1. IWD2243 Wireless & Mobile Security Chapter 1 : Wireless Fundamentals Prepared by : Zuraidy Adnan, FITM UNISEL1

2. 1.1 Wireless Medium Prepared by : Zuraidy Adnan, FITM UNISEL2  Radio Propagation Effects  Harsh medium for signal propagation  Distance between transmitter & receiver  Physical environment  Relative movement between transmitter & receiver  Attenuation : drop in signal strength as the signal propagates in any medium.  Near (1/r 2 ) & Far (1/r 4 )

3. 1.1 Wireless Medium (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL3  Shadow fading (slow fading) : Changes in the signal strength occurring due to the changes in operating environment.  Raleigh fading (fast fading) : Changes in signal strength due to the relative motion of the order of a few centimeters.  Inter-symbol interference – effect of multipath

4. 1.1 Wireless Medium (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL4  Hidden terminal problem  See figure 1.1b page 6  Collisions of node A and C while reaching B  Exposed terminal problem  See figure 1.1c page 7  Node C senses the medium and find it busy since node B has start transmitting

5. 1.1 Wireless Medium (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL5  Bandwidth  Bandwidth is always expensive (in wireless)  Almost all countries the wireless spectrum is controlled by government  Only certain band are allowed for commercial use  All protocol designed revolve around this constraint  Other constraint  Trend – wireless need to be mobile  Small devices – limited processing power, limited battery life

6. 1.2 Wireless Networking Basics Prepared by : Zuraidy Adnan, FITM UNISEL6  Wireless Local Area Network (WLAN)  1997 – IEEE – 802.11 WLAN standard – 2Mbps  1999 – IEEE – 802.11b – 11Mbps – 2.4Ghz band  Small area coverage – office building  Security features – encryption, frequency hopping, firewalls  Drawback – high initial cost, limited range, possibility of mutual interference, the need to security-enabled client  LANs and WLAN – OSI model  See figure 1.2 page 10

7. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL7  WLAN – advantages & disadvantages  See page 12 & 13 chapter 1  Current WLAN standard  802.11a – 5GHz, compatible with 802.11b  Signal interference by 802.11b user  802.11b (Wi-Fi) – 2.4Ghz band – 11Mbps – 4 to 7Mbps  Some manufacturers – 802.11b – 22Mbps  Future WLAN standard  IEEE – 802.11g – 2.4Ghz band – 54Mbps  IEEE – 802.11h – 5Ghz band – 54Mbps – enhancement of 802.11a – TPC (limit power) – DFS (protect sensitive freq.)

8. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL8  Bluetooth & WPAN  Point to point, point to multipoint piconets – adhoc.  Flexible net topology, low energy consumption, robust data capacity, high quality voice transmission.  Speed – 1Mbps, 10 meters  Ultra wideband  UWB – > 100Mbps - < 10 meters.

9. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL9  Security for WLANs  802.11i – security standard for 802.11a,b,g.  Replace WEP with TKIP, AES, and 802.1 x authentication.  Incorporated into IEEE 802.11-2007 standard.  Wi-Fi alliance – Wi-Fi Protected Assets (WPA), before 802.11i finalized.  WEP – 40bit, 60bit, 128bit encryption key.  All devices has to be set to use same encryption key.  Slow data transfer rate – up to 30%

10. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL10  SSID – method to identify or name an individual WLAN  Service Set Identifier – 32 char unique identifier.  Device level pass – connect to BSS – diff 1 WLAN to another – known also as network name.  Step to secure WLAN  See page 17 & 18 chapter 1.

11. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL11  WLANs performance  Transmission speed – file size, number of users, distance from access points.  Performance vary – number of users, local environment, obstructions that are in the way.  WLAN implementation concerns  Planning – Floor plan, site survey  Capacity – 1 access point, 15-20 users

12. 1.2 Wireless Networking Basics (cont.) Prepared by : Zuraidy Adnan, FITM UNISEL12  Performance – 802.11b, 350 meters outdoors, very much reduce indoors.  Interference – bluetooth connectivity (handheld device, mobile phones in the same area)  Building work – installation of metal storage cabinets, microwave ovens, fish tanks.  Power consumption – 802.11a, limited power output.  Power over Ethernet (PoE) – removing the need to install additional power cabling.