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  1. 3.- Wireless technologies Basics Applications The physical media Free-space loss and frequency dependency The IEEE 802 specification family Comparison between different wireless technologies (PHY and MAC layers) IEEE 802.11 Bluetooth

  2. Wireless? Why? • Mobility (anytime) • Coverage (anywhere) • New applications potential (services) • Healthcare • Lab administration • People with disabilities • Point-of-Care testing • Homecare administration • Controlling patient data • Education • More efficient learning methods • Wireless is ideal for campus-wide coverage

  3. Some Application Areas • Retail • Direct inventory management • Mobile POS • Self-checkout • Mobile scanners • Manufacturing • Field based data collections • Product management • Inventory visibility and planning

  4. Vehicular Networks • Safetyandtransportefficiency • InEuropearound 40,000 peopledieandmore than 1.5 millionsare injuredeveryyearontheroads • Trafficjamsgenerate a tremendouswasteoftimeandoffuel • Mostoftheseproblemscanbesolvedbyprovidingappropriateinformationtothedriverortothevehicle

  5. VehicleCommunication (VC) • VC promisessaferroads, • … more efficient driving,

  6. VehicleCommunication (VC) • … more fun, • … and easier maintenance.

  7. Rural communications • Rural communications on the global agenda • Connecting villages with Information and Communication Technologies (ICT) and establishing community access points • Benefits • E-business and e-commerce could play an important role in enabling local artisans to reach national and international markets Over 40% of the world’s population lives in rural and remote areas of developing countries and have difficult or no access to even basic telecommunications services. Development of telecommunications in rural and remote areas, therefore forms an important mission of the ITU Development sector. Yasuhiko Kawasumi, “Rural communications on the global agenda,” Global Survey on Rural Communications for the ITU-D on Communications for rural and remote areas.

  8. Rural populations and their ICT needs • Needs of rural people in connection with e-services • E-health, e-education and e-administration top the list as primary needs • E-business and e-banking also scored highly ITU-D global survey, Doc 111/SG2 For many rural areas, electricity supply is simply non-existent or insufficient Telemedicine Training in Bhutan by Tokai University: Tokai University Institute of Medical Sciences donated the medical equipments with ICT functions and provided the training on the use of equipments. Tokai University Second Opinion center provides the assistance service over the internet when requested by the Bhutanese ends.

  9. About the “Wireless Internet” Bluetooth RFID WWAN (3G,4G?) Low throughput, Long range WMAN (Wi-Max) WLAN (Wi-Fi) High throughput, short range Low throughput, short range WPAN

  10. Big Picture – WPAN’s • WPAN technologies – RFID, Bluetooth • RFID used in tagging applications, restricted environments (supermarkets, institutions) • 10 billion RFID tags to be sold by the end of 2005 (source: Deloitte & Touche) • Bluetooth – technology has matured • 56% of mainstream devices commercialised will have Bluetooth support by 2008 (Source: IDC) • Poor interoperability between vendors restricts the wide use of Bluetooth

  11. Big Picture – WLAN’s • WLAN – based on WiFi (802.11x) • Adoption rate increased worldwide • Up 51% more units sold globally in 2004 compared to 2003 (source: Infonetics Research) • European cities’ infrastructure facilitates the adoption of WiFi against wired alternatives • Old buildings • High population density • Poor telecommunications infrastructure • Wi-Fi mesh infrastructure: • Current backend implementations of Wi-Fi mesh infrastructure are based on proprietary solutions • Usage: wireless coverage of WLANs, blanketing large areas with hot-spot coverage • Coverage: 100m to 10km • Data rate:54Mbps- 100Mbps

  12. Big Picture –WMAN’s • WiMax (Worldwide Interoperability for Microwave Access) • Standards-based technology • Deployment of broadband wireless networks based on the IEEE 802.16 standard • Enables the delivery of last mile wireless broadband access as an alternative to cable and DSL • Some characteristics of the 802.16- 2004 standard: • Improve user connectivity • Higher quality of services • Full support for WMAN service • Robust carrier-class operation

  13. Download Speed 1-10 Mbps 250-384 kbps 90-180 kbps 40 kbps Big Picture –WMAN’s Mobile Networks Evolution 4G HSDPA UMTS 3G 2G EDGE GPRS 2015 1995 2005

  14. 3.- Wireless technologies Basics Applications The physical media Free-space loss and frequency dependency The IEEE 802 specification family Comparison between different wireless technologies (PHY and MAC layers) IEEE 802.11 Bluetooth

  15. Antennas basics • Directional Antenna • "An antenna having the property of radiating or receiving electromagnetic waves more effectively in some directions than others". • Omni-Directional Antenna • "A hypothetical, lossless antenna having equal radiation intensity in all directions". For a WLAN antenna, the gain in dBi is referenced to that of an omni-directional (isotropic) antenna (which is defined as 0 dBi). YAGI Directional Antenna

  16. Directional antennas Yagi antenna (13,5 dBi) reach: 6 Km at 2 Mb/s 2 Km at 11 Mb/s Parabolic antenna (20 dBi) reach: 10 Km at 2 Mb/s 4,5 Km at 11 Mb/s

  17. More antennas examples Horizontal Radiation

  18. ISM frequency bands ISM (Industrial, Scientific and Medical) frequency bands: • 900 MHz band (902 … 928 MHz) • 2.4 GHz band (2.4 … 2.4835 GHz) • 5.8 GHz band (5.725 … 5.850 GHz) Anyone is allowed to use radio equipment for transmitting in these bands (provided specific transmission power limits are not exceeded) without obtaining a license.

  19. ISM frequency band at 2.4 GHz The ISM band at 2.4 GHz can be used by anyone as long as (in Europe...) Transmitters using FH (Frequency Hopping) technology: • Total transmission power < 100 mW • Power density < 100 mW / 100 kHz ETSI EN 300 328-1 requirements Transmitters using DSSS technology: • Total transmission power < 100 mW • Power density < 10 mW / 1 MHz

  20. Free-space loss The free-space loss L of a radio signal is: where d is the distance between transmitter and receiver,  is the rf wavelength, f is the radio frequency, and c is the speed of light. The formula is valid for d >> , and does not take into account antenna gains (=> Friis formula) or obstucting elements causing additional loss.

  21. Power budget graphical representation

  22. 3.- Wireless technologies Basics Applications The physical media Free-space loss and frequency dependency The IEEE 802 specification family Comparison between different wireless technologies (PHY and MAC layers) IEEE 802.11 Bluetooth

  23. IEEE 802 wireless network technology options Network definition Wireless personal area network (WPAN) Low-rate WPAN (LR-WPAN) Wireless local area network (WLAN) Wireless metroplitan area network (WMAN) IEEE standard IEEE 802.15.1 IEEE 802.15.4 IEEE 802.11 IEEE 802.16 Known as Bluetooth ZigBee WiFi WiMAX

  24. IEEE 802 standardisation framework 802.1 Manage-ment 802.2 Logical Link Control (LLC) 802.3 MAC 802.5 MAC 802.11 Medium Access Control (MAC) CSMA/CA 802.3 PHY 802.5 PHY 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY CSMA/CD (Ethernet) Token Ring CSMA/CA (Wireless LAN)

  25. A common MAC layer, but many PHY options CSMA/CA Wireless LAN CSMA/CA = Carrier Sense Multiple Access with Collision Avoidance Unlike wired LAN stations, WLAN stations cannot detect collisions => avoid collisions 802.11 Medium Access Control (MAC) CSMA/CA 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY

  26. WLAN physical layer (1) The original physical layer specified in 802.11 defines two signal formats: FHSS (Frequency Hopping Spread Spectrum) 802.11 Medium Access Control (MAC) CSMA/CA Outdated, never implemented DSSS (Direct Sequence Spread Spectrum) 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY Data rates supported: 1 and 2 Mbit/s. ISM band: 2.4 … 2.4835 GHz

  27. WLAN physical layer (2) The first widely implemented physical layer was 802.11b that uses: DSSS (Direct Sequence Spread Spectrum) like in 802.11 but with larger bit rates: 1, 2, 5.5, 11 Mbit/s 802.11 Medium Access Control (MAC) CSMA/CA Becoming outdated 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY Automatic fall-back to lower speeds in case of bad radio channel. ISM band: 2.4 … 2.4835 GHz

  28. WLAN physical layer (3) 802.11a operates in the 5.8 GHz band. The signal format is OFDM (Orthogonal Frequency Division Multiplexing) Data rates supported: Various bit rates from 6 to 54 Mbit/s. 802.11 Medium Access Control (MAC) CSMA/CA Not too used in Europe 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY 5 GHz frequency band

  29. WLAN physical layer (4) 802.11g is the most recent physical layer, operating in the same band as 802.11b The signal format is OFDM (Orthogonal Frequency Division Multiplexing) Data rates supported: Various bit rates from 6 to 54 Mbit/s (same as 802.11a) 802.11 Medium Access Control (MAC) CSMA/CA 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY ISM band: 2.4 … 2.4835 GHz

  30. Wireless Fidelity (WiFi) The WiFi certification program of the Wireless Ethernet Compatibility Alliance (WECA) addresses compatibility of IEEE 802.11 equipment => WiFi ensures interoperability of equipment from different vendors. 802.11 Medium Access Control (MAC) CSMA/CA 802.11 PHY 802.11a PHY 802.11b PHY 802.11g PHY WiFi5 WiFi

  31. Wireless Personal Area Network (WPAN) 802.1 Manage-ment 802.2 LLC 802.15.1 MAC + PHY 802.15.4 MAC + PHY 802.16 MAC + PHY 802.3 MAC 802.5 MAC 802.11 MAC Data rates up to 700 kbit/s (2.1 Mbit/s) 802.3 PHY 802.5 PHY 802.11 PHY ISM band: 2.4 … 2.4835 GHz Bluetooth Special Interest Group (SIG)

  32. Low-rate WPAN (LR-WPAN) 802.1 Manage-ment 802.2 LLC 802.15.1 MAC + PHY 802.15.4 MAC + PHY 802.16 MAC + PHY 802.3 MAC 802.5 MAC 802.11 MAC Data rates up to 250 kbit/s 802.3 PHY 802.5 PHY 802.11 PHY ISM band: 2.4 … 2.4835 GHz ZigBee Alliance

  33. Wireless Metropolitan Area Network (WMAN) 802.1 Manage-ment 802.2 LLC 802.15.1 MAC + PHY 802.15.4 MAC + PHY 802.16 MAC + PHY 802.3 MAC 802.5 MAC 802.11 MAC Various data rates up to 100 Mbit/s and more 802.3 PHY 802.5 PHY 802.11 PHY Various frequency bands (not only ISM) WiMAX

  34. 3.- Wireless technologies Basics Applications The physical media Free-space loss and frequency dependency The IEEE 802 specification family Comparison between different wireless technologies (PHY and MAC layers) IEEE 802.11 Bluetooth

  35. Possible architectures • Independent Basic Service Set (IBSS) • Decentralized structure • Flexible: • Permanent and temporary networks • Allows to control power consumption • infrastructure Basic Service Set (BSS) • Components: • Station (STA) • Access Point (AP)or Point Coordinator (PC) • Basic Service Set (BSS) • Extended Service Set (ESS)

  36. BSS AP WLAN LAN The Extended Service Set (ESS) Distribution System (DS) • The standard does not define the implementation details • exists a proposal by a group of industries:Inter-acces point protocol (IAPP)

  37. Task Group f • Scope of Project: to develop recommended practices for an Inter-Access Point Protocol (IAPP) which provides the necessary capabilities to achieve multi-vendor Access Point interoperability across a Distribution System supporting IEEE P802.11 Wireless LAN Links. • Purpose of  Project: ... including the concepts of Access Points and Distribution Systems. Implementation of these concepts where purposely not defined by P802.11 ... As 802.11 based systems have grown in popularity, this limitation has become an impediment to WLAN market growth. This project proposes to specify the necessary information that needs to be exchanged between Access Points to support the P802.11 DS functions. The information exchanges required will be specified for, one or more Distribution Systems; in a manner sufficient to enable the implementation of Distribution Systems containing Access Points from different vendors which adhere to the recommended practices • Status: Work has been completed and is now part of the Standard as a recommended practice.

  38. Función To DS From DS Addr. 1 Addr. 2 Addr. 3 Addr. 4 IBSS 0 0 RA = DA SA BSSID - From the AP 0 1 RA = DA BSSID SA - To the AP 1 0 RA = BSSID SA DA - Wireless DS 1 1 RA TA DA SA Frames structure Types of addresses: • Source address (SA) • Destination Address (DA) • Transmitter Address (TA) • Receiver Address (RA) • BSS identifier (BSSID) • management (00) • control (01), • data (10), • reserved (11)

  39. BSSID y SSID • BSSID (Basic Service Set Identity) • BSS: AP’s MAC address • Ad-Hoc: 46 bit random number • SSID (Service Set ID) • Known as the Network Name • Length: 0~32 bytes • 0: is the broadcast SSID • Handled either manually or automatically • Should be unique; used to distinguish WLAN • Access point and station that would like to form a unique WLAN should use the same SSID

  40. Función To DS From DS Addr. 1 Addr. 2 Addr. 3 Addr. 4 IBSS 0 0 RA = DA SA BSSID - From the AP 0 1 RA = DA BSSID SA - To the AP 1 0 RA = BSSID SA DA - Wireless DS 1 1 RA TA DA SA Addressing and DS bits DS TA RA (BSSID) SA/TA AP AP SA RA Client AP DA Client DA Server Server

  41. Services • The IEEE 802.11 architecture defines 9 services: for the station and for the distribution • Station services: • Authentication • Deauthentication • Privacy  WEP • Data delivery • Distribution services: • Association  generates a connection between a STA and a AP • Disassociation • Reassociation  like association but informing about the previous AP • Distribution • integration  connects the WLAN with other LANs; Similar to connect/disconnect a cable to a traditional network

  42. State variables and services In a IBSS there is neither auth., nor ass. Data service is allowed State 1: unauthenticated, unassociated Class 1 frames Successful authentication Deauthentication notification State 2: authenticated, unassociated Class 1 & 2 frames Deauthentication notification Successful authenticationor reassociation Disassociation notification State 3: authenticated, associated A STA can be authenticated with various AP but it can be associated with only one AP Class 1, 2 & 3 frames

  43. Scanning • Parameters: BSStype, BSSID, SSID, ScanType, ChannelList, ProbeDelay, Min/MaxChannelDelay • ScanType: Passive • The stations wait for the APs beacons • ScanType: Active • Stations send probe requests • scan report are generated • The following phase is joining; this phase precedes the sequence of actions up to association

  44. With contention No contention Point CoordinationFunction (PCF) MAC Distributed Coordination Function (DCF) DIFS DIFS Contention window PIFS busy medium SIFS slot defer access The MAC: reliable data delivery • CSMA/CA with binary exponential backoff • The minimum protocol consists of two frames: the data and the ACK The 5 timing values: • Slot time • SIFS: short interframe space (< slot time) • PIFS: PCF interframe space (=SIFS+1slot) • DIFS: DCF interframe space (=SIFS+2slots) • EIFS: extended interframe space

  45. B1 = 25 B1 = 5 wait data data wait B2 = 10 B2 = 20 B2 = 15 DCF behaviour • The back off values are chosen inside the congestion window. That is, inside the interval [0, CW] • CW can vary between 31 slots (CWmin) and 1023 slots (CWmax) • CW is incremented after every failed sending and reset after every successful transmission • B1 and B2 are the back off interval at STA 1 and 2 • CW = 31

  46. Hidden node Exposed node Problematic configurations A A B C B C D

  47. SIFS SIFS SIFS RTS/CTS mechanism • Based on the network allocation vector (NAV) DIFS data RTS source ACK destination CTS DIFS NAV (RTS) Contention window other STA NAV (CTS) defer access

  48. PIFS SIFS SIFS SIFS PIFS SIFS SIFS PC Data+Poll Data+Poll Data+Poll CF-End Beacon DATA+ACK ACK SIFS (no response) STA1 CP Contention Free Period CP NAV Reset STA2 Station 2 sets NAV(Network Allocation Vector) Station 3 is hidden to the PC, it does not set the NAV. It continues to operate in DCF. STA3 Time PCF: Point Coordination Function • Beacons are used to keep timers in the stations synchronized and to send control information • The AP generates beacons at regular intervals • Stations know when the following beacon is arriving • The target beacon transmission time (TBTT) is announced in the previous beacon

  49. 802.11 periodic Superframe CFP(Contention Free Period) CP(Contention Period) CF-End CF-Poll PC Beacon STAs DATA DATA DATA DATA DATA DATA PCF: the superframe • There is an repetition of contention-free (CFP) and contention (CP) periods • A CFP and the following CP form a superframe.

  50. Broadcast trafic • It is not possible to fragment frames whose destination is a group address • Acknowledgement are not sent • MAC does not offer any retransmission service to broadcast or multicast frames