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Wireless Metropolitan Area Networks: WiMAX and Mobile WiMAX

Wireless Metropolitan Area Networks: WiMAX and Mobile WiMAX. Outline. Wireless Metropolitan Area Networks IEEE 802.16 family of WMAN standards The WiMax Forum IEEE 802.16 MAC Layer IEEE 802.16 OFDM based Physical Layer Mobile WiMAX key features. Classification of Wireless Networks.

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Wireless Metropolitan Area Networks: WiMAX and Mobile WiMAX

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  1. Wireless Metropolitan Area Networks:WiMAX and Mobile WiMAX

  2. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  3. Classification of Wireless Networks • Wireless Wide Area Networks • national coverage • typ. basestation range 10km • typ. user data rate 1Mbps • Wireless Metropolitan Area Networks: broadband wireless access • city-wide coverage • typ. basestation range 1km • typ. user data rate 10Mbps • Wireless Local Area Networks • spot or building coverage • typ. access point range 100m • typ. user data rate 100Mbps • Wireless Personal Area Networks • max. range 10m • typ. user data rates 1Mbps - 1Gbps (!) • Wireless Body Area Networks • max. range 1m • typ. data rate per node: 100kbps (!) - 100Mbps WWAN WMAN WLAN WPAN WBAN 802.15 802.11 802.16 802.16e family of IEEE standards Communication Technology Laboratory Wireless Communication Group

  4. PMP SS P2P backhaul network BS mesh Broadband Wireless Access • fixed broadband wireless access • line of sight (LoS) • non line of sight (NLoS) • mobile broadband wireless access • different network configurations • point-to-point (P2P) • point-to-multipoint (PMP) • mesh • subscriber station (SS) • base station (BS) Communication Technology Laboratory Wireless Communication Group

  5. Typical Equipment • BS: base station (indoor electronics and WiMAX tower) • SS: subscriber station (a user or group of users sharing a WiMAX receiver) Source: [4] Communication Technology Laboratory Wireless Communication Group

  6. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  7. global standard for wireless metropolitan area networks (WMAN) several km range throughput comparable to ADSL fast installation (including temporary installations) scalability for evolutionary growth (small initial investment) wide range of QoS data rate, latency constant and variable rate traffic connection oriented P2P, PMP, mesh supports a wide range of carrier frequencies and bandwidth operation in licensed and unlicensed bands (interference) efficient handling of asymmetric traffic link adaptation support of multiple antennas Goals of IEEE 802.16 Communication Technology Laboratory Wireless Communication Group

  8. IEEE 802.16 Family • 802.16: initial version. 10-66 GHz line-of-sight (LOS) in year 2002 • 802.16a: extension 2-11 GHz (no line-of-sight) NLOS in year 2003 • 802.16b: quality of service (QoS) • 802.16c: interoperability with protocols and test-suite structures • 802.16d (802.16-2004): improvement of 802.16 and 802.16a (nomadic) • 802.16e (802.16e-2005): support fixed and mobile broadband (PHY and MAC layers) • 802.16f: coverage improvement based on mesh networks • 802.16g: support mobility at higher layers • 802.16j: mobile multihop relaying • 802.16m: Air Interface for Fixed and Mobile Broadband Wireless Access Systems - Advanced Air Interface Source: [4] Communication Technology Laboratory Wireless Communication Group

  9. Status of IEEE 802.16 (as of 10/2010) Communication Technology Laboratory Wireless Communication Group

  10. Status of IEEE 802.16 (as of 10/2010) http://standards.ieee.org/getieee802/download/802.16-2009.pdf Communication Technology Laboratory Wireless Communication Group

  11. http://www.wimaxforum.org/http://www.wimaxforum.org/LiteratureRetrieve.aspx?ID=177981 Communication Technology Laboratory Wireless Communication Group

  12. Scope of the Standard data/control plane • service specific convergence sublayer • convergence functions to support different protocols (ATM, Ethernet, IP) • handles connection oriented and connectionless traffic • MAC common part sublayer • medium access • bandwidth management • MAC management signaling • addressing • connection management • security sublayer • privacy • authentification • encryption • four different physical layers • single carrier 11GHz-66GHz LoS • single carrier 2GHz-11GHz NLoS • OFDM 2GHz-11GHz NLoS portable • OFDMA 2GHz-6GHz NLoS mobile CS SAP service specific convergence sublayer (CS) MAC SAP MAC common part sublayer (CPS) security sublayer PHY SAP physical layer (PHY) Communication Technology Laboratory Wireless Communication Group

  13. IEEE 802.16 Key Features • Channel bandwidth varying from 1.25 to 20 MHz. • Connection-oriented services • Strong security • Multicast support • Low latency,low packet loss handovers • Coverage radius up to 50km theoretical (802.16) or 8km (802.16a) • Data rate up to 75 Mbps • 10-60 GHz LOS (802.16), 2-11GHz NLOS (802.16a) Source: [4] Communication Technology Laboratory Wireless Communication Group

  14. Difference and similarity to IEEE 802.11 family (Wi-Fi) If WiMAX provides services analogous to a cellphone, Wi-Fi is more analogous to a cordless phone. Communication Technology Laboratory Wireless Communication Group

  15. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  16. IEEE 802.16 offers a huge array of options potential source of problems for compatibility and interoperability solution: profiles the WiMAX forum defines system and certification profiles specific set of parameters for different application scenarios and ensures compatibility by certification nonprofit organization founded in June, 2001 more than 400 members as of 2006 mission: facilitate the deployment of IEEE 802.16 based broadband wireless equipment by ensuring compatibility and interoperability http://www.wimaxforum.org The WiMAX Forum: An Industry-Led Non-Profit Organization to Promote IEEE802.16 Systems Communication Technology Laboratory Wireless Communication Group

  17. WiMAX profiles System Profiles: • industry selection of features for MAC and PHY from the 802.16 specifications • determines the required and conditionally required features for implementation • maintains the mandatory or optional status in 802.16 standards • forms the basis for testing conformance and interoperability • does not exclude other implementations of the standard Certification Profiles: • contains band of operation, duplexing option and bandwidth • an example profile would be 2.5 GHz, TDD and 5MHz • certification profiles provide a mechanism to identify devices in various markets to be certified Example • the current fixed profiles define for both TDD and FDD profiles • all of the mobile profiles are TDD only • the fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10 MHz. • the mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16 standard allows far wider variety of channels, but only the above subsets are supported as WiMAX profiles). Communication Technology Laboratory Wireless Communication Group

  18. Spectrum allocation • There is no uniform global licensed spectrum for WiMAX. • In the US, the biggest segment available is around 2.5 GHz, • Elsewhere in the world, the most likely bands used will be around 3.5 GHz, 2.3/2.5 GHz, or 5 GHz, • 2.3/2.5 GHz probably being most important in Asia. • Analogue TV bands may become available for WiMAX use, • await the complete rollout of digital TV. • In the U.S. The FCC auction for this spectrum is scheduled for the end of 2007. • EU has suggested re-allocation of 500-800 MHz spectrum for wireless communication, including WiMAX. • Manufacturers are compelled to provide multi-spectrum devices that can be used across different regions and regulatory requirements. Communication Technology Laboratory Wireless Communication Group

  19. World frequency map WCS: Wireless Communication Systems BRS: Broadband Radio Service Communication Technology Laboratory Wireless Communication Group

  20. Spectral Auction of the 700MHz TV Band in the USA (Spring 2008) Communication Technology Laboratory Wireless Communication Group

  21. Results of the Spectral Auction in Germany, Spring 2010 („Digitale Dividende“) Communication Technology Laboratory Wireless Communication Group

  22. IEEE 802.16 Mobility Support and WiMAX Forum Usage Scenarios handover Communication Technology Laboratory Wireless Communication Group

  23. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  24. IEEE 802.16 MAC • MAC supports multiple 802.16 PHY layers • In IEEE802.11 the most widely used MAC is contention based (DCF) • robust, as it does not require central coordination • difficult to meet QoS requirements • connection-less MAC service • In contrast, the 802.16 MAC uses a scheduling algorithm. The SS need to compete once (for initial entry into the network). • after that it is allocated an access slot by the base station. • the time slot can enlarge and contract, but remains assigned to the subscriber station which means that other subscribers cannot use it. • connection-oriented MAC service. • the scheduling algorithm also allows the base station to control QoS parameters by balancing the resource assignments among the SSs. Communication Technology Laboratory Wireless Communication Group

  25. MAC Key Features Source: [4] Communication Technology Laboratory Wireless Communication Group

  26. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  27. single carrier 11GHz-66GHz LoS single carrier 2GHz-11GHz NLoS OFDM 2GHz-11GHz NLoS portable: WMAN-OFDM OFDMA 2GHz-6GHz NLoS mobile: WMAN-OFDMA WiMAX PHY Communication Technology Laboratory Wireless Communication Group

  28. CC: convolutional code RS: Reed Solomon Code CTC: convolutional turbo code BTC: block turbo code LDPC: low density parity check code AAS: adaptive antenna systems STC: space-time coding MIMO: multiple input multiple output (spatial multiplexing) WirelessMAN-OFDM and -OFDMA Overview source: [1] Communication Technology Laboratory Wireless Communication Group

  29. OFDM PHY Key Features Source: [4] Communication Technology Laboratory Wireless Communication Group

  30. 256 subcarriers 192 data subcarriers 56 NULL subcarriers 8 pilot subcarriers system bandwidth W is an integer multiple of 1.25MHz, 1.5MHz, 1.75MHz, 2MHz or 2.75MHz proportional to the temporal sampling frequency Fs to achieve different system bandwidths, the equipment must support different sampling frequencies the duration of the OFDM symbol is approximately given by the variable g determines the guard time (cyclic extention) between consecutive OFDM symbols OFDM subcarrier assignment data subcarrier pilot subcarrier .... . .... .... .... .... .... .... .... . frequency -88 -63 -38 -13 13 38 63 88 -128 -101 101 128 0 subcarrier index 0 NULL subcarrier subcarrier spacing F system bandwidth W Communication Technology Laboratory Wireless Communication Group

  31. TDM multiplexing on DL full OFDM symbol allocated to a SS on UL optional subchannels each SS uses only a nonoverlapping fraction of all subcarriers of an OFDM symbol each subchannel has 12 data subcarriers and 1 pilot subcarrier four chunks of 3 data subcarriers each maximum 16 subchannels SS may use 1, 2, 4, 8 or 16 subchannels the data subcarrier chunks of each subchannel are distributed across the whole system bandwidth impact on channel estimation (channel estimation on basis of preamble) OFDM subchannels SS B 31 . . . 29 17 15 SS A SS A subchannel index . . . SS C 3 1 time Communication Technology Laboratory Wireless Communication Group

  32. OFDM: modulation and coding schemes Communication Technology Laboratory Wireless Communication Group

  33. Outline • Wireless Metropolitan Area Networks • IEEE 802.16 family of WMAN standards • The WiMax Forum • IEEE 802.16 MAC Layer • IEEE 802.16 OFDM based Physical Layer • Mobile WiMAX key features Communication Technology Laboratory Wireless Communication Group

  34. in December 2005 the IEEE ratified the 802.16e amendment • support mobility • WiMAX forum is defining system performance and certification profiles • air interface • network architecture necessary to implement an end-to-end Mobile WiMAX network • Mobile Technical Group (MWG) • air interface (mandatory and optional features of the IEEE standard) • release-1 covers 5, 7, 8.75 and 10MHz channel bandwidth at 2.3, 2.5 3.3 and 3.5GHz bands • Network Working Group (NWG) • higher layer networking specifications Mobile WiMAX Communication Technology Laboratory Wireless Communication Group

  35. WiMAX Design Challenges • Mobility causes the SS to communicate with several BS • Identification must be fast and reliable. More demanding than for fixed systems. • Full mobility: the user expects a seamless connection (similar to 3G/4G systems) • Mobility support for the transport (IP) layer: may require authentication and handoffs for up and downlink IP packets and MAC frames • Support low power devices (battery autonomy) Communication Technology Laboratory Wireless Communication Group

  36. Overview of Key Features • Scalable OFDMA: scaling of channel bandwidth by FFT size with constant subcarrier spacing • results in a higher spectrum efficiency in wide channels • cost reduction in narrow channels • Improving NLOS coverage by • advanced antenna diversity schemes • hybrid-Automatic Retransmission Request (hARQ) error control • Improving capacity and coverage by • Adaptive Antenna Systems (AAS) • Multiple Input Multiple Output (MIMO) wireless • Increasing system margin by use of denser sub-channelization • improves indoor penetration • High-performance coding techniques such as Turbo Coding and Low-Density Parity Check coding (LDPC) enhance outage probability and NLOS performance • Downlink and uplink sub-channelization (multiple users per OFDM symbol) improves coverage, spectral efficiency and sum rate • New QoS class (enhanced real-time Polling Service) is more appropriate for VoIP applications. • Support for mobility (soft and hard handover (latencies < 50ms) between base stations) • most important aspects of WirelessMAN-OFDMA Communication Technology Laboratory Wireless Communication Group

  37. Time Division Duplex (TDD) • Standard supports TDD and FDD • But only TDD in the WiMAX mobile profile. • TDD enables adjustment of the downlink/uplink ratio to efficiently support asymmetric downlink/uplink traffic, while with FDD, downlink and uplink always have fixed and generally, equal DL and UL bandwidths. • TDD assures channel reciprocity for better support of link adaptation, MIMO and other closed loop advanced antenna technologies. • Unlike FDD, which requires a pair of channels, TDD only requires a single channel for both downlink and uplink providing greater flexibility for adaptation to varied global spectrum allocations. • Transceiver designs for TDD implementations are less complex and therefore less expensive. Communication Technology Laboratory Wireless Communication Group

  38. FUSC and PUSC subchannels • a common set of pilot tones is used by all subchannels • used, if all data subcarriers are allocated to subchannels (this may not be possible due to inter-cell interference) • requires the smallest overhead • DL partially used subcarriers (DL-PUSC) • six groups of subcarriers • each group uses individual pool of pilot subcarriers • the subchannels contain only data tones • UL-PUSC • each subchannel has its own pilot tones (required, because each subchannel may originate from a different user • support of subchannels on DL/UL • minimum frequency-time resource unit is one slot (48 data subcarriers) • two types of subcarrier permutations • diversity: random subcarrier selection across whole frequency band. • Provides diversity and inter-cell interference averaging • contiguous: block of adjacent subcarriers. Used for adaptive modulation and coding (AMC) and multiuser diversity. • DL fully used subcarriers (DL-FUSC) • each subchannel contains only data subcarriers Communication Technology Laboratory Wireless Communication Group

  39. SOFDMA Subcarrier Allocation and Modulation Schemes uplink requires more pilots due to OFDMA (each user has different channel) symbol period not affected by system bandwidth CC: convolutional code CTC: convolutional turbo code Optional: • Italic entries • Block turbo code and Low Density Parity Check code (LDPC) Communication Technology Laboratory Wireless Communication Group

  40. SOFDMA Parameters Source: [1] Communication Technology Laboratory Wireless Communication Group

  41. Fractional Frequency Reuse • Users close to the BS operate on the zone with all subchannels available (F1+F2+F3) • For the edge users, each cell or sector operates on the zone with a faction of the subchannels available (F1, F2 or F3) • Frequency reuse 1 for center users for max spectral efficiency • Fractional frequency reuse for edge users to assure connection quality and throughput Source: [1] Communication Technology Laboratory Wireless Communication Group

  42. Advanced Antenna Systems • Smart antennas increase the spectral density and the SNR. Supported are: • Spatial diversity (> 1 antenna at BS, placed at least half a wavelength apart, for selection combining) • Spatial multiplexing (SM) and collaborative SM • For the UL, each user has a single transmit antenna, and two users can transmit collaboratively in the same timeslot • Beamforming antennas • Space-time codes (TX diversity like Alamouti scheme) Source: [1],[4] Communication Technology Laboratory Wireless Communication Group

  43. bandwidth 10MHz frame duration 5ms uplink: max. 16-QAM; r=3/4 CTC downlink: max. 64-QAM; r=5/6 CTC PUSC sub-channels 44 data OFDM symbols Maximum Data Rates for SIMO/MIMO Configurations (Mandatory Regime) one sector comprises multiple users collaborative MIMO" Communication Technology Laboratory Wireless Communication Group

  44. QoS Categories Source: [1] Communication Technology Laboratory Wireless Communication Group

  45. the scheduler efficiently allocates resources in response to bursty data traffic and changing channel conditions the scheduler at the basestation schedules both DL and UL traffic requires accurate and timely information about MS traffic conditions and QoS requirements multiple UL bandwidth request mechanisms ranging channel piggyback requests (with data payload) polling (by basestation) the UL service flow defines the feedback mechanism for each UL connection dynamic resource allocation support of time, space and frequency resource allocation on a per-frame basis delivered in the MAP messages at the beginning of each frame benefit of doing the UL scheduling at the BS BS knows the QoS requirements of all MS and can allocate the UL resources more efficiently MAC scheduling services Communication Technology Laboratory Wireless Communication Group

  46. Sources [1] Mobile WiMAX – Part 1: A Technical Overview and Performance Evaluation. WiMAX Forum. August 2006. http://www.wimaxforum.org/technology/downloads/Mobile_WiMAX_Part1_Overview_and_Performance.pdf [2] WiMAX. Intel Technology Journal. Vol 8, issue 3. August 2004. ftp://download.intel.com/technology/itj/2004/volume08issue03/vol8_iss03.pdf [3] Introduction to WiMAX Air Interface. S. Shawn Tsai. Business Unit Access, Ericsson AB. September 2006. Presentation NCTU http://140.113.13.93/wireless/download/material/NCTU%20Tutorial%20one%20per%20page.pdf [4] WiMAX: taking wireless to the MAX. Deepak Pareek - Auerbach Publications c/o Taylor & Francis. 2006. http://www.itknowledgebase.net/books/4565/au7186_fm.pdf (e-text from ETH-Bibliothek) [5] WiMax and Wi-Fi: Separate and Unequal, Cherry, S.M. Spectrum, IEEE, Vol.41, Iss.3, March 2004. http://ieeexplore.ieee.org/iel5/6/28451/01270541.pdf?isnumber=28451∏=JNL&arnumber=1270541&arnumber=1270541&arSt=+16&ared=+16&arAuthor=Cherry%2C+S.M. Communication Technology Laboratory Wireless Communication Group

  47. Mobile Radio Standards (10/2011) http://en.wikipedia.org/wiki/Template:Cellular_network_standards Communication Technology Laboratory Wireless Communication Group

  48. Commercial Deployment Example: Clearwire http://www.clear.com/discover http://www.clearwire.com/ Communication Technology Laboratory Wireless Communication Group

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