Academic Theses (1)
O. Puchko, “Multipoint Transmission Scheme for HSDPA“, Ph.D. Thesis, ISBN 978-951-39-5477-2, University of Jyväskylä, 2013.
This thesis presents one of the multipoint transmission schemes for HSDPA, a scheme referred to as HS-SFN. This scheme can increase the peak data rate for the UEs in the softer handover area, or UEs that are located in the border between two cells belonging to the same Node B.
The study also considers the techniques that can increase the performance of HS-SFN, such as the enhanced type3 receiver, phase adjustment and common intra-site scheduler.
The HS-SFN study is carried by means of extensive system-level simulations employing a semi-static network simulation tool for HSDPA.
The simulation tool includes detailed modeling of propagation model, radio resource management algorithms, physical layer and a part of the upper layers of HSDPA radio access network.
Conference articles (12)
Z. Chang and T. Ristaniemi, “Asymmetric Resource Allocation for OFDMA Networks with Collaborative Relays”, Proc. The 10th Annual IEEE Consumer Communications and Networking Conference (IEEE CCNC), Las Vegas, NV, January 11-14, 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 allocations. We derive theoretical expressions for the solutions and illustrate them through simulations.
The results validate clearly the additional performance gains through asymmetric cooperative scheme compared to the other recently proposed resource allocation schemes.
Z. Chang and T. Ristaniemi, “Energy Efficiency of Collaborative OFDMA Mobile Clusters”, Proc. The 10th Annual IEEE Consumer Communications and Networking Conference (IEEE CCNC), Las Vegas, NV, January 11-14, 2013.
Future wireless communication systems are expected to offer several gigabits data rate. It can be anticipated that the advanced communication techniques can enhance the capability of mobile terminals (MTs) to support high data traffic.
However, aggressive technique induces high energy consumption for the circuits of MTs, which drain the batteries fast and consequently limit mobility. In order to solve such a problem, a scheme called distributed mobile cloud (DMC) is foreseen as one of the potential solutions to reduce energy consumption per node in a network by exploiting collaboration within a cluster of nearby mobile terminals.
In this paper we provide a detailed analysis of the energy consumption of a terminal joining the DMC and also analyze the conditions for energy savings opportunities. Numerical results are also provided to illustrate the analysis and show the potential of significant reduction of the per-node energy consumption in the mobile cloud concept.
B. Herman, D. Petrov, J. Puttonen and J. Kurjenniemi, “A3-Based Measurements and Handover Model for NS-3 LTE“, Proc. of the Third International Conference on Mobile Services, Resources, and Users (MOBILITY 2013), Lisbon, Portugal, November 17-22, 2013.
This paper presents a Long Term Evolution (LTE) handover algorithm implementation based on Reference Signal Received Power (RSRP) measurements and Event A3 on top of the LTE module of NS-3 network simulator.
Many simulation scenarios in various research projects rely on user mobility. However, until recently complete realisation of relevant functionality has been missing in free and open source tools such as NS-3.
Detailed modeling of RSRP measurements, including sliding window averaging, time-to-trigger and hysteresis evaluations are considered in this paper.
Received simulation results are verified through comparison with other publication, suggesting a promising direction for further studies of dynamic scenarios.
Z. Chang and T. Ristaniemi, “Power Efficient Multicast Transmission Framework with QoS Guarantee“, Proc. of the 2013 International Conference on Wireless Communications and Signal Processing (WCSP’13), Hangzhou, China, October, 2013.
Multicast is recognized as an efficient transmission mechanism for delivering large number of common data to different mobile users.
One inherent drawback of multicast transmission is that in order to guarantee the quality of service for each mobile user, the transmitter needs to adapt its data rate to the user(s) with worst channel condition in a multicast group. Therefore, power consumption could be seriously arisen.
In order to address this problem, in this work we propose an energy efficient framework called Multicast Support Multicast (MSM) and examine its energy saving performance. The proposed MSM can dynamically use an extra channel as an additional support for traditional multicast transmission, by which power consumption of transmitter can be reduced.
Moreover, through formulating optimization problem, we also discuss user grouping scheme that allows us to obtain the optimal energy saving gain. Numerical examples are presented to illustrate the proposed scheme and to show the performance gains obtained by employing additional multicast channel(s) and optimal user grouping.
Z. Chang and T. Ristaniemi, “Energy Efficiency of Unicast Supported Multicast with QoS Guarantee“, Proc. of the IEEE International Conference on Communication in China workshop (ICCC’13), China, , 2013.
Multicast transmission is known as an efficient mechanism for offering the same services for different terminals. However, the power consumption is surprisingly arisen due to terminals with the worst channel quality while maintaining the Quality of Service (QoS) and data decoding requirements.
In order to address this problem, we examine the energy saving performance of an efficient algorithm called Unicast Support Multicast (USM), which can dynamically and expeditiously use unicast transmission as an additional support for multicast transmission. The USM algorithm can overcome the inherent drawbacks of multicast transmission, and decrease the power consumption with QoS guarantee.
Numerical results based on the conducted theoretical analysis demonstrate that power consumption is reduced with USM while fulfilling the data rate and decoding requirements. In addition, the energy efficiency of USM is superior compared to pure multicast transmission.
Z. Chang and T. Ristaniemi, “Energy Efficiency of Using Multicast and Unicast in Collaborative OFDMA Mobile Cluster“, Proc. of the 77th IEEE Vehicular Technology Conference (IEEE VTC), Dresden, Germany, June, 2013.
Future wireless services induce higher demands for the circuits of mobile terminals, which will subsequently increase energy usage and hence limit users’ abilities to experience high quality of multimedia services offered by the high data rate wireless systems.
In order to address this problem, we advocate a model called collaborative mobile cluster (CMC), that is foreseen as one of the potential solutions to reduce energy consumption per terminal in a network by enabling collaboration within a cluster of mobile terminals.
We first compare the energy efficiency performance of unicast and multicast transmission strategies within the CMC. In addition, we propose an algorithm that can dynamically use unicast as an additional support for multicast, ultimately overcoming the inherent drawbacks of sole multicast.
Analytical results are derived and illustrated by simulations. The analysis demonstrates that: i) CMC enables a great potential to reduce the per-terminal energy consumption; ii) unicast and multicast transmissions are two optional candidates, but a proper combination of them allows better energy saving gain while still fulfilling the minimum data rate requirement.
F. Chernogorov and J. Puttonen, “User Satisfaction Classification for Minimization of Drive Tests QoS Verification“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications 2013, London, UK, September, 2013.
In wireless mobile networks, the 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, the 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.
F. Chernogorov, T. Ristaniemi, K. Brigatti and S. Chernov, “N-gram Analysis For Sleeping Cell Detection in LTE Networks“, Proc. of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) 2013, Vancouver, Canada, May, 2013.
Sleeping cell detection in a wireless network means to find the cells which are not working properly due to various reasons. The research in the area has mostly focused on cell outage detection, e.g. due to hardware failures at the base station antennas or non-optimal network planning.
In this paper we extend the research into a more challenging setting which is overlooked in the literature: the case where no outages occur in the network.
The essence of the proposed method for detection of problematic cells is to analyze the sequences of the events reported by the mobile terminals to the serving base stations. The suggested n-gram analysis includes dimensionality reduction and classification of the data and ends up with providing a set of abnormal users, which at the end reveal the location of the problematic cell.
We verify the proposed framework with simulated LTE network data and using the minimization of drive testing (MDT) functionality to gather the training and testing data sets.
T. Nihtilä, V. Tykhomyrov, O. Alanen, M. A. Uusitalo, A. Sorri, M. Moisio, S. Iraji, R. Ratasuk and N. Mangalvedhe, “System performance of LTE and IEEE 802.11 coexisting on a shared frequency band“, Proc. of the IEEE Wireless Communications & Networking Conference (WCNC), Shanghai, China, April 7-10, 2013.
This paper presents the system performance analysis of 3GPP Long-Term Evolution (LTE) and IEEE 802.11 Wireless Local Area Networks (WLAN) in a situation where LTE downlink (DL) has been expanded over to unlicensed frequency band usually used by WLAN.
Simple fractional bandwidth sharing mechanism is used to allow both technologies to transmit. The system performance is evaluated by means of fully dynamic network simulations.
T. Hiltunen, M. Lampinen and M. Valkama, “Codebook Design and Link Level Performance of Closed-Loop 4×2 MIMO in HSDPA“, Proc. of the IEEE International Wireless Symposium (IWS), 2013, Beijing, China, 14 -18 Apr , 2013.
The feedback quantization has a considerable impact on the performance of precoded four branch High Speed Downlink Packet Access (HSDPA) MIMO.
As the number of transmit antennas is increased, constructing an efficient quantization scheme becomes more important, and compared to the case of two transmit antennas, more quantization loss needs to be tolerated.
In this paper, the performance of four branch dual-codeword single-user MIMO is evaluated assuming two different types of compact codebooks.
The first of the studied codebooks is similar to the 4-Tx codebook used in Long Term Evolution (LTE) system and the second is a novel multi-granular codebook that tries to address the different short and long term correlation properties of the radio channel. An extension to the multi-granular codebook is also proposed in this paper to further improve the performance.
Simulation results are presented assuming cross-polarized antenna configuration. The link performance is compared to Release 7 2×2 MIMO and 4×2 MIMO with singular value decomposition based unquantized feedback.
The studies show link throughput gains up to 66% for the LTE codebook and up to 79% for the multi-granular codebook compared to the 2×2 MIMO. The relative gains are highest at low geometries where rank 1 transmission is dominant.
D. Petrov, P. Gonchukov, and T. Hidalgo Stitz, “Link to System Mapping for FBMC Based Systems in SISO case“, Proc. of the Tenth International Symposium on Wireless Communication Systems (ISWCS 2013), Ilmenau, Germany, 27-30 August, 2013.
The main emphasis of this paper is on the validation of physical level (PHY) abstraction methods for Filter Bank based Multi-Carrier (FBMC) systems. This kind of abstraction is the required element connecting link and system level simulations involved nowadays as an essential part in the development process of every new technology.
In this paper, we briefly introduce FBMC broadband systems and the scenario of its coexistence with Professional Mobile Radios (PMR). Then we overview existing algorithms of link to system (L2S) mapping.
Finally, a comparison of MI-based algorithms is performed with the help of link level simulator capable to produce Orthogonal Orthogonal Frequency- Division Multiplexing with Cyclic Prefix (CP-OFDM) and FBMC results based on LTE specification.
