nlast week n Looked at air interface of 1G and 2G cellular networks n Both are primarily circuit switched n We briefly consider this today

Transcription

1 Preview 2 Lecture 3 Overview of Wireless Systems (2) Last week Looked at air iterface of 1G ad 2G cellular etworks Both are primarily circuit switched I GS, the cotrol sigalig uses packets ad a protocol stack We briefly cosider this today 3G, 4G, WLANs ad WPANs are more packet orieted Brief overview today ostly Circuit Switched 1980s 1990s 2000s 2010s 3 Geeric Architecture 2G WWANs Wide Area Networks Local ad Persoal Area Networks 1G Aalog F/FDA Idepedet obile Data Aalog Cordless Phoe F/FDA IEEE DSSS/FHSS PSTN Access Iteret Access WLAN WPAN 2G Digital TDA/ CDA Cellular Overlay CDPD Circuit Switched Digital Cordless TDA IEEE b CCK/DSSS IEEE Bluetooth/FHSS 3G Cellular CDA IEEE a/g OFD IEEE UWB/OFD/DSSS IEEE Zigbee/DSSS DSS/FHSS DECT - TDA 4G LTE-Advaced OFDA/IO 4G LTE OFDA/IO 4G Wiax OFDA/IO IEEE OFD/IO 60 GHz Gigabit UWB IEEE BAN Radio Level Network Level aagemet Level Visitor Database Home Database Autheticatio Ceter The Iteret or PSTN Poit of Access ViD HoD AuC OC ER RNC SC 4 RNC obile Statio Operatio & aiteace Ceter Equipmet Register obile Switchig Ceter Radio Network Cotroller

2 5 2G Cellular Network Architecture BTS- Base Trasceiver Subsystem BSC - Base Statio Cotroller SC - obile Switchig Ceter BTS - Base Trasceiver Subsystem CO - Cetral Office VLR - Visitor Locatio Register SS 7 - Sigalig System 7 6 Terms ad termiology obile Statio (S) obile Termial T, obile Ed System -ES, obile Node N, obile Device, Hadheld Device, Wireless Device, etc. Poit of Access Base Statio (BS), Base Trasceiver Subsystem (BTS), obile Data Base Statio (DBS), Access Poit (AP), Node B, E-Node B Radio Cotroller Base Statio Cotroller BSC, Radio Network Cotroller RNC obile Cotrol Ceter obile Switchig Ceter SC, obile Data Itermediate System D-IS, Gateway GPRS Support Node GGSN Visitig Database Visitig Locatio Register VLR, obile Servig Fuctio SF, Servig GPRS Support Node SGSN, Foreig Aget FA Home Database Home Locatio Register HLR, obile Home Fuctio HF, GPRS Register GR, Home Aget HA Not all elemets from the geeric architecture exist i all techologies & the exact fuctioality of the elemets may be differet 7 obile Statio or Device We will call this obile Statio or S Irrespective of what it is Form factor ad capabilities Has to be light weight, durable, have log battery life ad yet be capable of performig complex tasks Eergy efficiet desig of software ad protocols Usability User characteristics (size, dexterity, kowledge, etc.) Eviromet characteristics (temperature, degree of mobility, etc.) Device Characteristics Start up time Data itegrity ad security CPU speed ad memory size Power supply User iterface (keypad, figer, stylus, voice) 8 obile Devices Pager Receive oly Tiy displays Simple text messages Two way pagers RF-ID tags, Sesors, embedded cotrollers Smartphoes Graphical displays ad touchscrees Almost full WWW Apps! Regular cellphoes Voice, data Simple text displays Simplified WWW Laptops Fully fuctioal Stadard applicatios Tablets ad etbooks Tiy or virtual keyboard CPU weak Log battery life Performace ad Cost?

3 Fuctioality of Elemets (I) 9 Base Statios (BS) 10 Poit of access The physical radio trasceiver Creates the air iterface Trasmits sigals to Ss Receives sigals from Ss Ivolved i multiplexig o the lik edium access Radio Network Cotroller Agai lik level aages the air iterface Which RF carrier should I tue to? What trasmit power level should I use? Is the frequecy carrier I wat to use capable of providig acceptable quality? Whe should I make a hadoff? Provides radio chaels betwee mobile uits ad etwork Pico-cells : (idoor 0-.5 Km) support 8-20 chaels icro-cells: (outdoor 0-1 Km), acro-cells: (1-30 Km) Base Statios ad Radio Network 11 obile Switchig 12 Cotrollers Base Trasceiver Subsystem (BTS) Houses radio uits Base Statio Cotroller (BSC) aages a cluster of BS, chael assigmet, hadoff, power cotrol, some switchig, etc Ceter obile Switchig Ceter (SC) Provides switchig fuctios, coordiates locatio trackig, call delivery, hadoff, iterfaces to HLR,VLR, AUC, etc. Size of cetral office switch BTS BSCs

4 Fuctioality (II) 13 Home ad Visitor Databases 14 obile Switchig Ceter aages mobility of devices Routes voice calls or packets to ad from Ss Keeps track of the locatio of the Ss Locatio meas i which cell or group of cells the S may be located i.e., which poits of access may be probable cadidates for pigig the S How does it do this? Usig the home database ad visitig database Esures security Uses the autheticatio ceter ad equipmet registers to autheticate the S ad to prevet fraudulet/stole devices from usig the etwork Accoutig ad Billig Operatios ad maiteace ceter Home Locatio Register (HLR) Specialized database server cotais billig ifo, service profile ad geeral locatio of a mobile user Visitor Locatio Register (VLR) Similar to HLR cotais locatio of users ad their service profile of all users i a metro type area Protocol Stack TCP/ (Simplified Slide modified from Agrawal 15 Layer ames ad tasks 16 Web Browsig) essage from Alice s Browser TCP Segmets Created datagrams carry TCP segmets Etheret i Alice s PC creates frame Etheret i router gets frame, checked for errors Etheret cable carries sigal to edge router There is a structured flow betwee layers at each ed Looks at DA for routig Trasport Edge router receives datagram Puts it i Etheret frame Web server process gets message TCP segmet is recovered, assembled datagram is picked up from frame Etheret i server gets frame, checks for errors Cable carries the sigal represetig Etheret frame to server machie There is a oe-to-oe correspodece betwee layers i the two ed poits Layer Layer ame Networkig task Header iformatio umber 5 Applicatio Specify user eeds, creates message User commads 4 Trasport Segmetatio ad reassembly of data segmets, sometimes reliable trasfer & speed matchig 3 Network Idetifyig ad locatig destiatio, best effort delivery of datagrams 2 Data-lik Reliable delivery of frames over a lik, Error cotrol 1 Physical Sigalig, movig idividual bits based o medium Sequece umbers Address Error check Usually oe, but i WiFi there is a header

5 Slide modified from Kurose-Ross segmet datagram H frame H l H Bob H l H H message Alice destiatio applicatio trasport etwork lik physical source applicatio trasport etwork lik physical H l H H Ecapsulatio Sigal Uses lik or AC address at frame level lik physical etwork lik physical Uses address at datagram/etwork level H switch router 17 Cotrol Sigalig ad User Data (Voice) i 2G Systems Cotrol Sigalig essages for settig up the voice call essages for mobility maagemet essages for radio resources maagemet Other sigalig (SS is carried o sigalig chaels) User data is primarily voice i 2G Sometimes called voice traffic Digitized ad carried i circuits set up by the cotrol sigals 18 Cotrol Sigalig Protocol 19 Example: obile Iitiated Call i 2G 20 Layer 3 Layer 2 Layer 1 Stack 2G GS C RR LAPD m Radio LAPD m Radio RR LAPD 64 kbps LAPD 64 kbps RR SCCP TP 64 kbps C RR SCCP TP 64 kbps S BTS BSC SC Air Iterface C: Coectio aagemet; : obility aagemet; SCCP: Sigal Coectio Cotrol Part RR: Radio Resource aagemet; TP: essage Trasfer Part; LAPD: Lik Access Protocol-D GS essage Name Category 1. Chael Request RR Traffic Chael = Circuit Security Related 2. Immediate Assigmet RR 3. Call Establishmet Request C 4. Autheticatio Request 5. Autheticatio Respose 6. Cipherig Commad RR 7. Cipherig Ready RR 8. Sed Destiatio Address C 9. Routig Respose C 10. Assig Traffic Chael RR 11. Traffic Chael Established RR 12. Available/Busy Sigal C 13. Call Accepted C 14. Coectio Established C 15. Iformatio Exchage voice bits This is all cotrol sigalig

6 Physical Vs Logical Chaels 21 2G GS - TDA/FDA/FDD 22 A 200 khz frequecy carrier is a physical chael A time slot used for voice traffic is a logical chael There are several cotrol chaels that are logical chaels i GS They are used for call set up, maagig mobility, hadlig radio resources, etc. guard space GS TDA frame Hz 124 chaels (200 khz) dowlik Hz 124 chaels (200 khz) uplik higher GS frame structures GS time-slot (ormal burst) tail user data S Traiig S user data tail 3 bits 57 bits 1 26 bits 1 57 bits 3 time guard space ms µs 577 µs Show physical ad logical chaels Circuit to Packet Switched 1980s 1990s 2000s 2010s G Systems ad Data 24 Wide Area Networks Local ad Persoal Area Networks 1G Aalog F/FDA Idepedet obile Data Aalog Cordless Phoe F/FDA IEEE DSSS/FHSS PSTN Access WLAN WPAN 2G Digital TDA/ CDA Cellular Overlay CDPD Digital Cordless TDA IEEE b CCK/DSSS IEEE Bluetooth/FHSS 3G Cellular CDA DSS/FHSS DECT - TDA Packet Switched IEEE a/g OFD IEEE UWB/OFD/DSSS IEEE Zigbee/DSSS 4G LTE-Advaced OFDA/IO 4G LTE OFDA/IO 4G Wiax OFDA/IO IEEE OFD/IO 60 GHz Gigabit UWB IEEE BAN 2G Systems provide slow speed data service 9.6 Kbps 14.4 Kbps 2.5G Attempt to improve data services from 2G ad build customer base for wireless data service GPRS, HSCSD, cdma2000-1x -> islabeled as 3G Basically overlay etwork of data service o 2G etworks ax data rate 57 Kbps 150 Kbps, typical data rates Kbps similar to dialup modem service obile Data Cellular Digital Packet Data (CDPD) -> Overlay o APS Geeral Packet Radio Service (GPRS) -> Overlay o GS Iteret Access

7 GPRS System Architecture 25 Servig GPRS Support Node (SGSN) 26 S S BTS BTS SGSN BSC BSC G GGSN HLR D Itra PLN backboe etwork ( based) G p G i New Etities GGSN SGSN It cotrols access to Ss that may be attached to a group of BSCs This is called a routig area (RA) or service area of the SGSN It is resposible for delivery of packets to the S i its service area ad from the S to the Iteret It also performs the logical lik maagemet, autheticatio, ad chargig fuctios U m A SC Gateway GPRS Support Node (GGSN) It acts as a logical iterface to the Iteret aitais routig iformatio related to a S, so that it ca route packets to the SGSN servicig the S It aalyses the packet data etwork () address of the S ad coverts it to the correspodig Iteratioal obile Subscriber Idetity (ISI) umber 27 GPRS Sigalig Plae GPRS employs out of bad sigalig i support of actual data trasmissio Sigalig betwee SGSN, HLR, VLR, EIR is similar to GS ad exteds oly the GPRS related fuctioality Based o Sigalig System 7 Betwee the S ad SGSN, a GPRS mobility maagemet ad sessio maagemet (G/S) protocol is used for sigalig purposes 28

8 GPRS Trasport Plae (two 29 3G (UTS) 30 tuels) Tuels Applicatio SNDCP LLC RLC AC Radio RLC AC Radio TLLI LLC Relay BSSGP Frame Relay L1 SNDCP BSSGP Frame Relay S BSS SGSN GGSN LLC L1 GTP TCP/ L2 L1 TID GTP TCP/ L2 L1 Gi Network architecture adds to the 2G architecture Similar core etwork as 2G systems WCDA based air iterface True QPSK modulatio Wider carrier badwidths 5 Hz 3.84 cps BSC/RNC CO SC PSTN CO CO VLR SGSN SC VLR BSC/RNC /SS 7 Home Locatio Register GGSN SGSN BSC/RNC Equipmet Auth. Idetity Ceter Register BTS/Node-B SNDCP: Subetwork Depedet Covergece Protocol BSSGP: BSS Gateway Protocol GTP: GPRS Tuelig Protocol SGSN ad GGSN Data! What is UTS? 31 Summary of WCDA 32 UTS stads for Uiversal obile Telecommuicatios System 3G cellular stadard i Europe & Japa Outcome of several research activities i Europe Geerated trial systems ad basic uderstadig of WCDA Assisted the stadardizatio efforts ost of the stadardizatio work was focused i 3GPP 3GPP refers to the physical layer as UTRA UTS Terrestrial Radio Access There are two modes FDD ad TDD UTS ca support both GS-AP ad IS-41 core etworks A all- third alterative is available ow WCDA is somewhat differet compared to IS-95 It is a widebad direct sequece spread spectrum system Supports up to 2 bps usig Variable spreadig ulticode coectios The chip rate is 3.84 cps Approximate badwidth is 5 Hz Carrier spacig is o a raster of 200 khz Supports higher data rates/capacity Icreased multipath diversity (proportioal to chip duratio)

9 UTS Protocol Stack (simplified) Show oly for radio access part Top Cotrol sigalig Bottom User Data Voice is hadled usig circuit switchig Itricate maybe later 33 High Speed Packet Access (HSPA) HSUPA uplik ad HSDPA dowlik Packet data oly ore efficiet (less tuelig, local schedulig) akes use of Hybrid ARQ Combies erroeous frames with retrasmitted frames to achieve diversity Fast schedulig Istead of sigalig from the RNC, a ode B is allowed to make decisios o the maximum data rates that a S ca use to trasmit packet data Vedors implemet proprietary algorithms 34 Packet Data i UTS Vs HSPA 35 4G (LTE) 36 Radio Network Cotroller UE SGSN GGSN Node B Schedulig Radio Network Cotroller Logical Lik Tuel GPRS Tuel (a) Packet data i UTS UE Report Node B SGSN GGSN Chael Quality Sigle Tuel (a) Packet data i HSPA Iteret Iteret Differet etwork architecture to support packet based access Flatter! All core etwork that ca iterface better with techologies such as WiFi ad Wiax Use of OFDA as the medium access/modulatio scheme Udereath QPSK, QA Flexibility to deploy it i as little spectrum as 1.4 Hz ad as much as 20 Hz of spectrum Support for true broadbad

10 OFDA 37 Chael Badwidths Check actual BW! 38 Flexible resource allocatio i time ad frequecy Uit of allocatio: Physical Resource Blocks subcarrier LTE Dowlik, Wiax uplik ad dowlik frequecy S 8 S 7 S 6 S 5 S 4 S 3 S 2 S 1 Slot S 7 S 3 S 2 S 1 S 8 S 6 S 3 S 2 time Compare with APS, GS, IS-95, UTS ad Wiax Ca vary from 1.4 Hz to 20 Hz Resource Block (RB) 180 khz wide ad 0.5ms log 12 subcarriers spaced at 15 khz (24 at 7.5 khz possible later) Data rate limited by User Equipmet (UE) categories Chael BW (Hz) Resource Blocks Fuctioal Chages E-NodeB Does a lot more ow! (o RNC or BSC) Selectio of E, RR fuctios, Hadlig obility E Seds pages to e-nodebs Hadles security Idle state mobility S-GW Termiatio of user plae Switchig of user plae (mobility) 39 LTE Simplified Protocol Stack (Cotrol Iformatio) UE RRC PDCP RLC AC PHY E-NodeB RRC PDCP RLC AC PHY GTP S1 obility ad Sessio aagemet S1- bearer Layer 2 Layer 1 E S1- Bearer GTP Layer 2 Layer 1 Shaded stack is called the access stratum - AS, upper layers are called o-access stratum NAS RRC = Radio Resource Cotrol Icludes measuremets o sigals PDCP = Packet Data Covergece Protocol RLC = Radio Lik Cotrol 40 Radio Bearer

11 LTE Simplified Protocol Stack 41 Wireless Local Area Networks 42 ( Our Data ) E-NodeB UE S-GW PDN-GW Ed-to-Ed Betwee UE ad Service Ed-poit usig Bearer betwee PDN-GW ad UE that defies QoS () PDCP PDCP GTP GTP GTP GTP RLC RLC Iteret Note that there is o RRC here Used primarily i smaller areas Homes, campuses, coffee shops, busiesses Support commuicatio to mobile data users via wireless chael Stadards IEEE a, b, g,, ac, ad, stadard (wireless Etheret) The project was iitiated i 1990, the first complete stadard was released i bps, 2bps, 11bps, 54 bps, >100 bps rates Use Barker codes (spread spectrum), CCK, OFD, IO Ifrastructure based ad Ad-Hoc based etworks HERLAN 1 ad 2 AC PHY AC PHY Layer 2 Layer 1 Layer 2 Layer 1 Layer 2 Layer 1 Layer 2 Layer 1 Typically use ulicesed spectrum Radio Bearer Some WiFi Stadards 43 Geeric Architecture - WLANs 44 How about chaels? Stadard Spectrum US Data Rates Trasmissio (GHz) Scheme Base IEEE , 2 bps GFSK, FHSS Autheticatio Server The Iteret , 2 bps B/QPSK, DSSS LAN segmet (distributio system) Router m 1, 2 bps PP, IR a , bps OFD b , 2, 5.5, 11 bps CCK S-3 AP-3 S-1 AP-1 Basic Service Set (BSS) g bps OFD, CCK AP ad 5 GHz Up to 600 bps IO/OFD S ac 2.4 ad 5 GHz > 1 Gbps IO/OFD ad multi-user IO Exteded Service Set (ESS)

12 Protocol positio of IEEE Ad hoc etwork topology 46 mobile termial applicatio TCP fixed termial server ifrastructure etwork access poit applicatio TCP Distributed topology Devices commuicate betwee each other directly (like walkie-talkies) Characteristics Recofigurable etworks No eed for a wired ifrastructure Suitable for rapid deploymet LLC AC PHY LLC AC PHY AC PHY LLC AC PHY Need to discover commuicatig parties, services, methods of routig data, ad so o Ad Hoc WLANs 47 What is a persoal area 48 Ss commuicate i a peer-to-peer maer Sigle-hop: They have to be i rage of oe aother ost vedors support oly this optio ulti-hop: Ss ca act as relay odes HERLAN/1 supports this, but there are o real products S S Idepedet Basic Service Set (IBSS) i WLANs S etwork? Origis i the BodyLAN project iitiated by BBN i the early 1990s Networkig persoal devices sesors, cameras, hadheld computers, audio devices, etc. Rage of aroud 5 feet aroud a soldier Today: Networkig digital cameras to cell phoes to cameras to laptops to priters to

13 IEEE Some WPAN Stadards 50 Started i 1997 as a sub-group of IEEE Iitial fuctioal requiremets Low power devices Rage of 0-10m Low data rates ( kbps) Small sizes (0.5 cubic iches) Low cost ultiple etworks i the same area Up to 16 separate devices Techology/ Feature (Bluetooth) Frequecy 2.4GHz 2.4GHz - 868/915Hz odulatio FHSS/BPSK DSSS/QPSK AC TDA/TDD CSA/CA ax. data rate 1bps 20/40/250Kbps Device types Oe Full/Reduced Fuctio No. of chaels 79 (hopped) 26 ax. No. of devices 8 Up to Battery life Weeks oths Coverage 10 m 10/50m Topologies Star, peer-peer Star ad cluster-tree Coectio time 3-5s 30ms Geeric Architecture - WPANs 51 IEEE or Bluetooth 52 Slave Slave Slave aster Ad-hoc topology Bluetooth: A cell or picoet is defied by a aster device The master cotrols the frequecy hoppig sequece The master also cotrols the trasmissio withi its picoet Others Sesor etworks ( ), RF-IDs, mobile ad hoc etworks Operates i the same 2.4 GHz bads as IEEE b It employs frequecy hoppig spread spectrum Chaels are 1 Hz wide The modulatio scheme is GFSK for a raw data rate of 1 bps o the air A basic time slot is defied as 625 microsecods A Bluetooth packet ca occupy oe, three or five slots Sometimes a trasmissio is half a slot The frequecy is chaged every packet

14 ad Zigbee Full Fuctio Device Reduced Fuctio Device 54 Geeral Idea i /Zigbee Full fuctio device (FFD) Serves as a PAN coordiator (like a master) Ca route packets (relay) Reduced fuctio device (RFD) ostly i sleep mode ad commuicate mostly with a FFD Star etwork similar to Bluetooth Cluster-tree provides ability to have a mesh Star Network etwork with differet topologies Cluster-Tree Network 55 Example of /Zigbee Philips esh Hue 56 Ultrawidebad (UWB) etworked Accessible through Two defiitios by the FCC the Iteret Source: Example: What is the fractioal badwidth of a UWB device operatig betwee 3.1 ad 4.8 GHz? A radio sigal that has a istataeous badwidth greater tha or equal to 500 Hz A radio sigal with a fractioal badwidth ³ 0.2 where Aswer: 2 1.7/(7.9) = 3.4/7.9 = > 0.2 You ca thik of this as also beig W/fc where fc is the ceter frequecy ad W is the badwidth occupied The badwidth defiitio here is the frequecy rage beyod which the PSD is 10 db below the maximum

15 ore o UWB 57 UWB - Time Hoppig PP 58 Typically trasmit very short pulses of differet shapes Pulse width may be as small as a teth of a aosecod Badwidth associated with such pulses is huge (GHz) Pulses are trasmitted with a low duty cycle PSD Spectrum Idea Use a referece pulse to idicate start of a period A pulse trasmitted earlier tha the period represets a 0 A pulse trasmitted later tha the period represets a 1 Differet Tx-Rx pairs use differet times to trasmit pulses The PSD is very low Looks like oise to most other sigals Pulse Shapes 59 Where ca we use UWB? Next Week 60 FCC regulatios limit the PSD to a specific spectral mask Suitable for short rage applicatios Very high data rates for a few meters Stadards activities Wireless Persoal Area Networks usig UWB a bps We start with db ad ateas Itroductio to Radio Propagatio