{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,6,19]],"date-time":"2025-06-19T04:58:25Z","timestamp":1750309105591,"version":"3.41.0"},"reference-count":0,"publisher":"Association for Computing Machinery (ACM)","issue":"1","license":[{"start":{"date-parts":[[1975,1,1]],"date-time":"1975-01-01T00:00:00Z","timestamp":157766400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.acm.org\/publications\/policies\/copyright_policy#Background"}],"content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["SIGCOMM Comput. Commun. Rev."],"published-print":{"date-parts":[[1975,1]]},"abstract":"\n We assume the reader is somewhat familiar with the ongoing\ndevelopment of Aloha techniques as described briefly in Abramson's\nFJCC 7 0 paper and Roberts's SJCC72 paper. In short, an Aloha\nsystem permits the (hopefully) occasional interference of data\npacket transmissions in a multi-access channel and provides for the\nretransmission of lost packets after some randomly distributed\ninterval. The purposes behind permitting interference and providing\nrecovery are (1) reduced central communication control to improve\nreliability and (2) improved use of communication facilites under\nbursty loads as found in interactive computer communication. Aloha\ntechniques are finding applicability in various communication\ncontexts (e.g., satellites), but here the emphasis is on\n large<\/jats:italic>\n populations of (potentially mobile)\n interactive<\/jats:italic>\n terminals.\n <\/jats:p>\n \n Slotted<\/jats:bold>\n . In a\n slotted<\/jats:italic>\n Aloha system, all terminals\nbegin their packet (re)transmissions at the ' tick of some global\nclock. Slotting has been advocated by Roberts as a simple way to\nimprove the limiting thruput of an Aloha channel by a factor of 2.\nGlobal ticking can be implemented in a (hopefully positive) number\nof ways and its feasibility is assumed in this paper. We rely on\nslotting to simplify our analysis, but suggest that the stability\nand control phenomena studied are characteristic of Aloha systems\nin general.\n <\/jats:p>\n \n Controlled<\/jats:bold>\n . The notion of an optimal retransmission delay\nwas introduced by Roberts. We extend the notion to include dynamic\ncontrol of retransmission delay. A\n controlled<\/jats:italic>\n Aloha system\nhas the property that its terminals adjust their retransmission\nbehavior as a function of perceived channel utilization. It will be\nshown that such adjustments are implementable in at least one way\nand that they improve system performance under heavy loads.\n <\/jats:p>\n \n Blocking and Thinking<\/jats:bold>\n . When a user's terminal has a ready\npacket, it is assumed that no new packets can be generated. The\nuser is said to be\n blocked<\/jats:italic>\n . When a user is not blocked, he\nis said to be\n thinking<\/jats:italic>\n . This assumption about user behavior\ndeparts from Abramson 's analysis and is thought to produce more\nrealistic solutions. Recall that Abramson (in FJCC70) modelled\nusers as unperturbable, realtime, Poisson sources of new packets.\nBy adding blocking to an Aloha model, transmission delays feed back\n(as in real life) on the generation of transmission requests. User\nsessions are said to be\n dilated<\/jats:italic>\n by transmissions delays.\n <\/jats:p>\n \n It is intended that\n think<\/jats:italic>\n time account for (1) delays in\ncentral system response, (2) return transmission delays, (3) real\nuser thinking time, and (4) type-in time.\n Block<\/jats:italic>\n time\naccounts only for delays due to transmissions through the\nmulti-access channel.\n <\/jats:p>\n The following analysis rests on some (very) simplifying\nassumptions about an Aloha system in equilibrium, in steady state.\nWhile having a large population of users tends to support our\nsteady-state arguments, the dynamics do indeed require more\ndetailed investigation.<\/jats:p>","DOI":"10.1145\/1024847.1024849","type":"journal-article","created":{"date-parts":[[2004,10,12]],"date-time":"2004-10-12T13:44:32Z","timestamp":1097588672000},"page":"24-31","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":15,"title":["Steady-state analysis of a slotted and controlled Aloha system with blocking"],"prefix":"10.1145","volume":"5","author":[{"given":"Bob","family":"Metcalfe","sequence":"first","affiliation":[{"name":"Xerox Palo Alto Research Center"}]}],"member":"320","published-online":{"date-parts":[[1975,1]]},"container-title":["ACM SIGCOMM Computer Communication Review"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dl.acm.org\/doi\/10.1145\/1024847.1024849","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/dl.acm.org\/doi\/pdf\/10.1145\/1024847.1024849","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T22:48:45Z","timestamp":1750286925000},"score":1,"resource":{"primary":{"URL":"https:\/\/dl.acm.org\/doi\/10.1145\/1024847.1024849"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1975,1]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1975,1]]}},"alternative-id":["10.1145\/1024847.1024849"],"URL":"https:\/\/doi.org\/10.1145\/1024847.1024849","relation":{},"ISSN":["0146-4833"],"issn-type":[{"type":"print","value":"0146-4833"}],"subject":[],"published":{"date-parts":[[1975,1]]},"assertion":[{"value":"1975-01-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}