ieee 802.16m sounding channel designs document number: ieee c802.16m-09/0140r1 date submitted:...
DESCRIPTION
Design Considerations (1/2) ▪ 1. Sounding signals are not allowed to collide with original pilots which are allocated in various kinds of UL tile structures –If collision happens, qualities of channel estimations for data transmission would degrade and thus data recovery would be unreliable –Three types of tile structures for UL transmission 2 18x6 tiles and 1 6x6 tileTRANSCRIPT
IEEE 802.16m Sounding Channel Designs
Document Number: IEEE C802.16m-09/0140r1Date Submitted: 2009-01-08
Source: Chih-Yuan Lin ([email protected]), Pei-Kai Liao ([email protected] ), Yu-Hao Chang ([email protected]), Ciou-Ping Wu ([email protected]), and Paul Cheng ([email protected])
MediaTek Inc.
Venue: IEEE 802.16m-08/052: Call for Comments on Project 802.16m SDD (802.16m-08/003r6), Section 11.9.2.3 UL Sounding Channel.
Base contribution: N/A
Purpose: Propose to be discussed and adopted by TGm for the use in Project 802.16m SDD
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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OutlineOutline▪ Design considerations of sounding channel
▪ FDM sounding PHY structures
▪ Simulation results
▪ Summary
▪ Text proposal
▪ Appendix
Design Considerations (1/2)Design Considerations (1/2)▪ 1. Sounding signals are not allowed to collide with original pilots
which are allocated in various kinds of UL tile structures– If collision happens, qualities of channel estimations for data transmission
would degrade and thus data recovery would be unreliable– Three types of tile structures for UL transmission
• 2 18x6 tiles and 1 6x6 tile
Intersection Sounding signalscan only be allocatedin white-color tones
Intersection Sounding signalscan only be allocatedin white-color tones
Design Considerations (2/2)Design Considerations (2/2)▪ 2. Maximally maintain sounding pattern consistency between each DRU tile
(6x6)– Since sounding is designed based on 18x6 tile, sounding patterns in 6x6 tiles may vary
if we don’t carefully design– Sounding consistency is recommended to be maintained such that there is no need to
memorize several data mapping rules at MS
▪ 3. Cannot affect other users’ UL behaviors after allocating sounding signals– E.g., utilization of SFBC
18
6
6
Note: MS should memorize 3mapping rules for DRU when sounding mode is enabled
Sounding PHY Structure (1/1)Sounding PHY Structure (1/1)▪ Example of FDM sounding PHY structure
– Based on design considerations, we have following example of FDM sounding structure
• Frequency-direction decimation can be used for multiuser (or multi-antenna) sounding
Sounding signal
Freq
.
Time
Freq
.
Time
Simulation Results (1/6)Simulation Results (1/6)▪ Comparative sounding structures
Motorola’s Example Proposed FDM Example
Freq
.
Time
Freq
.
Time
CDM Example
Freq
.
Time
Freq
.
Time
One CDMA code
Freq
.
Time
Freq
.
Time
Simulation Results (2/6)Simulation Results (2/6)▪ Simulation parameters
– Number of users• 3 and 6
– Channel estimation: 2D-MMSE• Optimized to predefined velocity speed 15 km/hr• Optimized to predefined channel delay spread 5 us
– Channel model• PB 3 km/hr• VA 30 km/hr
– Performance metric• Channel estimation mean square error (MSE)• System throughput
– Code sequences of CDM• Length-6 Zadoff-Chu sequences
– 5 MCS levels• QPSK 1/2, QPSK 3/4, 16QAM 1/2, 16QAM 3/4, 64QAM 2/3
Simulation Results – CE MSE (3/6)Simulation Results – CE MSE (3/6)▪ PB 3 km/hr
– In FDM sounding category, MTK and Motorola perform highly similarly– FDM performs better than CDM, especially when number of users increases
3 users 6 users
0 5 10 15
-22
-20
-18
-16
-14
-12
-10
-8
SNR (dB)
Ave
rage
CE
Mea
n S
quar
e E
rror
CDM ExampleMotorola FDMMTK FDM
0 5 10 15-22
-20
-18
-16
-14
-12
-10
-8
SNR (dB)
Ave
rage
CE
Mea
n S
quar
e E
rror
CDM ExampleMotorola FDMMTK FDM
Simulation Results – CE MSE (4/6)Simulation Results – CE MSE (4/6)▪ VA 30 km/hr
– Performance tendency is the same as under PB 3 channel model
3 users 6 users
0 5 10 15
-18
-16
-14
-12
-10
-8
SNR (dB)
Ave
rage
CE
Mea
n S
quar
e E
rror
CDM ExampleMotorola FDMMTK FDM
0 5 10 15-18
-16
-14
-12
-10
-8
SNR (dB)
Ave
rage
CE
Mea
n S
quar
e E
rror
CDM ExampleMotorola FDMMTK FDM
Simulation Results – Throughput (5/6)Simulation Results – Throughput (5/6)▪ PB 3 km/hr
– 8 BS antennas and 3 single-antenna MSs (8x3 MIMO)• BS performs ZF beamforming two subframes (12 symbol durations) later than so
unding – Two companies’ proposals have highly similar performance
10 15 20 25 300
0.1
0.2
0.3
0.4
0.5
SNR (dB)
loss
ove
r bes
t (10
0%)
MotorolaMTK
10 15 20 25 300
2
4
6
8
10
12
SNR (dB)
Thro
ughp
ut (b
its p
er s
ubca
rrier
)
MTKMotorola
3 users
Simulation Results – Throughput (6/6)Simulation Results – Throughput (6/6)▪ VA 30 km/hr
– MTK’s proposal perform very slightly better than Motorola’s one
3 users
10 15 20 25 300
0.2
0.4
0.6
0.8
1
SNR (dB)
loss
ove
r bes
t (10
0%) Motorola
MTK
10 15 20 25 300
2
4
6
8
10
12
SNR (dB)
Thro
ughp
ut (b
its p
er s
ubca
rrier
)
MTKMotorola
Summary (1/1)Summary (1/1)▪ For FDM sounding, MTK’s and Motorola’s sounding designs have similar p
erformances– MTK’s sounding can have very slightly better performance at mobility case– Motorola’s design seems to restrict MS’s behavior
• Cannot apply STBC when sounding is enabled
▪ Simulations also show that FDM sounding can largely outperform CDM sounding, especially when number of users increases– Since code orthogonality is destroyed by channel frequency/time selectivity,
multi-user interference is severe
Text ProposalText Proposal11.9.2.3.4 … Sounding from single or multiple antennas and multiple users are supported to provide MIM
O channel information for DL transmission. The allocation of sounding signals should not collide with the pilots for data transmission, so as to maintain data recovery quality. Sounding signals also should be allocated such that the sounding pattern in each DRU is kept the same. Moreover, the UL behaviors of other non-sounding MSs (e.g., using SFBC) should not be affected when sounding channel is enabled. Power allocation, sounding sequence design and mapping to subcarriers is TBD.
AppendixAppendix▪ Channel estimation for CDM sounding
Freq
.
Time
Freq
.
Time
1H
1H
1H
1H1H
1H
is not channel estimate of these tones, and so channel mismatches occur
1H
2D-MMSE channel estimator thus performs poorly
▪ CDM data model of red dash square
–
–
– is Hadamard product
▪ Channel estimation of user 1
8
1i i
i r H c n
8 8 821 1 1 1 1 1 1 1
1 1 1, 1ˆ H H H H H
i i x x i ii x i i
H H c
c r c H c c n c H c c n
1Hi i c c
1 2 3 4 5 6 7 8T
i i i i i i i i iH H H H H H H H H
Cause channel estimation errorAverage channel estimate, and so causechannel mismatch