1. Month Year
doc.: IEEE yy/xxxxr0
Mar. 2010
Modification on DFS and DCF procedure adapting to FCC rules in TVWS Part 2: Hidden Node
Date:
Authors:
Chin-Sean Sum, NICT
John Doe, Some Company

2. Mar. 2010
Executive Summary
This document describes the ‘mutation’ of the hidden node problem due to different allowable transmission power levels in the IEEE af
This document proposes a solution for the ‘mutated hidden node’ problem by using a simple relayed-RTS-CTS method
This proposed solution requires
very simple additions to existing operational procedures
minor changes to the existing standard
Summary on the required changes to legacy
Minor changes to the RTS frame
Minor changes to the RTS-CTS operational procedure
Chin-Sean Sum, NICT

3. Presentation Outline Classical Hidden Node Problem and Solution
Mar. 2010
Presentation Outline
Classical Hidden Node Problem and Solution
‘Mutated’ Hidden Node Problem
Proposed Mutated Hidden Node Solution
Required Changes to Legacy
Chin-Sean Sum, NICT

4. Classical Hidden Node Problem ~Scenario~
Mar. 2010
Classical Hidden Node Problem ~Scenario~
Chin-Sean Sum, NICT

5. Classical Hidden Node Solution ~RTS-CTS Overview~
Mar. 2010
Classical Hidden Node Solution ~RTS-CTS Overview~
Chin-Sean Sum, NICT

6. Classical Hidden Node Solution ~RTS-CTS Timing~
Mar. 2010
Classical Hidden Node Solution ~RTS-CTS Timing~
Chin-Sean Sum, NICT

7. ‘Mutated’ Hidden Node Problem ~The Origin~
Mar. 2010
‘Mutated’ Hidden Node Problem ~The Origin~
Classical hidden node problem involved only one transmission power level and thus one operating range
The FCC regulation for TVWS specifies multiple transmission power levels: 4W, 100mW and 50mW
As a result, the hidden node may become ‘more hidden’, hence the name ‘mutated’
In this document, the scenarios of the mutated hidden node and the corresponding proposed solution are presented
Chin-Sean Sum, NICT

8. ‘Mutated’ Hidden Node Problem ~Just How Serious is the Problem~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Just How Serious is the Problem~
Chin-Sean Sum, NICT

9. ‘Mutated’ Hidden Node Problem ~Operating Range~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Operating Range~
100mW STA
Operating Range (km)
4W STA
Urban
0.47
1.7
Suburban
0.64
2.4
Chin-Sean Sum, NICT

10. ‘Mutated’ Hidden Node Problem ~Scenario 1~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Scenario 1~
V_1, V_2 and I_1 are able to detect each other
No interference and no hidden node
Chin-Sean Sum, NICT

11. ‘Mutated’ Hidden Node Problem ~Scenario 2~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Scenario 2~
If V_1 or V_2 transmits, I_1 may also transmit
Interference to V_2
Chin-Sean Sum, NICT

12. ‘Mutated’ Hidden Node Problem ~Scenario 3~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Scenario 3~
If V_1 or V_2 transmits, I_1 may also transmit
Interference to V_1 or V_2
Chin-Sean Sum, NICT

13. ‘Mutated’ Hidden Node Problem ~Shortage of Classical RTS-CTS~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Shortage of Classical RTS-CTS~
Probable for scenario 2 and scenario 3
Chin-Sean Sum, NICT

14. ‘Mutated’ Hidden Node Problem ~Discussion~
Mar. 2010
‘Mutated’ Hidden Node Problem ~Discussion~
Scenario 1 shows no hidden node problem
Scenario 2 and 3 show that potential interference may be present due to hidden node
Furthermore, the classical RTS-CTS solution may not be sufficient to tackle the problem
The range of RTS has be extended to increase the efficiency of the RTS-CTS method
Chin-Sean Sum, NICT

15. ‘Mutated’ Hidden Node Solution ~Proposed Relayed-RTS-CTS Method~
Mar. 2010
‘Mutated’ Hidden Node Solution ~Proposed Relayed-RTS-CTS Method~
Chin-Sean Sum, NICT

16. ‘Mutated’ Hidden Node Solution ~ Relayed-RTS-CTS Procedure~
Mar. 2010
‘Mutated’ Hidden Node Solution ~ Relayed-RTS-CTS Procedure~
Assumption:
The initiating STA has the capability to obtain the addresses of the relaying STA(s)
Initiating STA sends RTS to receiving STA
In the receiving STA, by checking the Relay Control field and relay address fields:
the receiving STA knows whether it should use the conventional RTS-CTS, or the relayed-RTS-CTS mechanism
the receiver knows whether it should act or ignore the incoming RRTS
The RRTS is continuously relayed until it reaches the destination STA
The destination STA sends CTS to the initiating STA
Initiating STA sends data upon receiving CTS
Chin-Sean Sum, NICT

17. ‘Mutated’ Hidden Node Solution ~Relayed-RTS-CTS Timing~
Mar. 2010
‘Mutated’ Hidden Node Solution ~Relayed-RTS-CTS Timing~
RRTS – relayed-RTS
Chin-Sean Sum, NICT

18. Mar. 2010
Required Changes to Legacy (1/2) ~On the Existing RTS-CTS Procedure~
The existing RTS-CTS mechanism remains the same
On top of the RTS-CTS, an optional relayed-RTS-CTS mechanism is added
Several procedural changes are needed in order to employ the relayed-RTS-CTS mechanism
All procedural changes in the relayed-RTS mechanism do not affect the existing constant values and timing parameters
The proposed solution may still be optimized for rare and extreme scenarios
Chin-Sean Sum, NICT

19. Required Changes to Legacy 802.11 (2/2) ~Frame Format~
Mar. 2010
Required Changes to Legacy (2/2) ~Frame Format~
Relay Control field (1 octet)
Relay Type, RT (2 bits)
00: Conventional RTS-CTS
01: Relayed RTS-CTS with 1 relay
10: Relayed RTS-CTS with 2 relays
11: Relayed RTS-CTS with 3 relays
Relay Instance, RI (2 bits)
Gives the current relay STA
Reserve (4 bits)
RE1 to RE4 (6 octets each)
Chin-Sean Sum, NICT

20. Mar. 2010
Conclusion
This presentation explores the seriousness of the mutated hidden terminal in af
This presentation proposes a solution to solve the ‘mutated’ hidden node problem
The solution requires minimum change in the legacy
Chin-Sean Sum, NICT

21. Appendix A Operating Range
Mar. 2010
Appendix A Operating Range
Urban
Low Power
High Power
Environment
100mW 4W
Transmitter
Information Data Rate (Rb)
2.50
Coding Rate
0.50
Spreading factor 1
Center Frequency (MHz)
Bandwidth (BW in MHz)
5.0000
Tx Antenna Gain (GT)
0.0
Tx Average Power (PT)
20.00
36.00
Receiver
Average Noise Power per Bit (N = xlog(Rb) )
-110.0
Rx Noise Figure Referred to the Antenna Terminal (NF)
8.0
Estimated Payload Eb/N0(S) at BER=10-6
Payload CNR
5.0
Implementation Loss(I)
1.0
Rx Antenna Gain (GR)
Sensitivity
Propagation Loss Index
2.5
Range (d in km)
0.47
1.70
Base station antenna height (hb in m)
1.00
30.00
Mobile station antenna height (hm in m)
Mobile station antenna height correction factor (ahm)
6.75
Path Loss (PL)
120.75
123.18
Minimum Rx Sensitivity Level (Smin)
-93.0
Rx Power Calculations
Link Margin (LM)
0.46
0.07
Chin-Sean Sum, NICT

22. Appendix B A Typical Extreme Case & Solution
Mar. 2010
Appendix B A Typical Extreme Case & Solution
Chin-Sean Sum, NICT

23. Appendix C An Alternative Solution
Mar. 2010
Appendix C An Alternative Solution
Chin-Sean Sum, NICT