What is wireless? | Wireless network, tutorials, sensors, terms
This page covers wireless basics, wireless network, wireless sensors, wireless physical layer, propagation modes, terms etc. It mentions difference between wired and wireless medium, wireless tutorials and advantages and disadvantages of wireless communication.
Information which needs to be transmitted through wireless medium are converted to the suitable form as per medium using transmitter module. At the receiver, the information is retrieved back from this converted form. Information can be voice, data, video, image and so on.
History of wireless starts with Bell who in 1880 along with his colleague Charles Sumner Tainter invented photo phone. The system demonstrated by Bell had limitations. After this wireless came into public use in 1896 when Marconi demonstrated wireless telegraph. This came to reality due to Maxwell's prediction of existence of electromagnetic waves.
How wireless system works?
Electromagnetic waves or radio frequency waves or infrared waves are used as transport medium in wireless system. It uses wireless antennas or sensors in order to transmit/receive the EM waves.
An EM signal is a function of time, but it can be expressed as a function of frequency also. This frequency domain view is very important to analyze the frequency components of the signal. Viewed as a function of time, an EM signal can be either analog or digital. This EM signal can be transmitted to space and received from space using Antenna.
An antenna can be defined as an electrical conductor or system of conductors used either for radiating EM energy into space or for collecting EM energy from space. There are different antennas designed to transmit and receive different frequency bands. Let us understand contituents of a wireless system.
The basic components in the wireless network are Transmitter, Receiver and channel. Transmitter and Receiver combined are often called as Transceiver. Channel is the medium through which information in the form of EM waves pass through to reach the other end of the system. Based on channel there are limitations for different technologies to work efficiently. As mentioned above when Bell demonstrated it had assumed good atmosphere. We see live example of wireless system with all the living creatures in hearing aids which allows listening of music without any wires, mobile phones etc.
Refer Wireless System Overview >> which explains wireless system block diagram, types of wireless network, types of topologies, speeds supported by wireless networks and so on. There are various types of sensors. Wireless sensors include NFC sensor, RFID, bluetooth and zigbee based sensors. Refer Wireless Sensor >> for more information.
Wireless channel models
There are various wireless channel models based on transmitter and receiver systems location, distance and mobility. Due to this different technologies have been designed to exchange information efficiently between transmitter and receiver devices. Channels are of two types viz. time variant and time invariant channels based on trasnmitter and receiver is fixed and mobile respectively. There are slow and fast fading channels based on speed of Transmitter and Receiver.
Following are the applications of wireless communication.
1. Telegraph 2. Home automation 3. Telephone or Mobile 4. AM/FM Radio 5. Television 6. Camera 7. Space exploration 8. Wireless internet 9. Remote control 10. Wireless navigation systems 11. Medical 12. Wireless inventory systems
Wireless Standards or technologies
Following technologies or standards are based on wireless communication.
Cellular GSM TD-SCDMA wimax LTE UMTS GPRS CDMA SCADA WLAN 802.11ac 802.11ad GPS Zigbee z-wave Bluetooth UWB IoT T&M satellite Antenna RADAR RFID
Wireless Service Providers throughout the world
AT&T | Nextel | Verizon wireless| ViryaNet | India Airtel | India Aircel | India Reliance | India Tata Indicom | India Tikona Digital | India Vodaphone
UK O2 | UK Broadband | UK Vodafone | USA AT&T Mobility | USA Clearwire | USA Sprint | USA T-Mobile USA | USA US Cellular | USA Verizon Wireless
Wireless Physical Layer
Wireless physical layer refers to the layer which protects data to reach reliably from transmitter to the receiver in the presence of noisy channel environment. The Physical layer transmitter part uses scrambler, Interleaver, FEC module and modulator modules. The receiver part uses reverse of the above said modules. In addition, receiver uses front end synchronization modules such as time and frequency as well as channel equalization. Refer Wireless Physical Layer >> for more information.
Wireless Propagation Modes
There are three wireless propagation modes viz. Ground wave propagation, Sky wave propagation and Line of Sight (LOS) propagation.
Refer Wireless Propagation Modes >> for more information.
Difference between Wired and Wireless Medium
Following table mentions difference between wired and wireless mediums.
|Specifications||Wired network||Wireless network|
|Speed of operation||Higher||lower compare to wired networks, But advanced wireless technologies such as LTE, LTE-A and WLAN-11ad will make it possible to achieve speed par equivalent to wired network|
|System Bandwidth||High||Low, as Frequency Spectrum is very scarse resource|
|Cost||Less as cables are not expensive||More as wireless subscriber stations, wireless routers, wireless access points and adapters are expensive|
|Installation||Wired network installation is cumbersome and it requires more time||Wireless network installation is easy and it requires less time|
|Mobility||Limited, as it operates in the area covered by connected systems with the wired network||Not limited, as it operates in the entire wireless network coverage|
|Transmission medium||copper wires, optical fiber cables, ethernet||EM waves or radiowaves or infrared|
|Network coverage extension||requires hubs and switches for network coverage limit extension||More area is covered by wireless base stations which are connected to one another.|
|Applications||LAN (Ethernet), MAN||WLAN, WPAN(Zigbee, bluetooth), Infrared, Cellular(GSM,CDMA, LTE)|
|Channel Interference and signal power loss||Interference is less as one wired network will not affect the other||Interference is higher due to obstacles between wireless transmitter and receiver e.g. weather conditions, reflection from walls, etc.|
|QoS (Quality of Service)||Better||Poor due to high value of jitter and delay in connection setup|
|Reliability||High compare to wireless counterpart, as manufactured cables have higher performance due to existence of wired technology since years.||Reasonably high, This is due to failure of router will affect the entire network.|
Advantages and Disadvantages of Wireless Communication
Some of the benefits of wireless communication are speed, cost, durability, flexibility,
wireless nature etc.
Some of the drawbacks of wireless communication are security, compatibility, interference with other wireless carriers, power consumption in portable devices etc.
Refer advantages and disadvantages of wireless >> for more information.