A Contention Interval Probabilistic Deferment Backoff Mechanism for IEEE 802.11 DCF With Load-Dependent Slot Offsets

This study presents an extension of the IEEE 802.11 Distributed Coordination Function (DCF) based on a Contention Interval Probabilistic Deferment (CIPD) backoff mechanism designed to address persistent clustering of near-zero backoff counters under congestion. Unlike prior schemes that retain zerobased counter selection and fixed Contention Window (CW) rules, CIPD introduces contention-interval adaptation through a unified load signal and offset-aware reselection. First, a load-dependent slot offset raises the minimum selectable counter only for stations that attempt transmission in a contention interval, which suppresses synchronized early-slot access while preserving compatibility with standard DCF. Second, collision ratio signals provides Exponentially Weighted Moving Average (EWMA) a single contention estimate that controls both proportional CW scaling and offset assignment, enabling contention-interval adjustment across light, medium, and heavy load states. Third, a Discrete-Time Markov Chain (DTMC) with an offset-aware state space models transmission probability, collision rate, and saturation throughput under both stationary and non-stationary traffic, while a packet-level simulator evaluates the effect of CW scaling factors and offset settings through ablation experiments. Across a wide range of network densities, CIPD increases throughput by up to 73.1 %, lowers collision rates by 14.76 %, and achieves a Jain’s fairness index above 0.99, demonstrating consistent gains in both efficiency and fairness