1. IEEE P802.22 Wireless RANs Date: 2007-03-15
Month Year
doc.: IEEE yy/xxxxr0
March 2007
Overview of CBP
IEEE P Wireless RANs Date:
Authors:
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Carlos Cordeiro, Philips
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
March 2007
Introduction
The purpose of this presentation is to educate the WG on the CBP self-coexistence protocol adopted in the current Draft 0.2 spec
We detail the MAC aspect of CBP, while the PHY aspects were already presented and are available in document
Carlos Cordeiro, Philips
John Doe, Some Company

3. Month Year
doc.: IEEE yy/xxxxr0
March 2007
CBP Overview
CBP is fully controllable by the BS that decides who sends/listens and when to send/listen for CBP packets
The source of a CBP packet can be either a BS or CPE
CBP packets carry control information only (no data)
CBP can be used for communication and coexistence of WRANs on the same operating channel as well as across channels
CBP packets can be transmitted
Over the backhaul (not specified in the standard or in this presentation)
Over the air
Carlos Cordeiro, Philips
John Doe, Some Company

4. Case 1: Neighboring out-of-range BSs
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doc.: IEEE yy/xxxxr0
March 2007
CBP Usage Scenarios (1)
Case 1: Neighboring out-of-range BSs
BS A selects CPE A1 to send CBP packets
BS B selects CPE B1 to send CBP packets
CPEs A1 and B1 receives each other CBP packets and report to their BSs, this enables:
Network discovery
Spectrum etiquette (BSs may decide to switch channels)
Interference-free scheduling
Resource sharing (renting/offering, spectrum contention)
CPE B1
CPE A1
BS A
BS B
This situation may happen when BSs A and B belong to the same operator.
In this case, the operator would try to minimize the overlapping area, but some users would suffer from interference if no co-existence mechanism is in place.
Carlos Cordeiro, Philips
John Doe, Some Company

5. Case 2: Neighboring in-range (or collocated) BSs
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doc.: IEEE yy/xxxxr0
March 2007
CBP Usage Scenarios (2)
Case 2: Neighboring in-range (or collocated) BSs
The BSs can use the CPEs (A1 and B1) to transmit CBP packets, as in case 1
The BSs can choose to transmit the CBP packets
In this case, the BSs shall also use the Coexistence Window (at the end of the frame) to send the CBP packet
CPE B1
CPE A1
BS A
BS B
This situation may happen when BSs A and B belong to different operators.
Multiple operators will likely to place their BSs close to each other to reach the same set of consumers.
Carlos Cordeiro, Philips
John Doe, Some Company

6. CBP Packet Transmission
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doc.: IEEE yy/xxxxr0
March 2007
CBP Packet Transmission
Carlos Cordeiro, Philips
John Doe, Some Company

7. CBP Access during the SCW (1)
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doc.: IEEE yy/xxxxr0
March 2007
CBP Access during the SCW (1)
The CBP access during the Self-Coexistence Window (SCW) is contention-based
But, the contention parameters (Coexistence Backoff Start (CBS) and Coexistence Backoff End (CBE)) are fully controllable by the BS and sent in the UCD message
In transmit mode, the CPE/BS generates a contention window (CW) randomly between [0, CBS] and performs the backoff process as to access the medium
CW is used to reduce the collision probability amongst stations with CBP packets to transmit during the same SCW
Carlos Cordeiro, Philips
John Doe, Some Company

8. CBP Access during the SCW (2)
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doc.: IEEE yy/xxxxr0
March 2007
CBP Access during the SCW (2)
CW1=4
CW2=10
CW3=7
CBP packet Rx x
x+1
x+2
SCW at Frame i … Rx x
x+1
x+2
SCW at Frame i+1
CBP packet
CW2=7
CW3=4 … x
x+1
x+2
SCW at Frame i+2 Rx
CBP packet
CW2=4
CW1, CW2, and CW3 are backoff intervals
at closeby CPEs 1, 2, and 3
CBS = 16
Carlos Cordeiro, Philips
John Doe, Some Company

9. BS’ Selection of Transmitting CPEs
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March 2007
BS’ Selection of Transmitting CPEs
The BS decides which CPEs are to transmit CBP packets
While we believe this decision to be implementation dependent, we recommend the following mechanisms:
Based on CPE’s location information (being developed by Geolocation/Database tiger team)
Based on statistics reported by the CPE (e.g., PER)
Carlos Cordeiro, Philips
John Doe, Some Company

10. CBP-based Neighboring Network Discovery – Case 1
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doc.: IEEE yy/xxxxr0
March 2007
CBP-based Neighboring Network Discovery – Case 1
BS A selects CPE A1 to send CBP packets
BS B powers-up and scans the channels (but does not detect BS A)
CPE B1 powers-up and associates with BS B
BS B schedules CPE B1 to scan for CBP packets
B1 receives a CBP packet from A1 and reports to BS B
BS B discovers BS A
BS B schedules CPE B1 to send CBP packets
After that, BSs A and B can coexist through CBP and other mechanisms operating on top of it, e.g.
BS A and B can switch channels, or share the same channel using coexistence mechanisms
BS B
CPE B1
CPE A1
BS A
The same procedure can be used when BSs A and B operate in the same channel or in different channels.
Carlos Cordeiro, Philips
John Doe, Some Company

11. CBP-based Neighboring Network Discovery – Case 2
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doc.: IEEE yy/xxxxr0
March 2007
CBP-based Neighboring Network Discovery – Case 2
BS A selects CPE A1 to send CBP packets
BS B powers-up, scans the channels and detects BS A
BS B receives A’s SCH during the scanning process
BS B receives a CBP packet from A1
CPE B1 powers-up and associates with BS B
BS B can hear BS A and it decides to send CBP packets
BS A discovers BS B
BS A decides to send CBP packets
After that, BSs A and B can coexist through CBP and other mechanisms operating on top of it, e.g.
BS A and B can switch channels, or share the same channel using coexistence mechanisms
BS B
CPE B1
CPE A1
BS A
Carlos Cordeiro, Philips
John Doe, Some Company

12. CBP-based Coexistence Framework
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CBP-based Coexistence Framework
Comprised of four elements (see doc r1)
Spectrum etiquette
Interference-free scheduling
Dynamic resource renting and offering
Adaptive on demand channel contention
Carlos Cordeiro, Philips
John Doe, Some Company

13. After Reception of a CBP Packet
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After Reception of a CBP Packet
In case of a CPE
Report it to its associated BS
Future upstream bandwidth reservation requests can contain time allocation constraints
For example, a CPE can specify: “Give me 100Kb of airtime, but not between T1 and T2”
In case of the BS
Perform the CBP-based self-coexistence mechanisms, namely, spectrum etiquette, interference-free scheduling, dynamic resource renting and offering, and adaptive on demand channel contention
Information carried in the CBP packet can be used as the fall-back mechanism for frame synchronization in case GPS is not available, does not have coverage, etc.
Carlos Cordeiro, Philips
John Doe, Some Company

14. Under Consideration CBP was meant to be primarily a broadcast protocol
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doc.: IEEE yy/xxxxr0
March 2007
Under Consideration
CBP was meant to be primarily a broadcast protocol
If more reliability is required, an optional CBP-ACK could be included to confirm reception of transmitted CBP packet
Carlos Cordeiro, Philips
John Doe, Some Company

15. Month Year
doc.: IEEE yy/xxxxr0
March 2007
Conclusion
CBP provides a flexible means for WRANs to communicate and coexist
Controllable by the BS
Over the air or through the backhaul
On the same channel or in different channels
A comprehensive self-coexistence framework is defined based on CBP, which allows WRANs to coordinate and efficiently share resources
Carlos Cordeiro, Philips
John Doe, Some Company

16. Appendix March 2007 Month Year doc.: IEEE 802.22-yy/xxxxr0
Carlos Cordeiro, Philips
John Doe, Some Company

17. Performance Evaluation
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doc.: IEEE yy/xxxxr0
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Performance Evaluation
All aspects of the MAC have been implemented in OPNET
OPNET is considered the most well-reputated and reliable network simulation tool available today
In all simulations:
In case of quiet periods (QP), every CPE performs detection in all in-band channels (e.g., N-1, N, and N+1 in case of a single TV channel)
DFS model is implemented as per the requirements document
No fragmentation or packing
Some common simulation parameters
Superframe size = 12 frames, where Frame size = 40 ms
Packet size = 1 Kbyte
Detection time per TV channel = 13 ms
64-QAM rate 2/3 and Symbol time = 310 µs
Carlos Cordeiro, Philips
John Doe, Some Company

18. Month Year
doc.: IEEE yy/xxxxr0
March 2007
CBP/Synchronization
Evaluate the self-coexistence mechanisms of the proposed MAC
Synchronization
CBP in every frame
The number of overlapping cells are progressively increased
Up to 4 cells are simulated
BSs and CPEs start at random
Network is fully loaded and traffic is uniform
1 cell:
2 cells:
Carlos Cordeiro, Philips
John Doe, Some Company

19. CBP/Synchronization (cont.)
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doc.: IEEE yy/xxxxr0
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CBP/Synchronization (cont.)
3 cells:
4 cells:
Carlos Cordeiro, Philips
John Doe, Some Company

20. CBP/Synchronization (cont.)
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doc.: IEEE yy/xxxxr0
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CBP/Synchronization (cont.)
Network Synchronization Time
Local Drift Time
Carlos Cordeiro, Philips
John Doe, Some Company

21. CBP/Synchronization (cont.)
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CBP/Synchronization (cont.)
Simple scheduler
CBP together with Synchronization can provide significant performance improvements
Carlos Cordeiro, Philips
John Doe, Some Company