1. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 1 System Description and Operation Principles for IEEE 802.22 WRANs IEEE P802.22 Wireless RANs Date: 2005-11-07 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl 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.patcom@iee.org >

2. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 2 Abstract OFDMA as the basic multiple-access scheme for both uplink and downlink Pre-transform for uplink to reduce peak-to-average power ratio (PAPR) TDD as the duplex mode, with adaptive guard time control to maximize the system throughput Distributed channel sensing using guard interval between dowlink subframe and uplink subframe The CPEs support the usage of single TV channel with variable channel bandwidth (6, 7 & 8MHz) The BS supports the usage of multiple TV channels, either contiguous or discontiguous Scalable bandwidth ranging from 1.25 MHz to 7.5 MHz for each CPE Preamble and pilot design to avoid interference to primary users Shortened block Turbo codes (SBTC) with special parity check matrix design Supporting transmit power control (TPC) and adaptive modulation and coding (AMC) Adaptive antennas for interference avoidance and channel shortening Transmit diversity, random beamforming and virtual MIMO Cellular deployment and sectorization for enhanced channel capacity

3. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 3 WRANs Operate in the VHF/UHF TV bands using cognitive radio technology –Sensing before using –No fixed spectrum available Co-exist with primary users, e.g. wireless microphone –Primary users have higher priority in channel usage Coverage range as large as 100 km –Large delay spread –Long propagation delay

4. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 4 Two-Layer OFDMA How? –1 st Layer: FDMA -- User allocation to TV channels –2 nd Layer: OFDMA -- Multiple access within each TV channel Advantages: –Provide user orthogonality –Most suitable for irregular spectrum (discontiguous TV channels, partial TV channel) –Exploit multiuser diversity

5. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 5 OFDMA A group of subcarriers is defined as a subchannel Each user is allocated with one or more subchannels Localized subchannel vs distributed subchannel Localized subchannel preferable for avoiding interference to primary users

6. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 6 OFDMA ParametersDescription BChanel bandwidth NFFT size Number of used subcarriers, including DC subcarrier Oversampling factor Subcarrier spacing TbTb Useful symbol duration TcTc Cyclic prefix duration T s =T c +T b OFDMA symbol duration Cyclic prefix factor

7. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 7 Scalable Design Each CPE supports one TV channel usage –OFDMA –Scalable bandwidth ranging from 1.25 MHz to 7.5 MHz –Scalable for 6 MHz, 7MHz and 8MHz TV channels BS supports the usage of multiple TV channels, either contiguous or discontiguous –Two-layer OFDMA for BS

8. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 8 Variable Bandwidths within one TV Channel ParametersValues Channel bandwidth 1.25 MHz2.5 MHz5 MHz 7.5 MHz Sampling frequency* 1.4286 MHz2.8571 MHz5.7143 MHz 8.5714 MHz Sampling interval0.7 μs0.35 μs0.175 μs 0.1167 μs FFT size2565121024 1536 Subcarrier spacing 5.5804 kHz Useful OFDMA symbol interval 179.2 μs * Oversampling factor of 8/7

9. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 9 Support Variable TV Channel Bandwidths of 6, 7 & 8MHz Option A: Fixed sampling frequency –Adding variable number of nulls Option B: Variable sampling frequency –Keeping same number of useful subcarriers

10. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 10 Option A for Variable TV Bandwidth TV channel bandwidth8 MHz7 MHz6 MHz Sampling frequency7.5MHz*8/7 = 8.5714 MHz FFT size1536 Number of useful subcarriers 12491145937 Data/pilot subcarriers per subchannel 48/4 Number of subchannels242218

11. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 11 Option A with Variable CP Length CP factor1/161/81/43/8 * CP length11.2 μs22.4 μs44.8 μs 67.2 μs OFDMA symbol interval 190.4 μs201.6 μs224 μs246.4 μs * optional, to support repeater applications

12. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 12 Option A: Minimum Peak Rates DownlinkUplink Channel bandwidth1.25 MHz Total No of subcarriers256 No of used subcarriers209 No of subchannels4 No of data subcarriers per subchannel48 No of pilot subcarriers per subchannel4 No of subchannels per user42 Minimum peak rates 1.513 Mbps (QPSK, ¾ rate, 1/16 CP factor) 504 kbps (QPSK, ½ rate, 1/16 CP factor)

13. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 13 Option B for Variable TV Bandwidth TV channel bandwidth8 MHz7 MHz6 MHz Sampling Frequency 8/7*8 = 9.14MHz 8/7*7 = 8 MHz 8/7*6 = 6.86 MHz FFT size1024 / 2048 Number of useful subcarriers 864 / 1728 CP length(28 / 14 / 7 us) / (56 / 28 / 14 us) Spectrum efficiency (With ~1/16 CP factor) 78% Number of subchannels 27 (32 / 64 subcarriers per subchannels)

14. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 14 Option B: System Parameters

15. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 15 TDD as the Duplex Mode Why TDD? –Difficult to identify paired spectrum for FDD Drawback of TDD –Large BS TTG due to long propagation delay Our proposals –Adaptive guard time control to increase system throughput –A sensing slot allocated for distributed channel sensing after DL subframe

16. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 16 Basic TDD Frame Structure

17. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 17 DL Subframe DL Preamble –transmitted in the first OFDMA symbol of the TDD frame –used by CPEs for time synchronization, frequency synchronization and channel estimation FCH contains the Downlink Frame Prefix (DLFP) which specifies: –used subchannel bitmap, ranging channel indication, coding scheme for DL/UL-MAP, DL/UL-MAP length DL-MAP specifies: –Frame duration (in # of OFDMA symbols) and frame number –Subchannel allocation for each DL burst (subchannel and symbol offsets). –Coding/modulation scheme used for each DL burst UL-MAP specifies: –Subchannel allocation for each UL burst (subchannel and symbol offsets) –Coding/modulation scheme for each UL burst –UL-subframe start time for each burst (relative to the beginning of the frame) due to the use of adaptive TDD

18. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 18 UL Subframe Preamble is not necessary if pre-equalization is done at CPEs Otherwise, the first OFDMA symbol of a UL burst is designed as the UL preamble One subchannel can be assigned for ranging and BW request A sensing slot after DL subframe is designed for BS and all CPEs to sense the primary users Adaptive TDD is proposed to reduce required BS TTG

19. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 19 Adaptive TDD Frame Structure Near-by users are allowed to transmit earlier than far- away users Reduced BS TTG for increased throughput

20. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 20 Adaptive TDD time CPE3 is the nearest user while CPE2 and CPE4 are the farthest user. S1S2S3S4S5S6S7S8S9 CPE1 GGpreGdataG G G G G G CPE2 GGGpreGdataG G G G G CPE3 GpreGdataG G G G G G G CPE4 GGGpreGdataG G G G G CPE5 GGpreGdataG G G G G G

21. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 21 Channel Sensing and Adaptive TDD T ss = n * T b, n = 1, 2, 3… TTG1 > TRS + T ss TTG2 – TTG1 = k * T s, k = 1, 2, 3… A sensing slot after DL subframe for BS and CPEs to sense the channel DL Subframe DL2 DL Subframe UL 2 SSRTG TRS Sense Tss Sense Tss Sense Tss UL 1 SSRTG TTG1 TTG2 UL 2UL 1 DL2 DL1 CPE2 CPE1 BS DS1 DS2

22. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 22 Other Channel Sensing Options BS SensingCPE Sensing Sensing Duration = 100 ~ 200 us Sensing Frequency = 200~300Hz

23. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 23 Other Channel Sensing Options BS Sensing (at distributed subcarrier positions) CPE Sensing (at distributed subcarrier positions) Sensing Duration = 100 ~ 200 us Sensing Frequency = 200~300Hz

24. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 24 Channel Sensing Using Null Subcarriers

25. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 25 OFDMA Transmitter for BS... Data K Data 1 Preamble Pilot Two-layer OFDMA Formulator Windowing & Pulse Shaping Randomizer FEC Encoder Interleaver Symbol Mapper Pre-transform Randomizer FEC Encoder Interleaver Symbol Mapper Pre-transform

26. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 26 OFDMA Transmitter for CPE... Data Randomizer FEC Encoder Interleaver Symbol Mapper Preamble/ Pilot OFDMA Formulator Zeros Windowing & Pulse Shaping Pre-transform

27. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 27 Randomizer Only information bits are randomized but preambles are not randomized Information of sub-channel offset and symbol offset are used to initialize the state of the randomizer for different data block.

28. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 28 FEC Encoder: Convolutional Code (CC) Native code: –Rate ½ with constraint length: 7 –Generator polynomials: 171 oct, 133 oct Other coding rates through puncturing –2/3, ¾, 5/6

29. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 29 FEC Encoder: Block Turbo Code (BTC) Component code –Extended Hamming code Native code: (16,11), (32,26) and (64,57) Other code rate through shortening –Parity check code (8,7) and (16,15)

30. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 30 Parity Check Matrices for Hamming Codes N’ = 15 K’ = 11 N’ = 31 K’ = 26 N’ = 63 K’ = 57 Special parity check matrix design simplifies the decoding complexity. The syndrome value gives the error position, thus, look-up table is not needed.

31. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 31 Shortened Block Turbo Code (SBTC) Structure

32. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 32 Data Payload for One Subchannel: SBTC Modulation Scheme QPSK8PSK16-QAM64-QAM Coded Bytes Encoding Rate ~1/2~2/3~3/4~5/6~1/2~2/3~1/2~2/3~3/4~5/6~1/2~2/3 Allowed Data (Bytes) / No of symbols 6/19/1 12 16/220/216/120/1 24 16/325/316/225/216/125/1 36 23/435/423/235/2 48 31/5 60 40/640/440/340/2 72

33. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 33 Interleaver s: half of the number of coded bits per subcarrier k: the index of the coded bit before the first permutation i: index after the first and before the second permutation j: index after the second permutation N cbps : number of coded bits per encoded block First permutation (Block interleaver) i = (N cbps /16) (k mod 16) + floor(k/16) k = 0,1,…,N cbps – 1 Second permutation (Interleaving within the modulated symbol) j = s × floor(i / s) + (i + N cbps – floor(16i / N cbps )) mod s i = 0,1,… N cbps – 1

34. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 34 Pre-Transforms IFFT (size N) 0 0 0 0 0 0 0 0 P/S Cyclic Prefix S/PTransform (size M) Localized or distributed mapping Applicable to both UL and DL

35. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 35 Pre-Transforms Transform matrix: –DFT matrix multiplied by diag(1, α, …, α M-1 ), α = exp(-jπ/2M) or 1 –Walsh-Hadamard matrix –Identity matrix Uplink –Single carrier system if DFT matrix is used –Localized FDMA vs Interleaved FDMA –Low PAPR A BC Frequency A BC A BC ABCABCABCABC Interleaved FDMA ABC Frequency ABCABCABCABCABC Localized FDMA

36. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 36 Adaptive Modulation and Coding (AMC) Modulation schemes: –Downlink: QPSK, 16-QAM, 64-QAM, 256 QAM –Uplink: BPSK, QPSK, 8-PSK, 16-QAM, 64 QAM Code rates (CC and BTC): –1/2, 2/3, 3/4, 5/6 –Convolutional Codes (CC) and Block Turbo Codes (BTC)

37. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 37 Variable Throughput (1.25MHz, Downlink) minimum downlink peak rate ModulationCode rateData rate (in Mpbs) for different CP factor 3/81/41/81/16 QPSK ½0.7790.8570.9521.008 2/31.0391.1431.2701.345 ¾1.1691.2861.429 1.513 5/61.2991.4291.5871.681 16-QAM ½1.5581.7141.9052.017 2/32.0782.2862.5402.689 ¾2.3382.5712.8573.025 5/62.5972.8573.1753.361 64-QAM ½2.3382.5712.8573.025 2/33.1173.4293.8104.034 ¾3.5073.8574.2864.538 5/63.8964.2864.7625.042 256-QAM ½3.1173.4293.8104.034 2/34.1564.5715.0795.378 ¾4.6755.1435.7146.050 5/65.1955.7146.3496.723

38. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 38 Variable Throughput (1.25MHz, Uplink) minimum uplink peak rate ModulationCode rateData rate (in Mpbs) for different CP factor 3/81/41/81/16 BPSK ½0.1950.2140.2380.252 2/30.2600.2860.3180.336 ¾0.2920.3210.3570.378 5/60.3250.3570.3970.420 QPSK ½0.3900.4290.4760.504 2/30.5200.5710.6350.672 ¾0.5840.6430.7140.756 5/60.6490.7140.7940.840 16-QAM ½0.7790.8570.9521.008 2/31.0391.1431.2701.345 ¾1.1691.2861.4291.513 5/61.2991.4291.5871.681 64-QAM ½1.1941.2861.4291.513 2/31.5591.7151.9052.017 ¾1.7541.9292.1432.269 5/61.9482.1432.3812.521

39. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 39 Transmit Power Control (TPC) Objectives of TPC –Maintaining the reliability of communication when there are changes in channel and propagation conditions. –Conserving power while reducing interference. Transmitters must support monotonic TPC with range of up to 30 dB, 1 dB steps, and ± 0.5 dB accuracy. Transmit power control will be supported on link-by- link basis

40. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 40 Preamble and Pilot Design  DL preamble  Time synchronization, frequency synchronization and channel estimation  UL preamble  channel estimation  DL and UL pilot allocations in each OFDMA symbol for channel parameter estimation and tracking  Preamble and pilot design avoiding interference to primary users

41. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 41 DL Preamble The first OFDMA symbol of DL subframe –Periodic with period N/2 in time domain –The locations of active subcarriers are: 2k, k=0,1,…,N/2-1. If the subcarrier coincides with the DC or a guard subcarrier, or a subcarrier used by a primary user, set the value on the subcarrier to zero. Use a PN sequence to generate the values for the active subcarriers. –Low PAPR consideration –Each cell uses a different PN

42. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 42 UL Preamble UL preamble may be not necessary if pre- equalization is done at CPE, otherwise, a preamble is needed for channel estimation Each user sends a user dependent preamble to the BS to aid the estimation of channels at the BS. –Constructed from the basic preamble by setting all the subcarriers which are not allocated to the user as null subcarriers If the subcarrier is used by a primary user, set the value on the subcarrier to zero. Use a PN sequence to generate the values for the active subcarriers –Low PAPR consideration –Each cell uses a different PN

43. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 43 Pre-Equalization for Uplink The wireless channel usually changes slowly, we can use the channel estimated based on the downlink preamble to do pre- equalization for uplink. Let H(k,n) be the frequency domain channel response for user k at subcarrier n. The pre-equalized signal for user k is – where where s(k,n): modulated symbol for user k at subcarrier n B(k): subcarrier index set for user k p(k,n): power constraint factor such that (C(k) is the power for user k)

44. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 44 DL Pilot There are N/16 pilot subcarriers spread over the whole spectrum Two types of pilots –Fixed-location pilots: Subcarrier locations for the fixed location pilots remain unchanged in every OFDMA symbol. –Variable-location pilots: subcarrier locations for the variable location pilots change in every four OFDMA symbols. N/64 fixed-location pilots (1 for each subchannel) –Locations: 52k+1 and N/2+(3N/32)+52k+1, k=0,1,…,N/128-1. (N/16-N/64) variable-location pilots (3 for each subchannel) –Locations: 13k+3(L mod 4)-5 and N/2+(3N/32)+13k+3(L mod 4)-5, k=0,1,…,N/32-1 (k is not divisible by 4). (L is the OFDMA symbol index.) In all cases, if the pilot subcarrier coincides with a subcarrier used by a primary user, set the value on the pilot subcarrier to zero

45. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 45 DL Pilot Subcarrier Allocation (N =256) Fixed pilot1 53 153 205 Variable pilot (symbol 0)8 21 34 60 73 86 160 173 186 212 225 238 Variable pilot (symbol 1)11 24 37 63 76 89 163 176 189 215 228 241 Variable pilot (symbol 2)14 27 40 66 79 92 166 179 192 218 231 244 Variable pilot (symbol 3)17 30 43 69 82 95 169 182 195 221 234 247

46. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 46 UL Pilot The subcarriers are first divided into clusters with each cluster having 13 subcarriers. Each cluster has one pilot subcarrier. The pilot location is varying in three OFDMA symbols. –The location in a cluster is: 4(L mod 3)+3, L is the OFDMA symbol index. If the pilot subcarrier coincides with a subcarrier used by a primary user, set the value on the pilot subcarrier to zero.

47. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 47 Multiple Antenna Technologies Transmit diversity –Robustness to fading effect Transmit beamforming –Range extension –Interference avoidance –Delay spread reduction Spatial multiplexing –Increased throughput for dedicated users Virtual MIMO and random beamforming –Increased system throughput

48. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 48 Cyclic Delay Transmission Frequency diversity achieved by FEC !

49. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 49 Space-Frequency Coding (SFC) Subcarrier 1Subcarrier 2 Ant 1 S(1)-S*(2) Ant 2 S(2)S*(1)

50. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 50 Switched-beam Beamforming + CDT/STBC Downlink transmission (Localized) Two eigenbeams (switched beams) transmitted at a time Data transmitted at one beam cyclic delayed version at another beam Achieve diversity and beamforming gain simultaneously CPE 1 Base

51. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 51 Interference Avoidance to Primary Users (PUs) Beamforming to avoid interference to PU –Use geographic knowledge of the primary user –Frequency planning CPE2 uses frequencies unoccupied by PU for communication Frequencies occupied by PU can be allocated to CPE1& CPE3

52. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 52 Delay Spread Reduction For channels with large delays –Repeater applications –Large cell size Solutions –Basic transmit beamforming (BTB) and advanced transmit beamforming (ATB) –Exploits spatial domain as different reflectors usually have different direction of departure (DOD) w.r.t. transmitter

53. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 53 Basic Transmit Beamforming (BTB) In DL, beamformer only directs transmission to the path/cluster with the strongest gain per user. Other directions are suppressed – reducing overall delay Frequency domain beamforming for each user (subchannel) – different directions

54. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 54 Advanced Transmit Beamforming (ATB) More than one beam transmitted per user in DL. If overall channel delay in excess of CP length, relatively delay of each beam may be adjusted to suit CP length. Can also be used to increase delay diversity A repeater behaves like an additional delay path with known direction – can use ATB to mitigate extra delay introduced by repeater.

55. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 55 ATB By adjusting timings D1 and D2, the overall delay of the channel can be changed. Reflector 1 Or repeater Reflector 2 Or repeater CPE Local scatters Beam 1 Beam 2 Delay 1 T 1 = τ 1 + D 1 Delay 2 T 2 = τ 2 + D 2 Overall Delay |T1-T2| +δ Pre-alignment & beamforming Stream 1 Stream 2

56. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 56 ATB: Channel Shortening and Lengthening

57. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 57 Virtual MIMO Uplink Multiple Antennas at BS and single antenna at each CPE Multiple CPEs share the same physical channel Spectrum efficiency increase linearly with CPE number if the CPE number is less than the number of BS antennas CPE 1 CPE 2 Base

58. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 58 Random Beamforming for MIMO Randomly pick up one beamforming matrix, it will hit somebody if there are many users within the cell! When the user is hit and scheduled, it seems that the BS knows the CSI of that user. Equal rate for all data streams using TPC Multiuser diversity gain BS

59. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 59 Random Beamforming for MIMO PilotDataPilotData … PpPp S p (n) x p (n) H1H1 Q1HQ1H u 1 (n) y 1 (n) z 1 (n)...... HMHM QMHQMH u M (n) y M (n) z M (n) PpPp S k (n)x k (n) HkHk QkHQkH u k (n) y k (n) z k (n) Pilot mode Data mode: User k is scheduled for transmission DFE

60. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 60 Random Beamforming: Pilot Mode Random beamformer generator BS CPE Training sequences Random beamformer ZF-GDFE receiver SINR measurement SINR calibration using power control Feedback requested rate & power allocations Proportional fairness scheduling

61. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 61 Sectorization Each cell is divided into multiple sectors Each sector is covered by one sector or more antennas Frequency reuse 1 except sector edge users Inter-sector diversity is achieved for sector edge users using CDT or STBC If designed properly, sector-specific scrambling codes can be used to achieve frequency diversity

62. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 62 Inter-Sector Diversity

63. doc.: IEEE 802.22-05/0094r1 Submission November 2005 Ying-Chang Liang, Institute for Infocomm ResearchSlide 63 References [1] IEEE 802.22 Wireless RAN, Functional Requirements for the 802.22 WRAN Standard, IEEE 802.22-05/0007r46, October 2005. [2] IEEE 802.16-2004. IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems, 2004. [3] ETSI EN300 744 V1.5.1 (2004-11) Digital Video Broadcasting (DVB): Framing structure, channel coding and modulation for digital terrestrial television