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doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Joint Coding and Modulation Diversity for the Next Generation WLAN
Date: 2013-01-15Authors:
Slide1
Name Affiliations Address Phone Email Zhanji Wu Beijing University of
Post and Telecommunication (BUPT)
Xitucheng Road 10, Haidian district, Beijing, China
+86 10 62281058
Gao Xiang Beijing University of Post and Telecommunication (BUPT)
Xitucheng Road 10, Haidian district, Beijing, China
+86 13811150845
Wu Bin Institute of Microelectronics of the Chinese Academy of Sciences (IMECAS)
3 Beitucheng West Road, Chaoyang District, Beijing, PR China
Yunzhou Li Tsinghua University Tsinghua Rd. Beijng, China
+86 10 62773363
Zhendong Luo China Academy of Telecommunication Research (CATR)
No.52 Hua Yuan Bei Rd., Beijing, China
+86 10 62300171
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission Slide2
Abstract
• The combination of OFDM and MIMO is still a key feature for high-throughput transmission in the next generation WLAN.
• An improved MIMO-OFDM scheme based on modulation diversity named Joint Coding and Modulation Diversity (JCMD) is proposed. It can take full advantage of the coding-gain, the frequency diversity of OFDM system and the spatial diversity of MIMO all together. Simulation results turn out that it can obtain obvious SNR gain as compared with the current BICM-MIMO scheme, which is up to 7dB.
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission Slide3
Background• IEEE 802.11ac greatly enhanced the air interface key technologies, such as
enhanced LDPC coding and tone mapper, multiuser (MU) MIMO, broader bandwidth up to 160MHz, higher order quadrature amplitude modulation (QAM) modulation up to 256QAM and more transmit antenna number up to 8.
• [1] had proposed that the system capacity of 10 G bit/s will be achieved by combining some possible technologies for the next generation WLAN.
• The system capacity should be improved to maintain high performance.– Higher peak data rate
• extend the bandwidth/channel, e.g. 320 MHz/ch
• The next generation WLAN will support more spatial streams
• support more users in a MU-MIMO transmission– Higher spectrum efficiency
• DL-OFDMA
• Advanced SDMA
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
JCMD-MU-MIMO Transmit Diagram
Slide 4
NOTES
–The blocks drawn in dotted line are our proposed additional processing on the basis of the current 802.11 ac standard scheme.
–In simulations, the spatial mapping method for SU and MU MIMO are SVD and BD precoding, respectively.
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
• Rotational Modulation– Maximized modulation diversity order.
– The relationship between conventional modulated complex symbol A + j*B and the rotational modulated complex symbol X + j*Y can be expressed as:
Joint Coding and Modulation Diversity
cos sin
sin cos
X A
Y B
Slide 5
QPSK R-QPSK
L=1 L=2
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Optimum rotational matrices are proposed as follows
Proposed Rotational Matrices
iu
Slide 6
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
• Q-Component Interleaver– Spatial Q-Interleaving
Let and denote the input Q-component and the output Q-component of the spatial Q-interleaver on the spatial stream at the t instant. The spatial Q-interleaving is defined as follows, where is the spatial stream number.
(1)– Frequency domain Q-Interleaving
On each spatial stream, the frequency domain Q-Interleaving is carried out as follows,
where is the OFDM subcarrier number.
(2)
Joint Coding and Modulation Diversity
Slide 7
, 1, where , 0, 1i it t SS SSQ Q k N i k i N
, mod , where , 0, 1 , 0, 12
j j SDk i SD SD SS
NQ Q k i N k i N j N
itQ
itQ
thi
SSN
SDN
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Simulation Parameters for 802.11ac SU-MIMO Scheme
Slide 8
Parameters Values
PHY scheme OFDM
Antenna scheme 2*2 , 4*4
Bandwidth 20 MHz
Length of FFT 64
Number of subcarriers 56
Number of data subcarriers 52
Code Type BCC, LDPC
Channel Model 802.11ac channel model
MCSs MCS2, MCS4, MCS7, MCS8
Sub-carrier spacing 312.5 kHz
Channel estimation Perfect CSI
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
FER performance for 2*2 SU-MIMO scheme in 802.11 AC Channel, case E, NLOS
Slide 9
MCSSNR Gain in dB (FER=0.01)
BCC LDPC
MCS2 7.0 6.8
MCS4 4.8 4.5
MCS7 4.4 3.9
MCS8 2.1 1.6
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
FER performance for 4*4 SU-MIMO scheme in 802.11 AC Channel, case E, NLOS
Slide 10
MCSSNR Gain in dB (FER=0.01)
MCS2 7.2
MCS4 4.2
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Simulation Parameters for 802.11ac MU-MIMO Scheme
Slide 11
Parameters ValuesPHY scheme OFDM
User number 2
The number of antennas at TX 4
The number of antennas at RX per user 2
Bandwidth 20 MHz
Length of FFT 64
Number of subcarriers 56
Number of data subcarriers 52
Code type BCC, LDPC
Channel model 802.11ac channel model
MCSs MCS2, MCS4, MCS7, MCS8
Sub-carrier spacing 312.5 kHz
Precoding BD
Channel estimation Perfect CSI
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
FER performance for MU-MIMO scheme in 802.11 AC Channel, case E, NLOS, 2 users, each user has 2 spatial streams.
Slide 12
MCSSNR Gain in dB (FER=0.01)
BCC LDPC
MCS2 4.2 4.2
MCS4 2.2 2.0
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Hardware prototype system
Slide 13
BBU RRURohde&Schwarz
FSV RRU BBU
PC
Rohde&Schwarz
AMURohde&Schwarz
SMBV
Parameters Values
Carrier frequency (GHz) 2.3504
Bandwidth (MHz) 4.0
Sampling frequency (MHz) 3.84
Sampling interval (ns) 260
FFT 256
Sub-carrier spacing (kHz) 15
OFDM symbol interval (us) 75
GI interval (us) 8.33
Number of OFDM symbols in 5ms frame
66 (1*preamble + 18 + 47 symbols)
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission Slide 14
Channel estimation SNR Gain in dB (FER=0.01)
LS 3
LMMSE 3
FER performance for Hardware prototype system in VA channel
9 10 11 12 13 14 15 1610
-4
10-3
10-2
10-1
100
MIMO-LMMSE-LS-VA | 0km/h | SMBV:-37dBm
S/N
FE
R
LMMSE BICM
LMMSE JCMDLS BICM
LS JCMD
Parameters Values
Number of transmit antenna 2
Number of receive antenna 2
Channel coding LDPC
Code rate 3/4
Modulation QPSK
Channel model VA
Channel estimation LS, LMMSE
• Hardware prototype system has significant performance advantage about 3 dB.
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission Slide 15
Complexity Analysis
The overall complexity of the proposed JCMD scheme is almost the same as the conventional BICM scheme.
• The total number of addition/subtraction and multiplication/division operations is used to represent the overall complexity base on the hardware prototype system.
Conventional scheme JCMD scheme Proportion
QPSK 578872433 579328224 1:1.0008
16QAM 578968224 581646624 1:1.0046
64QAM 579105024 590769024 1:1.0201
1 2 30
1
2
3
4
5
6
7x 10
8
BICM
JCMD64QAM16QAMQPSK
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
Conclusions
• JCMD scheme jointly optimizes the MIMO-OFDM, channel coding and modulation together, which makes full use of time, frequency and space diversity.
– Rotational modulation
– Q-components interleaver
• The proposed scheme can obtain obvious SNR gain (up to 7dB) as compared with the current BICM MIMO scheme in IEEE 802.11 standard for LDPC/BCC coding, all MCSs and various channels .
– Significant SNR gain • Larger coverage area
• Lower transmit power
– Low complexity• Low processing power and cost
• JCMD is suitable for the next generation WLAN.
Slide 16
doc.: IEEE 802.11-13/0112r0
Zhanji Wu, et. Al.
January 2013
Submission
References
[1] 11-12-0820-00-0wng-improved-spectrum-efficiency-for-the-next-generation-wlans.pptx
[2] 11-11-0883-01-00ah-Channel-Model-Text.docx
[3] 3GPP TR 25.996 - Technical Specification Group Radio Access Network; Spatial channel model for Multiple Input Multiple Output (MIMO) simulations
[4] 11-11-0069-01-00ah-tgah-Introductory-proposal.ppt
[5] 11-11-0336-00-00ac-joint-coding-and-modulation-diversity-to-802-11ac.ppt
[6]11-11-1137-02-00ah-specification-framework-for-tgah.docx
Slide 17
