1. IEEE P802.22 Wireless RANs Date: 2006-06-15
2006 March
Effective and Flexible Structure for CPE CSIT Collection at base station for TDD OFDMA architecture
IEEE P Wireless RANs Date:
Authors:
Notice: This document has been prepared to assist IEEE It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair
Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at
HuaWei

2. 2006 March
Co-Authors:
HuaWei

3. Radio resource is very scarce
2006 March
Motivation
Design good resource allocation algorithm to fully utilize the resource
Radio resource is very scarce
CSIT is a crucial input
HuaWei

4. Very important to design a good CSIT collection mechanism
2006 March
CSIT Acquisition
CSIT: Channel gain (Phase is not important for resource allocation)
Using the reciprocity of the uplink and downlink channel
 CSIT of the excited subchannels of those currently uplink-active CPEs
Using feedback
 For unexcited subchannels of the CPEs
Very important to design a good CSIT collection mechanism
HuaWei

5. Features of Downlink WRAN System
2006 March
Features of Downlink WRAN System
BS knows the QoS requirements and queueing states of all the CPEs
 BS can determine which CPEs have higher priority and are more urgent
Maximum Doppler frequency is very small
 The CSIT can be updated rather infrequently
Variation of Doppler frequency among CPEs is limited
 The CSIT update frequencies of CPEs are similar
Polling-based CSIT feedback mechanism
HuaWei

6. Main Features of Our Proposed Structure (1)
2006 March
Main Features of Our Proposed Structure (1)
Centralized polling at the BS
 BS decides which CPEs to poll based on QoS requirements, queueing states, etc.
 BS decides for each selected CPE which subband to estimate based
on detected incumbents, history, etc.
Placement of the polling information
 For currently active CPEs, the polling information is contained in the UL-MAP
 For currently inactive CPEs, the polling information is contained in some broadcast channel
HuaWei

7. Main Features of Our Proposed Structure (2)
2006 March
Main Features of Our Proposed Structure (2)
Flexibility
 BS may request CSIT of any subband
 BS can allocate more or less subchannels and/or OFDM symbols for each CPE to convey the feedback, depending on the QoS requirement and the urgency of the downlink traffic, etc.
 Default CSIT quantization level is known to both BS and CPEs
 BS may control the precision of the feedback
 CPE feedbacks only the important information to BS (explained on the next page)
HuaWei

8. Main Features of Our Proposed Structure (3)
2006 March
Main Features of Our Proposed Structure (3)
CPEs decide which subchannel CSIT to feedback based on the channel condition 
Using predefined modulation and coding scheme, given the number of subchannels, OFDM symbols that are used to convey CSIT, and the CSIT quantization level, CPE knows it can feedback the CSIT of say c number of subchannels
For TDD system, the CPE should choose c number of un-excited subchannels with the largest gains  } x
Subchannel Gain 6
Subchannel Index
for i = 1:c {
If Q-bit feedback is allowed, then
CSIT_Feedback_Format() {
Remarks
Size (bits) ë û ) ( Q c + =
CSIT_Feedback_Format
HuaWei

9. CSIT Collection Request Message (1)
2006 March
CSIT Collection Request Message (1)
Syntax
Size (bits)
Remarks
CSIT_Collection_Request() {
N_CID 8
N_CID is the number of selected CPEs that are in this subband
for i = 1: N_CID {
CID 16
Feedback_Control( )
variable }
CSIT_Collection_Request for active CPEs (to be cont’d)
HuaWei

10. Feedback Control Message (1)
2006 March
Feedback Control Message (1)
Syntax
Size (bits)
Remarks
Feedback_Control() {
Subband_change_flag 1
0: estimate the downlink CSI of this subband
1: in the next frame estimate the downlink CSI of the subband specified by Subband Index
If{Subband_ change_flag==1}{
Subband Index 8
At most MHz subband }
Else{
Quantization_level_flag
0: use default quantization level, L=a
1: use specified quantization level
If{ Quantization_level_flag ==1}{
Quantization level, L=b 2
Assume there are at most 4 additional quantization precision levels
Feedback_ch_constraint_flag
0: use default number of subchannels, N=c
1: use specified number of subchannels
If{ Feedback_ch_constraint_flag==1}{
Number of subchannels, N=d 6
Assume 64 subchannels in a subband
Feedback_Control Message (to be cont’d)
HuaWei

11. Feedback Control Message (2)
2006 March
Feedback Control Message (2)
Feedback_symb_constraint_flag 1
0: use default number of OFDM symbols, M=e
1: use specified number of OFDM symbols
If{Feedback_symb_constraint_flag==1}{
Number of OFDM symbols, M=f 2
Assume at most 4 OFDM symbols can be used to do feedback }
for j=1:N{
Subchannel Index 6
Feedback_Control Message (cont’d)
HuaWei

12. CSIT Collection Request Message (1)
2006 March
CSIT Collection Request Message (1)
Syntax
Size (bits)
Remarks
CSIT_Collection_Request() {
N_CID 8
N_CID is the number of selected inactive CPEs
for i = 1:N_CID{
CID 16
Subband Index
Assume at most MHz subband
Quantization_level_flag 1
0: use default quantization level, L=a
1: use specified quantization level
If{ Quantization_level_flag ==1}{
Quantization level, L=b 2
Assume there are at most 4 additional quantization precision levels }
Feedback_ch_constraint_flag
0: use default number of subchannels, N=c
1: use specified number of sub-channels
If{ Feedback_ch_constraint_flag==1}{
Number of subchannels, N=d 6
Assume 64 subchannels in a subband
CSIT_Collection_Request for inactive CPEs (to be cont’d)
HuaWei

13. CSIT Collection Request Message (2)
2006 March
CSIT Collection Request Message (2)
Feedback_symb_constraint_flag 1
0: use default number of OFDM symbols, M=e
1: use specified number of OFDM symbols
If{Feedback_symb_constraint_flag==1}{
Number of OFDM symbols, M=f 2
Assume at most 4 OFDM symbols can be used to do feedback }
for j=1:N{
Subchannel Index 6
CSIT_Collection_Request for inactive CPEs (Cont’d)
HuaWei