IEEE C802.16m-08/1031
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Uplink Data Transmission for IEEE 802.16m
Date
Submitted
2008-09-05
Source(s)
Yih-Shen Chen, Kelvin Chou, I-Kang Fu and
Paul Cheng
Yihshen.Chen@mediatek.com
Kelvin.Chou@mediatek.com
IK.Fu@mediatek.com
MediaTek Inc.
Re:
MAC: Data Plane; in response to the TGm Call for Contributions and Comments 802.16m-08/033 for
Session 57
Abstract
This contribution discusses grant allocation and scheduling for uplink data transmission
Purpose
To be discussed and adopted by TGm for the P802.16m SDD.
Notice
Release
Patent
Policy
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IEEE C802.16m-08/1031
Uplink Data Transmission for IEEE 802.16m
Yih-Shen Chen, Kelvin Chou, I-Kang Fu, and Paul Cheng
MediaTek Inc.
1. Introduction
In 802.16 system, the uplink transmission starts from the request-and-grant negotiation. Mobile station (MS)
may establish multiple uplink connections with its serving base station (BS), and each connection has its
specific quality of service (QoS) parameter set. Based on the QoS parameters and buffer status, the MS makes
transmission request via contention-based or polling-based bandwidth request (BR) attempt. And then, the BS
grants uplink transmission resource to the MS. In legacy system, the BR is made per connection and the grant is
per terminal.
SRD states that IEEE 802.16m shall support different QoS levels for different services [1]. However, in the
legacy system, there is no scheduling rule commonly known between BS and MS. The BS performs its specific
scheduling algorithm to distribute the UL bandwidth between multiple connections/BSs, and the BS has to
“guess” the allocation rule by itself. Consequently, there would be a serious QoS issue when MS sends multiple
BRs because the MS is not aware which connections are honored by the BS and how the bandwidth are shared
among the connections.
Four scheduling types are defined for 802.16 legacy systems, including: unsolicited grant service (UGS), realtime polling service (rtPS), non-real-time polling service (nrtPS) and best effort services (BE). For UGS and
rtPS, BS periodically grants UL transmission bandwidth. For nrtPS and BE, BS grants UL transmission
bandwidth upon the reception of BRs. Since there is no strict time constraint between the request and grant
messages, BS may possibly collect multiple connection requests to handle. In legacy system, the grant message
only includes two parameters: Basic CID and transmission attribute. As mentioned, the grant is given per
terminal. Without any explicit indication, it’s hard for the MS to efficiently multiplex packets from multiple
connections into a single transmission block.
In the contribution, for finer QoS control, we propose a 2-step uplink resource allocation scheme for IEEE
802.16m system. In the 2-step scheme, BS announces the uplink bandwidth allocation by class-based grant
message and MS multiplexes packets from multiple connections by pre-defined scheduling principles.
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IEEE C802.16m-08/1031
2. Class-based uplink resource grant
The proposed grant message consists of class indication as well as Basic CID and transmission attribute. The
class indication is used to specify what kinds of scheduling type are to be transmitted in the uplink resource.
An uplink resource grant may be used to multiplex multiple connections from a single or multiple scheduling
types. Therefore, it is possible to use a bitmap for the class indication, where each bit represents a specific
scheduling type. The resource allocation and multiplexing of connections from different scheduling types is up
to BS’ implementation. BS makes the allocation based on connections’ QoS requirements and BRs. Noted that,
the time latency and BLER requirements are very different for data-plane and control-plane (MAC
management messages) transmissions; therefore, it is recommended not to multiplex them into a single UL
resource block.
3. Uplink scheduling principles
Within the same scheduling type, pre-defined scheduling principles are applied by MS. In this contribution, we
recommend that some common uplink scheduling rules shall be defined for 802.16m systems. These
scheduling rules are used to fulfill the QoS requirements. In SRD, it is said that IMT-Advanced QoS
requirements shall be supported including end-to-end latency, throughput, and error performance [1]. To meet
the requirements, there are many applicable scheduling rules. Priority-based uplink scheduling rule with
minimum rate is one of the possible algorithms. In the priority-based scheduling scheme, the low-latency
connections may be assigned with a higher priority to utilize uplink bandwidth so as to reduce transmission
delay while the minimum-rate parameter may be used to guarantee a sustainable throughput. The detail design
of pre-defined uplink scheduling rules is FFS.
4. Proposed Text for SDD
[Add section 10.4 uplink transmission scheduling in TGm SDD[1], ]
------------------------------- Text Start ---------------------------------------------------------------------------------10.4 uplink transmission scheduling
For QoS control, a 2-step uplink resource allocation scheme is considered in IEEE 802.16m system. In the 2step scheme, BS announces the uplink bandwidth allocation by class-based grant message and MS multiplexes
packets from multiple connections by pre-defined scheduling principles. The grant message consists of class
indication as well as Basic CID and transmission attribute. The class indication is used to specify what kinds of
scheduling type are to be transmitted in the uplink resource. And, for uplink transmission, some common uplink
scheduling rules shall be defined for 802.16m systems so as to fulfill the IMT-Advanced QoS requirements.
------------------------------- Text End -----------------------------------------------------------------------------------[1] IEEE 802.16m-08/003r4, “The Draft IEEE 802.16m System Description Document”
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