1. CCA schemes for the 120MHz spectrum in China
November 2010
November 2010
CCA schemes for the 120MHz spectrum in China
Authors:
Date:

2. November 2010
November 2010
Background
The channelization in Chinese spectrum has been considered in the proposed specification framework for TGac.
A 120MHz spectrum for channelization is recommended in China to improve the throughput.

3. 5GHz Spectrum in China The 5GHz spectrum for legacy device
November 2010
November 2010
5GHz Spectrum in China
The 5GHz spectrum for legacy device
from 5735MHz to 5835MHz
20MHz×5, 40MHz×2
very few legacy devices work on 5GHz spectrum in China
Total available 5GHz spectrum for 11ac
from 5725MHz to 5850MHz
20MHz×6, 40MHz×3, … ,
provide additional 20MHz and 40MHz channels

4. Enhanced mode and compatible mode
November 2010
November 2010
Enhanced mode and compatible mode
Two modes are defined to deal with above two spectrums.
Enhanced mode
5727.5MHz ~ MHz
High Throughput
compatible mode
5735MHz ~ MHz
Compatible with legacy device
The ac devices selectively work on these two modes while the legacy devices only work on compatible mode

5. One Scenario of two-modes OBSS
November 2010
One Scenario of two-modes OBSS
Assume
BSS2 works on enhanced mode channels
BSS3 works on compatible mode channels
BSS2 and BSS3 are non-overlapped in position
BSS1 is overlapped with BSS2 and BSS3
The transmission of BSS1 may affect BSS2 and BSS3, so the CCA should help BSS1 detect the channel state and avoid the collision with BSS2 and BSS3

6. TBD2(<-62+10log10(TBD1/20)) dBm
November 2010
CCA Requirement
The CCA should detect any signal on the target channel, no matter the signal belongs to enhanced mode transmission, compatible mode transmission or other systems.
The CCA sensitivity should be same as current sensitivity requirement in the proposed specification framework for TGac.
For valid signals:
TBD2(<-62+10log10(TBD1/20)) dBm
For any signal
-62+10log10(TBD1/20) dBm

7. CCA on Two Modes channel
November 2010
November 2010
CCA on Two Modes channel
According to the CCA requirement, the CCA should be not only on the target channel but also on the channels which are overlapped with the target channel. It implies that the CCA should be on two modes channel.
If CCA is on one mode channel ONLY
It’s HARD to achieve the CCA sensitivity requirement, especially for the valid signals on the channel of other mode which is overlapped with the target detecting channel.

8. CCA on Two Modes channel
November 2010
CCA on Two Modes channel
If CCA is on one mode channel ONLY
CCA on blue channel of compatible mode or the red channel of enhanced mode only receive fragmentary (12.5MHz or 7.5MHz bandwidth) signal
It is difficulty to achieve the CCA requirement with the fragmentary signal

9. CCA on Two Modes channel
November 2010
CCA on Two Modes channel
Possible CCA mechanism for the approach 1 in [1]
Channel state is based on the CCA result of the two modes channels
The channel state of each channel is the OR-operation result
The OR-operation should perform with the CCA results of itself and two overlapped channels in another mode
e.g. the red and green channels in slice 8
Channel State of Red Channel =
CCA result:
0: Idle
1: Busy
(CCA of Red Channel) OR (CCA of Green Channel 149 ) OR (CCA of Green Channel 153 )

10. CCA on Two Modes channel
November 2010
CCA on Two Modes channel
Possible CCA mechanism for the approach 2 in [1]
A 120MHz channel CCA is required
CCA on compatible mode channels provides the channel state of compatible mode channels
The 120MHz channel state is the OR-operation result of CCA results of all compatible mode channels and120MHz channel
BUSY : If any channel of compatible mode or 120MHz channel is busy;
IDLE : Only when all the CCA results of compatible mode and120MHz channel are idle;
CCA result:
0: Idle
1: Busy

11. November 2010
Conclusion
The CCA for Chinese two modes should perform on both enhanced and compatible mode channels.
The CCA for Chinese two modes should satisfy the CCA requirement in slice 6.

12. References [1] “11-10-1242-00-00ac-120mhz-channelization-solution.ppt”
November 2010
References
[1] “ ac-120mhz-channelization-solution.ppt”
[2] “ ac-channelization-for-china-s-spectrum.ppt”
[3] “ ac-proposed-specification-framework-for-tgac.doc”