Vertaile menetelmiä
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| Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)× | Monitulo-monitulo (MIMO)× | Slotted ALOHA -satunnaisprotokolla× | |
|---|---|---|---|
| Tieteenala | Tietoliikennetekniikka | Tietoliikennetekniikka | Tietoliikennetekniikka |
| Menetelmäperhe | Process / pipeline | Process / pipeline | Process / pipeline |
| Syntyvuosi≠ | 1990 | 1995 | 1970 |
| Kehittäjä≠ | Phil Karn | Telatar, Foschini, and Gans | Norman Abramson and Lawrence Roberts |
| Tyyppi≠ | random access protocol | spatial multiplexing technique | random access protocol |
| Alkuperäislähde≠ | 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. link ↗ | Telatar, I. (1999). Capacity of multi-antenna Gaussian channels. European Transactions on Telecommunications, 10(6), 585-595. DOI ↗ | Roberts, L. G. (1975). ALOHA packet system with and without slots and capture. ACM SIGCOMM Computer Communication Review, 5(2), 28-42. DOI ↗ |
| Rinnakkaisnimet | medium access control, WiFi MAC | spatial multiplexing, antenna diversity | random access, medium access |
| Liittyvät≠ | 3 | 5 | 3 |
| Tiivistelmä≠ | 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). | MIMO is a technique that uses multiple transmit and receive antennas to significantly increase channel capacity and reliability. Pioneered theoretically by Telatar (1999) and Foschini & Gans (1998), MIMO exploits multipath propagation—typically a liability in wireless—as an asset by creating independent spatial channels. It is now fundamental to all modern wireless systems including LTE, WiFi-6, and 5G, where it provides both capacity gains through spatial multiplexing and robustness through diversity. | 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. |
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