multiple access protocol
\u7528\u4f86\u898f\u7bc4\u5171\u7528\u5ee3\u64ad\u901a\u9053\u7684\u50b3\u8f38<\/p>\n\n\n\n
\u5e38\u898b\u76843\u7a2e\u985e\u578b<\/strong> \u5e38\u898b\u7684channel partitioning protocol\u6280\u8853<\/strong> \u5e38\u898b\u7684taking-turns protocol\u6280\u8853<\/strong> \u5e38\u898b\u7684random access protocol\u6280\u8853<\/strong> ………………………………………………………………………….\u00a0<\/p>\n\n\n\n ALOHAnet<\/strong> \u7279\u6027 Pure ALOHA<\/strong> Slotted ALOHA<\/strong> … <\/p>\n\n\n\n \u901a\u904e\u91cf\u5206\u6790<\/strong> pure ALOHA <\/strong> slotted ALOHA <\/strong> \u7d50\u8ad6 ……………………………………………………………………..<\/p>\n\n\n\n carrier sense multiple access(\u8f09\u6ce2\u611f\u61c9\u591a\u91cd\u5b58\u53d6)<\/strong> collision detection(\u78b0\u649e\u5075\u6e2c)<\/strong> \u91cd\u50b3\u7b49\u5f85\u6642\u9593\u7684\u516c\u5f0f<\/strong> ……. <\/p>\n\n\n\n CSMA\/CD<\/strong> MACA(multiple access with collision avoidance,\u78b0\u649e\u907f\u514d\u4e4b\u591a\u91cd\u5b58\u53d6) <\/strong> CSMA\/CA(Carrier Sense Multiple Access\/Collision Avoidance,\u8f09\u6ce2\u6aa2\u6e2c\u591a\u8def\u5b58\u53d6\/\u78b0\u649e\u907f\u514d)<\/strong> multiple access protocol\u7528\u4f86\u898f\u7bc4\u5171\u7528 …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"","fifu_image_alt":"","_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[26],"tags":[],"class_list":["post-809","post","type-post","status-publish","format-standard","hentry","category-osi-layer2"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/809","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/comments?post=809"}],"version-history":[{"count":0,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/809\/revisions"}],"wp:attachment":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/media?parent=809"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/categories?post=809"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/tags?post=809"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
channel partitioning protocol(\u901a\u9053\u5206\u5272)
random access protocol(\u96a8\u6a5f\u5b58\u53d6)
taking-turns protocol(\u8f2a\u6d41\u5b58\u53d6)<\/p>\n\n\n\n
TDMA(time division multiple access)
FDMA(frequency division multiple access)
CDMA(code division multiple access)<\/p>\n\n\n\n
polling protocol(\u8f2a\u8a62\u5354\u5b9a), used in 802.15 bluetooth
token-passing protocol(\u4ee4\u724c\u50b3\u905e\u5354\u5b9a),used in 802.5 and FDDI<\/p>\n\n\n\n
ALOHA,slotted ALOHA, CSMA
CSMA\/CD, used in Ethernet
CSMA\/CA, used in 802.11 wireless<\/p>\n\n\n\n
\u4e5f\u7a31\u70baALOHA system
\u7531\u7f8e\u570b\u590f\u5a01\u5937\u5927\u5b78\u6240\u958b\u767c\u7684\u5be6\u9a57\u6027\u96fb\u8166\u7db2\u8def\u7cfb\u7d71
1971\u5e746\u6708\u958b\u59cb\u6210\u529f\u904b\u4f5c
\u662f\u4e16\u754c\u4e0a\u7b2c\u4e00\u500b\u7121\u7dda\u8cc7\u6599\u7db2\u8def<\/p>\n\n\n\n
\u3000\u4f5c\u7528\u5728data-link layer
\u3000\u5c6c\u65bcRandom Access Protocol(\u96a8\u6a5f\u5b58\u53d6\u5354\u8b70)
\u904b\u4f5c
\u3000\u63a5\u6536\u9ede\u5728\u6536\u5230\u6578\u64da\u5f8c\uff0c\u6b63\u78ba\u5247\u56de\u8986ACK\uff0c\u932f\u8aa4\u5247\u56de\u8986NACK
\u3000\u5982\u679c\u767c\u751f\u78b0\u649e\uff1a\u5404\u81ea\u7b49\u5f85\u4e00\u6bb5\u96a8\u6a5f\u9577\u5ea6\u7684\u6642\u9593\u5f8c\uff0c\u518d\u6b21\u5617\u8a66\u50b3\u9001
\u53ef\u5206\u70ba
\u3000Pure ALOHA,\u6709\u592a\u591a\u7684\u50b3\u8f38\u885d\u7a81
\u3000Slotted ALOHA,ALOHA\u7684\u6539\u826f\u3000
ps:
Aloha\u548cslotted aloha\u50b3\u8f38\u524d\u4e0d\u6703\u5148\u6aa2\u67e5\u7db2\u8def\u5a92\u9ad4\u662f\u5426\u6709\u8cc7\u6599\u5728\u50b3\u8f38 <\/p>\n\n\n\n
\u61c9\u7528\uff1a\u56e0\u983b\u9053\u885d\u7a81\u592a\u9ad8\uff0c\u5f88\u5c11\u88ab\u7528
\u7576\u50b3\u8f38\u9ede\u6709\u6578\u64da\u9700\u8981\u50b3\u9001\u7684\u6642\u5019\uff0c\u6703\u7acb\u5373\u5411\u901a\u8a0a\u983b\u9053\u50b3\u9001<\/p>\n\n\n\n
\u61c9\u7528\uff1a\u5728\u624b\u6a5f\u7db2\u8def\u901a\u4fe1\u4e2d
\u512a\u9ede\uff1a\u6642\u9593\u5206\u5272\u6210\u7b49\u9577\u7684slot\u53ef\u6e1b\u5c11\u50b3\u8f38\u983b\u9053\u7684\u885d\u7a81
\u7576\u50b3\u8f38\u9ede\u6709\u6578\u64da\u9700\u8981\u50b3\u9001\u7684\u6642\u5019,\u53ea\u80fd\u5728\u4e0b\u4e00slot\u7684\u958b\u982d\u50b3\u9001\u5c01\u5305
\u6bcf\u6b21\u50b3\u9001\u7684\u6578\u64da\u5fc5\u9808\u5c11\u65bc\u6216\u8005\u7b49\u65bc\u4e00\u500bslot<\/p>\n\n\n\n
S=throughput per frame time,\u901a\u904e\u91cf
G=attempt per packet time,\u63d0\u4f9b\u7684\u6d41\u91cf(\u6bcf\u55ae\u4f4d\u6642\u9593\u901a\u904e\u7684\u6578\u64da\u5305\u6578\u91cf\uff09<\/p>\n\n\n\n
S=G*e^(-2G)
\u7576G<0.5,\u7d14ALOHA\u7cfb\u7d71\u624d\u8655\u65bc\u7a69\u5b9a\u72c0\u614b
\u7576G=0.5,S=0.184,\u4e5f\u5c31\u662fS\u53ef\u9054\u5230\u6700\u5927\u503c18.4%
\u7576G>0.5\u6642S\u958b\u59cb\u905e\u6e1b<\/p>\n\n\n\n
S=G*e^(-G)
\u7576G<1,\u5206\u6bb5ALOHA\u7cfb\u7d71\u624d\u8655\u65bc\u7a69\u5b9a\u72c0\u614b
\u7576G=1,S=0.368,\u4e5f\u5c31\u662fS\u53ef\u9054\u5230\u6700\u5927\u503c36.8%
\u7576G>1\u6642S\u958b\u59cb\u905e\u6e1b<\/p>\n\n\n\n
aloha\u4e0d\u662fstable\u7684madium control access protocol<\/p>\n\n\n\n
\u50b3\u8f38\u524d\u5148\u6aa2\u67e5\u7db2\u8def\u5a92\u9ad4\u662f\u5426\u6709\u8cc7\u6599\u5728\u50b3\u8f38,\u6b64\u70bacarrier sense
\u4e3b\u8981\u6709\u4e09\u5927\u6a5f\u5236
1-persistent:\u82e5\u9592\u7f6e\u5247\u7acb\u523b\u50b3\u9001,ethernet\u4f7f\u7528\u7684\u65b9\u6cd5
nonpersistent\/0-persistent:\u9592\u7f6e\u6642\u50b3\u9001,\u5fd9\u9304\u6642\u96a8\u6a5f\u7b49\u5f85\u4e00\u6bb5\u6642\u5728\u5075\u6e2c, \u9069\u5408\u7db2\u8def\u8ca0\u8f09\u91cd\u7684\u74b0\u5883
p-persistent:\u9592\u7f6e\u6642\u6709p\u7684\u6a5f\u7387\u7acb\u523b\u50b3\u9001,p-1\u7684\u6a5f\u7387\u7b49\u5f85\u4e0b\u4e00\u500b\u6642\u69fd, \u9069\u5408\u7db2\u8def\u8ca0\u8f09\u8f15\u7684\u74b0\u5883<\/p>\n\n\n\n
\u50b3\u9001\u8cc7\u6599\u6642\u4e5f\u540c\u6642\u8039\u807d,\u4ee5\u78ba\u4fdd\u540c\u4e00\u6642\u9593\u5167\u4e26\u6c92\u6709\u5176\u5b83\u5de5\u4f5c\u7ad9\u4e5f\u5728\u7db2\u8def\u5a92\u9ad4\u4e0a\u50b3\u9001\u8cc7\u6599,\u6b64\u70bacarrier detection
\u540c\u6642\u9001\u51fa\u5c01\u5305,\u8a0a\u865f\u6703\u91cd\u758a\u4e26\u7522\u751f\u78b0\u649e(\u7bc0\u9ede\u8d8a\u591a\ufe50\u8ddd\u96e2\u8d8a\u9577\ufe50\u767c\u751f\u6a5f\u6703\u5c31\u8d8a\u9ad8)
\u6d41\u7a0b\u5982\u4e0b
1\u78b0\u649e\u767c\u751f\u6642\u6703\u5728\u7db2\u7dda\u7522\u751f\u4e00\u500bfrequecy ripple(\u983b\u7387\u6f23\u6f2a)
2\u7bc0\u9ede\u76e3\u6e2c\u5230\u6709\u9019\u6a23\u7684ripple\u5c31\u5ee3\u64ad\u4e00\u500bJamming Signal(\u64fe\u4e82\u8a0a\u865f\/\u9ad8\u983b\u4fe1\u865f\/\u96cd\u585e\u4fe1\u865f),\u544a\u8a34\u6240\u6709\u7bc0\u9ede\u78b0\u649e\u5df2\u7d93\u767c\u751f
ps:\u58c5\u585e\u8a0a\u865f\u53ef\u7531\u4efb\u4f55\u7684\u4e8c\u9032\u4f4d\u8cc7\u6599\u7d44\u6210,\u53ea\u8981\u4e0d\u7522\u751f\u8a0a\u6846\u5167\u7684checksum\u5373\u53ef
3\u5168\u90e8\u7bc0\u9ede\u4e0d\u518d\u767c\u9001\u5c01\u5305,\u4e26random delay time\u96a8\u6a5f\u7b49\u5f85\u4e00\u6bb5\u6642\u9593\u518d\u91cd\u65b0\u9032\u884c\u50b3\u8f38
ps:
\u767c\u751f\u78b0\u649e\u7684\u5de5\u4f5c\u7ad9,\u9700\u7b49\u5f85\u66f4\u4e45\u7684\u6642\u9593\u624d\u6703\u91cd\u65b0\u9032\u884c\u50b3\u8f38
ps:
random delay time\u7531Binary Exponential Backoff Algorithm(\u4e8c\u5143\u6307\u6578\u5f8c\u9000\u6f14\u7b97\u6cd5)\u8ca0\u8cac
binary exponential backoff algorithm:\u96a8\u6a5f\u7684\u79d2\u6578\u662f0\u52302^i-1,i\u662f\u7b2c\u5e7e\u6b21\u78b0\u649e,\u53ef\u9032\u884c16\u6b21
ps:
backoff(\u64a4\u56de\u91cd\u50b3):\u7576\u78b0\u649e\u767c\u751f\u6642,\u6240\u5f37\u5236\u9032\u884c\u7684\u91cd\u65b0\u50b3\u8f38\u7684\u5ef6\u9072<\/p>\n\n\n\n
\u8a2dk\u662f\u7b2c\u5e7e\u6b21\u91cd\u50b3,r\u4ecb\u65bc0\u52302^k
0=r<=2^k ; r*slot time=\u91cd\u50b3\u7b49\u5f85\u6642\u9593
ex:10mbps\u7db2\u8def,\u767c\u751f\u78b0\u649e5\u6b21
0=(0~32)<=2^5 ; (0~32)*51.2\u5fae\u79d2=(0~1638.4)\u5fae\u79d2
\u6700\u4e45\u9700\u8981\u7b49\u5f851638.4\u5fae\u79d2\u6642\u9593\u624d\u6703\u91cd\u50b3<\/p>\n\n\n\n
\u5927\u81f4\u904b\u4f5c\u5982\u4e0b:
1\u6e96\u5099\u958b\u59cb:\u82e5\u7dda\u8def\u7a7a\u9592\u5247\u50b3\u8f38,\u7dda\u8def\u5fd9\u5247\u5230\u7b2c4\u6b65
2\u958b\u59cb\u50b3\u8f38:\u82e5\u50b3\u8f38\u6642\u6aa2\u6e2c\u5230\u885d\u7a81\u5247\u5230\u7b2c4\u6b65
3\u50b3\u8f38\u6210\u529f:\u5411\u4e0a\u5c64\u5831\u544a\u6210\u529f\u4e26\u9000\u51fa\u50b3\u8f38\u6a21\u5f0f
4\u7dda\u8def\u5fd9:\u7b49\u5f85\u7dda\u8def\u7a7a\u9592
5\u7dda\u8def\u7a7a\u9592:\u9032\u5165\u7b2c1\u6b65
6\u8d85\u904e\u6700\u5927\u5690\u8a66\u50b3\u8f38\u6b21\u6578:\u5411\u4e0a\u5c64\u5831\u544a\u5931\u6557\u4e26\u9000\u51fa\u50b3\u8f38\u6a21\u5f0f <\/p>\n\n\n\n
\u6703\u6709\u5169\u500b\u554f\u984c
hidden station
exposed sation<\/p>\n\n\n\n
\u50b3\u9001\u524d\u5148\u5075\u6e2c\u983b\u9053\u662f\u5426\u9592\u7f6e,
\u82e5\u9592\u7f6e\u5247\u7b49\u5f85IFS(Interval Frame Space)\u6642\u9593\u5f8c\u518d\u5075\u6e2c\u662f\u5426\u9592\u7f6e,\u82e5\u7a7a\u9592\u5247\u50b3\u9001,\u82e5\u7121\u7a7a\u9592\u5247\u7b49\u5f85
ps:\u9001\u51faframe\u5f8c,\u904e\u7a0b\u4e2d\u4e0d\u7528\u50cfcsma\/cd\u5728\u53e6\u5916\u5075\u6e2c
\u53ef\u80fd\u5728\u63a5\u6536\u7aef\u56e0\u5e72\u64fe\u906d\u7834\u58de,\u82e5\u78b0\u649e\u5f8c\u6703\u7b49\u5f85random delay time(\u96a8\u6a5f\u5ef6\u9072\u6642\u9593)\u5f8c\u91cd\u50b3
ps:
random delay time\u7531Binary Exponential Backoff Algorithm(\u4e8c\u5143\u6307\u6578\u5f8c\u9000\u6f14\u7b97\u6cd5)\u8ca0\u8cac
ps:
802.11\u63a1\u7528\u7684\u5a92\u9ad4\u5b58\u53d6\u63a7\u5236\u65b9\u5f0f\u70baCSMA\u53caMACAW\u7d50\u5408
MACAW(MACA for wireless,\u7121\u7dda\u7db2\u8def\u4e4bMACA)\uff1a\u4fee\u6539\u7248\u7684MACA,\u4f7f\u5176\u6548\u7387\u589e\u52a0<\/p>\n\n\n\n
CSMA\/CD\u548cCSMA\/CA\u5dee\u7570<\/strong>
CSMA\/CA
\u8457\u91cd\u5728\u8cc7\u6599\u50b3\u9001\u5f8c\u4e0d\u6703\u78b0\u649e
\u767c\u73fe\u983b\u9053\u9592\u7f6e\u6642,\u6703\u7b49\u5f85\u96a8\u6a5f\u6642\u9593\u5728\u5c07\u8a0a\u6846\u50b3\u9001\u51fa\u53bb
\u5931\u655732\u6b21\u5f8c\u901a\u77e5\u4e0a\u5c64Timeout
CSMA\/CD
\u8457\u91cd\u5728\u6aa2\u6e2c\u78b0\u649e
\u767c\u73fe\u983b\u9053\u9592\u7f6e\u6642,\u5c07\u8a0a\u6846\u7acb\u523b\u50b3\u9001\u51fa\u53bb
\u5931\u655715\u6b21\u5f8c\u901a\u77e5\u4e0a\u5c64Timeout
ps:
CSMA\/CD\u6703\u8b93\u91cd\u9001\u6642\u9593\u8b8a\u9577\uff0c\u589e\u52a0\u91cd\u9001\u6210\u672c\uff0c\u4e0d\u5efa\u8b70\u7528\u5728Wireless<\/p>\n","protected":false},"excerpt":{"rendered":"