https://www.itu.int/rec/T-REC-G.993.2 https://math.feld.cvut.cz/gollova/tik/TI/TI_prednasky.pdf https://cs.qaz.wiki/wiki/Shannon%E2%80%93Hartley_theorem https://cs.qaz.wiki/wiki/Shannon%E2%80%93Hartley_theorem ------------------- teorie informace, spousta rovnic http://cmp.felk.cvut.cz/~navara/psi/kody_pr.pdf https://www.earchiv.cz/b01/b1000011.php3 Peterka uvádí odstup signál/šum 30 dB Peterka tam má i mnoho jiných dobrých věcí https://www.earchiv.cz/b20/b0824001.php3 ---------------------------------- Doporučení ITU G.993.1 bandplan strana 96 - ANNEX A má to tři varianty bandplanu - kmitočtového plánu Annex E str. 97 Evropa A nebo B Bandplan A as specified in Annex A or Bandplan B as specified in Annex B may be used with restrictions specified in [ETSI]. DS - downstream - je na nižších kmitočtech US upstream strana 22 - skrambler a FEC 8.5.5.1 strana 19 crc(D)= M(D) D8 modulo G(D) where: M(D) = m0Dk–1 + m1Dk–2 + … + mk–2D + mk–1 is the message polynomial G(D) = D8 + D4 + D3 + D2 + 1 is the generating polynomial crc(D) = c0D7 + c1D6 + … + c6D + c7 is the check polynomial AHA, tak voni to, co my nazýváme u polynomu x , nazývají D !!!!! a D na 8 - to je přidej osm nul malé k počet bitů zprávy strana 22 9.2.1 Multi-carrier modulation The modulation shall use a maximum number of sub-carriers equal to NSC = 2 na (n+8), where n can take the values 0, 1, 2, 3, 4. Disjoint subsets of the NSC sub-carriers shall be defined for use in the downstream and upstream directions. These subsets are determined by the frequency plan (see 6.1). The exact subsets of sub-carriers used to modulate data in each direction shall be determined during initialization and shall be based on management system settings and the signal-to-noise ratios (SNRs) of the sub-channels. In many cases the number of sub-carriers used in a direction will be less than the maximum number allowed by the partitioning. takže : nejméně nosných je 256 nejvíce nosných je 2 na 12 4096 nosných strana 23 - číslo dole na stránce 9.2.1.1 Tone spacing The frequency spacing, Δf, between the sub-carriers shall be 4.3125 kHz, with a tolerance of 50 ppm. The sub-carriers shall be centred at frequencies f = k Δf. The tone index k can take the values k = 0,1,2, …, NSC – 1. 9.2.1.2 Data sub-carriers Transmission may take place on up to NSC – 1 sub-carriers, since DC is not used. The actual number of sub-carriers used may be lower than this maximum number. The lower limit depends on the presence of amateur radio-frequency bands and the required notching in these bands, the POTS or ISDN splitter, PSD masks, implementation-specific filters and the services to be provided. strana 106 F.2.3.2.1 Test frequency band Three bands of frequencies are used for test. • Voiceband frequencies: DC and 0.2 kHz to 4.0 kHz (0.2 kHz ≤ f ≤ 4.0 kHz) • ISDN band frequencies: DC and 4.0 kHz to 320 kHz (4.0 kHz < f ≤ 320 kHz) • VDSL band frequencies: 640 kHz to 12 MHz (640 kHz ≤ f ≤ 12 MHz) strana 55 dole na stránce It signifies that the band between 25 kHz and 138 kHz shall be used for upstream (VTU-R → VTU-O) transmission. takže vono to může použít i kmitočty pod 138 kHz strana 164 I.2.2.3.2.1 Symbol rates and carrier frequencies All available values of symbol rates (SR) for both carriers in both downstream and upstream directions shall be multiples of the Basic Symbol Rate (BSR): SR = s × BSR ITU-T Rec. G.993.1 (06/2004) 165 where s is an integer, BSR = 33.75 kBaud. The carrier signal frequencies fC shall be an integer multiple of BSR/2: fC = 0.5 × BSR × k [kHz] where k is an integer. The resulting fC shifting granularity is equal to 16.875 kHz. něco o rychlostech https://www.dsl.cz/clanky/namerene-rychlosti-internetu-na-dsl-cz-v-prosinci-2023 https://www.dsl.cz/clanky/rychlosti-mobilniho-internetu-na-dsl-cz-v-listopadu-2023 Teorie Vodrážka http://www.elektrorevue.cz/clanky/01031/index.html neco o profilech https://www.digilidi.cz/testujeme-vdsl-vcetne-rychleho-profilu-35b-na-modemu-asus-dsl-87vg https://www.earchiv.cz/l224/gifs/S3620.pdf strana 28 rzclosi na vzdálenosti - ale je to asi staré VDSL ve Zlíně https://avonet.cz/24917-faq-xdsl-adsl-vdsl rzchlosti https://www.root.cz/clanky/terminator-od-cetin-vdsl-bonding-s-rychlosti-az-250-mbit-s/ reklamní konference CETINu https://www.isp-konference.cz/sites/default/files/obsah/konference/program/soubory/cetin_3.pdf Kvalita služeb https://www.profiber.eu/files/prednasky/15.3.2013_D1_Pavel_Kosour,_Radek_Kocian_-_Kvalita_sluzeb_VDSL2.pdf