Download - Access Network Technologies
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Access Network Options
Copper: DSL, cable, power line (PLC/BPL)
Silicon: FTTH Copper/Silicon Hybrid: HFC, FTTC
Wireless: WiFi, WiMax, cellular (2G, 3G), satellite
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Local Loop The “last mile” or “first mile”: connection between customer premise and central office (CO) of telephone company
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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, …
QuickTime™ and a decompressor
are needed to see this picture.
Location of CO’s in U.S.
A Central Office
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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
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Cable Plant
Headend
Home
Drop Loop
Node
Feeder (Fiber)
Active
FROMBROADCASTSOURCES
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
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FTTx
Fiber-to-the-node (FTTN) Fiber-to-the-curb (FTTC) Fiber-to-the-building
(FTTB) Fiber-to-the-home (FTTH)
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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/
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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
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Cellular Communications
Source: Rappaport, Wireless Communications, Prentice Hall
1st generation (1G): analog, circuit switched, voice
2nd generation (2G): digital, circuit switched, voice
2½ generation (2.5G): digital, packet switched, voice and narrowband data
3rd generation (3G): digital, packet switched, voice and broadband data
4th generation (4G): “beyond 3G”
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Cellular Communications
Source: Rappaport, Wireless Communications, Prentice Hall
Mobile switching center Public switched telephone network
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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
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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
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Call Handoff
Calls need to be seamlessly handed off from one base station to another to support mobility
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Umbrella Cells
Supporting users with different mobility rates
Source: Rappaport, Wireless Communications, Prentice Hall
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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