Communication Research Labs Sweden AB Introduction to Wireless communication and WLAN

Communication Research Labs Sweden AB Background / History Two competitive standards: IEEE ETSI HiperLan/2 IEEE 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.

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

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

Communication Research Labs Sweden AB Different Types of Networks

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 Bluetooth, ZigBee, UltraWideband(UWB)

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 (WLAN) Digital Enhanced Cordless Telephony (DECT)

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 Data rate(Mb/s) IEEE b IEEE g IEEE a IEEE n IEEE Zigbee IEEE Bluetooth IEEE IEEE a Local Area Personal Area

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 WiMAX IEEE a/b/g (Mesh)

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

Communication Research Labs Sweden AB Characteristics of Wireless Networks

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

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

Communication Research Labs Sweden AB The IEEE Family

Communication Research Labs Sweden AB 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).

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

Communication Research Labs Sweden AB IEEE b Facts 2.4 GHz 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 ) 2 Mbit/s (legacy ) 5.5 Mbit/s 11 Mbit/s

Communication Research Labs Sweden AB IEEE b (cont.) b and g 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 b and g (in theory!): frequency hopping spread spectrum signaling method for BT (FHSS) VS direct sequence spread spectrum signaling method (DSSS) for

Communication Research Labs Sweden AB IEEE g Facts 2.4 GHz 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

Communication Research Labs Sweden AB IEEE a Facts 5.15 GHz – 5.25 GHz / 5.25 GHz – 5.35 GHz 5.49 GHz – GHz / GHz – 5.85 GHz Has 23 non-overlapping frequencies Approximately range: 35 meters indoors and 120 meters outdoors a 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

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

Communication Research Labs Sweden AB IEEE : Multiple Access Avoid collisions: 2+nodes transmitting at same time : CSMA - sense before transmitting Don’t collide with ongoing transmission by other node : 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)

Communication Research Labs Sweden AB frame: addressing Frame control duration 22 Address 1 Address 2 Address 3 seq control Address 4 payload 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

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

Communication Research Labs Sweden AB Wireless Security

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

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

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)

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

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