wireless. In this case, a radio signal is used to encode the information exchanged between the communicating devices. Many types of modulation techniques are used to send information over a wireless channel and there is lot of innovation in this field with new techniques appearing every year. While most wireless networks rely on radio signals, some use a laser that sends light pulses to a remote detector. These optical5Computer Networking : Principles, Protocols and Practice, Releasetechniquesallowtocreatepoint-to-pointlinkswhileradio-basedtechniques,dependingonthedirectionality of the antennas, can be used to build networks containing devices spread over a small geographical area.