AI 中文总结
本文对比三种无冲突退避算法与 BEB，通过系统级仿真评估 Wi-Fi 在不同流量场景下的性能，发现非全缓冲流量下无冲突访问或降性能，且站点多数时间退回到随机退避。
AI 中文摘要
分布式协调功能（DCF）是 Wi-Fi 底层的信道访问协议，基于带冲突避免的载波侦听多路访问（CSMA/CA）和二进制指数退避（BEB），它简单且有效，但随着冲突增多，其性能会因竞争加剧而下降。无冲突退避算法用确定性信道访问替代随机化，有望提升效率和可预测性。但考虑到协议设计的各种影响，无冲突方法是否足以在现实的非全缓冲流量（含上行和下行传输）下改善 Wi-Fi 性能？我们通过比较三种无冲突算法（CSMA/ECA、CSMA/E2CA 和确定性退避 DetBO）与标准及单阶段 BEB 来研究该问题。利用系统级仿真，我们评估全缓冲流量、含上行和下行传输的非全缓冲开/关流量，以及与 legacy BEB 站点的共存情况。在全缓冲流量下，无冲突操作仅提供适度的吞吐量增益，最高达 6.3%；在非全缓冲流量下，延迟主要由竞争窗口（CW）而非冲突避免决定，且在下行占主导的流量下，无冲突访问甚至会降低性能。站点至少 93% 的时间退回到随机退避，因此在接入点（AP）外几乎不会形成无冲突调度。
英文摘要
The Distributed Coordination Function (DCF)---the underlying channel access protocol in Wi-Fi, based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and Binary Exponential Backoff (BEB)---is simple and effective, but its performance can degrade with increasing contention due to collisions. Collision-free backoff algorithms replace randomization with deterministic channel access, potentially improving efficiency and predictability. But are collision-free methods, with all their implications in terms of protocol design, sufficient to improve Wi-Fi performance under realistic non-full-buffer traffic with both uplink and downlink transmissions? We investigate this question by comparing three collision-free algorithms, CSMA/ECA (ECA), CSMA/E2CA (E2CA), and deterministic backoff (DetBO), with standard and single-stage BEB. Using system-level simulations, we evaluate full-buffer traffic, non-full-buffer ON/OFF traffic with both uplink and downlink transmissions, and coexistence with legacy BEB stations. Under full-buffer traffic, collision-free operation provides only modest throughput gains, up to 6.3\%. With non-full-buffer traffic, delay is governed primarily by the contention window (CW) rather than by collision avoidance, and collision-free access can even degrade performance under downlink-heavy traffic. Stations fall back to a random backoff at least 93\% of the time, so a collision-free schedule rarely forms outside the AP.
Comments8 pages, 5 figures, 3 tables. Submitted to the 17th IFIP Wireless and Mobile Networking Conference (WMNC 2026)
