C80216m-08_214
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
16m Downlink Common Pilot Structure for TDM Control Structure
Date
Submitted
2008-03-10
Source(s)
Zhigang Rong, Yunsong Yang
Jung Woon Lee, Young Hoon Kwon
Yang Tang, Anthony Soong
Jianmin Lu
Huawei
E-mail: zrong@huawei.com
Re:
IEEE 802.16m-08/005: Call for Contributions on Project 802.16m System Description Document (SDD).
Target topic: “Pilot Structures as relevant to downlink MIMO”.
Abstract
This contribution proposes a common pilot structure supporting the enhanced TDM based control
structure in a mini-frame.
Purpose
For discussion and approval by TGm
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 herein.
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C80216m-08_214
Objectives
• In contribution IEEE C802.16m-08/211, we
described an enhanced TDM based control
structure in a mini-frame
• In this contribution, we describe a common pilot
structure supporting this enhanced TDM based
control structure in a mini-frame
2
C80216m-08_214
Proposed Control and Data Multiplexing
Scheme within a Data Mini-frame
• Control zone occupies x subcarriers
in the first 2 OFDM symbols
Mini-frame
OFDM
Symbol
– To gain the benefits of TDM based
control structure
RB
• Data zone occupies the remaining
usable subcarriers in the first 2
OFDM symbols
• 3rd to 6th OFDM symbols are used
for data zone
– Cleaner design for the data zone and
pilot structures
Frequency
– To enhance bandwidth and power
efficiency by adding FDM
– The Control zone size (x) is
modulated on Common Pilots in the
control zone
0
1
2
3
4
5
Time
Common Pilot 1
PCBCH
DGCH
Dedicated Pilot 1
Common Pilot 2
Data
DHACH
Dedicated Pilot 2
FIG. X: Example of Downlink Control Structure
3
C80216m-08_214
Proposed Common Pilot Structures
• 1st and 2nd Tx Antenna Common Pilots always provided in the
control zone (if BS supports at least 2 Tx antennas)
– Modulated with Control zone size information
– Used for channel measurement and coherent demodulation for both
localized and diversity resource allocation
• 3rd and 4th Tx Antenna Common Pilots may be provided in the
control zone based on demand
– Absence or presence as indicated
– The BS may group MSs that can benefit from the 3rd and 4th Tx
antennas into some mini-frames so that the BS can turn off the 3rd and
4th Tx antenna common pilots in the other mini-frames
• No Common Pilots provided in the data zone
– Optimized the common pilots on the first 2 antennas for average users
and schemes
– Use dedicated pilots to address user-specific needs
– For MBS/SFN, use dedicated pilots as SFN common pilots
4
C80216m-08_214
Summary of Simulation Results
(Details provided in the Appendix)
• Comparison of channel estimation loss @ 10-1 PER (with one
transmission) relative to idealized channel estimation between the
proposal and 16e Band AMC
• Ped. B, 3/30/120 kmph, 1x2 antennas
• Pilot overhead
– 16e Band AMC : 1/9 with 2.5 dB pilot boost
– TDM Pilot: 2/(9*6)=1/27 with 3dB pilot boost
• Conclusion: with significant lower pilot density, TDM common pilot
scheme achieves almost same performance as in 16e Band AMC
Channel Estimation Loss @ 10% PER (dB)
Mobile Speed
Pilot Tones in First 2 OFDM
Symbols (New Design)
Pilot Tones in All OFDM
Symbols (Band AMC)
3 km/h
0.8
0.6
30 km/h
0.8
0.7
120 km/h
0.8
1
5
C80216m-08_214
Benefits of the Proposals
• Design of Common Pilots that is optimized for
average users and without burdening these users
with unnecessary pilot overhead
– Additional dedicated pilots are provided per user on a needed
base
– Optimized pilot overhead design for every user
• Separating the Common Pilots from the data zone
gives the system flexibility to implement advanced
techniques such as various CL-MIMO/BF, various OLMIMO, SFN for MBS and Paging, and schemes for
high mobility or long delay spread
6
C80216m-08_214
Text Proposal
Insert the following text in Chapter 11 (Physical Layer):
11.Z Downlink Pilot Structures
11.Z.1 Common Pilots
For TDM-based downlink control/data multiplexing scheme:
The common pilots for the 1st and 2nd transmit antennas are always
provided (in a diversity fashion) in the control zone in a data miniframe, if the BS supports at least 2 transmit antennas.
The common pilots for additional transmit antennas are provided (in a
diversity fashion) in the control zone in a data mini-frame based on
needs, if the BS supports more than 2 transmit antennas. The
absence or presence of the common pilots for the additional transmit
antennas is indicated by the BS.
There is no common pilots provided in the data zone. Instead, the
dedicated pilots are provided based on needs in each specific
resource block. For MBS/SFN transmission, dedicated pilots are
used as SFN common pilots.
7
C80216m-08_214
Appendix - Simulation Results
8
C80216m-08_214
Simulation Parameters for the New Proposal
•
•
•
•
•
•
•
•
Carrier frequency: 2 GHz
System BW: 10 MHz
Ped B. with 3km/h, 30km/h and 120km/h
Channel coding: Turbo code
Antenna Configuration: 1x2
Packet size: 384
Modulation and coding: QPSK
Resource Allocation: 4 symbols * 5 subchannel (1 subchannel = 18
subcarriers)
• Effective coding rate: 0.5333
• Pilot tone is boosted with 3dB over data tone and located every 9th
subcarrier on first 2 OFDMA symbol
• Channel estimation (MMSE-CE4)
– MMSE-based CE on frequency domain with filter length 4
– MMSE-based CE on time domain with 4 OFDM symbols (2 in
current + 2 in next)
9
C80216m-08_214
Simulation Results
FER (Nep=384, QPSK, Ped. B 3km/h)
Ideal CE
MMSE-CE
1
FER
0.1
0.01
0.001
-2
-1
0
1
2
3
4
5
6
7
8
9
SNR
10
C80216m-08_214
Simulation Results
FER (Nep=384, QPSK, Ped. B 30km/h)
Ideal CE
MMSE-CE
1
FER
0.1
0.01
0.001
-2
-1
0
1
2
3
4
5
6
7
8
9
SNR
11
C80216m-08_214
Simulation Results
FER (Nep=384, QPSK, Ped. B 120km/h)
Ideal CE
MMSE-CE
1
FER
0.1
0.01
0.001
-2
-1
0
1
2
3
4
5
6
7
8
9
SNR
12
C80216m-08_214
Simulation Parameters for 16e Band AMC
•
•
•
•
•
•
•
•
•
•
•
Carrier frequency: 2 GHz
System BW: 5 MHz
Ped B. with 3km/h
Channel coding: Turbo code
Antenna Configuration: 1x2
Packet size: 384
Modulation and coding: QPSK
Resource Allocation: 8 slots ( 4 symbols * 4 subchannel)
Effective coding rate: 0.5
Pilot tone is boosted with 2.5dB over data tone
Channel estimation
– MMSE-based CE on frequency domain
– MMSE on time domain (filter length is 6)
13
C80216m-08_214
Simulation Results
FER of Band AMC (Nep=384, QPSK, Ped. B 3km/h)
AMC (3km/h,IdealCE)
AMC (3km/h, MMSE_CE)
1.E+00
FER
1.E-01
1.E-02
1.E-03
-2
-1
0
1
2
3
4
5
6
7
8
9
SNR
14
C80216m-08_214
Simulation Results
FER of Band AMC (Nep=384, QPSK, Ped. B 30km/h)
AMC (30km/h,IdealCE)
AMC (30km/h, MMSE_CE)
1
4
1.E+00
FER
1.E-01
1.E-02
1.E-03
-2
-1
0
2
3
5
6
7
8
9
SNR
15
C80216m-08_214
Simulation Results
FER of Band AMC (Nep=384, QPSK, Ped. B 120km/h)
AMC (120km/h,IdealCE)
AMC (120km/h, MMSE_CE)
1.E+00
FER
1.E-01
1.E-02
1.E-03
-2
-1
0
1
2
3
4
5
6
7
8
9
SNR
16