Reliable Multicast Broadcast Service Protocol Design
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE S80216m-08/1150
Date Submitted:
2008-09-17
Source:
Hung-Yu Wei, Ching-Chun Chou
Department of Electrical Engineering,
National Taiwan University
Chun-Yen Wang,
ichard Li,
ITRI
Voice:
E-mail:
[Telephone Number (optional)]
hywei@cc.ee.ntu.edu.tw
f95921098@ntu.edu.tw
ChunYen@itri.org
richard929@itri.org
Venue:
MAC aspect of enhanced MBS; in response to the TGm Call for Contributions and Comments 802.16m-08/033 for Session 57
Base Contribution:
IEEE C80216m-08/1150
Purpose:
To be discussed and adopted by TGm for use in the IEEE 802.16m
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Introduction: Reliable MBS
• Reliable MBS
– Provide reliable service for MBS
• Better QoS
– video downloading
– Advertisement
– System/application information broadcasting
– Protocol
• Feedback
– ACK
– NACK
• Re-transmission
– Combine with HARQ or ARQ
– Efficient feedback is essential for MBS
Reliable MBS Reception
• Feedback mechanism for reliability
• NACK schemes
– Busy Tone NACK / NACK-Preamble NACK
• p-% Reliability
• ACK schemes
– Periodic ACK / Polling ACK
• Network ←→Users
– Integrated Schemes
• Suitable solution for different goals and systems
NACK Design
• Reduce signaling cost
– Negative ACK would trigger retransmission
• Busy Tone NACK
– 1 MBS group uses 1 NACK code
• Just use CDMA code as example
– Non-CDMA code could still be used: IE or others
– MS sends the Busy Tone NACK if it does not
receive any data block
• 1 or more data loss would result in Busy Tone
– Easy implementation and low signaling overhead
– Synchronous & non-adaptive HARQ
Example: Busy Tone NACK
BS Downlink to MBS group (MS1, MS2, MS3)
data 1
data 2
data 2
data 3
Re-transmission
NACK
MS1
rx
rx
MS2
rx
rx
MS3
rx
rx
rx
NACK
NACK
NACK-preamble NACK
• 1 MBS group uses 1 NACK code
– Just use CDMA code as example
• Non-CDMA code could still be used: IE or others
• MS uses the NACK CDMA code to code the reception error
message
– If BS receives exactly 1 NACK, then it knows that an MBS data is not
received and which MS does not receive it.
– If BS receives more than 1 NACK, then it knows that the block is not
received in several MSs.
• Moderate signaling overhead
– Obtain more information than Busy Tone NACK
– Synchronous + Non-adaptive HARQ
Collision of IE
Still get NACKpreamble
NACK IE 1
NACK IE 2
Received NACK IE
NACK IE
p-% Reliable MBS
• Tradeoff between data reliability & retransmission
cost.
• Probabilistic Reliability
– Utilizing NACK characteristics
– Use the value of p to adjust the reliability level
– 100-% reliable MBS
• All lost data blocks are retransmitted
– p-% reliable MBS
• The BS would decide whether the lost data block is retransmitted
according to p
• Busy Tone NACK with p-% reliability
• NACK-preamble with p-% reliability
ACK Design
• Polling ACK
– BS (network) should poll the MSs for ACK
– On-demand polling
• Periodic ACK
– The MSs periodically report ACK to BS
– The length of the period and the time of reporting should be
preconfigured by the BS
• Information Element (IE) are used for ACK reporting
– Full information reporting for MBS
Integrating ACK with NACK
• ACK and NACK could be applied simultaneously
• Complete solution
– Different system goals or HARQ designs and QoS
requirements could be satisfied
Time period for periodic ACK
Periodic ACK with
cumulative info
BS data
busy tone NACK
BS data
Retransmission
Periodic ACK with
cumulative info
BS data
time
No busy tone NACK is transmitted
Proposed Text (I)
15.x.1 Reliable Multicast and Broadcast
The multicast/broadcast mechanism within the system should be able to provide
reliable transmission to all the MBS group members. The degree of reliability could
be adjusted according to contents of the MBS traffic flows. Reliable multicast and
broadcast operation is designed to provide better service in MBS. The HARQ
operation and feedback mechanism are needed to facilitate re-transmission and to
provide reliability.
15.x.1.1 P-Reliable MBS
To meet different levels of traffic flow requirements, the service reliability is
configurable. In P-Reliable MBS scheme, re-transmission of data blocks will be
conducted so that at least p% of packets will be correctly received.
15.x.2 ACK and NACK Design for Reliable MBS
Acknowledgement (ACK) and Negative Acknowledgement (NACK) are crucial for
reliable MBS operation. The group members within the same MBS group are able
to transmit feedback message simultaneously to report the delivery status of MBS
data blocks. The design criterions for the ACK and NACK should be considered
from the following aspects.
Proposed Text (II)
15.x.2.1Acknowledgement Feedback Latency
The way of ACK and NACK design could be classified into immediate
ACK/NACK, delayed ACK/NACK, and integrated scheme.
15.x.2.2 Immediate Acknowledgment Scheme
In immediate acknowledgment, the MS transmit the ACK/NACK immediately after
the transmission of BS data. The fast feedback is used for immediate retransmission
to enhance reliability of MBS.
15.x.2.3 Delayed Acknowledgement Scheme
In delayed acknowledgement, the ACK and NACK are sent after a certain period.
The delayed ACK/NACK should contain cumulative information within the
ACK/NACK period. The BS could poll the MBS group to gather reception states of
the MSs. The polling could be periodic or on-demand. The MS reports to the poll
and the BS uses the information for MBS configuration.
Proposed Text (III)
15.x.2.4 Integrated Scheme
The integrated scheme means that the operation of ACK and NACK contains both
the characteristics of the immediate and delayed acknowledgement. More than one
kinds of ACK/NACK may be used. ACK and NACK could be applied
simultaneously for different feedback latency acknowledgment.
15.x.2.5 Channel Access and Allocation for Acknowledgement
The ACK and NACK mechanism should be able to operate on specific
preconfigured channels. The number of preconfigured wireless channels could be
the same as the node number or less. If the BS receives one or more
acknowledgement indicating that certain data block is lost, the BS should trigger
the retransmission for the specific data.