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Adaptive MIMO Systems with Channel State Information at Transmitter
KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 This dissertation presents adaptation techniques that can achieve high spectral efficiency for single user multiple-input multiple-output (MIMO) systems. Two types of adaptation techniques, adaptive modulation and adaptive powe allocation, are employed to adapt the rate and the transmit power to fading channels. We start by investigating the adaptive modulation subject to a certain bit-error-ratio (BER) constraint, either instantaneous BER constraint or average BER constraint. The resulting average spectral efficiencies are obtained in closed-form expressions. It turns out that, by employing the average BER constraint, we can achieve the optimal average spectra efficiency at the cost of prohibitive computational complexity. On the other hand, instantaneous BER constraint leads to inferior performance with little computational complexity. In order to achieve comparable performance to the average BER constraint with limited complexity, a non-linear optimization method is proposed. To further enhance the average spectra efficiency, adaptive power allocation schemes are considered to adjust the transmit power across the temporal domain or the spatial domain, depending on the specific situation. Provided the closed-form expressions of the average spectral efficiency, the optimal MIMO coding scheme that offers the highest average spectral efficiency under the same circumstances can be identified. As we take into account the effect of imperfect channel estimation, the adaptation techniques are revised to tolerate interference introduced by the channel estimation errors. As a result, the degradation with respect to the average spectral efficiency is in proportion to signal-to-noise ratio (SNR). In order to facilitate fast development and verification of the adaptation schemes proposed for various MIMO systems, a reconfigurable Link Layer Simulator (LiLaS) which accommodates a variety of wireless/wireline applications is designed in the environment of MATLAB/OCTAVE. The idea of the simulator is originated from Software Defined Radio (SDR) and evolved to suit Cognitive Radio (CR) applications. For the convenience of modification and reconfiguration, LiLaS is functionally divided into generic blocks and all blocks are parameterized.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xvii, 79 p.
Series
Trita-ICT-COS, ISSN 1653-6347 ; 0804
Keyword [en]
adaptive modulation, adaptive power allocation, average spectral efficiency, MIMO, BER.
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-9777ISBN: 978-91-7415-188-6 (print)OAI: oai:DiVA.org:kth-9777DiVA: diva2:128182
Public defence
2009-01-30, Sal E, Forum IT, Kista, 14:00 (English)
Opponent
Supervisors
Note
QC 20100812Available from: 2009-01-07 Created: 2008-12-13 Last updated: 2010-08-12Bibliographically approved
List of papers
1. Discrete rate spectral efficiency improvement by scheme switching for MIMO systems
Open this publication in new window or tab >>Discrete rate spectral efficiency improvement by scheme switching for MIMO systems
2008 (English)In: IEEE International Conference on Communications, ISSN 1550-3607, E-ISSN 1938-1883, 3998-4002 p.Article in journal (Refereed) Published
Abstract [en]

Adaptive modulation scheme has been widely used in multiple-input multiple-output (MIMO) systems to enhance spectral efficiency while maintaining the bit error rate (BER) under a target level. We consider two MIMO schemes, orthogonal space-time block codes (OSTBC) and spatial multiplexing with zero-forcing receiver (SM-ZF), that apply adaptive modulation scheme and derive closed-form expressions of the average spectral efficiency and BER. Based on the closed-form expression of spectral efficiency, a low complexity switching method is utilized to obtain high spectral efficiency gain over an adaptive system using a single scheme.

Keyword
OSTBC; ZF; adaptive modulation; CSIT
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-9794 (URN)10.1109/ICC.2008.751 (DOI)000259505002241 ()2-s2.0-51249106622 (Scopus ID)
Note
QC 20100812Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
2. Impact of channel estimation error on performance of adaptive MIMO systems
Open this publication in new window or tab >>Impact of channel estimation error on performance of adaptive MIMO systems
2008 (English)In: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing, ISSN 1520-6149, 2865-2868 p.Article in journal (Refereed) Published
Abstract [en]

Adaptive modulation scheme has been widely used in multiple-input multiple-output (MIMO) systems to enhance the spectral efficiency while maintaining the bit-error-rate (BER) under a target level. In this work, we investigate the performance of adaptive modulation in the presence of imperfect channel estimation and the impact of estimation noise on the spectral efficiency. The closed-form expressions for the average spectral efficiency are derived. Two MIMO schemes are considered, i.e., orthogonal space-time block codes (OSTBC) and spatial multiplexing with zero-forcing receiver (SM-ZF), and a low complexity method to enable the transmitter to switch between OSTBC and SM-ZF is utilized to achieve higher spectral efficiency than adaptive OSTBC and adaptive SM-ZF.

Keyword
MIMO systems; communication system operations and management; communication system performance
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-9796 (URN)10.1109/ICASSP.2008.4518247 (DOI)000257456702039 ()2-s2.0-51449096603 (Scopus ID)
Note
QC 20100812Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
3. Asymptotic Performance of MMSE MIMO Systems Using Adaptive Modulation
Open this publication in new window or tab >>Asymptotic Performance of MMSE MIMO Systems Using Adaptive Modulation
(English)In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558Article in journal (Other academic) Submitted
Abstract [en]

This letter investigates the asymptotic performance of minimum-mean-square error (MMSE) in MIMO systemsusing adaptive modulation. The asymptotic average spectral efficiency and bit-error rate (BER) are derived basedon three approximations of the probability density function (p.d.f.) of effective SNR. Simulations suggest that themost accurate estimation of average spectral efficiency is obtained by using Gamma distribution.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-9797 (URN)
Note
QS 20120327Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
4. On Performance of Adaptive Modulation in MIMO Systems Using Orthogonal Space-Time Block Codes
Open this publication in new window or tab >>On Performance of Adaptive Modulation in MIMO Systems Using Orthogonal Space-Time Block Codes
2009 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 58, no 8, 4238-4247 p.Article in journal (Refereed) Published
Abstract [en]

We provide a systematic study of adaptive modulation schemes in multiple-input multiple-output (MIMO)orthogonal space-time block codes (OSTBC) systems. Closed-form expressions are obtained to evaluate systemperformance, e.g., average spectral efficiency, bit-error-ratio (BER), and outage probability. Provided the closedformexpressions, the optimal SNR thresholds that yield the maximal average spectral efficiency can be solved. Inorder to reduce complexity of the optimal algorithm, an original method which can achieve approximately the sameperformance as the optimal one is proposed. Furthermore, we apply these methods in a more practical situation,where channel estimation is imperfect, and examine how the performance is affected due to channel estimationerrors.

Keyword
Adaptive modulation; bit error ratio (BER) constraint; imperfect channel state information (CSI); multiple input-multiple output (MIMO); orthogonal space-time block code (OSTBC)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-9798 (URN)10.1109/TVT.2009.2022475 (DOI)000270547800035 ()2-s2.0-70350214277 (Scopus ID)
Note
QC 20100812. Uppdaterad från submitted till published (20100812).Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
5. Adaptive Modulation and Power Allocation for OSTBC
Open this publication in new window or tab >>Adaptive Modulation and Power Allocation for OSTBC
2009 (English)In: ICICS 2009 - Conference Proceedings of the 7th International Conference on Information, Communications and Signal Processing: Macau Fisherman's Wharf: 8 December 2009 through 10 December 2009, 2009Conference paper, Published paper (Refereed)
Abstract [en]

Adaptive modulation and power allocation schemes have been widely used in multiple-input multiple-output(MIMO) systems to enhance spectral efficiency while maintaining bit error ratio (BER) to a target level. We derivethe spectral efficiency of orthogonal space-time block codes (OSTBC) that can be achieved by applying adaptivemodulation and power allocation. Compared to non-adaptive power scheme, the adaptive power allocation canachieve substantial gain in the spectral efficiency. Moreover, channel estimation errors are taken into account andthe impact on the spectral efficiency is investigated.

Keyword
Adaptive modulation; Adaptive power allocation; MIMO; OSTBC
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-9799 (URN)10.1109/ICICS.2009.5397730 (DOI)2-s2.0-77949627444 (Scopus ID)
Note
QC 20100812. Uppdaterad från submitted till konferensbidrag (20100812).Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2010-08-12Bibliographically approved

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