Date post: | 25-Dec-2015 |
Category: |
Documents |
Upload: | poppy-richard |
View: | 214 times |
Download: | 0 times |
Ch0:1Tseng:WirelessNet
Chapter 0:Chances of Wireless Communications
Yu-Chee Tseng
Dept of Computer Science and Information Engr.
National Chiao-Tung University
Ch0:2Tseng:WirelessNet
Wireless Network Architectures
Ch0:3Tseng:WirelessNet
Ch0:4Tseng:WirelessNet
Wireless Network Models
With Infrastructure: Without Infrastructure (ad hoc networks):
Ch0:5Tseng:WirelessNet
Cellular: Infrared:
Ch0:6Tseng:WirelessNet
無線隨意網路( Multi-hop Ad Hoc Network )
Laptop
PDA
LaptopLaptop
Laptop
A
B
C
D
E
PDA
Laptop
Laptop
Laptop
PDA
PDA
C'
Ch0:7Tseng:WirelessNet
感測網路( Sensor Network )
Ch0:8Tseng:WirelessNet
Bluetooth Technology
Ch0:9Tseng:WirelessNet
Applications of Wireless Communications
Ch0:10Tseng:WirelessNet
Mobile Computing
Wireless Communication Technology
Portable Computer Technology appearance of light-weight computing devices
Vision: Ubiquitous Computing / Nomadic Computingcomputers everywhere; information anywhere anytime
Ch0:11Tseng:WirelessNet
Features of Wireless Communication
one global bandwidth shared by all users fortunately channels, such as (frequency, time-slot) pairs, can be reuse
d Radio-based
low bandwidthhigh latency radio communication linkshigher bit error rate (BER)
fading short-term multipath fading (Rayleigh effect)
due to same signal taking different paths and arriving at the receiver shifted in phase
long-term fading (radio shadow) topology of the terrain (like mountains) can cause signal dropouts solution: deploying multiple antenna sites
Ch0:12Tseng:WirelessNet
Features of Portable Computers
Limited resources: limited energy (battery life) limited CPU speed limited memory
Less reliable, less secure
Ch0:13Tseng:WirelessNet
Mobile System Architecture
Cellular-based Ad hoc Relaying link Wireless ATM Packet Radio Network Sensor Networks
Ch0:14Tseng:WirelessNet
Mobile Computing Applications/Services
Wireless information services: Pico-service: local parking lot availability, layout of a buildi
ng Micro-service: train and bus station information, local traffic
information Macro-service: weather information, local news service Wide Area Service: stock market information
Real-time multimedia applications tele-medicine tele-computing collaborative environments
Ch0:15Tseng:WirelessNet
Research: Hardware Aspects
power saving display, LCDlow-voltage CPUs
AT&T's Hobbit chip: 5,000 times less power consumption in doze mode than active mode
radio: IEEE 802.11 power consumption example:
transmit: 1400 mW receive: 1000 mW idle: 830 mW sleep: 130 mW
size, user interface (wearable computers)
Ch0:16Tseng:WirelessNet
Research: Software Aspects
mobile communication protocolsWAPwireless TCPMobile IPMAC protocols
Energy-efficient protocolrelated to the above send/receive/idle/sleep model
... and many others
Ch0:17Tseng:WirelessNet
Research: Algorithmic Aspects
Bandwidth saving Data caching for broadcast channel allocation communication scheduling math. analysis