1. CPET 260 – Network I Wireless Networks Bluetooth

2. Wireless Networking: IEEE 802.11 (Wi-Fi) and Home RF Advantages Fast installation Adaptable to changing environment Reduced costs in many situations Applications Hospitals Older buildings Temporary setups Warehouse & Factor Floors

3. Ad-Hoc Networks & Access Points (Aps) Ad-Hoc networks are established ‘on the fly’ A number of computers, each with wireless NIC adapters Communications is established by the computers interchange Peer to Peer network AKA – Basic Service Set (BSS) or Independent Basic Service Set (IBSS)

4. Access Point An AP acts as an intermediary in the network – potentially extending the distance between far points of the net. AP can be added to a wired net to provide extend or provide additional services.

5. Examples D-Link DWL-1000AP 11Mbps, 5.5Mbps, 1Mbps or auto Supports DHCP 100 to 300 meters

6. Examples D-Link DL-713 Wireless Gateway Wireless + 3 switch ports Supports Network Address Translation (NAT) – security IEEE 802.11b & ‘Wi-Fi’ compatible

7. IEEE 802.11 Standards Spread Spectrum radio Frequency Hopping Spread Spectrum (FHSS) Original 802.11 std used FHSS 1Mbps Direct Sequence Spread Spectrum (DSSS) Supported both 1Mbps & 2Mbps IR is included – at 1Mbps & 2Mbps Not implemented to any great amount

8. IEEE 802.11 Standards The MAC layer – Ethernet used CSMA/CD – Carrier Sense Multi-Access/Collision Detect Required that transmission be monitored while sent RF cannot perform monitoring while sending CSMA/CA – Carrier Sense Multi-Access / Collision Avoidance

9. CSMA/CA As with CSMA/CD – the NIC listens for a carrier already in use If detected – backs off & waits If no detection, sends packet Waits for ACK packet – to acknowledge receipt of data packet. If no ACK – the lost packet is retransmitted. Also known as Distributed Coordination Function (DCF)

10. CSMA/CA In a wireless network, since each node needs only to communicate to the AP – not to each other, they may be out of range of one another. Hidden Node problem Solved by sending RTS (request to send) + amt of time needed to the AP AP responds with CTS

11. CSMA/CA All units on net receive CTS + time required Other units back off the time granted by AP Known as Point Coordination Function – PCF DCF is required by IEEE 802.11, PCF is not

12. Association / Reassociation Provides for migration from one BSS to another, as the node moves physically MAC layer provides

13. Radio Wave Transmissions FHSS versus DSSS On 2.400 – 2.483 GHz range Known as the ISM band (Industry, Scientific, Medical) Spread Spectrum Developed in WWII for security As apposed to narrowband

14. Spread Spectrum Radio transmission is transmitted on a greater bandwidth than the actual transmitted data. Resulting bandwidth is determined by a method other than by data transmitted. Up to 1000 times wider BW

15. FHSS versus DSSS FHSS – uses a narrowband transmission in the range of the SS transmission Both ends must know the starting frequency and the pattern used No data burst longer than 400 ms for one frequency. May skip from one to next May skip on preset pattern

16. FHSS versus DSSS DSSS uses pseudo-noise signal on all frequencies not used by data burst. Both ends know the algorithm for generating the pseudo-noise pattern Noise is removed at receiver, leaving data

17. What is Wi-Fi Wireless Ethernet Compatibility Alliance (WECA) produces products using IEEE 802.11b standard Wi-Fi extends to 11 Mbps Designed for both home/business wireless solutions

18. Security 802.11 standard is Wired Equivalent Privacy (WEP) Shared 40 bit key for security RC4 encryption algorithm Can be ‘broken’ easily Work is underway for WEP2 (IEEE 802.11e)

19. HomeRF A home version of wireless on 2.4G ISM band Uses FHSS technology SWAP 2.0 Shared Wireless Access Protocol 1.6Mbps

20. References IEEE 802.11 DSSS Overview http://www.wi- fi.com/downloads/weca80211boverview.pdfhttp://www.wi- fi.com/downloads/weca80211boverview.pdf IEEE 802.11 Technical Tutorial http://www.wi- fi.com/downloads/IEEE_80211_Primer.pdf http://www.wi- fi.com/downloads/IEEE_80211_Primer.pdf Reliability of IEEE 802.11 Hi Rate DSSS WLANs in a High Density Bluetooth Environment http://www.wi- fi.com/downloads/Coexistence_Paper_Intersil_ Aug18.pdfhttp://www.wi- fi.com/downloads/Coexistence_Paper_Intersil_ Aug18.pdf

21. Bluetooth Voice and Data Performance in 802.11 DSSS WLAN Environment http://www.wi- fi.com/downloads/BT_inf802_June_8.pdfhttp://www.wi- fi.com/downloads/BT_inf802_June_8.pdf Wi-Fi WEP Security Update http://www.wi- fi.com/pdf/Wi-FiWEPSecurity.pdfhttp://www.wi- fi.com/pdf/Wi-FiWEPSecurity.pdf Does Frequency Hopping Enhance Security? http://www.wi- fi.com/pdf/20010419_frequencyHopping.pdf http://www.wi- fi.com/pdf/20010419_frequencyHopping.pdf

22. Wi-Fi Security Update http://www.wi- fi.com/pdf/20011015_WEP_Security.pdf http://www.wi- fi.com/pdf/20011015_WEP_Security.pdf 802.15 Operating Rules, PDF http://grouper.ieee.org/groups/802/15/pu b/Rules/WPAN-Rules.pdf 802.15 Operating Rules, PDF http://grouper.ieee.org/groups/802/15/pu b/Rules/WPAN-Rules.pdf