1. MU-MIMO support for Heterogeneous Devices
July 2010
doc.: IEEE /0784r0
July 2010
MU-MIMO support for Heterogeneous Devices
Date:
Authors:
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

2. Abstract Potential Usage Model for MU-MIMO
July 2010
doc.: IEEE /0784r0
July 2010
Abstract
Potential Usage Model for MU-MIMO
Support MU-MIMO with Heterogeneous Devices
Multi-encoder
Single Guard Interval
Multi-SS/MCS
Multi-band
VHT-SIG design Aspects
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

3. Potential Usage Model for MU-MIMO
July 2010
doc.: IEEE /0784r0
July 2010
Potential Usage Model for MU-MIMO
MU-MIMO may be able to support simultaneous multi-link peer-to-peer transmission for throughput enhancement
Various heterogeneous devices in a typical networked home scenarios (e.g. DTV, PC and handheld devices)
Each device may have different capabilities (e.g. supported channel bandwidth, MCS, FEC, etc)
It may be not typical to support MU-MIMO with all same capabilities AP
STA
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

4. Support MU-MIMO with Heterogeneous Devices
July 2010
Support MU-MIMO with Heterogeneous Devices
Various heterogeneous devices with different channel bandwidth, MCS and FEC are scattered in a typical networked home scenarios (e.g. DTVs, PCs, and handheld devices)
MU-MIMO support for heterogeneous devices will be most practical and important for good User Experience
e.g. support seamless streaming (transmission not interrupted in order to support data for small devices) of HD multimedia AP
20MHz, BCC
40MHz, BCC
80MHz, LDPC
MU-MIMO
Byeongwoo Kang, LG Electronics

5. Multi-encoder Transmission
July 2010
Multi-encoder Transmission
STA will have the choice to additionally support LDPC (BCC mandatory)
Two Methods of supporting Multi-encoder transmission
VHT-SIG-B indication of FEC type for each STA
1 bit FEC field in VHT-SIG-A
STAs which do not support LDPC always decode with BCC regardless of FEC bit
STAs which support LDPC follow directions of FEC bit
Byeongwoo Kang, LG Electronics

6. Single Guard Interval Transmission (1/3)
July 2010
doc.: IEEE /0784r0
July 2010
Single Guard Interval Transmission (1/3)
In case of the multiple GT duration
In case of the single GT duration
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

7. Single Guard Interval Transmission (2/3)
July 2010
doc.: IEEE /0784r0
July 2010
Single Guard Interval Transmission (2/3)
Consideration aspects to support the multiple GI duration
At the transmitter side
Different processing chains for the STAs having long GI duration or short GT duration
Boundary of OFDM symbols between different GT durations are not aligned
Spurious Spatial Interference in OFDM symbol boundaries for MU-MIMO between Spatial stream in case frequency selective precoding is applied
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

8. Single Guard Interval Transmission (3/3)
July 2010
doc.: IEEE /0784r0
July 2010
Single Guard Interval Transmission (3/3)
Consideration aspects to support the multiple GI duration
At the receiver side
GI is needed to get frequency data symbols
Having GI in VHT-SIG-B may cause decoding complexity issues (highly dependent on implementation)
GI information may be needed in VHT-SIG-A
General Observation
Single GT Duration transmission for MU-MIMO feature is useful
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

9. Multi-SS/MCS Transmission
July 2010
doc.: IEEE /0784r0
July 2010
Multi-SS/MCS Transmission
Nothing additional needs to be done
Variable # of Spatial Streams per STA already supported
Different MCS per STA already supported
Byeongwoo Kang, LG Electronics
Yujin Noh, LG Electronics

10. Single Channel Bandwidth Transmission
July 2010
Single Channel Bandwidth Transmission
It is assumed that we allow a Group involving STAs with different channel bandwidth capabilities for MU-MIMO support
AP does not transmit its data packet to STAs with lower CB capability
Case 1: AP transmits 20MHz data packet
to STA1, STA2, STA3 and STA4
Case 2: AP transmits 40MHz data packet
To STA2, STA3 and STA4
Case 3: AP transmits 80MHz data packet
To STA4
Byeongwoo Kang, LG Electronics

11. Multi-BW Transmission Example 1
July 2010
Multi-BW Transmission Example 1
It is assumed that we allow a Group involving STAs with different channel bandwidth capabilities for MU-MIMO support
20MHz CB indication in VHT-SIG-A
Both STA1 and STA2 receive 20MHz data packet
STA 1 with 20MHz CB capability
STA 2 with 80MHz CB capability
Frequency
Time
STA 1
STA 2
User
Byeongwoo Kang, LG Electronics

12. Multi-BW Transmission Example 2
July 2010
Multi-BW Transmission Example 2
40MHz CB indication in VHT-SIG-A
For STA2 with 80MHz CB capability, receive 40MHz data packet
For STA1 with 20MHz CB capability, receive 20MHz data packet
STA 1 with 20MHz CB capability
STA 2 with 80MHz CB capability
Frequency
Time
User
STA 1
STA 2
Byeongwoo Kang, LG Electronics

13. Multi-BW Transmission Support
July 2010
Multi-BW Transmission Support
AP are allowed to transmit the different size of data packet to even STAs with lower CB capability as well comparing with CB indication in VHT SIG-A
AP transmits 20MHz data packet
to STA 1
AP transmits 40MHz data packet
to STA 2 and STA 3
AP transmits 20MHz data packet
to STA 4
Byeongwoo Kang, LG Electronics

14. VHT-SIG-A Design for Multi-BW Transmission
July 2010
VHT-SIG-A Design for Multi-BW Transmission
Method of MU-MIMO support with heterogeneous devices
STA can choose minimum value between the signaled CB and the maximum usable CB of STA
The signaled CB can be the channel bandwidth indication in VHT-SIG-A
The max usable CB of STA can be from the Channel Width information in Notify Channel Width frame
Note : STA sends the Notify Channel Width frame to another AP/STA(s) to indicate the channel width it is able to receive
Channel Bandwidth to be used =
min (signaled CB, max usable CB of STA)
Order
Information 1
Category 2
Action 3
Channel Width
Byeongwoo Kang, LG Electronics

15. VHT-SIG design aspects
July 2010
VHT-SIG design aspects
Parameter design guides and consideration for VHT-SIG-A and VHT-SIG B
Practical usage model for MU-MIMO with heterogeneous devices
Multi-encoder
Option 1: 1 bit FEC field in VHT-SIG-A for all STAs
Option 2: 1bit FEC field in VHT-SIG-B for each STA
Multi-band
Bandwidth field is determined to be included in VHT-SIG-A
Multi-SS/MCS
Different MCS per STA supported in VHT-SIG-B
Multiple spatial stream per STA supported in VHT-SIG-A
Single Guard Time duration in VHT-SIG-A will be suitable for all STAs
Byeongwoo Kang, LG Electronics

16. July 2010
Summary
MU-MIMO support for heterogeneous devices will be most practical and important in a typical networked home scenarios
Multi-encoder
Multi-SS/MCS
Multi-band
Single Guard Time duration
Byeongwoo Kang, LG Electronics

17. July 2010
Strawpoll #1
Do you support adopting multi-encoder MU-MIMO transmissions and edit the spec framework document, with following text?
R4.D: DL MU-MIMO shall not restrict the transmission encoder type for STA(s) with LDPC encoding/decoding capability in case that said STA(s) is being paired by MU-MIMO transmission with STA(s) which do not have LDPC encoding/decoding capability
Yes No
Abstain
Byeongwoo Kang, LG Electronics

18. July 2010
Strawpoll #2
Do you support adopting same GI configuration transmission for all spatial streams for both SU-MIMO and MU-MIMO transmissions and edit the spec framework document, with following text?
R4.E: DL MU-MIMO shall only support the same Guard Interval (GI) for all spatial stream regardless of STA capability.
Yes No
Abstain
Byeongwoo Kang, LG Electronics

19. July 2010
Strawpoll #3
Do you support adopting multi-bandwidth transmission for different STAs which do not all support the maximum BW of the DL MU-MIMO transmission and edit the spec framework document, with following text?
R4.F: DL MU-MIMO shall support potential transmission of different bandwidth for different set of spatial streams associated with different STA which do not have the same BW capability. The exact supported bandwidth combinations of DL MU-MIMO transmission and signaling and mechanisms of how to support multi-bandwidth DL MU-MIMO transmission is TBD.
Yes No
Abstain
Byeongwoo Kang, LG Electronics