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doc.: IEEE 802.11-15/0330r5
Submission
OFDMA Numerology and StructureMay 2015
Slide 1
Date: 2015-05-13
Authors: Name Affiliation Address Phone email
Shahrnaz Azizi
Intel
2200 Mission College Blvd, Santa Clara, CA 95054
Eldad Perahia [email protected]
Robert Stacey 2111 NE 25th Ave, Hillsboro
OR 97124, USA +1-503-724-893 [email protected]
Po-Kai Huang [email protected]
Qinghua Li [email protected]
Xiaogang Chen [email protected]
Chittabrata Ghosh [email protected]
Rongzhen Yang [email protected]
Laurent cariou [email protected]
Wookbong Lee
LG Electronics
19, Yangjae-daero 11gil, Seocho-gu, Seoul 137-130,
Korea [email protected]
Kiseon Ryu [email protected]
Jinyoung Chun [email protected]
Jinsoo Choi [email protected]
Jeongki Kim [email protected]
Giwon Park [email protected]
Dongguk Lim [email protected]
Suhwook Kim [email protected]
Eunsung Park [email protected]
HanGyu Cho [email protected]
1 S.Azizi, Intel, J. Choi, LGE
doc.: IEEE 802.11-15/0330r5
Submission Slide 2
Authors (continued)Name Affiliation Address Phone email
Ron Porat
Broadcom
Matthew Fischer [email protected]
Sriram Venkateswaran
Tu Nguyen
Vinko Erceg
Lei Wang
Marvell
5488 Marvell Lane, Santa Clara, CA, 95054
858-205-7286 [email protected]
Hongyuan Zhang
Yakun Sun [email protected]
Liwen Chu [email protected]
Jinjing Jiang [email protected]
Yan Zhang [email protected]
Rui Cao [email protected]
Sudhir Srinivasa [email protected]
Saga Tamhane [email protected]
Mao Yu [email protected]
Edward Au [email protected]
Hui-Ling Lu [email protected]
1
May 2015
S.Azizi, Intel, J. Choi, LGE
doc.: IEEE 802.11-15/0330r5
Submission Slide 3
Authors (continued)
James Yee
Mediatek
No. 1 Dusing 1st Road, Hsinchu, Taiwan
+886-3-567-0766 [email protected]
Alan Jauh [email protected]
Chingwa Hu [email protected]
Frank Hsu [email protected]
` 1 Thomas Pare
Mediatek USA
2860 Junction Ave, San Jose, CA 95134, USA
+1-408-526-1899 [email protected]
ChaoChun Wang [email protected]
James Wang [email protected]
Jianhan Liu [email protected]
Tianyu Wu [email protected]
Russell Huang [email protected]
` 1
Name Affiliation Address Phone email
1
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission Slide 4
Authors (continued)
Name Affiliation Address Phone email
Albert Van Zelst
Qualcomm
Straatweg 66-S Breukelen, 3621 BR Netherlands
Alfred Asterjadhi 5775 Morehouse Dr. San Diego, CA, USA
Bin Tian [email protected]
Carlos Aldana 1700 Technology Drive San
Jose, CA 95110, USA [email protected]
George Cherian 5775 Morehouse Dr. San
Diego, CA, USA
Gwendolyn Barriac [email protected]
Hemanth Sampath [email protected]
Menzo Wentink Straatweg 66-S Breukelen, 3621 BR Netherlands
Richard Van Nee [email protected]
Rolf De Vegt 1700 Technology Drive San
Jose, CA 95110, USA [email protected]
Sameer Vermani 5775 Morehouse Dr. San
Diego, CA, USA
Simone Merlin [email protected]
Tevfik Yucek 1700 Technology Drive San
Jose, CA 95110, USA
VK Jones [email protected]
Youhan Kim [email protected]
1
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission Slide 5
Authors (continued)
Name Affiliation Address Phone email
Phillip Barber
Huawei
The Lone Star State, TX [email protected]
Peter Loc [email protected]
Le Liu F1-17, Huawei Base, Bantian,
Shenzhen +86-18601656691 [email protected]
Jun Luo 5B-N8, No.2222 Xinjinqiao
Road, Pudong, Shanghai [email protected]
Yi Luo F1-17, Huawei Base, Bantian,
Shenzhen +86-18665891036 [email protected]
Yingpei Lin 5B-N8, No.2222 Xinjinqiao
Road, Pudong, Shanghai [email protected]
Jiyong Pang 5B-N8, No.2222 Xinjinqiao
Road, Pudong, Shanghai [email protected]
Zhigang Rong 10180 Telesis Court, Suite 365, San Diego, CA 92121
Rob Sun 303 Terry Fox, Suite 400 Kanata, Ottawa, Canada
David X. Yang F1-17, Huawei Base, Bantian,
Shenzhen [email protected]
Yunsong Yang 10180 Telesis Court, Suite 365, San Diego, CA 92121
Zhou Lan F1-17, Huawei Base, Bantian,
SHenzhen +86-18565826350 [email protected]
Junghoon Suh 303 Terry Fox, Suite 400 Kanata, Ottawa, Canada
Jiayin Zhang 5B-N8, No.2222 Xinjinqiao
Road, Pudong, Shanghai +86-18601656691 [email protected]
1 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission Slide 6
Authors (continued)Name Affiliation Address Phone email
Thomas Derham Orange
1 Yasushi Takatori
NTT
1-1 Hikari-no-oka, Yokosuka, Kanagawa 239-0847 Japan
Yasuhiko Inoue [email protected]
Yusuke Asai [email protected]
Koichi Ishihara [email protected]
Akira Kishida [email protected]
Akira Yamada
NTT DOCOMO
3-6, Hikarinooka, Yokosuka-shi, Kanagawa, 239-8536,
Japan [email protected]
m
Fujio Watanabe 3240 Hillview Ave, Palo
Alto, CA 94304 watanabe@docomoinnovatio
ns.com
Haralabos Papadopoulos
1 Fei Tong
Samsung
Innovation Park, Cambridge CB4 0DS (U.K.)
+44 1223 434633 [email protected]
Hyunjeong Kang Maetan 3-dong; Yongtong-Gu
Suwon; South Korea +82-31-279-9028 [email protected]
m
Kaushik Josiam 1301, E. Lookout Dr, Richardson TX 75070
(972) 761 7437 [email protected]
Mark Rison Innovation Park,
Cambridge CB4 0DS (U.K.) +44 1223 434600 [email protected]
Rakesh Taori 1301, E. Lookout Dr, Richardson TX 75070
(972) 761 7470 [email protected]
Sanghyun Chang Maetan 3-dong; Yongtong-Gu
Suwon; South Korea +82-10-8864-
1751 [email protected]
1 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission Slide 7
Authors (continued)
Name Affiliation Address Phone email
Bo Sun
ZTE
#9 Wuxingduan, Xifeng Rd Xian, China
Kaiying Lv [email protected]
Yonggang Fang
Ke Yao
Weimin Xing
Brian Hart Cisco Systems
170 W Tasman Dr, San Jose, CA 95134
Pooya Monajemi [email protected]
Joonsuk Kim
Apple
Aon Mujtaba [email protected]
Guoqing Li [email protected]
Eric Wong [email protected]
Chris Hartman [email protected]
1
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Outline
• Part-I– Motivation and background– Granularity of OFDMA resource units – Methodology – The proposed OFDMA resource units
• Part-II– Total usable tones– The proposed OFDMA structure and units
Slide 8 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Motivation and Background
• Based on the target use cases for 802.11ax, methods to improve the PHY efficiency such as OFDMA techniques have been proposed [1-3].– Time and space multiplexing have already been explored, with large number of users in dense
network WLAN systems need to explore multiplexing in frequency dimension – OFDMA can alleviate dense condition by maximizing user frequency selective multiplexing gain
• OFDMA can extract scheduling gains/selection diversity by scheduling users not in outage• Scheduling is easily done at AP where channel state information is available for MU-MIMO
• Contributions to 802.11ax have demonstrated that the existence of short data frames, at a low duty cycle in the network is a major factor for capping overall system throughput because such short packets can not be aggregated, and hence system suffers from MAC inefficiency and larger preamble overhead – Benefits of use of OFDMA in such scenarios was shown in [4]
• The 11ax specification framework has already defined UL and DL OFDMA as one of key 11ax MU features
Slide 9 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Discussions on the Granularity of OFDMA
• There is a tradeoff in obtaining OFDMA gain with complexity:– On frequency selective fading channels, smaller resource unit size provides higher gain, but at the
expense of larger feedback and signaling overhead• The size of the smallest resource unit should be selected relative to the channel coherence BW, which is quite
small especially for outdoor channels• The larger the number of users participating in the OFDMA scheduling the higher the gain, but this requires
larger scheduling/grouping complexity
• It was agreed to use 4x OFDM symbol duration in 11ax [5,6] as follows– 11ax has duration 12.8 us (without CP) based on a 256 FFT in 20 MHz, 512 FFT in 40 MHz, 1024
FFT in 80 MHz/80+80 MHz and 2048 FFT in 160 MHz– 4x symbol duration allows better granularity for OFDMA
• There are more number of tones in a given OFDMA bandwidth
Slide 10 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Selection of the Smallest OFDMA Resource Unit
S.Azizi, Intel, J. Choi, LGE Slide 11
• Simulations are performed to evaluate the spectrum efficiency vs. selection of the smallest OFDMA resource unit– Evaluation assumption is provided in the Appendix-A
• It is observed that spectrum efficiency starts to go down from the point of 2.5MHz RU size => The size of the smallest OFDMA resource unit needs to be smaller than 2.5MHz
102
103
104
1
1.5
2
2.5
3
3.5
RB SIZE(KHz)
Spectr
um
Eff
icie
ncy (
bps/H
z)
IEEE channel, 256-pt FFT
802.11 B NLOS
802.11 C NLOS
802.11 D NLOS
802.11 E NLOS
802.11 F NLOS
102
103
104
1
1.5
2
2.5
3
3.5
RB SIZE(KHz)
Spectr
um
Eff
icie
ncy (
bps/H
z)
IEEE channel, 256-pt FFT
ITU UMi NLOS
ITU UMi LOS
ITU UMi O2I NLOS
ITU UMa NLOS
ITU UMa LOS
Indoor channel, 256 FFT Outdoor channel, 256 FFT
Resource unit (RU) size Resource unit (RU) size
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Methodology (1/2)
• Simple design– Simple for implementation, testing, scheduling and sub-band feedback– Ability to create a limited number of modes and/or user assignments
• Reuse of existing design and hardware blocks of 802.11 alphabets
• Consistency– Consistent tone use for 2.4GHz and 5GHz bands– Consistent tone use for 20/40BW: easy feedback
• And consistent with 80MHz BW
• Good packing efficiency– Minimize leftover tones as well as proper guard/DC tone setting depending on BWs– Need to resolve following problems
• Very difficult to get 100% packing efficiency unless the resource unit is very small • Also inefficient to use only one small unit because number of pilots grows linearly
• Commonality between DL and UL resource unit– Minimize implementation, enabling a soft AP acting by a non-AP STA– Common design in terms of
• Resource granularity size• Pilot location and portion within a resource unit
– Pilot tone locations agnostic to BW and specific tone assignments
Slide 12 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Methodology (2/2)
• Based on the criteria mentioned in the previous slide, the following block sizes are considered – Reuse 26-tone block as defined in 11ah
• Mainly to support short/medium packets with many users
– Reuse 52-tone or 56-tone blocks from 11a/g or 11n/ac20MHz– Define a 10MHz block that would be similar to the existing 11n/ac 40MHz– Reuse 242- tone block as defined in 11ac
• Packing efficiency and number of leftover tones are analyzed for variety of combinations of the considered resource units on 20/40 and 80MHz bandwidth– The next slide proposes an OFDMA resource units that
• maximizes reuse of existing architecture while minimizes leftover tones• can be extended to 40/80 and 160 MHz
Slide 13 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
The Proposed Resource Units in 20MHz BW
• The proposed resource units have the following sizes– 26-tone with 2 pilots – 52-tone with 4 pilots– 106-tone with 4 pilots – 242-tone with 8 pilots
Slide 14 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Discussions on Choice of Resource Units
• The following lists the rationales behind the proposed resource units– The two smallest units of 26-tone and 52-tone have 2 pilots and 4 pilots, respectively, as in current
11ah 1MHz and 11a/g 20MHz with 24 data and 48 data for uniformity• Why picking 52-tone from 11a/g and not 56-tone from 11n/ac?
– 52-tone allows 256 QAM rate 5/6 with BCC while as in 11ac, 256 QAM rate 5/6 cannot be used in 56-tone – 52-tone is a multiple of 26-tone that allows a nice alignment among OFDMA assignments
– The third unit has 102 data plus 4 pilots. It is similar to legacy 11ac 40MHz, with a small change of replacing Ncol=18 with Ncol=17
• Appendix-B shows the results of simulation studies performed to select number of pilots (2 to 6) for the 102-data tone unit
– It can be seen that using only 2 pilot tones can lead to significant SNR losses, the performance with 4-6 pilots is similar with some loss for 3 pilots in certain cases
– The fourth unit of 242-tone is as in 11ac 80MHz with 8 pilot tones – There are reasonable number of pilots in each units
Slide 15 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Outline
• Part-I– Motivation and background– Granularity of OFDMA resource units – Methodology – The proposed OFDMA resource units
• Part-II– Total usable tones– The proposed OFDMA structure and units
Slide 16 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Number of Nulls at DC (1/2)• In 5GHz, 40ppm CFO spans ~3 tones on the left/right of DC
– Mainly 80/160MHz operation, as well as 40 and 20MHz operation• In 2.4GHz, 40ppm CFO spans 1 tone on the left/right of DC
– Mainly 20MHz operation• To avoid DC, ideally we need at least 7 nulls in 5GHz, and at least 3 nulls in 2.4GHz• DL OFDMA
– Rx LO Leakage + CFO is the major concern • UL OFDMA
– In UL OFDMA, the assumption is that STAs are required to synchronize the carrier frequency to the AP
• If carrier frequency compensation is done in digital domain, then Tx carrier leakage (Tx DC) of each UL OFDMA transmission may not be at the center of the transmitted OFDMA waveform, potentially interfering with data tones.
– In Uplink, carrier leaks from the received signals cannot be calibrated out by the AP receiver• Unknown frequencies, unknown magnitude
– Impact could be more severe than Rx DC in DL OFDMA, especially for narrow bandwidth OFDMA assignments near DC
Slide 17 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Number of Nulls at DC (2/2)• The impact of insufficient DC nulls depends on the bandwidth of resource units
• For wideband resource unit (like SU 20MHz), tone erasure of 1 or 2 tones cause negligible performance degradation (see Appendix-C)
• For small resource units like 26 tones, the degradation from insufficient DC nulls becomes significant (see Appendix-D)
• For 20MHz and 80MHz OFDMA tone plan (discussed in the following slides) – There is a straddling DC 26-tone allocation that is vulnerable to DC offset– There are also some leftover tones which can be assigned around DC to provide better protection for
the center 26-tone allocation• The proposed number of Nulls at DC
– For 20MHz, non-OFDMA has 3 DC nulls. OFDMA has 7 DC nulls to protect the central 26-tone allocation
– For 40MHz, 5 DC nulls • There is no center 26-tone allocation
– For 80MHz, OFDMA has 7 DC nulls and non-OFDMA has 5 DC nulls • There is a center 26-tone allocation in OFDMA tone plan
Slide 18 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Number of Guard Tones
• The payload design of 4x Symbol 20MHz is exactly 11ac 80 MHz down-clocked by 4, meaning (6,5) guard tones, 3 DC nulls, payload 234 data, 8 pilots (for the case where each user occupies the entire BW, DL/UL SU/MU-MIMO)– Spectral mask is 11ac 80MHz mask down-clocked by 4
• For 4x Symbol 40MHz bandwidth, the spectral mask is based on 11ac 80MHz mask down-clocked by 2, but with (12,11) guard tones – Note that we replaced (6,5)x2 with (12,11) for better symmetry in tone assignment
• For 4x Symbol 80MHz bandwidth, the spectral mask is based on 11ac 160MHz mask down-clocked by 2, but with (12,11) guard tones • Appendix-E shows that the 80MHz 11ax has lower OOBE than 11ac even if only (6,5) guards
are considered, hence the spectral mask is met with the proposed number of guard tones.
Slide 19 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Summary of NON-OFDMA Usable Tones
• DC Nulls– For 20MHz, non-OFDMA has 3 DC nulls– For 40MHz, 5 DC nulls – For 80MHz, non-OFDMA has 5 DC nulls
• 80MHz non-OFDMA tone plan– To maximize tone efficiency, non-OFDMA tone plan (SU and MU-MIMO) uses 996 with 5 DC
tones• 160MHz consists of two 80MHz tone plans
Slide 20 S.Azizi, Intel, J. Choi, LGE
May 2015
2.4 GHz / 5GHz 5GHz
20MHz 40 MHz 80 MHz 160 MHz/80MHz+80MHz
FFT size 256 512 1024 2x1024
Edge (6,5) (12,11) (12,11) (12,11)
Usable tones
242 484 996 2x996
doc.: IEEE 802.11-15/0330r5
Submission
Summary of Total Number of OFDMA Usable Tones
• DC Nulls– For 20MHz, OFDMA has 7 DC nulls.
• Appendix-D shows simulation results for the need of 7 DC nulls
– For 40MHz, 5 DC nulls – For 80MHz, OFDMA has 7 DC nulls.
• 160MHz OFDMA tone plan– Two replicas of 80MHz tone plans
• 996-tone (non-OFDMA tone plan in 80MHz) is used as a resource unit in 160MHz. • Combinations of 996+994, 994+996, and 994+ 994 are valid for 160MHz.
Slide 21
2.4 GHz / 5GHz 5GHz
20MHz 40 MHz 80 MHz 160 MHz/80MHz+80MHz
FFT size 256 512 1024 2x1024
Edge (6,5) (12,11) (12,11) (12,11)
Usable tones
Max 238 484 994 max 2x996
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Analysis on location of resource units (1/3)
K (assign-ments)
1x26 2x26 106 Further improve SST gain by moving location
3 1 0 2
• Have improvement for the 1x26 unit (one position => multiple positions available)
• Not much improvement for 106 (max a 26 tone shift ) units
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
K 1x26 2x26 106 Further improve SST gain by moving location
4 1 2 1 • Have improvement for the 1x26 unit• Not much improvement for other units
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
Possible assignments (e.g.)<Two 106-tone units assigned>
<One 102+P unit assigned>
* K = 5 with [1x26, 2x26, 106] = [3, 1, 1] => better than above for the 1x26 unit(3) in the fixed location
Fixed
Moving
Fixed
Moving
* Leftover tones are not addressed here
106
Slide 22 S.Azizi, Intel, J. Choi, LGE
• We check if “moving location” for units can further improve Sub-band Selective Transmission (SST) gain by providing more available positions than “fixed position”
• Note that to help with visualizing the analysis, we have illustrated 106-tone block as 4 units of 26-tone in the pictures below
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Analysis on location of resource units (2/3)
K 1x26 2x26 106 Further improve SST gain by moving location
5 1 4 0• Have improvement for the 1x26 unit • Not much improvement for 2x26 (max a 26
tone shift for having four 2x26s) units
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26K 1x26 2x26 106 Further improve SST gain by moving location
9 9 0 0No gain (already able to select any 26 unit in dif-ferent positions)
Possible assignments (e.g.)
26 26 26 26 26 26 26 26 26
<No 106 unit assigned>
K 1x26 2x26 106 Further improve SST gain by moving location
6 3 3 0Not much improvement because of being able to have enough number of units even with fixed loca-tion
26 26 26 26 26 26 26 26 26
26 26 26 26 26 26 26 26 26
<Only 1x26 unit assigned>
* Similar trend with K = 6 with [1x26, 2x26, 106] = [5, 0, 1]K = 7 with [1x26, 2x26, 106] = [5, 2, 0] K = 8 with [1x26, 2x26, 106] = [7, 1, 0]
Fixed
Moving
Fixed
Fixed
Slide 23 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Analysis on location of resource units (3/3)
• In previous slides on checking SST gain, following is shown– As the number of assignments is small (requiring relatively large size of units) and a few small unit
(like one 1x26) coexists with large size of units, it tends to have an opportunity to improve SST gain of the small unit by moving location while the SST gain for large unit (>26 tone) does not change much from fixed locations
– But, different location of units depending on assignment would cause increase of signaling (indicate multiple combinations of position per assignment case)
• OFDMA is a technique to maximize user multiplexing gain– Good to multiplex as many users as possible– Good to multiplex traffic of similar sizes
• For efficiency of padding, decoding time, etc.
– The analysis showed that SST gain was limited for the case that only one 26-tone unit is assigned in the center
• Given that target 11ax use cases have many users to schedule, the case of scheduling only one 26-tone in the center is an unlikely event.
– SST gain also drops with multiple Tx and/or Rx antennas• The assumption is that the scheduler would assign units smartly to maximize OFDMA gain, and hence fixing the
position of resource units is preferred– Reduced signaling overhead and complexity
Slide 24 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
The Proposed OFDMA Structure
• OFDMA resource units are– (1,2)x26-tone each with 2 pilots – 106-tone with 4 pilots– (1,2)x242-tone each with 8 pilots – 996-tone with 16 pilots
• The 20 MHz OFDMA structure uses the 26-tone, 52-tone and 106-tone at fixed positions, and the non-OFDMA 242-tone
• The 40 MHz OFDMA structure is two replicas of 20MHz structure, and has the addition of non-OFDMA 2x242-tone – Reuse of 11ac 160MHz
• The 80MHz OFDMA structure is two replicas of 40MHz plus one central 26-tone, and has the addition of non-OFDMA 996-tone
• The 160MHz OFDMA structure is two replicas of 80MHz– 996-tone is defined to be a resource unit for this bandwidth of operation
Slide 25 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
20 MHz BSS
Slide 26
Usable tones
26 tone RUs(the exact location of
four leftover tones is TBD)
52 tone RUs + one 26-tone(the exact location of
four leftover tones is TBD)
106 tone RUs+ one 26-tone
242 tone RU(242 non-OFDMA)
S.Azizi, Intel, J. Choi, LGE
May 2015
7 DC Nulls
3 DC Nulls
doc.: IEEE 802.11-15/0330r5
Submission
40 MHz BSS – Two replicas of 20MHz Design
Slide 27
242 tone RUs
484 tone RU(484 non-OFDMA)
S.Azizi, Intel, J. Choi, LGE
May 2015
Usable tones
26 tone RUs(the exact location of
sixteen leftover tones is TBD)
52 tone and 26 tone RUs(the exact location of
Sixteen leftover tones is TBD)
106 tone and 26 tone RUs(the exact location of
eight leftover tones is TBD)
5 DC Nulls
doc.: IEEE 802.11-15/0330r5
Submission
80 MHz BSS
Slide 28
Usable tones
26 tone RUs (the exact location of thirty twoleftover tones is TBD)
52 tone and 26 tone RUs (the exact location of thirty two leftover tones is TBD)
106 tone and 26 tone RUs(the exact location of sixteen
leftover tones is TBD)
242 tone RUs and 26 tone
484 tone RUs and 26 tone RU
Non-OFDMA996 tone
S.Azizi, Intel, J. Choi, LGE
May 2015
7 DC Nullsin case of OFDMA
5 DC Nulls
• Two replicas of 40MHz design + one 26 central• The OFDMA assignment of resource units to different users are completely
aligned with 242-boundary
doc.: IEEE 802.11-15/0330r5
Submission
Fixed Position of Building Blocks
Slide 29
• The proposed resource units are at fixed positions (as shown below)– RUs are building blocks for the scheduler to assign them to different users
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Example 1: 16 OFDMA assignments in 80MHz BSS
Slide 30
• The proposed resource units at fixed positions are used as building blocks for the scheduler to assign them to different users
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Example 2: 8 OFDMA assignments in 80MHz BSS
Slide 31
• The proposed resource units at fixed positions are used as building blocks for the scheduler to assign them to different users
S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
New TerminologyIn previous slides, “non-OFDMA” was used to indicate a case where OFDMA is not used. This was meant to refer to a case where the entire bandwidth of operation is scheduled for a single access (SA) or multi-user MIMO. To be accurate, the following terminology are defined:• HE-MA-PPDU = OFDMA tone plan (or MA tone plan)• HE-SA-PPDU = non-OFDMA tone plan (or SA tone plan)
• HE-MA-MU-PPDU = OFDMA + MU-MIMO• HE-SA-MU-PPDU = non-OFDMA tone plan + MU-MIMO
• The term “OFDMA PPDU” means HE-MA-PPDU or HE-MA-MU-PPDU – the “potential” case where MU-MIMO is being done on part of the PPDU BW
Slide 32 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Straw Poll #1 Do you agree to add the following in 11ax SFD?
The tone structure of the Data field of the HE PPDU is as follows:
1. 242 tone with 8 pilots with (6,5) guard tones and 3 DC tones for a 20MHz HE-SA-PPDU or HE-SA-MU-PPDU
2. 484 tone with 16 pilots with (12,11) guard tones and 5 DC tones for a 40MHz HE-SA-PPDU or HE-SA-MU-PPDU
3. 996 tone with 16 pilots with (12,11) guard tones and 5 DC tones for an 80MHz HE-SA-PPDU or HE-SA-MU-PPDU
4. 2x996 tone for a 160MHz/80MHz+80MHz HE-SA-PPDU or HE-SA-MU-PPDU
• Yes• No• Abstain
Slide 33 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Straw Poll #2 (1/4) Do you agree to add the following to 11ax SFD1. define 20MHz OFDMA building blocks as follows
– 26-tone with 2 pilots, 52-tone with 4 pilot and 106-tone with 4 pilots
and with 7 DC Nulls and (6,5) guard tones, and at locations shown in the picture below- An OFDMA PPDU can carry a mix of different tone unit sizes within each 242 tone unit boundary
The following is TBD:– Exact location of extra leftover tones
Slide 34 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Straw Poll #2 (2/4) 2. define 40MHz OFDMA building blocks as follows
– 26-tone with 2 pilots, 52-tone with 4 pilots, 106-tone with 4 pilots and 242-tone with 8 pilots
and with 5 DC Nulls and (12,11) guard tones, and at locations shown in the picture below
The following is TBD:– Exact location of extra leftover tones
Slide 35 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Straw Poll #2 (3/4) 3. define 80MHz OFDMA building blocks as follows
– 26-tone with 2 pilots, 52-tone with 4 pilots, 106-tone with 4 pilots, 242-tone with 8 pilots and 484-tone with 16 pilots
and with 7 DC Nulls and (12,11) guard tones, and at locations shown in the picture belowThe following is TBD:– Exact location of extra leftover tones
Slide 36 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Straw Poll #2 (4/4) 4. define 160MHz/80MHz+80MHz OFDMA building blocks as follows
– 26-tone with 2 pilots – 52-tone with 4 pilots– 106-tone with 4 pilots– 242-tone with 8 pilots– 484-tone with 16 pilots– 996-tone with 16 pilots (note that 996-tone is defined for 80MHz HE-SA-PPDU or 80MHz
HE-SA-MU-PPDU)
The following is TBD:– Exact location of extra leftover tones
• Yes• No• Abstain
Slide 37 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
References
[1] 11-14-0858-01-00ax-analysis-on-frequency-sensitive-multiplexing-in-wlan-systems.pptx
[2] 11-14-1227-02-00ax-ofdma-performance-analysis.pptx
[3] 11-14-1452-00-00ax-frequency-selective-scheduling-in-ofdma.pptx
[4] 11-14-0855-00-00ax-techniques-for-short-downlink-frames.pptx
[5] 11-15-0099-03-00ax-payload-symbol-size-for-11ax.pptx
[6] 11-15-0132-02-00ax-spec-framework.docx
Slide 38 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-A: Evaluation assumptions (1/2)
Slide 39 S.Azizi, Intel, J. Choi, LGE
• Evaluation setting– Average spectrum efficiency(SE) is used – 100 STAs with same large scale fading (10dB SNR)– 256 subcarriers for 20MHz system BW– Did not consider guard and pilot subcarrier for simplicity– Resource Unit (RU) sizes of 1/2/4/8/16/32/64/128/256 subcarriers are compared– DL Scheduler to maximize SE for each RU
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-A: Evaluation assumptions (2/2)
• Formulation on DL scheduler– Calculate the post-detection SINR on each OFDM subcarrier (j) considering the
receiver algorithm.– Calculate the effective SINR ( ) , using the following equation (RBIR-based)
– Reference the AWGN link performance curves of different MCSs to obtain the mapping between effective SINR and PER
– Obtain each STA’s max rate
– Obtain each RU’s max rate
– Obtain SE for different RU
j
eff
1
0 2
11
1 J
j
jeff J
_ _ __
_ _ max 1 * _sta idx mcs idx mcs idxmcs idx
rate per sta PER siso rate
BW
RUperrateSE
__
idxstaidxsta
RUperrateRUperrate __
__max__
Slide 40 S.Azizi, Intel, J. Choi, LGE
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-B: Simulation studies for number of pilots for 102-data-tone unit (1/3)
Slide 41 S.Azizi, Intel, J. Choi, LGE
May 2015
Simulation setup• 256 FFT in 20 MHz, 1000 bytes• Number of Pilots: 2,3,4,5,6
– 6 pilots: Data tones = [16:122], pilots = [31,46,61,76,91,107]– 5 pilots: Data tones = [17:122], pilots = [34,51,69,87,104] – 4 pilots: Data tones = [18:122], pilots = [38,59,80,101]– 3 pilots: Data tones = [19:122], pilots = [44,70,96]– 2 pilots: Data tones = [20:122], pilots = [53,88]
• Tone amplitude: assumes all 242 tones are loaded → each tone has amplitude = √256/242• Channels: 11nD, UMi-NLoS
• SIG-A symbol and HE-LTF are considered: to ensure that payload performance curves are accurate (enough pilots + phase tracking)
• Channel estimation, timing, CFO estimation, phase tracking: all real. Phase noise added• Channel estimation: smoothing done • Phase tracking: based on the pilots (and data aided tracking for MCS0)
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-B: OFDMA with 102 data tones (2/3)Simulation results for 11nD Channel
Slide 42 S.Azizi, Intel, J. Choi, LGE
May 2015
Little difference in performance as we change #pilots from 2-6
MCS 0 MCS 9
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-B: OFDMA with 102 data tones (3/3)Simulation results for UMi-NLoS
Slide 43 S.Azizi, Intel, J. Choi, LGE
May 2015
MCS 3
At 10% PER, loss with2 pilots: 1.9 dB3 pilots: 0.8 dB
MCS 1
At 10% PER2.15 dB loss with 2 pilots, 0.85 dB loss with 3 pilots
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-C: PER, Tone Erasure, AWGN
Slide 44 S.Azizi, Intel, J. Choi, LGE
20MHz 80MHz
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-C: PER, Tone Erasure, D-NLOS
Slide 45 S.Azizi, Intel, J. Choi, LGE
20MHz 80MHz
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-C: PER, Tone Erasure, UMi-NLOS
Slide 46 S.Azizi, Intel, J. Choi, LGE
20MHz 80MHz
May 2015
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-D: Simulation Studies (1/3)for the Number of DC Nulls in 20MHz OFDMA
Slide 47 S.Azizi, Intel, J. Choi, LGE
May 2015
We performed simulations to study the impact of LO leakage in UL OFDMA on the performance of the 26 tone OFDMA unit straddling the DC• The study is performed as a function of the number of DC tones – 3,5 or 7 and the RF
frequency 2.4GHz and 5GHz.– 20MHz, 256FFT, 25% GI, 40ppm max LO offset – 100 byte payload for the middle 26 tone unit under test– Middle 26 tones
• 3DC case: [-14:-2, 2:14] w/ pilots at [-8, 8]• 5DC case: [-15:-3, 3:15] w/ pilots at [-9, 9]• 7DC case: [-16:-4, 4:16] w/ pilots at [-10, 10]
– -32dB LO leakage for every user. It assumes the following 11ac requirement for 11ax STA participating in UL OFDMA
• When the RF LO is not at the center of the transmitted PPDU BW, power measured at the location of RF LO using resolution BW of 312.5KHz shall not exceed the maximum of -32dB relative to the total transmitted power and -20dBm, or equivalently max(P-32,-20), where P is the transmit power per antenna in dBm and N_{sT} defined in Table 22-5 (Timing Related Constants) – 11ac LO requirement
– 4 RX Antenna– Channel smoothing enabled w/ 4x LTF and with and without tone erasures for the 3DC and 5DC– 3/6/9 users are considered– The LO of each user is assumed to undergo independent channel fading– Frequency offset of each user is uniformly distributed over +/- 235KHz and +/-100KHz
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-D: Simulation Studies (2/3)for the Number of DC Nulls in 20MHz OFDMA
2.4GHz Band
Slide 48 S.Azizi, Intel, J. Choi, LGE
May 2015
• Compared to 7DC, penalty to use 3DC is about 5% in indoor and 10% in outdoor (9 user case)
• Compared to 7DC, no penalty to use 5DC (9 user case)
0 5 10 15 20 25 30 35 400
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
SNR in dB
Spe
ctra
l Eff
icie
ncy
(bps
/Hz)
11nD, 2.4GHz
3DC - 3 Users5DC - 3 Users
7DC - 3 Users
3DC - 6 Users
5DC - 6 Users7DC - 6 Users
3DC - 9 Users
5DC - 9 Users7DC - 9 Users
0 5 10 15 20 25 30 35 400
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
SNR in dB
Spe
ctra
l Eff
icie
ncy
(bps
/Hz)
ITU UMI NLOS, 2.4GHz
3DC - 3 Users5DC - 3 Users
7DC - 3 Users
3DC - 6 Users
5DC - 6 Users7DC - 6 Users
3DC - 9 Users
5DC - 9 Users7DC - 9 Users
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-D: Simulation Studies (3/3)for the Number of DC Nulls in 20MHz OFDMA
5GHz Band
Slide 49 S.Azizi, Intel, J. Choi, LGE
May 2015
• Compared to 7DC, penalty to use 3DC is about 40% in 9 user case• Compared to 7DC, penalty to use 5DC is about 25% in 9 user case
0 5 10 15 20 25 30 35 400
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
SNR in dB
Spe
ctra
l Eff
icie
ncy
(bps
/Hz)
ITU UMI NLOS, 5GHz
3DC - 3 Users5DC - 3 Users
7DC - 3 Users
3DC - 6 Users
5DC - 6 Users7DC - 6 Users
3DC - 9 Users
5DC - 9 Users7DC - 9 Users
0 5 10 15 20 25 30 35 400
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
SNR in dB
Spe
ctra
l Eff
icie
ncy
(bps
/Hz)
11nD, 5GHz
3DC - 3 Users5DC - 3 Users
7DC - 3 Users
3DC - 6 Users
5DC - 6 Users7DC - 6 Users
3DC - 9 Users
5DC - 9 Users7DC - 9 Users
doc.: IEEE 802.11-15/0330r5
Submission
Appendix-E: 80MHz Mask
Slide 50 S.Azizi, Intel, J. Choi, LGE
May 2015
• The following plots show that 11ax has lower OOBE than 11ac, and hence the spectral mask is met even if only (6,5) guard tones are considered.
– The legend “edge 506” indicated the case of (6,5) guard tones
-80 -60 -40 -20 0 20 40 60 80-40
-35
-30
-25
-20
-15
-10
-5
0
5
Spectrum without filter
Frequency (MHz)
PS
D (
dBm
)
256 FFT1024 FFT, Edge 506
37 38 39 40 41 42 43-40
-35
-30
-25
-20
-15
-10
-5
0
5
Spectrum without filter
Frequency (MHz)
PS
D (
dBm
)
256 FFT1024 FFT, Edge 506
