Clarification on ACK of Bandwidth Request
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16m-09/0180r1
Date Submitted:
2009-1-5
Source:
Gang Shen, Kaibin Zhang, Jimin Liu, Xiaobing Leng
Alcatel Shanghai Bell
E-mail:
[email protected]
Venue:
Re: Call for Comments on Project 802.16m System Description Document (SDD)
Base Contribution:
N/A
Purpose:
To be discussed and adopted by TGm for the 802.16m SDD
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Acknowledgement of bandwidth request in 16m SDD
• 16m SDD allows acknowledgement
of the reception of bandwidth request
1
Acknowledgement for BR indicators
2
BS
BW REQ message
3
Acknowledgement for BW REQ
4
– Acknowledge of BR enables MS to
restart BR to recover quickly from a
BR failure
•
UL grant for BW REQ message
UL grant
UL scheduled transmission with optional
piggybacked bandwidth request
However, it is not necessary for ABS to response every BR with ACK
considering the extra overhead
5
MS
– In SDD it states “In step 2 and step 4,
ABS may send message to
acknowledge the reception Status”
(line 20 of page 110)
Bandwidth Request indicator
ACK of BR in Step 2
• The BR procedure could be a 5-step regular procedure (step 1 to 5) or an
optional 3-step one (step 1,4 and 5).
– Step 2 is only used in the regular procedure.
– Upon detection of the ranging code, the ABS shall issue a CDMA Allocation
IE right now
• It is not necessary for ABS to send ACK in step 2
– If the AMS receives a CDMA Allocation IE with the code matching its own, it
knows BS has correctly received the BR.
– So Extra ACK together with CDMA Allocation IE in step 2 is not necessary
• It is suggested to remove ACK of BR in step 2
ACK of BR in Step 4
• Step 4 is for UL grant, where ABS allocates the bandwidth for AMS
• It is also not necessary for extra ACK in Step 4.
– If MS receives the UL grant, thus it knows BS has correctly received the BR.
So extra ACK in step 4 together with UL grant is not necessary
– ACK should follow the procedure step 3 and before the step 4 to let AMS be
informed early
• If ABS allocates UL grant immediately, it is not necessary to send ACK of
BR
– The BS should response the acknowledgement only when needed
– ACK is useful when BS receives BR but can not allocate the bandwidth
immediately
• It is suggested to change to
– “ABS send out ACK following Step 3 if ABS does not send UL grant within a
period (e.g. next frame).”
AMS Activities to Restart BR
• SDD has not mentioned AMS activities to restart BR
• It is suggested to change to
– “If MS does not receive UL grant or ACK within a pre-defined period
(e.g. next frame), it then restarts the bandwidth request”
Suggested Remedy
[Change the following texts in line 20 of page 110 as indicated]
“Following Step 3, ABS may acknowledge the reception if ABS can not
schedule UL grant to a specified AMS immediately. If MS does not receive
UL grant or ACK within a pre-defined period (e.g. next frame), it then restarts
the bandwidth request. BS and MS may coordinate to determine the predefined period.”
[Change the figure51 on page 110as indicated]
Bandwidth Request indicator
1
2
UL grant for BW REQ message
3
Acknowledgement for BW REQ
4
UL grant
UL scheduled transmission with optional
piggybacked bandwidth request
5
MS
BS
BW REQ message