Ba da dadewa ba, akan wasu albarkatu daban-daban da kuma a cikin blog na, na yi magana game da gaskiyar cewa ZigBee ya mutu kuma lokaci yayi da za a binne ma'aikacin jirgin. Domin sanya fuska mai kyau akan wasa mara kyau tare da Zaren aiki a saman IPv6 da 6LowPan, Bluetooth (LE) wanda ya fi dacewa da wannan ya isa. Amma zan baku labarin wannan wani lokaci kuma. A yau za mu yi magana game da yadda ƙungiyar ma'aikata ta kwamitin ta yanke shawarar yin tunani sau biyu bayan 802.11ah kuma sun yanke shawarar cewa lokaci ya yi da za a ƙara cikakken nau'i na wani abu kamar LRLP (Long-Range Low-Power) zuwa tafkin na 802.11 ma'auni, irin wannan. ku LoRA. Amma wannan ya zama ba zai yiwu ba a aiwatar da shi ba tare da yanka saniya mai tsarki na dacewa da baya ba. A sakamakon haka, an yi watsi da Long-Range kuma kawai Low-Power ya rage, wanda kuma yana da kyau sosai. Sakamakon ya kasance cakuda 802.11 + 802.15.4, ko kuma kawai Wi-Fi + ZigBee. Wato, za mu iya cewa sabuwar fasahar ba ta fafatawa da mafita na LoraWAN ba, amma, akasin haka, ana ƙirƙira su ne don haɗa su.
Don haka, bari mu fara da abu mafi mahimmanci - Yanzu na'urorin da ke goyan bayan 802.11ba yakamata su sami nau'ikan rediyo guda biyu. A bayyane yake, bayan sun kalli 802.11ah/ax tare da fasahar Target Wake Time (TWT), injiniyoyin sun yanke shawarar cewa wannan bai isa ba kuma suna buƙatar rage yawan amfani da wutar lantarki. Me yasa mizanin ya samar da rabe-rabe zuwa nau'ikan rediyo daban-daban - Rediyon Sadarwa na Farko (PCR) da Rediyon Wake-Up (WUR). Idan tare da farko komai ya bayyana, wannan shine babban rediyo, yana watsawa da karɓar bayanai, to tare da na biyu ba haka bane. A zahiri, WUR galibi na'urar saurare ne (RX) kuma an ƙera shi don cinye ƙarfin aiki kaɗan kaɗan. Babban aikinsa shine karɓar siginar tashi daga AP kuma kunna PCR. Wato, wannan hanyar tana da mahimmanci rage lokacin farawa sanyi kuma tana ba ku damar tada na'urori a wani lokaci da aka ba da cikakken daidaito. Wannan yana da amfani sosai idan kuna da, a ce, ba na'urori goma ba, amma ɗari da goma kuma kuna buƙatar musayar bayanai tare da kowannensu a cikin ɗan gajeren lokaci. Bugu da kari, dabarar mita da lokaci na farkawa suna motsawa zuwa gefen AP. Idan kuma a ce LoRAWAN yana amfani da tsarin PUSH ne a lokacin da masu aikin su da kansu suka farka su watsa wani abu a iska, sannan su kwana da sauran lokutan, to a wannan yanayin, akasin haka, AP ta yanke shawarar lokacin da na’urar da ya kamata ta farka, kuma su kansu actuators ... ba kullum barci ba.
Yanzu bari mu matsa zuwa frame Formats da karfinsu. Idan 802.11ah, a matsayin ƙoƙari na farko, an ƙirƙira shi don ƙungiyoyin 868/915 MHz ko kuma kawai SUB-1GHz, to 802.11ba an riga an yi niyya don ƙungiyoyin 2.4GHz da 5GHz. A cikin "sababbin" ma'auni da suka gabata, an sami dacewa ta hanyar gabatarwar da aka fahimta ga tsofaffin na'urori. Wato, lissafin ya kasance koyaushe cewa tsofaffin na'urori ba dole ba ne su iya gane dukkan firam ɗin; ya isa su fahimci lokacin da wannan firam ɗin zai fara da kuma tsawon lokacin watsawa. Wannan bayanin ne suka ɗauka daga gabatarwar. 802.11ba ba togiya, tun da makircin da aka tabbatar da kuma tabbatar (za mu yi watsi da batun halin kaka a yanzu).
Sakamakon haka, firam ɗin 802.11ba yayi kama da wannan:
Ƙirar da ba ta HT ba da ɗan gajeren guntun OFDM tare da daidaitawar BPSK yana ba da damar duk na'urorin 802.11a/g/n/ac/ax don jin farkon watsa wannan firam ɗin kuma kada ku tsoma baki, shiga cikin yanayin sauraron watsa shirye-shirye. Bayan gabatarwar ya zo filin aiki tare (SYNC), wanda shine ainihin analog na L-STF/L-LTF. Yana aiki don ba da damar daidaita mita da daidaita mai karɓar na'urar. Kuma a wannan lokacin ne na'urar watsawa ta canza zuwa wani nisa ta 4 MHz. Don me? Komai mai sauqi ne. Wannan yana da mahimmanci don a iya rage ƙarfin kuma a iya samun daidaitaccen sigina-zuwa-amo rabo (SINR). Ko barin wutar kamar yadda yake kuma cimma gagarumin karuwa a kewayon watsawa. Zan iya cewa wannan kyakkyawan bayani ne, wanda kuma ya ba mutum damar rage yawan buƙatun samar da wutar lantarki. Bari mu tuna, alal misali, mashahurin ESP8266. A cikin yanayin watsawa ta amfani da bitrate na 54 Mbps da ƙarfin 16dBm, yana cinye 196 mA, wanda ba shi da girma ga wani abu kamar CR2032. Idan muka rage fadin tashar da sau biyar kuma muka rage karfin watsawa da sau biyar, to a zahiri ba za mu yi hasarar a cikin kewayon watsawa ba, amma za a rage yawan amfanin da ake amfani da shi da wani abu, a ce, zuwa kusan 50mA. Ba cewa wannan yana da mahimmanci a ɓangaren AP wanda ke watsa tsarin WUR ba, amma har yanzu ba shi da kyau. Amma ga STA wannan ya riga ya zama ma'ana, tun da ƙananan amfani yana ba da damar yin amfani da wani abu kamar CR2032 ko batura da aka tsara don ajiyar makamashi na dogon lokaci tare da ƙananan raƙuman ruwa. Tabbas, babu wani abu da ke zuwa kyauta kuma rage girman tashar zai haifar da raguwar saurin tashar tare da haɓaka lokacin watsawa na firam ɗaya, bi da bi.
Af, game da saurin tashar. Ma'auni a cikin tsari na yanzu yana ba da zaɓuɓɓuka biyu: 62.5 Kbps da 250 Kbps. Kuna jin warin ZigBee? Wannan ba abu ne mai sauƙi ba, tun da yake yana da fadin tashar 2Mhz maimakon 4Mhz, amma nau'in nau'in modulation daban-daban tare da mafi girman spectral density. A sakamakon haka, kewayon na'urorin 802.11ba yakamata ya zama mafi girma, wanda ke da matukar amfani ga yanayin IoT na cikin gida.
Ko da yake, jira minti ɗaya... Tilastawa duk tashoshin da ke yankin yin shiru, yayin da suke amfani da 4 MHz kawai na rukunin 20 MHz ... "WANNAN ɓatanci ne!" - za ku ce kuma za ku yi gaskiya. Amma a'a, WANNAN SHINE GASKIYA!
Ma'aunin yana ba da damar yin amfani da ƙananan tashoshin 40 MHz da 80 MHz. A wannan yanayin, bitrates na kowane tashoshi na iya zama daban-daban, kuma don dacewa da lokacin watsa shirye-shiryen, ana ƙara Padding zuwa ƙarshen firam. Wato, na'urar na iya ɗaukar lokacin iska akan duk 80 MHz, amma amfani da ita kawai akan 16 MHz. Wannan sharar gida ce ta gaske.
Af, kewaye na'urorin Wi-Fi ba su da damar fahimtar abin da ake watsawa a wurin. Saboda ba a amfani da OFDM na yau da kullun don ɓoye firam ɗin 802.11ba. Haka ne, kamar haka, ƙawancen ya yi watsi da abin da ya yi aiki mara kyau na shekaru da yawa. Madadin OFDM na al'ada, Multi-Day (MC) -OOK ana amfani da tsarin. An raba tashar 4MHz zuwa 16 (?) masu ɗaukar kaya, kowannensu yana amfani da ɓoye bayanan Manchester. A lokaci guda kuma, filin DATA da kansa shima yana cikin ma'ana ya kasu kashi 4 μs ko 2 μs dangane da bitrate, kuma a kowane irin wannan yanki ƙananan ko babban matakin ɓoye na iya dacewa da ɗaya. Wannan ita ce mafita don guje wa dogon jerin sifilai ko waɗanda. Scrambling a mafi ƙarancin albashi.
Hakanan an sauƙaƙa matakin MAC sosai. Ya ƙunshi fage masu zuwa kawai:
- Sarrafa Frame
Zai iya ɗaukar ƙimar Beacon, WuP, Ganowa ko kowace ƙimar zaɓin mai siyarwa.
Ana amfani da Beacon don daidaitawa lokaci, WuP an tsara shi don tada ɗaya ko rukuni na na'urori, kuma Discovery yana aiki a kishiyar shugabanci daga STA zuwa AP kuma an tsara shi don nemo wuraren samun damar da ke goyan bayan 802.11ba. Wannan filin kuma ya ƙunshi tsawon firam idan ya wuce 48 ragowa. - ID
Dangane da nau'in firam ɗin, yana iya gano AP, ko STA, ko ƙungiyar STAs waɗanda aka yi nufin wannan firam ɗin. (Ee, zaku iya tada na'urori a cikin ƙungiyoyi, ana kiranta farkawa na rukuni kuma yana da kyau sosai).
- Nau'in Dogara (TD)
Fage mai sassauƙa sosai. A ciki ne za a iya watsa ainihin lokacin, sigina game da sabuntawar firmware / daidaitawa tare da lambar sigar, ko wani abu mai amfani wanda ya kamata STA ya sani.
- Filin Checksum Frame (FCS)
Komai yana da sauki a nan. Wannan shi ne checksum
Amma don fasahar ta yi aiki, bai isa kawai aika firam a cikin tsarin da ake buƙata ba. Dole ne STA da AP su yarda. STA tana ba da rahoton sigoginta, gami da lokacin da ake buƙata don fara PCR. Duk shawarwarin yana faruwa ta amfani da firam na 802.11 na yau da kullun, bayan haka STA na iya kashe PCR kuma shigar da yanayin kunna WUR. Ko watakila ma samun ɗan barci, idan zai yiwu. Domin idan akwai, to yana da kyau a yi amfani da shi.
Na gaba yana zuwa ɗan ƙarin matsi na sa'o'i milliamp masu daraja da ake kira WUR Duty Cycle. Babu wani abu mai rikitarwa, kawai STA da AP, ta hanyar kwatankwacin yadda yake don TWT, sun yarda akan jadawalin barci. Bayan wannan, STA galibi yana barci, lokaci-lokaci yana kunna WUR don sauraron "Shin wani abu mai amfani ya zo mini?" Kuma kawai idan ya cancanta, yana farkawa babban tsarin rediyo don musayar zirga-zirga.
Canza yanayin sosai idan aka kwatanta da TWT da U-APSD, ko ba haka ba?
Kuma yanzu wani muhimmin nuance wanda ba ku yi tunani nan da nan ba. WUR ba dole ba ne ya yi aiki a mitar daidai da babban tsarin. Akasin haka, yana da kyawawa kuma yana ba da shawarar cewa yayi aiki akan wani tashar daban. A wannan yanayin, aikin 802.11ba ba ta kowace hanya ta tsoma baki tare da aikin hanyar sadarwa kuma, akasin haka, ana iya amfani da shi don aika bayanai masu amfani. Wuri, Lissafin Maƙwabta da ƙari a cikin wasu ƙa'idodin 802.11, misali 802.11k/v. Kuma menene fa'idodin buɗewa don cibiyoyin sadarwar Mesh ... Amma wannan shine batun wani labarin dabam.
Amma ga rabo na daidaitattun kanta a matsayin takarda, to . Wato, a wannan shekara za mu iya tsammanin ainihin ma'auni ko aƙalla aiwatarwa na farko. Lokaci ne kawai zai nuna yadda yaduwar za ta kasance.
Kamar haka... (c) .
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source: www.habr.com