1. Access Network Technologies IS250 Spring 2010 chuang@ischool.berkeley.edu

2. 2 Access Network Options  Copper: DSL, cable, power line (PLC/BPL)  Silicon: FTTH  Copper/Silicon Hybrid: HFC, FTTC  Wireless: WiFi, WiMax, cellular (2G, 3G), satellite

3. 3 Local Loop  The “last mile” or “first mile”: connection between customer premise and central office (CO) of telephone company

4. 4 POTS to PANS  Originally for analog POTS (plain old telephone service)  Also used for digital service -Integrated Services Digital Network (ISDN) -Supports voice and data -Digital Subscriber Line (DSL) -Several variants, e.g., ADSL, VDSL, SDSL, … Location of CO’s in U.S. A Central Office

5. 5 ADSL  Asymmetric Digital Subscriber Line  Modulation technique: -DMT (discrete multi- tone)/OFDM (Orthogonal Frequency Division Multiplexing)  Data rate as a function of distance http://www.maxim-ic.com/images/appnotes/3638/3638Fig02.gif

6. 6 Cable Plant Headend Home Drop Loop Node Feeder (Fiber) Active FROM BROADCAST SOURCES  Cable plant originally designed for one-way delivery of CATV programming; upgraded to support two-way data communication -Groups of subscribers in neighborhood share network  Hybrid Fiber Coax (HFC): -Optical fiber from cable headend to neighborhood concentration points -Coax cable to subscriber premises  Cable modem: uses FDM + TDM

7. 7 FTTx  Fiber-to-the-node (FTTN)  Fiber-to-the-curb (FTTC)  Fiber-to-the-building (FTTB)  Fiber-to-the-home (FTTH)

8. 8 WiFi Access Networks  Different scales, different economic models -Wireless ISPs (e.g., Boingo) -Municipal WiFi networks (e.g., Philadelphia, Taipei, Mountain View) -Community mesh networks -Private Access Points  Interference between provider, public and private APs an unresolved issue -WiFi operates in unlicensed spectrum Source: http://www.wigle.net/

9. 9 Wi-Max (802.16)  WMAN standard supporting point-to-multipoint wireless broadband access (WBA) -Up to 30 miles range -Up to 70 Mbps data rate -802.16e provides mobility support  Complements 802.11  Competes against 3G/4G (cellular-based) http://en.wikipedia.org/wiki/Image:30WiMAX.gif

10. 10 Cellular Communications Source: Rappaport, Wireless Communications, Prentice Hall  1 st generation (1G): analog, circuit switched, voice  2 nd generation (2G): digital, circuit switched, voice  2½ generation (2.5G): digital, packet switched, voice and narrowband data  3 rd generation (3G): digital, packet switched, voice and broadband data  4 th generation (4G): “beyond 3G”

11. 11 Cellular Communications Source: Rappaport, Wireless Communications, Prentice Hall Mobile switching center Public switched telephone network

12. 12 Frequency Reuse  Cells with same letter use the same set of frequencies  Cell cluster (outlined in bold) replicated over coverage area  Example: cell cluster size, N = 7  Frequency reuse factor = 1/N Source: Rappaport, Wireless Communications, Prentice Hall

13. 13 Cell Splitting  Cell splitting allows channels to be added with no new spectrum usage  Note: vertices are locations of cell towers Source: Rappaport, Wireless Communications, Prentice Hall

14. 14 Call Handoff  Calls need to be seamlessly handed off from one base station to another to support mobility

15. 15 Umbrella Cells  Supporting users with different mobility rates Source: Rappaport, Wireless Communications, Prentice Hall

16. 16 Local Loop Economics  Cost to deploy new wire: ~$1000 per home -Depends on population density (higher in rural areas) -Example: Verizon FiOS $23B for 18 mil homes -Cost per subscriber is higher  Number of households in U.S.: 100 million  Total cost: at least $100 Billion  Wireless: -AT&T wireless capital investment $20B in 2010 -Number of wireless subscribers 85Mil -Wireless revenue $50B