Networking · Cluster
Wireless Networking
Radio behavior, medium access, and mobility.
- 01 The Hidden Terminal Problem and Why 802.11 Reserves the Medium Why listening before transmitting fails on radio, how RTS/CTS and the duration field build a virtual carrier sense, and what the reservation costs per frame.
- 02 DCF Backoff and the Contention Window Growth Rule How a station decides when to transmit after the medium goes idle, why the backoff is counted in slots rather than microseconds, and how the window doubles after loss.
- 03 802.11 Address Fields and the Four-Address Distribution System Why a Wi-Fi frame carries up to four MAC addresses, how the ToDS and FromDS bits select which is which, and what breaks when a bridge is inserted.
- 04 OFDM Subcarrier Spacing, Guard Intervals, and Channel Width Why a wide Wi-Fi channel is divided into many narrow subcarriers, what the cyclic prefix protects against, and how spacing changed in later amendments.
- 05 Rate Adaptation and How a Station Chooses Its MCS How a transmitter infers channel quality it cannot measure, why the retry count is a noisy signal, and what the probe-then-fallback strategies cost.
- 06 A-MPDU Aggregation and Block Acknowledgement How 802.11n packs many frames into one transmission, why each subframe keeps its own check sequence, and what the block ack bitmap window buys.
- 07 Airtime Fairness and Why One Slow Client Halves a Cell How per-station throughput diverges from per-station airtime, how frame duration is computed from rate and size, and what a scheduler can do about it.
- 08 Fast BSS Transition and the Key Hierarchy That Makes Roaming Quick Why reassociating to a new access point normally costs a full authentication and key exchange, and how pre-derived keys cut that to two messages.
- 09 Spatial Reuse, OBSS Interference, and BSS Coloring Why overlapping cells defer to each other even when they could transmit, what the preamble carries to fix it, and how a colour is chosen without coordination.
- 10 OFDMA Scheduling and Multi-User Transmission in Wi-Fi How a 20 MHz channel is split into resource units, how a trigger frame coordinates simultaneous uplinks, and what the scheduling overhead costs.