Mobile Phone Networks

Transcription

1 Mobile Phone Networks

2 Basic 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 2009 Slide # 2

3 Cell Towers Cell towers typically have 3 sectors Each operates at a different frequency ENEE 426 Communication Networks Spring 2009 Slide # 3

4 Cell Towers Occasionally local zoning laws prevent towers from being put up, so they have to be camouflaged ENEE 426 Communication Networks Spring 2009 Slide # 4

5 Cell Towers Antennas are sectored Three 120-degree sectors Each use different frequency, don t interfere ENEE 426 Communication Networks Spring 2009 Slide # 5

6 Cell Sites At the base of the tower there s the cell site Contains base station, power, air conditioning ENEE 426 Communication Networks Spring 2009 Slide # 6

7 Cellular Backhaul Connection between cell site and Mobile Telephone Switching Office (MTSO) Can be fiber, copper, or wireless ENEE 426 Communication Networks Spring 2009 Slide # 7

8 Cellular History First-Generation Mobile Phones (1G) Advanced Mobile Phone System (AMPS) Analog Low SNR = static Unencrypted FCC required support until Feb 18, 2008 ENEE 426 Communication Networks Spring 2009 Slide # 8

9 Evolution 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 talk ENEE 426 Communication Networks Spring 2009 Slide # 9

10 Voice 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 kbps CDMA2000 1xRTT (RTT=Radio Transmission Technology) Doubled coding space for CDMA 144 kbps ENEE 426 Communication Networks Spring 2009 Slide # 10

11 GSM Infrastructure Base Station Controller Mobile Switching Center Visitor Location Register Public Switched Telephone Network Home Location Register Packet Control Unit Gateway GPRS Support Node Base Transceiver Station Serving GPRS Support Node ENEE 426 Communication Networks Spring 2009 Slide # 11

12 GSM Coverage ENEE 426 Communication Networks Spring 2009 Slide # 12

13 CDMA Coverage ENEE 426 Communication Networks Spring 2009 Slide # 13

14 Early 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 UDP ENEE 426 Communication Networks Spring 2009 Slide # 14

15 Higher 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 2009 Slide # 15

16 Move 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 e) ENEE 426 Communication Networks Spring 2009 Slide # 16

17 GSM 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 Mbps ENEE 426 Communication Networks Spring 2009 Slide # 17

18 CDMA 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 2009 Slide # 18

19 Toward 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 MIMO ENEE 426 Communication Networks Spring 2009 Slide # 19

20 Enabling Technology: MIMO MIMO: Multiple Input, Multiple Output Used in n, e, LTE, UMB ENEE 426 Communication Networks Spring 2009 Slide # 20

21 Technology Table Generation 3GPP 3GPP2 2G GSM IS-95 / cdmaone 2.5G GPRS / EDGE IS-2000 / cdma2000 1xRTT 3G UMTS cdma2000 EV-DO 3.5G HSPA 4G IMT IMT ENEE 426 Communication Networks Spring 2009 Slide # 21

22 Current 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 4G ENEE 426 Communication Networks Spring 2009 Slide # 22

23 Converged Backend IP Multimedia Subsystem (IMS): backend convergence of voice and data ENEE 426 Communication Networks Spring 2009 Slide # 23