query: What does "IMSI" stand for in IMSI-catcher?
passage: IMSI-catcher
An international mobile subscriber identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking location data of mobile phone users.[1] Essentially a "fake" mobile tower acting between the target mobile phone and the service provider's real towers, it is an example of a man-in-the-middle (MITM) attack. The 3G wireless standard offers some risk mitigation due to mutual authentication required from both the handset and the network.[2] However, sophisticated attacks may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication.[3]
passage: Carrier interferometry
CI was introduced by Steve Shattil, a scientist at Idris Communications, in U.S. Pat. No. 5,955,992, filed February 12, 1998, and in the first of many papers in April, 1999. The concept was inspired by optical mode-locking in which frequency-domain synthesis using a resonant cavity produces desired time-domain features in the transmitted optical signal. In radio systems, users share the same subcarriers, but use different orthogonal CI codes to achieve Carrier Interference Multiple Access (CIMA) via spectral interferometry mechanisms.