Electronic Engineering Mobile and Wireless Networking Lecture 16
Electronic Engineering Mobile and Wireless Networking Lecture 16 Dr. Xinbing Wang 1
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 – Wi. Fi 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 – Wi. MAX or IEEE 802. 16 (Broadband Access) Electronic Engineering Dr. Xinbing Wang 2
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. Electronic Engineering Dr. Xinbing Wang 3
Method 3: DFWMAC-PCF (2) t 0 t 1 medium busy point coordinator wireless stations‘ NAV PIFS Super. Frame SIFS D 1 SIFS D 2 SIFS U 1 U 2 NAV At time t 0 the contention-free period should start, but another station is transmitting data l After the medium has been idle, the PCF has to wait for PIFS before accessing the medium. l The point coordinator now sends data D 1 to the first station. The station can answer after SIFS. After waiting for SIFS, the point coordinator can poll the second station by sending D 2 (downstream). l The second station replies with U 2 (upstream) l Electronic Engineering Dr. Xinbing Wang 4
Method 3: DFWMAC-PCF (3) t 2 point coordinator wireless stations‘ NAV D 3 PIFS SIFS D 4 t 3 t 4 CFend SIFS U 4 NAV contention free period contention t 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 Electronic Engineering Dr. Xinbing Wang 5
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 Frame Duration/ Address Sequence Address Control ID 1 2 3 Control 4 bits 2 2 4 1 1 1 1 0 -2312 4 Data CRC 1 Protocol To From More Power More Type Subtype Retry WEP Order version DS DS Frag Mgmt Data Electronic Engineering Dr. Xinbing Wang 6
Special Frames: ACK, RTS, CTS Acknowledgement bytes ACK Request To Send RTS bytes 2 2 6 6 Frame Receiver Transmitter Duration Control Address bytes Clear To Send CTS Electronic Engineering 2 Frame 2 6 Receiver 4 Duration CRC Control Address 2 2 6 Frame Receiver Duration Control Address 4 CRC Dr. Xinbing Wang 7
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 informs the old AP so it can release resources Electronic Engineering Dr. Xinbing Wang 8
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 – Wi. Fi 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 – Wi. MAX or IEEE 802. 16 (Broadband Access) Wireless local loop (WLL) and Fixed Wireless Access (FWA) 802. 16 service Wi. MAX Electronic Engineering Dr. Xinbing Wang 9
Wireless Local Loop (WLL) Wired technologies responding to need for reliable, high-speed access by residential, business, and government subscribers – ISDN, x. DSL, 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 Electronic Engineering Dr. Xinbing Wang 10
WLL Configuration Electronic Engineering Dr. Xinbing Wang 11
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 Electronic Engineering Dr. Xinbing Wang 12
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 Electronic Engineering Dr. Xinbing Wang 13
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 Electronic Engineering Dr. Xinbing Wang 14
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 (Qo. S) Use wireless links with microwave or millimeter wave radios Are capable of broadband transmissions (>2 Mbps) Electronic Engineering Dr. Xinbing Wang 15
IEEE 802. 16 Protocol Architecture Electronic Engineering Dr. Xinbing Wang 16
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 Electronic Engineering Dr. Xinbing Wang 17
Protocol Architecture: 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 Qo. S parameters into native 802. 16 MAC format – Adapt time dependencies of upper layer traffic into equivalent MAC service Electronic Engineering Dr. Xinbing Wang 18
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 Electronic Engineering Dr. Xinbing Wang 19
Wi. MAX Forum The Wi. MAX mission is to make the 802. 16 interoperable. Just like Wi. Fi did for 802. 11. No Wi. MAX compliant products today, foreseen during 2005. The first Wi. MAX products will be based on 802. 16 d. Intel is the most powerful player in Wi. MAX forum Architecture specification work initiated in a new subgroup 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 Electronic Engineering Dr. Xinbing Wang 20
Wi. MAX Standards Roadmaps ra ble e rop (< ) to e bs su is h t f Hz G 6 802. 16 e e AX M Wi 802. 16 nt =i 802. 16 d Some Mobility 2005 ? Similar to. 16 a 802. 16 a Errata Jul 2004 2 – 11 GHz NLOS Jan 2003 10 – 66 GHz LOS Sep 2000 Electronic Engineering NOTE: IEEE 802. 16 specifies only layer 1 & 2 21 Dr. Xinbing Wang
Applications of 802. 16 Electronic Engineering Dr. Xinbing Wang 22
Wi. MAX 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 Electronic Engineering Dr. Xinbing Wang 23
IEEE 802. 16 Standards Wi. MAX 802. 16 d/Hiper. MA N 802. 16 e Completed Spectrum December 2001 June 2004 (802. 16 d) Estimate 2005 10 - 66 GHz < 11 GHz < 6 GHz Channel Conditions Bit Rate Line of Sight Only Non Line of Sight 32 – 134 Mbps in 28 MHz channel bandwidth Up to 75 Mbps in 20 MHz Up to 15 Mbps in channel bandwidth 5 MHz channel bandwidth Modulation QPSK, 16 QAM and 64 QAM OFDM 256 FFT Scalable OFDMA QPSK, 16 QAM, 64 QAM 128 to 2048 FFT Mobility Fixed Electronic Engineering 20, 25 and 28 MHz Channel Portable 1. 75 to 20 MHz Dr. Xinbing 1. 75 to 20 MHz Wang 24
Relation to Other Technologies Whether 802. 16 a will complement or clash with certain other technologies remains to be seen. For a while, at least, it will certainly be complementary to 802. 11 a, enabling Wi-Fi users to dramatically extend their distance from wired networks. Electronic Engineering Dr. Xinbing Wang 25
Theoretical Wi. MAX Raw Bandwidth (Mbit/s)* Modulation / Code rate QPSK 1/2 QPSK 3/4 1, 75 MHz 1. 45 2. 18 3, 5 MHz 2. 91 4. 36 7, 0 MHz 5. 82 14, 0 MHz 20, 0 MHz 16 QAM 1/2 16 QAM 3/4 64 QAM 2/3 64 QAM 3/4 4. 36 5. 82 6. 55 5. 82 8. 73 11. 64 13. 09 8. 73 11. 64 17. 45 23. 27 26. 18 11. 64 17. 45 23. 27 34. 91 46. 55 52. 36 16. 26 24. 40 32. 53 48. 79 65. 05 73. 19 2. 91 *OFDM 256 FFT. Includes MAC and preamble overhead Electronic Engineering Dr. Xinbing Wang 26
Theoretical Coverage (Km)* Type of Area Rural Rooftop Antenna Window/Fixed Antenna Indoor/Portable Antenna <20 Km using <8 Km NLOS** <4 Km Suburban N/A <4 Km <2 Km Urban N/A <2 Km <1 Km *Approximate distances only, depends heavily on geographical area **<50 Km is theoretical maximum for LOS. Assumption is a NLOS base station and a rooftop antenna for better reception and maximum uplink power Electronic Engineering Dr. Xinbing Wang 27
Portability (Mobility) in 802. 16 e 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). Electronic Engineering Dr. Xinbing Wang 28
Mobility in 802. 16 e – 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 Qo. S supported. All four GSM/WCDMA classes. Electronic Engineering Dr. Xinbing Wang 29
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. 11 a: 64 FTTs – 802. 16 d: 256 FFTs Spectrum – 802. 11: limited channels in Un-license spectrum – 802. 16: multiple channels in licensed & Un-license spectrum Electronic Engineering Dr. Xinbing Wang 30
Comparison 802. 11 and 802. 16 Technology 802. 11 802. 16 Range < 300 feet < 30 Mile ( typical 3~4) Coverage Optimized for indoor short range 2. 7 bps/Hz peak. <= 54 Mbps in 20 MHz Outdoor LOS & NLOS Scalability 1 -10 CPE CSMA/CA 1 - hundreds CPE TDMA QOS No QOS On demand BW voice Video, data Data rate 5 bps/Hz peak, <100 Mbps in 20 MHz CPE: Customer Premise Chips Electronic Engineering Dr. Xinbing Wang 31
Broadband Wireless Systems Wi. MAX 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 Electronic Engineering 3 G Evolved Mobile Broadband Phone & laptop Full mobility Non line-of-sight 3 GPP and 3 GPP 2 standard Voice/data optimized Optimized for Mobility Evolution towards Higher Data Drivers: Mobile Broadband for incremental investment National & global roaming networks Dr. Xinbing Wang 32
Peak Bit Rates Comparison CDMA 2000 1 x 1 x. EV-DO 1. 25 MHz 1 x. EV-DV IEEE 802. 16 d -20 MHz Flarion 1. 25 MHz Electronic Engineering Standards compliant 5 Mhz HSDPA Peak Bit-rate UL WCDMA Peak bit-rate DL 200 KHz EDGE FDD/TDD Channel Bandwidth GSM/GPRS FDD 160 kbps 3 GPP FDD 480 kbps 3 GPP FDD/TDD 2 Mbps 3 GPP FDD 14. 4 Mbps 7. 68 Mbps 3 GPP FDD 640 kbps 450 kbps 3 GPP 2 FDD 3. 1 Mbps 1. 8 Mbps 3 GPP 2 - 75 Mbps IEEE FDD/TDD FDD 3. 2 Mbps 900 kbps Dr. Xinbing Wang _ 33
Summary Cellular network architecture: UMTS (Chapter 10) Mobile IP (Chapter 12) Wireless LAN (Chapters 11/13/14) – Classification: Wireless LANs, PANs, and MANs – Wi. Fi 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 – Wi. MAX or IEEE 802. 16 (Broadband Access) Wireless local loop (WLL) and Fixed Wireless Access (FWA) 802. 16 services Wi. MAX Reading materials: http: //www. ieee 802. org/16/ Electronic Engineering Dr. Xinbing Wang 35
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