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Overview of Wireless Networks. Anuj Puri. Outline. Projections of wireless growth Cellular Networks Wireless LANs and Bluetooth WAP Ad Hoc wireless networks. HUGE EXPECTATIONS AND INVESTMENT IN M-DATA. European UMTS spectrum auctions $ Billions. Millions of subscribers worldwide.

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outline
Outline
  • Projections of wireless growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
huge expectations and investment in m data
HUGE EXPECTATIONS AND INVESTMENT IN M-DATA
  • European UMTS spectrum auctions
  • $ Billions
  • Millions of subscribers worldwide
  • Mobile phone subscribers
  • TV households
  • PCs
  • U.K. licenses
  • German licenses
  • French licenses
  • UMTS license fee to date (not ex-haustive)
success of i mode in japan
SUCCESS OF I-MODE IN JAPAN
  • Number of i-mode subscribers
  • Thousands
  • i-Mode has already exceeded 12 million subs
  • Feb 22,1999 start
  • Aug 8
  • Nov 18
  • Dec 23
  • May 31,
  • 2000
outline1
Outline
  • Projections of wireless growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
cellular networks
Cellular Networks
  • Mobile phones (internet access)
  • Cellular concept
    • Frequency reuse
    • Handoffs
organization of cellular networks
HLR (home location

register)

MSC (mobile

switching center)

VLR (visitor

location register)

BS

(base station)

Organization of Cellular Networks

BS – modulation, antenna

MSC – switching

HLR – information (location)

about “home” users

VLR – information about

visiting users

how does a call get to the mobile
How does a call get to the mobile ?
  • Suppose (510) 643 - 1111 is roaming in the (703) area code
  • Cell phone registers with the (703) MSC, which adds it to (703) VLR and informs the (510) HLR of the location of the cell phone
  • A call comes in for (510) 643 – 1111. Then (510) MSC queries its HLR, and directs the call to the (703) MSC
  • The (703) MSC forwards the call to the mobile
handoff
BS A

BS B

Handoff

HLR

MSC

VLR

  • Mobile is associated with BS A
  • It continuously monitors the signal strength from BS A,
  • and BS B
  • When the signal strength from BS B becomes stronger,
  • it associates with BS B
evolution of cellular industry
Evolution of cellular industry

First Generation

Analog Voice

AMPS

Second Generation

Digital Voice

GSM, IS-95,

IS-136, PDC

Third Generation

Packet data

W-CDMA, EDGE,

CDMA2000

multiple migration paths are available
MULTIPLE MIGRATION PATHS ARE AVAILABLE
  • 2.5G
  • 3G
  • 3+G
  • 4G
  • 2G
  • PDC

WCDMA

  • HSPDA
  • GSM
  • GPRS
  • OFDM
  • EDGE
  • Software radio
  • TDMA
  • (IS-136)
  • Array antennas
  • cdma2000
  • MC-3X
  • CDMA (IS-95A/B)
  • CdmaOne
  • 1XRTT
  • 1XEVDO/HDR
  • 1 xtreme

* Footnote

Source: Sources

3g networks
3G Networks

GGSN

SGSN

BS A

BS B

SGSN

Access Network

Physical layer/ MAC

IP based Core Network

Routing/network handoff

mobile ip
Mobile IP
  • Home Agent (HA) – keeps track of where the mobile is (similar to GGSN)
  • Foreign Agent (FA) – delivers packets to the mobile in the foreign network (similar to SGSN)
  • All packets for mobile arrive at HA which “tunnels” them to mobile’s FA
  • When mobile moves to a new location, it informs its HA of the new FA
outline2
Outline
  • Projections of cellular growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
wireless lans and bluetooth
Wireless LANs and Bluetooth
  • For indoor use or operation over small areas
  • Operates in ISM (Industrial Scientific and Medical) Band
  • Spread Spectrum techniques
main components of 802 11
Main Components of 802.11

Roaming

Medium Access

Control

Physical Layer

physical layer
Physical Layer
  • Operate in unlicensed bands
    • In U.S., 900 MHz, 2.4 GHz, 5.7GHz
    • Various restrictions on use
  • Spread Spectrum techniques
    • Direct Sequence Spread Spectrum
    • Frequency Hopping Spread Spectrum
medium access layer
Medium Access Layer
  • Why not use Ethernet protocol ?
    • Sender cannot detect collision
      • senders power overwhelms other transmitters
      • carrier sense does not necessarily mean collision
    • Receiver has a better idea of whether a collision is happening
    • Hidden Terminal / Exposed Terminal Problem
hidden and exposed terminals
Hidden and Exposed Terminals

A

B

C

A and B can hear each other

B and C can hear each other

A and C can not hear each other

Both A and C want to transmit to B (Hidden Terminal)

B wants to transmit to A when C is transmitting to someone

else (Exposed Terminal)

slide20
MACA

A wants to transmit to B

- A sends a RTS to B

- B replies with a CTS

- A sends data to B

RTS: contains the length of data

CTS: also contains the length of data

Everyone hearing RTS stays quiet for CTS

Everyone hearing CTS remains quiet for RTS

802 11 mac
802.11 MAC
  • CSMA/CA (Carrier Sense / Collision Avoidance)
    • Carrier Sense (check to see if someone is transmitting)
    • Collision Avoidance (RTS-CTS-Ack)
  • Acknowledgments at link level
  • Fragmentation and Reassembly
basic scheme
Basic Scheme

RTS

Data

CTS

ACK

Defer Access

NAV (RTS)

Back-off Window

NAV (CTS)

some terminology
Some Terminology

Distribution

System

Access

Point

Access

Point

Basic Service Set (BSS)

Extended Service Set (ESS)

bluetooth
Bluetooth
  • Master-slave architecture
  • Frequency hopping system
  • System design for cheap production
outline3
Outline
  • Projections of cellular growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
wap or the web for small wireless devices
WAP (or the web for small wireless devices)
  • Why not use wired web infrastructure (html, http, tcp) ?
    • HTML too feature rich for small devices
    • TCP may have too much overhead for low bandwidth wireless links
  • WAP (Wireless Application Protocol)
    • An optimized stack for wireless applications
    • Mobile talks with the WAP gateway
    • WAP gateway talks with the web server on the internet
wap architecture
WAP Architecture

WAP

HTTP/TCP

WAP

Gateway

Internet

Web Server

wap stack
WAP Stack

WML, etc

HTML

WSP (Session

Protocol)

HTTP

WTP (Transaction

Protocol)

TCP/UDP

WDP (Datagram

Protocol)

Bearer Services

SMS, CSD

IP

gateways proxies for wireless devices
Gateway

Internet

Web Server

Gateways/Proxies for Wireless Devices ?

2nd Generation: Low speed data, small displays  WAP

3rd Generation: Higher speed, IP address for each station

 Proxy/ Gateway ?

outline4
Outline
  • Projections of wireless growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
ad hoc wireless networks
Ad Hoc Wireless Networks
  • No base stations or infrastructure required
  • Multi-hop wireless networks
    • Each node can talk with a neighbor
  • Applications
    • Sensor networks
    • Intelligent control applications (i.e, IVHS)
ad hoc wireless networks1
Ad Hoc Wireless Networks
  • MAC schemes
  • Addressing
  • Routing
geographical routing algorithm
Geographical Routing Algorithm

Geographical

network

  • Assumptions:
  • Each node knows its own position and its neighbors’ position
  • Nodes don’t know the global topology
  • Destination address is a geographical position to which the packet is to be delivered
a simple routing algorithm
A Simple Routing Algorithm

Routing Decision: Route to the neighbor which is nearest

to the packet destination

Destination

Source

problem with simple routing
Problem with Simple Routing

Wall

Destination

Source

  • Simple routing doesn’t always work
  • The Geographical routing algorithm is an extension of the
  • simple routing algorithm.
routing tables
Routing Tables

Routing Table for Station n:

  • Routing Tables:
  • Routing tables contain some
  • additional entries beside neighbors

(x,y) position

Neighbor

Position of n

-

Position of

neighbor a

a

  • Routing Algorithm:
  • Packet arrives for position p
  • at node n
  • Node n finds the position to
  • which p is closest and forwards
  • to the corresponding neighbor

Position of

neighbor b

b

a

(12,4)

route discovery
Route Discovery
  • Packet gets “stuck” when a node does not have a neighbor to which it can forward the packet
  • When a packet is stuck, a Route Discovery is started to destination D
  • A path p = s(0) s(1)...s(k)is found to D
  • Entry [ position(D), s(i+1) ] is added to the routing table of s(i)
example
Example

Pos(A) = (1,1)

Pos(B) = (2,2)

Pos(C) = (3,1)

Links:

A ---- B

B ---- C

B

Pos(C)

Pos(B)

---

Pos(C)

Pos(A)

A

C

A

Pos(C)

Pos(C)

C

Pos(C)

---

Pos(A)

---

Pos(B)

B

Pos(B)

B

  • A gets a packet for Pos(C)
  • A forwards it to B because pos(B) is closer to pos(C)
  • B forwards it to C because pos(C) is closer to pos(C)
route discovery1
Pos(D)

C

B

Pos(D)

Route Discovery

Pos(D)

Pos(C)

---

Pos(A) = (1,1)

Pos(B) = (2,2)

Pos(C) = (3,1)

Pos(D) = (2.5,0)

Links:

A ---- B

B ---- C

C ---- D

B

B

Pos(B)

---

Pos(D)

Pos(B)

Pos(D)

Pos(D)

D

Pos(D)

A

Pos(A)

C

A

C

Pos(C)

---

Pos(A)

Pos(D)

---

B

Pos(B)

D

Pos(C)

C

Pos(D)

  • A gets a packet for Pos(D)
  • Packet gets stuck at A because Pos(A) is closest to Pos(D)
  • Initiate route discovery for D from A
  • Update the routing tables and forward the packet
slide40
Theorem:There are no cycles in the routing tables.

--- Think of the routing entry [ position(D), a] as a path with

end point D. Then we are always following a path whose end

point is closer to the destination then the end point of the

previous path.

a geometrical view
A Geometrical View

Routing Table for Station n:

Vornoi View:

(x,y) position

Neighbor

a

Position of n

-

Position of

neighbor a

n

b

a

Position of

neighbor b

b

(12,4)

a

(12,4)

  • Route discovery is initiated if packet destination falls within
  • the cell containing station n
  • Each route discovery causes the cell with station n to get split
routing table size
Routing Table Size
  • How many “splits” before station n is alone in its cell ?
    • Each split reduces the cells area ~ 1/2
    • The cell’s area when station n is alone in the cell ~ 1/N
    • where N is the number of stations in a unit area
    • => log(N) splits before station n is alone in its cell
  • Each split causes a route discovery
  • Each route discovery causes L entries to be added to the routing
  • tables where L is the average route discovery path length
  • => O( L log(N) ) entries in routing table of each station
outline5
Outline
  • Projections of wireless growth
  • Cellular Networks
  • Wireless LANs and Bluetooth
  • WAP
  • Ad Hoc wireless networks
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