Proposal for differentiating bandwidth request based on
service class and retry attempts
Proposal for differentiating bandwidth request based in service
class and retry attempts
Document Number: IEEE S802.16m-09/1321r4
Date Submitted: 2009-07-10
Source:
Abhay Karandikar
B. Srinadh
Prateek Kapadia
Harshad Maral
E-mail : karandi@ieee.org
Telecom Center of Excellence, Indian Institute of Technology (Bombay)
Kiran Kuchi
J. Klutto Milleth
CeWiT
Shatidev Mohanty
Yang Xiangying
Intel
Re:
Call for Comments on IEEE 802.16m-09/0010r2 IEEE 802.16m Amendment text/Area: Chapter 15.2.11.1.1. (Bandwidth Request)
Purpose: To provide the details of the C802.16m-09/1321 : Proposal for differentiating bandwidth request based on service class and retry
attempts
Notice:
This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the
“Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained
Differentiation & Prioritization in Contention-based
Random Access for Bandwidth Request (BR)
• Our proposal: Method for Differentiation &
Prioritization in Content-based BR
• Present status of standardization:
– Sections:
• AWD 80216m-09_0010r2 Section 15.2.2 Bandwidth
Request Procedure
• AWD 80216m-09_0010r2 Section 15.2.11.1.1
Contention-based random access bandwidth request
• AWD 80216m-09_0010r2 Section 15.3.9.2.5 Bandwidth
request channel
– Need for Differentiation by Service Class & Priority is
identified, but Method for Differentiation & Prioritization is
TBD
Goals for BR Contention Differentiation &
Prioritization
• Lower UL Grant Delay ==>> Smaller Contention
Window sizes for Flows on Higher Service Class
• Lower Average UL Grant Delay ==>> Smaller
Contention Window sizes for Flows with more BR retry
attempts
• Values for Contention Window need to be varied
depending on Load
– More Load ==>> Higher window sizes reduce
Contention
– Less Load ==>> Lower window sizes reduce UL
Grant Delay
Key Elements of Proposal




Define Connection Priority (CP) for each
contending Service Flow
CP is a function of Service Class & Number of
Retries (BR collisions) so far
CP initialization parameters sent on DSA-REQ
or DSC-REQ
CP parameters:

Service Class

Initial / Maximum Window Size

Window Scaling Factor
Example 1: Truncated Binary Exponential Backoff
Service Class
0 (High)
1
2
3 (Low)
Initial Window
1
2
4
4
16
128
256
512
Scaling Factor
2
2
2
2
Window Size (Retry #1)
2
4
8
8
Window Size (Retry #2)
4
8
16
16
Window Size (Retry #4)
16
32
64
64
Window Size (Retry #8)
16
128
256
256
Window Size (Retry #12)
16
128
256
512
Window Size (Retry #16)
16
128
256
512
Max Window
Example 2: No Backoff with Priority
Service Class
0 (High)
1
2
3 (Low)
Initial Window
16
24
48
64
Max Window
16
24
48
64
1
1
1
1
Window Size (Retry #1)
16
24
48
64
Window Size (Retry #2)
16
24
48
64
Window Size (Retry #4)
16
24
48
64
Window Size (Retry #8)
16
24
48
64
Window Size (Retry #12)
16
24
48
64
Window Size (Retry #16)
16
24
48
64
Scaling Factor
Connection Priority Data in DSx-REQ

Service Class: 4 bit

Initial Window Size: 8 bit

Maximum Window Size: 11 bit

Window Scaling Factor: 4 bit
---------------------------------Start of the Text (page 64 line 38)------------------------------------15.2.11.1.1 Contention-based random access bandwidth request
AMS considers the BR was failed and may restart the BR procedure upon one of the
following conditions:
1)received a Negative-ACK; or
2)the BR timer expires.
When AMS restarts BR procedure, the AMS shall randomly select a number within its
backoff window specified by the connection priority. This random value indicates the
number of contention transmission opportunities that the AMS shall defer before
transmitting. The connection priority is defined by the tuple of contention window
parameters and the number of retries. The ABS transmits initial connection priority
parameters - initial and maximum window sizes and backoff window scaling factor - in
DSx-REQ and/or DSx-RSP messages.
Corresponding DSx-REQ and DSx-RSP message parameters:
Connection priority/Service class4 bitsInitial window size11 bitsMaximum window size8
bitsContention window scaling factor4 bits