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Aktuelle Entwicklungen in der Standardisierung für drahtlose lokale Netzwerke

Aktuelle Entwicklungen in der Standardisierung für drahtlose lokale Netzwerke. Maximilian Riegel Siemens AG, ICM Networks 2002-10-02. Outline. WLAN Standardization overview The IEEE802.11 WLAN Standard Architecture Physical layer Spectrum issues MAC layer functions Configurations

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Aktuelle Entwicklungen in der Standardisierung für drahtlose lokale Netzwerke

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  1. Aktuelle Entwicklungen in der Standardisierung für drahtlose lokale Netzwerke Maximilian Riegel Siemens AG, ICM Networks2002-10-02

  2. Outline • WLAN Standardization overview • The IEEE802.11 WLAN Standard • Architecture • Physical layer • Spectrum issues • MAC layer functions • Configurations • Handover • Power Management • Privacy and access control • WLAN Security • WLAN – UMTS Interworking • Tight coupling • Market and application considerations • Loose coupling • Standardization activities M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  3. Wireless LAN Standardization ETSI BRAN UMTS Integration HiperLAN/2 DFS & TPC 5 GHz 54 Mbit/s WIG Wireless Interworking Group IEEE 802.11 802.11f: Inter Access Point Protocol 802.11e: QoS Enhancements MAC 802.11i: Security Enhancements IEEE 802.11 802.11h DFS & TPC 802.11a 5 GHz 54Mbit/s 802.11g 2,4 GHz 54Mbit/s 802.11b 2,4 GHz 11Mbit/s PHY 2,4 GHz 2 Mbit/s Current standardization topics M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  4. The ubiquitous WLAN Railway Station Airport PublicWLAN Campus • Today’s road worriers require access to the Internet everywhere. • WLAN is more than just cable replacement, it provides hassle-free broadband Internet access everywhere. • Coverage in ‘hot-spots’ sufficient. • IEEE802.11b meets the expectations for easiness, cost and bandwidth. Office Hospital Office Congress hall,Hotel Semi-publicWLAN Corporate WLAN Plant Remote Access HomeWLAN M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  5. Wireless IEEE802.11 Standard • Approved June 1997 • 802.11b approved Sept. 1999 • Operation in the 2.4GHz ISM band • USA: FCC part 15.247-15.249 • Europe: ETS 300-328 • Japan: RCR-STD-33A • Supports three PHY layer types: DSSS, FHSS, Infrared • MAC layer common to all 3 PHY layers • Supports peer-to-peer and infrastructure configurations • IEEE802.11b high data rate extension with 11 Mbps using existing MAC layer • IEEE802.11a for operation in the 5 GHz band with up to 54 Mbit/s using the same MAC layer M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  6. Wireless LAN IEEE802.11Basic Architecture local distribution network internet Netscape apache http http tcp tcp ip ip ip ip ip 802.2 ppp 802.2 802.2 802.2 802.2 ppp 802.11 Bluetooth 802.11 802.3 802.3 802.3 Bluetooth 802.3 IEEE802.11 Client Access Point Access Router Server M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  7. IEEE802.11 Protocol Architecture • Station Management • interacts with both MAC Management and PHY Management • MAC Layer Management Entity • power management • handover • MAC MIB • MAC Entity • basic access mechanism • fragmentation • encryption • PHY Layer Management • channel tuning • PHY MIB • Physical Layer Convergence Protocol (PLCP) • PHY-specific, supports common PHY SAP • provides Clear Channel Assessment signal (carrier sense) • Physical Medium Dependent Sublayer (PMD) • modulation and encoding LLC = 802.2 MAC Layer Management MAC Sublayer MAC PHY Layer Management PLCP Sublayer Station Management PHY PMD Sublayer M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  8. IEEE 802.112.4 GHz & 5 GHz Physical Layers • 2.4 GHz Frequency Hopping Spread Spectrum • 2/4 FSK with 1/2 Mbps • 79 non overlapping frequencies of 1 MHz width (US) • 2.4 GHz Direct Sequence Spread Spectrum • DBPSK/DQPSK with 1/2 Mbps • Spreading with 11 Bit barker Code • 11/13 channels in the 2.4 GHz band • 2.4 GHz High Rate DSSS Ext. (802.11b) • CCK/DQPSK with 5.5/11 Mbps Power Power spreading Frequency Frequency Frequency • 5 GHz OFDM PHY (802.11a) • Basic parameters identical toHiperLAN2 PHY • European regulatory issues unsolved Power Frequency Time • Baseband IR, 1 and 2Mbps, 16-PPM and 4-PPM M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  9. IEEE802.11g: Further Speed Extension for the 2.4GHz Band Upcoming • Mandatory: CCK w/ short preample (802.11b) and OFDM (802.11a applied to 2.4 GHz range). • Optional: PBCC proposal for 22 Mbit/s from Texas Instruments • Optional: CCK-OFDM proposal for up to 54 Mbit/s from Intersil Range vs. throughput rate comparison of • CCK (802.11b), • OFDM(“802.11a”), • PBCC, • CCK-OFDM (Batra, Shoemake; Texas Instruments; Doc: 11-01-286r2) M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  10. Spectrum Designation in the 5 GHz range 5.150 5.250 Japan 5.150 5.350 5.725 5.825 Max peak Tx power USA Indoor 200 mW / Outdoor 1 W EIRP Outdoor 4 W EIRP DFS & TPC DFS & TPC 5.350 5.150 5.470 5.725 Max mean Tx power Europe Indoor 200 mW EIRP Outdoor 1W EIRP 5.100 5.300 5.400 5.500 5.600 5.700 5.800 5.900 5.200 DFS: Dynamic Frequency Selection TPC: Transmit Power Control • Many European countries are currently opening 5 GHz range for radio LANs. Freq./GHz M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  11. IEEE802.11h: Spectrum and Transmit Power Management AP 2 AP 1 • DFS (Dynamic Frequency Selection) • AP‘s make the decision • STA‘s provide detailed reportsabout spectrum usage at theirlocations. AP 3 STA Upcoming • TPC (Transmission power control) • supports interference minimisation, power consumption reduction, range control and link robustness. • TPC procedures include: • AP‘s define and communicate regulatory and local transmit power constraints • Stations select transmit powers for each frame according to local and regulatory constraints M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  12. … when will 5 GHz WLANs come? • IEEE802.11b (2.4 GHz) is now taking over the market. • There are developments to enhance IEEE802.11b for • more bandwidth (up to 54 Mbit/s) • QoS (despite many applications do not need QoS at all) • network issues (access control and handover). • 5 GHz systems will be used when the 2.4 GHz ISM band will become too overcrowded to provide sufficient service. • TCP/IP based applications are usually very resilient against ‘error proune’ networks. • Issues of 5 GHz systems: • Cost: 5 GHz is more expensive than 2.4 GHz • Power: 7dB more transmission power for same distance • Compatibility to IEEE802.11b/g necessary M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  13. CSMA/CA Explained Busy Medium • Reduce collision probability where mostly needed. • Stations are waiting for medium to become free. • Select Random Backoff after a Defer, resolving contention to avoid collisions. • Efficient Backoff algorithm stable at high loads. • Exponential Backoff window increases for retransmissions. • Backoff timer elapses only when medium is idle. • Implement different fixed priority levels IFS: Inter Frame Space Free access when medium DIFS is free longer than DIFS Contention Window PIFS DIFS SIFS Backoff-Window Next Frame Slot time Select Slot and Decrement Backoff as long as medium is idle. Defer Access M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  14. IEEE802.11e: MAC Enhancementsfor Quality of Service (EDCF) Upcoming • differentiated DCF access to the wireless medium for prioritized traffic categories (4 different traffic categories) • output queue competes for TxOPs using EDCF wherein • the minimum specified idle duration time is a distinct value • the contention window is a variable window • lower priority queues defer to higher priority queues • EDCF (Enhanced Distributed Coordination Function) M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  15. IEEE802.11Point Coordination Function (PCF) • Optional PCF mode provides alternating contention free and contention operation under the control of the access point • The access point polls stations for data during contention free period • Network Allocation Vector (NAV) defers the contention traffic until reset by the last PCF transfer • PCF and DCF networks will defer to each other • PCF improves the quality of service for time bounded data CFP repetition interval Contention Period Contention Free Period Access Point Beacon D1+Poll D2+Poll CF end U1+ACK U2+ACK Stations M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  16. IEEE802.11e: MAC Enhancements for Quality of Service (HCF) Upcoming • only usable in infrastructure QoS network configurations • allow a uniform set of frame exchange sequences to be used during both the contention period (CP) and contention free period (CFP) • uses a QoS-aware point coordinator, called a hybrid coordinator • by default collocated with the enhanced access point (EAP) • uses the point coordinator's higher priority to allocate transmission opportunities (TxOPs) to stations • provides limited-duration contention free bursts (CFBs) to transfer QoS data. • meets predefined service rate, delay and/or jitter requirements of particular traffic flows. • ... • „Quite complex method still under definition“ • HCF (Hybrid coordination function) M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  17. IEEE802.11 Ad Hoc Mode • Independent networking • Use Distributed Coordination Function (DCF) • Forms a Basic Service Set (BSS) • Direct communication between stations • Coverage area limited by the range of individual stations Peer-to-Peer Network M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  18. IEEE802.11 Infrastructure Mode • Access Points (AP) and stations (STA) • BSS (Basic Service Set): a set of stations controlled by a single coordination function • Distribution system interconnects multiple cells via access points to form a single network • Extends wireless coverage area and enables roaming Distribution System (DS) Server BSS-A BSS-B M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  19. IEEE802.11 Handover Access Point B Station 6 Station 2 Station 5 Access Point A Access Point C Station 4 Station 7 Station 3 Station 1 • Station decides that link to its current AP is poor • Station uses scanning function to find another AP • or uses information from previous scans • Station sends Reassociation Request to new AP • If Reassociation Response is successful • then station has roamed to the new AP • else station scans for another AP • If AP accepts Reassociation Request • AP indicates Reassociation to the Distribution System • Distribution System information is updated • normally old AP is notified through Distribution System M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  20. IEEE802.11f: Inter-Access Point Protocol (IAPP) Upcoming • IAPP defines procedures for • automatic configuration handling of access points • context transfer between APs when stations move RADIUS Server Distribution System Server IAPP-ADD IAPP-MOVE M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  21. IEEE802.11 Power Management • Stations wake up prior to an expected DTIM (Delivery Traffic Indication Message). • If TIM indicates frame buffered • station sends PS-Poll and stays awake to receive data • else station sleeps again • Broadcast frames are also buffered in AP. • all broadcasts/multicasts are buffered • broadcasts/multicasts are only sent after DTIM. • DTIM interval is a multiple of TIM interval TIM-Interval DTIM interval Time-axis Busy Medium TIM TIM DTIM TIM TIM DTIM Broadcast AP activity Broadcast PS Station Tx operation PS-Poll M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  22. IEEE802.11 Privacy and Access Control • Goal of 802.11 is to provide “Wired Equivalent Privacy” (WEP) • Usable worldwide • 802.11 provides for an authentication mechanism • To aid in access control. • Has provisions for “OPEN”, “Shared Key” or proprietary authentication extensions. • Shared key authentication is based on WEP privacy mechanism • Limited for station-to-station traffic, so not “end to end”. • Uses RC4 algorithm based on: • a 40 bit secret key • and a 24 bit IV that is send with the data. • includes an ICV to allow integrity check. M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  23. Shortcomings of plain WEP security • WEP unsecure at any key length • IV space too small, lack of IV replay protection • known plaintext attacks • No user authentication • Only NICs are authenticated • No mutual authentication • Only station is authenticated against access point • Missing key management protocol • No standardized way to change keys on the fly • Difficult to manage per-user keys for larger groups • WEP is no mean to provide security for WLAN access, • … but might be sufficient for casual cases. M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  24. IEEE802.11i: Enhanced security Associate AuthenticationServer EAP Identity Request EAP Identity Response Access Request EAP Request Access Challenge EAP Response Access Request EAP Success Access Accept Upcoming • Enhanced encryption • WEP2 w/ increase IV space to 128bit, key length 128bit • optional: Advanced Encryption Standard (AES) • Authentication and key management by adoption of IEEE802.1X Standard for Port Based Network Access Control M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  25. A last word about WLAN security: Even IEEE802.11i may not be sufficient for public hot-spots: Only VPN technologies (IPSEC, TLS, SSL) will fulfil end-to-end security requirements in public environments. VPN technologies might even be used in corporate WLAN networks. IPSEC, TLS, SSL tcp tcp 802.11 802.11 WEP 802.11 802.11 Netscape apache http http tcp tcp ip ip ip ip ip 802.2 ppp 802.2 802.2 802.2 802.2 ppp 802.3 802.3 802.3 802.3 Bluetooth M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  26. WLAN – UMTS Interworking: Ancient approach: ‘tight coupling’ LNP SCP IN MSCS MSCS VLR HSS PSTN AUC BSC RNC BTS BTS wlan local access network Node B Node B TDM / ATM / IP PLMN core GGSN SGSN PLMN access internet WLAN as just another radio access technology of UMTS • All UMTS services become available over WLAN. but: • PLMN is burdened with high bandwidth WLAN traffic. • Wi-Fi does not provide all the functionality needed (QoS, security). M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  27. UMTS and Wireless LAN are different. GSM/GPRS/UMTS anytime / everywhere voice, realtime messaging QoS precious bandwidth carrier grade operator driven huge customer base high revenues WLAN IEEE802.11 sometimes / somewhere standard web applications best effort cheap bandwidth corporate technology market driven casual users low revenues M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  28. WLAN is much cheaper than 2G/3G * based on current IP volume prices of 40€ /GByte.Time based pricing results in similar costs,e.g. MobileStar Pulsar pricing plan: $0,10/min Transfer cost/duration of an 1 Mbytes .ppt/.doc/.xls File... logarithmic scale € 4 min 4 min 5 sec -99,6% M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  29. Becoming a WLAN operator is easy. • Legal aspects: • Usage of license free spectrum (2,4 GHz ISM band) • No telecommunication license necessary, as long as • not providing telephony services, • not providing network access across borders of private premises. • Cost issues: • The lower bound:Investment: WLAN Access Point /w DSL Router (~ 350 €)Monthly operation cost: ~ 60 € for DSL Flat Rate • Most commercial installations are much more expensive due to charging and billing. • It is very easy and extremely cheap to become a WLAN operator, but most people did not yet know about it. ...but wait until they have installed WLAN in their living rooms! M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  30. WLAN – UMTS Interworking: Now widely accepted: ‘loose coupling’ LNP SCP IN MSCS MSCS VLR HSS PSTN AUC internet BSC RNC BTS BTS wlan local access network Node B Node B Siemens contributed ‚loose coupling‘ to standardization. TDM / ATM / IP PLMN core Authentication Accounting SGSN PLMN access Only Authentication, Authorization and Accounting of WLAN access is performed by the mobile network operator. • Revenues without competing against aggressive WLAN operators. • Perfect model for leveraging the huge customer base and establishing a widely accepted platform for mobile commerce. M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  31. E.g.: Web based authentication and mobile network security SMS containing Password Username: Password: html N auth RADIUS client auth HLR Mobile Client 0172-3456789 ********** mobile network DHCP Server AAA Server Access Gateway internet M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  32. Standards for WLAN/UMTS interworking • 3GPP • R5: SA1Requirements of 3GPP system – WLAN interworking. • R6: SA2Continuation with architectural considerations • ETSI BRANSubgroup on “Interworking between HiperLAN/2 and 3rd generation cellular and other public systems”. • Detailed architectural description mainly based on the Siemens ‘loose coupling’ principle established • IEEE802.11 and MMAC are now joining this effort.=> Wireless Interworking Group (WIG). • WECA (Wireless Ethernet Compatibility Alliance)‘Wireless ISP Roaming Initiative’ • Detailed functional specification for roaming (loose coupling) between IEEE802.11 WLAN networks available. • Mainly aimed for roaming between ISPs but also well applicable for MNOs. M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  33. The end • Thank you for your attention. • Questions and comments? • Maximilian Riegelmaximilian.riegel@icn.siemens.dehttp://www.max.franken.de/ M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  34. WLAN – UMTS interworking is laying the path for the future of networking… New radio interface • From the ITU-R vision of Wireless Communications beyond 3G: Services and applications Media access system download channel Wireline xDSL Digital Broadcast IP based core network WLAN type cellular 2nd. gen. return channel: e.g. cellular IMT-2000 (UMTS) Seamless network of complementary access systems M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

  35. Generic Internet Network Architecture Internet Policy Server AAA Server WLAN Access Peer (Client) Peer (Web-Server) Internet/Web Applications www www http http tcp tcp ip ip ip ip ip ip ip ip 802.2 802.2 802.2 802.2 link link link link link link 802.11 802.11 802.3 802.3 phy phy phy phy phy phy M. Riegel, WLAN Standardization, 021002-wlan-informatik2002.ppt

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