (BS) – includes an antenna, a controller, and a number of receivers

Mobile telecommunications switching office (MTSO) – connects calls between mobile units

Two types of channels available between mobile unit and BS

-Control channels – used to exchange information having to do with setting up and maintaining calls

-Traffic channels – carry voice or data connection between users

IEEE 802.11a and IEEE 802.11b

IEEE 802.11a

-Makes use of 5-GHz band

-Provides rates of 6, 9 , 12, 18, 24, 36, 48, 54 Mbps

-Uses orthogonal frequency division multiplexing (OFDM)

-Subcarrier modulated using BPSK, QPSK, 16-QAM or 64-QAM

IEEE 802.11b

-Provides data rates of 5.5 and 11 Mbps

-Complementary code keying (CCK) modulation scheme

IEEE 802.11 Architecture

Distribution system (DS)

Access point (AP)

Basic service set (BSS)

-Stations competing for access to shared wireless medium

-Isolated or connected to backbone DS through AP

Extended service set (ESS)

-Two or more basic service sets interconnected by DS

Differences between LLC and HDLC

LLC uses asynchronous balanced mode of operation of HDLC (type 2 operation)

LLC supports unacknowledged connectionless service (type 1 operation)

LLC supports acknowledged connectionless service (type 3 operation)

LLC permits multiplexing by the use of LLC service access points (LSAPs)

LLC Services

Unacknowledged connectionless service

No flow- and error-control mechanisms

Data delivery not guaranteed

Connection-mode service

Logical connection set up between two users

Flow- and error-control provided

Acknowledged connectionless service

Cross between previous two

Datagrams acknowledged

No prior logical setup

MAC Frame Format

MAC control

Contains Mac protocol information

Destination MAC address

Destination physical attachment point

Source MAC address

Source physical attachment point

CRC

Cyclic redundancy check

Separation of LLC and MAC

The logic required to manage access to a shared-access medium not found in traditional layer 2 data link control

For the same LLC, several MAC options may be provided

Internetworking Terms

Communication network – facility that provides a data transfer service among devices attached to the network

Internet – collection of communication networks, interconnected by bridges/routers

Intranet – internet used by an organization for internal purposes

-Provides key Internet applications

-Can exist as an isolated, self-contained internet


End System (ES) – device used to support end-user applications or services

Intermediate System (IS) – device used to connect two networks

Bridge – an IS used to connect two LANs that use similar LAN protocols

Router - an IS used to connect two networks that may or may not be similar

Layers of the OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical


OSI Application Layer

Provides access to the OSI environment for users

Provides distributed information services


OSI Presentation Layer

Provides independence to the application processes from differences in data representation (syntax)


OSI Session Layer

Provides the control structure for communication between applications

Establishes, manages, and terminates connections (sessions) between cooperating applications


OSI Transport Layer

Provides reliable, transparent transfer of data between end points

Provides end-to-end error recovery and flow control


OSI Network Layer

Provides upper layers with independence from the data transmission and switching technologies used to connect systems

Responsible for establishing, maintaining, and terminating connections


OSI Data link Layer

Provides for the reliable transfer of information across the physical link

Sends blocks (frames) with the necessary synchronization, error control, and flow control


OSI Physical Layer

Concerned with transmission of unstructured bit stream over physical medium

Deals with accessing the physical medium

Mechanical characteristics

Electrical characteristics

Functional characteristics

Procedural characteristics

TCP/IP Layers

Physical layer

Network access layer

Internet layer

Host-to-host, or transport layer

Application layer

TCP/IP Physical Layer

Covers the physical interface between a data transmission device and a transmission medium or network

Physical layer specifies:

Characteristics of the transmission medium

The nature of the signals

The data rate

Other related matters


TCP/IP Network Access Layer

Concerned with the exchange of data between an end system and the network to which it's attached

Software used depends on type of network

Circuit switching

Packet switching (e.g., X.25)

LANs (e.g., Ethernet)

Others


TCP/IP Internet Layer

Uses internet protocol (IP)

Provides routing functions to allow data to traverse multiple interconnected networks

Implemented in end systems and routers


Transport Layer

Commonly uses transmission control protocol (tcp)

Provides reliability during data exchange

Completeness

Order


TCP/IP Application Layer

Logic supports user applications

Uses separate modules that are peculiar to each different type of application

Categories of Noise

Thermal Noise

Intermodulation noise

Crosstalk

Impulse Noise

Thermal Noise

Thermal noise due to agitation of electrons

Present in all electronic devices and transmission media

Cannot be eliminated

Function of temperature

Particularly significant for satellite communication

Types of Antennas

Isotropic antenna (idealized)

Radiates power equally in all directions

Dipole antennas

Half-wave dipole antenna (or Hertz antenna)

Quarter-wave vertical antenna (or Marconi antenna)

Parabolic Reflective Antenna

Differences between LANs and WANs

Scope of a LAN is smaller

LAN interconnects devices within a single building or cluster of buildings

LAN usually owned by organization that owns the attached devices

For WANs, most of network assets are not owned by same organization

Internal data rate of LAN is much greater

Characteristics of LANs

Like WAN, LAN interconnects a variety of devices and provides a means for information exchange among them

Traditional LANs

Provide data rates of 1 to 20 Mbps

High-speed LANS

Provide data rates of 100 Mbps to 1 Gbps

Characteristics of WANs

Covers large geographical areas

Circuits provided by a common carrier

Consists of interconnected switching nodes

Traditional WANs provide modest capacity

64000 bps common

Business subscribers using T-1 service – 1.544
Mbps common

Higher-speed WANs use optical fiber and transmission technique known as asynchronous transfer mode (ATM)

10s and 100s of Mbps common

Types of Communication Networks

Traditional

Traditional local area network (LAN)

Traditional wide area network (WAN)

Higher-speed

High-speed local area network (LAN)

Metropolitan area network (MAN)

High-speed wide area network (WAN)

Time-Domain Concepts

-
Analog signal - signal intensity varies in a smooth fashion over time

No breaks or discontinuities in the signal

- Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level

- Periodic signal - analog or digital signal pattern that repeats over time

s(t +T ) = s(t ) -¥<>

where T is the period of the signal

- Aperiodic signal - analog or digital signal pattern that doesn't repeat over time

- Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts

- Frequency (f )

Rate, in cycles per second, or Hertz (Hz) at which

the signal repeats

- Period (T ) - amount of time it takes for one repetition of the signal

T = 1/f

- Phase (f) - measure of the relative position in time within a single period of a signal

- Wavelength (l) - distance occupied by a single cycle of the signal

Or, the distance between two points of corresponding phase of two consecutive cycles

Transmission Fundamentals, Analog and Digital Data, Channel Capacity, Multiplexing

1         Transmission Fundamentals,

First thing we will examine is the description of radio signals or the electromagnetic signal.

What is radio signal?

It is a function of time and frequency

This means there is a signal and this signal changes with frequency and time.

 

There is analog and digital signal.

 

Analog signal: no break or discontinuity, signal varies in a smooth fashion

Digital signal: signal intensity maintains a constant level for some period, and then changes to another constant level. Imagine 1 and 0 s.

 

Periodic signal: analog or digital signal pattern that repeats over time.

Aperiodic signal: doesn’t repeat over time

 

Peak amplitude: maximum value or strength of the signal

Frequency: rate, cycles per second, Hertz (Hz)

 

Period: amount of time it takes for one repetition of the signal

T=1/f

 

Phase: measure of the relative position in time within a single period of a signal.

 

Wavelength: distance occupied by a single cycle of the signal.

 

Drawings and mathlab examples:

 

t=0:0.01:1;

x=2*pi*t+0;

plot(t,sin(x)), grid on

>>  t=0:0.01:1;

x=2*pi*t+0;

plot(t,2*sin(x)), grid on

>>  t=0:0.01:1;

x=2*pi*2*t+0;

plot(t,2*sin(x)), grid on

>>   t=0:0.01:1;

x=2*pi*0.5*t+0;

plot(t,2*sin(x)), grid on

>>   t=0:0.01:4;

x=2*pi*0.25*t+0;

plot(t,sin(x)), grid on

>> t=0:0.01:4;

x=2*pi*0.25*t+90;

plot(t,sin(x)), grid on

 

 

 

 

1.2         Analog and Digital Data,

Analog: video, audio

Digital: text, integers

 

Analog signal: coninuously varying electromgnetic wave, can propogate analog and digital data

 

Digital signal: a sequence of voltage pulses, cheaper than analog signaling, less susceptiple to noise, suffer from attenuation..

 

Digital signals can propagate analog and digital data

 

Analog transmission---attenuation limits length of transmission link, amplifiers increase ranges..analog data can tolerate distortion, but digital data intruduces errors...

 

Digital transmission---attenuation endangers integrity of data, repeaters achieve greater distance, repeaters recover the signal and transmit

 

1.3         Channel Capacity,

the maximum data rate transmitted over a communication path, or channel.

 

Concepts:

Data rate: rate (bits per second)

Bandwidth: bandwidth of the transmitted signal constrained by the transmitter and the nature of the transmission medium. (hertz)

Noise:

Error rate:

 

1.4         Transmission media

Guided: wired—copper, fiber, coaxiel cables

unguided media---wireless transmission, antennas, directional, omnidirectional

 

 

 

 

 

 

 

 

 

1.5         Multiplexing

Carrying multiple signals on a single medium.

More efficient use of transmission medium

FDM –frequency-division multiplexing

TDM—time-division multiplexing

Protocols and the TCP/IP Protocol Suite

Protocol architecture

Overview of TCP/IP

Open systems interconnection (OSI) reference model

Internetworking

Communication Networks

Comparison of basic communication network technologies

- Circuit switching

- Packet switching

- Frame relay

- ATM

Transmission Fundamentals

Basic overview of transmission topics

Data communications concepts

- Includes techniques of analog and digital data transmission

Channel capacity

Transmission media

Multiplexing

Limitations and Difficulties of Wireless Technologies

Wireless is convenient and less expensive

Limitations and political and technical difficulties inhibit wireless technologies

Lack of an industry-wide standard

Device limitations

E.g., small LCD on a mobile telephone can only

displaying a few lines of text

E.g., browsers of most mobile wireless devices use

wireless markup language (WML) instead of HTML

Background

Provides preview and context for rest of

book

Covers basic topics

Data Communications

TCP/IP

Broadband Wireless Technology

Higher data rates obtainable with broadband wireless technology

- Graphics, video, audio

Shares same advantages of all wireless services: convenience and reduced cost

-  Service can be deployed faster than fixed service

-  No cost of cable plant

-  Service is mobile, deployed almost anywhere

Wireless Comes of Age

Guglielmo Marconi invented the wireless telegraph in 1896

Communication by encoding alphanumeric characters in analog signal

Sent telegraphic signals across the Atlantic Ocean

Communications satellites launched in 1960s

Advances in wireless technology

Radio, television, mobile telephone,communication satellites

More recently

Satellite communications, wireless networking,cellular technology

Breaking down the issues in Mobile Computing

• Technical Challenges of Mobile Computing
– portability,
– mobility,
– wireless communications
– system issues

•Traveling people and their needs with respect to applications and technologies
– application perspective: which applications are of benefit?
– Which applications can be implemented and used effectively regarding the often narrow bandwidth, limited computing power, small memory and battery capacity and other resources of the terminals?


•Wireless Networks
– to main types: terrestrial cellular and satellite networks – determine to a large extent application architectures and usable protocols
– communication autonomy is an important feature of the terminals in these networks: thus the terminals are not always reachable for variety of reasons

•Data Management issues
– where to keep the data, when to transmit it, whether to use caching and where in the network, how to optimize data placement, pull/push approach, transactional services, location-dependent queries etc
– these questions are closely related with the
networking issues and properties of the terminals

Nomadic or Mobile Computing

Nomadic computing is concerned with the connection of portable (mobile) computers, and with the migration of software, from a home platform to a remote one;

– It is now recognized that access to computing and communications is necessary not only from one's "home base," but also while one is in transit and when one reaches one's destination.

– The goal of "transparent virtual networking" or "nomadic" computing is precisely to permit users and programs to be as effective as possible in this environment of uncertain connectivity, without changes to the manner in which they operate.

– Using diverse phones from everywhere in the world is not activity that could be called nomadic computing (because there is no computing (data processing) involved)

– Dragging around a laptop and working with it without being able to set up a connection to the “home base” through a computer network is neither nomadic
computing in a strong sense; one must be able to communicate with “home base” and people in other organizations

– Does nomadic computing require some devices to be dragged around by the people?
(not necessarily, an infrastructure with suitable access devices could be offered to traveling people - in the same manner as telephones are offered in hotels, airports, etc.)

– Another important development are the advances in computer networking infrastructure that make global connectivity possible.

– One notable development is the Internet as a global networking infrastructure, but in this context especially the wireless technologies are very important.

• The role of wireless technologies in mobile computing:

– wired portable devices can be connected to the network infrastructure only in certain locations for a certain period of time => communication activity of a
nomad is spatially and temporally restricted – wireless portable devices, especially those operating with radio transmitter/receiver avoid the above problem to a great extent


• nomadic or mobile computing consists of: traveling people using
• portable wireless computing and communication devices connected to
• computer network infrastructure supporting global connectivity and remote computing

First & Second Generation Mobile Phones

Mobile phones were born when a number of mobile radio users decided to make mobile phone technology more popular. Mobile telephones were firstly installed in vehicles on a permanent basis, later some versions appeared which were named transportables, could also be carried. Motorola developed a two way radio in a rucksack, the walkie-talkie, and this was widely regarded as one of the first mobiles.

First Generation Phones

First mobile phones are called as first generation (1G) mobile phones. Mobile phones started to gain popularity with the introduction of cellphones that were based on cellular networks.

Mobile phones were originally much bigger than current ones, they were designed for installation in vehicles only, which is called the car phone. These big phones were later converted for use as transportable phones the size of a small.
This system used a single large transmitter on top of a tall building and had a single channel, used for both sending and receiving. To talk, the user had to push a button that enabled the transmitter and disabled the receiver. This system is known as push – to - talk systems.

Second Generation Phones

Second generation, is also called 2G. Second generation telephone systems were different because of their use of digital circuit switched transmission. 2G is the introduction of advanced & quick telephone to network signals. The introduction of 2-G systems saw telephones move from historic 1G telephones to small hand held items, which were much more portable. This change was made useful improvements in technology for example more advanced batteries and energy efficient electronics.

The second generation mobile telephones had several advantages over 1G items. These included SMS messaging, which initially became possible on GSM networks & eventually on all digital networks. SMS text messaging soon became the communication method of choice & the general public now prefer sending messages to placing voice calls.
The first generation of mobile phones was analog; the second generation was digital. The voice signal picked up by the microphone is digitized and compressed.