K. Ivanov

Nokia Siemens Networks, Esbo, Southern Finland Province, Finland

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Publications (28)1.48 Total impact

  • 10/2010: pages 151-210;
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    ABSTRACT: Uplink power control in UTRAN Long Term Evolution consists of an open-loop scheme handled by the User Equipment and closed-loop power corrections determined and signaled by the network. In this study the difference in performance between pure open-loop and combined open and closed-loop power control has been analyzed and the different behavior of fractional vs. full path-loss compensation has been evaluated. A comprehensive system level simulation model has been used with a facility to trace a particular test user during its motion from eNodeB towards the cell border and back to its initial position. This study demonstrates the effect of distance path-loss of a test user on several physical layer performance metrics including throughput, resource allocation as well as modulation and coding scheme utilization. Simulation results in a fully loaded network show high throughput for open-loop fractional power control for the user located in the vicinity of the serving eNodeB, however, steep performance degradation has been observed when the user is moving towards the cell edge. The user throughput at the cell border can be increased by the closed-loop component. The benefit of closed-loop power control is the higher homogeneity in terms of throughput across the entire network area and the ability to automatically stabilize the network performance under different conditions like cell load and traffic distribution.
    Communications, 2009. ICC '09. IEEE International Conference on; 07/2009
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    ABSTRACT: Uplink power control in 3GPP UTRAN Long Term Evolution networks supports an optional closed-loop component around an open-loop point of operation. In this study the performance difference between pure open-loop and combined open- and closed-loop power control has been evaluated using a full blown system level simulation model. The interworking between power control, adaptive transmission bandwidth, and adaptive modulation and coding has been thoroughly analyzed and the resulting performance differences depending on the users' locations within the cells are demonstrated by two-dimensional network plots. A deep inhomogeneous throughput distribution throughout the deployment area has been observed for pure open-loop power control. Enabling the closed-loop component results in a more homogeneous performance albeit at lower mean throughput. Significant impact is given by the selected quality and level targets for the closed-loop component. The benefit of closed-loop power control is the higher homogeneity in terms of throughput across the entire cell area and its ability to adjust the transmission power according to the desired quality and level targets. Hence the network performance is stabilized in various cell environments.
    Proceedings of the International Conference on Wireless Communications and Mobile Computing: Connecting the World Wirelessly, IWCMC 2009, Leipzig, Germany, June 21-24, 2009; 01/2009
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    ABSTRACT: Uplink power control in 3GPP UTRAN Long Term Evolution (LTE) networks consists of a closed-loop scheme around an open-loop point of operation. The uplink performance of the network is decisively influenced by power control. This paper provides insight into the power control procedure and its interworking with Adaptive Transmission Bandwidth (ATB) as well as Adaptive Modulation and Coding (AMC) presenting a detailed performance evaluation by system level simulations for a fully loaded network. The analysis starts for pure open-loop power control as reference, for which the impact of parameter settings on resource allocation, utilization of specific modulation and coding schemes, retransmission rate, and resulting throughput has been determined. A two-dimensional parameter optimization for full path-loss compensation and fractional power control has been performed to conclude the best strategy for the trade-off between network capacity and coverage. Finally on top of this optimized open-loop power control parameter set the closed-loop component has been enabled and proposals for optimum power control threshold settings are provided. The beneficial effects of closed-loop power control are presented highlighting its ability to adjust the transmission power according to the desired quality and level requirements.
    12/2008: pages 175-184;
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    ABSTRACT: In mobile networks a most economic utilization of the channels on the air interface by means of intelligent radio resource management is desired since these resources are the most valuable ones. Half-rate speech codecs introduced in GERAN networks for capacity increase involve quality degradation compared to full-rate codecs especially in error-prone radio channel conditions. To provide best possible speech quality the available resources in the network should be utilized as extensive as possible. In addition flexible mechanisms are required to provide additional capacity whenever needed for obtaining the optimum trade-off between quality expectations and capacity requirements. In this study two different load dependent half-rate allocation algorithms for speech services have been proposed. The performance differences have been evaluated thoroughly by system level simulations and compared in terms of system performance. Applied quality criteria are frame erasure rate, bad speech quality probability, codec mode distribution, speech quality indicator and call drop rate. The results show significant differences in channel utilization, speech quality and achieved network capacity.
    Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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    ABSTRACT: The introduction of the upcoming GERAN evolution feature package in current GSM/EDGE deployments offers operators significant boost in network capacity and mobile data users UMTS/HSPA like high speed packet data services along with competitive latency. Intelligent radio resource management supports novel dual-carrier capable mobile stations by dynamic configuration of GPRS/EDGE packet data channels (PDCHs) on multiple non-BCCH carriers. In addition the currently standardized EDGE2 level B (EDGE2-B) concept provides enhanced PDCH data rates up to 118.4 kbps per timeslot. In this paper system level simulation results for the end-to-end performance of GERAN over TCP/IP are presented assuming conventional 4 timeslots up to future potential 14 timeslots capable EDGE and EDGE2-B mobiles showing up to 800 / 1600 kbps peak data rates. FTP-application throughput has been investigated with respect to both download file size and important TCP settings such as e.g. receiver window size. The GERAN dual-carrier performance has been evaluated for EDGE and EDGE2-B both under ideal radio conditions and in regular hexagonal cellular deployments depending on system load, exemplifying FTP 500 kbyte download with 8 timeslots capable mobiles. At medium system load EDGE2-B compared to EDGE reveals about 100% capacity gain and more than 60% gain in mean user throughput.
    Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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    ABSTRACT: Different user segments have various requirements and expectations towards the performance of mobile networks. Subscribers having experienced the high quality of UMTS networks desire to maintain high speech quality and excellent data throughput also in areas of missing UMTS but existing GSM coverage. In GSM networks a privileged treatment of UMTS subscribers by means of proper resource allocation provides a substantial quality improvement with respect to standard GSM subscribers. This strategy allows network operators to reduce the performance gap between both network areas experienced by UMTS subscribers. A detailed study on the performance of circuit switched speech and packet data services has been performed based on system level simulations. The results show significant speech quality advantages for users with dual-RAT terminals compared to standard GSM users as well as notably higher data throughput rates.
    Wireless Personal Communications 06/2008; 46(1):5-18. · 0.43 Impact Factor
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    ABSTRACT: Dual antenna interference cancellation (DAIC) recently introduced by 3 GPP standardization as a natural evolution step of its predecessor single antenna interference cancellation (SAIC) to further improve the spectral efficiency in GERAN networks is based on the enhancement of the SAIC inherent downlink advanced receiver performance (DARP) feature by receive diversity. In this study focus has been set on a proper and efficient modelling of DAIC in terms of link-to-system level simulator interface (LSLI). A novel memory saving approach for the design of LSLI suggests a lower and upper bound for the dominant interference ratio (DIR) metric to be used in system level simulations. Using the new approach system level simulations have been performed showing roughly three to four-fold capacity gain w.r.t. today's conventional AMR networks and a gain of factor two compared to deployments with 100% SAIC penetration.
    Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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    ABSTRACT: As customer demand for wireless data services increases the bandwidth requirements for new applications are rapidly growing Half-rate speech codecs have been introduced in GERAN networks to save operator's spectrum shared by circuit switched voice and packet switched data services. The released physical resources by allocating voice calls on half-rate channels can be efficiently utilized to significantly increase the data rate of packet switched services. Since by nature the speech quality on half-rate channels is inferior to that on full-rate channels a dynamic half-rate assignment strategy has been introduced triggering half-rate allocation by taking into account both the radio conditions of the voice call and the cell traffic load. Provided that the radio conditions are sufficient voice calls are temporarily allocated on half-rate channels during periods of high traffic load to ensure high quality of service level for packet data applications. In this study the trade-off between speech quality and data capacity has been analyzed by means of system level simulations. Exploiting half-rate allocation at the expense of certain speech quality degradation results in a substantial reduction of the number of blocked data calls as well as in a significant increase in the packet data throughput. Yet almost the same performance for packet data services is achieved by pure and dynamic half-rate allocation, the latter strategy provides significant speech quality gain for 50% of the subscribers.
    Mobile and Wireless Communications Summit, 2007. 16th IST; 08/2007
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    ABSTRACT: Audio bandwidth extension in AMR-WB to twice of that used in AMR-NB provides essential subjective speech quality improvements, while the link level performance in GERAN networks for codec modes of comparable source bit rate is similar. This study analyzes the effect of improved audio perception as well as the impact of channel errors and call drops on the network performance. Profound system level simulations for relaxed 4times3 and 3times3 frequency re-use as well as tight 1times1 reuse have been performed In 4times3 and 3times3 re-use networks, whose capacity is limited by hard-blocking, the audio advantage provided by AMR-WB is entirely transformed into quality improvements. These amount almost one third on the speech quality indicator (SQI) scale ranging from zero to one. The capacity of 1times1 re-use networks is primarily limited through soft-blocking criteria. Four different quality criteria have been applied: SQI, frame erasure rate (FER), bad quality probability (BQP), and call drop rate (CDR). If only the subjective speech quality criteria were taken into account an increase in network capacity from 21% Erlang fractional load (EFL) for AMR-NB to 32% for AMR-WB is feasible. Since this quality indicator is rather related to general speech quality impression than to intelligibility, additional FER based quality criteria and CDR have been applied. Requiring additionally BQP lower than 5% and CDR lower than 2% limits the capacity of AMR-WB tight re-use networks to 21% EFL. Exactly the same capacity is achieved by AMR-NB, for which subjective speech quality is the more restrictive criterion. Exchanging the BQP criterion by the more restrictive criterion of mean FER per call lower than 2% for 95% of the subscribers leads to capacity advantages for AMR-NB due to lack of sufficiently robust AMR-WB codec modes and the higher latency in codec mode adaptation using tandem free operation. Results indicate that tight re-use networks should not exploit first glance quali- ty advantage of AMR-WB. Instead for the definition of admission control thresholds FER and BQP criteria shall be taken into consideration in addition to subjective speech quality impression.
    Mobile and Wireless Communications Summit, 2007. 16th IST; 08/2007
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    ABSTRACT: Smart quality enhancement (SQE) aims at improving traditional quality based power control algorithms by automatically adjusting the transmit power control decision thresholds to the prevailing traffic load conditions. During low traffic periods a high C/I threshold is required to protect calls against quality degradation caused by occasionally emerging interferers. At busy hour traffic level lower C/I decision thresholds are used to reduce the interference level for the most affected calls in the network. Applying this strategy the call is always best served. The benefit from SQE has been investigated by means of system level simulations. The simulation results show an optimum speech quality achieved by SQE over the whole range of feasible traffic load in the network. The percentage of satisfied users at low traffic load that would have been obtained with an optimum static decision threshold configured for busy hour traffic has been increased by SQE from about 93% to above 99%. Correspondingly the percentage of satisfied users at busy hour traffic load that would have been obtained with an optimum static decision threshold configured for low traffic has been improved from 90% up to 93%. Assuming an acceptable outage of 10% the quality improvement of about 3% can be traded-off against a capacity gain of about 10% to 15%. SQE is especially beneficial in network deployments providing mixed indoor and outdoor coverage
    Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on; 10/2006
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    ABSTRACT: WiMax broadband MAN based on the IEEE 802.16d/e standard supports mobile as well as fixed wireless access services. The underlying subscriber data links are characterised by totally different radio conditions such as propagation, interference rejection capability, terminal antenna gain, pattern and height. This leads to a significant coverage mismatch, different user throughput, system capacity and spectrum efficiency. In this paper, the basic performance of mobile and fixed subscribers has been thoroughly analysed for homogeneous hexagonal 3.5 GHz cellular deployments of an OFDM-based WiMax system depending on cell size, frequency reuse and offered traffic load. Network level simulation results on user FTP-application throughput, channel load, modulation and coding scheme utilisation and packet call blocking have been presented for cell radius of 300, 1000 and 2000 m in tight 1 × 1 and 1 × 3 frequency reuse, respectively. The future performance enhancements from optional features as Block Turbo Coding, downlink Power Control, scheduling schemes, sub-channelling in scalable OFDMA and advanced antenna technology have been evaluated and simulation results provided. Copyright © 2006 AEIT.
    European Transactions on Telecommunications 03/2006; 17(2):203 - 218. · 1.05 Impact Factor
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    ABSTRACT: During the last couple of years a series of voice quality and capacity enhancement features have been implemented in narrow-band deployments of GERAN (GSM/EDGE radio access networks) mobile radio networks. Recent field findings revealed call drop rate (CDR) to be the major limiting factor already in medium loaded AMR (adaptive multi rate) networks planned in tight frequency reuse due to excessive failures on the associated control channels (ACCH). The reason for this phenomenon observed at 20% to 30% EFL (Erlang fractional load) is the significant link level performance imbalance of up to 6 dB (in terms of C/I) between AMR 4.75/5.90 kbps voice codecs and signaling ACCH. In this study a novel strategy based on temporary ACCH overpower has been proposed as a practical and fully backwards compatible option to reduce the C/I gap and to improve the probability of successful decoding of the FACCH/SACCH frames. A full description of the CDR contributors (radio link timeout and handover failures) has been provided along with detailed system level simulation results. The initial evaluation of the novel approach is very promising, showing a significant soft capacity gain by substantially reducing CDR allowing a system load well above 30% EFL in homogeneous hexagonal networks. The suggested approach could be efficiently combined with current 3GPP standardization initiatives for control channel improvements in GERAN
    Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
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    ABSTRACT: The recent IEEE802.16d/e standardization initiative for wireless metropolitan area networking (MAN) aims at portable and mobile broadband wireless access (BWA) in cellular deployments as well as conventional fixed residential high throughput access (e.g. wireless DSL) and feeding applications such as IEEE802.11 WLAN hotspot backhaul. This paper focuses on the basic IEEE802.16d/e performance presenting end-to-end application throughput, capacity and spectrum efficiency figures for pure mobile scenarios. Detailed link level and system level simulations have been performed in interference limited cellular environment for tight 1x1 and 1x3 frequency reuse showing very promising results on 3.5 MHz OFDM channels (256 sub-carriers) in the 3.5 GHz band. The dependency of the application throughput, channel utilization and coding scheme distribution on the system load has been thoroughly analyzed. It is shown that admission control functionality is mandatory for a system in 1x1 reuse to avoid overload and packet call blocking conditions, whereas 1x3 reuse works properly over the entire system load range.
    Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st; 01/2005
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    ABSTRACT: Growing traffic load in today's wireless networks brings up new challenges with respect to capacity. Simultaneously the demands for high quality voice services are rising. AMR half-rate in 8-PSK modulation combines both aspects and provides doubling the GERAN capacity just at a slight degradation of the perceived speech quality. A detailed performance study of 8-PSK modulated AMR half-rate codec modes is presented based on network planning studies and profound system level simulations. In addition a performance comparison to GMSK modulated AMR half-rate and full-rate codec modes has been provided. This analysis is focused on speech quality, coverage and capacity by AMR-NB in GERAN networks applying different frequency re-use patterns ranging from relaxed 4times3 to tight 1times1. The trade-off between quality and capacity has been demonstrated as well as the gain provided by 8-PSK modulated AMR half-rate. Network configurations offering full-rate quality by the allocation of half-rate channels have been identified. The capacity gain can be used to serve additional subscribers and/or to increase the quality and capacity of GPRS/EDGE data services
    01/2005;
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    ABSTRACT: The introduction of AMR-WB in 2G and 3G mobile networks represents a quantum leap in speech quality. The perceived voice quality is even superior to that offered in today's wire-line networks. A detailed study on the performance of the different AMR-WB codec types supporting GMSK as well as 8-PSK modulation has been performed based on system level simulations. The investigation is focused on speech quality, coverage and capacity that can be achieved in GERAN networks applying different frequency re-use patterns starting from a relaxed 4×3 down to a tight 1×1. The results show that neither additional sites nor a re-planning of the network is necessary for the introduction of AMR-WB. The dynamics of real codec mode adaptation traced along with the experienced radio link quality on an individual link reveal that an excellent speech quality can be achieved. The support of AMR-WB by both GERAN and UMTS offers high network homogeneity and a perfect symbiosis between 2G and 3G technologies providing an outstanding voice quality throughout the complete area of the multi-RAT network.
    Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st; 01/2005
  • C.F. Ball, K. Ivanov, L. Bugl, P. Stockl
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    ABSTRACT: The end-to-end performance in both GPRS and EDGE is strongly related to the efficiency of the RLC/MAC protocol. In this paper, we focus on the optimization of several parameters like RLC polling period, RLC roundtrip time and RLC window size. Furthermore, we discuss specific implementation options as well as control mechanisms provided by the standard. The optimum settings of these parameters and their mutual interaction evaluated by simulations have been confirmed by PING and application throughput measurements in a real system. In addition, different architectural aspects such as PCU embedded either in the BSC or in the BTS and 64 kbps vs. 16 kbps based Abis interface have been discussed. The new concept of "RLC frequent retransmission prevention" on the sender side allows fast polling by simultaneously avoiding retransmission of RLC blocks with pending acknowledgement status. The novel fast polling strategy provides about 3 dB to 4 dB link level gain as well as user throughput enhancement in the order of 20% for GPRS and 30% for EDGE.
    Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
  • C.F. Ball, K. Ivanov, L. Bugl, P. Stockl
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    ABSTRACT: A detailed analysis of the GPRS and EGPRS RLC/MAC protocol and its influence on the overall end-to-end performance has been performed. The end user application throughput depends on several parameters, such as the RLC polling period, the RLC window size, the RLC roundtrip time, and specific protocol implementation issues. Simulation and measurement results for optimum adjustment of the above parameters are given; they also demonstrate the superiority of the improved EGPRS protocol stack versus the original GPRS one. Additionally, a protocol performance improvement both for GPRS and EGPRS has been proposed by introducing a new concept of "RLC frequent retransmission prevention" on the sender side, allowing fast polling by simultaneously avoiding retransmission of RLC blocks with pending acknowledgement status. Fast polling is referred to as the introduction of a very short RLC polling period, with, e.g., 8 RLC blocks, versus moderate polling periods, e.g., of 16 or 24 RLC blocks. The proposed strategy for fast polling proves to provide a user throughput gain in the order of 20% for GPRS and 30% for EDGE.
    Personal, Indoor and Mobile Radio Communications, 2004. PIMRC 2004. 15th IEEE International Symposium on; 10/2004
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    ABSTRACT: Customer demand for wireless data services is rapidly increasing. The introduction of GPRS, EDGE and UMTS providing high bit rate radio bearer, however, is not the complete response for satisfying the demands of these new high quality services. An advanced quality of service QoS management is necessary to handle the characteristic requirements of both different service types and user expectations. A new QoS strategy is proposed and analyzed comprising 3GPP QoS parameters along with operator's specific weighting factors to define the appropriate QoS priority of each service type and user profile. Admission control as well as a deterministic up-and downgrading strategy are applied to ensure a minimum grade of service for low-priority applications. Furthermore, delay time sensitive services and premium users are granted a full bandwidth. Simulation results are provided to qualify the behavior of the proposed QoS strategy under different packet data load conditions. Especially in highly loaded and even overloaded GERAN networks the introduction of QoS provides significant benefits for the end user and offers powerful means to increase the service revenues according to the charging policy adopted by the network operator. The introduction of an appropriate QoS strategy is the prerequisite for an overlay deployment strategy of GSM/EDGE and UMTS.
    Personal, Indoor and Mobile Radio Communications, 2004. PIMRC 2004. 15th IEEE International Symposium on; 10/2004
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    ABSTRACT: With SI<sup>2</sup>R-DMA a novel procedure for boosting GERAN capacity in synchronized narrowband deployments has been proposed. The main goal of SI<sup>2</sup>R-DMA is both the inter- and intra-site interference reduction by intelligent radio resource management evolved from state-of-the-art DMA. For this purpose the new concept of concentric MAIO has been introduced for partitioning cells in inner and outer areas, whereas inner and outer mobiles of different interfering sites are allocated on orthogonal timeslots thus minimizing the mutual inter-site interference caused by random frequency hopping. The interaction between different sites in finding the optimum resource allocation with minimum inter-site interference has been modeled similar to a self-organizing neural network. A detailed description of SI<sup>2</sup>R-DMA has been provided accompanied by a variety of simulation results. First results are very promising, showing significant capacity gain of about 20% compared to conventional DMA.
    Personal, Indoor and Mobile Radio Communications, 2004. PIMRC 2004. 15th IEEE International Symposium on; 10/2004