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Phase Noise Effects on OFDM
Systems: Consequences and Solutions
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| Faculty: Y.
Bar-Ness |
| Students: Songping
Wu |
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| Orthogonal
frequency division multiplexing (OFDM) has been widely
adopted and implemented in wire and wireless communications.
In comparison to single carrier transmission, OFDM is
quite effective to eliminate inter-symbol interference
(ISI) caused by channel multipath fading hostility while
providing high transmission data rate with high spectral
efficiency. Moreover, OFDM receiver becomes relatively
simple with one-tap channel equalizer and simple hardware.
Hence, it is very well suited to the future high data
rate wireless multimedia communications.
The disadvantage of OFDM, however, is
its sensitivity to both frequency offset and phase noise.
Caused by the frequency difference between the transmitter
and the receiver, or by Doppler shift, frequency offset
has been thoroughly analyzed and many methods have been
proposed for its estimation and correction. Unlike frequency
offset which is deterministic, phase noise is a random
process caused by the fluctuation of the receiver and
transmitter oscillators. Phase noise causes leakage
of DFT which subsequently destroys the orthogonalities
among subcarrier signals, leading to the significant
performance degradation.
Our research work on phase noise includes:
- We present the OFDM performance analysis
in the presence of phase noise in both single-user
and multiple access environments.
- For single-user case, we provide exact
closed-form expression of signal to interference plus
noise ratio (SINR) and the corresponding lower and
upper bounds of SINR for small phase noise.
- For multi-user case, we derive a closed-form
BER expression with BPSK modulation.
- With the understandings of phase noise
effects, we also propose several methods
to mitigate both single and multiple phase noise.
- Phase noise suppression
algorithm
- Simultaneous CPE and ICI correction
- Multiple phase noise correction
for OFDM/SDMA
- The effect of phase noise on OFDM
channel estimation. We propose joint channel and frequency
offset estimation in the presence of phase noise
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| Figure:
Phase noise suppression algorithm |
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| References: |
| [1] Songping Wu
and Yeheskel Bar-Ness, "A phase noise suppression
algorithm for OFDM-based WLANs," IEEE Comm. Lett.,
vol. 6, pp. 535-537, Dec. 2002. |
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| [2] Songping Wu and Yeheskel
Bar-Ness, "OFDM systems in the presence of phase
noise: consequences and solutions," Accepted by IEEE
Trans. Comm. in Sept. 2003. |
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| [3] Songping Wu
and Yeheskel Bar-Ness, "Multiple phase noise correction
for OFDM/SDMA," to appear in Globecom'03, San Francisco,
CA, USA, Dec. 2003. |
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| [4] Songping Wu
and Yeheskel Bar-Ness, "A new phase noise mitigation
method in OFDM systems with simultaneous CPE and ICI correction,"
Proc. Of multi-carrier spread-spectrum for future wireless
systems 2003, Germany, Sep. 2003. |
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| [5]Songping Wu
and Yeheskel Bar-Ness, "MC-CDMA performance with
multiple phase noise over an uplink correlated Rayleigh
fading channel," IST mobile and wireless communications
summit 2003, Aveiro, Portugal, June 2003. |
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| [6] Songping Wu
and Yeheskel Bar-Ness, "OFDM channel estimation in
the presence of frequency offset and phase noise,"
ICC'03, Anchorage, Alaska, USA, May 2003. |
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Phase Noise Mitigation in MIMO OFDM
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| Faculty: Y.
Bar-Ness |
| Students: Pan
Liu, Songping Wu |
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Orthogonal
frequency division multiplexing (OFDM) is a promising
technique that transmits multiple data symbols simultaneously
over orthogonal subcarriers through a single communication
channel. It has been adopted by IEEE 802.11a standard
as the transmission technique for WLANs.
The combined MIMO-OFDM scheme has an advantage over conventional
SISO systems for its much improved system capacity or
BER performance introduced by MIMO technique, and its
robustness to channel frequency selectivity due to OFDM
technique. However, similar to SISO-OFDM, MIMO-OFDM is
also very sensitive to phase noise. Various phase noise
correction methods were proposed for single -antenna systems
with perfect channel estimation, but nothing has been
suggested for the correlated multi-antenna case. In this
project, we proposed a new phase noise mitigation method
for the general Mt by Mr spatially correlated MIMO WLANs
with channel estimation error.
Moreover, close forms of BER performance
has also been derived both for AWGN and fading channel
with BPSK or QPSK modulation. Simulation results show
that the proposed analytical forms are quite accurate
for different phase noise levels and block lengths.
In particular, we analytically proves that a constant
phase noise tracking mechanism is needed even with a
high quality oscillator, which is the essential motivation
for phase noise mitigation studies.
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| Figure:
Phase noise suppression algorithm |
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| References: |
| [1] P. Liu S. Wu and
Y. Bar-Ness, “A Phase Noise Mitigation Scheme for MIMO
WLANs with Spatially Correlated and Imperfectly Estimated
Channels,” accepted for publication in IEEE Commun. Lett. |
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| [2] S. Wu, P. Liu and Y. Bar-Ness
"Phase Noise Mitigation for OFDM systems," accepted for
publication in IEEE Trans. Wireless Commun. |
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| [3] P. liu and Y. Bar-Ness,
"BER performance analysis for OFDM Systems With Phase
Noise," accepted for publication in ICC' 06. |
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| [4] P. liu and Y. Bar-Ness,
"Phase noise mitigation for V-BLAST OFDM system," Micorwave
Antenna Propagation and EMC Technologies For Wireless
Communications, Beijing, China, Aug. 2005. |
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| [5] P. liu and Y. Bar-Ness,
"Phase Noise Mitigation Method with MMSE based CPE Estimator
in MIMO OFDM," Wireless and Optical Communications Conference,
Newark, Apr. 2005. |
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Peak to Average Power Ratio Reducation
in MIMO OFDM
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| Faculty: Y.
Bar-Ness |
| Students: Mizhou
Tan, Zoran Latinovic, Pan Liu |
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| Many peak-to-average
power ratio (PAPR) reduction schemes have been proposed
for orthogonal frequency division multiplexing (OFDM)
systems. Among them, signal scrambling methods are attractive
since OFDM signals are modified without distortion to
present better PAPR property and require relatively low
complexity. In MIMO-OFDM systems, a straightforward way
for PAPR reduction is to apply existing schemes proposed
for OFDM systems separately on each transmit antenna.
A MIMO-OFDM system with two transmit antennas and orthogonal
space-time block coding (STBC) is considered here with
a novel idea for cross-antenna rotation and inversion
(CARI). While requiring only a small amount of side
information, this scheme fully utilizes additional degrees
of freedom provided by employing multiple transmit antennas.
As in our previous work [2], two suboptimal schemes
presented, termed successive suboptimal CARI (SS-CARI)
and random suboptimal (RS-CARI) are also investigated.
These schemes provide a good compromise between performance
and complexity. Compared with the concurrent SLM scheme
proposed in [1], the new schemes present significant
performance advantage, particularly with small number
of subblocks.
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| Figure:
Phase noise suppression algorithm |
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| References: |
[1] M. Tan Z. Latinovic
and Y. Bar-Ness, “STBC MIMO-OFDM Peak Power Reduction
by
Cross-Antenna Rotation and Inversion,” IEEE Commun.
Lett. vol. 9, pp. 592-594, Jul. 2005. |
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| [2] Yung-Lyul Lee, Young-Hwan
You, Won-Gi Jeon, Jong-Ho Paik and Hyoung-Kyu Song, “Peak-to-average
power ratio in MIMO-OFDM systems using selective mapping,”
IEEE Commun. Lett., vol. 7, pp. 575–577, Dec. 2003. |
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| [3] M. Tan and Y. Bar-Ness,
“OFDM Peak-to-Average Power Ratio Reduction by Combined
Symbol Rotation and Inversion with Limited Complexity,”
in Proc. IEEE GLOBECOM, San Francisco, CA, 2003, pp. 605–610. |
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| Adaptive
modulation, coding, and power allocation for MIMO-OFDM |
| Faculty: Y.
Bar-Ness |
| Students: Jordi
Diaz |
| Industry partners:
Samsung Electronics |
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MIMO-OFDM is
a very promising technology to communicate through wireless
frequency selective channels since it can combat channel
dispersion by means of diversity while exploits multiplexing
gains. When Channel State Information (CSI) is available
at the transmitter, MIMO-OFDM transceivers can be designed
so that the ultimate rates of communication can be attained
with lower complexity than channel unaware schemes, by
means of Adaptive Modulation and Coding (AMC).
For practical operation, we have proposed a new approach
for the design of (AMC) for MIMO-OFDM wireless communications
under practical implementation constraints such as delay,
and low number of encoders. The design criteria are based
on the possible conflict in the joint extraction of diversity
and adaptation benefits of a MIMO-OFDM channel known at
the transmitter. The proposed scheme avoids this conflict
by adapting as accurately as possible given the side information
while using diversity to combat remaining uncertainty.
This is accomplished by channel parallelization, sorting
and grouping into modulation modes. Moreover, a new power
allocation strategy, named WF/CI, is also introduced and
showed to perform better, in a practical setting, than
the theoretically optimal water-filling power allocation.
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| References |
| [1] J. Diaz ,Y.
Bar-Ness, and Y. H. Lee, "A new approach to joint
AMC and power allocation for MIMO-OFDM" to appear
in Proc. of Advanced International Conference in Telecommunications,
AICT. Guadeloupe, French Caribbean, February 2006. |
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Copyright © 2000-2006 CWCSPR, NJIT.
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