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Cellular Networks and Mobile Architectures

Cellular Networks and Mobile Architectures. PSTN. Mobile Telecommunications. Public Switched Telephone Network. Mobile Switching Office. Air Interface. Cell Tower. Pre-Cellular Technology. One Transmitter High Power Limited Channels. Source: International Engineering Consortium.

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Cellular Networks and Mobile Architectures

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  1. Cellular Networks and Mobile Architectures

  2. PSTN Mobile Telecommunications Public Switched Telephone Network Mobile Switching Office Air Interface Cell Tower

  3. Pre-Cellular Technology • One Transmitter • High Power • Limited Channels Source: International Engineering Consortium

  4. Cellular Architecture • Many Transmitters • Low Power • Frequency Reuse Source: International Engineering Consortium

  5. Cellular Architecture • Each tower serves one cell • Each cell uses different frequencies • As phone moves from one cell to another, towers “handoff” calls

  6. Seven Way Frequency Re-use Cellular networks are designed so adjacent cells use different frequencies Source: International Engineering Consortium

  7. Cellular vs PCS • All mobile telephony providers use “cellular” architecture • Primarily two different types of FCC licenses are used to provide mobile telephony: Cellular and PCS (Personal Communications System)

  8. Mobile Telephony Generations • First Generation – Analog • AMPS (Advanced Mobile Phone System) • First cellular standard, used by all cellular licensees • Represented pioneer analog cellular systems that permitted two-way voice communications, circuit-switched data transmission

  9. Mobile Telephony Generations • Second Generation - Digital • TDMA (Time Division Multiple Access) - AT&T • CDMA (Code Division Multiple Access) - Sprint, Verizon • GSM (Global System for Mobile Communications) • Voicestream, Most European Operators • iDEN(Integrated Digital Enhanced Network) - Nextel • Uses SMR licenses rather than cellular or PCS • 2G networks are the first digital mobile telephone networks and offer voice services such as voice mail and caller ID as well as Short Messaging Service (SMS) • Data speeds of 9.6 to 19.2 kbps

  10. Mobile Telephony Generations • Third Generation – Digital • WCDMA: Wideband Code Division Multiple Access • CDMA2000 : Code Division Multiple Access • UMTS : Universal Mobile Telecommunications System • EDGE : Enhanced Data for Global Evolution • DECT: Digital Enhanced Cordless Telecommunications • Called UMTS in Europe • Currently in development • 3G technology promises Internet access with speeds up to 2 Mbps • Combines high-speed mobile access with Internet Protocol (IP) based services. • Planned 3G services include video and audio streaming and location-based services • This doesn't just mean fast mobile connection to the World Wide Web - by liberating us from slow connections, cumbersome equipment and immovable access points, 3G will enable new ways to communicate, access information, conduct business and learn.

  11. 1G: First Generation Mobile Telephony • AMPS : Advanced Mobile Phone System • Original Standard for analog mobile telephony systems • Still used in some areas of North America, Latin America, Eastern Europe, Australia, and parts of Russia and Asia. • Competes with GSM and CDMA • To optimize the use of transmission frequencies, AMPS divides geographic areas into cells • Each connection uses its own dedicated frequency - of which there are about 1,000 per cell. • Two cells can use the same frequency for different connections so long as the cells are not adjacent to each other. • The digital IS-136 TDMA standard (often known as D-AMPS) offers the evolutionary path from analog AMPS.

  12. 2G: Second Generation Mobile Telephony • CDMA : Code Division Multiple Access • IS-95 based digital technology for delivering mobile telephone services. • CDMA systems have been in commercial operation since 1995 • These systems now support over 95 million subscribers worldwide. • CDMA networks operate in the 800 and 1900 MHz frequency bands with primary markets in the Americas and Asia. • Provides for voice and data services up to speeds of 64 kbits/sec, as well as integrated voice mail and SMS services. • Marketed using the name cdmaOne. • The next evolutionary step for 3G services is CDMA2000, or IS-2000.

  13. 2G: Second Generation Mobile Telephony • TDMA : Time Division Multiple Access • Also known as D-AMPS • Technology for digital transmission of radio signals between a mobile telephone and a radio base station. • In TDMA, the frequency band is split into a number of channels. • Each channel is split into three time units, so that three calls can share a single frequency channel without interfering with one another. • Based on the IS-136 standard. • It is one of the world's most widely deployed digital wireless systems. PR providers are now switching from CDMA to TDMA • It provides a natural evolutionary path for analog AMPS networks • Offers efficient coverage and is well suited to emerging applications, such as wireless virtual private networks (VPNs) • Ideal platform for PCS (Personal Communication Services).

  14. 2G: Second Generation Mobile Telephony • GSM : Global System for Mobile Communications • First introduced in 1991 • One of the leading digital cellular systems. • Eight simultaneous calls can occupy the same radio frequency. • GSM simplifies data transmission to allow laptop and palmtop computers to be connected to GSM phones. • It provides integrated voice mail, high-speed data, fax, paging and short message services capabilities, as well as secure communications. • It offers the best voice quality of any current digital wireless standard. • Originally a European standard for digital mobile telephony, GSM has become the world's most widely used mobile system in use in over 100 countries. • GSM networks operate on the 900 MHz and 1800 MHz waveband in Europe, Asia and Australia, and on the 1900 MHz waveband in North America and in parts of Latin America and Africa.

  15. 2G: Second Generation Mobile Telephony • GPRS : General Packet Radio Service • Packet-linked technology • Enables high-speed wireless Internet and other data communications. • GPRS provides more than four times greater speed than conventional GSM systems. • Using a packet data service, subscribers are always connected and always on line so services will be easy and quick to access.

  16. 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. • Handset transmission power limited to 2 W in GSM850/900 and 1 W in GSM1800/1900.

  17. Architecture

  18. 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

  19. Network Switching Subsystem (NSS) • This GSM core network manages communication amongst mobile devices & with PSTN • Mobile 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

  20. GPRS core network • Mobility management, session management, and transport for IP services • GPRS Tunneling Protocol, GTP allows end users mobility with continued Internet connectivity by transporting user’s data between users’ current SGSN and GGSN • GPRS support nodes (GSN) • GGSN - Gateway GPRS Support Node • SGSN - Serving GPRS Support Node

  21. 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.

  22. IMT-2000 • International Mobile Telecommunications 2000 • Term used by the International Telecommunication Union (ITU), a United Nations agency, to describe third generation mobile telephony standards that meet a number of requirements in terms of transmission speed and other factors. • Basic standards in IMT-2000 include: \ • IMT-DS (direct spread). WCDMA • IMT-MC (multi-carrier). CDMA2000 • IMT-TC (time-code) UTRA TDD & TD-SCDMA • IMT-FT (frequency-time). DECT • IMT-SC (single carrier). TDMA

  23. IMT-2000 Terrestrial Radio Interfaces

  24. Transition to 3G

  25. 3G: Third Generation Mobile Telephony • WCDMA: Wideband Code Division Multiple Access • Technology for wideband digital radio communications of Internet, multimedia, video and other capacity-demanding applications. • WCDMA is the dominating 3G technology, providing higher capacity for voice and data and higher data rates. • Uses a new spectrum with a 5 MHz carrier, providing 50 times higher data rate than in present GSM networks, and 10 times higher data rate than in GPRS networks • Handles up to 2 Mbps for local area access or 384 Kbps for wide area access. A coming release will include enhancements up to more than 10 Mbps.

  26. 3G: Third Generation Mobile Telephony • WCDMA: Wideband Code Division Multiple Access • WCDMA is also known as UMTS • Has been adopted as a standard by the ITU under the name IMT-2000 direct spread. • The gradual evolution from today's systems is driven by demand for capacity, which is required by new and faster data based mobile services. • WCDMA enables better use of available spectrum and more cost-efficient network solutions. • The operator can gradually evolve from GSM to WCDMA, protecting investments by re-using the GSM core network and 2G/2.5G services.

  27. 3G: Third Generation Mobile Telephony • CDMA 2000: Code Division Multiple Access 2000 • Also known as IS-2000 • 3G technology that can be deployed in several phases. • The first phase, CDMA2000 1X, supports an average of 144 kbps packet data in a mobile environment. • The second release of 1X, called 1xEV-DO can support data rates up to 2 Mbps on a dedicated data carrier • The final phase, 1xEV-DV, supports even higher peak rates, simultaneous voice and high-speed data, as well as improved Quality of Service mechanisms. • A key component of CDMA2000 is its ability to support the full demands of advanced 3G services such as multimedia and other IP-based services.

  28. 3G: Third Generation Mobile Telephony • EDGE : Enhanced Data for Global Evolution • A technology that gives GSM the capacity to handle services for the third generation of mobile telephony. • EDGE provides three times the data capacity of GPRS. • Using EDGE, operators can handle three times more subscribers than GPRS; triple their data rate per subscriber, or add extra capacity to their voice communications. • EDGE uses the same TDMA (Time Division Multiple Access) frame structure, logic channel and 200kHz carrier bandwidth as today's GSM networks, which allows existing cell plans to remain intact.

  29. 3G: Third Generation Mobile Telephony • DECT : Digital Enhanced Cordless Telecommunications • A common standard for cordless personal telephony • Originally established by ETSI, a European standardization body. • DECT is a system for cordless business communications.

  30. 3G: Applications, Services and Market

  31. Difference between regular TDMA and W-CDMA

  32. Difference between regular CDMA and W-CDMA

  33. UMTS and 3G technologies (WCDMA & HSPA) • Universal Mobile Telecommunications System (UMTS) – commonly uses WCDMA as the underlying interface • Theoretically 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.

  34. Next Generation Mobile Networks • 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.

  35. 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

  36. NGMN Envisioned System Architecture

  37. 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, Internet Services • 802.16d 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.

  38. 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

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

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

  41. Internet : Sample scenario – Residential Broadband access Internet 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?

  42. 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.

  43. END.

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