Huawei Technologies Co., Ltd. All right reserved Slide 1
www.huawei.com
TELFOR-2013 November 26-28, 2013
Tensor-Based Multiuser Detection
and
Intra-Cell Interference Mitigation
in LTE PUCCH
Vladimir Lyashev | Ivan Oseledets | Delai Zheng
Huawei Technologies
Russian Research Center, Moscow ([email protected])
Huawei Technologies Co., Ltd. All right reserved Slide 2
Why does PUCCH important?
“PUCCH occupies too much bandwidth and
is used not in the most efficient way.” Field-test scenario:
• eRAN7, 10 MHz
• 60 connected UEs
• 30 UEs constantly downloading
large files (i.e. video streaming)
eNodB allocates
• 10RB for PUCCH,
• 3 UE per RB in average
“VoLTE dramatically
increases PUCCH usage.” • 8 million VoLTE users worldwide
• VoLTE will take off in 2015-2016 worldwide
• over 10-20 MHz spectrum - hundreds users
• 46% MBB providers required VoLTE during 1 year
AMR calls/1MHz
GSM 8
UMTS 12
HSPA 24
VoLTE 50
“40% Of YouTube Traffic Now Mobile,
Up From 25% In 2012, 6% In 2011.”
Huawei Technologies Co., Ltd. All right reserved Slide 3
LTE Uplink: resources
Huawei Technologies Co., Ltd. All right reserved Slide 4
PUCCH Allocation and SRS Signal
SRS bandwidth is multiplied
by 4RB: 4, 8, 12, …
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Intra-cell Interference in LTE PUCCH
In practice, time-alignment of the
signals at the eNodeB receiver is
not perfect.
Up to:
• 36UE per 1RB in Format 1x
• 12UE per 1RB in Format 2x
Separation by CAZAC sequence
Huawei Technologies Co., Ltd. All right reserved Slide 6
Timing Error: Main Reasons
limited resolution and measurement errors
propagation time change due to UE movement
oscillator drift
abrupt change of the multipath channel
misdetection of the Timing Advance
(Initial or Update) command
Huawei Technologies Co., Ltd. All right reserved Slide 7
Abrupt changes in channel delay profile T
A
co
mm
an
d
Timing
correction at
UE
Timing
correction at
UE
Timing
correction at
UE
Path birth-
death
Path birth-
death
abs(timing
error)
200ms-1s 200ms-1s 200ms-1s
can’t be compensated by TA commands alone!
Huawei Technologies Co., Ltd. All right reserved Slide 8
Field-test measurements: scenario
1
2
1
2
20 km/h speed
600 m length difference
720kHz (6RB) SRS signal
generation
// blue line
14.4 MHz measurement signal
// red line
Huawei Technologies Co., Ltd. All right reserved Slide 9
Field test measurements: results
Huawei Technologies Co., Ltd. All right reserved Slide 10
Mathematical Model
IPPTPPTPYH
j
Q
jqq
qqqq
H
jjjjj
H
jj XHXH 2
ceinterferencellintra
1losspower
NUE = 6, TAerror = 0 μs NUE = 6, TAerror = 1.56 μs
Desired user Interference SIR Desired user Interference SIR
23.7 0.11 23 dB 14.41 4.12 5.5 dB
12.52 0.67 22 dB 11.23 2.63 6.5 dB
13.37 0.95 11 dB 16.91 1.01 12 dB
9.83 0.65 12 dB 2.42 3.15 -1.2 dB
7.5 0.26 15 dB 7.97 2.71 4.5 dB
10.6 0.51 13 dB 5.11 4.21 0.8 dB
Measurement results
Me
asu
rem
ent #
CAZAC property for ideal sync.: 𝐏𝑗𝐻𝐏𝑞 =
1, 𝑗 = 𝑞;0, 𝑗 ≠ 𝑞.
Huawei Technologies Co., Ltd. All right reserved Slide 11
Mathematical Model and Its Approximation
),,(),(),(),,,(),,(),,(1
klnEkqTlqXlknqHlkqPklnYQ
q
B-rank channel approximation:
B
kSnqWlknqH1
),(),,(),,,(
Rank-2 model basically gives a very good fit to the
experimental channel H(q, n, l, k), usually of a fit of order 95%.
The rank-1 model also look promising, and can approximate
70% of the energy.
Huawei Technologies Co., Ltd. All right reserved Slide 12
Rank-1 (B=1) Model Approximation
signal) (receivedtensor 3Dforslice
),,(),(
th
l
l
klnYknY
sequence) (referencetensor 3Dforslice
),,(),(
th
l
l
klqPkqP
Mathematical Notation in
Slice Form
)()()( kSkTkT
Jo
int
Alg
ori
thm
AL
S-1
llll ETPWXY
Huawei Technologies Co., Ltd. All right reserved Slide 13
Joint Detection
Receive Signal
Simple Channel
Estimation & MRC
with equalizing
Set as initial guess
for ALS iterations ALS-1 iterations
Output CQI bits
W0 X0 X
Y
XMRC
T0= I12x12^
QPSK-symbols
demapping &
decoding
H0
Update T ^ Update W Update X
Iteration++
lTll YTIPWX ˆ lWl YIXW ˆ lllX YPXIW ˆ
Huawei Technologies Co., Ltd. All right reserved Slide 14
Joint Detection with Quality Control
Qual
ity
dec
odin
g
TErr = 0
FER in MRC: 128 / 12 000
FER in ALS-1: 225 / 12 000
MRC & ALS-1 have the same error frames: 114 / 12 000
ALS-1 males mistake (MRC not): 111 / 12 000
TErr = 3
FER in MRC: 407 / 12 000
FER in ALS-1: 180 / 12 000
MRC & ALS-1 have the same error frames: 107 / 12 000
ALS-1 males mistake (MRC not): 73 / 12 000
Pilots
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Simulation Parameters
Parameter Value
LTE PUCCH format format 2
Bandwidth 1.4 MHz
CQI 7 bits
Modulation type QPSK
Number of Rx antennas 4
Number of Tx antennas per user 1
Number of users 6
Cyclic shift (CS) interval for RS π / 3
Power of desired user (CS=0) 0 dB
Power for UE with CS=1,3,5 3 dB
Power for UE with CS=2,4 0 dB
Timing error (uniform distribution) -1.56 … 1.56 us
Propagation channel ETU70
Number of simulated sub-frames 20 000
Huawei Technologies Co., Ltd. All right reserved Slide 16
Convergence
with Quality Decoding Control without Quality Decoding Control
Huawei Technologies Co., Ltd. All right reserved Slide 17
Simulation Results
with Quality Decoding Control without Quality Decoding Control
Gap: 0.8 dB Gap: 0.4 dB
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Outlook
Non-Orthogonal Access
MU-MIMO and Massive-MIMO
Algorithm Diversity for Cloud RAN (cRAN)
Dimension Reduction in Non-Linear Signal
Processing
Huawei Technologies Co., Ltd. All right reserved Slide 19
www.huawei.com
TELFOR-2013 November 26-28, 2013
Dr. Vladimir Lyashev, IEEE Member [ [email protected] ]
[ linkedin.com/in/lyashev/ ]