Lecture19 - Tue sday, June3 Quiz #3, Hom work #5 e S s...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Tuesday, June 3 Quiz #3, Homework #5 Scores are posted Lowest quiz is dropped Pick up Quiz #3 Questions? Program #2 is due Thursday, June 5 If you are working with a partner, be sure to check the extra requirements
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Today's Topics Introduction to wireless networking Mobility Instructor Evaluation
Background image of page 2
3 Wireless and Mobile Networks Background: # wireless (mobile) phone subscribers now exceeds # wired phone subscribers computer nets: laptops, palmtops, PDAs, Internet-enabled phone promise anytime-anywhere mobile Internet access two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Elements of a wireless network network infrastructure wireless hosts laptop, PDA, IP phone run applications may be stationary (non-mobile) or mobile wireless does not always mean mobility
Background image of page 4
5 Elements of a wireless network network infrastructure base station typically connected to wired network relay - responsible for sending packets between wired network and wireless host(s) in its “area” e.g., cell towers, 802.11 access points
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Elements of a wireless network network infrastructure wireless link typically used to connect mobile(s) to base station also used as backbone link multiple access protocol coordinates link access various data rates, transmission distance, etc.
Background image of page 6
7 Elements of a wireless network network infrastructure infrastructure mode base station connects mobiles into wired network handoff: mobile changes base station providing connection
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 Elements of a wireless network ad hoc mode no base stations nodes can only transmit to other nodes within link coverage nodes organize themselves into a network: route among themselves
Background image of page 8
9 Wireless Link Characteristics Differences from wired link …. decreased signal strength: radio signal attenuates as it propagates through matter (path loss) interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well multipath propagation: radio signal reflects off objects, arriving at destination at slightly different times …. make communication across wireless link (even a point to point) much more “difficult”
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
10 Wireless traffic control Wireless uses collision avoidance (CA) rather than collision detection (CD) Transmitting computer sends very short "reservation" message to receiver Destination responds with short message reserving slot for sender Response from destination is broadcast so all potential senders are notified of the reservation
Background image of page 10
11 IEEE 802.11: multiple access avoid collisions: 2 + nodes transmitting at same time 802.11: CSMA - sense before transmitting don’t collide with ongoing transmission by other node 802.11: no collision detection!
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/28/2009 for the course CS 372 taught by Professor Leviet during the Fall '07 term at Oregon State.

Page1 / 45

Lecture19 - Tue sday, June3 Quiz #3, Hom work #5 e S s...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online