方法对比

	载波侦听多路访问/冲突避免 (CSMA/CA)	正交频分复用 (OFDM)	Slotted ALOHA 随机接入协议
领域	电信	电信	电信
方法族	Process / pipeline	Process / pipeline	Process / pipeline
起源年份	1990	1971	1970
提出者	Phil Karn	Weinstein and Ebert	Norman Abramson and Lawrence Roberts
类型	random access protocol	multicarrier modulation scheme	random access protocol
开创性文献	Karn, P. (1990). MACA—a new channel access method for packet radio. In Proceedings of the ARRL/CRRL Amateur Radio 9th Computer Networking Conference, 134-140.	Weinstein, S. B., & Ebert, P. M. (1971). Data transmission by frequency-division multiplexing using the discrete Fourier transform. IEEE Transactions on Communication Technology, 19(5), 628-634.	Roberts, L. G. (1975). ALOHA packet system with and without slots and capture. ACM SIGCOMM Computer Communication Review, 5(2), 28-42.
别名	medium access control, WiFi MAC	multicarrier modulation	random access, medium access
相关	3	5	3
摘要	CSMA/CA is a random access protocol for wireless medium access control, designed to enable multiple devices to share a wireless channel while minimizing collisions. Introduced by Phil Karn in 1990, it is the foundation of WiFi (IEEE 802.11) and is now the de facto standard for unlicensed spectrum access. CSMA/CA combines carrier sensing (listen before transmit) with collision avoidance (RTS/CTS handshake) to improve channel efficiency and fairness, avoiding the efficiency loss of pure random access (Aloha).	OFDM is a multicarrier modulation technique that divides a wideband channel into many narrowband orthogonal subcarriers. Introduced by Weinstein and Ebert in 1971, it exploits the duality between time and frequency domains to efficiently use spectrum while mitigating intersymbol interference in frequency-selective channels. OFDM is now the standard for high-speed wireless systems including WiFi, cellular LTE, and digital broadcasting.	Slotted ALOHA is a fundamental random access protocol enabling multiple devices to share a wireless channel without centralized coordination. Introduced by Abramson (1970) and refined by Roberts (1975), it divides time into fixed slots and allows devices to transmit at the beginning of a slot with a fixed probability. While simple and elegant, Slotted ALOHA achieves only 37% channel utilization under saturation (optimal traffic load), a fundamental limit discovered by Abramson. Despite this limitation, Slotted ALOHA remains a teaching tool and appears in modern systems like satellite and IoT networks.