RFWireless Communication Basics
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This page covers wireless basics, wireless network, wireless sensors, wireless physical layer, propagation modes, terms, etc. It mentions the difference between wired and wireless mediums, wireless tutorials, and the advantages and disadvantages of wireless communication.
Introduction
Information that needs to be transmitted through a wireless medium is converted to a suitable form by a transmitter module. At the receiver, the information is retrieved from this converted form. This information can be voice, data, video, image, and so on.
The history of wireless starts with Bell, who, in 1880, along with his colleague Charles Sumner Tainter, invented the photophone. This system demonstrated by Bell had limitations. Wireless came into public use in 1896 when Marconi demonstrated wireless telegraphy. This became a reality due to Maxwell’s prediction of the existence of electromagnetic waves.
How a Wireless System Works
Electromagnetic waves, radio frequency waves, or infrared waves are used as a transport medium in a wireless system. It uses wireless antennas or sensors to transmit/receive the EM waves. An EM signal is a function of time, but it can also be expressed as a function of frequency. This frequency domain view is crucial for analyzing 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 and received from space using an 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. Different antennas are designed to transmit and receive different frequency bands.
Let’s understand the constituents of a wireless system. The basic components in the wireless network are the Transmitter, Receiver, and Channel. Transmitter and Receiver combined are often called a Transceiver. The Channel is the medium through which information in the form of EM waves passes to reach the other end of the system. Based on the channel, there are limitations for different technologies to work efficiently.
As mentioned above, Bell’s demonstration assumed a good atmosphere. We see live examples of wireless systems with all living creatures, in hearing aids which allow listening to music without any wires, mobile phones, etc.
There are various types of sensors. Wireless sensors include NFC sensors, RFID, Bluetooth, and Zigbee-based sensors.
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: time-variant and time-invariant channels, based on whether the transmitter and receiver are fixed or mobile, respectively. There are slow and fast fading channels based on the speed of the Transmitter and Receiver.
Applications
Following are the applications of wireless communication:
- Telegraph
- Home automation
- Telephone or Mobile
- AM/FM Radio
- Television
- Camera
- Space exploration
- Wireless internet
- Remote control
- Wireless navigation systems
- Medical
- 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
The wireless physical layer refers to the layer that protects data to reliably reach from the transmitter to the receiver in the presence of a noisy channel environment.
The Physical layer transmitter part uses scrambler, Interleaver, FEC module, and modulator modules. The receiver part uses the reverse of the above-said modules. In addition, the receiver uses front-end synchronization modules such as time and frequency, as well as channel equalization.
Wireless Propagation Modes
There are three wireless propagation modes: Ground wave propagation, Sky wave propagation, and Line of Sight (LOS) propagation.
Difference between Wired and Wireless Mediums
| Specifications | Wired network | Wireless network |
|---|---|---|
| Speed of operation | Higher | lower compared to wired networks, but advanced wireless technologies such as LTE, LTE-A, and WLAN-11ad will make it possible to achieve speeds on par with wired networks |
| System Bandwidth | High | Low, as the Frequency Spectrum is a very scarce 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 radio waves 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 | 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 the high value of jitter and delay in connection setup |
| Reliability | High compared to its wireless counterpart, as manufactured cables have higher performance due to the existence of wired technology for many years. | Reasonably high. This is because the failure of a 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.
