dedicated resources allocation for direct communications in ieee 802.16n document number: ieee...
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Dedicated resources allocation for direct communications in IEEE 802.16n
Document Number:IEEE C802.16n-10/0051r2
Date Submitted:2011-03-14
Source:Young-Ho Jung E-mail: [email protected] Aerospace University
Sungcheol Chang, Eunkyung Kim, Sungkyung Kim, Hyun Lee, Chulsik Yoon E-mail: [email protected] , ETRI [email protected] *<http://standards.ieee.org/faqs/affiliationFAQ.html>
Re:Call for contributions for 802.16n AWD
Base Contribution:N/A
Purpose:To be discussed and adopted by TG802.16n
Notice:This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.
Copyright Policy:The contributor is familiar with the IEEE-SA Copyright Policy <http://standards.ieee.org/IPR/copyrightpolicy.html>.
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.
Direct Communication Scenarios
• S1: HR-MS forwarding to network (IEEE 802.16n network reference model )
– Case 1: HR-MS S/S is outside of HR-BS coverage– Case 2: HR-MS S/S is within the coverage of HR-BS
• S2: Local connection between HR-MSs (IEEE 802.16n network reference model )
– Case 1: one of HR-MSs is outside of HR-BS coverage– Case 2: all HR-MSs are within the coverage of HR-BS– Case 3: all HR-MSs are outside of HR-BS coverage
HR-BS Backhaul1HR-MS HR-MS R1RMM4
HR-MS S/S Forwarding HR-MS
HR-MS S/S: HR-MS with sourcing and sinking of dataForwarding HR-MS: HR-MS with fowrding function
HR-MS HR-MSRMM5
Candidate Options for Direct Communication Resources
• O1: some of DL resources are allocated for direct communications
– TDM– FDM
• O2: some of UL resources are allocated for direct communications
– TDM– FDM
Interference scenarios for direct communications
• Inter-Carrier Interference (ICI) and Inter-Symbol Interference (ISI)
– Condition: When the signals from different transmitters arrive with a time difference larger than CP size
– ExamplesHR-BSHR-BS
HR-MS (RF)
HR-MS (RF)
HR-MSHR-MS
HR-MSHR-MSHR-
MSHR-MS
AMSAMS
Utilize differentsubcarriers of UL resources
HR-BSHR-BS
HR-MS (RF)
HR-MS (RF)
HR-MSHR-MS
HR-MSHR-MSHR-
MSHR-MS
AMSAMS
Utilize differentsubcarriers of DL resources
Interference scenarios for direct communications
• ADC bit resolution reduction due to large RMS value in time domain (see Appendix for numerical analysis)
– Condition: When receiving signals, if some signals from adjacent transmitters (even if orthogonal subcarriers are used) are received with very large power.
– ExamplesHR-BSHR-BS
HR-MS (RF)
HR-MS (RF)
HR-MSHR-MS
HR-MSHR-MS
AMSAMS
Utilize differentsubcarriers of UL resources
HR-BSHR-BS
HR-MS (RF)
HR-MS (RF)
HR-MSHR-MS
HR-MSHR-MS AMSAMS
Utilize differentsubcarriers of DL resources
p-p
for
AD
C
p-p
for
AD
C
Direct-comm. signalCellular UL signal
p-p
for
AD
C
p-p
for
AD
C
Direct-comm. signalCellular DL signal
Interferences for Direct-mode Resource Allocation Options (HR-MS forwarding)
HR-MS AMS or MS
HR-MS HR-RS or HR-BS
AMS or MS HR-MS
HR-RS or HR-BS HR-MS
S1
Case1
DL(O1)
TDM - - - -
FDM
Reduction of ADC bit resolution for
adjacent active AMS or MS
- -
-(time
synchronization is required)
UL(O2)
TDM -
-(time
synchronization is required)
-(time
synchronization is required)
-
FDM - -
Reduction of ADC bit resolution of HR-MS due to adjacent active AMS or MS
-
Case2
DL(O1)
TDM - - - -
FDMReduction of ADC bit resolution for
adjacent AMS or MS- - -
UL(O2)
TDM - - - -
FDM - -
Reduction of ADC bit resolution of HR-MS due to adjacent active AMS or MS
-
S1: HR-MS forwarding to networkCase 1: HR-MS S/S is outside of HR-BS coverage, Case 2: HR-MS S/S is within the coverage of HR-BS
Interferences for Direct-mode Resource Allocation Options (Local Connection)
HR-MS AMS or MS
HR-MS HR-RS or HR-BS
AMS or MS HR-MS
HR-RS or HR-BS HR-MS
S2
Case1
DL(O1)
TDM - - - -
FDM
Reduction of ADC bit resolution for
adjacent active AMS or MS
- -
-(time
synchronization is required)
UL(O2)
TDM -
-(time
synchronization is required)
-(time
synchronization is required)
-
FDM - -
Reduction of ADC bit resolution of HR-MS due to adjacent active AMS or MS
-
Case2
DL(O1)
TDM - - - -
FDMReduction of ADC bit resolution for
adjacent AMS or MS- - -
UL(O2)
TDM - - - -
FDM - -
Reduction of ADC bit resolution of HR-MS due to adjacent active AMS or MS
-
S2: Local connection between HR-MSs Case 1: one of HR-MSs is outside of HR-BS coverage, Case 2: all HR-MSs are within the coverage of HR-BS
Interferences for Direct-mode Resource Allocation Options (Local Connection)
HR-MS AMS or MS
HR-MS HR-RS or HR-BS
AMS or MS HR-MS
HR-RS or HR-BS HR-MS
S2Case
3
DL(O1)
TDM-
(ICI and ISI to cell edge AMS or MS)*
- - -
FDM-
(ICI and ISI to cell edge AMS or MS)*
- - -
UL(O2)
TDM - --
(ICI and ISI from cell edge AMS or MS)*
-
FDM - --
(ICI and ISI from cell edge AMS or MS)*
-
S2: Local connection between HR-MSs Case 3: all HR-MSs are outside of HR-BS coverage
*: If there is any AMS or MS within the HR-BS coverage near the HR-MS pair (outside of HR-BS coverage), ICI and ISI can be taken effect due to timing synchronization mismatch, however, the possibility is very little.
Proposed text for IEEE802.16n AWD
• 16.3.3.8 Frame structure supporting direct communicationFor direct communication, some of downlink and uplink resources shall be dedicatedly assigned for direct communication.
Conclusion
• If exclusive resources are allocated for direct communication, there is no severe interference.
• If TDM type resource segmentation is used, there is no interference at all.
• If FDM type resource segmentation is used, degradation of ADC resolution problem can be happened, however, its possibility is very little, and the effect of ADC resolution reduction is not severe.(DL resource: HR-MS AMS or MS, UL resource: AMS or MS HR-MS)
If dedicated resources are allocated for direct communication, all combinations of TDM/FDM and DL/UL resources can be considered as resource segmentation option for direct communication .
Appendix
• Analysis of ADC bit resolution reduction due to high power interfering signals– ADC resolution reduction at HR-MSs due
to adjacent AMSs in the uplink resources is analyzed, however, the effect at the AMS due to HR-MSs in the downlink resource is identical.
• Typical parameters– ADC resolution for mobile station: 12 bits (for both I/Q signals)– RMS value of AGC output = 127
• RMS value of received signal is mapped to 127 of ADC output
– RMS value of direct-communication signal• 127*sqrt(Pdirect)/sqrt(Pdirect+PCellular ）
• e.g. ） PCellular ／ Pdirect ＝ 1000 (30dB ） RMS value of direct mode signal ＝4.02 PCellular ／ Pdirect ＝ 100 (20dB ） RMS value of direct mode signal ＝ 12.7
PCellular ／ Pdirect ＝ 10 (10dB ） RMS value of direct mode signal ＝ 40.1
ADC bit resolution of the desired signal (direct comm.) is reduced (1/3 ~ 1/30)
The effect of ADC bit resolution reduction
• Interference due to ADC bit resolution reduction– ADC bit resolution reduction incensement of quantization noise in time
domain inter-carrier interference (ICI) in the frequency domain– Quantization error (variance) = 2/12
– ＝１／ RMSdirect
• 4.02 (-30dB), 12,7 (-20dB), 40.1 (-10dB)
– Upper bound of SINR• SINR (dB) = 10log10 (1/Quantization error variance) = 10log10(12/ 2)
• Assumptions for performance analysis– FFT size = 1024– Dedicated resources are allocated for direct communication– RMS value of AGC output = 127
Pdirect /PCellular Theoretical bound Simulation results
-10dB 42.9dB 42.9dB
-20dB 32.9dB 32.9dB
-30dB 22.9dB 22.9dB
The effect of ADC bit resolution reduction
• Power of direct comm./ power of cellular interference = -20dB
• Power of direct comm. / power of cellular interference = -30dB
-1.5 -1 -0.5 0 0.5 1 1.5-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5-1.5
-1
-0.5
0
0.5
1
1.5
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-1.5 -1 -0.5 0 0.5 1 1.5-1.5
-1
-0.5
0
0.5
1
1.5
The effect of ADC bit resolution reduction - constellations
blue o – floating point, red x – with the effect of ADC bit resolution reduction)
• SNR vs. SINR (effect of ICI due to ADC resolution reduction)
– Power of direct comm. power/ power of cellular interference = -20dB
– Performance loss at the High SNR range (marginal loss less than SNR = 15dB)
- Power of direct comm. power/ power of cellular interference = -30dB
The effect of ADC bit resolution reduction - SINR reduction due to ICI (inter-carrier
interference)
-10 -5 0 5 10 15 20 25 30-15
-10
-5
0
5
10
15
20
25
30
SNR (dB)
SIN
R (
dB)
floating
with effect of ADC resolution reduction
-10 -5 0 5 10 15 20 25 30-15
-10
-5
0
5
10
15
20
25
30
SNR (dB)
SIN
R (
dB)
floating point
with the effect of ADC bit resolution reduction