350-101 Cisco Implementing and Operating Cisco Wireless Core Technologies

MIMO, or Multiple-Input Multiple-Output, is a core 802.11n and later wireless technology that uses multiple transmit and receive radio chains and antennas to improve wireless performance. Cisco’s Wireless RF Reference Guide explains that IEEE 802.11n introduced MIMO, replacing the older single-radio SISO model with multiple radios, each using its own antenna, to increase data rates and improve reception in multipath environments. Cisco also notes that weak or distorted multipath signals can be received by more than one radio and reconstructed, improving decode quality and reliability. This directly supports option A: MIMO exploits multiple RF paths rather than treating multipath as purely destructive. Depending on implementation, MIMO can use spatial diversity, maximal ratio combining, and spatial streams to increase throughput, improve signal-to-noise ratio, reduce retries, and make more efficient use of airtime. Cisco describes spatial stream notation such as 4x4:4 as four transmitters, four receivers, and four spatial streams. Option B describes frequency hopping, not MIMO. Option C is not a MIMO function. Option D is the opposite of MIMO because MIMO deliberately uses multiple antennas and radio paths. Reference topics: 802.11 Technology Fundamentals — MIMO, spatial streams, multipath, SISO versus MIMO, and 802.11n/ac/ax PHY enhancements.