Results 461-480 of 517.
Bookmark and Share    
Full Text
See detailDistribution Grid Monitoring through Pilot Injection and Successive Interference Cancellation
Neshvad, Surena UL; Chatzinotas, Symeon UL; Sachau, Jürgen UL

in Proceedings of IAEE Conference (2014)

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large ... [more ▼]

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large portion of the electricity demand is fed in through the distribution grid, whose good health and operational status will be important for guaranteeing grid stability. In Luxembourg, the distribution network is sparsely monitored and controlled, thus instabilities arising due to line overvoltage or DG malfunctioning are not rapidly detected and resolved. This research discusses a novel and low infrastructure methodology for online monitoring of the distribution grid. Such a tool will be increasingly necessary in order to guarantee the stability, reliability and security of the power network, as a larger and larger portion of the energy demand will be satisfied by DG in future years. In this research, advanced system identification techniques utilized in communications, such as Pseudo-Random Binary Sequences, Successive Interference Cancellation are applied to estimate the transfer function of power network propagation paths. The developed method proposes an online monitoring tool that computes grid parameters in real time during operation, without extensive infrastructure addition, by utilizing the PWM based inverters on the grid for active system identification. [less ▲]

Detailed reference viewed: 123 (10 UL)
Full Text
Peer Reviewed
See detailIndex assignment for multiple description repair in distributed storage systems
Kapetanovic, Dzevdan UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in ICC 2014 (2014)

Distributed storage systems have been receiving increasing attention lately due to the developments in cloud and grid computing. Furthermore, a major part of the stored information comprises of multimedia ... [more ▼]

Distributed storage systems have been receiving increasing attention lately due to the developments in cloud and grid computing. Furthermore, a major part of the stored information comprises of multimedia, whose content can be communicated even with a lossy (non-perfect) reconstruction. In this context, Multiple Description Lattice Quantizers (MDLQ) can be employed to encode such sources for distributed storage and store them across distributed nodes. Their inherent properties yield that having access to all nodes gives perfect reconstruction of the source, while the reconstruction quality decreases gracefully with fewer available nodes. If a set of nodes fails, lossy repair techniques could be applied to reconstruct the failed nodes from the available ones. This problem has mostly been studied with the lossless (perfect) reconstruction assumption. In this work, a general model, Multiple Description Lattice Quantizer with Repairs (MDLQR), is introduced that encompasses the lossy repair problem for distributed storage applications. New performance measures and repair techniques are introduced for MDLQR, and a non-trivial identity is derived, which is related to other results in the literature. This enables us to find the optimal encoder for a certain repair technique used in the MDLQR. Furthermore, simulation results are used to evaluate the performance of the different repair techniques. © 2014 IEEE. [less ▲]

Detailed reference viewed: 146 (0 UL)
Full Text
Peer Reviewed
See detailCompressive Sparsity Order Estimation for Wideband Cognitive Radio Receiver
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Signal Processing (2014)

Compressive Sensing (CS) has been widely investigated in the Cognitive Radio (CR) literature in order to reduce the hardware cost of sensing wideband signals assuming prior knowledge of the sparsity ... [more ▼]

Compressive Sensing (CS) has been widely investigated in the Cognitive Radio (CR) literature in order to reduce the hardware cost of sensing wideband signals assuming prior knowledge of the sparsity pattern. However, the sparsity order of the channel occupancy is time-varying and the sampling rate of the CS receiver needs to be adjusted based on its value in order to fully exploit the potential of CS-based techniques. In this context, investigating blind Sparsity Order Estimation (SOE) techniques is an open research issue. To address this, we study an eigenvalue-based compressive SOE technique using asymptotic Random Matrix Theory. We carry out detailed theoretical analysis for the signal plus noise case to derive the asymptotic eigenvalue probability distribution function (aepdf) of the measured signal’s covariance matrix for sparse signals. Subsequently, based on the derived aepdf expressions, we propose a technique to estimate the sparsity order of the wideband spectrum with compressive measurements using the maximum eigenvalue of the measured signal’s covariance matrix. The performance of the proposed technique is evaluated in terms of normalized SOE Error (SOEE). It is shown that the sparsity order of the wideband spectrum can be reliably estimated using the proposed technique for a variety of scenarios. [less ▲]

Detailed reference viewed: 271 (34 UL)
Full Text
Peer Reviewed
See detailPerformance of the Multibeam Satellite Return Link With Correlated Rain Attenuation
Arnau, J.; Christopoulos, Dimitrios UL; Chatzinotas, Symeon UL et al

in Wireless Communications, IEEE Transactions on (2014), 13(11), 6286-6299

Rain attenuation is among the major impairments for satellite systems operating in the K-band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the ... [more ▼]

Rain attenuation is among the major impairments for satellite systems operating in the K-band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link and obtain analytical approximations at high and low signal-to-noise ratio. The derived approximations provide insights into the effect of key system parameters such as the interuser distance, the satellite beam radius, or the rain intensity, and simulation results show that it fits tightly with the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights. [less ▲]

Detailed reference viewed: 162 (17 UL)
Full Text
Peer Reviewed
See detailSNR Estimation for Multi-dimensional Cognitive Receiver under Correlated Channel/Noise
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Wireless Communications (2013), 12(12), 6392-6405

In addition to Spectrum Sensing (SS) capability required by a Cognitive Radio (CR), Signal to Noise Ratio (SNR) estimation of the primary signals at the CR receiver is crucial in order to adapt its ... [more ▼]

In addition to Spectrum Sensing (SS) capability required by a Cognitive Radio (CR), Signal to Noise Ratio (SNR) estimation of the primary signals at the CR receiver is crucial in order to adapt its coverage area dynamically using underlay techniques. In practical scenarios, channel and noise may be correlated due to various reasons and SNR estimation techniques with the assumption of white noise and uncorrelated channel may not be suitable for estimating the primary SNR. In this paper, firstly, we study the performance of different eigenvaluebased SS techniques in the presence of channel or/and noise correlation. Secondly, we carry out detailed theoretical analysis of the signal plus noise hypothesis to derive the asymptotic eigenvalue probability distribution function (a.e.p.d.f.) of the received signal’s covariance matrix under the following two cases: (i) correlated channel and white noise, and (ii) correlated channel and correlated noise, which is the main contribution of this paper. Finally, an SNR estimation technique based on the derived a.e.p.d.f is proposed in the presence of channel/noise correlation and its performance is evaluated in terms of normalized Mean Square Error (MSE). It is shown that the PU SNR can be reliably estimated when the CR sensing module is aware of the channel/noise correlation. [less ▲]

Detailed reference viewed: 306 (25 UL)
Full Text
Peer Reviewed
See detailInline Interference Mitigation Techniques for Spectral Coexistence of GEO and NGEO Satellites
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of 19th ka band and 31st AIAA ICSSC conference (2013, October)

The requirement of low latency for real time systems and high demand of broad- band data are leading to the rapid deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several ... [more ▼]

The requirement of low latency for real time systems and high demand of broad- band data are leading to the rapid deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several frequency bands. When the number of usable non-geostationary (NGEO) satellites i.e., LEO/MEO in space increases, the need for frequency coexistence between the NGEO satellite systems with the already existing geostationary (GEO) satellite networks increases rapidly. In this context, it is crucial to explore interference mitigation techniques between GEO and NGEO systems in order to allow their spectral coexistence. More specifically, in the coexistence scenario of GEO and NGEO satellite networks, in-line interfer- ence may be a serious problem and it arises whenever an NGEO satellite passes through a line of sight path between a GEO earth station and a GEO satellite. In this paper, we carry out interference analysis between GEO and NGEO systems considering the case of O3b satellite systems and propose an adaptive power control technique for both the uplink and the downlink coexistence scenarios in order to mitigate the in-line interference. Furthermore, we provide several cognitive solu- tions for mitigating the in-line interference. [less ▲]

Detailed reference viewed: 244 (28 UL)
Full Text
Peer Reviewed
See detailEigenvalue Based Sensing and SNR Estimation for Cognitive Radio in Presence of Noise Correlation
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Vehicular Technology (2013), 62(8), 3671-3684

Herein, we present a detailed analysis of an eigenvalue based sensing technique in the presence of correlated noise in the context of a Cognitive Radio (CR). We use a Standard Condition Number (SCN) based ... [more ▼]

Herein, we present a detailed analysis of an eigenvalue based sensing technique in the presence of correlated noise in the context of a Cognitive Radio (CR). We use a Standard Condition Number (SCN) based decision statistic based on asymptotic Random Matrix Theory (RMT) for decision process. Firstly, the effect of noise correlation on eigenvalue based Spectrum Sensing (SS) is studied analytically under both the noise only and the signal plus noise hypotheses. Secondly, new bounds for the SCN are proposed for achieving improved sensing in correlated noise scenarios. Thirdly, the performance of Fractional Sampling (FS) based SS is studied and a method for determining the operating point for the FS rate in terms of sensing performance and complexity is suggested. Finally, a Signal to Noise Ratio (SNR) estimation technique based on the maximum eigenvalue of the received signal’s covariance matrix is proposed. It is shown that proposed SCN-based threshold improves sensing performance in correlated noise scenarios and SNRs up to 0 dB can be reliably estimated with less than 1 % normalized Mean Square Error (MSE) in the presence of correlated noise without the knowledge of noise variance. [less ▲]

Detailed reference viewed: 300 (45 UL)
Full Text
Peer Reviewed
See detailSecondary User Scheduling Under Throughput Guarantees for the Primary Network
Kapetanovic, Dzevdan UL; Butt, Majid; Chatzinotas, Symeon UL et al

in IEEE Vehicular Technology Conference (VTC), Fall 2013 (2013, September 02)

This work addresses scheduling in a cognitive radio scenario where a minimum throughput for the downlink primary network (PN) is guaranteed to each user with an associated violation probability ... [more ▼]

This work addresses scheduling in a cognitive radio scenario where a minimum throughput for the downlink primary network (PN) is guaranteed to each user with an associated violation probability (probability of not obtaining the guaranteed throughput). The primary network is surrounded by multiple downlink secondary networks, each aiming to maximize its network throughput. Scheduling in PN is performed independent of the secondary networks. Some information about the PN is available at the central scheduler that is responsible for scheduling the secondary networks. The contribution of this work is to apply a novel scheduler to the PN which is more robust to QoS degradations resulting from the secondary networks than other state of the art schedulers. This is validated by numerical simulations of the cognitive radio network. [less ▲]

Detailed reference viewed: 156 (1 UL)
Full Text
Peer Reviewed
See detailFrequency Packing for Interference Alignment-based Cognitive Dual Satellite Systems
Chatzinotas, Symeon UL; Sharma, Shree Krishna UL; Ottersten, Björn UL

in Proceedings of IEEE 78th Vehicular Technology Conference: VTC2013-Fall (2013, September)

Interference Alignment (IA) has been considered a promising technique for spectral coexistence of different wireless systems in an underlay cognitive mode. Furthermore, Frequency Packing (FP) can be ... [more ▼]

Interference Alignment (IA) has been considered a promising technique for spectral coexistence of different wireless systems in an underlay cognitive mode. Furthermore, Frequency Packing (FP) can be considered as an important technique for enhancing the spectrum efficiency in spectrum-limited satellite applications. In this paper, we consider a spectral coexistence scenario of a multibeam satellite and a monobeam satellite with the monobeam satellite as primary and the multibeam satellite as secondary. In this context, this paper focuses on examining the effect of FP on the performance of multi-carrier based IA technique. For this purpose, different IA techniques such as coordinated IA, uncoordinated IA and static IA have been considered. The effect of FP on the performance of different IA techniques in the considered scenario is evaluated in terms of system sum rate and primary rate protection ratio. It is shown that the system sum rate increases with the FP factor for all the techniques and the primary rate is perfectly protected with the coordinated IA technique even with dense FP. [less ▲]

Detailed reference viewed: 202 (15 UL)
Full Text
Peer Reviewed
See detailCognitive Radio Techniques for Satellite Communication Systems
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of IEEE 78th Vehicular Technology Conference: VTC2013-Fall (2013, September)

The usable satellite spectrum is becoming scarce due to continuously increasing demand for broadcast, multimedia and interactive services. In this context, cognitive satellite communications has received ... [more ▼]

The usable satellite spectrum is becoming scarce due to continuously increasing demand for broadcast, multimedia and interactive services. In this context, cognitive satellite communications has received important attention lately in the research community. Exploring efficient spectrum sharing techniques for enhancing spectral efficiency in satellite communication has become an important research challenge. In this paper, we study the main aspects of satellite cognitive communications and present possible practical scenarios for hybrid/dual cognitive satellite systems. Furthermore, suitable cognitive techniques for the considered scenarios are identified. More specifically, Spectrum Sensing (SS), interference modeling, and beamforming techniques are discussed for hybrid cognitive scenario and SS, interference alignment, and cognitive beamhopping techniques are discussed for dual satellite systems. This paper concludes by providing interesting open research issues in this domain. [less ▲]

Detailed reference viewed: 377 (17 UL)
Full Text
Peer Reviewed
See detailMMSE Filtering for Amplify & Forward SIMO Multiple Access Channel with Ill-conditioned Second Hop
Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proc of Asia-Pacific Conference on Communications, APCC 2013 (2013, August)

Detailed reference viewed: 98 (1 UL)
Full Text
Peer Reviewed
See detailTransmit Beamforming for Spectral Coexistence of Satellite and Terrestrial Networks
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of 8th International Conference on Cognitive Radio Oriented Wireless Networks 2013 (2013, July)

Herein, we study transmit beamforming techniques in an underlay cognitive mode for the coexistence of satellite and terrestrial networks with the satellite forward link as primary and the terrestrial ... [more ▼]

Herein, we study transmit beamforming techniques in an underlay cognitive mode for the coexistence of satellite and terrestrial networks with the satellite forward link as primary and the terrestrial downlink as secondary. Since geostationary satellite terminals have predetermined propagation characteristics so that they always point towards the geostationary satellite, the interference received by the satellite terminals from the terrestrial Base Station (BS) is confined in an angular sector. Based on this a priori knowledge, we propose transmit beamforming techniques at the BS to maximize the Signal to Interference plus Noise Ratio (SINR) towards the desired secondary user and to mitigate the interference towards the primary satellite terminals. Different types of Linearly Constrained Minimum Variance (LCMV) techniques have been proposed for our considered scenario where the exact locations and the number of satellite terminals within a specific angular sector are not known while designing the beamformer. Furthermore, an optimization problem is formulated for maximizing the Secondary User (SU) rate and it is shown that the worst case SU rate depends on the Primary User (PU) distance, PU interference threshold and the angular separation of the desired SU from the region of interest. [less ▲]

Detailed reference viewed: 237 (10 UL)
Full Text
Peer Reviewed
See detailCognitive Beamhopping for Spectral Coexistence of Multibeam Satellites
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Future Network and MobileSummit 2013 (2013, July)

The usable satellite spectrum is becoming scarce due to continuously increasing demand for broadcast and multimedia services. In this context, we consider the problem of enhancing spectral efficiency in ... [more ▼]

The usable satellite spectrum is becoming scarce due to continuously increasing demand for broadcast and multimedia services. In this context, we consider the problem of enhancing spectral efficiency in multibeam satellite networks. The spectral coexistence scenario of two multibeam satellites over a common coverage area is studied with a primary satellite having larger beams and a secondary satellite having smaller beams. Furthermore, a novel cognitive beamhopping satellite system is proposed. The system performance of the proposed system is evaluated and compared with that of conventional multibeam and beamhopping systems in terms of system throughput. It is shown that the proposed system significantly enhances the spectral efficiency in comparison to other systems. Moreover, the scenario of the presence of multiple secondary users within an inactive primary beam is considered with power control on the secondary transmission. The system performance is evaluated by considering partial and full frequency sharing approaches. It is noted that the total spectral efficiency increases with the number of secondary users in the full frequency reuse approach. [less ▲]

Detailed reference viewed: 238 (23 UL)
Full Text
Peer Reviewed
See detailThe Effect of Noise Correlation on Fractional Sampling based Spectrum Sensing
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Communications (ICC), 2013 IEEE International Conference on (2013, June)

This paper considers a Fractional Sampling (FS) technique to enhance the Spectrum Sensing (SS) efficiency of a Cognitive Radio (CR) using a decision statistic based on asymptotic Random Matrix Theory (RMT ... [more ▼]

This paper considers a Fractional Sampling (FS) technique to enhance the Spectrum Sensing (SS) efficiency of a Cognitive Radio (CR) using a decision statistic based on asymptotic Random Matrix Theory (RMT). Firstly, the effect of noise correlation on eigenvalue based SS is studied analytically and by numerical evaluation. Secondly, new bounds for the Standard Condition Number (SCN) are proposed to enhance the SS efficiency in correlated noise scenarios. It is shown that proposed FS method can enhance SS efficiency up to certain FS rates at the expense of receiver complexity and no performance advantage is obtained if the FS rate is increased beyond this limit. As a result, a method for determining the operating point for the FS rate in terms of sensing performance and complexity is suggested. [less ▲]

Detailed reference viewed: 213 (35 UL)
Full Text
Peer Reviewed
See detailSpatial Filtering for Underlay Cognitive SatComs
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in proceedings of 5th International Conference on Personal Satellite Services (2013, June)

Herein, we study an underlay beamforming technique for the coexistence scenario of satellite and terrestrial networks with the satel- lite return link as primary and the terrestrial uplink as secondary ... [more ▼]

Herein, we study an underlay beamforming technique for the coexistence scenario of satellite and terrestrial networks with the satel- lite return link as primary and the terrestrial uplink as secondary. Since satellite terminals are unique in that they always point towards the geo- stationary satellite, interference received by the terrestrial Base Station (BS) is concentrated in a specific angular sector. The priori knowledge that all the geostationary satellite terminals are facing south for the European coverage can be used in designing a beamformer at the ter- restrial BS. Based on this concept, we propose a receive beamformer at the BS to maximize the Signal to Interference plus Noise Ratio (SINR) towards the desired user and to mitigate the interference coming from the interfering satellite terminals. The performances of Minimum Vari- ance Distortionless (MVDR) and Linear Constrained Minimum Variance (LCMV) beamformers are compared for our considered scenario. It is shown that LCMV beamformer is better suited in rejecting interference even in case of Direction of Arrival (DoA) uncertainty of interfering satel- lite terminals as long as DoA range of the interfering sector is known to the beamformer. Furthermore, it is noted that MVDR beamformer is suitable for a large number of interferers. [less ▲]

Detailed reference viewed: 186 (22 UL)
Full Text
Peer Reviewed
See detailAsymptotic Analysis of Eigenvalue-based Blind Spectrum Sensing Techniques
Chatzinotas, Symeon UL; Sharma, Shree Krishna UL; Ottersten, Björn UL

in proceedings of International Conference on Acoustics, Speech, and Signal Processing (ICASSP) 2013 (2013, May)

Detailed reference viewed: 238 (20 UL)
Full Text
Peer Reviewed
See detailMMSE Filtering Performance of Dual-Hop Amplify-and-Forward Multiple-Access Channels
Chatzinotas, Symeon UL

in Wireless Communications Letters, IEEE (2013), 2(1), 122-125

Detailed reference viewed: 120 (8 UL)
Full Text
Peer Reviewed
See detailRepairing multiple description quantizers in distributed storage systems
Chatzinotas, Symeon UL

Scientific Conference (2013)

Distributed storage systems have been receiving increasing attention lately due to the developments in cloud and grid computing. Furthermore, a major part of the stored information comprises of multimedia ... [more ▼]

Distributed storage systems have been receiving increasing attention lately due to the developments in cloud and grid computing. Furthermore, a major part of the stored information comprises of multimedia, whose content can be communicated even with a lossy reconstruction. In this context, Multiple Description Quantizers (MDQ) can be employed to encode such sources for distributed storage. However, a question which naturally arises is how to repair lost descriptions which are due to node failures. In this paper, we employ MDQs based on translated lattices and a common decoding method through averaging over the available descriptions. The descriptions of failed nodes are repaired by quantizing the estimate of common decoding and then by reusing the same side codebook. Based on simulations, we study the effect of system size and number of failures on the distortion of the reconstructed source. As expected, the distortion deteriorates with the number of failures but the degradation is graceful especially for large systems. © 2013 IEEE. [less ▲]

Detailed reference viewed: 179 (2 UL)
Full Text
Peer Reviewed
See detailInterference alignment for spectral coexistence of heterogeneous networks
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in EURASIP Journal on Wireless Communications and Networking (2013), 2013(46),

The coexistence of heterogeneous networks within the same spectrum for enhancing the spectrum efficiency has attracted large interest lately in the research community. Furthermore, the research interest ... [more ▼]

The coexistence of heterogeneous networks within the same spectrum for enhancing the spectrum efficiency has attracted large interest lately in the research community. Furthermore, the research interest towards the deployment of small cells and multibeam satellites is increasing due to high capacity, easier deployment and higher energy efficiency. However, due to the scarcity of available spectrum and the requirement of additional spectrum for these systems, small cells need to coexist with macrocells and multibeam satellites need to coexist with monobeam satellites within the same spectrum. In this context, this contribution investigates an underlay spectral coexistence mechanism which exploits an interference alignment (IA) technique in order to mitigate the interference of cognitive transmitters towards the primary receivers in a normal uplink mode. More specifically, three types of IA techniques, namely static, uncoordinated and coordinated are investigated. The performance of the IA technique is evaluated and compared with primary only, resource division and no-mitigation techniques in terms of sum-rate capacity, primary to secondary rate ratio and primary rate protection ratio. It is shown that the coordinated IA technique perfectly protects the primary rate in both terrestrial and satellite coexistence scenarios. [less ▲]

Detailed reference viewed: 263 (32 UL)
Full Text
Peer Reviewed
See detailMultiantenna Signal Processing for Cognitive Communications
Chatzinotas, Symeon UL; Sharma, Shree Krishna UL; Ottersten, Björn UL

in Proceedings of IEEE China Summit and International Conference on Signal and Information Processing (ChinaSIP) 2013 (2013)

Cognitive communications has attracted a large interest during the last decade due to spectrum scarcity. In combination with multiantenna techniques, cognitive communications have the ability to increase ... [more ▼]

Cognitive communications has attracted a large interest during the last decade due to spectrum scarcity. In combination with multiantenna techniques, cognitive communications have the ability to increase spectral efficiency by enabling the coexistence of a primary and secondary systems. In this paper, we focus in two specific cognitive approaches: a) Multiantenna Interference Alignment (IA) and b) Multiantenna Spectrum Sensing (SS). In the first case, we investigate how IA over multiple spatial dimensions can be exploited in order to lower harmful interference towards the primary system into acceptable levels. In the second case, we compare the sensing performance of different eigenvalue-based blind SS techniques. This paper concludes by presenting some interesting open problems in this area. [less ▲]

Detailed reference viewed: 228 (7 UL)