IEEE C802.16mUL -08_705r2
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Uplink Power Control of 16m
Date
Submitted
2008-07-07
Source(s)
JueJun Liu
Xuehuan Wang
Tao Qian
Jin Yu
Jianfei Tong
Jia Lin
Huawei Technologies Co., Ltd.
Xin Su
Tsinghua University
Re:
E-mail:linjia@huawei.com
E-mail: suxin@mail.tsinghua.edu.cn
IEEE 802.16m-08/024: Call for Comments and Contributions on Project 802.16m System
Description Document (SDD).
Target topic: “Power control”.
Abstract
Proposal for Soft Frequency Reuse for interference mitigation.
Purpose
For review and discussion in the TGm
Notice
Release
Patent
Policy
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 herein.
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
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contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16.
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
<http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
Uplink Power Control of 16m
Juejun Liu, Xuehuan Wang, Tao Qian, Jin Yu, Jianfei Tong, Jia Lin, Xin Su
1 Introduction
Traditional transmission power control (TPC) is a key technique to achieve link adaptation. In OFDMA system,
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IEEE C802.16mUL -08_705r2
TPC is considered as a method for decreasing interference to other users in neighbor sector. This paper presents
TPC schemes for 16m uplink physical channels.
2 TPC for UL data channel
Open loop TPC shall be supported for the UL channel with an initial value for initial data transmission. BS shall
broadcast specific system parameters in the BCH for open loop TPC adjustment, e.g. BS transmission power
and UL noise and interference level of each sub zone etc. MS can initialize its UL transmission power according
to these specific parameters and UL resource allocation.
The BS shall be capable of providing accurate power measurements of the received signal from MS. This value
can then be compared with a target level, and the resulting offset can be feedbacked to the MS through UL
power control signaling. For interference mitigation, MS shall also adjust its UL data transmission power
according to overload indication of sub zone from neighbor sector.
2.1 Assignment of Transmission Powers of New and Retransmitted Packets
BS may assign transmission power of UL new packets and retransmitted packets through DL control channel.
Assigned transmission power is associated with assigned MCS and target BLER.
For providing improved transmission performance, power boost can be used for HARQ retransmission. BS can
negotiate different power boost value for different service with MS to provide different requirements of service
when creating service connection.
Power boost indicator can be included in the UL resource assignment message to indicate whether to use power
boosting for UL HARQ retransmission.
2.2 TPC procedure
The reference transmission power of the UL data channel is decided by MS via open loop adjustment. Then, the
MS can be informed the initial transmission power offset associated with assigned MCS and target SNR using
the downlink control channel.
Transmission power of MS is equal to reference transmission power plus initial transmission power offset.
Neighbor sectors measure the received interference power over multiple non-overlapping frequency partitions
which is called sub zone. If the interference power level exceeds the pre-defined threshold, neighbor sector will
transmit an overload indicator signal per sub zone. BS can broadcast multiple overload indicators for multiple
sub zones simultaneously.
Therefore, MS transmits the data with the decreasing transmission power by one step size as long as neighbor
sector feedbacks a “Overload” signal, which indicates that the transmission power should be reduced. Otherwise,
MS may transmit the data with the increasing transmission power by one step size. MS shall select the overload
indicator signal from the frequency partition, over which UL resources are assigned to MS.
Through above procedure, inter-sector interference can be mitigated effectively.
BS also may adjust transmission power of MS through MAC management. MS shall set its transmission power
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IEEE C802.16mUL -08_705r2
according to adjust value.
2.3 Measurement of Interfering Power from neighbor sector
Each sector shall estimate the average amount of interference of entire bandwidth relative to thermal noise
power (referred to as IOT of entire bandwidth) experienced by this sector from terminals in other sectors, where
the thermal noise level is measured during the Uplink Silence Interval. Meanwhile, each sector shall estimate
the average amount of interference of each sub zone relative to thermal noise power (referred to as IOT of sub
zone) experienced by this sector from terminals in other sectors. Each sector broadcasts an indication of its
interference measurements that can be used by MSs in other sectors. For simplicity, the following description
assumes that a single load indicator bit is used for providing interference information. Each sector shall set its
average overload indication (OI) of entire bandwidth or average overload indication of sub zone as follows:
OI m , s (n)  1, if IoTmeasure,m, s (n)  IoTt arg et
m: sector index
s: sub zone index
n: measure interval
Illustration of sub zone:
sub zone1
sub zone2
sub zone3
System Bandwidth 10MHz
sub zone4
AOI: Average OI over entire bandwidth
SOI: Average OI over sub zone
sub zone5
OI transmission format
AOI
sub zone6
SOI1
SOI2
SOI3
SOI4
SOI5
SOI6
IoT per sub zone or IoT over entire bandwidth computation:
IoTs 
I
k
k ,s
  02
 02
 02  Ws  N 0
I
k ,s
denotes the thermal noise power for sub zone s
denotes neighbor sectors interference power over sub zone s.
k
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IEEE C802.16mUL -08_705r2
k: interfering sector index
OI of entire bandwidth can be used as power adjustment information for MSs that operate in hopping over entire
bandwidth mode.
OI of sub zone can be used as power adjustment information for MSs that operate in hopping over local sub
zone mode.
Different OI information can provide accurate interference estimate for different hop mode.
2.4 Transmission of power control indication
2.4.1 Transmission of initial transmission power value
Initial transmission power value shall be included in UL resource assignment message, which is transmitted
over DL control channel within one subframe.
2.4.2 Transmission of power correction value
BS may send dedicated power control MAC management message to adjust transmission power of MS.
2.4.3 Transmission of Overload indicator
DL overloads indicator channel carries overload indicator information for each sub zone and entire bandwidth.
They are broadcasted over the air link per super frame/frame/sub frame (FFS). DL overloads indicator channel
has larger coverage than DL traffic and penetrates far into neighbor sector. Illustration is as following:
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IEEE C802.16mUL -08_705r2
Sector 2
Sector 1
Traffic
coverage
MS
UL Data
Overload
Indicator
coverage
Sector 3
Overload indicator from neighbor sector
3 TPC for UL control channel
The reference transmission power of the UL control channel is decided by MS via open loop adjustment.
Initial transmission power of UL control channels shall be equal to reference power plus power offset.
Different power offset setting shall be used for different UL control channels.
3.1 TPC for UL initial ranging channel
Transmission power of UL ranging channel is equal to reference transmission power plus power offset of UL
ranging channel. Power offset of UL initial ranging channel is FFS.
During UL initial ranging, a pre-determined power step size and wrap back scheme shall be used.
3.2 TPC for UL CQI channel
Transmission power of UL CQI channel is equal to reference transmission power plus power offset of UL CQI
channel. Power offset of UL CQI channel is FFS.
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IEEE C802.16mUL -08_705r2
3.3 TPC for UL ACK channel
Transmission power of UL ACK channel is equal to reference transmission power plus power offset of UL
ACK channel. Power offset of UL ACK channel is FFS.
3.4 TPC for UL bandwidth request channel
Transmission power of UL BR channel is equal to reference transmission power plus power offset of UL BR
channel. Power offset of UL BR channel is FFS.
4 Conclusion
This paper presented TPC schemes for 16m uplink physical channels. In particular, we propose applying the
overload indicator of sub zone and overload indicator of entire bandwidth from surrounding neighbor sectors to
control the transmission power of MS for mitigating inter-sector interference.
5 Proposed Text
The following text is proposed to be captured in the IEEE 802.16m system description document (SDD) [1].
================================= Start of Proposed Text ==============================
X.x.x Uplink Power Control
Add content of previous chapter 2 and chapter 3 into this section
==================================== End of the Text ================================
6 References
[1] 80216m-08_003r2 SDD
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