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In telecommunications, an interference is that which modifies a signal in a disruptive manner, as it travels along a communication channel between its source and receiver. The term is often used to refer to the addition of unwanted signals to a useful signal. Common examples include:
- Electromagnetic interference (EMI)
- Co-channel interference (CCI), also known as crosstalk
- Adjacent-channel interference (ACI)
- Intersymbol interference (ISI)
- Inter-carrier interference (ICI), caused by doppler shift in OFDM modulation (multitone modulation).
- Common-mode interference (CMI)
- Conducted interference
Noise is a form of interference but not all interference is noise.
A solution to interference problems in wireless communication networks is interference alignment, which was crystallized by Syed Ali Jafar at the University of California, Irvine. A specialized application was previously studied by Yitzhak Birk and Tomer Kol for an index coding problem in 1998. For interference management in wireless communication, interference alignment was originally introduced by Mohammad Ali Maddah-Ali, Abolfazl S. Motahari, and Amir Keyvan Khandani, at the University of Waterloo, for communication over wireless X channels. Interference alignment was eventually established as a general principle by Jafar and Viveck R. Cadambe in 2008, when they introduced "a mechanism to align an arbitrarily large number of interferers, leading to the surprising conclusion that wireless networks are not essentially interference limited." This led to the adoption of interference alignment in the design of wireless networks.
My research group crystallized the concept of interference alignment and showed that through interference alignment, it is possible for everyone to access half of the total bandwidth free from interference. Initially this result was shown under a number of idealized assumptions that are typical in theoretical studies. We have since continued to work on peeling off these idealizations one at a time, to bring the theory closer to practice. Along the way we have made numerous discoveries through the lens of interference alignment, which reveal new and powerful signaling schemes.
Syed Jafar revolutionized our understanding of the capacity limits of wireless networks. He demonstrated the astounding result that each user in a wireless network can access half of the spectrum without interference from other users, regardless of how many users are sharing the spectrum. This is a truly remarkable result that has a tremendous impact on both information theory and the design of wireless networks.
- Inter-flow interference
- Intra-flow interference
- Signal-to-interference ratio (SIR)
- Signal-to-noise plus interference (SNIR)
- "2015 National Laureates". Blavatnik Awards for Young Scientists. June 30, 2015. Retrieved 22 September 2019.
- Maddah-Ali, Mohammad Ali; Motahari, S. Abolfazl; Khandani, Amir Keyvan (July 2008). "Communication over MIMO X channels: Interference alignment, decomposition, and performance analysis". IEEE Transactions on Information Theory. 54 (8): 3457–3470.
- Jafar, Syed A. (2010). "Interference Alignment — A New Look at Signal Dimensions in a Communication Network". Foundations and Trends in Communications and Information Theory. 7 (1): 1–134. CiteSeerX 10.1.1.707.6314. doi:10.1561/0100000047.
- "Meet the Scientists: Syed A. Jafar". Armed With Science. United States Department of Defense. August 24, 2015. Retrieved 23 September 2019.