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

 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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 The “last mile” or “first mile”: connection between customer premise and central office (CO) of telephone company
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 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.
A Central Office
Location of CO’s in U.S.
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 Asymmetric Digital
Subscriber Line
 Modulation technique:
DMT (discrete multitone)/OFDM (Orthogonal
Frequency Division
Multiplexing)
 Data rate as a function of distance
5 http://www.maxim-ic.com/images/appnotes/3638/3638Fig02.gif

 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
Active
Node
Home
FROM
BROADCAST
SOURCES
Headend
Feeder (Fiber)
Drop Loop
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 Fiber-to-the-node (FTTN)
 Fiber-to-the-curb (FTTC)
 Fiber-to-the-building (FTTB)
 Fiber-to-the-home (FTTH)
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 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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 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 http://en.wikipedia.org/wiki/Image:30WiMAX.gif
 Complements 802.11
 Competes against 3G/4G (cellular-based)
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 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”
Source: Rappaport, Wireless Communications, Prentice Hall
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Mobile switching center Public switched telephone network
Source: Rappaport, Wireless Communications, Prentice Hall
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 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 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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 Calls need to be seamlessly handed off from one base station to another to support mobility
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 Supporting users with different mobility rates
Source: Rappaport, Wireless Communications, Prentice Hall
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 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
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