1. Managing SCW regular pattern
July 2007
doc.: IEEE yy/xxxxr0
July 2008
Managing SCW regular pattern
IEEE P Wireless RANs Date:
Authors:
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Sangbum Kim, Samsung Electronics

2. July 2007
doc.: IEEE yy/xxxxr0
July 2008
Abstract
This contribution proposed a mechanism for controlling scalability in reservation of SCW
This contribution is related to the resolution of comment #436
Comment #436
Sangbum Kim, Samsung Electronics

3. Reservation of SCW in Draft v1.0
July 2007
doc.: IEEE yy/xxxxr0
July 2008
Reservation of SCW in Draft v1.0
BS schedules a SCW in active mode according to a regular pattern.
During its initialization stage, a new comer WRAN monitors the channel to discover neighboring WRANs and identifies their SCW regular patterns.
The new comer WRAN shall set its own regular pattern so that it does not overlap with the SCWs reserved by the discovered neighboring WRAN.
Contention-based & reservation-based
Sangbum Kim, Samsung Electronics

4. Problem on SCW regular pattern
July 2008
Problem on SCW regular pattern
If there is no vacant SCW slot for new comer, how can the new comer BS transmit its CBP packet?
A new value of SCW_Active_Repetition should be set;
In current draft, there is no mechanism to manage the value of SCW_Active_Repetition among BSs
Sangbum Kim, Samsung Electronics

5. Distributed management for Reservation of SCW
July 2008
Distributed management for Reservation of SCW
If all SCW slots are occupied, new comer BS secures its SCW regular pattern by contending a neighboring cell.
If new comer loses, it retries to contend in another SCW slot.
Otherwise, the target cell shall increase the period of its pattern as double and then share SCW slots with new comer.
New comer should try to contend a cell with the small period of SCW_Active_Repetition for fairness of latency performance.
If there is vacant SCW slots and the pattern of other cells is not disturbed, cell can reduce its regular pattern.
Sangbum Kim, Samsung Electronics

6. Exemplary process - No vacant SCW slot
July 2008
Exemplary process - No vacant SCW slot
Sangbum Kim, Samsung Electronics

7. July 2008
Suggested text changes for SCW regular pattern in ‘ CBP Packet Generation’
The reservation of SCWs facilitates the contention-free CBP transmissions among the neighboring WRAN cells sharing the channel, and it can be achieved by scheduling the regular SCW pattern such that it does not overlap with the SCW pattern of other neighboring WRANs. The procedure for that is as follows:
During the initialization stage, the WRAN monitors the channel to discover neighboring WRANs and identifies their SCW regular patterns. For instance, the regular SCW pattern can be identified by receiving a sequence of CBP packets from a neighboring WRAN.
If a WRAN indentifies another WRAN’s regular SCW pattern, it shall regard these SCWs as reserved and shall set its own regular pattern so that it does not overlap with the SCWs reserved by the neighboring WRAN.
Once the WRAN starts its own regular SCW pattern, it shall maintain this pattern for a number of super-frames specified by the SCWActive_Reservation_Period parameter.
Insert the following texts between line 36 and line 37
If necessary, a BS reserves its SCW regular pattern by contending on an active SCW slot occupied by a existing neighboring cell.
If the BS lose the contention, it retries to contend on another active SCW slot;
If the existing neighboring cell detects contention from other WRAN cells in a given SCW slot, it shall double the SCW_Active_Repetition value by giving up the contended slot in its reserved pattern.
Sangbum Kim, Samsung Electronics

8. July 2008
Conclusion
We proposed a mechanism to manage the period of SCW reservation through contention-based access mechanism which is already adopted in the current draft v1.0.
Flexibility and scalability in SCW reservation is allowed.
The proposed mechanism needs minimal change to MAC and no change to PHY.
Sangbum Kim, Samsung Electronics

9. July 2008
References
IEEE P802.22™/ DRAFTv1.0, Draft Standard for Wireless Regional Area Networks Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Policies and procedures for operation in the TV Bands
Sangbum Kim, Samsung Electronics