Wireless LAN 第一組 電機四 林長寬 B9090193 2018/11/24

Outline What is “wireless”? Challenges of wireless networks Introduction to various standards Comparison 2018/11/24

“Wireless” means? 2018/11/24

Popular Dominant Wireless Systems 2018/11/24

Architecture 2018/11/24

Challenges for wireless network (1) Interference from other sources 2018/11/24

Solution Candidates Simple but inefficient when users are idle. The total number of users is limited. 2018/11/24

Random Access Protocol Carrier Sense Multiple Access (CSMA) Every user has the opportunity to access to the media. Listen before you speak! 2018/11/24

Challenges for wireless network (2) When a common media is shared for each host in the same BSS… 2018/11/24

Solutions to Multiple Access CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) 2018/11/24

Other Transmission Techniques Interference & Jamming DSSS (Direct Sequence Spread Spectrum) FHSS (Frequency Hopping Spread Spectrum) Bandwidth Efficiency OFDM (orthogonal frequency division multiplexing) Please refer to the Communication System course. 2018/11/24

Wireless Standards IrDA 802.11a/b/g HomeRF HiperLAN/2 2018/11/24

IrDA Infrared Data Association (IrDA) <Applications> Remote Controller, transmission between consuming electronic gadgets. <Features> Line of sight transmission only Connection between 2 devices only Low security level Low price 2018/11/24

802.11a/b/g (cont’) Standardized by IEEE, also known as Wi-Fi. <Applications> WLAN interface card, AP, etc. <Features> The most popular wireless standards. Use CSMA/CA and identical frame structure. Both infrastructure mode and ad hoc are allowed. 2018/11/24

802.11a/b/g (cont’) 802.11a 802.11b 802.11g Standard Operating Freq. Data Rate Distance Modulation Scheme 802.11a 5.1 ~ 5.8 GHz 54 Mbps 30 m OFDM 802.11b 2.4 ~ 2.485 GHz 11 Mbps 100m (indoor) 400m (outdoor) DSSS with CCK 802.11g 20Mbps↑:OFDM 20Mbps↓:DSSS 2018/11/24

HomeRF Based on Share Wireless Access protocol (SWAP) <Applications> Intended for use in homes, for communication between PCS, or other consumer devices. <Features> Integrate both data and voice signal transmission. Relatively inexpensive to set up and maintain. Responds well to interference because of frequency-hopping modulation. 2018/11/24

HiperLAN/2 Standardized by the European Telecommunication Standardization Institution (ETSI) <Applications> WLAN devices <Features> Only in Europe. Theoretical maximum speed of 54 Mbps. Bandwidth guaranteed. 2018/11/24

Comparison IrDA 802.11b HomeRF HiperLAN/2 Standard Operating Freq. Data Rate Distance Modulation Scheme IrDA Wavelength: 820 nm 4/16 Mbps ~ 5 m 802.11b 2.4 ~ 2.485 GHz 11 Mbps 100m (indoor) 400m (outdoor) DSSS with CCK HomeRF 2.4 GHz 10 Mbps 50 m FHSS HiperLAN/2 5 GHz 54 Mbps 30m (indoor) 150m (outdoor) OFDM 2018/11/24

Reference Computer networking A Top-Down Approach Featuring the Internet 3rd by James F.Kurose & Keith W. Ross http://www.hi-pda.com/drupal/ http://www.ibm.com/tw/ http://www.purplesky.com.tw/2k.htm http://www.dlink.com.tw/home.asp http://cobra.ee.ntu.edu.tw/~oops/HTML6/01_html/Oral_presentation.htm http://www.webopedia.com/quick_ref/WLANStandards.asp 2018/11/24

Thank you for your listening! 2018/11/24