telekomunikacijų standartus reguliuoja ITU, Europoje ETSI, USA FCC
1979 WARC rezervavo spektrą 892MHZ tarp 960MHZ
standarai
analoginiai, nmt, amps, tacs
nmt 450 naudojo nuo 420Mhz iki 490Mhz juostą, 180 arba 225 radijo kanalai
nmt 900 naudojo dazhniu juosta nuo 890 iki 960, viso 1000 kanalų
amps nuo 824MHz iki 894MHz 832 kanalai
tacs 890MHz 960MHz
etacs 872MHz 950MHz
skaitmeninia gms, damps, pdc
gsm 900MHz, vėliau gsm 1800MHz, dar vadinams DCS1800
damps sudarytas iš is 54 is 136 is 95
STRUCTURE AND COMPONENTS
cell network: MS, BTS, BSC, HLR ir VLR
GSM system: MS, base station sub system, network and switching ss, operational ss
Base station ss: BTS, BSC
network and switching ss: MSC, VLR, HLR, EIR, AUC
basic architecture
MS, BS, MSC, database
MSC funkcijos
setting up and controlling calls
handover control
location updating
signaling to and from MS
MSC integruojamas su VLR
GSM structure
MS with SIM
BS sub system (BTS ir BSC)
Network and switching sub system (MSC, GMSC, HLR, VLR, EIR, AUC)
Operation sub system
TRANSMITING
GSM naudoja GAUSIAN MINIMUM SHIFT KEYING moduliacijà
GSM iðkyla tokie trukdþiai: laiko dispersija, ty tas pats signalas pasiekia imtuvà skirtingais laikais, sunku suprast signalø eiliðkumà. laikinis vëlavimas, atsiranda MS tolsant nuo stoties.
ðitiems trukdþiams paðalint naudojamos adaptive equalisation - lygintuvas kompensuoja laiko disperijà. timing advance - MS yra liepiama siøsti info anskèiau nei priskirtam time slot, taip iðvengiama time delay. frequency hopping - reguliariai keièiamas daþnis
FM moduliacija
perduodama balso duomenys 300Hz- 3400Hz
SAT 5970Hz 6000Hz 6030Hz
8kHz signalling tone
Control data is transmitted using FSK at 8kb/s
GMS data rate 13kbps, detection and error connection coding 22,8kbps ciphering dar prideda duomenu. interleaving- ishrenkami besikartojanys bitai. burst formating - kiekvienos 20ms kalbos suformatuoja á 8 half bursts, iðëjimas yr 33kb/s, kart aðtuoni timeslotai, tg 270kbps
TDMA
Dazhnis kas 200kHz iðskirstomas, uplink downlink kas 45MHz, tada sudalinama á 8 time slotus, todël gali vytk 8 pokalbiai
CODING
PCM naudojama PSTN konvertuot analoginá signala 300Hz 3400Hz á digitaliná data rate 64kbps
susideda ið sampling, quantizing ir coding procesø. visgi tai labai neefektyvu, todël ið tikrøjø yra perduodama spektro filtø parametrai
codavimas nuo klaidø padidina talpà kanalo, nors jis ir prideda papildomø bitø, bet galima naudot þemesná daþná, maþesná spektrà
ACCESS
TDMA (gsm kas 200kHz, analog FDMA (uplink downlink kas 25Mhz, CDMA
analog systems
Control channel FOCC 40bits words, RECC 48bits words
voice channels fvc, rvc
digital systems
time slot kartojimasis physical channel
vienodi time slotai - logical channel
SWITCHING
switching - connecting functional units. MSC - general switching element.
circuit swithing (time-space-time switching)
MSC susidaro ið digital switch matrix ir procesoriaus
SIGNALING
exchange of information. between MS and network, network exhcange, cellular between PSTN network.
signal system no 7 (app part, user par, telephony user part, message transfer part, ISDN user part)
analog system - digital control channel, signaling messages - page, voice channel designation, system parameter overhead,
digital systems - synchro channels, paging and access channels
signaling protocols: LAPDm - MS to BTS , LAPD BTS to BSC, MTP 2 - BSC to MSC
SS no 7
susidaro ið Signalling point (pvz HLR, VLR) ir signalling transfer point
allocation of signaling channel
a dials b
MS sends request for SDCCH over the RACC. BSC allocates an SDDCH for MS and identifies over a AGCCH. MS is marked busy in VLR. security functions processed over SDCCH. The MSC asks to allocate a TRAFFIC channel
signalling systems and protocols
in analogue networks control info is transmitted in words (28) bits.
signalling messages
*page
*voice channel designation
*system parameter overhead message
ms to bts uses LAPDm
bts to bsc uses LAPD
BSC to MSC uses MTP level 2
MSC to PSTN ss no 7, R2, national
IUT-T Signalling System no 7 consists of App parts
(generates messages for mtp), User parts (generates messages to ISND or PSTN), Message Tranfsfer
LINKING NETWORKS
connecting with PSTN, ISDN, PLMN, PSPDN, CSPDN.
*involves analog to digital conversion
*echo problem = ocours when theres enough delay present in the call
MAINTENANCE OPERATIOAN MANAGMENT
centralizuota kontrole naudojama, taip saugiau, pigiau, greichiau, patikimiau.
ish distributed strukturos persitvarke i central, nes reikejo remote access, security pagerint, atpigint, statisticas vest, controle patogesne. distributed dirbdavo daugiau zhmoniu, tai neefektyvu.
CELL PLANNING
*system requirements (available frequency band, grade of service, capacity, coverage, speech quality, cost, system growth capability)
*nominal cell plan (cell structure, modell of cell grid, channel allocation. cell data, channel loading plan, bs locations)
*surveys (exact location, space for equimpemn, cable runs, power facilities, contract with owner, radio measurments)
*system desgin(dimensions of BS, MSC
*implementation and system tuning(changing parametrers,ir t.t
*system growth
traffic per subscriber (a=nxt/3600 [erlang] A = traffic deman, n = number of calls, t =time per hour
