RADIO SYSTEMS – ETI 051 Lecture no: 12 Centralized and AdHoc networks Wireless LAN Ove Edfors, Department of Electroical and Information Technology Ove.Edfors@eit.lth.se 2010-05-12 Ove Edfors - ETI 051 1 2010-05-12 Ove Edfors - ETI 051 2 Centralized and AdHoc Infrastructure and AdHoc Networks Networks • Some issues to consider: – Centralized networks Centralized Network AdHoc Network Centralized Network AdHoc Network • Integration with wired LAN • Network planning (access points) • Interoperability Wired network • Roaming and handover between access points • Security / authentication • Power management AP AP MS – AdHoc networks MS • Multi-hop and routing • Quality of service MS MS • Interoperability MS MS • Security / authentication MS • Power management 2010-05-12 Ove Edfors - ETI 051 3 2010-05-12 Ove Edfors - ETI 051 4
Error-correcting and Error- detecting Codes • In wireless systems we need error-correcting and error-detecting codes • The quality of the wireless channel changes with time and we need to safeguard our data. Error control and ARQ – Data transmitted during a fading dip can (if the coding scheme is properly designed) be recovered by an error- correcting code. • To reach very low error rates we need error detection to trap incorrectly decoded data. 2010-05-12 Ove Edfors - ETI 051 5 2010-05-12 Ove Edfors - ETI 051 6 Automatic Repeat Request (ARQ) • Using error-detection codes we can reduce the error rate by applying an ARQ scheme. • ARQ is usually not an option for time critical data over ‘slow’ channels, such as real-time audio and Digital transmission video. in WLANs • For high efficiency, ARQ schemes for wireless channels need to be more intricate than the ones used on wired channels – This is due to the fading nature of wireless channels 2010-05-12 Ove Edfors - ETI 051 7 2010-05-12 Ove Edfors - ETI 051 8
Some recent WLANs Data rate [kbit/sec] (IEEE 802.11n) +MIMO 100,000 Increasing OFDM IEEE 802.11a equalization IEEE 802.11g Hiperlan/2 complexity IEEE 802.11b 10,000 Spread Spectrum Bluetooth 2.0 Wireless LAN standards and specifications IEEE 802.11 Recent WLAN standards and 1,000 Bluetooth 1.0 Recent WLAN standards and specifications specifications The latest standards, with the highest The latest standards, with the highest data rates are based on OFDM data rates are based on OFDM 100 (in combination with MIMO). (in combination with MIMO). 10 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year 2010-05-12 Ove Edfors - ETI 051 9 2010-05-12 Ove Edfors - ETI 051 10 Wireless LAN Standards and ETSI - HIPERLAN/2 Specifications • Some of the available standards and specifications – ETSI www.etsi.fr • HIPERLAN/2 HIPERLINK – IEEE HIPERACCESS • 802.11 • 802.11a • 802.11b • 802.11g • 802.11n Part of the ETSI – BlueTooth SIG Part of the ETSI BRAN family BRAN family • BlueTooth HIPERLAN 2010-05-12 Ove Edfors - ETI 051 11 2010-05-12 Ove Edfors - ETI 051 12
ETSI - HIPERLAN/2 ETSI - HIPERLAN/2 • Digital transmission – OFDM (multicarrier) with sampling rate 20 MHz BURST STRUCTURES BURST STRUCTURES – 5.150-5.350 GHz & 5.470-5.725 GHz . . . – 48 data carriers + 4 pilot carriers Broadcast Preamble Data Data Data – Carrier spacing 0.3125 MHz 16 us 4 us – Symbol length 4 us (0.8 us cyclic prefix) . . . Down link Preamble Data Data Data – Range < 150 m. – TDMA/TDD 8 us • Syncronization . . . Up link (short preamble) Preamble Data Data Data – Broadcast (base => all). Preamble 16 us. 12 us – Downlink (base => terminal). Preamble 8 us. . . . – Uplink (teminal => base). Short preamble 12 us and long Up link (long preamble) Preamble Data Data Data preamble 16 us. 16 us 2010-05-12 Ove Edfors - ETI 051 13 2010-05-12 Ove Edfors - ETI 051 14 ETSI - HIPERLAN/2 ETSI - HIPERLAN/2 SIGNAL CONSTELLATIONS TRANSMISSION MODES SIGNAL CONSTELLATIONS TRANSMISSION MODES (OPTION) Sig.constCode Databit/symbol Data rate BPSK QPSK 16-QAM 64-QAM BPSK 1/2 24 6 Mbit/s BPSK 3/4 36 9 Mbit/s QPSK 1/2 48 12 Mbit/s QPSK 3/4 72 18 Mbit/s 16QAM 9/16 108 27 Mbit/s 16QAM 3/4 144 36 Mbit/s 64QAM 3/4 216 54 Mbit/s 1 bit/symbol 2 bit/symbol 4 bit/symbol 6 bit/symbol 2010-05-12 Ove Edfors - ETI 051 15 2010-05-12 Ove Edfors - ETI 051 16
IEEE - 802.11 IEEE - 802.11 • 802.11-1997 • 802.11a-1999 (supplement to 802.11-1997) – PHY layer – New PHY (and MAC) layer for 802.11 www.ieee.org • diffused infrared - in baseband – 5 GHz band • DSSS and FHSS (50 hops/sec) in 2.4 GHz ISM band – Essentially the same physical layer (OFDM) as HIPERLAN/2 • 1 and 2 Mbps data rate – 6-54 Mbps data rate – MAC layer • Two network architectures: Infrastructure Network and Ad-Hoc • 802.11b-1999 (supplement to 802.11-1997) Network • Primary services: Data transfer, Association, Reassociation, – New PHY (and MAC) layer for 802.11 Authentication, Privacy, and Power Management – 2.4 GHz band – MISSING – DSSS based physical layer • AP-to-AP coordination for roaming, Data frame mapping, – 11 Mbps data rate Confomance test 2010-05-12 Ove Edfors - ETI 051 17 2010-05-12 Ove Edfors - ETI 051 18 IEEE - 802.11 IEEE 802.11 – a bigger family • 802.11g-2003 (supplement to 802.11-1997) • IEEE 802.11 - The original 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard • IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001) – Same PHY layer as 802.11a • IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999) • IEEE 802.11d - international (country-to-country) roaming extensionsNew countries – 2.4 GHz band • IEEE 802.11e - Enhancements: QoS, including packet bursting • IEEE 802.11F - Inter-Access Point Protocol (IAPP) – New MAC layer • IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003) – 6-54 Mbps data rate • IEEE 802.11h - 5 GHz spectrum, Dynamic Channel/Frequency Selection (DCS/DFS) and Transmit Power Control (TPC) for European compatibility • IEEE 802.11i (ratified 24 June 2004) - Enhanced security • IEEE 802.11j - Extensions for Japan • 802.11n (under development) • IEEE 802.11k - Radio resource measurements • IEEE 802.11n - Higher throughput improvements • IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as – Up to 500 Mbit/sec ambulances and passenger cars) – Proposal based on MIMO technology • IEEE 802.11r - Fast roaming • IEEE 802.11s - Wireless mesh networking • IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics • IEEE 802.11u - Interworking with non-802 networks (e.g., cellular) • IEEE 802.11v - Wireless network management 2010-05-12 Ove Edfors - ETI 051 19 2010-05-12 Ove Edfors - ETI 051 20
Bluetooth Special Interest Bluetooth Special Interest Group - Bluetooth Group - Bluetooth • FHSS in the 2.4 GHz band PICONET www.bluetooth.com – max 1600 hops/sec (much faster than IEEE 802.11 FHSS) – 1 MHz channels – 79 frequency channels • Modulation Slave 2 – Version 1.x • GFSK (BT=0.5) • 1 Mbps (raw) Master – Version 2.x Slave 3 • Additionally differential 4PSK and 8PSK • 2 & 3 Mbps Slave 1 • Range – 10 cm -- 10 m 2010-05-12 Ove Edfors - ETI 051 21 2010-05-12 Ove Edfors - ETI 051 22 Bluetooth Special Interest Bluetooth Special Interest Group - Bluetooth Group - Bluetooth SCATTERNET MASTER SLAVE same clock Slave Mater internal internal Hop Hop clock clock Frequency Frequency freq. freq. hop hop (hop sequence generator generator timing) Offset Master Master Master unit Master unit BlueTooth Device BlueTooth Device Address Address (selection of hop sequence) 2010-05-12 Ove Edfors - ETI 051 23 2010-05-12 Ove Edfors - ETI 051 24
Bluetooth Special Interest Bluetooth Special Interest Group - Bluetooth Group - Bluetooth Packet lengths 1, 3 and 5 Packet lengths 1, 3 and 5 FH / TDD FH / TDD 625 us f ( k ) f ( k +1) f ( k +2) f ( k +3) f ( k +4) f ( k +5) Frequency: f (2 k ) f (2 k +1) f (2 k +2) f (2 k +3) t MASTER f ( k ) f ( k +3) f ( k +4) f ( k +5) t t SLAVE f ( k ) f ( k +5) t 625 us t 2010-05-12 Ove Edfors - ETI 051 25 2010-05-12 Ove Edfors - ETI 051 26 Bluetooth Special Interest Bluetooth Special Interest Group - Bluetooth Group - Bluetooth Modulation • Synchronous connection oriented (SCO) Gaussian-filtered Frequency Shift Keying (GFSK) [c.f. GMSK] BT b = 0.5 B = 500 kHz – Synchronous transmission Mod.index = 0.32 (+/-3%) f d = 320/2 kHz = 160 kHz (+/-3%) Bitrate 1 Mbit/sec (+/-1ppm) – Symmetric data rate – Reserved time slots f – Intended for voice 1 1 F T + f d – No retransmission • Asymmetric connection less (ACL) Transmit – Asynchronous transmission center F T frequency t – Used for asymmetric communication – Retransmission used (Go-back-1 ARQ) F T - f d 0 0 T b = 1 us These are the basic packet types. 2010-05-12 Ove Edfors - ETI 051 27 2010-05-12 Ove Edfors - ETI 051 28
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