January 2004 doc IEEE 802 11 04002 r

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January 2004 doc. : IEEE 802. 11 -04/002 r 2 Considerations for STS for

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Considerations for STS for MIMO-OFDM Seigo Nakao, Yoshiharu Doi, snakao@gf. hm. rd. sanyo. co. jp doi@gf. hm. rd. sanyo. co. jp SANYO Electric Co. , Ltd. Japan Presented by Jon W. Rosdahl Submission Slide 1 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Contents • Background &

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Contents • Background & motivation • Proposal for new STS – STS example for 2 TX mode – STS example for 3 TX mode • Conclusion Submission Slide 2 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Background: Issues for STS

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Background: Issues for STS TX 1 STS DATA 1 TX 2 STS DATA 2 TX 3 STS DATA 2 The receive signal power of STS should be the same as that of DATA for ideal AGC control. Submission Slide 3 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Legacy STS Questions •

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Legacy STS Questions • Is only one legacy (. 11 a) STS enough for MIMO-OFDM? – Assertion: Legacy STS (from. 11 a) is not preferable for MIMO applications (with more than one Tx antenna). • Assuming legacy STS is not sufficient, what STSs are preferable? Submission Slide 4 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Postulate: • Each MIMO

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Postulate: • Each MIMO TX antenna should have it’s own STS • The cross-correlation of 1 STS cycle for any pair of STSs should be 0 for – Easy synchronization, – Good frequency offset estimation, and – Optimum AGC implementation. Submission Slide 5 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Signal Calculation Assumptions h

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Signal Calculation Assumptions h 11 S 1(t) h 21 X 1(t) = h 11 S 1(t)+h 21 S 2(t)+n 1(t) h 12 h 22 S 2(t) X 2(t) = h 12 S 1(t)+h 22 S 2(t)+n 2(t) S|Si(t)|2 = SSi(t)S*i(t) = 1, (i=1, 2), SS*1(t)S 2(t) = Xc, SS*i(t)nj(t) = 0 (i=1, 2 j=1, 2), nj(t) << 1 i. e. |nj(t)|2 ~= 0 (j=1, 2) S means the sum of 1 STS cycle. (i. e. from t=0 to t=15) Submission Slide 6 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of STS Calculating the receiving signal power of 1 STS cycle (16 FFT points). S|X 1(t)|2 =SX 1(t)X*1(t) =S{h 11 S 1(t)+h 21 S 2(t)+n 1(t)}{h*11 S*1(t)+h*21 S*2(t)+n*1(t)} =h 11 h*11 SS 1(t)S*1(t) + h 21 h*21 SS 2(t)S*2(t) + h 11 h*21 SS 1(t)S*2(t) +h*11 h 21 SS*1(t)S 2(t) + h 11 SS 1(t)n*1(t) + h 21 SS 2(t)n*1(t) + h*11 SS*1(t)n 1(t) + h*21 SS*2(t)n 1(t) + Sn 1(t)n*1(t) Here, SS*1(t)S 2(t) = Xc, SS*i(t)nj(t) = 0 and |nj(t)|2 ~= 0, so S|X 1(t)|2 =|h 11|2+|h 21|2+h 11 h*21 X*c+h*11 h 21 Xc =|h 11|2+|h 21|2+2 Re[h 11 h*21 X*c] Submission Slide 7 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of STS If STS of TX 1 is the same as that of TX 2 (i. e. S 1(t)=S 2(t)), Xc = 1. The receiving signal power of 1 STS cycle is, |h 11|2+|h 21|2+2 Re[h 11 h*21]. (/ 16 FFT points) When h 11 = –h 21, AGC can’t work correctly because the receiving signal power is 0. However, the receiving power of DATA sequence is |h 11|2+|h 21|2. (/ 16 FFT points) because Xc = 0 in the DATA sequence. Therefore New STS is necessary. Submission Slide 8 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Receiving Signal Power of STS In general, if the |Xc| is not small, the receiving power difference between STS and DATA (i. e. 2 Re[h 11 h*21 Xc]) becomes large depending on propagation situations. Therefore the optimum AGC is difficult. Xc should be 0 in 1 STS cycle. (i. e. the cross correlation between transmitted STSs should be small) Submission Slide 9 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Cross-correlation of X 1

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Cross-correlation of X 1 and S 1 When finding synchronization symbol timing or estimating frequency offset of signals from Ant 1, the calculation for cross-correlation of X 1(t) and S 1(t) is necessary. ( i. e. SX 1(t)S*1(t) / sqrt{S|X 1(t)|2}sqrt{S|S 1(t)|2}) SX 1(t)S*1(t) / sqrt{S|X 1(t)|2}sqrt{S|S 1(t)|2} =S{(h 11 S 1(t)+h 21 S 2(t)+n 1(t)}S*1(t) / sqrt{S|X 1(t)|2} =S{(h 11 S 1(t)S*1(t)+h 21 S 2(t)S*1(t)+S*1(t)n 1(t)} / sqrt{S|X 1(t)|2} ={h 11 SS 1(t)S*1(t)+h 21 SS*1(t)S 2(t)+SS*1(t)n 1(t)}/sqrt{S|X 1(t)|2} =(h 11 + h 21 Xc) / sqrt{|h 11|2+|h 21|2+2 Re{h 11 h*21 Xc}} In case h 11 = –h 21 Xc, the cross-correlation of X 1(t) and S 1(t) becomes 0. Thus, if Xc is small (preferably Xc = 0), then there is no case when the (h 11 + h 21 Xc) term becomes 0. Submission Slide 10 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Some Preamble & Frame

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Some Preamble & Frame Format combinations: • Single STS and single LTS (legacy) • Multiple Simultaneous STS and LTS • Multiple Simultaneous STS and staggered LTS Submission Slide 11 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX, Single STS

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX, Single STS example Type 1 (single STS) TX 1 STS LTS Signal TX 2 Submission DATA 1 LTS Slide 12 Signal DATA 2 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX, Overlapped STS

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX, Overlapped STS examples Type 2 (overlapped STS and LTS) TX 1 STS LTS Signal DATA 1 TX 2 STS LTS Signal DATA 2 Type 3 (overlapped STS, staggered LTS) TX 1 STS TX 2 STS Submission LTS Signal DATA 1 LTS Slide 13 Signal DATA 2 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Proposal for New STSs

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Proposal for New STSs • Each TX antenna should have an unique STS. • The cross-correlations of one STS cycle (i. e. 16 FFT points) for STS pair should be 0. TX 1 STS 1 DATA 1 TX 2 STS 2 DATA 2 TX 3 STS 3 DATA 2 These STSs can be applied for all types of frame format. (e. g. overlapped LTSs, non-overlapped LTSs, overlapped Signals, non-overlapped Signals) Submission Slide 14 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 How to find new

January 2004 doc. : IEEE 802. 11 -04/002 r 2 How to find new STSs Generally, the cross-correlation of u(t) and v(t) is defined as Where, U(f) and V(f) are the Fourier transform of u(t) and v(t), respectively. Therefore, the cross-correlation of following STSs is always 0. • STS 1 which consists of 6 subcarriers of legacy STS. (e. g. – 24, – 4, 8, 12, 16, 20) • STS 2 which consists of 6 different subcarriers. (e. g. – 20, – 16, – 12, – 8, 4, 24) Moreover, both STS 1 and STS 2 have the same cycle length as the Legacy. 11 a STS (16 FFT points). Submission Slide 15 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX and 3

January 2004 doc. : IEEE 802. 11 -04/002 r 2 2 TX and 3 TX STS Examples Submission Slide 16 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Example of New STS

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Example of New STS for 2 TX STS 1– 26, 26 = sqrt(13/3){0, 0, – 1–j, 0, 0, 0, 0, 0, – 1–j, 0, 0, 0, – 1–j, 0, 0, 0, 1+j, 0, 0, 0, 0} STS 2– 26, 26 = sqrt(13/3){0, 0, 0, 1+j, 0, 0, 0, 0, – 1–j, 0, 0, 0, 0, 0, – 1–j, 0, 0} Cross-correlation between STS 1 and STS 2 is 0. Cross-correlation between legacy STS and both STS 1 and STS 2 is non-zero but small enough to help identify legacy and 11 n devices. Submission Slide 17 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of STS 1 for 2 TX FFT point number Submission Slide 18 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of STS 2 for 2 TX FFT point number Submission Slide 19 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Example of New STS

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Example of New STS for 3 TX STS 1– 26, 26 = sqrt(13/2){0, 0, – 1–j, 0, 0, 0, 0, – 1– j, 0, 0, 0, 1+j, 0, 0, – 1–j, 0, 0, 0, 0, 0, 0} STS 2– 26, 26 = sqrt(13/2){0, 0, 0, 0, 1+j, 0, 0, 0, 0, 0, – 1–j, 0, 0, 0, 1+j, 0, 0, 0, 1+j, 0, 0} STS 3– 26, 26 = sqrt(13/2){0, 0, 0, – 1–j, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1+j, 0, 0, 0, 0} Submission Slide 20 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of STS 1 for 3 TX FFT point number Submission Slide 21 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of STS 2 for 3 TX FFT point number Submission Slide 22 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Amplitude Time domain of STS 3 for 3 TX FFT point number Submission Slide 23 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Conclusion • New STSs

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Conclusion • New STSs are necessary for MIMO-OFDM. • Each TX antenna should have an unique STS. • The cross-correlation of 1 STS cycle for any pair of STSs should be 0. • Appropriate STSs are possible – Preliminary examples of new STSs were shown. • STS usage should be included in Comparison Criteria considerations Submission Slide 24 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Additional investigation • Work

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Additional investigation • Work is in progress to find new STSs which meet this criteria and also provide good autocorrelation performance. Submission Slide 25 Seigo Nakao, Yoshiharu Doi (SANYO)

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Questions? Submission Slide 26

January 2004 doc. : IEEE 802. 11 -04/002 r 2 Questions? Submission Slide 26 Seigo Nakao, Yoshiharu Doi (SANYO)