EE392I-3

Introduction to Cellular Networking and Rethinking Mobile ArchitecturesJatinder Pal Singh EE 392I, Lecture-3April 13th, 2010

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goals Emerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

Basics: Structure Cells Different Frequencies or CodesBase Station Fixed transceiverMobile Station Distributed transceiversDownlinkUplinkHandoffMultiple Access

Basics: Multiple Access MethodsTimeFrequencyCodesTDMA: Time Division Multiple Access FDMA: Frequency Division Multiple Access CMDA: Code Division Multiple Access

Some More BasicsUplink & Downlink separated inTime: Time Division Duplex (TDD), orFrequency: Frequency Division Duplex (FDD)Information (voice, data) is digitized and bit streams modulated onto carrier Modulation, data redundancy (coding), transmission power, data retransmissions (ARQ) adapted to varying wireless channel qualitySpatial attenuation of signalFrequency or codes can be reused (frequency reuse)

Cellular Technology Evolution0G: Mobile radio telephones (e.g. MTS) 1G: Analog 2G/3G/4G .. - digital:GSM/3GPP FamilycdmaOne/CDMA2000 FamilyGSMGPRSEDGEUMTS, WCDMAHSPAcdmaOne/IS-95CDMA2000 EV-DO2G3G4GLTE

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goalsEmerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

Global System for Mobile communications (GSM)900/1800 MHz band (US: 850/1900 MHz)For 900 MHz bandUplink: 890-915Downlink: 935-96025 MHz bandwidth - 124 carrier frequency channels, spaced 200KHz apartTime Division Multiplexing for 8 full rate speech channels per frequency channel.Handset transmission power limited to 2 W in GSM850/900 and 1 W in GSM1800/1900.

Architecture

The Base Station Subsystem (BSS)Base Transceiver Station BTS - transceivers serve different frequencies. Frequency hopping by handsets and transceiversSectorization using directional antennas Base Station Controller (BSC) controls several (tens to hundreds) of BTSs allocation of radio channelshandovers between BTSs concentrator of traffic databases with information such as carrier frequencies, frequency hopping lists, power reduction levels, etc. for each cell site

Network Switching Subsystem (NSS)This GSM core network manages communication amongst mobile devices & with PSTNMobile Switching Center (MSC) : routing of calls and GSM services for users, mobility management, handovers, Gateway MSC interfaces with PSTN, determines the visited MSC at which the subscriber being called is currently located Visited MSC - MSC where a customer is currently located. The Visitor Location Register (VLR) associated with this MSC has subscriber's data. Anchor MSC - MSC from which handover initiated. Target MSC - MSC toward which a handover should take place. Home Location Register (HLR): database with all mobile phone subscriber details

GPRS core networkMobility management, session management, and transport for IP servicesGPRS Tunneling Protocol, GTP allows end users mobility with continued Internet connectivity by transporting users data between users current SGSN and GGSNGPRS support nodes (GSN) GGSN - Gateway GPRS Support Node SGSN - Serving GPRS Support Node

GSM Support for Data Services: GPRSUser gets pair of uplink and downlink frequencies. Multiple users share the same frequency channel with time domain multiplexing. Packets have constant length corresponding to a GSM time slot. Downlink uses FCFS packet scheduling Uplink Slotted ALOHA for reservation inquiries during contention phasedata transferred using dynamic TDMA with FCFS scheduling. Upto 64 kbps (more for EDGE) downlink per user.

UMTS and 3G technologies (WCDMA & HSPA)Universal Mobile Telecommunications System (UMTS) commonly uses WCDMA as the underlying interfaceTheoretically supports up to 14 Mbps rates with HSDPA WCDMA Frequency bands 1885-2025 Mhz (uplink), 2110-2200 Mhz (downlink)US: 1710-1755 MHz and 2110-2155 MHz W-CDMA has 5 Mhz wide radio channels (CDMA2000 transmits on one or several pairs of 1.25 Mhz radio channels).HSDPA allows networks based on UMTS to have higher data rates on downlink(1.8. 3.6, 7.2, 14.0 Mbps via AMC, and HARQ, fast packet scheduling.

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goalsEmerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

Next Generation Mobile NetworksNext Generation Mobile Networks (NGMN) Ltd. - Consortium with partnership of major mobile operatorsRecommendations without specific technology prescriptionsTarget to establish performance targets, recommendations and deployment scenarios for future wide-area mobile broadband network packet switched coreThe architecture intended to provide a smooth migration of existing 2G/3G networks towards an IP network that is cost competitive and has broadband performance.

NGMN Envisioned System Architecture

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goals Emerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

Alternative fixed wireless and MAN standardsWiMAX, the Worldwide Interoperability for Microwave Access based on IEEE 802.16 standard Last-mile broadband access, backhaul for cellular networks, Internet Services802.16d Fixed WiMAX, 802.16e - Mobile WiMAX. Licensed spectrum profiles: 2.3GHz, 2.5GHz and 3.5GHz. US mostly around 2.5 GHz, assigned primarily to Sprint Nextel, Clearwire.

ConvergenceHeterogeneous access technologiesMulti-mode access devices Dual mode phones (WiFi, 2.5/3G), UMAHeterogeneous ServicesCellular Internet access and Internet based voice/video accessChallengesTime variant heterogeneous network characteristicsHeterogeneous applications with different utilitiesSystem design and networking challenges

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goals Emerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

Cellular Networks and InternetCellular NetworksInternetVoiceDataPacket SwitchedControlledSemi-OrganicGoodPoorIncipient ServiceTechnologyEvolutionMobility SupportNew ServicesOperator initiated or partneredThird party/ independent (largely)

Cellular Networks and InternetCellular NetworksInternetData rates for supporting broadband servicesInsufficient as of presentRelatively highCost per MB of dataHigherLowerQoS at edgesGood Support (voice vs. data)Mostly absent

Internet : Sample scenario Residential Broadband accessInternetBRASDSLAMHome WiFi RouterQoS: Wireless hop (802.11e?), PPPoE, IP QoS (Diffserv) and translation mechanismsMobility Options: MIP - high-barrier, delay performance, incremental patch rather than clean solution?

Cellular ScenarioBetter QoS, scheduling Better Mobility within the cellular network Integrated voice/data AuthenticationDownside is excessive edge network delays, costs of network deployment.

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goalsEmerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

The Economics3G spectrum licensing and migration costTelecom equipment vendors economics of operation, meeting bids vs. system upgrades for technical innovationStiff competition for fixed and mobile segments of operators, drive towards services.Interesting and sometimes conflicting dynamics for both fixed and mobile operators.

AgendaBasics & Technology EvolutionArchitecture and Functionality (GSM, 3G and beyond)Cellular future goalsEmerging trendsAlternative wireless access technologiesConvergenceComparison with Internet and sample scenario studies Economics of operationFrom a clean slate

From a Clean SlateGreater intelligence at edges of networks, eventually leading to just network elements of different sizes and capabilitiesFunctional homogeneity in network elements in terms of storage/caching, processing, networking capability. Such network element should likely be multi-homed connected with heterogeneous technologies (including p2p, delay tolerant), have intelligence for resource allocation, QoS have interaction capability with other network elements (including user devices), support mobility, handoffs have ability to recognize needs of existing and new applications (HDTV, phone, streaming video)be plug and play Interfacing of applications/services (QoS specs) with underlying serving networks for fast and easy deployment.Heterogeneity in access technologies amongst user carried devices honored and accepted by the network elements.

Options for operatorsSharing the spectrum/infrastructure costs?New service models to forestall cost of upgradesGood opportunity for fixed and mobile carriers to take initiative.