Literature Review summary (Combining “adaptive modulation” and “adaptive
beamforming”)
Title
Author(s)
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Multiantenna Adaptive Modulation with Beamforming Based on
Bandwidth-Constrained Feedback
Pengfei Xia, Shengli Zhou, Georgios B. Giannakis
IEEE Transaction on Communications
Vol. 53, No.3, March 2005, page 526
Adapting to time-varying channel conditions and fading to increase
rate, with rate-limited feedback
Investigate adaptive modulation system based on transmit
beamforming with rate-limited feedback. Jointly design the feedback
strategy and transmission parameters for rate-limited feedback
Contributions
Proposed a nested iterative approach that yield a practical design of the
adaptive transmission and feedback strategy
System /
technology
used
Transmit beamforming and adaptive modulation (transmit power,
signal constellation, beamforming direction and feedback strategy),
Multiple transmit, one receive antenna, wireless channel is frequency
nonselective,
Mathematical
techniques
used
/methodology
Formulate the problem, link with existing works> difficulty in solving
original problem analytically, suboptimal formulation> develop the
nested approach> present the numerical results
Adaptive
Modulation
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Jointly design transmit power, the signal constellation,
beamforming direction and feedback strategy
Subject to average BER, and average transmit-power
constraint
B feedback bits per block, decides a feedback index n  {1, 2,
…, N}, N= 2B
Corresponding to each index n, transmitter will select the
transmission mode Mn = (Mn, Pn, Wn)
Mn= signal constellation size
Pn= transmit power
Wn=beamsteering vector
For signal constellation, consider 2 case : continuous rate &
discrete rate
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Assumptions
Key Results
Conclusions
Continuous-rate: Mn= 2 bn , where bn  0 is arbitrary real
number
Discrete-rate: Mn= 22, 24, 26, …;, bn are even integers,
corresponding to square M-QAM constellation
Mn=0 : no data transmission
Goal: maximize transmission rate, subject to certain
performance and power constraints
Nested iterative approach developed to yield suboptimal yet
practical design for continuous rate case
Discrete rate designed based on continuous rate
Channel do not vary within block, independent identically distributed
channel coefficients, Perfect CSI at receiver, Feedback channel is error
free, delay free
Throughput enhancement (considerable improvement in transmission
rate, as the number of feedback bits increases)
A finite number of feedback bits can improve the overall performance
considerably
Critique
Title
Author(s)
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
Adaptive Modulation for Multiantenna Transmissions with
Channel Mean Feedback
Shengli Zhou, Georgios B. Giannakis
IEEE Transaction on Wireless Communications
Vol. 3, No.5, September 2004, page 1626
Adapting to time-varying channel conditions and fading to increase
rate, CSI imperfections (estimation errors & feedback delays)
 To design adaptive modulation scheme for multiantenna
transmissions with channel mean feedback.
 Investigate adaptive trellis-coded multiantenna modulation
Proposed a transmitter based on two dimensional beamformer that
System /
technology
used
Mathematical
techniques
used
/methodology
Adaptive
modulation
optimally adapts the basis beams, the power allocation between the
two beams, and signal constellation to maximize the transmission
rate, while maintaining the target BER
2-D beamformer (Alamouti data streams are power loaded and
transmitted along two orthogonal basis beams). Nt transmit and Nr
receive antennas, flat-fading channel, slowly time-varying channel
Partial CSI: Mean feedback( Models the spatial fading channels as
Gaussian random variables with nonzero mean and white covariance )
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Assumptions
Key Results
Conclusions
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Based on partial CSI (Mean feedback)
Two dimensional beamformer
Transmitter optimally adapts the basis beams, the power
allocation between to beams, and signal constellation, to
maximizes the transmission rate, while maintaining the
target BER
rate improvement
adaptive multiantenna modulation turns out to be less sensitive
to channel imperfections, compared to single antenna
counterpart
The result shows rate improvement, illustrate an interesting
tradeoff emerges between feedback quality and hardware
complexity
Relaxing the receiver complexity constraint, adaptive
modulation based on spatial multiplexing schemes is an
interesting future research topic
Critique
Title
Author(s)
Dynamic Spatial Subchannel Allocation with Adaptive
Beamforming for MIMO/OFDM Systems
Ya-Han Pan, Khaled ben Letaief, Zhigang Cao
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
System /
technology
used
Mathematical
techniques
used
/methodology
Assumptions
Key Results
Conclusions
IEEE Transactions on Wireless Communications
Vol.3, No.6, November 2004
Challenge to provide high data rates with high QoS over hostile mobile
environments with limited spectrum and ISI.
Propose a new technique
1. Propose a dynamic spatial subchannel allocation with
adaptive beamforming for broadband OFDM wireless
transmission system
2. Considered the performance of the proposed system combine
with adaptive modulation
Broadband OFDM
Adaptively select the eigenvectors associated with the relatively large
spatial subchannel eigenvalues to generate the beamforming weights at
the mobile and basestations and then dynamically assigns the
corresponding best spatial subchannels to transmit the OFDM block
symbols.
1. proposed system can achieve better performance than an
adaptive antenna-arrays-based OFDM system without dynamic
spatial subchannel allocation over multipath fading channels
2. proposed system is far less susceptible to feedback delay in
rapid time-varying channels and a little more sensitive to
channel estimation errors than conventional adaptive antennaarrays-based OFDM systems.
The proposed system could be prove to be an effective scheme for
providing significant increases in system’s capacity and bandwidth
efficicency as well as improvement in QoS
Critique
Title
How Accurate Channel Prediction Needs to be for TransmitBeamforming with Adaptive Modulation over Rayleigh MIMO
Channels?
Author(s)
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
System /
technology
used
Mathematical
techniques
used
/methodology
Assumptions
Key Results
Conclusions
Shengli Zhou, Georgios B. Giannakis
IEEE Transactions on Wireless Communications
Vol.3, No.4, July 2004, page 1285-1294
Channel prediction problems for adaptive modulation
Analyze the impact of channel predictor error on the BER
performance of a transmit beamformer with adaptive modulation
that treats the predicted channel is perfect.
Reveal the critical value of the normalized prediction error, below
which the predicted channels can be treated as perfect by the
adaptive modulator, otherwise, explicit consideration of the channel
imperfection must be accounted for at the transmitter
MIMO, Rayleigh fading, multiple transmit, multiple receive, transmitbeamformer, MMSE channel predictor based on Pilot Symbol Assisted
Modulation, Independent & identically distributed (iid) Rayleigh fading
MIMO channels.
1. Present the MMSE predictor
2. analyze the impact of channel prediction error
3. obtained a closed-form BER expressions for arbitrary number
of receive and transmit antennas
4. derive simple closed-form expressions when transmit and/or
receive antennas are less or equal to 2
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BER performance of the adaptive transmit-beamforming based
system depends on various system parameters only through a
single variable, the normalized channel prediction error.
When the error is below a certain critical value, the predicted
channels can be treated as perfect by the adaptive modulator
Critique
Title
Author(s)
Combination of Adaptive Beamforming & Adaptive Loading for
OFDM Packet Transmission
Ming Lei, Hiroshi Harada, Hiromitsu Wakana, Ping Zhang
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
System /
technology
used
Mathematical
techniques
used
/methodology
Assumptions
Key Results
Conclusions
IEEE Conference
2004, page 1215-1219
Propose a new scheme
Propose a combinational scheme of adaptive beamforming and
adaptive loading for OFDM
Least Mean Square algorithm, pre-FFT algorithm,
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Use frequency-domain adaptive loading to load the bits and
transmit power to the individual subcarriers to counter with
frequency selective fading.
Investigate 2 adaptive beamforming schemes based on LMS
algorithm used to estimate the array weight, difference in either
using time or frequency domain pilot vector. Both are based on
pre-FFT combining (lower complexity than post-FFT).
Beamforming scheme based on frequency domain pilot has marginal
performance gain while the one based on time-domain pilot has
comparatively low complexity.
The combinational scheme based on the adaptive beamforming &
adaptive loading is very effective in improving the performance of
OFDM packet transmission (decreasing PER)
Critique
Title
Author(s)
Effect of modifying Signal parameters on the Beamforming
Performance in CDMA Mobile Communications
B. Banitalebi, M. Karimi, M. Kamarei, G. Dadashsadeh (Iranian)
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
System /
technology
used
Mathematical
techniques
used
/methodology
Assumptions
Key Results
Conclusions
Critique
Title
2005 Asia-Pacific Conference on Communications, Perth, Western
Australia
3-5 October 2005, page 148-152
Effect of variation of PN codes length, modulation types and order
change the beamformer performance
Analyze the effects of variation of the signal properties on the
performance of the beamformer for two simple and mostly used
modulation techniques
Beamforming in BS, uplink mode, using Least Squares-Constant
Modulus Algorithm (LS-CMA), Gaussian Wide Sense Stationary
Uncorrelated Scattering
Investigation done theoretically and using simulations
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When the number of users is constant, increasing the code
length can efficiently improve the performance of the
beamformer
 Increasing the modulation order to achieve higher data
transmission rates causes some degradation in the output SER
bit it is not very serious
 Signal interference ratio has no significant effect on the
beamformer performance
 Using QAM modulation which uses both phase and amplitude
to separate different symbols from each other gives smaller
values of SER than PSK modulation
The parameters have different effects on the beamformer performance
On the Networking Performance of UTRA-like TDD and FDD
CDMA Systems Using Adaptive Modulation and Adaptive
Beamforming
Author(s)
Publication
(place & year
if book)
Volume no,
Month & Year,
pages
Problem being
addressed
Purpose
Contributions
System /
technology
used
Mathematical
techniques
used
/methodology
Assumptions
Key Results
Conclusions
Critique
Song Ni, Jonathan S. Blogh, Lajos Hanzo
IEEE Conference
2003, page 606-610
MS-MS interference (intra and intercell), BS-BS interference
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Characterize the capacity of an adaptive modulation assisted,
beam steering aided TDD/CDMA system.
 Studies the achievable network performance by simulation and
compares it to that of FDD/UTRA system
Non-shadowed, log-normal shadowed, Sample Matrix Inversion (SMI)
Performance metrics used are call dropping probability, Grade of
Service,
The base station is equipped with the Minimum Mean Squared Error
Block Decision Feedback Equaliser based MUD
The employment of adaptive arrays in conjunction with AQAM limited
the detrimental effects of co-channel interference and resulted in
performance improvements both in terms of achievable call quality and
the system’s capacity