tel pratybos 3

Standartai
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