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  • 51. Dam, Hai Huyen
    et al.
    Nordholm, Sven
    Cantoni, Antonio
    Haan, Jan Mark de
    Iterative Method for the Design of DFT Filter Bank2004In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 51, no 11, p. 581-6Article in journal (Refereed)
    Abstract [en]

    Multi-rate adaptive filters have numerous advantages such as low computational load, fast convergence and parallelism in the adaptation. Drawbacks when using multi-rate processing are mainly related to aliasing and reconstruction effects. These effects can be minimized by introducing appropriate problem formulation and employing sophisticated optimization techniques. In this paper, we propose a formulation for the design of filter bank which controls the distortion level for each frequency component directly and minimizes the inband aliasing and the residual aliasing between different subbands. The advantage of this problem formulation is that the distortion level can be weighted for each frequency depending on the particular practical application. A new iterative algorithm is proposed to optimize simultaneously over both the analysis and the synthesis filter banks. This algorithm is shown to have a unique solution for each iteration. For a fixed distortion level, the proposed algorithm yields a significant reduction in both the inband aliasing and the residual aliasing levels compared to existing methods applied to the numerical examples.

  • 52. Dam, Hai Huyen
    et al.
    Nordholm, Sven
    Zepernick, Hans-Jürgen
    Frequency Domain Blind Equalization for MIMO Systems2005Conference paper (Refereed)
    Abstract [en]

    This paper presents a new normalized frequency domain approach for adaptive blind equalization for multiple-input multiple-output (MIMO) communication systems. We first develop a time domain block based algorithm that updates the equalizer coefficients once per block of data symbols. As the time domain algorithm involves infinite summations in the separation cost function, an approximation is then proposed to reduce the cost function to finite summations. As a consequence, the block based time domain algorithm can be implemented in the frequency domain to reduce the computational complexity associated with the conventional symbol-by-symbol time domain update. Furthermore, by recognizing that the signals in the frequency domain are orthogonal, it is possible to significantly improve the convergence rate by normalizing the update equations with respect to the signal power in each frequency bin. Simulation results show that the proposed algorithm can successfully equalize the received signals while maintaining low computational complexity. Moreover, the presented normalized frequency domain blind equalization algorithm for MIMO systems significantly improves the convergence rate.

  • 53. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordholm, Sven
    Nordberg, Jörgen
    Spreading Code Design Using a Global Optimization Method2005In: Annals of Operations Research, ISSN 0254-5330, E-ISSN 1572-9338, Vol. 133, no 1-4, p. 249-264Article in journal (Refereed)
    Abstract [en]

    The performance of a code division multiple access system depends on the correlation properties of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference and to improve bit error performance. An auto-correlation function with a distinct peak enables proper synchronization and suppresses intersymbol interference. However, these requirements contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize the out-of-phase average mean-square aperiodic auto-correlation with average mean-square aperiodic cross-correlation being allowed to lie within a fixed region. This approach is applied to design sets of complex spreading sequences. A design example is presented to illustrate the relation between various correlation characteristics. The correlations of the obtained sets are compared with correlations of other known sequences.

  • 54. Davis, Alan
    et al.
    Low, Siow Yong
    Nordholm, Sven
    Grbic, Nedelko
    A subband space constrained beamformer incorporating voice activity detection2005Conference paper (Refereed)
    Abstract [en]

    This paper introduces a new subband adaptive space constrained beamforming structure for use in hands-free speech enhancement applications. The scheme incorporates a space constrained source model and voice activity information through the integration of a voice activity detector (VAD). The VAD information is used to estimate noise covariance information during non-speech periods and to optimally estimate the source power spectral density (PSD), which is used to provide a spectrally optimized constraint on the source. The proposed structure is evaluated in a real car environment, yielding results which compare well to the optimal Wiener solution where full knowledge of the source is known. ©2005 IEEE.

  • 55. Duong, Quang Trung
    Exact Closed-Form Expression for Average Symbol Error Rate of MIMO-MRC Systems2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we derive closed-form expressions for exact average symbol error rate (SER) of multiple-input multiple-output (MIMO)-maximum ratio combining (MRC) systems with M-ary modulations. We obtain the tractable compact closed-form expressions for the average SER in terms of the Gauss and Appell hypergeometric functions which are provided as library functions in common mathematical softwares such as MAPLE and MATHEMATICA. The analysis is validated by comparing with Monte-Carlo simulations and we further show that our general SER expressions reduce to the previous known results for binary signals (M=2) as a special case. Applying the series representation of the Gauss and Appell hypergeometric function, we derive a very tight approximation for the average SER

  • 56. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Performance Analysis of Selection Decode-and-Forward Relay Networks2008In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 44, no 20, p. 1206-07Article in journal (Refereed)
    Abstract [en]

    The performance of decode-and-forward (DF) cooperative networks with relay selection is presented. Specifically, we derive closed-form expressions for symbol error probability (SEP), bit error rate (BER), and achievable spectral efficiency of DF relay selection system in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels taking into account the incapability of decoding the received signals' cyclic redundancy code (CRC) at the relays. We also perform Monte-Carlo simulations to validate the analysis.

  • 57. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Tran, Nguyen Nam
    Ergodic Capacity of Cooperative Networks Using Adaptive Transmission and Selection Combining2009Conference paper (Refereed)
    Abstract [en]

    Closed-form expressions for channel capacity of repetition-based cooperative networks under adaptive transmission with selection combining are presented under the assumption of independent Rayleigh fading. Specifically, three different adaptive techniques are investigated: optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and channel inversion with fixed rate (TIFR). Among them, for an arbitrary number of relays, TIFR gives the worst channel capacity; OPRA gives the best channel capacity and ORA has a channel capacity quality in between the others. The analysis results, based on the upper and lower bound of the end-to-end SNR, agree very well with the simulated results and definitely show the impact of selection combining on the calculated channel capacity per unit bandwidth

  • 58. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Zepernick, Hans-Jürgen
    On the Performance of Selection Decode-and-Forward Relay Networks over Nakagami-m Fading Channels2009In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 13, no 3, p. 172-174Article in journal (Refereed)
    Abstract [en]

    In this paper, we present the performance of fixed decode-and-forward cooperative networks with relay selection over independent but not identically distributed Nakagamim fading channels, with integer values of the fading severity parameter m. Specifically, closed-form expressions for the symbol error probability and the outage probability are derived using the statistical characteristic of the signal-to-noise ratio. We also perform Monte-Carlo simulations to verify the analytical results

  • 59. Duong, Quang Trung
    et al.
    Engelke, Ulrich
    Zepernick, Hans-Jürgen
    Unequal Error Protection for Wireless Multimedia Transmission in Decode-and-Forward Relay Networks2009Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose an unequal error protection (UEP) scheme for multimedia transmission over wireless decode-and-forward (DF) relay networks. We prove that relay selection combining (R-SC) mode yields a better error rate performance than all-participate relays, i.e., distributed spacetime codes (DSTC) and orthogonal transmission with maximum ratio combining (OT-MRC) at the destination. Hence, we apply the R-SC scheme for transmitting bit sequence with high priority while the cooperative spatial multiplexing scheme is employed for the bit-stream with low priority. With this strategy, we achieve the maximum spatial diversity gain for high priority data and a high spatial multiplexing gain for low priority data. Monte- Carlo simulations and analytical results are shown to validate the proposed UEP scheme.

  • 60. Duong, Quang Trung
    et al.
    Ha, Dac-Binh
    Tran, Hoai-An
    Vo, Nguyen-Son
    Symbol Error Probability of Distributed-Alamouti Scheme in Wireless Relay Networks2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyze the maximum likelihood decoding performance of non-regenerative cooperation employing Alamouti scheme. Specifically, we derive two closed-form expressions for average symbol error probability (SEP) when the relays are located near by the source or destination. The analytical results are obtained as a single integral with finite limits and an integrand composed solely of trigonometric functions. Assessing the asymptotic (high signal-to-noise ratio) behavior of SEP formulas, we show that the distributed-Alamouti codes achieves a full diversity order. We also perform Monte-Carlo simulations to validate the analysis.

  • 61. Duong, Quang Trung
    et al.
    Ha, Dac-Binh
    Tran, Hoai-An
    Vo, Nguyen-Son
    Haroon, Ahsan
    On The Symbol Error Probability of Distributed-Alamouti Scheme2009In: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 4, no 7, p. 437-444Article in journal (Refereed)
    Abstract [en]

    Taking into account the relay’s location, we analyze the maximum likelihood (ML) decoding performance ofdualhop relay network, in which two amplify-and-forward (AF) relays employ the Alamouti code in a distributed fashion. In particular, using the well-known moment generating function (MGF) approach we derive the closed-form expressions of the average symbol error probability (SEP) for M-ary phase-shift keying (M-PSK) when the relays are located nearby either the source or destination. The analytical result is obtained as a single integral with finite limits and the integrand composed solely of trigonometric functions. Assessing the asymptotic characteristic of SEP formulas in the high signal-to-noise ratio regime, we show that the distributed-Alamouti protocol achieves a full diversity order. We also perform the Monte-Carlo simulations to validate our analysis. In addition, based on the upper bound of SEP we propose an optimal power allocation between the first-hop (the source-to-relay link) and second-hop (the relay-to-destination link) transmission. We further show that as the two relays are located nearby the destination most of the total power should be allocated to the broadcasting phase (the first-hop transmission). When the two relays are placed close to the source, we propose an optimal transmission scheme which is a non-realtime processing, hence, can be applied for practical applications. It is shown that the optimal power allocation scheme outperforms the equal power scheme with a SEP performance improvement by 2-3 dB.

  • 62. Duong, Quang Trung
    et al.
    Nguyen, Ngoc-Tien
    Hoang, Trang
    Nguyen, Viet-Kinh
    Pairwise Error Probability of Distributed Space--Time Coding Employing Alamouti Scheme in Wireless Relays Networks2009In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 51, no 2, p. 231-244Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes, in which the source and the relay generate Alamouti space--time code in a distributed fashion. We restrict our attention to the space-time code construction for Protocol III in [1]. In particular, we derive two closed-form approximations for PEP when the relay is either close to the destination or source and an upper bound for any position of the relay. Using the alternative definition of $Q$-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.

  • 63. Duong, Quang Trung
    et al.
    Tran, Hoai-An
    Distributed Space-Time Block Codes with Amicable Orthogonal Designs2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we generalize the construction of distributed space–time block codes (DSTBCs) using amicable orthogonal designs which are originally applied to co-located multiple-antenna systems. We also derive the closed-form expression of average symbol error probability (SEP). The result is obtained in the form of single finite-range integral whose integrand contains only the trigonometric functions. Using the asymptotic (high signal-to-noise ratio) SEP formulas we show that the orthogonal DSTBCs achieve full diversity order. We also perform Monte-Carlo simulation to validate the analysis.

  • 64.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Yeoh, Phee Lep
    Vo, Nguyen Quoc Bao
    Elkashlan, Maged
    Yang, Nan
    Cognitive Relay Networks With Multiple Primary Transceivers Under Spectrum-Sharing2012In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, no 11, p. 741-744Article in journal (Refereed)
    Abstract [en]

    We examine the impact of multiple primary transmitters and receivers (PU-TxRx) on the outage performance of cognitive decode-and-forward relay networks. In such a joint relaying/spectrum-sharing arrangement, we address fundamental questions concerning three key power constraints: 1) maximum transmit power at the secondary transmitter (SU-Tx), 2) peak interference power at the primary receivers (PU-Rx), and 3) interference power at SU-Rx caused by the primary transmitter (PU-Tx). Our answers to these are given in new analytical expressions for the exact and asymptotic outage probability of the secondary relay network. Based on our asymptotic expressions, important design insights into the impact of primary transceivers on the performance of cognitive relay networks is reached. We have shown that zero diversity order is attained when the peak interference power at the PU-Rx is independent of the maximum transmit power at the SU-TX.

  • 65. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Adaptive Transmission Scheme for Wireless Cooperative Communications2009Conference paper (Refereed)
    Abstract [en]

    An adaptive transmission scheme for cooperative communications is proposed in this paper. Communication protocols with amplify-and-forward relays based on the distributed-Alamouti space-time code (achieving spatial diversity gain) and cooperative spatial multiplexing (C-SM) (pertaining spatial multiplexing gain) are considered. Specifically, under a fix transmission rate, we use adaptively the cooperative diversity (C-DIV) and C-SM according to channel conditions. With this strategy, either C-DIV with higher order modulation or C-SM with lower order modulation can be properly selected to enhance the error rate performance. The proposed adaptive protocol is shown to provide superior performance compared to C-DIV and C-SM.

  • 66. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Exact Average Symbol Error Rate of Cooperative Spatial Multiplexing in Composite Channels2008Conference paper (Refereed)
    Abstract [en]

    Performance of cooperative spatial multiplexing systems over composite channels is presented. In particular, we derive the exact closed-form average symbol error rate (SER) expressions for cooperative spatial multiplexing systems with linear equalization receiver (e.g., Zero-Forcing) and M-ary modulation scheme in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the average SER is expressed in the forms of Appell hypergeometric function. Applying the series representation of Appell hypergeometric function, we derive a very tight approximation for the average SER. We also perform Monte-Carlo simulations to validate our analysis.

  • 67. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Hybrid Decode-Amplify-Forward Cooperative Communications with Multiple Relays2009Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the performance gain of hybrid decode-amplify-forward (HDAF) relay protocol over the two conventional ones: the adaptive decode-forward (ADF) and amplify-forward (AF) in dual-hop multiple-relay networks. We analyze the performance gain in terms of the symbol error probability (SEP) in the high signal-to-noise ratio (SNR) regime. Similarly as in the single relay case [1], under a specific modulation scheme, these gains only depend on the ratio of channel mean power between the first-hop and second-hop transmission. In particular, we show that the HDAF protocol obtains a large gain, medium gain, and small gain over ADF, AF as the relays are placed close to the destination, half-way between the source and destination (symmetric case), and nearby the source, respectively. In contrast to the single-relay case in which the HDAF scheme has no benefit compared to ADF and AF as the relay is located close to the source [1], HDAF still achieves a small gain with multiple relays. Interestingly, we further show that for all cases the performance gains are saturated as the number of relays is large.

  • 68. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Ergodic Capacity of Cooperative Spatial Multiplexing Systems in Composite Channels2009Conference paper (Refereed)
    Abstract [en]

    The ergodic capacity of cooperative spatial multiplexing systems over composite channels is presented. Specifically, we derive the exact closed-form expressions for ergodic capacity of cooperative spatial multiplexing systems with linear receiver in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the final analytical result of ergodic capacity is described in a closed-form expression. We also perform Monte-Carlo simulations to validate our analysis. Subsequently, we apply the obtained analytical expression to evaluate some representative scenarios regarding to spatial multiplexing gain in relay composite channels

  • 69. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Performance Gain of Hybrid Decode-Amplify-Forward Cooperative Communications2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2009Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the performance of adaptive decode-forward (ADF), amplify-forward (AF), and hybrid decode-amplify-forward (HDAF) relaying protocol. In particular, we derive the closedform expression of symbol error probability (SEP) for these three relaying protocols. For the AF protocol, we derive a simpler and more tractable final result than previously published work [1]. Furthermore, analyzing the high signal-to-noise ratio (SNR) regime, we derive an asymptotically tight approximation for SEP. Especially, for the AF protocol, our SEP approximation is tighter than the result in [2]. The SEP approximation is used to assess an important aspect between the three different relaying protocols, i.e., the SEP performance gain of HADF over the two conventional relaying schemes ADF and AF. It is shown that the performance gain of HDAF over ADF and AF significantly depends on the relative value of channel conditions between source-to-relay and relay-to- estination link (relay channels). Interestingly, it is shown that the HDAF protocol has no benefit compare to the two others if the relay is located close to the source. In contrast, the performance gains of HDAF over the ADF and AF scheme are remarkably large as the relay moves nearby the destination. Specifically, the numerical results given as well as our analysis indicate that for QPSK modulation, HDAF outperforms ADF and AF with a performance improvement by 5 dB and 6 dB, respectively.

  • 70. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Performance of ROI-Based Image Transmission Using Cooperative Diversity2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we examine the spatial diversity of cooperative communications for image transmission without deploying multiple antennas at the transmitter. We propose a novel region of interest (ROI)-based scheme for image transmission over wireless cooperative/relay fading channels. By having the relay terminal assist the direct communications, we can increase the resilience for ROI against the error-prone fading channels. Our proposed scheme significantly improves the performance of ROI compared to the direct communications (no-cooperation) and conventional relay networks without performing any forward error correction. Although we focus on the adaptive decode-forward (ADF) relay protocol, our proposed scheme can be easily adopted to any other relaying protocol such as fixed decode-forward (FDF), amplify-forward (AF), hybrid decode-amplify-forward (HDAF), and distributed-Alamouti space--time coding. Simulation results show that under the the same total transmit power constraint our proposed scheme significant outperforms the conventional ones in terms of bit error rate (BER) and peak signal-to-noise ratio (PSNR).

  • 71. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Robust EZW Image Transmission Scheme Using Distributed-Alamouti Codes in Relay Networks2008Conference paper (Refereed)
    Abstract [en]

    A robust image transmission scheme deploying distributed-Alamouti space-time code (STC) over wireless relay networks is proposed. Specifically, we propose a cross-layer design combining application, networking, and physical layer to enhance the quality of multimedia data over error-prone wireless channels. At the application layer, a coded image sequence based on the wavelet transform is divided into two priorities. The higher priority contains the most significant information of image and the lower priority conveys less important information. At the physical layer, two pre-assigned relays cooperate to form a distributed-Alamouti code which help the source to transmit the low priority sequence of the image over error-prone wireless channels. At the networking layer, among the whole relay nodes in the networks we select two relay nodes which provides the maximum signal-to-noise ratio to convey the higher priority. With this strategy, we implicitly achieve unequal error protection for image transmission without controlling power or varying modulation and coding at the transmitter at the expense of increasing network's overhead (i.e. feedback information). The selection of relays needs limited feedback, hence, enabling our proposed scheme feasible in practical applications. Analytical and simulation results are provided to verify our proposal. It has been shown that the image quality is remarkably enhanced in terms of objective quality using the proposed scheme compared to the conventional transmission schemes.

  • 72. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Bao, Vo Nguyen Quoc
    Symbol error probability of hop-by-hop beamforming in Nakagami-m fading2009In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, no 20, p. 1042-1044Article in journal (Refereed)
    Abstract [en]

    The symbol error probability (SEP) of amplify-and-forward(AF) multiple-input multiple-output (MIMO) cooperative networks where beamforming is adopted at both the source and destination is investigated. In particular, the tight lower bound for SEP of AF MIMO relay systems is presented with hop-by-hop beamforming over independent, but not necessarily identically distributed, Nakagami-m fading channels. Furthermore, assessing the high SNR, an asymptotic SEP expression is derived which reveals the array and diversity gain. Numerical results are shown to verify the analysis in some representative scenarios.

  • 73.
    E., Okwelume Gozie
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Kingsley, Ezeude Anayo
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    BLIND SOURCE SEPARATION USING FREQUENCY DOMAIN INDEPENDENT COMPONENT ANALYSIS2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Our thesis work focuses on Frequency-domain Blind Source Separation (BSS) in which the received mixed signals are converted into the frequency domain and Independent Component Analysis (ICA) is applied to instantaneous mixtures at each frequency bin. Computational complexity is also reduced by using this method. We also investigate the famous problem associated with Frequency-Domain Blind Source Separation using ICA referred to as the Permutation and Scaling ambiguities, using methods proposed by some researchers. This is our main target in this project; to solve the permutation and scaling ambiguities in real time applications

  • 74.
    Elnourani, Mohamed
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    COGNITIVE RADIO AND GAME THEORY: OVERVIEW AND SIMULATION2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This thesis aims to clearly describe the cognitive radio and its components and operations. Moreover, it aims on describing the expected outcome from the most common techniques that are proposed for use in cognitive radios. In addition, it describes the basic principles of game theory and some simple game models that can be used to analyze the efficiency of the optimization algorithms. Furthermore, it investigates the use of load balancing algorithm and genetic algorithm in optimizing the decision making operation in cognitive radios. Matlab software simulations were carried out and the results show the promising benefit of using those two algorithms along with game theory in optimizing the dynamic spectrum allocation process.

  • 75. Engelke, Ulrich
    Perceptual Quality Metric Design for Wireless Image and Video Communication2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The evolution of advanced radio transmission technologies for third generation mobile radio systems has paved the way for the delivery of mobile multimedia services. In particular, wireless image and video applications are among the most popular services offered on modern mobile devices to support communication beyond the traditional voice services. The large amount of data necessary to represent the visual content and the scarce bandwidth of the wireless channel impose new challenges for the network operator to deliver high quality image and video services. Link layer metrics have conventionally been used to monitor the received signal quality but were found to not accurately reflect the visual quality as it is perceived by the end-user. These metrics thus need to be replaced by suitable metrics that measure the overall impairments induced during image or video communication and accurately relate them to subjectively perceived quality. In this thesis, we focus on objective metrics that are able to quantify the end-to-end visual quality in wireless image and video communication. Such metrics may then be utilised to support the efficient use of link adaptation and resource management techniques and thus guarantee a certain quality of service to the user. The thesis is divided into four parts. The first part contributes an extensive survey and classification of contemporary image and video quality metrics that may be applicable in a communication context. The second part then discusses the development of the Normalised Hybrid Image Quality Metric (NHIQM) that we propose for prediction of visual quality degradations induced during wireless communication. The metric is based on a set of structural features, which are deployed to quantify artifacts that may occur in a wireless communication system and also are well aligned to characteristics of the human visual system (HVS). In the third part, three metric designs are discussed that utilise the same structural feature set as a basis for quality prediction. Incorporation of further HVS characteristics into the metric design will then improve even more the visual quality prediction performance. The design and validation of all proposed metrics is supported by subjective quality experiments that we conducted in two independent laboratories. Comparison to other state of the art visual quality metrics reveals the ability of the proposed metrics to accurately predict visual quality in a wireless communication system. The last part contributes an application of NHIQM for filter design. In particular, the filtering performance of a de-blocking de-ringing post filter for H.263 video sequences is analysed with regards to visual quality of the filtered sequence when applying appropriate filter parameter combinations.

  • 76. Engelke, Ulrich
    et al.
    Kusuma, Tubagus Maulana
    Zepernick, Hans-Jürgen
    Perceptual Quality Assessment of Wireless Video Applications2006Conference paper (Refereed)
    Abstract [en]

    The rapid evolution of wireless networks is driven by the growth of wireless packet data applications such as interactive mobile multimedia applications, wireless streaming services, and video-on-demand. The largely heterogeneous network structures, severe channel impairments, and complex traffic patterns make the wireless networks much more unpredictable compared to their wired counterparts. One of the major challenges with the roll-out of these services is therefore the design of wireless networks that fulfill the stringent quality of service requirements of wireless video applications. In this paper, the applicability of perceptual image quality metrics for real-time quality assessment of Motion JPEG2000 (MJ2) video streams over wireless channels is investigated. In particular, a reduced-reference hybrid image quality metric (HIQM) is identified as suitable for an extension to video applications. It outperforms other known metrics in terms of required overhead and prediction performance.

  • 77. Engelke, Ulrich
    et al.
    Kusuma, Tubagus Maulana
    Zepernick, Hans-Jürgen
    Caldera, Manora
    Reduced-reference metric design for objective perceptual quality assessment in wireless imaging2009In: Signal Processing-Image Communication, ISSN 0923-5965 , Vol. 24, no 7, p. 525-547Article in journal (Refereed)
    Abstract [en]

    The rapid growth of third and development of future generation mobile systems has led to an increase in the demand for image and video services. However, the hostile nature of the wireless channel makes the deployment of such services much more challenging, as in the case of a wireline system. In this context, the importance of taking care of user satisfaction with service provisioning as a whole has been recognized. The related user-oriented quality concepts cover end-to-end quality of service and subjective factors such as experiences with the service. To monitor quality and adapt system resources, performance indicators that represent service integrity have to be selected and related to objective measures that correlate well with the quality as perceived by humans. Such objective perceptual quality metrics can then be utilized to optimize quality perception associated with applications in technical systems. In this paper, we focus on the design of reduced-reference objective perceptual image quality metrics for use in wireless imaging. Specifically, the Normalized Hybrid Image Quality Metric (NHIQM) and a perceptual relevance weighted L_p-norm are designed. The main idea behind both feature-based metrics relates to the fact that the human visual system (HVS) is trained to extract structural information from the viewing area. Accordingly, NHIQM and L_p-norm are designed to account for different structural artifacts that have been observed in our distortion model of a wireless link. The extent by which individual artifacts are present in a given image is obtained by measuring related image features. The overall quality measure is then computed as a weighting sum of the features with the respective perceptual relevance weight obtained from subjective experiments. The proposed metrics differ mainly in the pooling of the features and amount of reduced-reference produced. While NHIQM performs the pooling at the transmitter of the system to produce a single value as reduced-reference, the L_p-norm requires all involved feature values from the transmitted and received image to perform the pooling on the feature differences at the receiver. In addition, non-linear mapping functions are developed that relate the metric values to predicted mean opinion scores (MOS) and account for saturations in the HVS. The evaluation of prediction performance of NHIQM and the L_p-norm reveals their excellent correlation with human perception in terms of accuracy, monotonicity, and consistency. This holds not only for the prediction performance on images taken for the training of the metrics but also for the generalization to unknown images. In addition, it is shown that the NHIQM approach and the perceptual relevance weighted L_p-norm outperform other prominent objective quality metrics in prediction performance.

  • 78. Engelke, Ulrich
    et al.
    Maeder, Anthony
    Zepernick, Hans-Jürgen
    On Confidence and Response Times of Human Observers in Subjective Image Quality Assessment2009Conference paper (Refereed)
    Abstract [en]

    Mean opinion scores obtained in subjective image quality experiments are widely accepted as measures of perceived visual quality. They have, however, a strong limitation regarding the reliability of the rated quality, since there is no explicit information as to whether the human observer experienced difficulties when judging image quality. We thus suggest that additional information about the observers confidence should be provided along with the actual quality measure. In this paper, we analyse two ways of obtaining this confidence measure; firstly as a confidence score given by the human observer and secondly as an indirect measure of the observers response time to provide the quality score. We reveal strong relationships of confidence scores and response times to the quality scores. We further propose a model to predict observer confidence based on the quality scores and response times.

  • 79. Engelke, Ulrich
    et al.
    Maeder, Anthony
    Zepernick, Hans-Jürgen
    The Effect of Spatial Distortion Distributions on Human Viewing Behaviour when Judging Image Quality2009Conference paper (Refereed)
    Abstract [en]

    In wireless communication, distortions are induced into an image through both lossy source coding and an error prone channel. The combination thereof causes complex distortion patterns in the visual content which vary strongly in their spatial distribution, some being uniformly spread and others being locally clustered. In the context of image quality, it is of interest to identify as to how the distribution of the distortions impact on the visual attention of human observers and thus on the perceived quality. For this reason, we conducted an experiment in which fifteen participants were asked to rate the quality of eighty distorted images and their corresponding reference images, while we recorded their gaze patterns using an eye tracker. The test images contained a wide range of artifact magnitudes, both locally and globally distributed, and were created using a wireless channel simulation model. We then correlate the visual gaze patterns of the human observers with local energy measures of the distortions in order to identify the effect of distortion distributions on the viewing behaviour of human observers when judging image quality. The outcomes serve to improve the prediction performance of objective image quality metrics that we previously proposed.

  • 80. Engelke, Ulrich
    et al.
    Maeder, Anthony
    Zepernick, Hans-Jürgen
    Visual Attention Modelling for Subjective Image Quality Databases2009Conference paper (Refereed)
    Abstract [en]

    The modelling of perceptual image quality metrics has experienced increased effort in recent years. In order to allow for model design, validation, and comparison, a number of subjective image quality databases has been made available to the research community. Most metrics that were designed using these databases assess the quality uniformly over the whole image, not taking into account stronger attention to salient regions of an image. In order to facilitate incorporation of visual attention (VA) into objective metric design we have conducted an eye tracking experiment. The experiment and its outcomes will be explained in detail in this paper. The actual gaze data recorded in the experiment is publicly available in order to facilitate and encourage VA modelling for image quality metrics.

  • 81. Engelke, Ulrich
    et al.
    Rossholm, Andreas
    Zepernick, Hans-Jürgen
    Lövström, Benny
    Quality Assessment of an Adaptive Filter for Artifact Reduction in Mobile Video Sequences2007Conference paper (Refereed)
    Abstract [en]

    In this paper, we examine an adaptive deblocking deringing filter for mobile video sequences in H.263 format. The considered filter has been designed with reference to the constraints of computational complexity and working memory of mobile terminals. The post filter suggested by the International Telecommunications Union (ITU) in Recommendation H.263 App. III is also included as a reference. Given that fidelity metrics such as the peak signal-to-noise ratio (PSNR) do not necessarily correlate well with video quality as experienced by the user, we consider in this paper objective quality metrics that can incorporate knowledge about the user's perception into the quality assessment. Guidelines for choosing filter parameters in relation to user-perceived video quality are obtained from the numerical results.

  • 82. Engelke, Ulrich
    et al.
    Vuong, Xuan Nguyen
    Zepernick, Hans-Jürgen
    Regional Attention to Structural Degradations for Perceptual Image Quality Metric Design2008Conference paper (Refereed)
    Abstract [en]

    In this paper, regional attention to structural degradations in images is analyzed to improve perceptual quality prediction performance of objective image quality metrics. Subjective experiments were conducted to identify regions-of-interest for a set of natural images. A region-selective metric design is then applied to four objective image quality metrics which were trained and validated with respect to quality prediction accuracy and generalization to unknown images. For this purpose, data is used from subjective quality experiments conducted at two independent laboratories. It is shown that the region-selective design is highly beneficial for the considered objective image quality metrics, in particular, prediction accuracy can be significantly increased.

  • 83. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    An Artificial Neural Network for Quality Assessment in Wireless Imaging Based on Extraction of Structural Information2007Conference paper (Refereed)
    Abstract [en]

    In digital transmission, images may undergo quality degradation due to lossy compression and error-prone channels. Efficient measurement tools are needed to quantify induced distortions and to predict their impact on perceived quality. In this paper, an artificial neural network (ANN) is proposed for perceptual image quality assessment. The quality prediction is based on structural image features such as blocking, blur, image activity, and intensity masking. Training and testing of the ANN is performed with reference to subjective experiments and the obtained mean opinion scores (MOS). It is shown that the proposed ANN is capable of predicting MOS over a wide range of image distortions. This applies to both cases, when reference information about the structure of the original image is available to the ANN but also in absence of this knowledge. The considered ANN would therefore be well suited for combination with link adaption techniques.

  • 84. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Multiobjective Optimization of Multiple Scale Visual Quality Processing2008Conference paper (Refereed)
    Abstract [en]

    In this paper, multiobjective optimization is applied to determine the optimal feature weights for a multi-resolution image quality metric. The optimization is conducted with respect to two aims; maximization of quality prediction accuracy and generalisation ability to unknown images. A thresholding of the optimal weights is applied to further reduce computational complexity of the quality metric. A detailed discussion of the tradeoff between prediction performance and complexity with respect to the threshold is provided. The metric design and evaluation is supported using mean opinion scores from subjective quality experiments that we conducted in two independent laboratories. Comparison to other state of the art quality metrics reveals the ability of the proposed metric to accurately predict subjective image quality perception.

  • 85. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Multi-resolution Structural Degradation Metrics for Perceptual Image Quality Assessment2007Conference paper (Refereed)
    Abstract [en]

    In this paper, a multi-resolution analysis is proposed for image quality assessment. Structural features are extracted from each level of a pyramid decomposition that accurately represents the multiple scales of processing in the human visual system. To obtain an overall quality measure the individual level metrics are accumulated over the considered pyramid levels. Two different metric design approaches are introduced and evaluated. It turns out that one of them outperforms our previous work on single-resolution image quality assessment.

  • 86.
    Engelke, Ulrich
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    On Perceptual Quality Evaluation of Video Applications for Wireless Ad-hoc Networks2007Conference paper (Refereed)
  • 87. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Optimal Region-of-Interest Based Visual Quality Assessment2009Conference paper (Refereed)
    Abstract [en]

    Visual content typically exhibits regions that particularly attract the viewer's attention, usually referred to as regions-of-interest (ROI). In the context of visual quality one may expect that distortions occurring in the ROI are perceived more annoyingly than distortions in the background (BG). This is especially true given that the human visual system is highly space variant in sampling visual signals. However, this phenomenon of visual attention is only seldom taken into account in visual quality metric design. In this paper, we thus provide a framework for incorporation of visual attention into the design of an objective quality metric by means of region-based segmentation of the image. To support the metric design we conducted subjective experiments to both quantify the subjective quality of a set of distorted images and also to identify ROI in a set of reference images. Multiobjective optimization is then applied to find the optimal weighting of the ROI and BG quality metrics. It is shown that the ROI based metric design allows to increase quality prediction performance of the considered metric and also of two other contemporary quality metrics.

  • 88. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Pareto Optimal Weighting of Structural Impairments for Wireless Imaging Quality Assessment2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider multiobjective optimization for obtaining the feature weights associated with structural image impairments and its application to wireless imaging quality assessment. The proposed framework supports optimization with respect to finding a trade-off between metric prediction accuracy and generalization to unknown images. Evaluation of optimal trade-off solutions for two representative scenarios reveal the benefits of the proposed approach. In particular, quality prediction accuracy of an objective image metric can be strongly increased and negligible features are identified that can be discarded to save computational complexity.

  • 89. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Perceptual-based Quality Metrics for Image and Video Services: A Survey2007Conference paper (Refereed)
    Abstract [en]

    The accurate prediction of quality from an end-user perspective has received increased attention with the growing demand for compression and communication of digital image and video services over wired and wireless networks. The existing quality assessment methods and metrics have a vast reach from computational and memory efficient numerical methods to highly complex models incorporating aspects of the human visual system. It is hence crucial to classify these methods in order to find the favorable approach for an intended application. In this paper a survey and classification of contemporary image and video quality metrics is therefore presented along with the favorable quality assessment methodologies. Emphasis is given to those metrics that can be related to the quality as perceived by the end-user. As such, these perceptual-based image and video quality metrics may build a bridge between the assessment of quality as experienced by the end-user and the quality of service parameters that are usually deployed to quantify service integrity.

  • 90.
    Engelke, Ulrich
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Quality Evaluation in Wireless Imaging Using Feature-Based Objective Metrics2007Conference paper (Refereed)
    Abstract [en]

    This paper addresses the evaluation of image quality in the context of wireless systems using feature-based objective metrics. The considered metrics comprise of a weighted combination of feature values that are used to quantify the extend by which the related artifacts are present in a processed image. In view of imaging applications in mobile radio and wireless communication systems, reduced-reference objective quality metrics are investigated for quantifying user-perceived quality. The examined feature-based objective metrics provide options for controlling the processing complexity and implementation resources required for performing the quality evaluation. Furthermore, the metrics support the scaling of overhead needed for communicating the image features over the wireless link and the accuracy for predicting the image quality.

  • 91. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Kusuma, Tubagus Maulana
    Perceptual Evaluation of Motion JPEG2000 Quality over Wireless Channels2006Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the applicability of perceptual image quality metrics for quality assessment of Motion JPEG2000 (MJ2) video streams over wireless channels. A performance evaluation of MJ2 quality for different levels of source compression and channel coding settings is provided. This reveals insights into the characteristics and suitability of the considered perceptual quality metrics for wireless video quality assessment. In particular, a reduced-reference hybrid image quality metric (HIQM) is identified as the most favorable metric with respect to supporting real-time applications. The findings obtained from the considered scenarios may also guide the design of efficient physical layer functions for wireless video systems.

  • 92. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Maeder, Anthony
    Visual Attention Modeling: Region-of-Interest Versus Fixation Patterns2009Conference paper (Refereed)
    Abstract [en]

    Visual attention (VA) is an integral property of the human visual system. The deployment of a VA model can be beneficial for many image and video applications, such as, compression, transmission, and quality assessment. However, the design of a VA model is highly dependent on the subjective VA data used as ground truth and the application that the model is intended for. In this paper, we discuss two ways of obtaining subjective VA data that can subsequently be used to develop VA models; selective regions-of-interest and visual fixation patterns. The feasibility of both methods will be discussed, in particular, with respect to visual quality assessment.

  • 93.
    Erdogan, Ferhat
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Implementation and Comparison of Motion Estimation Algorithms for Video Coding2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    In video coding, motion compensated prediction between the frames is a very efficient way for exploiting temporal correlation. Different motion estimation algorithms have been developed in order to provide efficient motion compensated prediction of scene motion between frames. In this thesis, full search, fast search, hierarchical search, sub pixel interpolation and mesh based motion estimation algorithms have been implemented. Comparisons are made both in the spatial and temporal domain, mainly in terms of Peak Signal to Noise Ratio (PSNR) and computational complexity. A video codec using lifting based wavelet transform is used for the comparisons in the temporal domain.

  • 94. Erman, Maria
    et al.
    Mohammed, Abbas
    Rakus-Andersson, Elisabeth
    Fuzzy Logic Applications in Wireless Communications2009Conference paper (Refereed)
    Abstract [en]

    A survey of fuzzy logic applications and principles in wireless communications is presented, with the aim of highlighting successful usage of fuzzy logic techniques in applied telecommunications and signal processing. To the best of our knowledge, this is the first such study of its kind. This paper will focus firstly on discerning prevalent fuzzy logic or fuzzy-hybrid approaches in the areas of channel estimation, channel equalization and decoding, and secondly outlining what conditions and situations for which fuzzy logic techniques are most suited for these approaches. Furthermore, after insights gained from isolating fuzzy logic techniques applied to real problems, this paper proposes areas for further research targeted to practice-oriented researchers.

  • 95.
    Eskilsson, Eric
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Styrprogram till PIC-processorer för fjärrmanövrerad relämatris2008Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Abstract The aims with this report are to document the upgrade and development of new software for the distance laboratory at Blekinge Tekniska Högskola. The work has been focused on implementing the identification number in a microcontroller, to read its data from a so called look-up table and to be able to control digital components through a serial bus (SPI). The look-up table is a list of data from which the software reads data for the different types of printed circuit boards in the hardware component of the distance laboratory is in focus. The results of the report are an implemented, upgraded version of the software and all three aims has been accomplished. Sammanfattning Syftet med detta arbete har varit att utveckla och uppgradera en ny mjukvara till distanslaboaratoriet på Blekinge Tekniska Högskola, genom att implementera adressen till en microcontroller, att läsa dess data från en så kallad look-up table, samt att kunna styra digitala komponenter med en seriell buss (SPI). Fokus i programmeringen har legat på look-up table, vilket är en datalista som mjukvaran läser funktionsdata från för de olika korttyperna i matrisen. Resultatet är en implementerad, uppgraderad version av mjukvaran och alla tre målen har gått att genomföra.

  • 96. Fiedler, Markus
    Euro-NGI D.JRA.6.1.1: State-of-the-art with regards to user-perceived Quality of Service and quality feedback2004Other (Other academic)
    Abstract [en]

    This deliverable D.JRA.6.1.1 presents a review of the state-of-the-art with regards to Quality of Service from the user's perspective and quality feedback, which is the topic of the corresponding work package WP.JRA.6.1 as part of the Joint Research Activity "Socio-Economic Aspects of Next Generation Internet" of the Network of Excellence "Euro-NGI". The document contains a survey of Quality of Service-related standards and discusses the current status regarding Quality of Servce in the Internet. The central role of the user is highlighted, and methods how to relate user perception to technical parameters on application and network level are discussed. Furthermore, currently existing quality feedback and management facilities in Internet are reviewed. Complementary work of the involved partners within these fields is presented, showing the broad range of compentence of the partners within the scope of JRA.6.1. Finally, relevant research issues are identified, providing a promising basis for future joint research.

  • 97. Fiedler, Markus
    Traffic Measurement and Characterization2004In: COST 279 - Midterm Report: Analysis and Design of Advanced Multiservice Networks Supporting Mobility, Multimedia, and Internetworking / [ed] Committee, COST 279 Management; Menth, M., Roma: ARACNE editrice S.r.l. , 2004, p. 49-73Chapter in book (Other academic)
    Abstract [en]

    We observe currently a fast evolution of web, multimedia, and especially peer-to-peer applications. This evolution yields a rapidly changing load environment for the transport of data streams subject to severe Quality of Service (QoS) constraints. Considering the needs for traffic planning and QoS assessment in wired and wireless access, as well as backbone networks, issues like load modeling and traffic characterization by thorough statistical techniques have to be addressed as the first basic steps of teletraffic engineering. For this purpose, new and reliable traffic measurement, modeling, and estimation techniques are required to accurately determine the traffic load and the resource usage in wired and wireless networks. The goal of this chapter consists in providing a comprehensive overview on related activities within the COST 279 action. Its structure reflects natural steps of obtaining results: traffic measurement, which concerns rather technical issues related to the collection of traffic and its statistics; traffic characterization, to provide a rather qualitative desciption of traffic behavior; traffic modeling, to provide a rather quantitative description with focus on models and their parameters; and traffic estimation, which is about inference and prediction of traffic volumes based on observations.

  • 98.
    Fiedler, Markus
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Lundberg, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Arlos, Patrik
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Pettersson, Mats
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    QoE-based Cross-Layer Design of Mobile Video Systems: Challenges and Concepts2009Conference paper (Refereed)
    Abstract [en]

    This conceptual paper focuses on revealing challenges and offering concepts associated with the incorporation of the Quality of Experience (QoE) paradigm into the design of mobile video systems. The corresponding design framework combines application, middleware and networking layer in a unique cross-layer approach, in which all layers shall jointly analyse the quality of the video and its delivery in face of volatile conditions. Particular ingredients of the framework are efficient video processing, advanced realtime scheduling, and reduced-reference metrics on application and network layer.

  • 99.
    Fontecha, Gorka Treceño
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Barbero., Beatriz Mora
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Examination of Various Approaches to Possibly Improve the Existing Algorithms Applied in Fingerprint Recognition Systems2007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    In human fingerprints there are plenty of small details which are the discontinuities in the ridges, denoted minutiae. Minutiae-based matching is a wellknown method applied in fingerprint recognition. Minutiae defines a representative feature vector of a fingerprint. Due to quality variations in fingerprint images a preprocessing in form of binarization and skeltonization is applied, before obtaining the feature vector. Once the features of each fingerprint are obtained, a matching algorithm carries out the comparison task between those features vectors to determine if they match. In the new binarization function, quality at the same time that speed are essential requirements. In order to sort out this subject, areas of an adaptive size are analyzed instead of a pixel by pixel examination. The binarization algorithm is implemented in the frequency domain with the concept of ridges and their orientations. Skeletonization is needed as a preprocessing step with the aim of obtaining the minutiae from the fingerprint. It is a matter of fact that the high quality skeleton is an emphatic factor in the fingerprint recognition. A robust skeletoned image will ensure a reliable extraction of features. Several strategies relating to the application of filters will be discussing in order to speed-up the iteractive thinning algorithms. The proposed minutiae matching algorithms explore though several variations of the geometric hashing method. Based on minutiae features, new approaches are presented to obtain an effectiveness function.

  • 100.
    Gabriel, Karim
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Moudarres, Sani Al
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    The development of a Speech Level Adjustment Technique for late Deaf People2009Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    People that become deaf later on in life do have the ability to speak with correct pronunciation but since they can not hear their own voice nor the noise in the enviroment, they have difficulties to adjust their voice level to the surrounding environment. In this thesis we propose and algorithm which can be used on a prototype to help the late deafened people to adjust their voice level to the surrounding.

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