Tagged: wireless communication

Bluetooth Technology

Bluetooth is a electrical device that uses wireless technology on 2.5 GHz ISM (license free) frequency band.It can be used in mobile phones, headsets,portable computers to exchange data to each other without wire.Due to its low cost,low size,low power,radio technology,it becomes popular.Almost,every mobile phone provide Bluetooth technology.

Advantage of Bluetooth

1. Operates in the 2.4GHz frequency band without a license for wireless communication.

2. Real-time data transfer possible for short distance.

3. It can transmite data through obstacles like wall.

4. It supports both point-to-point wireless connections between mobile phones

and personalcomputers, as well as point-to-multipoint connections to any other

wireless networks.

5. Bluetooth is a portable devices

6. Compared with other systems operating in the same frequency band,

the Bluetooth radio typically hops faster and uses shorter packets.

7. Bluetooth is actually inexpensive.

8. Bluetooth is standardized wireless, meaning that a high level of compatibility

that means it will connect devices to each other, even if they aren’t the same model.

9. Low energy consumption As a result of Bluetooth using low power signals,

the technology requiresvery little energy and will use less battery or electrical

power as a result.

10.The standard for Bluetooth will allow compatible devices to share data and voice communications.

Bluetooth Application

1. Wireless networking between laptops and desktop computers, or desktops that are in a confined
space and little bandwidth is needed.

2. Peripherals such as mice, keyboards, and printers.

3.Most Cell phones uses Bluetooth technology .They are able to connect to computers, PDAs
and various other devices.

4. The transfer of files, images and MP3, between mobile phones.

5. Certain MP3 players and digital cameras to transfer files to and from computers.

6. Bluetooth technology headsets for smart phones and cell phones.

7. Data logging equipment that transmits data to a computer via Bluetooth technology.

Security

If you want to connect two device through Bluetooth ,’pairing process’ is requiered.Through pairing
two or more Bluetooth devices that recognize each other by the profiles they share.
This is one of the most basic levels of security for Bluetooth devices.

Bluetooth use an encryption algorithm, which is completely and entirely secure. Once the devices pair with each other, they too become entirely secure.

Communication will be successfully if and only if thay are paired.That is why Bluetooth technology is considered to be secure.

Still there is secirity threate because some hackers have developed ways to get around this level of basic security.so, you must have software to prevent hackers from getting in.

Wireless communication : Infrared Technology

Infrared wireless tecnology is the use of wireless technology in devices or systems that allow data transfer through infrared (IR) radiation.In infrared communication , an LED transmits the infrared signal as bursts of non-visible light. At the receiving end a photodiode or photoreceptor detects and captures the light pulses,and retrieve the information they contain.

IR wireless is used for short- and medium-range communications and control.It is used in computer hardware such as in wireless mouse, keyboard,Floppy disk drives,Printers.It is also used in Car locking systems,Emergency response systems, Headphones,Home security systems ,Robot control systems and more.

Infrared technology offers several important advantages as well as disadvantages as a form of wireless communication.

IR Advantages:

1. Low power requirements: ideal for laptops, telephones
2. Low circuitry costs: $2-$5 for the entire coding/decoding circuitry
3. Simple circuitry: no special hardware is required.
4. Higher security: directionality of the beam helps ensure that data isn’t   leaked or spilled to nearby devices as it’s transmitted
5. Portable

IR Disadvantages:

1. Line of sight: transmitters and receivers must be almost directly aligned to
communicate
2. Blocked by common materials: people, walls, plants, etc. can block transmission
3. Short range: transmission become slow on longer distances
4. Light, weather sensitive: direct sunlight, rain, fog, dust, pollution can affect
transmission
5. Speed: transmission rate is lower than typical wired transmission.

Health Risks

There are no confirmed health risks or scientific dangers from infrared or radio frequency but in case of point-to-point lasers which can cause burns or blindness and also continuous microwave exposure which has been linked to cancer and leukemia.

Security

Electromagnetic frequencies currently have less protection and can be freely intercepted by motivated individuals. But,security issue varies by the type of wireless transmission method .Infrared data transmission is more difficult to intercept when compared to radio frequency. Radio frequency can penetrate walls, making it much easier to transmit a message, but also more susceptible to tapping.

Global System for Mobile Communications(GSM)

Global system for mobile communication (GSM) is the Pan European standard for mobile communications defined by the European Telecommunication Standards Institute (ETSI) and published in 1990.

GSM is a digital mobile telephony system that is widely used in world. GSM uses a variation of time division multiple access(TDMA).It is most widely used in three digital wireless telephony technologies(TDMA,GSM and CDMA). GSM digitizes and compresses data and sends it to a channel with two other streams of user data, each in its own time slot. It works on either the 900 MHz or 1800 MHz frequency band.

GSM, along with other technologies, is part of the evolution of wireless mobile telecommunications that includes High-Speed Circuit-Switched Data (HCSD), General Packet Radio System (GPRS), Enhanced Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service (UMTS).

Services provided by GSM

Using the ITU-T definitions, telecommunication services can be divided into bearer services, teleservices, and supplementary services. The most basic teleservice supported by GSM is telephony in which speech is digitally encoded and transmitted through the GSM network as a digital stream.

By Using GSM technologies telephony, emergency services, facsimile, SMS and data services can be provided through wireless communications. It can also send messages such as traffic updates or news updates. Messages can also be stored in the SIM card for later retrieval.

It also provide bearer and teleservices service such as call forward when the mobile subscriber is unreachable by the network, and call barring of outgoing or incoming calls, for example when roaming in another country and other services , such as caller identification, call waiting, multi-party conversations.

GSM users can send and receive data, at rates up to 9600 bps, to users on POTS (Plain Old Telephone Service), ISDN, Packet Switched Public Data Networks, and Circuit Switched Public Data Networks using a various of access methods and protocols, such as X.32. As GSM is a digital network, a modem is not required between the user and GSM network.But an audio modem is required inside the GSM network to interwork with POTS.

GSM security

It provide moderate level of security. The system was developed to authenticate the subscriber using a pre-shared key and challenge-response. Communications between the subscriber and the base station can be encrypted. The user with a longer authentication key to give greater security.

GSM uses several cryptographic algorithms for security such as A5/1 and A5/2 stream ciphers ,that are used for ensuring over-the-air voice privacy.A large security advantage of GSM over earlier systems is that the cryptographic key stored on the SIM card is never sent over the wireless interface. Serious weaknesses have been found in both algorithms.

According to GSM World, there are now more than 2 billion GSM mobile phone users in the world. GSM World references China as “the largest single GSM market, with more than 370 million users, followed by Russia with 145 million, India with 83 million and the USA with 78 million users.”

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Code Division Multiple Access(CDMA) Technology

CDMA (Code-Division Multiple Access) is a wireless communication protocols.It is called second-generation (2G) and third-generation (3G) wireless communications.CDMA is a form of wireless multiplexing, in which data can be sent over multiple frequencies simultaneously.In a CDMA system, data is broken into packets.Each of packets is given a unique identifier, so that they can be sent out over multiple frequencies and then re-built in the correct order by the receiver.The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.
pread spe
CDMA uses analog-to-digital conversion (ADC) along with spread spectrum technology. Audio input is first converted into binary elements. The frequency of the transmitted signal is then made compatible with receiver frequency so that it can be intercepted only by a defined receiver. There are trillions of possible frequency-sequencing codes, which enhances privacy and makes cloning difficult.

The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff.It minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes of CDMA supports several times as many signals per unit bandwidth as analog modes. CDMA is compatible with other cellular technologies, that supports nationwide roaming.

The first CDMA standard, also known as CDMAone and still common in cellular telephones in the U.S.It offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and wideband CDMA support data many times faster.

CDMA has been used in many communications systems, including the GSM and in the OmniTRACS satellite system for transportation logistics.

Usage in mobile telephony

CDMA has been implementationed with different termology. The original U.S. standard defined by QUALCOMM was known as IS-95.The ‘IS’ referring to an Interim Standard of the Telecommunications Industry Association (TIA). IS-95 is often referred to as second generation cellular(2G). The QUALCOMM brand name CDMAone may also be used to refer to the 2G CDMA standard.

Various companies use different form of CDMA to provide fixed-line networks using Wireless local loop (WLL) technology. This application of CDMA can be found in most parts of the world.

Wireless communication : AMPS technology

Advance Mobile Phone System (AMPS) is the analog mobile system standard which is introduce in Amarica during 1980s.Now,these days analog system is no longer advance,almost whole world become degital system.

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Technology :

It was a first-genaration technology,using FDMA(Frequency division multiple access) technology.It means that each cell site would transmit on different frequencies, allowing many cell sites to be build near each other.But it had disadvantage that each site did not have much capacity for carrying calls.It has also poor security,but latter it was improved by introducing newer digital TDMA(Time division multiple access).

AMPS Channels :

The frequencies allocated to AMPS by the FCC range between 824 to 849 MHz in reverse channels (mobile to base) and 869 to 894 MHz in forward channels (base to mobile). They are not contiguous blocks because the initial 40 MHz allocation by the FCC was later extended by 10 MHz when the service’s popularity became evident. There are now a total of 416 channels available in each direction, numbered from 1 to 1024 with gaps in the numbering.

Frequency bands :

In that time, there were to be two licensee (networks). Each network is authorized to use 416 channels in the 800 MHz band. Each channel is consists of 2 frequencies. 416 of these are in the 824~849 MHz range for transmissions from mobile stations to the base stations and paired with 416 frequencies in the 869~894 MHz range for transmissions from base stations to the mobile stations. Each cell site will use a subset of these channels, and must use a unique set to avoid interference. This significantly reduces the number of channels available at each site in real-world systems. Each AMPS frequency is 30kHz wide.

The AMPS band was taken from the same 806~890 MHz frequency band which was originally UHF TV channels 70~83. This meant that these UHF channels could not be used for UHF TV transmission as these frequencies were to be used for AMPS transmission.