Transcript Wireless Network Architectures

Chapter 0:
Chances of Wireless Communications
Yu-Chee Tseng
Dept of Computer Science and Information Engr.
National Chiao-Tung University
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Wireless Network Architectures
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Wireless Network Models
 With Infrastructure:
 Without Infrastructure (ad hoc
networks):
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 Cellular:
 Infrared:
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無線隨意網路
（Multi-hop Ad Hoc Network）
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感測網路（Sensor Network）
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Bluetooth Technology
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Applications of Wireless Communications
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Mobile Computing
 Wireless Communication Technology
 Portable Computer Technology
 appearance of light-weight computing devices
 Vision: Ubiquitous Computing / Nomadic Computing
 computers everywhere;
 information anywhere anytime
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Features of Wireless Communication
 one global bandwidth shared by all users
 fortunately channels, such as (frequency, time-slot) pairs,
can be reused
 Radio-based
 low bandwidth
 high latency radio communication links
 higher 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
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 solution: deploying multiple antenna sites
Features of Portable Computers
 Limited resources:
 limited energy (battery life)
 limited CPU speed
 limited memory
 Less reliable, less secure
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Mobile System Architecture
 Cellular-based
 Ad hoc
 Relaying link
 Wireless ATM
 Packet Radio Network
 Sensor Networks
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Mobile Computing Applications/Services
 Wireless information services:
 Pico-service: local parking lot availability, layout of a
building
 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
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Research: Hardware Aspects
 power saving
 display, LCD
 low-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)
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Research: Software Aspects
 mobile communication protocols
 WAP
 wireless TCP
 Mobile IP
 MAC protocols
 Energy-efficient protocol
 related to the above send/receive/idle/sleep model
 ... and many others
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Research: Algorithmic Aspects
 Bandwidth saving
 Data caching for broadcast
 channel allocation
 communication scheduling
 math. analysis
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