WiMAX. Robert Bestak. Czech Technical University in Prague Faculty of Electrical Engineering. PDF vytvořeno zkušební verzí pdffactory

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1 WiFi WiMAX Robert Bestak Czech Technical University in Prague Faculty of Electrical Engineering

2 IEEE wireless standards (1/2) WG Wireless Local Area Network WG Wireless Personal Area Network WG Broadband Wireless Access a n a e WG Mobile Broadband Wireless Access WG Wireless Regional Area Network *IEEE: Institute of Electrical and Electronics Engineers 2007, December 10 R. Bestak 2

3 IEEE wireless standards (2/2) WiFi WiMAX WG Wireless Local Area Network WG Wireless Personal Area Network WG Broadband Wireless Access a n a e WG Mobile Broadband Wireless Access Bleutooth ZigBee WG Wireless Regional Area Network 2007, December 10 R. Bestak 3

4 WiFi

5 IEEE protocol model Transport layer UDP TCP SCTP DCCP IETF Network layer IPv4, IPv6 ICMP Data Link layer Physical layer Logical Link Control (LLC) Medium Access Control (MAC) a b g n IEEE 802 IEEE * IETF: Internet Engineering Task Force 2007, December 10 R. Bestak 5

6 IEEE Wireless Fidelity IEEE , Wireless LAN Indoor (offices, buildings, not well suited for outdoor BWA) Originally did not support QoS WiFi Alliance Manufactures of WiFi equipments Testing, certification, promotions of technology Equipments before standard ( problems with interoperability,...) Products certified by WiFi Alliance are provided with logo 2007, December 10 R. Bestak 6

7 Architecture of WiFi Distribution System Interconnection of APs Access Point Provides wireless access to distribution system Station Terminal equipped with a radio module Medium Air Medium Distribution System Access Point Station 2007, December 10 R. Bestak 7

8 Network architecture AP AP AP Infrastructure Wireless Distribution System AP Ad-Hoc Mesh 2007, December 10 R. Bestak 8

9 Layers Network layer Data Link layer IP Logical Link Control (LLC) Medium Access Control (MAC) Physical layer IR DSSS FHSS a,g OFDM b HR-DSSS 2007, December 10 R. Bestak 9

10 Physical layer Standard PHY Frequency Data rates [Mbit/s] FHSS, DSSS 2,4 GHz; IR 1; b HR-DSSS 2,4 GHz 1; 2; 5,5; g OFDM 2,4 GHz 6, 9, 12, 18, 24, 36, 48, a/h OFDM 5,2; 5,5GHz 6, 9, 12, 18, 24, 36, 48, 54 Transmission rate Depends on modulation Dynamically varies according to quality of received signal ( quality rate ) Due to protection, the user data rate is about one half 2007, December 10 R. Bestak 10

11 IEEE b/g Number of channels: CZ 13 channels (2,412 GHz 2,472 GHz) Channels are shared Channel bandwidth: 22 MHz Distance between channels: 5 MHz EIRP: 100 mw(20 dbm) EIRP (Equivalent IsotropicallyRadiated Power) 22 MHz only 3 non-overlapped channels f [MHz] 2007, December 10 R. Bestak 11

12 MAC MAC implements access methods Network layer Data Link layer IP Logical Link Control (LLC) Medium Access Control (MAC) Physical layer IR DSSS FHSS a,g OFDM b HR-DSSS 2007, December 10 R. Bestak 12

13 CSMA CSMA CarrierSenseMultipleAccess Rules: Carrier ==> do not transmit No carrier ==> OK to transmit But the above rules do not always apply to wireless environment Solution: RTS/CTS Collision detection (CD) Ethernet Does not work over wireless (stations can not here each other) Therefore, family uses CA Collision avoidance (CA) Random backoff Priority ackprotocol 2007, December 10 R. Bestak 13

14 DCF (Distributed Coordination Function) Busy medium DIFS CW Backoff Next frame Slot time FHSS (50μs), DSSS (20 μs) IFS - Interframe Space DIFS - DCF IFS SIFS - Short IFS, SIFS<DIFS SIFS=10μs (DSSS) CW - Congestion window (Random number 0-CWmax) DIFS SIFS DIFS Source station CW [5] Frame Destination station Ack Station close to Source CW [10] Listen CW [5] Frame Time 2007, December 10 R. Bestak 14

15 Problem of DCF CSMA/CA problem of hidden node Reduction of communication about 40% Mainly case of large area and use of omni-directional antennas AP Source station CW [5] Frame Destination station Station A Station C Station close to Source CW [10] Listen Station B Station close to Destination CW [12] Frame Station A does not hear the communication AP/Station C ( hidden node) Collision at destination Time 2007, December 10 R. Bestak 15

16 RTS/CTS method RTS/CTS (Request To Sent / Clear To Sent) Eliminates problem of hidden node Collision can only occur when sending RTS packet Effective only for long packets (for short packet is used the basic mechanism) DIFS SIFS SIFS SIFS DIFS SIFS Source station CW [5] RTS Frame CW [10] NAV from RTS Destination station CTS Ack RTS Station close to Source CW [10] NAV (Net Allocation Vector) from RTS CW [5] RTS Station close to Destination NAV from CTS NAV Time 2007, December 10 R. Bestak 16

17 Standards Standard Release date Frequency [GHz] Max. data rate [Mbit/s] Notes ,4 2 Original version c 1998 Bridge operation procedure; this work is now part of 802.1D a OFDM b , d 2001 For countries that don t support 2,4 GHz frequency bands F 2003 Provides wireless access point communications among multi-vendor systems; trial use recommendation withdrawal in g ,4 54 HW is compatible with b h 2003 Spectrum Management of a for European compatibility; dynamic frequency selection and transmit power control i 2004 Security j ,9-5 FFor Japanese market e 2005 QoS enhancements (EDCA, HCCA, etc.) m 2007 Maintenance of the standard Includes amendments a, b, d, e, g, h, i & j k 2007? Radio resource management enhancement r 2007? Fast Roaming / Fast BBS Transition n 2008? 2,4 and/or 5 74 MIMO p 2009? Wireless access in the vehicular environment s 2008? Mesh topology u 2009? Interworking with non-802 networks (e.g., cellular network) w 2008? Increase of security of management frames y 2008? 3,65-3,7 For U.S. market 2007, December 10 R. Bestak 17

18 WiMAX

19 WiMAX Access networks (last mile) metallic cables, optical cables, radio WiMAX a) Substitution of cables b) Mobile network 2007, December 10 R. Bestak 19

20 Wireless Access WiMAX Worldwide Interoperability for Microwave Access IEEE ( st version of standard) BWA Outdoor ( metropolitan access network) Support of QoS WiMAX Forum Founded 2001 Non-profit industry trade organization Around 350 members (e.g., Alcatel, Intel, Nortel, Alvarion, etc.) Goal Promotion & certification of equipments Specification of tests ( according to standards, interoperability) Selection of labs for certification , December 10 R. Bestak 20

21 Frequency bands (1/2) Unlicensed / licensed spectrum GHz Line of Sight (LOS) Cell radius -up to 40 50km 2-11 GHz Non Line of Sight (NLOS) Cell radius -up to 7 9 km power management, MIMO Focus on 3,5 GHz and 5,8 GHz bands Note:Unlicensed spectrum + Free, allows quickly meet the needs of users -To eliminate interferences, arrangement between providers is needed 2007, December 10 R. Bestak 21

22 Frequency bands (2/2) 2007, December 10 R. Bestak 22

23 versions (1/2) /12 LOS (10-66 GHz), up to 135 Mbit/s c a 2003/01 NLOS (2-11 GHz), up to 75 Mbit/s REVd ( ) 2004/ e 2005/12 NLOS (to 6 GHz) Mobility 2007, December 10 R. Bestak 23

24 Features Flexible channel size 1,75 MHz 20, 28 MHz ( 1,75; 3,5; 5; 7; 10; )...increase of cell capacity in the network High data rates Over 100 Mbit/s (depends on the channel bandwidth) QoS support..support low latency applications (e.g., voice or video) Support of tents of users under one Base Station Ch 1 Ch 2 Ch 3 Ch 4 Bandwidth of operator (e.g., 14 MHz) 2007, December 10 R. Bestak 24

25 Topologies Point-To-Multipoint Mesh FSS Base Station IP/ATM networks Mesh SS (Fix) Mesh BS IP/ATM networks Mobile Subscriber Station (802.16e) Fix Subscriber Station FSS Mesh SS (Mobile) Mesh SS (Fix) Mesh SS (Fix) Communication between SSs through BS Communication between SSs with/without BS 2007, December 10 R. Bestak 25

26 Modes (1/2) FDD f x for downlink, f y for uplink Fixed duration frame TDD f x for both downlink and uplink Fixed duration frame, variable size of downlink & uplink sub-frame Frame j Frame j+1 Frame j+2 downlink uplink adaptive Physical slot 2007, December 10 R. Bestak 26

27 Services Type Description Ex. Unsolicited Grant Service UGS Real-time data transmission -fixed packet size, periodic transmission Voice, VoIP real-time Polling Service rtps Real-time data transmission -variable packet size, periodic transmission MPEG video Extended rtps ErtPS Real-time data transmission Detection of voice activity non-real-time Polling Service nrtps Non real-time data transmission -variable packet size, min. transmission rate FTP Best Effort BE Web-browsing 2007, December 10 R. Bestak 27

28 Layers in WiMAX Service Specific Convergence Sublayer (CS) MAC MAC Common Part Sublayer (CPS) Security Sublayer (SS) PHY Physical Layer 2007, December 10 R. Bestak 28

29 Physical layer (1/3) 2-11 MHz i) OFDM (256 carriers) ii) OFDMA (2048 carriers) iii) Single carrier MHz i) Single carrier e SOFDMA (Scalable OFDMA) 2007, December 10 R. Bestak 29

30 Physical layer (3/3) Adaptive Modulation &Coding (AMC) QPSK, 16QAM, 64QAM Convolution code Turbo code Hybrid ARQ (HARQ) N x Stop&Wait Chase combining, Incremental redundancy Advance antennas techniques Beamforming STC (Space Time Coding) MIMO (Multiple Input Multiple Output) 2007, December 10 R. Bestak 30

31 SS (Security Sublayer) Identification of user/equipment EAP (Extensible Authentication Protocol) SIM, USIM, login + password Ciphering of data AES (Advanced Encryption Standard) Secure key exchange PKMv2 (Privacy and Key Management Protocol version 2) ATM ATM CS IP PPP Packet CS MAC CPS SS Physical layer 2007, December 10 R. Bestak 31

32 MAC CPS (MAC Common Part Sublayer) Connection establishment/maintenance/termination Assignment of radio resources Transmission of data (voice, audio, video) over the radio interface HARQ N x Stop&Wait ATM ATM CS IP PPP Packet CS MAC CPS SS Physical layer 2007, December 10 R. Bestak 32

33 CS (Service specific Convergence Sublayer) Interface between CPS and upper layers (IP, ATM, etc.) Transformation and mapping of upper layer data Classification of upper layer data into appropriate flows (CID) Payload header suppression/restoration ( option) Types ATM CS Packet CS (IP, PPP, Ethernet, etc.) ATM IP PPP ATM CS Packet CS MAC CPS SS Physical layer 2007, December 10 R. Bestak 33