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Mobile Phone NetworksENEE 426 | Communication Networks | Spring 2008 Lecture 10Basic Organizations• Infrastructure networks– Downlink: tower to phones (forward)– Uplink: phones to tower (reverse)• Arranged into “cells”– Hence the terminology “cell phones”ENEE 426 | Communication Networks | Spring 2008 Lecture 10Cell Towers• Cell towers typically have 3 sectors• Each operates at a different frequencyENEE 426 | Communication Networks | Spring 2008 Lecture 10Cell Towers• Occasionally local zoning laws prevent towers from being put up, so they have to be camouflagedENEE 426 | Communication Networks | Spring 2008 Lecture 10Cell Towers• Antennas are sectored– Three 120-degree sectors– Each use different frequency, don’t interfereENEE 426 | Communication Networks | Spring 2008 Lecture 10Cell Sites• At the base of the tower there’s the cell site• Contains base station, power, air conditioningENEE 426 | Communication Networks | Spring 2008 Lecture 10Cellular Backhaul• Connection between cell site and Mobile Telephone Switching Office (MTSO)• Can be fiber, copper, or wirelessENEE 426 | Communication Networks | Spring 2008 Lecture 10Cellular History• First-Generation Mobile Phones (1G)• Advanced Mobile Phone System (AMPS)• Analog• Low SNR = static• Unencrypted• FCC required supportuntil Feb 18, 2008ENEE 426 | Communication Networks | Spring 2008 Lecture 10Evolution to Digital• Second generation (2G)• Two standards emerge (circa 1995)– Interim Standard 95 (IS-95), aka cdmaOne• CDMA-base system• Pioneered by Qualcomm who owns CDMA patents– Global System for Mobile communications (GSM)• Originally Groupe Special Mobile, originated in Europe• TDMA system• Other competitors– PCS from Sprint –CDMA at different frequency– iDen from Nextel – GSM with push to talkENEE 426 | Communication Networks | Spring 2008 Lecture 10Voice and Data • 1G and 2G networks only support voice• Low-rate data possible over 2G using modem– Packets -> audio -> digital -> analog RF– 14.4 kbps, VERY inefficient• Need to natively support digital• 2.5G (circa 2000)– GSM Packet Radio Service (GPRS)• Reuse existing GSM time slots to send data• 60 – 80 kbps– CDMA2000 1xRTT (RTT=Radio Transmission Technology)• Doubled coding space for CDMA• 144 kbpsENEE 426 | Communication Networks | Spring 2008 Lecture 10GSM InfrastructureBase Station ControllerPacket ControlUnitMobile Switching CenterVisitorLocation RegisterHome Location RegisterPublic Switched Telephone NetworkServing GPRS Support NodeGateway GPRS Support NodeBase Transceiver StationENEE 426 | Communication Networks | Spring 2008 Lecture 10GSM CoverageENEE 426 | Communication Networks | Spring 2008 Lecture 10CDMA CoverageENEE 426 | Communication Networks | Spring 2008 Lecture 10Early Web Access• Phones not designed to display web pages• New protocol developed: Wireless Application Protocol• Minimal web browsers on phones, web pages designed to support constrained browsers• “compressed” version of HTTP, runs over UDPENEE 426 | Communication Networks | Spring 2008 Lecture 10Higher Data Rates• Evolution of 2.5G -> 2.75G (circa 2003)• Enhanced Data rates for GSM Evolution (EDGE)• Incremental change– Required new base stations and handsets– Same network infrastructure– Uses higher-order modulation (3 bits per baud rather than 1 bit per baud)– ~ 60 kbps per time slot (up to 8 slots per user = 480 kbps)• Eventually classified as a 3G technology (supports rates > 144 kbps)ENEE 426 | Communication Networks | Spring 2008 Lecture 10Move toward broadband• Third Generation (3G) standards• Supports >1 Mbps to handsets (official requirement 144 kbps)• Uses different frequencies than 2G• Requires cell companies to build new infrastructure• International Telecommunications Union (ITU) decides what technologies are considered 3G• International Mobile Telecommunications-2000 (IMT-2000) is global standard; major standards:– EDGE (2.75G)– UMTS / W-CDMA– CDMA2000 EV-DO– Mobile WiMAX (IEEE 802.16e)ENEE 426 | Communication Networks | Spring 2008 Lecture 10GSM 3G Standards (3GPP)• Universal Mobile Telecommunications System (UMTS)• Actually based on Wideband CDMA (W-CDMA) communications• Most users get 500 kbps to 1 Mbps• Enhancements:– 3.5G: High-Speed Downlink Packet Access• Total speeds up to 14 Mbps downlink per base station• Future versions up to 42 Mbps– 3.75G: High-Speed Uplink Packet Access• 5.76 Mbps uplink speeds per base station• Future versions up to 11.5 MbpsENEE 426 | Communication Networks | Spring 2008 Lecture 10CDMA 3G Standards (3GPP2)• CDMA2000 Evolution-Data Only (EVDO)• Uses both CDMA and TDMA• Designed for end-to-end IP connectivity• Downlink: 2.4 Mbps (3.1 Mbps future)• Uplink: 153 kbps (1.8 Mbps future)ENEE 426 | Communication Networks | Spring 2008 Lecture 10Toward 4G• 3GPP Standard– Long Term Evolution (LTE)– Based on OFDMA– Rates over 320 Mbps with MIMO• 3GPP2 Standard– Ultra Mobile Broadband (UMB)– Based on OFDMA– Rates over 280 Mbps with MIMOENEE 426 | Communication Networks | Spring 2008 Lecture 10Enabling Technology: MIMO• MIMO: Multiple Input, Multiple Output• Used in 802.11n, 802.16e, LTE, UMBENEE 426 | Communication Networks | Spring 2008 Lecture 10Technology TableGeneration3GPP3GPP22GGSMIS-95 / cdmaOne2.5GGPRS / EDGEIS-2000 / cdma2000 1xRTT3GUMTScdma2000 EV-DO3.5GHSPA4GIMTIMTENEE 426 | Communication Networks | Spring 2008 Lecture 10Current Events• AT&T: 3GPP network (GSM, EDGE)• Verizon: 3GPP2 network (IS-95, cdma2000)• Verizon– Decided to switch to LTE rather than UMB– UMB has lost traction, 3GPP2 in trouble– Qualcomm, major 3GPP2 vendor, embraces LTE• Sprint / Nextel– Merged in 2005– iDen and PCS networks incompatible– Deploying WiMAX for 4GENEE 426 | Communication Networks | Spring 2008 Lecture 10Converged Backend• IP Multimedia Subsystem (IMS): backend convergence of voice and


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UMD ENEE 426 - Mobile Phone Networks

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