Doc.: IEEE 802.22-08/0209r4 Submission Oct. 2008 Sangbum Kim, Samsung Electronics Slide 1 Managing...

doc.: IEEE 802.22-08/0209r4

Submission

Oct. 2008

Sangbum Kim, Samsung ElectronicsSlide 1

Managing SCW Regular PatternIEEE P802.22 Wireless RANs Date: 2008-10-24

Name Company Address Phone email Sangbum Kim Samsung Electronics Korea +82 31 279 7092 [email protected]

Cheng Shan Samsung Electronics Korea +82 31 279 7557 [email protected]

Euntaek Lim Samsung Electronics Korea +82 31 279 5917 [email protected]

Baowei Ji Samsung Telecom.

America USA +1-972-761-7167 [email protected]

Authors:

Notice: This document has been prepared to assist IEEE 802.22. 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 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf 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 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at [email protected].>

doc.: IEEE 802.22-08/0209r4

Submission

Abstract

• This contribution proposed a mechanism for controlling scalability in reservation of SCW.

• It is expected that this contribution can resolve the scalability problem as pointed out in comment #431 and #436.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

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.

Oct. 2008


SCW_Active_Repetition

SCW in active mode

WRAN 1

WRAN 2

WRAN 3

WRAN 3 monitors the channel

Regular pattern

doc.: IEEE 802.22-08/0209r4

Submission

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?– In order to resolve this problem, the value of SCW_Active_Repetition

should be set not to be fixed and adaptively be changed according to the number of co-channel WRAN cell.

– From this reason, a mechanism to control the reservation period is needed in IEEE802.22.

Oct. 2008


Cell 1, 2, 3 and 4 haveSCW_Active_Repetition of 4

2 3 4 1 2 3 4 1 2 5 4 1 2 3 4 1

SCW_Active_RepetitionCell ID

1

2

3

4

5

4

4

4

4

?

1

4

1

3

2

New comer

5

doc.: IEEE 802.22-08/0209r4

Submission

Distributed Management for Reservation of SCW (1/2)

• 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.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

Distributed Management for Reservation of SCW (2/2)

• If there is vacant SCW slots, WRAN can reduce the period of its pattern according to the following rules.

• If there are multiple WRANs trying to occupy the same pattern of vacant slots, the WRANs shall resolve the occupation through contention;

• If necessary, the winner of the vacant slots shall release its previously occupied slots to maintain a regular pattern;

– For example, if the vacant slots are not located at the middle of its pattern cycle, WRAN can’t occupy the vacant slots because of its regular pattern.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

Exemplary Process – There is no vacant slots

Oct. 2008


Initially, cell 1, 2, 3 and 4 haveSCW_Active_Repetition of 4

2 3 4 1 2 3 4 1 2 5 4 1 2 3 4 1

5

(1) Contention: 3 wins, 5 loses(2) Retry contention: 3 loses, 5 wins(3) Cell 3 changes SCW_Active_Repetition from 4 to 8


1

2

3

4

5

4

4

4 à 8

4

8

1

5

(1) (2)

(3)

4

1

3

2

New comer

5

doc.: IEEE 802.22-08/0209r4

Submission

Exemplary Process – A WRAN is out (1/2)

• As cell 2 is out, cell 3 and 5 can try to reduce their SCW period.

Oct. 2008


5 4 1 3 4 1 5 4 1 3 4 1


1

2

3

4

5

4

out

8

4

8

1

4

1

3

2 5

doc.: IEEE 802.22-08/0209r4

Submission

Exemplary Process – A WRAN is out (2/2)

Oct. 2008


5 4 1 3 4 1 5 4 1 3 4 11

5

3

5 4 1 5 3 4 1 5 4 1 5 3 4 11

5 4 1 5 3 4 1 5 4 1 5 3 4 11

3

5 3 4 1 5 3 4 1 5 3 4 1 5 3 4 11


1

2

3

4

5

4

-

4

4

4

(1) Since the period of new vacant pattern is 4, cell 3 and 5 want to switch their pattern to the vacant pattern.(2) Contention: 5 wins, 3 loses(3) Cell 5 occupies new pattern

(4) Cell 5 leaves the current pattern

(5) Cell 3 identifies vacant SCW slots that can reduce the cell its period by half(6) Try contention. Since there is no competitor in this case, cell 3 occupies the vacant slots and then its period decreases

Period values after the process

Step 1

Step 2

Step 3

Step 4

doc.: IEEE 802.22-08/0209r4

Submission

Additional improvement (1)

• Fast identification of SCW pattern– WRANs need to monitor its channel until it identifies the reservation

period of neighboring WRANs.– In order to quickly identify SCW pattern of neighboring WRANs, the

beacon MAC header includes the value of SCW_Active_Repetition or the number of frame from the current slot to the slot in which next CBP packet will be transmitted.

Oct. 2008


Syntax Size Notes

Type 1 bit 0: Type indicating the value of period 1: Type indicating the location of next SCW slot directly

Value 4 bits the value of SCW_Active_Repetition or the number of frame from the current slot to the slot in which next CBP packet will be transmitted.

doc.: IEEE 802.22-08/0209r4

Submission

Additional improvement (2)

• Guaranteeing minimum latency performance for CBP transmission by adopting an admission control – For it, IEEE802.22 standard shall present a threshold on minimum latency

performance.– In the case that it is difficult to maintain the minimum latency

performance by new comer, the contention by new comer is limited.– Because new comer identifies the period of neighboring WRANs, new

comer can recognize whether it is possible for it to contend or not.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

Suggested text changes for SCW regular pattern in ‘6.21.2.1.2 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.• WRAN can set up or change its current SCW pattern by occupying available vacant slots.• If there are multiple WRANs trying to occupy the same pattern of vacant slots, the WRANs shall resolve the

occupation through contention; if necessary, the winner of the vacant slots shall release its previously occupied slots to maintain a regular pattern;

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

As a resolution of comment #431

• In comment #431, two drawbacks are described as follows:

1) Scalability - the reservation period (assumed to be fixed) limits the maximum number of co-channel WRAN cell to communicate using CBP

The proposed mechanism provides the scalability to change the reservation period according to the number of co-channel WRAN cell.

2) Latency - if the reservation period is set to be too large, the latency for inter-WRAN communications will be large too. If it is too short, not many WRAN cells can be accommodated

In the proposed mechanism, latency performance depends on the number of co-channel WRAN cell. Alternatively, if an admission control is adopted for the contention, we can maintain the QoS of latency.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission

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.

• By the proposed mechanism, flexibility and scalability in SCW reservation is allowed.

• The proposed mechanism needs minimal change to MAC and no change to PHY.

Oct. 2008


doc.: IEEE 802.22-08/0209r4

Submission Slide 15

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

Oct. 2008

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