1. Communication Research Labs Sweden AB Introduction to Wireless communication and WLAN

2. Communication Research Labs Sweden AB Background / History Two competitive standards: IEEE 802.11 ETSI HiperLan/2 IEEE 802.11 Ethernet based Standard in 1997 (2 Mbps) HiperLan/2 ATM based (Asynchronous Transfer Mode) Excellent support for Quality of Service Obsolete! IEEE – Institute for Electric and Electronic Engineers (USA) ETSI – European Telecommunication Standardization Institute (Europe) HIPERLAN - High Performance Radio Local Area Network.

3. Communication Research Labs Sweden AB Background / History In 1999, early IEEE 802.11 products suffered from interoperability problems. The Wi-Fi Alliance is a trade group consisting of almost all 802.11 equipment producers. (Over 260 members) Products with the Wi-Fi logo has been interoperability tested with other Wi-Fi products.

4. Communication Research Labs Sweden AB IEEE 802.11 Chip Vendors Most common chipset producers: Atheros Broadcom Intel Intersil (Prism) Proxim (Orinoco)

5. Communication Research Labs Sweden AB Different Types of Networks

6. Communication Research Labs Sweden AB Personal Area Network (PAN) The interconnection of devices within the range of an individualperson, typically within a range of 10 meters. Examples Interconnection of wearable computer components Connection of headset and head display with mobile phone Technologies for realization IrDA (Infrared) IEEE 802.15 Bluetooth, ZigBee, UltraWideband(UWB)

7. Communication Research Labs Sweden AB Local Area Network (LAN) A LAN supplies networking capability to a group of computers in close proximity to each other such as within an office environment. Examples Interconnection of printers, stationary and mobile devices within an office Internet access at university, airports etc. (Hot Spots) Interconnection of inHome entertainment Technologies for realization IEEE 802.11 (WLAN) Digital Enhanced Cordless Telephony (DECT)

8. Communication Research Labs Sweden AB Wireless Access Technologies Local/ Personal Area Networks DECT High Speed Vehicular Rural Vehicular Urban Pedestrian Indoor Fixed Urban Personal Area 0.010.1 1 10 100 1000 Data rate(Mb/s) IEEE 802.11b IEEE 802.11g IEEE 802.11a IEEE 802.11n IEEE 802.15.4 Zigbee IEEE 802.15.1 Bluetooth IEEE 802.15.3IEEE 802.15.3a Local Area Personal Area

9. Communication Research Labs Sweden AB Metropolitan Area Network (MAN) A MAN supplies networking capability to a city or metropolitan area. Examples Wireless interconnection of operator networks with WLAN Wireless DSL solution Broadband Wireless for last mile to connect homes through wireless to network operators Technologies for realization IEEE 802.16 WiMAX IEEE 802.11a/b/g (Mesh)

10. Communication Research Labs Sweden AB Wireless Access Technologies Metropolitan Area Network (MAN) High Speed Vehicular Rural Vehicular Urban Pedestrian Indoor Fixed Urban Personal Area 0.010.1 1 10 100 1000 Data rate(Mb/s) IEEE 802.11b IEEE 802.11g IEEE 802.11a IEEE 802.11n Metro Area WiMAX 801.16

11. Communication Research Labs Sweden AB Characteristics of Wireless Networks

12. Communication Research Labs Sweden AB Characteristics of Wireless Networks Frequency Regulation Useful spectrum almost occupied High Bit Error Rate and Packet Loss Rate Due to interference with engines, lightning etc. Shared Medium Communication High Delay and Jitter Due to high error rate, error control and MAC mechanisms Low data rate 54 Mbps in WLAN (shared), 53 kbps in GSM/GPRS

13. Communication Research Labs Sweden AB Signal Propagation Transmission Range Communication possible Low error rate Detection Range Detection of signal is possible No communication is possible Interference Range Signal may not be detected Increased background noise

14. Communication Research Labs Sweden AB The IEEE 802.11 Family

15. Communication Research Labs Sweden AB 802.11 LAN architecture Wireless host communicates with base station (or AP) Basic Service Set (BSS) (aka “cell”) in infrastructure mode use same frequency and contains: wireless hosts or station (STA) access point (AP): base station ad hoc mode: hosts only  IBSS (Independent Basic Service Set sharing same frequency Distribution System Interconnects several BSS to form a logical ESS (Extended Service Set).

16. Communication Research Labs Sweden AB IEEE 802.11 Overview Mobile terminal Access Point Fixed terminal

17. Communication Research Labs Sweden AB IEEE 802.11b Facts 2.4 GHz - 2.485 GHz divided into 11 channels at different frequencies Has 3 non-overlapping frequencies Approximately range: 38 meters indoors and 140 meters outdoors Data Rates 1 Mbit/s (legacy 802.11) 2 Mbit/s (legacy 802.11) 5.5 Mbit/s 11 Mbit/s

18. Communication Research Labs Sweden AB IEEE 802.11b (cont.) 802.11b and 802.11g equipment could occasionally suffer interference from microwave ovens or cordless telephones. Bluetooth devices, while operating in the same 2.4 GHz band, do not interfere with 802.11b and 802.11g (in theory!): frequency hopping spread spectrum signaling method for BT (FHSS) VS direct sequence spread spectrum signaling method (DSSS) for 802.11.

19. Communication Research Labs Sweden AB IEEE 802.11g Facts 2.4 GHz - 2.485 GHz divided into 11 channels at different frequencies Has 3 non-overlapping frequencies Approximately range: 38 meters indoors and 140 meters outdoors Data Rates 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s

20. Communication Research Labs Sweden AB IEEE 802.11a Facts 5.15 GHz – 5.25 GHz / 5.25 GHz – 5.35 GHz 5.49 GHz – 5.725 GHz / 5.725 GHz – 5.85 GHz Has 23 non-overlapping frequencies Approximately range: 35 meters indoors and 120 meters outdoors 802.11a devices are never affected by products operating on the 2.4 GHz band Reasonably free from interference Data Rates 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s

21. Communication Research Labs Sweden AB Hidden and exposed terminal problems BAC Range of terminal A Range of terminal C will collide with transmission from A at B Hidden Terminal Problem ACBD Range of terminal B Range of terminal C Exposed Terminal Problem cannot send to D due to carrier sense currently transmitting wants to transmit

22. Communication Research Labs Sweden AB IEEE 802.11: Multiple Access Avoid collisions: 2+nodes transmitting at same time 802.11: CSMA - sense before transmitting Don’t collide with ongoing transmission by other node 802.11: no collision detection! difficult to receive (sense collisions) when transmitting due to weak received signals (fading) can’t sense all collisions in any case: hidden terminal, fading goal: avoid collisions: CSMA/CA (Collision Avoidance)

23. Communication Research Labs Sweden AB 802.11 frame: addressing Frame control duration 22 Address 1 Address 2 Address 3 seq control Address 4 payload 66 6 620-2312 CRC 4 Address 1: MAC address of wireless host or AP to receive this frame. Used by stations to filter packets Address 2: MAC address of wireless host or AP transmitting this frame. Receiver thus identifies ACK target Address 3: MAC address of router interface to which AP is attached. Depends on To and From bits in Frame control field Address 4: used only in ad hoc mode to identify original source of WDS (wireless distribution system) frames

24. Communication Research Labs Sweden AB 802.11 MAC Layer Overhead Data rate (Mbps)Approximate Throuput (Mbps) 802.11b116 802.11g (802.11b in cell)548 802.11g (no 802.11b in cell)5422 802.11a5425 Source: Cisco Systems, Inc. Network Capacity Approximations for 802.11b, 802.11g and 802.11a

25. Communication Research Labs Sweden AB Wireless Security

26. Communication Research Labs Sweden AB Wireless Security MAC-address filtering SSID Broadcast Authentication Encryption

27. Communication Research Labs Sweden AB Wireless Security - WEP WEP (Wired Equivalent Privacy) Part of the 802.11 standard Encryption standard: RC4

28. Communication Research Labs Sweden AB Wireless Security - WPA WPA (Wi-Fi Protected Access) Encryption standard: RC4 Authentication Encryption Pre-shared Key (PSK) IEEE 802.1x (authentication server)

29. Communication Research Labs Sweden AB Wireless Security – WPA2 WPA2 (Wi-Fi Protected Access) – IEEE 802.11i Encryption standard: AES Authentication Encryption Pre-shared Key (PSK) IEEE 802.1x (authentication server)

30. Communication Research Labs Sweden AB Wireless Security – Other Higher layer security measures such as: IPSec SSL...