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Turkka J.,Tampere University of Technology | Nihtila T.,Magister Solutions Ltd. | Viering I.,Nomor Research GmbH
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2011

This paper presents a performance evaluation of an uplink load balancing algorithm for Long-Term Evolution (LTE) Self-Organizing Networks (SON) in a non-regular network layout and shows how cell sizes affect the performance of the algorithm. The proposed algorithm solves local overload situations by handing over users to neighboring cells and adjusting power control settings. However, the non-regular network layout and the varying cell size can limit the expected gains of the algorithm in some situations due to the chosen uplink load balancing strategies and the limitations of the LTE uplink radio access technique. The performance evaluation is done by using a fully dynamic LTE system simulator which is capable to model user and network characteristics, mobility and radio resource management (RRM) algorithms accurately. © 2011 IEEE.


Chang Z.,University of Jyvakyla | Chang Z.,Magister Solutions Ltd. | Ristaniemi T.,University of Jyvakyla | Niu Z.,Tsinghua National Laboratory for Information Sciences and Technology
IEEE Transactions on Wireless Communications | Year: 2014

This paper addresses the resource allocation problem in collaborative relay-assisted OFDMA networks. Recent works on the subject usually ignored either the selection of relays, asymmetry of the source-to-relay and relay-to-destination links or the imperfections of channel state information. In this article we take into account all these together and our focus is two-fold. Firstly, we consider the problem of asymmetric radio resource allocation, where the objective is to maximize the system throughput of the source-to-destination link under various constraints. In particular, we consider optimization of the set of collaborative relays and link asymmetries together with subcarrier and power allocation. Using a dual approach, we solve each sub-problem in an asymptotically optimal and alternating manner. Secondly, we pay attention to the effects of imperfections in the channel-state information needed in resource allocation decisions. We derive theoretical expressions for the solutions and illustrate them through simulations. The results validate clearly the additional performance gains through an asymmetric cooperative scheme compared to the other recently proposed resource allocation schemes. © 2014 IEEE.


Asghar M.Z.,Magister Solutions Ltd. | Hamalainen S.,Nokia Inc. | Ristaniemi T.,University of Jyväskylä
2012 IEEE 17th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks, CAMAD 2012 | Year: 2012

Fault management is an important part of the operations and maintenance subsystem (OSS) of cellular mobile networks. Perhaps the most important reason is to reduce the number of outages and duration of outages in the network in order to meet the operator's requirements such as network availability, robustness, coverage and capacity etc. Increasing complexity of the cellular networks has significant impact on the operations and maintenance of the network. Automation is necessary to protect the operational as well as capital expenses of the cellular network. The aim of this paper is to present a self-healing framework developed for 3GPP Long Term Evolution (LTE) networks and to provide a platform where the detection and compensation of cell outages are evaluated in realistic environment. The impact of early fault detection and timely execution of compensation tasks are shown in terms of radio link failures and number of connected users. © 2012 IEEE.


Chang Z.,University of Jyväskylä | Chang Z.,Magister Solutions Ltd | Ristaniemi T.,University of Jyväskylä
Wireless Networks | Year: 2013

This work addresses the radio resource allocation problem for cooperative relay assisted OFDMA wireless network. The relays adopt the decode-and-forward protocol and can cooperatively assist the transmission from source to destination. Recent works on the subject have mainly considered symmetric source-to-relay and relay-to-destination resource allocations, which limits the achievable gains through relaying. In this paper we consider the problem of asymmetric radio resource allocation, where the objective is to maximize the system throughput of the source-to-destination link under various constraints. In particular, we consider optimization of the set of cooperative relays and link asymmetries together with subcarrier and power allocation. We derive theoretical expressions for the solutions and illustrate them through simulations. The results show clear additional performance gains through asymmetric cooperative scheme compared to the other recently proposed resource allocation schemes. © 2012 Springer Science+Business Media, LLC.


Ong E.H.,Nokia Inc. | Kneckt J.,Nokia Inc. | Alanen O.,Magister Solutions Ltd. | Chang Z.,Magister Solutions Ltd. | And 2 more authors.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2011

The IEEE 802.11ac is an emerging very high throughput (VHT) WLAN standard that could achieve PHY data rates of close to 7 Gbps for the 5 GHz band. In this paper, we introduce the key mandatory and optional PHY features, as well as the MAC enhancements of 802.11ac over the existing 802.11n standard in the evolution towards higher data rates. Through numerical analysis and simulations, we compare the MAC performance between 802.11ac and 802.11n over three different frame aggregation mechanisms, viz., aggregate MAC service data unit (A-MSDU), aggregate MAC protocol data unit (A-MPDU), and hybrid A-MSDU/A-MPDU aggregation. Our results indicate that 802.11ac with a configuration of 80MHz and single (two) spatial stream(s) outperforms 802.11n with a configuration of 40 MHz and two spatial streams in terms of maximum throughput by 28% (84%). In addition, we demonstrate that hybrid A-MSDU/A-MPDU aggregation yields the best performance for both 802.11n and 802.11ac devices, and its improvement is a function of the maximum A-MSDU size. © 2011 IEEE.


Puttonen J.,Magister Solutions Ltd. | Kurjenniemi J.,Magister Solutions Ltd. | Alanen O.,Magister Solutions Ltd.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2010

In this paper we propose a radio problem detection based rescue handover for 3G Long Term Evolution (LTE). The radio problem detection based handover algorithm takes advantage of already existing Radio Link Failure (RLF) detection mechanism specified in 3GPP for LTE. In coverage limited scenarios as well as challenging interference and mobility conditions, the event triggered handover measurement report may not be even sent to Evolved NodeB at the time of RLF. In proposed algorithm UE shall monitor the downlink quality based on the cell-specific reference signal in order to detect the downlink radio link quality of the serving cell. In case of a detected radio link problem handover process is initiated to a better cell. The proposed handover algorithm is compared to the default UE assisted hard handover process by means of fully dynamic system level simulations. Based on the studies it can be concluded that the radio problem detection assisted handover algorithm decreases the amount of RLFs thereby improving the handover and system performance. Especially the RLFs that occur before the handover process is even started are basically non-existent. ©2010 IEEE.


Puttonen J.,Magister Solutions Ltd. | Virtej E.,Nokia Inc. | Keskitalo I.,Nokia Inc. | Malkamaki E.,Nokia Inc.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2012

In cellular networks it is envisioned an explosion of diverse data applications running in smart phones, which could increase significantly not only user plane but also control plane load in the network. Smart phones and their always-on applications introduce several challenges: From the network perspective, an increased amount of UEs/applications can increase the signaling load due to frequent state transitions and handover signaling. From the UE perspective, challenges of power consumption are evident, since UE would increasingly be in connected state. In this article we study the trade-off between releasing the UE into idle state vs. keeping the UE in connected state, in a LTE system. The results indicate that optimum performance can be achieved using UE specific RRC release timer and DRX configurations by taking advantage of traffic characteristics and UE mobility. © 2012 IEEE.


Chernogorov F.,Magister Solutions Ltd. | Puttonen J.,Magister Solutions Ltd.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

In wireless mobile networks quality of user experience changes dynamically and depends on large variety of factors. Because of that mobile operators are willing to timely and effectively evaluate provided Quality of Service (QoS) in their networks. Nowadays the main tool for monitoring network state and performance is drive testing. To replace this expensive and mostly manual procedure, concept of Minimization of Drive Tests (MDT) is being developed in 3GPP LTE standardization. One area where MDT is applied is QoS verification, where user satisfaction is evaluated on the basis of periodic reports which contain values of different Key Performance Indicators (KPIs). By analyzing these KPIs one could find users which are unsatisfied with the experienced QoS and optimize configuration parameters in the areas of the network where concentration of unsatisfied users is high. In this paper we introduce a data mining framework which allows to distinguish between satisfied and unsatisfied users in LTE mobile network on the basis of limited number of KPIs. In addition, we take into use a KPI ranking system which gives an ability to significantly reduce the number of analyzed variables without compromising the resulting accuracy. © 2013 IEEE.


Erkkila A.-L.,Metso Paper Inc. | Leppanen T.,Magister Solutions Ltd. | Leppanen T.,Jyväskylä University of Applied Sciences | Hamalainen J.,Lappeenranta University of Technology
International Journal of Solids and Structures | Year: 2013

The rheological nature of paper or board is usually treated either as elasto-plastic or as viscoelastic depending on the studied paper making process or behavior in converting and end use. In this paper we study several stress-strain curve models and the determination of material parameters from an elasto-plastic point of view. Finally, a suitable approach for all stress-strain curves measured from 180 strips is constructed using a linear function for an elastic region and a nonlinear function for a strain hardening region. This model determines a proportional limit (elastic limit) and gives fairly elegant dependencies between material/fitting parameters and two important factors of mechanical properties of paper: dry solids content and anisotropy. In this paper the dependency of a plastic strain on dry solids content and anisotropy is estimated using the introduced stress-strain curve model. Correspondingly, the model can be used to estimate many other mechanical behaviors, for example, the tension differences arising from non-uniform moisture content of the paper web profile. However, the main target of this study is to produce competent parameters based on modeled stress-strain curves for further construction of a material model. This elasto-plastic material model will be utilized in out-of-plane deformation and fracture models. © 2013 Elsevier Ltd. All rights reserved.


Puttonen J.,Magister Solutions Ltd. | Chernogorov F.,Magister Solutions Ltd.
IEEE Vehicular Technology Conference | Year: 2014

In 3rd Generation Partnership Project (3GPP), enhancements of Diverse Data Applications (eDDA) work item has targeted at improving always-on connectivity for smartphones, identifying and specifying mechanisms at the Radio Access Network (RAN) level to enhance the ability of 3GPP Long Term Evolution (LTE) to handle diverse traffic profiles. The key aspects are the Radio Resource Control (RRC) release timer for User Equipment (UE) state control between connected and idle modes, and Discontinuous Reception (DRX) targeted for minimizing the UE power consumption in connected state. There exist important tradeoffs between UE power consumption, Quality-of-Service and RAN/core network signalling load. What's more, these tradeoffs may be dependent on the UE mobility/velocity. In this article we study the effect of DRX and RRC release timer parameterization on UE mobility performance in heterogeneous networks. These results can be applied to parameter optimization of DRX and RRC release. © 2014 IEEE.

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