{"id":70827,"date":"2020-02-21T14:42:12","date_gmt":"2020-02-21T11:42:12","guid":{"rendered":"https:\/\/prohoster.info\/blog\/802-11ba-wur-ili-kak-skrestit-uzha-s-ezhom"},"modified":"2020-03-03T16:14:44","modified_gmt":"2020-03-03T13:14:44","slug":"802-11ba-wur-ili-kak-skrestit-uzha-s-ezhom","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sq\/blog\/administrirovanie\/802-11ba-wur-ili-kak-skrestit-uzha-s-ezhom","title":{"rendered":"802.11ba (WUR) ose si t\u00eb kryq\u00ebzoni nj\u00eb gjysm\u00ebz dhe nj\u00eb hedgehog","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Jo pak jo, n\u00eb t\u00eb kaluar\u00ebn kam folur p\u00ebr k\u00ebt\u00eb n\u00eb burime t\u00eb ndryshme dhe n\u00eb blogun tim, q\u00eb ZigBee \u00ebsht\u00eb i vdekur dhe se \u00ebsht\u00eb koha p\u00ebr t\u00eb varrosur stewardes\u00ebn. P\u00ebr t\u00eb b\u00ebr\u00eb nj\u00eb fytyr\u00eb t\u00eb mir\u00eb n\u00eb nj\u00eb loj\u00eb t\u00eb keqe me Thread, q\u00eb funksionon mbi IPv6 dhe 6LowPan, mjafton nj\u00eb Bluetooth (LE) m\u00eb i p\u00ebrshtatsh\u00ebm p\u00ebr k\u00ebt\u00eb. Por p\u00ebr k\u00ebt\u00eb do t\u00eb flas ndonj\u00ebher\u00eb n\u00eb nj\u00eb tjet\u00ebr rast. Sot do t\u00eb flas p\u00ebr m\u00ebnyr\u00ebn se si grupi i pun\u00ebs i komitetit mendoi mir\u00eb p\u00ebr her\u00eb t\u00eb dyt\u00eb pas 802.11ah dhe vendosi se ishte koha p\u00ebr t\u00eb shtuar n\u00eb fondin e standardeve 802.11 nj\u00eb variant t\u00eb plot\u00eb t\u00eb di\u00e7kaje si LRLP (Long-Range Low-Power) n\u00eb p\u00ebrputhje me LoRA. Por kjo doli t\u00eb ishte e pamundur pa prer\u00eb vi\u00e7in e shenjt\u00eb t\u00eb kompatibilitetit mbrapa. Si rezultat, u dor\u00ebzuan nga Long-Range dhe mbeti vet\u00ebm Low-Power, q\u00eb gjithashtu \u00ebsht\u00eb shum\u00eb mir\u00eb. K\u00ebshtu, u krijua nj\u00eb p\u00ebrzierje e 802.11 + 802.15.4 ose thjesht Wi-Fi + ZigBee. Pra, mund t\u00eb themi se teknologjia e re nuk \u00ebsht\u00eb nj\u00eb konkurrenc\u00eb p\u00ebr zgjidhjet LoraWAN, por p\u00ebrkundrazi krijohet p\u00ebr t'i plot\u00ebsuar ato.
\n<\/a><\/noindex>
\nPra ndaj, le t\u00eb fillojm\u00eb me t\u00eb r\u00ebnd\u00ebsishmen \u2014 Tani n\u00eb pajisjet q\u00eb mb\u00ebshtesin 802.11ba duhet t\u00eb ket\u00eb dy radio module. Duket se, pas shqyrtimit t\u00eb 802.11ah\/ax me teknologjin\u00eb e Target Wake Time (TWT), inxhinier\u00ebt vendos\u00ebn se kjo \u00ebsht\u00eb e pap\u00ebrgjegjshme dhe duhet ulur ndjesh\u00ebm konsumi i energjis\u00eb. P\u00ebr k\u00ebt\u00eb arsye, standardi parashikon ndarjen n\u00eb dy lloje t\u00eb ndryshme radio \u2014 Primary Communication Radio (PCR) dhe Wake-Up Radio (WUR). N\u00ebse p\u00ebr t\u00eb par\u00ebn gjith\u00e7ka \u00ebsht\u00eb e qart\u00eb, kjo \u00ebsht\u00eb radioja kryesore, ajo d\u00ebrgon dhe merr t\u00eb dh\u00ebna, p\u00ebr t\u00eb dyt\u00ebn situata \u00ebsht\u00eb m\u00eb e nd\u00ebrlikuar. Faktikisht, WUR paraqet kryesisht nj\u00eb pajisje gjurmimi (RX) dhe sipas ideve duhet t\u00eb konsumoj\u00eb shum\u00eb pak energji p\u00ebr pun\u00eb. Pjesa e saj kryesore \u00ebsht\u00eb t\u00eb marr\u00eb sinjalin e zgjimit nga AP dhe t\u00eb aktivizoj\u00eb PCR. Pra, ky metod\u00eb duksh\u00ebm ul koh\u00ebn e ftoht\u00eb p\u00ebr t\u00eb filluar dhe lejon q\u00eb pajisjet t\u00eb zgjojn\u00eb n\u00eb nj\u00eb koh\u00eb t\u00eb caktuar me sakt\u00ebsi maksimale. Kjo \u00ebsht\u00eb shum\u00eb e dobishme kur keni, le t\u00eb themi, jo dhjet\u00eb pajisje, por nj\u00ebqind e dhjet\u00eb dhe duhet t\u00eb shk\u00ebmbeni t\u00eb dh\u00ebna me secil\u00ebn prej tyre brenda nj\u00eb periudhe t\u00eb shkurt\u00ebr. P\u00ebr m\u00eb tep\u00ebr, logjika e frekuenc\u00ebs dhe periudh\u00ebs s\u00eb zgjimit kalon n\u00eb an\u00ebn e AP. N\u00ebse, p\u00ebr shembull, n\u00eb LoRAWAN aplikohet metodologjia PUSH kur pajisjet ekzekutuese vet\u00eb zgjojn\u00eb dhe d\u00ebrgojn\u00eb di\u00e7ka n\u00eb aj\u00ebr, n\u00eb k\u00ebt\u00eb rast \u00ebsht\u00eb e kund\u00ebrta, AP vendos se kur dhe cila pajisje duhet t\u00eb zgjohet, nd\u00ebrsa pajisjet ekzekutuese... nuk gjithmon\u00eb flen\u00eb.<\/p>\n

Tani, le t\u00eb kalojm\u00eb te formatet e kadrove dhe sigurimi i p\u00ebrputhshm\u00ebris\u00eb. N\u00ebse 802.11ah si p\u00ebrpjekja e par\u00eb krijohej p\u00ebr zona 868\/915 MHz ose thjesht SUB-1GHz, 802.11ba tashm\u00eb \u00ebsht\u00eb e destinuar p\u00ebr zona 2.4GHz dhe 5GHz. N\u00eb standardet e m\u00ebparshme \"t\u00eb reja\" p\u00ebrputhshm\u00ebria arrihej p\u00ebrmes nj\u00eb preambule kuptimplot\u00eb p\u00ebr pajisjet m\u00eb t\u00eb vjetra. Pra, llogaritja gjithmon\u00eb ishte q\u00eb pajisjet e vjetra nuk ishte e nevojshme t\u00eb jen\u00eb n\u00eb gjendje t\u00eb njohin t\u00eb gjith\u00eb kadron, mjafton t\u00eb kuptojn\u00eb kur kjo ka filluar dhe sa koh\u00eb do t\u00eb zgjas\u00eb transmetimi. Pik\u00ebrisht k\u00ebt\u00eb informacion ato e marrin nga preambula. 802.11ba nuk b\u00ebri p\u00ebrjashtim, pasi skema \u00ebsht\u00eb e provuar dhe e testuar (\u00e7\u00ebshtja e shpenzimeve do ta l\u00ebm\u00eb p\u00ebr m\u00eb von\u00eb).<\/p>\n

N\u00eb p\u00ebrfundim, kadrin 802.11ba duket k\u00ebshtu:<\/p>\n

\"802.11ba
\n
\nPreambula Non-HT dhe nj\u00eb fragment i shkurt\u00ebr i OFDM me modulimin BPSK lejon t\u00eb gjitha pajisjet 802.11a\/g\/n\/ac\/ax t\u00eb d\u00ebgjojn\u00eb fillimin e transmetimit t\u00eb k\u00ebtij kadri dhe t\u00eb mos nd\u00ebrhyjn\u00eb, duke kaluar n\u00eb modin e d\u00ebgjimit t\u00eb val\u00ebve. Pas preambul\u00ebs vjen fusha e sinkronizimit (SYNC) q\u00eb n\u00eb thelb \u00ebsht\u00eb nj\u00eb ekuivalent i L-STF\/L-LTF. Ajo sh\u00ebrben p\u00ebr t'i dh\u00ebn\u00eb mund\u00ebsin\u00eb pajisjes p\u00ebr t\u00eb rregulluar frekuenc\u00ebn dhe p\u00ebr t\u00eb sinkronizuar marr\u00ebsin e saj. Dhe pik\u00ebrisht n\u00eb k\u00ebt\u00eb moment, pajisja transmetuese kalon n\u00eb nj\u00eb gjer\u00ebsi kanali tjet\u00ebr prej 4MHz. Pse? E gjith\u00eb kjo \u00ebsht\u00eb shum\u00eb e thjesht\u00eb. Kjo \u00ebsht\u00eb e nevojshme p\u00ebr t\u00eb ulur fuqin\u00eb dhe p\u00ebr t\u00eb arritur nj\u00eb raport t\u00eb krahasuesh\u00ebm t\u00eb sinjalit ndaj fuqis\u00eb me zhurm\u00ebn (SINR). Ose t\u00eb mbajm\u00eb fuqin\u00eb ashtu si\u00e7 \u00ebsht\u00eb dhe t\u00eb arrijm\u00eb nj\u00eb rritje t\u00eb konsiderueshme t\u00eb distanc\u00ebs s\u00eb transmetimit. Do t\u00eb thosha se kjo \u00ebsht\u00eb nj\u00eb zgjidhje mjaft elegante, p\u00ebr m\u00eb tep\u00ebr, q\u00eb lejon uljen e k\u00ebrkesave p\u00ebr burimet e energjis\u00eb. Le ta kujtojm\u00eb, p\u00ebr shembull, nj\u00ebsin\u00eb popullore ESP8266. N\u00eb modin e transmetimit me nj\u00eb bit rate prej 54 Mbps dhe fuqis\u00eb prej 16 dBm, ajo konsumon 196 mA, q\u00eb \u00ebsht\u00eb shum\u00eb e lart\u00eb p\u00ebr di\u00e7ka si CR2032. N\u00ebse e ulim pes\u00eb her\u00eb gjer\u00ebsin\u00eb e kanalit dhe pes\u00eb her\u00eb fuqin\u00eb e transmetuesit, at\u00ebher\u00eb praktikisht nuk do t\u00eb humbim n\u00eb distanc\u00ebn e transmetimit, por do ta kemi konsumimin e energjis\u00eb t\u00eb ulur, le t\u00eb themi, rreth 50 mA. Nuk \u00ebsht\u00eb se kjo \u00ebsht\u00eb kritike p\u00ebr AP-n\u00eb q\u00eb transmeton kadrin p\u00ebr WUR, por gjithsesi \u00ebsht\u00eb mir\u00eb. Nd\u00ebrsa p\u00ebr STA kjo ka kuptim, pasi konsumimi m\u00eb i ul\u00ebt lejon p\u00ebrdorimin e di\u00e7kaje si CR2032 ose baterive t\u00eb dizajnuara p\u00ebr ruajtje t\u00eb gjat\u00eb t\u00eb energjis\u00eb me shkarkime t\u00eb ul\u00ebta nominale. Sigurisht, asgj\u00eb nuk \u00ebsht\u00eb falas dhe ulja e gjer\u00ebsis\u00eb s\u00eb kanalit do t\u00eb \u00e7oj\u00eb n\u00eb uljen e shpejt\u00ebsis\u00eb kanale me rritjen e koh\u00ebs s\u00eb transmetimit t\u00eb nj\u00eb kadri p\u00ebrkat\u00ebs. <\/p>\n

M\u00eb kujtoi p\u00ebr shpejt\u00ebsin\u00eb e kanalit. Standarti n\u00eb form\u00ebn e tij aktual parashikon dy variante: 62.5 Kbps dhe 250 Kbps. E ndjeni, a po vjen ZigBee? Kjo nuk \u00ebsht\u00eb rast\u00ebsi, sepse ai ka nj\u00eb gjer\u00ebsi kanali prej 2 MHz n\u00eb vend t\u00eb 4 MHz, por nj\u00eb lloj moduli tjet\u00ebr me nj\u00eb densitet spektri m\u00eb t\u00eb madh. Si rezultat, rrezja e veprimit t\u00eb pajisjeve 802.11ba duhet t\u00eb jet\u00eb m\u00eb e madhe, q\u00eb \u00ebsht\u00eb shum\u00eb e p\u00ebrshtatshme p\u00ebr skenar\u00ebt IoT brenda ambienteve.<\/p>\n

Por sh\u00ebndetje... T\u00eb detyrosh t\u00eb gjitha stacionet n\u00eb rreth t\u00eb heshtin, duke p\u00ebrdorur vet\u00ebm 4 MHz nga shiritin 20 MHz... \"KJO \u00cbSHT\u00cb M\u00cbM\u00cbRSI!\" - do thoni dhe do keni t\u00eb drejt\u00eb. Por jo, KJO \u00cbSHT\u00cb M\u00cbM\u00cbRSIA E V\u00cbRTET\u00cb!<\/p>\n

\"802.11ba
\n
\nN\u00eb standard \u00ebsht\u00eb parashikuar mund\u00ebsia e p\u00ebrdorimit t\u00eb n\u00ebnkanaleve 40 MHz dhe 80 MHz. N\u00eb k\u00ebt\u00eb rast, shpejt\u00ebsit\u00eb e t\u00eb gjitha n\u00ebnkanaleve mund t\u00eb jen\u00eb t\u00eb ndryshme, dhe p\u00ebr t'u p\u00ebrputhur me koh\u00ebn e transmetimit, n\u00eb fund t\u00eb korniz\u00ebs shtohet Padding. K\u00ebshtu, nj\u00eb pajisje mund t\u00eb z\u00ebr\u00eb koh\u00eb etere n\u00eb t\u00eb gjitha 80 MHz, nd\u00ebrsa ta p\u00ebrdor\u00eb at\u00eb vet\u00ebm n\u00eb 16 MHz. Kjo \u00ebsht\u00eb nj\u00eb v\u00ebrtet e v\u00ebrteta m\u00ebm\u00ebrsia.<\/p>\n

Nga ana tjet\u00ebr, pajisjet Wi-Fi t\u00eb rrethit nuk kan\u00eb asnj\u00eb shans t\u00eb kuptojn\u00eb se \u00e7far\u00eb po transmetohet n\u00eb eter. Sepse p\u00ebr kodimin e kornizave 802.11ba nuk p\u00ebrdoret OFDM e njohur p\u00ebr ta. Po, k\u00ebshtu, aleanca hoqi dor\u00eb nga di\u00e7ka q\u00eb ka funksionuar pa ndales\u00eb p\u00ebr shum\u00eb vite. N\u00eb vend t\u00eb OFDM klasik, aplikohet modulimi Multi-Carrier (MC)-OOK. Kanali 4MHz ndahen n\u00eb 16(?) n\u00ebnburime, secila e cila p\u00ebrdor kodim manchester. N\u00eb k\u00ebt\u00eb m\u00ebnyr\u00eb, fusha e t\u00eb dh\u00ebnave (DATA) \u00ebsht\u00eb gjithashtu e ndar\u00eb logjikisht n\u00eb segmente t\u00eb 4 \u03bcs ose 2 \u03bcs n\u00eb var\u00ebsi t\u00eb shpejt\u00ebsis\u00eb, dhe n\u00eb secilin segment t\u00eb till\u00eb, nj\u00ebsi mund t\u00eb p\u00ebrgjigjet nj\u00eb nivel t\u00eb ul\u00ebt ose t\u00eb lart\u00eb t\u00eb kodimit. Kjo \u00ebsht\u00eb nj\u00eb zgjidhje p\u00ebr t\u00eb shmangur nj\u00eb seri t\u00eb gjat\u00eb zeros ose onesh. Skrambllimi n\u00eb minimalet.<\/p>\n

\"802.11ba
\n
\nNiveli MAC gjithashtu \u00ebsht\u00eb ndjesh\u00ebm i thjeshtuar. Ai p\u00ebrmban vet\u00ebm fushat e m\u00ebposhtme:<\/p>\n