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What is software-defined radio (SDR) definition?
A typical voice SDR transmitter, such as might be used in mobile two-way radio or cellular telephone communication, consists of the following stages.? Items with asterisks represent computer-controlled circuits whose parameters are determined by the programming (software).- Microphone
- Audio amplifier
- Analog-to-digital converter (ADC) that converts the voice audio to ASCII data
- Modulator that impresses the ASCII intelligence onto a radio-frequency (RF) carrier
- Series of amplifiers that boosts the RF carrier to the power level necessary for transmission
- Transmitting antenna
A typical receiver designed to intercept the above-described voice SDR signal would employ the following stages, essentially reversing the transmitter's action. Again, items followed by asterisks represent programmable circuits.- Receiving antenna
- Superheterodyne system that boosts incoming RF signal strength and converts it to a constant frequency
- Demodulator that separates the ASCII intelligence from the RF carrier
- Digital-to-analog converter (DAC) that generates a voice waveform from the ASCII data
- Audio amplifier
- Speaker, earphone, or headset
The most significant asset of SDR is versatility. Wireless systems employ protocols that vary from one service to another. Even in the same type of service, for example wireless fax, the protocol often differs from country to country. A single SDR set with an all-inclusive software repertoire can be used in any mode,anywhere in the world. Changing the service type, the mode, and/or the modulation protocol involves simply selecting and launching the requisite computer program, and making sure the batteries are adequately charged if portable operation is contemplated.
The ultimate goal of SDR engineers is to provide a single radio transceiver capable of playing the roles of cordless telephone, cell phone, wireless fax,wireless e-mail system, pager, wireless videoconferencing unit, wireless Web browser, Global Positioning System (GPS) unit, and other functions still in the realm of science fiction, operable from any location on the surface of the earth, and perhaps in space as well.
What is cyber hijacking?
Hijacking is a type of network security attack in which the attacker takes control of a communication - just as an airplane hijacker takes control of a flight - between two entities and masquerades as one of them. In one type of hijacking (also known as a man in the middle attack), the perpetrator takes control of an established connection while it is in progress. The attacker intercepts messages in a public key exchange and then retransmits them, substituting their own public key for the requested one, so that the two original parties still appear to be communicating with each other directly. The attacker uses a program that appears to be the server to the client and appears to be the client to the server. This attack may be used simply to gain access to the messages, or to enable the attacker to modify them before retransmitting them.
Information from Wikipedia and TechTarget.com
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