Cellular Networks: Architectural and Functional Overview, Evolving Trends, and Clean Slate Design Paradigms

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

Cells Different Frequencies or Codes Basics: Structure Multiple Access Downlink Handoff Uplink Mobile Station Distributed transceivers Base Station Fixed transceiver Cells Different Frequencies or Codes

Basics: Multiple Access Methods Frequency TDMA: Time Division Multiple Access CMDA: Code Division Multiple Access FDMA: Frequency Division Multiple Access Codes Time

Some More Basics Uplink & Downlink separated in Time: Time Division Duplex (TDD), or Frequency: 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 quality Spatial attenuation of signal Frequency or codes can be reused (frequency reuse)

Cellular Technology Evolution 0G: Mobile radio telephones (PTT, MTS) 1G: Analog 2G/3G and beyond - digital: GSM Family cdmaOne/CDMA2000 Family GSM cdmaOne/IS-95 GPRS 2G EDGE HSCSD WCDMA (UMTS) 3G CDMA2000 EV-DO HSPA

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

Global System for Mobile communications (GSM) 900/1800 MHz band (US: 850/1900 MHz) For 900 MHz band Uplink: 890-915 Downlink: 935-960 25 MHz bandwidth - 124 carrier frequency channels, spaced 200KHz apart Time Division Multiplexing for 8 full rate speech channels per frequency channel. Circuit Switched Data with data rate of 9.6 kbps 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 transceivers Sectorization using directional antennas Base Station Controller (BSC) controls several (tens to hundreds) of BTSs allocation of radio channels handovers 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) GSM circuit-switched core network manages communication between mobile phones & PSTN Mobile Switching Center (MSC) : provides circuit switched calling, mobility management, GSM services for users Gateway MSC – interfaces with PSTN, determines which visited MSC the subscriber being called is currently located at 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.

GPRS core network Mobility management, session management, and transport for IP services GPRS Tunneling Protocol, GTP (over UDP) allows end users mobility with continued Internet connectivity GPRS support nodes (GSN) GGSN - Gateway GPRS Support Node SGSN - Serving GPRS Support Node

GSM Support for Data Services: GPRS User 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 phase data 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) - WCDMA as the underlying interface Supports up to 14 Mbps rates with HSDPA (typical present deployed rates per user 384kbps) 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 (1.8. 3.6, 7.2, 14.4 Mbps via AMC, and HARQ, fast packet scheduling. UMTS air interface forms Generic Radio Access Network (GeRAN) which can be connected to various backbone networks like the Internet, ISDN, GSM or UMTS. Using PCMCIA or USB card, or cellular router customers are able to access 3G broadband services

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

In the decade beyond 2010 Next Generation Mobile Networks (NGMN) Ltd. - Consortium with partnership of major mobile operators Recommendations without specific technology prescriptions Target to establish performance targets, recommendations and deployment scenarios for future wide-area mobile broadband network packet switched core The 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: Beyond 3G Video telephony and multimedia conferencing, IM, video streaming – among high drivers for NGMN Essential System recommendations Seamless mobility across all bearers with service continuity through a min of 120 km/h Peak uplink data rates 30-50 Mbps Peak > 100Mbps downlink Latency core < 10ms, RAN <10ms, <30ms e2e QoS based global roaming Broadcast, multicast, and unicast services to subscribers of all environments Real time, conversational and streaming in PS across all required bearers Cost per MB : as close to DSL as possible

NGMN Envisioned System Architecture

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

Alternative fixed wireless and MAN standards WiMAX, the Worldwide Interoperability for Microwave Access based on IEEE 802.16 standard Last-mile broadband access, backhaul for cellular networks, interconnectivity for hotspots OFDMA used by 802.16e. MIMO support amongst recent developments Licensed spectrum profiles: 2.3GHz, 2.5GHz and 3.5GHz. US mostly around 2.5 GHz, assigned primarily to Sprint Nextel, Clearwire. Claims for delivery of 70 Mbps, and over 50 kilometers, not simultaneously true.

Convergence Heterogeneous access technologies Multi-mode access devices Dual mode phones (WiFi, 2.5/3G), UMA Heterogeneous Services Cellular Internet access and Internet based voice/video access Challenges Time variant heterogeneous network characteristics Heterogeneous applications with different utilities System design and networking challenges

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

Cellular Networks and Internet Incipient Service Data Voice Circuit Switched Analog Circuit Switched Digital C.S. Voice + P.S. Data Packet Switched Technology Evolution Controlled Semi-Organic Operator initiated or partnered Third party/ independent (largely) New Services Mobility Support Good Poor

Cellular Networks and Internet QoS at edges Good Support (voice vs. data) Mostly absent Data rates for supporting broadband services Insufficient as of present Relatively high Cost per MB of data Lower Higher

Internet : Sample scenario – Residential Broadband access BRAS DSLAM Home WiFi Router QoS: Wireless hop (802.11e?), PPPoE, IP QoS (Diffserv) and translation mechanisms Mobility Options: MIP - high-barrier, delay performance, incremental patch rather than clean solution?

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

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

The Economics 3G spectrum licensing and migration cost Telecom equipment vendors – economics of operation, meeting bids vs. system upgrades for technical innovation Stiff competition for fixed and mobile segments of operators, drive towards services. Interesting and sometimes conflicting dynamics for both fixed and mobile operators.

Agenda Basics & Technology Evolution Architecture and Functionality (GSM, 3G and beyond) Cellular future goals (2010 and beyond) Emerging trends Alternative wireless access technologies Convergence Comparison with Internet and sample scenario studies Economics of operation From a clean slate

From a Clean Slate Greater intelligence at edges of networks, eventually leading to just network elements of different sizes and capabilities Functional 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 operators Sharing the spectrum/infrastructure costs? New service models to forestall cost of upgrades Good opportunity for fixed and mobile carriers to take initiative.

Deutsche Telekom Laboratories: Related Research Efforts Broadband Access Sharing (Extended HotSpots) Commercial grade routers with virtualization, user traceability, limited QoS support. Limited trail in Berlin; Pilot for extensive evaluation launched and technology on company product roadmap for 2008. Distributed Authentication framework for a Global WiFi network (Mobicom’07, extended abstract) Heterogeneous Network access Optimal Control theoretic approach for rate allocation (WiOpt’07) Convex optimization framework for media-aware rate allocation for HD video sequences (ACM Multimedia’07, best student paper award) Markov Decision Process based flow assignment over heterogeneous networks (IEEE WoWMoM’07, top 15 papers) Peer to Peer Media Streaming Large scale dynamics of a commercial P2P streaming session and real-world testing of commercial P2P streaming solutions. Gossip based P2P streaming protocol (Journal on Advances in Multimedia’07)

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