Overview of wireless networks
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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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Overview of wireless networks

Overview of Wireless Networks

Anuj Puri


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)


Overview of wireless networks

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


Overview of wireless networks

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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