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Mobile and Wireless Networking

Mobile and Wireless Networking. Lecture 16 Dr. Xinbing Wang. Part 3: Current Wireless Systems. Cellular network architecture: UMTS (Chapter 10) Mobile IP (Chapter 12) Wireless LAN (Chapters 11 /13/14) Classification: Wireless LANs, PANs, and MANs WiFi or IEEE 802.11

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Mobile and Wireless Networking

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  1. Mobile and Wireless Networking Lecture 16Dr. Xinbing Wang

  2. Part 3: Current Wireless Systems • Cellular network architecture: UMTS (Chapter 10) • Mobile IP (Chapter 12) • Wireless LAN (Chapters 11/13/14) • Classification: Wireless LANs, PANs, and MANs • WiFi or IEEE 802.11 • Network architecture, fact sheets, pros and cons • Physical medium • Protocol architecture: PCF and DCF • 802.11 MAC: three methods, CSMA, DCF, and PCF • WiMAX or IEEE 802.16 (Broadband Access) Dr. Xinbing Wang

  3. Method 3: DFWMAC-PCF (1) • The access mechanisms presented so far cannot guarantee a maximum access delay or minimum transmission bandwidth. • To provide a time bounded service, the standards specify a Point Coordination Function (PCF) on top of the DCF mechanisms. • Using PCF requires an access point that can controls medium access and polls the single nodes. Ad Hoc networks cannot use this function. Dr. Xinbing Wang

  4. Method 3: DFWMAC-PCF (2) t0 t1 SuperFrame medium busy PIFS SIFS SIFS D1 D2 point coordinator SIFS SIFS U1 U2 wireless stations NAV stations‘ NAV • At time t0 the contention-free period should start, but another station is transmitting data • After the medium has been idle, the PCF has to wait for PIFS before accessing the medium. • The point coordinator now sends data D1 to the first station. The station can answer after SIFS. After waiting for SIFS, the point coordinator can poll the second station by sending D2 (downstream). • The second station replies with U2 (upstream) Dr. Xinbing Wang

  5. Method 3: DFWMAC-PCF (3) t2 t3 t4 PIFS SIFS D3 D4 CFend point coordinator SIFS U4 wireless stations stations‘ NAV NAV contention free period t contention period • Polling continues with the third node which has nothing to answer. • After waiting for PIFS, the point coordinator can issue an end marker (CFend), indicating that the contention period may start again. • The cycle starts again with the next superframe Dr. Xinbing Wang

  6. 802.11 - Frame format • Types • control frames, management frames, data frames • Sequence numbers • important against duplicated frames due to lost ACKs • Addresses • receiver, transmitter (physical), BSS identifier, sender (logical) • Miscellaneous • sending time, checksum, frame control, data bytes 2 2 6 6 6 2 6 0-2312 4 Frame Control Duration/ ID Address 1 Address 2 Address 3 Sequence Control Address 4 Data CRC bits 1 1 1 1 1 1 2 2 4 1 1 Protocol version Type Subtype To DS From DS More Frag Retry Power Mgmt More Data WEP Order Dr. Xinbing Wang

  7. Special Frames: ACK, RTS, CTS • Acknowledgement • Request To Send • Clear To Send bytes 2 2 6 4 Frame Control Duration Receiver Address CRC ACK bytes 2 2 6 6 4 Frame Control Duration Receiver Address Transmitter Address CRC RTS bytes 2 2 6 4 Frame Control Duration Receiver Address CRC CTS Dr. Xinbing Wang

  8. 802.11 - Roaming • Scanning • scan the environment, i.e., listen into the medium for beacon signals or send probes into the medium and wait for an answer • Reassociation Request • station sends a request to one or several AP(s) • Reassociation Response • success: AP has answered, station can now participate • failure: continue scanning • AP accepts Reassociation Request • signal the new station to the distribution system • the distribution system updates its data base (i.e., location information) • typically, the distribution system now informsthe old AP so it can release resources Dr. Xinbing Wang

  9. Part 3: Current Wireless Systems • Cellular network architecture: UMTS (Chapter 10) • Mobile IP (Chapter 12) • Wireless LAN (Chapters 11/13/14) • Classification: Wireless LANs, PANs, and MANs • WiFi or IEEE 802.11 • Network architecture, fact sheets, pros and cons • Physical medium • Protocol architecture: PCF and DCF • 802.11 MAC: three methods, CSMA, DCF, and PCF • WiMAX or IEEE 802.16 (Broadband Access) • Wireless local loop (WLL) and Fixed Wireless Access (FWA) • 802.16 service • WiMAX Dr. Xinbing Wang

  10. Wireless Local Loop (WLL) • Wired technologies responding to need for reliable, high-speed access by residential, business, and government subscribers • ISDN, xDSL, cable modems • Increasing interest shown in competing wireless technologies for subscriber access • Wireless local loop (WLL) • Narrowband – offers a replacement for existing telephony services • Broadband – provides high-speed two-way voice and data service Dr. Xinbing Wang

  11. WLL Configuration Dr. Xinbing Wang

  12. Advantages of WLL over Wired Approach • Cost – wireless systems are less expensive due to cost of cable installation that’s avoided • Installation time – WLL systems can be installed in a small fraction of the time required for a new wired system • Selective installation – radio units installed for subscribers who want service at a given time • With a wired system, cable is laid out in anticipation of serving every subscriber in a given area Dr. Xinbing Wang

  13. Propagation Considerations for WLL • Most high-speed WLL schemes use millimeter wave frequencies (10 GHz to about 300 GHz) • There are wide unused frequency bands available above 25 GHz • At these high frequencies, wide channel bandwidths can be used, providing high data rates • Small size transceivers and adaptive antenna arrays can be used Dr. Xinbing Wang

  14. Propagation Considerations for WLL • Millimeter wave systems have some undesirable propagation characteristics • Free space loss increases with the square of the frequency; losses are much higher in millimeter wave range • Above 10 GHz, attenuation effects due to rainfall and atmospheric or gaseous absorption are large • Multipath losses can be quite high Dr. Xinbing Wang

  15. 802.16 Standards Development • Use wireless links with microwave or millimeter wave radios • Use licensed spectrum • Are metropolitan in scale • Provide public network service to fee-paying customers • Use point-to-multipoint architecture with stationary rooftop or tower-mounted antennas • Provide efficient transport of heterogeneous traffic supporting quality of service (QoS) • Use wireless links with microwave or millimeter wave radios • Are capable of broadband transmissions (>2 Mbps) Dr. Xinbing Wang

  16. IEEE 802.16 Protocol Architecture Dr. Xinbing Wang

  17. Protocol Architecture: PHY and MAC • Physical and transmission layer functions: • Encoding/decoding of signals • Preamble generation/removal • Bit transmission/reception • Medium access control layer functions: • On transmission, assemble data into a frame with address and error detection fields • On reception, disassemble frame, and perform address recognition and error detection • Govern access to the wireless transmission medium Dr. Xinbing Wang

  18. Protocol Architecture: Convergence • Convergence layer functions: • Encapsulate PDU framing of upper layers into native 802.16 MAC/PHY frames • Map upper layer’s addresses into 802.16 addresses • Translate upper layer QoS parameters into native 802.16 MAC format • Adapt time dependencies of upper layer traffic into equivalent MAC service Dr. Xinbing Wang

  19. IEEE 802.16 Services • 802.16.1 • Digital audio/video multicast • Digital telephony • ATM • Internet protocol • Bridged LAN • Back-haul • Frame relay • 802.16.3 • Voice transport • Data transport • Bridged LAN Dr. Xinbing Wang

  20. WiMAX Forum • The WiMAX mission is to make the 802.16 interoperable. Just like WiFi did for 802.11. • No WiMAX compliant products today, foreseen during 2005. The first WiMAX products will be based on 802.16d. • Intel is the most powerful player in WiMAX forum • Architecture specification work initiated in a new sub-group • No single global spectrum assigned, possibilites: • 5.8 GHz, 3.5 GHz, 2.5 GHz, (IMT-2000 more likely in this band), and 2.3 GHz Dr. Xinbing Wang

  21. Similar to .16a Errata Jul 2004 802.16d WiMAX Standards Roadmaps WiMAX = interoperable subset of this (< 6 GHz) Some Mobility 2005 ? 802.16e 2 – 11 GHz NLOS Jan 2003 802.16a 802.16 10 – 66 GHz LOS Sep 2000 NOTE: IEEE 802.16 specifies only layer 1 & 2 Dr. Xinbing Wang

  22. Applications of 802.16 Dr. Xinbing Wang

  23. WiMAX Segments,High Level Pros and Cons • Backhaul, Fixed, point to point – LOS • High Bitrate • Low Interference • Clear Signal – No multipath fading • Relatively Low Cost • DSL, Fixed up to portable, Point to point, point to multipoint – NLOS • Relative high bitrate, but lower • One cell • Still relative cheap • Low to moderate interference-> Static radio environment • WAN and Mobile environment • Significantly lower bitrate • High interference. More multipath fading and dopplershift effects Dr. Xinbing Wang

  24. IEEE 802.16 Standards WiMAX Dr. Xinbing Wang

  25. Relation to Other Technologies • Whether 802.16a will complement or clash with certain other technologies remains to be seen. For a while, at least, it will certainly be complementary to 802.11a, enabling Wi-Fi users to dramatically extend their distance from wired networks. Dr. Xinbing Wang

  26. Modulation / Code rate QPSK 1/2 QPSK 3/4 16 QAM 1/2 16 QAM 3/4 64 QAM 2/3 64 QAM 3/4 1,75 MHz 1.45 2.18 4.36 5.82 6.55 2.91 3,5 MHz 5.82 8.73 13.09 4.36 2.91 11.64 7,0MHz 5.82 11.64 17.45 23.27 26.18 8.73 14,0 MHz 11.64 17.45 23.27 34.91 46.55 52.36 20,0 MHz 16.26 24.40 32.53 48.79 65.05 73.19 Theoretical WiMAX Raw Bandwidth (Mbit/s)* *OFDM 256 FFT. Includes MAC and preamble overhead Dr. Xinbing Wang

  27. Theoretical Coverage (Km)* Type of Area Rooftop Antenna Window/Fixed Antenna Indoor/Portable Antenna <20 Km using NLOS** Rural <8 Km <4 Km Suburban <4 Km <2 Km N/A Urban N/A <2 Km <1 Km *Approximate distances only, depends heavily on geographical area **<50 Km is the theoretical maximum for LOS. Assumption is a NLOS base station and a rooftop antenna for better reception and maximum uplink power Dr. Xinbing Wang

  28. Portability (Mobility) in 802.16e • New network reference model • New BS-BS interface (IB) and BS-server interface (A) defined, mobile subscriber station (MSS) • Authentication and service authorization (ASA) servers provide authorization, authentication, billing, management, provisioning and other services. EAP is defined for SIM cards, and other means of Authentication (Extensible Auth. Protocol). Dr. Xinbing Wang

  29. Mobility in 802.16e – Layer 2 • Handover (HO) process defined in MAC including • cell reselection • target BS scanning • network re-entry • HO decision and initiation and HO cancellation. • MAC messages for each of the handover functions defined. • Broadcast paging message defined. • Neighbor topology advertisement messages defined. • Option of using mobile IP provided. • Full QoS supported. All four GSM/WCDMA classes. Dr. Xinbing Wang

  30. Some Differences with 802.11 • MAC • 802.11: Contention-based MAC (CSMA/CA), basically wireless Ethernet. • 802.16: Dynamic TDMA-based MAC with on-demand bandwidth allocation. • OFDM • 802.11a: 64 FTTs • 802.16d: 256 FFTs • Spectrum • 802.11: limited channels in Un-license spectrum • 802.16: multiple channels in licensed & Un-license spectrum Dr. Xinbing Wang

  31. Comparison 802.11 and 802.16 Technology Range Coverage Data rate Scalability QOS 802.11 < 300 feet Optimized for indoor short range 2.7 bps/Hz peak. <= 54Mbps in 20MHz 1-10 CPE CSMA/CA No QOS 802.16 < 30 Mile ( typical 3~4) Outdoor LOS & NLOS 5bps/Hz peak, <100Mbps in 20 MHz 1- hundreds CPE TDMA On demand BW  voice Video, data CPE: Customer Premise Chips Dr. Xinbing Wang

  32. Broadband Wireless Systems WiMAX • Wireless Broadband • Laptop centric • Fixed  Portability • Line-of-Sight & Non Line-of-Sight • IEEE Layer 1 & 2 standard • Data optimized • Optimized for Fixed High data rate • Evolution towards mobility Drivers: • Data optimized network (simple) • DSL complement 3G Evolved • Mobile Broadband • Phone & laptop • Full mobility • Non line-of-sight • 3GPP and 3GPP2 standard • Voice/data optimized • Optimized for Mobility • Evolution towards Higher Data Drivers: • Mobile Broadband for incremental investment • National & global roamingnetworks Dr. Xinbing Wang

  33. Peak Bit Rates Comparison Channel Bandwidth FDD/TDD Peak bit-rate DL Peak Bit-rate UL Standards compliant GSM/GPRS 3GPP FDD 160 kbps 160 kbps 200KHz EDGE FDD 480 kbps 480 kbps 3GPP WCDMA FDD/TDD 2 Mbps 2 Mbps 3GPP 5Mhz HSDPA FDD 14.4 Mbps 7.68 Mbps 3GPP CDMA2000 1x FDD 640 kbps 450 kbps 3GPP2 1xEV-DO 1.25 MHz FDD 3.1 Mbps 1.8 Mbps 3GPP2 1xEV-DV FDD 3.1 Mbps 1.8 Mbps 3GPP2 IEEE 802.16d -20 MHz FDD/TDD - 75 Mbps - 75 Mbps IEEE _ Flarion FDD 1.25 MHz 3.2 Mbps 900 kbps Dr. Xinbing Wang

  34. Summary • Cellular network architecture: UMTS (Chapter 10) • Mobile IP (Chapter 12) • Wireless LAN (Chapters 11/13/14) • Classification: Wireless LANs, PANs, and MANs • WiFi or IEEE 802.11 • Network architecture, fact sheets, pros and cons • Physical medium • Protocol architecture: PCF and DCF • 802.11 MAC: three methods, CSMA, DCF, and PCF • WiMAX or IEEE 802.16 (Broadband Access) • Wireless local loop (WLL) and Fixed Wireless Access (FWA) • 802.16 services • WiMAX • Reading materials: http: //www.ieee802.org/16/ Dr. Xinbing Wang

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