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  • 251.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Bao, Vo Nguyen Quoc
    Tran, Hung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Effect of primary network on performance of spectrum sharing AF relaying2012Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 48, nr 1, s. 25-U95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most of the research in spectrum sharing has neglected the effect of interference from primary users. In this reported work, the performance of spectrum sharing amplify-and-forward relay networks under interference-limited environment, where the interference induced by the transmission of primary networks is taken into account, is investigated. In particular, a closed-form expression tight lower bound of outage probability is derived. To reveal additional insights into the effect of primary networks on the diversity and array gains, an asymptotic expression is also obtained.

  • 252. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Tran, Nguyen Nam
    Ergodic Capacity of Cooperative Networks Using Adaptive Transmission and Selection Combining2009Konferensbidrag (Refereegranskat)
    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

  • 253. 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 Channels2009Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 13, nr 3, s. 172-174Artikel i tidskrift (Refereegranskat)
    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

  • 254. Duong, Quang Trung
    et al.
    Engelke, Ulrich
    Zepernick, Hans-Jürgen
    Cooperative Wireless Communications with Unequal Error Protection and Fixed Decode-And-Forward Relays2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we examine an unequal error protection (UEP) scheme for wireless imaging that is based on utilizing the distributed diversity offered by decode-and-forward (DF) networks. Specifically, the data stream after source encoding is divided into high and low priority sub-streams depending on their importance for image reconstruction. A relay-selection combining (R-SC) scheme is exploited for high priority image data to achieve high reliability while cooperative spatial multiplexing is employed to low priority image data to support high spectral efficiency. In this work, we specifically take into account the setting that relays may forward erroneously detected signals to the destination when cooperating with fixed DF. In this context, the analytical and numerical results validate that R-SC outperforms other relaying protocols in terms of average symbol error probability while the considered UEP approach offers the highest spectral efficiency among the examined relaying schemes.

  • 255. Duong, Quang Trung
    et al.
    Engelke, Ulrich
    Zepernick, Hans-Jürgen
    Unequal Error Protection for Wireless Multimedia Transmission in Decode-and-Forward Relay Networks2009Konferensbidrag (Refereegranskat)
    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.

  • 256. Duong, Quang Trung
    et al.
    Ha, Dac-Binh
    Tran, Hoai-An
    Vo, Nguyen-Son
    Symbol Error Probability of Distributed-Alamouti Scheme in Wireless Relay Networks2008Konferensbidrag (Refereegranskat)
    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.

  • 257. Duong, Quang Trung
    et al.
    Ha, Dac-Binh
    Tran, Hoai-An
    Vo, Nguyen-Son
    Haroon, Ahsan
    On The Symbol Error Probability of Distributed-Alamouti Scheme2009Ingår i: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 4, nr 7, s. 437-444Artikel i tidskrift (Refereegranskat)
    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.

  • 258. Duong, Quang Trung
    et al.
    Hoang, Le-Nam
    Bao, Vo Nguyen Quoc
    On the Performance of Two-Way Amplify-and-Forward Relay Networks2009Ingår i: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E92-B, nr 12, s. 3957-3959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of two-way amplify-and-forward (AF) relay networks is presented. In particular, we derive exact closed-form expressions for symbol error rate (SER), average sum-rate, and outage probability of two-way AF relay systems in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels. Our analysis is validated by a comparison against the results of Monte-Carlo simulations.

  • 259. Duong, Quang Trung
    et al.
    Le, Thanh-Tan
    Zepernick, Hans-Jürgen
    Performance of Cognitive Radio Networks with Maximal Ratio Combining over Correlated Rayleigh Fading2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we apply the maximal ratio combining (MRC) technique to achieve higher detection probability in cognitive radio networks over correlated Rayleigh fading channels. We present a simple approach to derive the probability of detection in closed-form expression. The numerical results reveal that the detection performance is a monotonically increasing function with respect to the number of antennas. Moreover, we provide sets of complementary receiver operating characteristic (ROC) curves to illustrate the effect of antenna correlation on the sensing performance of cognitive radio networks employing MRC schemes in some respective scenarios.

  • 260. 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 Networks2009Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 51, nr 2, s. 231-244Artikel i tidskrift (Refereegranskat)
    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.

  • 261. Duong, Quang Trung
    et al.
    Suraweera, Himal A.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Nallanathan, Arumugam
    OSTBC Transmission in MIMO AF Relay Systems with Keyhole and Spatial Correlation Effects2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the degenerative effects of antenna correlation and keyhole on the performance of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks. In particular, we considered a downlink MIMO AF relay system consisting of an nS-antenna base station S, an nR-antenna relay station R, and an nD-antenna mobile station D, in which the signal propagation originated from the mobile station suffers from keyhole and spatial correlation effects. We have derived an exact expression for the moment generation function of the instantaneous signal-to-noise ratio which enables us to analyze the symbol error probability and outage probability of the considered system.We have shown that although the mobile station is in a poor scattering environment, i.e., keyhole, the relay channel (S → R → D link) still achieves a cooperative diversity order of min(nR, nD) provided that the channel from the source (S → R link) is keyhole-free. This result is important to radio system designers since under such a severe scenario it is unnecessary to deploy a large number of antennas on the relay station (nR) but only requires nR = nD to obtain the maximum achievable diversity gain.

  • 262. Duong, Quang Trung
    et al.
    Tran, Hoai-An
    Distributed Space-Time Block Codes with Amicable Orthogonal Designs2008Konferensbidrag (Refereegranskat)
    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.

  • 263.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Yeoh, Phee Lep
    Vo, Nguyen Quoc Bao
    Elkashlan, Maged
    Yang, Nan
    Cognitive Relay Networks With Multiple Primary Transceivers Under Spectrum-Sharing2012Ingår i: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, nr 11, s. 741-744Artikel i tidskrift (Refereegranskat)
    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.

  • 264. Duong, Quang Trung
    et al.
    Yuen, Chau
    Zepernick, Hans-Jürgen
    Lei, Xianfu
    Average Sum-Rate of Distributed Alamouti Space--Time Scheme in Two-Way Amplify-and-Forward Relay Networks2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose a distributed Alamouti space-time code (DASTC) for two-way relay networks employing a single amplify-and-forward (AF) relay. We first derive closed-form expressions for the approximated average sum-rate of the proposed DASTC scheme. Our analysis is validated by a comparison against the results of Monte-Carlo simulations. Numerical results verify the effectiveness of our proposed scheme over the conventional DASTC with one-way communication.

  • 265. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Adaptive Transmission Scheme for Wireless Cooperative Communications2009Konferensbidrag (Refereegranskat)
    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.

  • 266. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Cross-Layer Design for MRT Systems with Channel Estimation Error and Feedback Delay2011Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 58, nr 4, s. 681-694Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we analyze the effect of channel estimation error and delayed feedback on the performance of a cross-layer scheme combining adaptive modulation for maximum ratio transmission (MRT) at the physical layer and truncated automatic repeat request (T-ARQ) at the link layer. The cross-layer attempts to maximize the spectral efficiency under predetermined quality of service requirements, namely, delay and packet-loss constraints. In particular, we derive closed-form expressions for the average packet error rate, average achievable spectral efficiency, and the outage probability, hence, enabling to evaluate the performance of the cross-layer scheme in the presence of imperfect channel estimation at the receiver and delayed feedback path between the receiver and transmitter. The final expressions are given in terms of the minimum and maximum number of transceiver antennas as well as the channel estimation error and feedback delay parameters. We further show that with a small amount of channel estimation error and/or feedback delay the system performance is severely degraded. Specifically, numerical results demonstrate that with channel estimation error and feedback delay the performance of the cross-layer scheme is even worse than that of T-ARQ only. We also observe an irreducible outage probability floor appearing in the high signal-to-noise regime.

  • 267. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Hybrid Decode-Amplify-Forward Cooperative Communications with Multiple Relays2009Konferensbidrag (Refereegranskat)
    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.

  • 268. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Ergodic Capacity of Cooperative Spatial Multiplexing Systems in Composite Channels2009Konferensbidrag (Refereegranskat)
    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

  • 269. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    On the Performance Gain of Hybrid Decode-Amplify-Forward Cooperative Communications2009Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2009Artikel i tidskrift (Refereegranskat)
    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.

  • 270. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Performance Analysis of Cooperative Spatial Multiplexing with Amplify-and-Forward Relays2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cooperative spatial multiplexing (CSM) systems can achieve high spatial multiplexing gain in wireless relay networks since each single-antenna relay forwards simultaneously a different subset of source messages to the destination. In this paper, the performance of CSM with amplify-and-forward (AF) relays are presented. Specifically, we derive exact closed-form expressions for symbol error probability (SEP) and achievable spectral efficiency of CSM with linear receiver in dissimilar Rayleigh fading channels. Assessing the SEP performance in the high signal-to-noise regime, we further show that CSM with AF relays obtains the first order of diversity gain. Furthermore, it has been observed that CSM outperforms two well-known cooperative diversity systems, e.g., selection combining and maximal ratio combining, in term of spectral efficiency. We also perform Monte-Carlo simulations to validate our analysis.

  • 271. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Bao, Vo Nguyen Quoc
    Symbol error probability of hop-by-hop beamforming in Nakagami-m fading2009Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, nr 20, s. 1042-1044Artikel i tidskrift (Refereegranskat)
    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.

  • 272. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Fiedler, Markus
    Cross-Layer Design for Integrated Mobile Multimedia Network with Strict Priority Traffic2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In mobile multimedia networks, different traffic classes require various levels of quality of service (QoS). In this paper, we propose a cross-layer design to provide diverse QoS provisions for integrated realtime/non-realtime traffic by jointly taking into account the physical layer, data link layer, and application layer. Specifically, at the physical layer, adaptive modulation and coding (AMC) is employed to cope with the time-varying nature of fading channels whereas impairments due to queuing effects are considered at the data link layer. At the application layer, realtime and non-realtime traffic are classified into high and low priority classes, respectively, with strict priority levels. The cross-layer scheme is characterized as a discrete Markov modulated Poisson process. Solving the steady state probability of this Markov model readily enables us to investigate several important performance metrics such as packet drop rate due to buffer overflow and packet error rate due to transmission errors and network impairments. Our proposed cross-layer design is verified by comparing the analytical results with Monte-Carlo simulations. Furthermore, it has been shown that the proposed cross-layer design can flexibly guarantee QoS requirements for each traffic class.

  • 273. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Tsiftsis, Theodoros A.
    Bao, Vo Nguyen Quoc
    Amplify-and-Forward MIMO Relaying with OSTBC over Nakagami-m Fading Channels2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we analyze the performance of dual-hop channel state information (CSI)-assisted amplify-andforward (AF) cooperative networks using orthogonal space-time block codes (OSTBCs) over independent but not identically distributed Nakagami-m fading channels. Specifically, we present closed-form expressions of the outage probability (OP) and the symbol error probability (SEP). The analytical results are given in tractable forms which readily allow us to assess the performance of AF relay systems using OSTBCs. For sufficiently large signal-to-noise ratio, we obtain the asymptotic results for OP and SEP which reveal insights into the effect of fading factors on the diversity and coding gains. It has been shown that between the two hops the more severe link solely determines the diversity and coding gains. In particular, these two gains strictly depend on the fading severity parameters and the channel mean powers of the more rigorous hop, respectively. Numerical results are provided showing an excellent agreement between our analytical results and those of Monte-Carlo simulations for selected scenarios.

  • 274. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Tsiftsis, Theodoros A.
    Bao, Vo Nguyen Quoc
    Performance Analysis of Amplify-and-Forward MIMO Relay Networks with Transmit Antenna Selection over Nakagami-m Channels2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    We analyze the performance of amplify-and-forward (AF) multiple-input multiple-output (MIMO) cooperative networks over independent but not identically distributed Nakagami-$m$ fading channels. Specifically, we consider an AF MIMO relay network where the source deploys the transmit antenna selection scheme to communicate with the destination through the help of a relay. We derive closed-form approximations for outage probability (OP) and symbol error probability (SEP). Moreover, asymptotically tight approximations for OP and SEP have been obtained to facilitate insights on how fading parameters affect the performance. Our analytical results are verified by Monte-Carlo simulations for respective scenarios.

  • 275.
    Duong, Trung Quang
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Duy, Tran Trung
    Matthaiou, Michail
    Tsiftsis, Theodoros
    Karagiannidis, George K.
    Cognitive Cooperative Networks in Dual-Hop Asymmetric Fading Channels2013Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, s. 955-961Konferensbidrag (Refereegranskat)
    Abstract [en]

    Previous works on cognitive relay networks (CRNs) considered only symmetric fading channels. However, in practical wireless propagation scenarios, it is likely that the channels of the secondary user (SU) and primary user (PU) may undergo different fading characteristics. In this paper, we assume that the channels of the secondary network (SU-source -> SU-relay -> SU-destination) are subject to Rician fading, whereas the channels of the link from the SU to the PU experience Rayleigh fading. Based on this framework, the end-to-end outage probability (OP) of CRNs is investigated for two different relaying schemes: i) in the absence of the direct link with decode-and-forward (DF) protocol and ii) in the presence of the direct link with incremental DF protocol. In particular, we derive both exact and asymptotic OP expressions for the considered CRNs. Our analysis reveals important insights into the impact of fading parameters on the CRN performance under distinct fading distributions.

  • 276.
    Dziak, Damian
    et al.
    Politechnika Gdanska, POL.
    Jachimczyk, Bartosz
    BetterSolutions S.A., POL.
    Bork-Ceszlak, Krzysztof
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Zydanowicz, Tadeusz
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Kulesza, Wlodek
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Wireless monitoring system for fireman's competence objective assessment2017Ingår i: Elektronika ir Elektrotechnika, ISSN 1392-1215, Vol. 23, nr 4, s. 56-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Developing technologies associated with tracking human movement and behaviour enable new applications for competence assessments from training results of professionals, such as medical staff, sportsmen or emergency servicemen. This article considers a methodological approach to design a system for firefighter's skills and competence assessment. Assessed training features such as in-building behaviour and tasks execution are analysed based on data gathered with wireless Ultra-Wideband Real-Time Location System, UWB RTLS, and Inertial Measurement Unit, IMU. The assessment is based on the predefined required training tasks, the expert's expertise and results of the trainee's test. The Unity game engine is used for data processing and visualization. As the comprehensive final map of the trainee's skills, the spider diagram is applied and the single score method provides the conclusive statement. The proposed solution was verified experimentally in real environment.

  • 277.
    Dziak, Damian
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Jachimczyk, Bartosz
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Jagusiak, Tomasz
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Automatic Waterjet Positioning Vision System2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The goals of this work are a design and implementation of a new vision system, integrated with the waterjet machine. This system combines two commercial webcams applied on an industrial dedicated platform. A main purpose of the vision system is to detect the position and rotation of a workpiece placed on the machine table. The used object recognition algorithm consists of edge detection, standard math processing functions and noise filters. The Hough transform technique is used to extract lines and their intersections of a workpiece. Metric rectification method is used, in order to obtain a top view of the workspace and to adjust an image coordinate system, accordingly to the waterjet machine coordinates. In situ calibration procedures of the booth webcams are developed and implemented. Experimental results of the proposed new vision system prototype confirm required performance and precision of the element detection.

  • 278.
    Dziak, Damian
    et al.
    Politechnika Gdanska, POL.
    Jachimczyk, Bartosz
    BetterSolutions S.A., POL.
    Kulesza, Wlodek
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    IoT-based information system for healthcare application: Design methodology approach2017Ingår i: Applied Sciences, E-ISSN 2076-3417, Vol. - 7, nr - 6, artikel-id 596Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    - Over the last few decades, life expectancy has increased significantly. However, elderly people who live on their own often need assistance due to mobility difficulties, symptoms of dementia or other health problems. In such cases, an autonomous supporting system may be helpful. This paper proposes the Internet of Things (IoT)-based information system for indoor and outdoor use. Since the conducted survey of related works indicated a lack of methodological approaches to the design process, therefore a Design Methodology (DM), which approaches the design target from the perspective of the stakeholders, contracting authorities and potential users, is introduced. The implemented solution applies the three-axial accelerometer and magnetometer, Pedestrian Dead Reckoning (PDR), thresholding and the decision trees algorithm. Such an architecture enables the localization of a monitored person within four room-zones with accuracy; furthermore, it identifies falls and the activities of lying, standing, sitting and walking. Based on the identified activities, the system classifies current activities as normal, suspicious or dangerous, which is used to notify the healthcare staff about possible problems. The real-life scenarios validated the high robustness of the proposed solution. Moreover, the test results satisfied both stakeholders and future users and ensured further cooperation with the project. © 2017 by the authors.

  • 279.
    E., Okwelume Gozie
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Kingsley, Ezeude Anayo
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    BLIND SOURCE SEPARATION USING FREQUENCY DOMAIN INDEPENDENT COMPONENT ANALYSIS2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    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

  • 280.
    EDAMAKANTI, BHANUDURGA SRI SATYA SIMHA
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    GUNDU, VISHNU CHAITANYA
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Subband Adaptive Filtering Technique employing APA For Stereo Echo Cancellation over Audio Signals2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The world today is relying on hands free devices and teleconferencing equipments but the major problem with the use of these systems is creation of acoustic echo at the time of conversation. The quality of information to be transmitted and received is degraded due to the echo. Hence, echo cancellation has come up as the most interesting as well as challenging part in any communication system. Echo is the degraded or delayed version of an original signal which comes back to the source after successive reflections from the surroundings. The removal of echo without degrading the quality of an original signal is a challenge of research in present time. Echo cancellation in case of voice communication is removal of echo, improving the quality of an original voice signals. In our thesis we have focused on the acoustic echo cancellation in closed room with the help of adaptive filters. Stereo echo cancellation is a key technique for solving the echo problem in modern teleconferencing systems. There is a fundamental problem in stereo echo cancellation, the misalignment between the converged filter weights and the real room impulse responses. Most existing works explain the misalignment problem by a conceptual stochastic equation, and no studies have investigated the closed form of the final weights in a stereo echo canceller. In our thesis we have proposed a subband adaptive modeling approach to develop an effective system of stereo echo cancellation with the help of better adaptive filtering techniques. We have adopted the subband adaptive modeling because the fullband adaptive modeling technique may not be able to characterize the electro-acoustic performance of a Multichannel Compression Hearing Aid (MCHA). We also employ the design of DFT filter banks for the analysis and synthesis of the signal and in the place of conventional NLMS or RLS algorithm; we have rather employed the APA (Affine Projection Algorithm) for adaptive modeling in each subband. The performance of the subband adaptive modeling is simulated under various conditions in MATLAB and the results are analyzed. The performance of the subband adaptive modeling system is better and effective as compared to the fullband adaptive modeling system. The results for various input and noise signals are plotted and shown in result section of this report.

  • 281.
    EGEREGOR, DAFE
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    NUMERICAL SIMULATION OF HEAT TRANSFER AND PRESSURE DROP IN PLATE HEAT EXCHANGERS USING FLUENT AS CFD TOOL2008Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    As shown from the study, different geometries give different results at different flow conditions (Reynolds number/ mass-flow rate). The choice of appropriate plate geometry does not always depend on high Nusselt number values, but predictability and almost constant behaviour through a large Reynolds number range, plays an important role as shown by the chevron design.

  • 282.
    Elhag, Omer
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Fast Back Projection Algorithm for Bi-Static SAR Using Polar Coordinates2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Synthetic Aperture Radar (SAR) plays a significant role in geophysical studies and remote sensing applications. SAR inherits the benefits of imaging RADAR over the other optical sensors such as working in all weather conditions and working independently of sunlight. In addition to these benefits SAR generates a finer resolution 2-D image compared to conventional (real) aperture radar. Due to the sole merits of Ultrawideband-Ultrawidebeam (UWB) Bistatic SAR, this thesis introduces and analyzes a fast time domain algorithm for its image formation. This algorithm inherits the advantages of time-domain algorithms over frequency domain ones. It divides the full synthetic aperture into subapertures. Each subaperture generates a polar grid image. The key point is that the subaperture polar images have very low resolution in cross range (the angular direction); this means that they can be calculated on a pixel grid that is coarse in the angular direction. The final image is obtained by combining all subaperture polar images after converting them to the final high-resolution Cartesian image, in this conversion interpolation is used. Since the subaperture images contain far fewer pixels in cross range than the final image, far fewer operations are required to be executed as compared to Global Backprojection GBP. Due to using the polar grid, the proposed algorithm is named Bistatic Polar-FBP (Bi-PFBP). It is found that although for N×N scene image with N aperture positions the Bi-PFBP computational load is less by approximately a factor of √N as compared to GBP, the image quality generated by each one of them is almost the same.

  • 283.
    Elisabeth, Källström
    et al.
    Volvo, SWE.
    John, Lindström
    Luleå tekniska Universitet, SWE.
    Lars, Håkansson
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Magnus, Karlberg
    Luleå tekniska Universitet, SWE.
    Renderstedt, Reza
    Volvo, SWE.
    Larsson, Jonas
    Volvo, SWE.
    Identification of vibration properties of heavy duty machine driveline parts as a base for adequate condition monitoring: Axle2016Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics / [ed] Vogiatzis, K; Kouroussis, G; Crocker, M; Pawelczyk, M, INT INST ACOUSTICS & VIBRATION , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    With increasing complexity in the heavy duty construction equipment, early fault detection of certain components in the machine becomes more and more challenging due to too many fault codes generated when a failure occurs. The axle is one such component. The axle transfers driving torque from the transmission to the wheels and axle failure may result in costly downtime of construction equipment. To reduce service cost and to improve uptime, adequate condition monitoring based on sensor data from the axle is considered by for instance measuring vibrations on the axle. Further, the analysis of the data collected has been has been carried out using adequate signal processing methods. The results indicate that the vibration properties of the axle are relevant for early fault detection of the axle. Thus, the health of the axle may be continuously monitored on-board using the vibration information and if the axle health starts to degrade a service and/or repair may be scheduled well in advance of a potential axle failure and in that way the downtime of a machine may be reduced and costly replacements and repairs avoided.

  • 284.
    Elnourani, Mohamed
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    COGNITIVE RADIO AND GAME THEORY: OVERVIEW AND SIMULATION2008Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    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.

  • 285. Emam, Seyed Mohammad
    et al.
    Khatibi, Siamak
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Khalili, Khalil
    Improving the Accuracy of Laser Scanning for 3D Model Reconstruction Using Dithering Technique2014Ingår i: Procedia Technology / [ed] Moldovan, L, Elsevier , 2014, Vol. 12Konferensbidrag (Refereegranskat)
    Abstract [en]

    Triangulation technique is one of the most commonly techniques used in three dimensional measurements. Depth reconstruction accuracy is a direct impact of the quantization process and this is related to the number of pixels of the sensor. Dithering technique (DT) benefits from relative fine movement between object and sensor to reduce the quantization error. This paper describes the theory of the DT and establishes a mathematical model. To evaluate if DT technique can improve the accuracy in real world, a control rig was designed and built, following which experiments were performed. The results showed that considerable improvement can be achieved in measurement accuracy.

  • 286.
    Emani, Harsha Yashaskar
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Identification and Masking Method of Clouds in Satellite Images2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Identification of the cloud in an image is essential in order to remove the noise in the image and improve the quality of the image. Further the masking of cloud in a satellite image is important in order to obtain a clear image taken from a remote sensing satellite. This thesis presents the identification of cloud in a satellite image, to segregate the cloud part of the image from non-cloud part of the same image like soil, vegetation, water by using certain techniques. Region of interest (ROI) selection technique is used to obtain the desired cloud image from the actual image. To obtain cloud image from non-cloud image masking methods such as automatic masking and manual masking are used in ROI selection technique. A suitable image is obtained from the sensor known as ‘Moderate Resolution Imaging Spectroradiometer’ (MODIS). The manual and automatic masked cloud images are compared and the performance of the cloud masking methods is evaluated. The evaluation of the results indicates that the cloud images are possible to obtained by ROI selection technique through automatic masking and manual cloud masking method.

  • 287. Enflo, Bengt
    et al.
    Hedberg, Claes
    Theory of Nonlinear Acoustics in Fluids2002Bok (Övrigt vetenskapligt)
    Abstract [sv]

    Boken beskriver på ett enhetligt sätt ickelinjär akustik i gaser och vätskor (fluider) med lika stor vikt på matematik som fysik.

  • 288. Engelke, Ulrich
    Modelling Perceptual Quality and Visual Saliency for Image and Video Communications2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The evolution of advanced radio transmission technologies for third and future generation mobile radio systems has paved the way for the delivery of mobile multimedia services. This is further enabled through contemporary video coding standards, such as H.264/AVC, allowing wireless image and video applications to become a reality on modern mobile devices. The extensive amount of data needed to represent the visual content and the scarce channel bandwidth constitute great challenges for network operators to deliver an intended quality of service. Appropriate metrics are thus instrumental for service providers to monitor the quality as experienced by the end user. This thesis focuses on subjective and objective assessment methods of perceived visual quality in image and video communication. The content of the thesis can be broadly divided into four parts. Firstly, the focus is on the development of image quality metrics that predict perceived quality degradations due to transmission errors. The metrics follow the reduced-reference approach, thus, allowing to measure quality loss during image communication with only little overhead as side information. The metrics are designed and validated using subjective quality ratings from two experiments. The distortion assessment performance is further demonstrated through an application for filter design. The second part of the thesis then investigates various methodologies to further improve the quality prediction performance of the metrics. In this respect, several properties of the human visual system are investigated and incorporated into the metric design. It is shown that the quality prediction performance can be considerably improved using these methodologies. The third part is devoted to analysing the impact of the complex distortion patterns on the overall perceived quality, following two goals. Firstly, the confidence of human observers is analysed to identify the difficulties during assessment of the distorted images, showing, that indeed the level of confidence is highly dependent on the level of visual quality. Secondly, the impact of content saliency on the perceived quality is identified using region-of-interest selections and eye tracking data from two independent subjective experiments. It is revealed, that the saliency of the distortion region indeed has an impact on the overall quality perception and also on the viewing behaviour of human observers when rating image quality. Finally, the quality perception of H.264/AVC coded video containing packet loss is analysed based on the results of a combined subjective video quality and eye tracking experiment. It is shown that the distortion location in relation to the content saliency has a tremendous impact on the overall perceived quality. Based on these findings, a framework for saliency aware video quality assessment is proposed that strongly improves the quality prediction performance of existing video quality metrics.

  • 289. Engelke, Ulrich
    Perceptual Quality Metric Design for Wireless Image and Video Communication2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 290. Engelke, Ulrich
    et al.
    Barkowsky, Marcus
    Callet, Patrick Le
    Zepernick, Hans-Jürgen
    Modelling Saliency Awareness for Objective Video Quality Assessment2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Existing video quality metrics do usually not take into consideration that spatial regions in video frames are of varying saliency and thus, differently attract the viewer's attention. This paper proposes a model of saliency awareness to complement existing video quality metrics, with the aim to improve the agreement of objectively predicted quality with subjectively rated quality. For this purpose, we conducted a subjective experiment in which human observers rated the annoyance of videos with transmission distortions appearing either in a salient region or in a non-salient region. The mean opinion scores confirm that distortions in salient regions are perceived much more annoying. It is shown that application of the saliency awareness model to two video quality metrics considerably improves their quality prediction performance.

  • 291. Engelke, Ulrich
    et al.
    Kaprykowsky, Hagen
    Zepernick, Hans-Jürgen
    Ndjiki-Nya, Patrik
    Visual Attention in Quality Assessment2011Ingår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 28, nr 6, s. 50-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Perceptual quality metrics are widely deployed in image and video processing systems. These metrics aim to emulate the integral mechanisms of the human visual system (HVS) to correlate well with visual perception of quality. One integral property of the HVS is, however, often neglected: visual attention (VA) [1]. The essential mechanisms associated with VA consist mainly of higher cognitive processing, deployed to reduce the complexity of scene analysis. For this purpose, a subset of the visual information is selected by shifting the focus of attention across the visual scene to the most relevant objects. By neglecting VA, perceptual quality models inherently assume that all objects draw the attention of the viewer to the same degree.

  • 292. Engelke, Ulrich
    et al.
    Kusuma, Tubagus Maulana
    Zepernick, Hans-Jürgen
    Perceptual Quality Assessment of Wireless Video Applications2006Konferensbidrag (Refereegranskat)
    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.

  • 293. Engelke, Ulrich
    et al.
    Kusuma, Tubagus Maulana
    Zepernick, Hans-Jürgen
    Caldera, Manora
    Reduced-reference metric design for objective perceptual quality assessment in wireless imaging2009Ingår i: Signal Processing-Image Communication, ISSN 0923-5965 , Vol. 24, nr 7, s. 525-547Artikel i tidskrift (Refereegranskat)
    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.

  • 294. Engelke, Ulrich
    et al.
    Liu, Hantao
    Zepernick, Hans-Jürgen
    Heynderickx, Ingrid
    Maeder, Anthony
    Comparing Two Eye-Tracking Databases: The Effect Of Experimental Setup And Image Presentation Time On The Creation Of Saliency Maps2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Visual attention models are typically designed based on human gaze patterns recorded through eye tracking. In this paper, two similar eye tracking experiments from independent laboratories are presented, in which humans observed natural images under task-free condition. The resulting saliency maps are analysedwith respect to two criteria; the consistency between the experiments and the impact of the image presentation time. It is shown, that the saliency maps between the experiments are strongly correlated independent of presentation time. It is further revealed that the presentation time can be reduced without substantially sacrificing the accuracy of the convergent saliency map. The results provide valuable insight into the similarity of saliency maps from independent laboratories and are highly beneficial for the creation of converging saliency maps at reduced experimental time and cost.

  • 295. Engelke, Ulrich
    et al.
    Maeder, Anthony
    Zepernick, Hans-Jürgen
    Analysing Inter-Observer Saliency Variations in Task-Free Viewing of Natural Images2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    We analyse variations of saliency between human observers when viewing natural image content. For this purpose, we conducted an eye tracking experiment to record gaze patterns of humans when viewing natural images. The resulting gaze patterns were used to create saliency maps for each observer and image. A correlation analysis is then conducted with the aim to quantify the variability of saliency between the observers and the different images. The results are considered to be a first step towards gaining a better understanding regarding the reliability of saliency maps for natural images.

  • 296. Engelke, Ulrich
    et al.
    Maeder, Anthony
    Zepernick, Hans-Jürgen
    Visual Attention Modelling for Subjective Image Quality Databases2009Konferensbidrag (Refereegranskat)
    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.

  • 297. Engelke, Ulrich
    et al.
    Rossholm, Andreas
    Zepernick, Hans-Jürgen
    Lövström, Benny
    Quality Assessment of an Adaptive Filter for Artifact Reduction in Mobile Video Sequences2007Konferensbidrag (Refereegranskat)
    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.

  • 298. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    A Framework for Optimal Region of Interest-based Quality Assessment in Wireless Imaging2010Ingår i: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 19, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Images usually exhibit regions that particularly attract the viewer's attention. These regions are typically referred to as regions-of-interest (ROI) and the underlying phenomenon in the human visual system is known as visual attention (VA). In the context of image quality one may expect that distortions occuring in the ROI are perceived as being more annoying, as compared to distortions in the background. However, VA is only seldom taken into account in existing image quality metrics. In this paper, we thus provide a VA framework to extend existing image quality metrics with a simple VA model. The performance of the framework is evaluated on three contemporary image quality metrics. We further consider the context of wireless imaging where a broad range of artifacts can be observed. To facilitate the VA based metric design, we conducted subjective experiments to both obtain a ground truth for the subjective quality of a set of test images and to identify ROI in the corresponding reference images. A methodology is further discussed to optimize the VA metrics with respect to quality prediction accuracy and generalization ability. It is shown that the quality prediction performance of the three considered metrics can be significantly improved by deploying the proposed framework.

  • 299. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    An Artificial Neural Network for Quality Assessment in Wireless Imaging Based on Extraction of Structural Information2007Konferensbidrag (Refereegranskat)
    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.

  • 300. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Framework for Optimal Region of Interest-based Quality Assessment in Wireless Imaging2010Ingår i: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 19, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Images usually exhibit regions that particularly attract the viewer's attention. These regions are typically referred to as regions-of-interest (ROI) and the underlying phenomenon in the human visual system is known as visual attention (VA). In the context of image quality one may expect that distortions occuring in the ROI are perceived as being more annoying, as compared to distortions in the background. However, VA is only seldom taken into account in existing image quality metrics. In this paper, we thus provide a VA framework to extend existing image quality metrics with a simple VA model. The performance of the framework is evaluated on three contemporary image quality metrics. We further consider the context of wireless imaging where a broad range of artifacts can be observed. To facilitate the VA based metric design, we conducted subjective experiments to both obtain a ground truth for the subjective quality of a set of test images and to identify ROI in the corresponding reference images. A methodology is further discussed to optimize the VA metrics with respect to quality prediction accuracy and generalization ability. It is shown that the quality prediction performance of the three considered metrics can be significantly improved by deploying the proposed framework.

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