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Multiple-Input and Multiple-Output (MIMO) and 802.11n(Ch. 15 of Textbook)Instructor: Dr. Wei (Lisa) LiComputer Science, GSU[email protected]
--- A method for multiplying the capacity of a radio link using multipletransmit and receive antennasto exploit multipath propagationMIMO
An Overview•802.11a/b/g devices send a single spatial stream over a single antenna–If signals are reflected, there is a problem•To further improve throughput–Transmit two or more spatial streams, and employ multiple receive antennas and advanced signal processing to recover the multiple transmitted data streams–Actually uses the reflected signals to increase the range and reduce “dead spots”3
Antenna BasicsIt was always very hard to introduce antenna techniques until iPhone 4 was released…
Introduction to Antennas•An antenna is an electrical conductor or system of conductors–Transmission- radiates electromagnetic energy into space (convert the energy into EM waves)–Reception- collects electromagnetic energy from space•The physical size of the radiating element is proportional to the wavelength –The higher the frequency, the shorter the wavelength, and thus, the smaller the antenna size5
Introduction to Antennas (Cont’d)•In two-way communications, –the same antenna can be used for transmission and reception–But not necessary: e.g., cellular base stations