方法对比

	Slotted ALOHA 随机接入协议	载波侦听多路访问/冲突避免 (CSMA/CA)	香农信道容量定理
领域	电信	电信	电信
方法族	Process / pipeline	Process / pipeline	Process / pipeline
起源年份	1970	1990	1948
提出者	Norman Abramson and Lawrence Roberts	Phil Karn	Claude Shannon
类型	random access protocol	random access protocol	fundamental theoretical bound
开创性文献	Roberts, L. G. (1975). ALOHA packet system with and without slots and capture. ACM SIGCOMM Computer Communication Review, 5(2), 28-42.	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.	Shannon, C. E. (1948). A mathematical theory of communication. Bell System Technical Journal, 27(3), 379-423.
别名	random access, medium access	medium access control, WiFi MAC	channel capacity, information theory bound
相关	3	3	5
摘要	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.	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).	Shannon's channel capacity theorem, published in 1948, establishes the maximum rate at which information can be reliably transmitted over a noisy channel. Expressed as C = B log2(1 + S/N) for additive white Gaussian noise (AWGN), it is a fundamental bound in information theory and communications engineering. Shannon proved that reliable communication is possible at any rate below capacity, and impossible above it. This theorem underpins the design of all modern communication systems and motivates coding theory, modulation, and signal processing techniques.