P.B.R. VISWODAYA INSTITUTE OF SCIENCE AND TECHNOLOGY
WIRELESS NETWORKS
THIS TOPIC IS PRESENTED BY SECOND YEAR M.C.ASTUDENTS
B.L.PRIYANKA.
K.SUJANA.
WIRELESS NETWORKS-BLUETOOTH TECHNOLOGY
ABSTRACT
Now a days, wireless networks plays a very important role in our society. Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires. Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, such as radio waves, for the carrier and this implementation usually takes place at the physical level or "layer" of the network.with the help of these wireless networks We can have the convinience .
We can have the economical freedom.Here the problem tracing is also very easy as we have no physical relation in between the systems.Now in these days we can have the wireless technology in the mobiles very much.in olden days we can have the communication through the long wires.If any connection is in failure then communication is not possible.But now it’s not at all a problem.We can easily have the networking between the cells.We can also have the wireless technology developped in between the systems.
Here the bluetooth technology is used now a days very frequently and through the wireless network bluetooth technology can be possible very easily .
1. INTRODUCTION:
The idea that resulted in the Bluetooth technology was born in 1994. Ericsson Mobile communications initiated a study to investigate the feasibility of a low-power, low-cost radio interface between Mobile Phones
And their accessories. The aim was to eliminate cables between Mobile Phones and PC cards, headsets and Desktop devices etc.
In February 1998, five companies,Ericssion, Nokia, IBM, Toshiba and Intel formed a Special Interest Group (SIG). The group contained the Mix of business areas –two market leaders in Mobile Telephony, to market leaders in Laptop computing and a market leader in core digital – signal-processor technology. It’s important to surround yourself with the right kind of people. That is a fact that even old Herald knew.
In this Electronic era, the devices used byus arerapidly growing. We are using several wires to supply power, to connect user interfaces, to connect each other. There will be no problem until we shift them from one place to another. Bluetooth wireless technology – the technology that propels you into a new dimension in wireless connectivity.
Why the name Bluetooth is given to this technology? The Answer is “Herald Bluetooth was the 10 th century Viking King who gave name to our technology. Herald Bluetooth was king of Denmark in the 10th century. He unified Denmark and part of Norway into a single kingdom, and then introduced Christianity into Denmark. But he was killed in 986during battle with his son. So his name was choosen for this technology
2. NEED FOR BLUETOOTH:
There are already a couple of ways to get around wires. They are
- Beams of light in the infrared spectrum.
- Cable synchronization.
INFRARED:
It is used to connect some computers with peripheral devices. For most of these computer and entertainment purposes, infrared is used in a digital mode. The signal is pulsed on and off very quickly to send data from one point to another. Infrared communicationare fairly reliable and don’t cost very much to build into a device. Reliable means interference between devices is uncommon because infrared transmitters and receivers have to be lined up with each other and we can make sure a message goes only to intended recipient, even in a room full of infrared receivers.
Drawbacks with infrared communications are
1. Infrared is a “line of sight “technology. For example we have to point the remote control at theTELEVISION or DVD player to make things happen.
2. Infrared is a “One –To –One” technology. For example we can send data from our PC to out LAPTOP, but not to both LAPTOP and PDA at the same time.
CABLE SYNCHRONIZATION:
In synchronization, we attach PDA to out computer (usually with a cable),
Press a button and make sure that the data on PDA and the data on the computer match. Its technique that makes the PDA a valuable tool for many people but synchronizing the PDA with the PC and making sure we have the correct cable or cradle to connect these two can be real hassle.
Bluetooth intended to get around the problems that come with both Infrared and Cable synchronizing system.
INFRARED CABLE
COMMUNICATION SYNCHRONIZATION
From the users’ point of view, there are 3 important features in Bluetooth.
- It is wireless.
- It is inexpensive. Manufacturers think that it will add about $20 per device.
3. Bluetooth don’t require doing any thing special to make it work. The devices find one another and strike up a conversation.
When any two devices want to talk to each other, they have to agree on a number of points before the conversation begins.
- The first point of agreement is physical, will they talk over wires or through some form of wireless signal.
- The second point is type of communication, i.e. information can be sent one bit at a time in a scheme called Serial Communication or in group of bits in scheme called Parallel Communication. PC uses both serial and parallel communications to talk to different devices. Modems, mice, Keyboards are use serial links, while printers tend to use parallel links.
All parties in a electronic conversation need to know what the bits mean and whether the message they received is same of message that was sent. In most cases this means developing a language of commands and responses known as protocol. Some products have standard protocol used by virtually all companies so that the commands for one product will tend to have the same effect on another. Modems fall into this category. Other product types each speaks in their own language, which means commands intended for one specific product will seem gibberish if received by another. Printers have multiple standards like PCC and POSTSCRPT.
4.HOW BLUETOOTH WORKS?
4.1. AVOIDING INTERFERENCE:
Bluetooth devices sent out very week signal of 1 milli watt. By comparison the most powerful cell phones can transmit a signal of 3 watts. The low power limit range of Bluetooth device to about 10 meters, cutting the chances of interferences.
With many different Bluetooth devices in a room, they wont interfere with one another. Why because, it is unlikely that several devices will beon the same frequency at the same time because Bluetooth uses a technique called Frequency Hopping Spread-Spectrum (FHSS)
In this technique a device will use 79 individual randomly chosen frequencies with in a designated range, changing from one to another on a regular basis. Transmitters changes frequencies 1600 times every second. Since every Bluetooth transmitter uses FHSS, it is unlikely that 2 transmitters will be on the same frequency at the same time. This same technique minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices since any interference on a particular frequency will lose only a tiny fraction of a second.
FHSS is designed to tradeoff bandwidth efficiently for reliability, integrity and security. FHSS uses a narrow band carrier that changes frequency in a pattern known to both transmitter and receiver.
4.2.BLUETOOTH NETWORKS :
Two possible networks exist in Bluetooth. They are:
1. Pico net.
2. Scatter net.
When we bring Bluetooth radios with in range of each other, an electronic conversation will take place to determine whether they have data to share or whether one need to control one another. Once the conversation has started the devices form a network i.e. Pico net. One unit becomes a MASTER and other as SLAVE. The master controls all the traffic in the Pico net. Bluetooth radios in a Pico net frequency-hop together.
Scatter nets occur when multiple masters exists in range of each other. A master radio may also be a slave radio on another Pico net. Each Pico net is hopping with a different sequence sharing the same 2.4 GHz band. Because different hopping sequences, there is very little chance that any master will hit a channel at the same time as another master.xx
PICONET
SCATTERN
4.3. BLUETOOTH RADIO STATES:
Radios in a Pico net can be in one of six states.
- OFF – It means initial state. There is no connection for LMP.
- STANDBY – Radio is waiting to join in a Piconet.
- INQUIRE – Radio seeking other radios to connect.
- PAGE – Master radio asking to connect to a specific radio.
- CONNECTED – Radio active on a Piconet as a master, slave or simultaneously.
- PARK/HOLD – When there is no work for a radio if states its position and waits for messages. This state is called Park state. In this state it consumes least power.
1 2
3 3
7
4
4
6
5
Frequency hops in the range 2400 – 2438.5 MHz at the rate of 1600 times per second
1,2,3 – SCO links – time slots were reserved
4,5,6,7 – ACL links – remainin
ARCHITECTURE OF BLUETOOTH PACKET
ACCESS CODE / POCKET HEADER / PAYLOAD72 BITS 54 BITS 0 – 2745 BITS
Using access code slave compares data packets access code by comparing its internal code, otherwise it rejects it.
7. BLUETOOTH USAGE MODELS : Usage models are accompanied by a profile. Profile defines the protocols and protocol features supporting a particular usage model.
7.1. FILE TRANSFER MODEL
This usage model offers the ability to transfer data objects from one device to another. Object types includes .x1s, .ppt, .wav,.jpg and .doc files, entire folders or directories or streaming media formats. It also offers a possibility to browse the contents of the folders on a remote device.
7.2. LAN ACCESS MODEL:
In this model multiple data terminals use a LAN Access Point (LAP) as a wireless connection to a LAN. Once connected, the DT’s operate as if it they were connected to the LAN via dial-up networking. The DT can access all of the services provided by the LAN.
7.3. SYNCHRONIZATION MODEL
It provides a device-to-device (phone, PDA, computer etc) synchronization of the PIM (personal information Mgt) information, typically phonebook, calendar, message and note information. Synchronization requires business card, calendar and task information to betransferred and processed by computers, cellular phones and PDA utilizes a common protocol and format.
8. CONCLUSION: