January 2005 Doc IEEE 802 22 05 0005

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Tutorial on Multi Access OFDM (OFDMA) Technology IEEE P 802. 22 Wireless RANs Date: 2005 -01 -04 Authors: Notice: This document has been prepared to assist IEEE 802. 22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802. 22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http: //standards. ieee. org/guides/bylaws/sb-bylaws. pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard. " Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802. 22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee. org. > Submission Runcom Technologies Ltd. 1 Eli Sofer, Runcom 1

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Abstract The contribution presents a tutorial on Multi Access OFDM (OFDMA) technology which has been endorsed in leading standards such as- ETSI DVB-RCT and IEEE 802. 16 a, d and 16 e. Essential parameters of Up. Link and Down. Link and simulation results are presented. System capabilities and advantages are also discussed. The tutorial could offer an insight and understanding of OFDMA technology to be considered as a candidate for WRAN system Submission Runcom Technologies Ltd. 2 Eli Sofer, Runcom 2

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Tutorial on Multi Access OFDM (OFDMA) Technology Eli Sofer Runcom Technologies Ltd Submission Runcom Technologies Ltd. 3 Eli Sofer, Runcom 3

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Contents • • OFDMA System Architecture Illustrated Example OFDMA System Properties Coverage and Capacity Submission Runcom Technologies Ltd. 4 Eli Sofer, Runcom 4

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA System Architecture Submission Runcom Technologies Ltd. 5 Eli Sofer, Runcom 5

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 • Duplexing Technique FDD/TDD • Multiple Access Method TDMA/OFDMA OFDM Symbols allocated by TDMA Sub-Carriers within an OFDM Symbol allocated by OFDMA • Diversity Frequency, Time, Code (CPE and BS), Space Time Coding, Antenna Array Submission Runcom Technologies Ltd. 6 Eli Sofer, Runcom 6

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Duplexing - Principles FDD (Frequency Division Duplexing ) Uses One Frequency for the Down. Link, and a Second Frequency for the Up. Link. TDD (time Division Duplexing) Uses the same frequency for the Downlink and the Uplink. In any configuration the access method is OFDMA/TDMA. Submission Runcom Technologies Ltd. 7 Eli Sofer, Runcom 7

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA-TDMA Principles Using OFDMA/TDMA, Sub Channels are allocated in the Frequency Domain, and OFDM Symbols allocated in the Time Domain. Submission Runcom Technologies Ltd. 8 Eli Sofer, Runcom 8

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Down. Link OFDMA Symbol Submission Runcom Technologies Ltd. 9 Eli Sofer, Runcom 9

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Down. Link Specification • Burst Structure is defined from one Sub-channel in the Frequency domain and n OFDMA time symbols in the time domain, each burst consists of N data modulated carriers. • Adaptive Modulation and Coding per Sub-Channel in the Down-Link • Forward APC controlling (+6 d. B) – (-6 d. B) digital gain on the transmitted Sub-Channel • Supporting optional Space Time Coding employing Alamouti STC. • Supporting optional Adaptive Array. Submission Runcom Technologies Ltd. 10 Eli Sofer, Runcom 10

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example- Down. Link Specification • FFT size : 2048 • Guard Intervals : ¼, 1/8, 1/16, 1/32 • Coding Mandatory: concatenated RS GF(256) and Convolutional coding (k=7, G 1=171, G 2=133, keeping overall coding rate to = ½, ¾ • Coding Optional: Convolutional Turbo Code (CTC), Turbo Product Code (TPC) with coding rates close to = ½, ¾ • QPSK, 16 QAM, 64 QAM modulation • Modulo 4, Pilot based Symbol Structure. • 32 Sub-Channels of 48 data carriers each Submission Runcom Technologies Ltd. 11 Eli Sofer, Runcom 11

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Downlink Pilot and Data Carriers Allocation Scheme Submission Runcom Technologies Ltd. 12 Eli Sofer, Runcom 12

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Space Time Coding Subcarrier modulation IFFT Filter DAC RF Tx diversity encoder IFFT input packing Tx Rx RF DAC Submission Runcom Technologies Ltd. Filter Diversity Combiner FFT 13 Subchannel demod. Log. Likelihood ratios Decoder Eli Sofer, Runcom 13

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Up. Link OFDMA Symbol Submission Runcom Technologies Ltd. 14 Eli Sofer, Runcom 14

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example of Up. Link Specification • Burst Structure is defined from one Sub-channel in the Frequency domain and 3 OFDMA time symbols in the time domain, each burst consists of 144 data modulated carriers. • Adaptive Modulation and Coding per User in the Up. Link • User Can be allocated 1 up to 32 Sub-Channels • 2 Sub-Channels are used as the Ranging Sub-Channels for User Ranging and fast Band-Width Request. Submission Runcom Technologies Ltd. 15 Eli Sofer, Runcom 15

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example of Up. Link Specification • FFT size : 2048 • Guard Intervals : ¼, 1/8, 1/16, 1/32 • Coding Mandatory: concatenated RS GF(256) and Convolutional coding (k=7, G 1=171, G 2=133, keeping overall coding rate to = ½, ¾ • Coding Optional: Convolutional Turbo Code (CTC), Turbo Product Code (TPC) with coding rates close to = ½, ¾ • QPSK, 16 QAM, 64 QAM modulation • Modulo 13, Pilot based Sub-Channel Structure. • 32 Sub-Channels of 53 carriers each, 5 carriers used as pilots, 48 carriers used for data Submission Runcom Technologies Ltd. 16 Eli Sofer, Runcom 16

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example for Up. Link Sub-Channel Pilot and Data Carriers Allocation Scheme Submission Runcom Technologies Ltd. 17 Eli Sofer, Runcom 17

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Using Special Permutations for carrier allocation • All usable carriers are divided into 32 carrier groups named basic group, each main group contains 53 basic groups. Submission Runcom Technologies Ltd. 18 Eli Sofer, Runcom 18

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Using Special Permutations for carrier allocation • Carriers are allocated by a basic series and it’s cyclic permutations for example: • Basic Series: 0, 5, 2, 10, 4, 20, 8, 17, 16, 11, 9, 22, 18, 21, 13, 19, 3, 15, 6, 7, 12, 14, 1 • After two cyclic permutations we get: 2, 10, 4, 20, 8, 17, 16, 11, 9, 22, 18, 21, 13, 19, 3, 15, 6, 7, 12, 14, 1, 0, 5 Submission Runcom Technologies Ltd. 19 Eli Sofer, Runcom 19

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Using Special Permutations for carrier allocation • The Carriers of each Sub-Channel are spread all over the usable frequency for best frequency diversity • The allocation by permutation gives an excellent Reuse factor - almost 1. • The allocation by permutation give an excellent interference spreading and averaging. Submission Runcom Technologies Ltd. 20 Eli Sofer, Runcom 20

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Using CDMA like modulation for Ranging • The CDMA like synchronization is achieved by allocating several of the usable Sub-Channels for the Ranging process, the logic unit they consist is called a Ranging Sub-Channel. • Onto the Ranging Sub-Channel users modulate a Pseudo Noise (PN) sequence using BPSK modulation • The Base Station detects the different sequences and uses the CIR that he derives from the sequences for: – Time and power synchronization – Decide on the user modulation and coding Submission Runcom Technologies Ltd. 21 Eli Sofer, Runcom 21

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 DVB-RCT MAC Performance • Aloha vs. CDMA BW request (32 codes) – CDMA efficiency is better by a factor of six – CDMA latency is better by a factor of four Submission Runcom Technologies Ltd. 22 Eli Sofer, Runcom 22

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Illustrated Example Submission Runcom Technologies Ltd. 23 Eli Sofer, Runcom 23

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example • • • Subscriber Units at the Current OFDMA Symbol = 3 Sub-Channels Allocated to Subscriber-Unit #1 = 12 Sub-Channels Allocated to Subscriber-Unit #2 = 9 Sub-Channels Allocated to Subscriber-Unit #3 = 6 Number Of New Subscriber-Units Requesting Services = 3 All Subscriber-Units Suffer Different Multi-Paths and different Attenuation's Submission Runcom Technologies Ltd. 24 Eli Sofer, Runcom 24

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example • Constellation at the Base Station Submission Runcom Technologies Ltd. 25 Eli Sofer, Runcom 25

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example • Users Separation Submission Runcom Technologies Ltd. 26 Eli Sofer, Runcom 26

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Example - Results • User Estimation Submission Runcom Technologies Ltd. 27 Eli Sofer, Runcom 27

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Results • User Estimation Submission Runcom Technologies Ltd. 28 Eli Sofer, Runcom 28

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Results • User Estimation Submission Runcom Technologies Ltd. 29 Eli Sofer, Runcom 29

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Results • Finding New Subscriber-Units Requesting Services, Using the Ranging Pilots (CDMA/OFDM Techniques) Submission Runcom Technologies Ltd. 30 Eli Sofer, Runcom 30

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA System Properties Submission Runcom Technologies Ltd. 31 Eli Sofer, Runcom 31

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Interference Rejection/Avoidance • Narrowband Interference Rejection – Easy to Avoid/Reject Narrowband Dominant Interference. – Less Interfered Part of the Carrier Can Still Be Used. Submission Runcom Technologies Ltd. 32 Eli Sofer, Runcom 32

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 PAPR Reduction • Using shaping on the signal peaks • Limiting the PAPR to a constant value by vector reduction Submission Runcom Technologies Ltd. 33 Eli Sofer, Runcom 33

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Spectrum Properties • Rectangular Spectrum Shape (Brick Wall) • Small Frequency Guard band Submission Runcom Technologies Ltd. 34 Eli Sofer, Runcom 34

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Spectrum Properties Submission Runcom Technologies Ltd. 35 Eli Sofer, Runcom 35

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Group Delay In OFDM, channel impairment are solved in the same way Group Delays are solved, by Channel estimation Submission Runcom Technologies Ltd. 36 Eli Sofer, Runcom 36

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Phase Noise Effects Phase Noise Effect on S. C Phase Noise Effect on OFDM Submission Runcom Technologies Ltd. 37 Eli Sofer, Runcom 37

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 • Timing Sensitivity Low timing sensitivity is needed, and simple phase and channel estimators solve timing problems. • Frequency Sensitivity solved by locking onto the Base-Station transmission and deriving the Subscriber Unit’s clocks from it. • Equalization No Equalizers are needed, channel impairment and timing problems are both solved with simple phase and channel estimators Submission Runcom Technologies Ltd. 38 Eli Sofer, Runcom 38

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 System Coverage and Capacity Submission Runcom Technologies Ltd. 39 Eli Sofer, Runcom 39

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Using Reuse Factor of 1 By allocating different Sub-Channels to different sectors we can reach reuse factor of 1 with up to 12 sectors (changing the polarity enhances the performance) Submission Runcom Technologies Ltd. 40 Eli Sofer, Runcom 40

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Capacity · Use modulations with various Bit/Hz capabilities as Adaptive N-QAM. · Use Adaptive FEC (Convolutional & Reed-Solomon or Turbo code) · Maximal frequency reuse between cells/sectors (close to 1). · Maximum sectors allocation. · The use of statistical Multiplexing and concentration. · Adaptive Carrier Allocations. · Adaptive Power Control Submission Runcom Technologies Ltd. 41 Eli Sofer, Runcom 41

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Coverage Submission Runcom Technologies Ltd. 42 Eli Sofer, Runcom 42

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Coverage - Simulations Submission Runcom Technologies Ltd. 43 Eli Sofer, Runcom 43

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Coverage - Simulations · Multi Sector Coverage, 3 Sectors, 3 Frequencies, achieves 2. 8 Bits/s/Hz/Cell, 22. 5 Mbps/Sector Submission Runcom Technologies Ltd. 44 Eli Sofer, Runcom 44

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 Coverage - Simulations · Multi Sector Coverage, 6 Sectors, 6 Frequencies, achieves 2. 8 Bits/s/Hz/Cell, 22. 5 Mbps/Sector Submission Runcom Technologies Ltd. 45 Eli Sofer, Runcom 45

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA Advantages- Summary (1) • Averaging interference's from neighboring cells, by using different basic carrier permutations between users in different cells. • Interference’s within the cell are averaged by using allocation with cyclic permutations. • Enables orthogonality in the uplink by synchronizing users in time and frequency. • Enables Multipath mitigation without using Equalizers and training sequences. • Enables Single Frequency Network coverage, where coverage problem exists and gives excellent coverage. Submission Runcom Technologies Ltd. 46 Eli Sofer, Runcom 46

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA Advantages - Summary (2) • Enables spatial diversity by using antenna diversity at the Base Station and possible at the Subscriber Unit. • Enables adaptive modulation for every user QPSK, 16 QAM, 64 QAM and 256 QAM. • Enables adaptive carrier allocation in multiplication of 23 carriers = n. X 23 carriers up to 1587 carriers (all data carriers). • Offers Frequency diversity by spreading the carriers all over the used spectrum. • Offers Time diversity by optional interleaving of carrier groups in time. Submission Runcom Technologies Ltd. 47 Eli Sofer, Runcom 47

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA Advantages - Summary (3) • Using the cell capacity to the utmost by adaptively using the highest modulation a user can use, this is allowed by the gain added when less carriers are allocated (up to 18 d. B gain for 23 carrier allocation instead of 1587 carriers), therefore gaining in overall cell capacity. • The power gain can be translated to distance - 3 times the distance for R 4 and 8 time for R 2 for LOS conditions. • Enabling the usage of Indoor Omni Directional antennas for the users. • MAC complexity is the same as for TDMA systems. Submission Runcom Technologies Ltd. 48 Eli Sofer, Runcom 48

January 2005 Doc. : IEEE 802. 22 -05 -0005 r 0 OFDMA Advantages - Summary (4) • Allocating carrier by OFDMA/TDMA strategy. • Minimal delay per OFDMA symbol of 300 sec. • Using Small burst per user of about 100 symbols for better statistical multiplexing and smaller jitter. • User symbol is several times longer then for TDMA systems. • Using the FEC to the outmost by error detection of disturbed frequencies. Submission Runcom Technologies Ltd. 49 Eli Sofer, Runcom 49