Internet Access by GSM & GPRS

Transcription

1 Kmmunikatinsnetz Franken e.v. Internet Access by GSM & GPRS At the end f the wired universe... Maximilian Riegel access-by-gsm.ppt-1 ( )

2 Kmmunikatinsnetz Franken e.v. Prlg When yu like m slw links m expensive cnnectin fees m cmplicated installatin and cnfiguratin m... just like yu have dne it Ô94 & Ô95 in the wired Internet then yu are right here: Welcme back int the future! access-by-gsm.ppt-2 ( )

3 Kmmunikatinsnetz Franken e.v. Outline GSM system verview Circuit switched data Internet access ver GSM High Speed Circuit Switched Data GPRS system verview Cmparisn f CSD, HSCSD and GPRS Links access-by-gsm.ppt-3 ( )

4 Kmmunikatinsnetz Franken e.v. GSM (Glbal System fr Mbile cmmunicatins) GSM standard was adpted by ETSI in 1991 Nw used in cuntries by abut 400 mi users Benefits: m Supprt fr internatinal raming m Distinctin between user and device identificatin m Excellent speech quality m Wide range f services m Interwrking (e.g. with ISDN, DECT) m Extensive security features Services: m Telephny m Asynchrnus and synchrnus data services (2.4/4.8/9.6 kbit/s) m Access t packet data netwrk (X.25) m Telematic services (SMS, fax, videtext, etc.) m Many value-added features (call frwarding, caller ID, vice mailbx) access-by-gsm.ppt-4 ( )

5 Kmmunikatinsnetz Franken e.v. GSM system architecture BTS BTS BSC BTS PLMN access BSC BTS MSC TDM HLR VLR AUC PLMN cre MSC EIR IN PSTN (ISDN) PLMN Public Land Mbile Netwrk BTS Base Transceiver Statin BSC Base Statin Cntrller MSC Mbile Switching Center PSTN Plain Standard Telefn Netwrk HLR Hme Lcatin Register VLR Visited Lcatin Register AUC Authenticatin Center EIR Equipment Identity Register IN Intelligent Netwrk access-by-gsm.ppt-5 ( )

6 Kmmunikatinsnetz Franken e.v. GSM radi interface GSM900 Up: MHz Dwn: MHz GSM1800 Up: MHz Dwn: MHz GSM1900 Up: MHz Dwn: MHz One channel transfers 114 infrmatin bits / time slts One channel ccupies 24 time slts / 120ms One channel has a raw data rate f 22,8 kbit/s (full rate) Half a channel might be used fr ne cnnectin (half rate) The bearer service fr data cmmunicatin prvides 9,6 kbit/s access-by-gsm.ppt-6 ( )

7 Kmmunikatinsnetz Franken e.v. GSM CSD (Circuit Switched Data) nn-transparent Mst widely used: nn-transparent data rate f 9.6 kbit/s. m Errr crrectin and flw cntrl ("nn-transparentò) m RTT is typically arund 0.5s (GSM1800) and 1s (GSM900) Nn-transparent mde utilises a special GSM netwrk-based errr crrectin facility called "Radi Link Prtcl" (RLP) that ensures mre rbust transmissin. Transmitter gets an acknwledgement frm the receiver that data has been errr-free received. "frward crrectin" technique is used t ensure uninterrupted data transmissin thrughut. Call can be started n V.110 (link a ISDN data call; fast set-up) r n V.32.( like in a PSTN mdem; slw set-up). RLP causes a small additinal delay. access-by-gsm.ppt-7 ( )

8 Kmmunikatinsnetz Franken e.v. GSM CSD (Circuit Switched Data) transparent N GSM errr crrectin supplied ver the air interface. Standard fr G3 fax transmissin is a transparent prtcl. Mst GSM netwrks supprt bth nn transparent and transparent data cmmunicatins. Can be started n V.110 (link a ISDN data call) r n V.32.( like in a PSTN mdem). Transparent mde causes nly minimal delay but des nt guarantee errr free transmissin. Real time requirements are better fulfilled by transparent mde. access-by-gsm.ppt-8 ( )

9 Kmmunikatinsnetz Franken e.v. Cnfiguratin: CSD AT Strings Fr ISDN cnnectin use the fllwing initialisatin strings: AT+CBST=71,0,1 (fr mst newer handsets) The +CBST string is defined as "select bearer service type" in GSM The full definitin is: AT+CBST=<speed>,<name>,<ce> <speed> Meaning 0 autbauding V V V34 (HSCSD 1 timeslt) V34 (HSCSD 2 timeslts) V34 (HSCSD 2 timeslts) V V110 (HSCSD 1 timeslt V110 (HSCSD 2 timeslts) V110 (HSCSD 2 timeslts <name> 0 1 <ce> Meaning data circuit asynchrnus data circuit synchrnus Meaning transparent nn-transparent bth, transparent preferred bth, nn-transparent preferred access-by-gsm.ppt-9 ( )

10 Kmmunikatinsnetz Franken e.v. Mbile Internet access in Germany Mst mbile phnes are equipped with mdem functinality Cnnectin t the cmputer might be realized by cable r IrDA Getting mbile internet access needs just the cnfiguratin f a new internet cnnectin n the cmputer. T-D1 D2-privat e-plus Viag Interkm Phne number Username Passwrd will be prvided after sign up dnôt care dnôt care empty empty g@mbil.de internet Cst per minute [DM] (22-06) 0.39 (06-22) 0.19 (18-09) 0.39 (09-18) 0.29 Mre ecnmic cnnectin fees might be pssible by lcal dial-in numbers ( Mst MNOs prvide direct dial-in numbers fr ther nline-services. access-by-gsm.ppt-10 ( )

11 Kmmunikatinsnetz Franken e.v. HSCSD (High Speed Circuit Switched Data) Maximum user data rate per GSM time slt 14.4 kbit/s m New cding scheme with less errr prtectin capabilities m 14.4 kbit/s bearer nt pssible at GSM900 Up t fur time slts can be allcated fr ne data call. Bth, 9.6 kbit/s and 14.4 kbit/s bearers, can be used. m max kbit/s with 9.6 kbit/s bearer m max kbit/s with 14.4 kbit/s bearer Nn-transparent service: m Number f timeslts can be changed during the call m Asymmetric allcatin pssible Transparent service: m Fixed number f timeslts during a particular call Simple upgrade f existing GSM netwrks access-by-gsm.ppt-11 ( )

12 Kmmunikatinsnetz Franken e.v. Cnfiguratin: HSCSD AT Strings The mst cmmn HSCSD cnfiguratins are: m AT+CHSN=2,1,1,8 want single slt 14k4 m AT+CHSN=2,1,1,12 want single slt 14k4 but will accept 9k6 m AT+CHSN=4,2,2,8 want duble slt 28k8 m AT+CHSN=4,2,2,12 want duble slt 28k8 but will accept 19k2 The actual frmat f the cmmand is defined in GSM07.07 as: AT+CHSN=<wAiur>,<wRx>,<tpRx>,<cdings> <wrx> and <tprx> are the wanted and maximum number f receive timeslts. <wrx>=0: the handset shuld calculate the crrect value frm <waiur> and <cdings>. <tprx>=0: the handset will nt request a change in timeslts allcated during the call. <waiur> Meaning 0 0 default - take speed frm AT+CBST <cding> 1 4 Meaning 4800 full rate data traffic timeslt 9600 full rate data traffic timeslt full rate data traffic timeslt These values are additive, e.g. 12 means 9600 r are acceptable access-by-gsm.ppt-12 ( )

13 Kmmunikatinsnetz Franken e.v. GPRS (General Packet Radi Service) Designed fr bursty data traffic m Stays cnnected withut wasting radi resurces m intrductin f packet switching t the GSM netwrk m Reuse f the GSM radi netwrk infrastructure m Multi slt cmbining traffic technlgy fr bandwidth-n-demand Up t 4 (theretically 8) timeslts fr uplink and dwnlink 4 different cding schemes CS with different capacities. m Capacity ranges frm 9.05 kbit/s (CS 1) t 21.4 kbit/s (CS 4) m Theretical maximum speed is 21.4 x 8 = kbit/s Dynamic ptin f GPRS: m GSM vice traffic is priritised m Packet switched data traffic nly n timeslts nt in use fr vice => Reuse f therwise wasted bandwidth access-by-gsm.ppt-13 ( )

14 Kmmunikatinsnetz Franken e.v. GPRS: dynamic allcatin f time-slts access-by-gsm.ppt-14 ( )

15 Kmmunikatinsnetz Franken e.v. GPRS system architecture BTS BTS BSC BTS PLMN access BSC SGSN BTS MSC TDM HLR VLR AUC PLMN cre MSC EIR GGSN IN PSTN (ISDN) Internet SGSN (Serving GPRS Supprt Nde) Packet data handler twards BSC prviding authenticatin, mbility management, lgical link management, packet ruting and transfer Interwrking with the HLR and the GPRS packet cntrl unit lcated in the BSC r a BTS. GGSN (Gateway GPRS Supprt Nde) Interwrking functin with external packet data netwrks. Acting as an access server Setting up the lgical link t the mbile statin thrugh the SGSN. Translatin f data frmats and signalling prtcls access-by-gsm.ppt-15 ( )

16 Kmmunikatinsnetz Franken e.v. Bandwidth - delay cmparisn CSD HSCSD GPRS Bandwidth (Up / Dwn) [kbit/s] 9.6 / / / 57.6 CS1: 9.05 / 36.2 CS2: 13.4 / 53.6 CS3: 15.6 / 62.4 CS4: 21.4 / 85.6 Delay 1s (GSM900) 0.5s (GSM1800) 1s (GSM900) 0.5s (GSM1800) QS class 1: 128B: mean 0.5s (95% 1.5s) 1kB: mean 2s (95% 7s) QS class 2: 128B: mean 5s (95% 25s) 1kB: mean 15s (95% 75s) QS class 3: 128B: mean 50s (95% 250s) 1kB: mean 75s (95% 375s) access-by-gsm.ppt-16 ( )

17 Kmmunikatinsnetz Franken e.v. Mbile Netwrks are expensive Transfer cst/duratin f an 1 Mbytes.ppt/.dc/.xls File Û min 4 min 5 sec 10 1 lgarithmic scale Transfer-Cst [Û] Duratin [min] ,6% 0,1 0 GPRS GSM-HSCSD WLAN* 0,01 GPRS GSM- HSCSD WLAN * based n current IP vlume prices f 40Û /GByte. Time based pricing results in similar csts, e.g. MbileStar Pulsar pricing plan: $0,10/min access-by-gsm.ppt-17 ( )

18 Kmmunikatinsnetz Franken e.v. Links ãinternet-zugang aus den MbilfunknetzenÒ ãinternet zum OrtstarifÒ Ging nline with the cmmunicatr (als very infrmative fr nn-nkia Cmmunicatin users) ãmit Laptp und Handy ins InternetÒ Overview f the Glbal System fr Mbile Cmmunicatins Mbilfunk FAQs access-by-gsm.ppt-18 ( )