EVM Definition Analysis: Supporting Document for C80216m10/0616 IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE S802.16m-10/0689 Date Submitted: 2010-05-05 Source: Rongzhen Yan, Yang-seok Choi Tom Harel, Hujun Yin, Amir Rubin, Jin Fu and Rui Huang Intel Corporation E-mail: Rongzhen.Yang@intel.com Venue:. RE: Comments on P802.16m/D5 Purpose: EVM definition and requirement for IEEE 802.16m Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. 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EVM Definition/Requirement Background • Current 16m text of EVM: reference to 802.16-2009 section 8.1.8.2.3: – It is EVM definition and limitation for WirelessMAN-SC, not for OFDM/OFDMA; – The definition don’t consider the impaction of EVM noise on modulated tone and unmodulated tones; • 16e EVM Definition/Requirement in 8.4.13.3: – The limitation in Table 544 was derived from very simply rule, the impaction of EVM noise for capacity loss is not studied; – The EVM noise on modulated and un-modulated tones, are evaluated and limited separately. It is not appreciated because EVM noise on un-moudulated will be changed according to the ratio of occupied bandwidth for modulated tones; – For highest modulation in uplink, 64 QAM, is low possibility to used in full Tx power, so, the test condition of power reduction comparing to the maximum Tx power, which is not addressed; Agenda • EVM Noise Study and Equation Derivation • EVM Basic Requirements by LLS Result • Power Reduction Study for Uplink EVM Test EVM Noise Study • Rapp is selected as PA model for distortion study, parameters setting: • • • Saturation Power: 31 dBm Maximum V = 3.3 v Rapp P = 2 or 3 Rapp Example: Vsat = 3.3 v 4 3 V 1 in Vsat 2 2P 1 2P Rapp P=2 Rapp P=3 Rapp P=30 1 Output Voltage Vout Vin 0 -1 -2 • Permutation for the study: – 16m Uplink CRU – 16m Uplink DRU -3 -4 -5 -4 -3 -2 -1 0 Input Voltage 1 2 3 4 5 EVM Noise Distribution • EVM Noise will be distributed into Modulated Tones Un-modulated Tones Guard Band OOBE -50 • EVM Noise Definition: LP ErrorRMS 2 Nf 2 2 0 j 1 kS 0 I (i, j, k ) LP i 1 j 1 kS 0 -60 -70 -80 -90 – On Modulated Tones (16e Equation) I (i, j, k ) I (i, j, k ) Q(i, j, k ) Q (i, j, k ) 1 Nf min spectrum average spectrum max-hold spectrum FCC mask -40 xx(f) [dBm/Hz] – – – – Spectral density and masks. TX power = 29.18 -30 2 Q0 (i, j, k ) 2 -100 -110 -30 -20 -10 0 10 Frequency [MHz] – On Un-Modulated tones (16e Equation) I (i, j, k ) LP ErrorRMS 2 1 Nf Nf i 1 j 1 kSu LP I (i, j, k ) j 1 kS 0 2 Q (i , j , k ) 2 2 Q0 (i, j, k ) 2 – Sum of the in-band EVM noise: ErrorRMS ErrorRMS ( Modulated ) ErrorRMS (Un mod ulated ) 2 2 2 – EVM Noise in OOB is limited by spectral mask, don’t need to be limited by EVM requirement. 20 30 EVM Noise Study – Case 1: Uplink CRU • 16m Uplink CRU example: one subband assigned @ subband #2, other parameters: • • • • Rapp P = 2 Noise on modulated tones and un-modulated tones is studied EVM: SUM = -9.56, Modulated = -11.64, Un-Modulated = -13.75 EVM noise feature on modulated tones, AWGN can be assumed: 1000 1000 800 800 600 600 400 400 200 200 0 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 Real Part EVM on Modulated Tones 0.6 0 -1 0.8 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 Imagine Part EVM on Modulated Tones 0.6 0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 Real Part EVM on UnModulated Tones - Adjacent Subband 0.8 EVM noise feature on un-modulated tones, obviously, no white: EVM Noise Power Distribution for Localized Allocation 16m LLRU - 1000 Symbols Statistics - Rapp2 0.09 3000 0.08 2500 0.07 2000 0.06 EVM Noise Per Tone Distribution EVM Noise Average per Subband 0.05 Histogram Normalized EVM Noise Power • 16m LLRU - 1000 Symbols Statistics - Rapp2 1200 Histogram Histogram 16m LLRU - 1000 Symbols Statistics - Rapp2 1200 0.04 1500 1000 0.03 0.02 500 0.01 0 0 100 200 300 400 500 Tone Index 600 700 800 900 0 -0.8 EVM Noise Study – Case 1, Cont. • 100% load is assumed and each AMS has been assigned for one subband crossing the whole band. The generated EVM noise is accumulated with same weight: EVM Noise Power Distribution for Localized Allocation, 100% Load 0.12 Normalized EVM Noise Power 0.11 0.1 0.09 EVM Noise Per Tone Distribution EVM Noise Average per Subband 0.08 0.07 0.06 0.05 0 100 200 300 400 500 Tone Index 600 700 800 900 • So, the accumulated EVM noise from all AMS still can be assumed as AWGN. EVM Noise Study – Case 1, Cont. • Different rates of modulate vs. un-modulated are studied, and results are summarized: Assigned Band (subband) Offset (subband) EVM (Modulated) EVM (Unmodulated) Mod vs. Un-Mod EVM Noise Ratio per Subcarrier (dB) 1 1 -11.6404 -13.7560 12.52 2 1 -11.6039 -14.2465 10.42 4 1 -11.5718 -14.9812 8.18 8 1 -11.5736 -16.9309 2.34 12 0 -11.5538 N/A N/A 1 6 -11.6685 -13.8978 13.20 2 5 -11.6438 -13.8856 10.03 4 4 -11.5486 -13.9439 7.17 8 2 -11.5624 -16.6926 2.12 • Obviously, we can see that: • EVM noise on un-modulated tones cannot be ignored; • But, the limitation by 16e un-modulated equation is not suitable: it will be changed greatly due to assigned band percentage of whole band. EVM Noise Study – Case 2: Uplink DRU • 16m Uplink Distributed example: • • • • 4 DLRU assigned, Tx Power = ~27.25 dBm, EVM = ~15.4 dB (sum) Rapp P = 2 Noise on modulated tones and un-modulated tones is studied EVM: SUM = -16.98, Modulated = -23.43, UnModulated = -18.10 Obviously, EVM noise on modulated tones can be assumed as AWGN: 700 700 600 600 500 500 400 400 300 300 200 200 100 100 0 -0.4 -0.3 -0.2 -0.1 0 0.1 Real Part EVM on UnModulated Tones 0.2 0 -0.4 0.3 -0.3 -0.2 -0.1 0 0.1 Imagine Part EVM on UnModulated Tones 0.2 0.3 Also, the EVM noise on un-modulated tones can be assumed as AWGN: 16m LLRU - 1000 Symbols Statistics - Rapp2 16m LLRU - 1000 Symbols Statistics - Rapp2 1800 1800 1600 1600 1400 1400 1200 1200 Histogram Histogram • 16m DLRU - 500 Symbols Statistics - Rapp2 800 Histogram Histogram 16m DLRU - 500 Symbols Statistics - Rapp2 800 1000 800 1000 800 600 600 400 400 200 200 0 -0.4 -0.3 -0.2 -0.1 0 0.1 Real Part EVM on UnModulated Tones 0.2 0.3 0 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 Imagine Part EVM on UnModulated Tones 0.3 0.4 EVM Noise Study – Case 2, Cont. • Different rates of modulate vs. un-modulated are studied, and results are summarized: Assigned DLRU Num. EVM (Modulated) EVM (Unmodulated) Mod vs. UnMod EVM Noise Ratio per Subcarrier (dB) 1 -20.7584 -18.0257 13.99 2 -23.0256 -18.2187 8.81 4 -23.5273 -18.1345 5.02 8 -23.4201 -18.3091 1.88 16 -21.3967 -19.1258 0.74 32 -18.9053 -21.9739 0.05 48 -17.2001 N/A N/A • Obviously, we can see that: • Also, EVM noise on un-modulated tones cannot be ignored: even higher than EVM noise on modulated tones. • But, the limitation by 16e un-modulated equation is not suitable: it will be changed greatly due to assigned band percentage of whole band. • Summary: EVM Noise Study Summary and EVM Equation Derivation – AWGN assumption is acceptable for EVM noise on both modulated tones and unmodulated tones; – EVM noise on un-modulated tones cannot be ignored. • So, we set the modeling assumptions: • • Total EVM noise: Mt = Mm + Mum Mm is the total EVM noise on modulated tones Mum is the total EVM noise on un-modulated tones For K numbers of AMS are assigned for 1/K resource of total available band with same permutation (localized or distributed); All AMS has same EVM values and similar received RSS at ABS side. We can get total capacity: K CTotal i 1 i S i, j B log 1 s 2 M i , j N jBK ( i ) is the AMS index, j is subcarrier belong to AMS i bandwidth BK (i ) S i, j is received signaling strength M i, j is EVM noise strength N is all other noise in the receiver (exclude EVM noise) Bs is the bandwidth of one subcarrier Here, we assume EVM noise generated by all AMS are same feature, we can get: M (i, j ) Mm M um ( M m M um ) Mt ( K 1) B/K B ( K 1) / K B/K B/K and, we assume the received signaling strength is same: S i, j S B S S B log 2 1 CTotal log 2 1 M M t t i 1 K N N B/K B/K K If 5% throughput loss is assumed because of EVM noise, we can get: S S 0.95 B log 2 1 B log 2 1 Mt N N B/K 1 0.95 Mt S N 1 1 S B / K N S because S B / K is the total reference signal power on mod ulated tones, we can get suitable EVM definition as : EVM Lin EVM Noise on Modulated Un mod ulated Tones Re ference Signal Power on Modulated Tones And we can get 5% throughput loss condition, EVM vs. working SNR relationship: 1 1 0.95 EVM Re quired 10 log 10 1 SNRLin 1 SNR Lin EVM Curve for 5% Throughput Loss -5 -10 EVM Requirement (dB) -15 -20 -25 -30 -35 -5 0 5 10 15 Working Instantaneous SNR (dB) 20 25 30 EVM Equation Definition • By the study, we can define the EVM noise equation by the sum of EVM noise in modulated and un-modulated tones (same naming style of 16e): 1 EVM 10 log 10 N f I ( i , j , k ) I ( i , j , k ) Q ( i , j , k ) Q ( i , j , k ) LS Nf i 1 j 1 kS Su 2 2 0 I (i, j, k ) LP j 1 kS 0 0 2 Q0 (i, j, k ) 2 Where: N f is the number of frames for the measurement; LS is the number of symbols used for the measurement; S is the group of modulated data subcarriers; S u is the group of un-modulated data subcarriers. It includes all subcarriers in the range 0 … Nused – 1, except the DC and the modulated subcarriers (in S); I 0 (i, j, k ), Q0 (i, j, k ) denotes the ideal symbol point in the complex plane. It is set as (0, 0) in the un-modulated data subcarriers. I (i, j, k ), Q(i, j, k ) denotes the observed point of the i-th frame, j-th OFDMA symbol, k-th subcarrier in the complex plane; Agenda • EVM Noise Study and Equation Derivation • EVM Basic Requirements by LLS Result • Power Reduction Study for Uplink EVM Test Uplink LLS Simulation Setting For EVM Requirements, we needs to get the working SNR of each modulation, so we perform uplink LLS for: • Channel Model: eITU-PedB 3km/h • Uplink Data Transmission Configuration: • • • • Single stream SIMO: 1 Tx, 2 Rx (spacing 0.5 wavelength), MRC receiver. Channel Estimation: MMSE Permutation: 16m DRU Data Burst Size: 3 subframes x 4 DRUs • HARQ: disabled Uplink LLS for 1x2, eITU-PedB, DRU, QPSK 10 10 10 eITU-PedB, 3km/h, 16m UL LLS, QPSK, DRU 0 CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, -1 R=0.0992 R=0.1071 R=0.123 R=0.1429 R=0.1587 R=0.1746 R=0.1984 R=0.2262 R=0.254 R=0.2817 R=0.3175 R=0.3571 R=0.3968 R=0.4524 R=0.5079 R=0.5754 R=0.6508 R=0.7183 -2 -10 -5 0 5 10 15 20 • The maximum SNR of QPSK at 30% PER is ~6 dB. • The EVM requirement should be -16 dB Uplink LLS for 1x2, eITU-PedB, DRU, 16QAM and 64QAM 10 10 10 eITU-PedB, 3km/h, 16m UL LLS, 16QAM and 64QAM, DRU 0 CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, -1 R=0.4067, R=0.4623, R=0.5198, R=0.5774, R=0.6508, R=0.4868, R=0.5503, R=0.6243, R=0.6984, R=0.7937, R=0.8677, Modul 4 Modul 4 Modul 4 Modul 4 Modul 4 Modul 6 Modul 6 Modul 6 Modul 6 Modul 6 Modul 6 -2 0 5 10 15 20 25 30 35 40 • The maximum SNR (30% PER) of 16QAM is 11 dB, so the EVM requirement is -19 dB • The midpoint of 64QAM is 17dB, so the EVM requirement is -24 dB Downlink LLS Simulation Setting Basic settings to derive the downlink working SNR range: • Channel Model: eITU-PedB 3km/h • Downlink Data Transmission Configuration: • • • • 2 Tx, 2 Rx, SFBC, Rate = 1 Channel Estimation: MMSE Permutation: 16m DRU Data Burst Size: 4 subframes x 4 DRUs • HARQ: disabled DL LLS for 2x2 SFBC, eITU-PedB, DRU, QPSK 10 10 10 0 eITU-PedB, 3km/h, 16m Downlink LLS, SFBC 2x2, QPSK, DLRU CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, -1 -2 -10 -5 0 5 R=0.0651 R=0.0703 R=0.0807 R=0.0938 R=0.1042 R=0.1146 R=0.1302 R=0.1484 R=0.1667 R=0.1849 R=0.2083 R=0.2344 R=0.2604 R=0.2969 R=0.3333 R=0.375 R=0.4271 R=0.4688 10 • The maximum SNR of QPSK at 30% PER is ~0 dB. • The EVM requirement should be -11 dB DL LLS for 2x2 SFBC, eITU-PedB, DRU, 16QAM and 64QAM eITU-PedB, 3km/h, 2x2 SFBC, 16m Downlink LLS, 16QAM and 64QAM, DRU 0 10 10 10 CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, CTC, -1 R=0.2656, R=0.3021, R=0.3438, R=0.3854, R=0.4271, R=0.3194, R=0.4097, R=0.4583, R=0.5208, Modul 4 Modul 4 Modul 4 Modul 4 Modul 4 Modul 6 Modul 6 Modul 6 Modul 6 -2 0 5 10 15 20 25 30 • The maximum SNR (30% PER) of 16QAM is 4.5 dB, so the EVM requirement is -15 dB • The maximum SNR (30% PER) of 64QAM is 11dB, so the EVM requirement is -20 dB EVM Requirements Summary • LLS Results Summary: – Uplink EVM Requirement for QPSK, 16 QAM, 64 QAM (1x2 SIMO) is: -16, -19, -24 dB – Downlink EVM Requirement for QPSK, 16 QAM, 64 QAM (2x2 SFBC) is: -11, -15, -20 dB • Recommendation: – Because downlink (ABS) implementation is less sensitive for higher EVM requirement, for the simplification, we can set downlink EVM requirement as same as uplink, for higher downlink performance. Agenda • EVM Noise Study and Equation Derivation • EVM Basic Requirements by LLS Result • Power Reduction Study for Uplink EVM Test Modulation vs. Tx Power Study • In 16m uplink transmission, because of uplink power control, the modulation is related to uplink Tx power level. • Uplink SLS Scenario for evaluation: IEEE 802.16m PCLA DG evaluation setting: Parameter Value Parameter Value Carrier frequency (GHz) 2.5 GHz Site to site distance (m) 500m 10 MHz Channel eITU-Ped B, 3km/h Reuse factor 1 Max power in MS (dBm) 23dBm Frame duration (Preamble+DL+UL) 5ms Antenna Config 1x2 SIMO Number of OFDM symbols in UL Frame 18 HARQ On (Max retrans: 4/Sync) FFT size (tone) 1024 Target PER 0.2 Useful tone 864 Link to system mapping RBIR Number of LRU 48 Scheduler type PF LRU type DRU Resource Assignment Block 8 LRU Number of users per sector 10 Penetration loss (dB) 20dB CMIMO support no Control Overhead 0 for SE calculation (not defined yet) System bandwidth (MHz) Tx Power vs. Modulation CDF Tx power distribution for different values of for all modulations 1 0.9 0.9 0.8 0.5 0.4 0.7 0.5 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 -80 -60 -20 0 20 Tx power (in dBm) Tx power distribution for different values of for QPSK -40 0 -80 40 1 0.9 0.9 =0 =0.2 =0.4 =0.6 =0.8 =1 =1.2 =1.4 0.6 0.5 0.4 -20 0 Tx power (in dBm) 20 40 0.7 =0.2 =0.4 =0.6 =0.8 =1 =1.2 =1.4 0.6 0.5 0.4 0.3 0.3 0.2 0.2 0.1 0 -80 -40 0.8 CDF 0.7 -60 Tx power distribution for different values of for 64QAM 1 0.8 =0 =0.2 =0.4 =0.6 =0.8 =1 =1.2 =1.4 0.6 CDF 0.6 CDF 0.8 =0 =0.2 =0.4 =0.6 =0.8 =1 =1.2 =1.4 0.7 CDF Tx power distribution for different values of for 16QAM 1 0.1 -60 -40 -20 0 Tx power (in dBm) 20 40 0 -70 -60 -50 -40 -30 -20 Tx power (in dBm) -10 0 10 20 30 Typical gamma value selection • According to the all gamma value results, we can get: • • • • QPSK/16QAM has high percentage of full power transmission; the test under full Tx power is necessary; 64 QAM has very low percentage of full power transmission, which is potential test under power reduction (vs. full power) But how much power reduction for 64 QAM is suitable? Different gamma values (as control parameter of power control) will produce different IoT distributions: IoT Distribution for different values of 1 gamma IoT mean (in dB) IoT Std (in dB) 0.0 5.5069 1.0959 0.2 5.7500 1.0982 0.4 6.6577 1.0503 0.6 7.7271 1.0501 0.8 9.0305 1.0654 0.2 1.0 10.6258 1.2287 0.1 1.2 12.3736 1.4547 0 1.4 13.5477 1.5246 0.9 0.8 0.7 =0 =0.2 =0.4 =0.6 =0.8 =1.0 =1.2 =1.4 CDF 0.6 0.5 0.4 0.3 0 5 10 IoT (in dB) 15 20 Power Reduction of 64 QAM Study • Considering the performance and IoT requirement (<10 dB), the Gamma value 0.4 ~ 0.8 will be typically adopted values for the power reduction study. • We study the CDF 5% power of 64 QAM Tx power distribution: gamma IoT mean (in dB) Tx Power @ 5% CDF (dBm) 0.2 5.7500 7.8 0.4 6.6577 13.3 0.6 7.7271 17.9 0.8 9.0305 19.7 1.0 10.6258 21.9 1.2 12.3736 23.0 1.4 13.5477 23.0 • If we consider the average power reduction of gamma value 0.4~0.8, it will be 6 dB; • If we consider the maximum gamma value to control IoT less than 10 dB, it will be 2~3 dB; • So, we set it as 3 dB as trade off value. Summary of Minimum 16m EVM Requirement • Downlink EVM Requirement: Unit Parameter QPSK or BPSK 16QAM 64QAM • dB dB dB Required EVM Level (dB) -16 -19 -24 Uplink EVM Requirement: Unit Parameter QPSK or BPSK 16QAM 64QAM dB dB dB Required EVM Level (dB) -16 -19 -24 Power Reduction (dB) 0 0 3