1. Ch2:1 WirelessNet Tseng Fundamental of Wireless LAN n Radio Waves n IEEE 802 Families n Appenidx (Infrared and Carrier Currents LANs)

2. Ch2:2 WirelessNet Tseng Wireless LAN Configuration

3. Ch2:3 WirelessNet Tseng Radio-Based Wireless LANs n Most widely used method uAdv: penetrating walls and other obstacles with little attenuation. uDisadv: security, interference, etc. n 2 approaches: uNarrow band uISM band and Spread spectrum

4. Ch2:4 WirelessNet Tseng Narrow Band Modulation n Concentrate all transmission power in a narrow range of frequency. n Efficient use of radio spectrum; save bandwidth. n ex: television, AM, FM n Adv: for long distance transmission (e.g. metropolitan area) n Disadv: noise can easily corrupt the signals n Need to obtain FCC licenses to coordinate the use.

5. Ch2:5 WirelessNet Tseng ISM Bands n In 1985, FCC modified part 15 to stimulate the use of wireless networks. n ISM=Industrial, Scientific, and Medical n Unlicensed, you can freely install and move.

6. Ch2:6 WirelessNet Tseng ISM Spectrum Availability n Only 2.4 GHz is the world-accepted ISM band. n 902 MHz is easier in manufacturing.

7. Ch2:7 WirelessNet Tseng Spread Spectrum Modulation n Definition: “spread” a signal’s power over a wider band of frequency.

8. Ch2:8 WirelessNet Tseng Spread Spectrum n Disadv: This contradicts with the goal of conserving bandwidth. n Adv: less susceptible to electrical noise (especially from narrow band sources) uIn World War II, US Army uses spread spectrum to avoid hostile jamming. (invented by Hedy Lamarr, an actress) n To spread a signal, there are two ways: udirect sequence (DSSS) ufrequency hopping (FHSS)

9. Ch2:9 WirelessNet Tseng Direct Sequence Spread Spectrum (DSSS) n Use bit sequence to represent “zero” and “one” (Fig. 2-5) n Also referred to as “chipping code”. n Longer chipping codes are more resilient to noise. n Minimum length = 10 (by FCC) n IEEE 802.11 uses 11 chips per data bit.

10. Ch2:10 WirelessNet Tseng Frequency Hopping Spread Spectrum (FHSS) n Data is modulated by carrier signals that hop from frequency to frequency as a function of time, over a wide band of frequencies.

11. Ch2:11 WirelessNet Tseng FHSS (cont.) n Hopping Code: to determine the order of hopping frequencies n The receiver must “listen” to incoming signals at the right time at the right frequency. n FCC regulation: at least 75 frequencies, with max. dwell time 400ms. n Adv.: very resilient to noise. n Orthogonal hopping codes: a set of hopping codes that never use the same frequencies at the same time (can be on-line adjusted by software). n Allow multiple wireless LANs to co-exist.

12. Ch2:12 WirelessNet Tseng Forms of Radio-based Wireless LAN uWireless Local Bridge uInfrastructure uAd Hoc

13. Ch2:13 WirelessNet Tseng IEEE 802 Families n IEEE? ua non-profit professional org. founded in 1884; now has 320,000 members in 150 countries; n Most notable standards: uIEEE 802 family (802.2 LLC, 802.3 Ethernet, 802.5 Token Ring, etc.) n IEEE membership info: uOpen to anyone. It’s FREE!! Must pay meeting fees. uMembership Category: voting member, nearly member, aspirant member, sleeping member.

14. Ch2:14 WirelessNet Tseng n 802.11a: Specification enabling up to 54 Mb/s to be achieved in the 5 GHz unlicensed radio band by utilizing OFDM n 802.11b: Specification enabling up to 22 Mb/s to be achieved in the 2.4 GHz unlicensed radio band by utilizing DSSS n 802.11c: Provides required information to ensure proper bridge operations, which is required when developing access points n 802.11d: Covers additional regulatory domains, which is especially important for operation in the 5 GHz bands because the use of these frequencies differ widely from one country to another Task groups of 802.11

15. Ch2:15 WirelessNet Tseng n 802.11e: Covers issues of MAC enhancements for QoS, such as EDCF service differentiation and HCF n 802.11f: Provides interoperability for users roaming from one access point to another of different vendor n 802.11g: Specification enabling up to 54 Mb/s to be achieved in the 2.4 GHz unlicensed radio band n 802.11h: Dynamic channel selection and transmission power control n 802.11i: Specification for WLAN security to replace the weak Wired Equivalent Privacy (WEP) n 802.11k: Radio resource measurement for 802.11 specifications so that a wireless network can be used more efficiently n 802.11p: 又稱 WAVE ； Wireless Access in the Vehicular Environment ）是一個由 IEEE 802.11 標準擴充的通訊協定。這個 通訊協定主要用在車用電子的無線通訊上。它設定上是從 IEEE 802.11 來擴充延伸，來符合智慧型運輸系統（ Intelligent Transportation Systems ， ITS ）的相關應用。 IEEE 802.11 標準通訊協定無線通訊 IEEE 802.11智慧型運輸系統 Intelligent Transportation Systems Task groups of 802.11

16. Ch2:16 WirelessNet Tseng Appendix: (for your reference)

17. Ch2:17 WirelessNet Tseng Infrared Light-based Wireless LAN n Wavelength range: 0.75 ~ 1000 u uultraviolet < visible lights < infrared < radio utypically operating at 0.82u n Adv: uhigher security: does not propagate through opaque objects, keeping signals within rooms and building uno interference from microwave ovens and radio transmitters n Disadv: udirectional, not suitable for mobile applications n Two types of infrared light LANs: uDiffused uPoint-to-point

18. Ch2:18 WirelessNet Tseng Diffused Infrared-based LAN n Example: TV remote controller n Example: three stations using a ceiling uJust like using a flashlight, and talking to people using Morse Code. uA person wants to send must look at the ceiling to make sure that no other people are sending. uThe receiver looks at the packet header to check for incoming packets.

19. Ch2:19 WirelessNet Tseng n “Point-to-Point” Infrared LAN System uEach link has a pair of transducers (uni-directional): å up to 75 ft. uconnect as a token ring (what is token ring??) åEach transducer can talk with a IEEE 802.5 token ring board. udata rate: 4 and 16 Mbps); uGood security: åResilient to electrical noise. uNo mobility, little fault-tolerant capability

20. Ch2:20 WirelessNet Tseng Carrier Current LANs n Use power line as a medium to transmit data. uFig. 2.15 n The electrical power companies provide 110V, 60Hz alternating current; the signal can support 1~2 Mbps data signals. n Adv: adopt already-existing cables n Products are being seen/proposed in the market.

21. Ch2:21 WirelessNet Tseng Power Line Communication n Power line communication or power line carrier (PLC) is a system for carrying data on a conductor also used for electric power transmission uDifferent types of power line communications use different frequency bands, depending on the signal transmission characteristics of the power wiring used

22. n Ultra-High-frequency communication (≥ 100 MHz) n High-frequency communication (≥ 1 MHz) uHome networking (broadband) åUsed to interconnect home computers, peripherals or other networked consumer peripherals uInternet access (broadband over power lines) åThe use of PLC technology to provide broadband Internet access through ordinary power lines Ch2:22 WirelessNet Tseng broadband over power lines(BLP) power line Ethernet

23. Ch2:23 WirelessNet Tseng n Medium frequency (≥ 1 kHz) uHome control (narrowband) åUse the household electrical power wiring as a transmission medium uLow-speed narrow-band communication åControl and telemetry of electrical equipment such as meters, switches, heaters and domestic appliances uTransmitting radio programs n Low frequency (< 1 kHz) uPLC is one of the technologies used in the automatic meter reading industry Remote control of lighting and appliances without installation of additional control wiring Automatic meter reading X10 ZigBee