Publications 2016

Conference articles (10)

H. Martikainen, I. Viering and B. Wegmann, “Dynamic Range Aware LTE Uplink P0 Optimization in HetNet“, Proc. of the IEEE International Conference on Communications (ICC’16), Kuala Lumpur, Malaysia, May 23-27, 2016.

Power control is essential for uplink multi-user access of Long Term Evolution (LTE). It guarantees that the received uplink power is kept within reasonable dynamic range such that the weak signals from large distance users do not get lost due to limited resolution of the eNB’s Analog-to-Digital Converter (ADC).

Capacity optimization of the open loop power control (OLPC) parameter P0 is applicable cell-individually for Macro deployments but fails in combination with small cells using the same frequency carrier, i.e. in heterogeneous networks (HetNet).

In this paper, we show that an autonomous cell-individual Self-Optimizing-Network (SON) algorithm using cell internal optimization criteria like power headroom (PHR) reports and receive power dynamic range to increase P0 leads to good performance in macro-only layout. However, for co-channel HetNet deployment with embedded pico cells the inter-cell interference among the layers must be taken into account by means of propagation information exchange.

We present a novel enhanced HetNet SON approach for P0 optimization where P0 value for a pico is calculated based on network configuration and the path loss of the weak macro cell-edge User Equipments (UEs) L_max. The results show that approach can limit the P0 at safe level when pico cell could cause too much inter-cell interference to macro cell and on the other hand has higher limits when pico cell UEs are not interfering macro cell.

This method offers a simple way to boost uplink capacity in macro and HetNet layouts while taking the uplink dynamic range and inter-cell interference into account.

J. Turkka, P. Kela, X. Gelabert, M.Costa, K. Heiska, K. Leppänen, C. Qvarfordt, “Supporting Mobility in 5G: A Comparison Between Massive MIMO and Continuous Ultra Dense Networks“, Proc. of the IEEE International Conference on Communications (ICC’16), Kuala Lumpur, Malaysia, May 23-27, 2016.

This paper proposes an approach for providing 5G services to mobile users that is based on continuous ultra dense networks (C-UDNs). The proposed approach outperforms the widely accepted solution based on macro cells and massive MIMO systems (M-MIMO).

In particular, we show that the performance of M-MIMO systems deployed on macro cells is significantly limited by channel aging. The proposed mobility solution based on uplink beacons overcomes the handover problem often linked to UDNs.

Dense networks make it possible for users to transmit at a power lower than that of macro cells, thus making C-UDN more robust to pilot contamination and allowing for lower Channel State Information (CSI) latencies due to shorter reuse distance of UL pilots. Extensive numerical results from detailed systemlevel simulations are provided in order to compare and highlight the benefits of the proposed C-UDN mobility solution to that of a macro M-MIMO deployment.

D. Petrov, T. Hämäläinen, S. Melnik, “Asymptotic Presentation of Intrinsic Interference for FBMC/OQAM Signals in Quasi-Static Channels“, Proc. of European Wireless Conference 2016, Oulu, Finland, May 18-20, 2016.

The paper presents an in-depth analysis of interference intrinsic to the FBMC/OQAM systems when the signal is transmitted over frequency-dispersive channels. This kind of effect appears due to the real-time orthogonality introduced in the filter bank for the sake of much better frequency containment of the signal.

FBMC is a promising alternative to OFDM in applications where more efficient and flexible spectrum utilization should be achieved, for example in wide-band PMR systems, cognitive radios, coexistence scenarios, etc.

Closed-form asymptotic expressions developed in the study provide insight into FBMC/OQAM interference situation. In the channels with deep fades, intrinsic interference can have a considerable impact on the sub-carrier SINR of the received signal.

The results of the paper provide an important theoretical basis for the prediction of linklevel performance, in particular for link-to-system interface used in system-level simulations. The findings of the study can also be used for practical applications, such as parallel equalization in FBMC receivers.

J. Turkka, P. Kela, M. Costa, M. Koivisto, J. Werner, A. Hakkarainen, M. Valkama, R. Jäntti, K. Leppänen, “Location Based Beamforming in 5G Ultra-Dense Networks“, Proc. of the IEEE Vehicular Technology Conference (VTC Fall), 2016 IEEE, Montreal, Canada, 18–21 September, 2016.

In this paper we consider transmit (Tx) and receive (Rx) beamforming schemes based on the location of the device. In particular, we propose a design methodology for the Tx/Rx beamforming weight-vectors that is based on the departure and arrival angles of the line-of-sight (LoS) path between access-nodes (ANds) and user-nodes (UNds).

A network-centric extended Kalman filter (EKF) is also proposed for estimating and tracking the directional parameters needed for designing the Tx and Rx beamforming weights. The proposed approach is particularly useful in 5G ultra-dense networks (UDNs) since the high-probability of LoS condition makes it possible to design geometric beams at both Tx and Rx in order to increase the signal-to-interference-plus-noise ratio (SINR).

Moreover, relying on the location of the UNd relative to the ANds makes it possible to replace fullband uplink (UL) reference signals, commonly employed for acquiring the channel-state-information-at-transmitter (CSIT) in time-division-duplex (TDD) systems, by narrowband UL pilots. Also, employing the EKF for tracking the double-directional parameters of the LoS-path allows one to reduce the rate at which UL reference signals are transmitted.

Consequently, savings in terms of time-frequency resources are achieved compared to beamforming schemes based on full-band CSI. Extensive numerical results are included using a realistic ray-tracing based system-level simulator in ultra-dense 5G network context.

Results show that position based beamforming schemes outperform those based on full-band CSI in terms of mean user-throughput even for highly mobile users.

J. Turkka, P. Kela, M. Costa, “On the Spatial Consistency of Stochastic and Map-based 5G Channel Models“, Proc. of the IEEE Conference on Standards for Communications & Networking (CSCN’16), Berlin, Germany, 31 October – 2 November, 2016.

The 5th Generation (5G) of wireless mobile communication systems is currently the focus of many research projects and standardization bodies, such as the 3rd Generation Partnership Project (3GPP). Accurate modeling of the radio propagation channel is important for evaluating the performance of candidate technologies for 5G.

However, the state-of-the-art radio channel models, such as the 3GPP 3D channel model, are not appropriate for analyzing all use-cases and scenarios commonly considered for 5G mainly due to its inherent stochastic nature. In particular, the difficulty in dealing with long-term spatial consistency and lack of correlation of small-scale parameters motivates using channel models based on ray-tracing.

In fact, channel models that provide spatially consistent observations are of fundamental importance in assessing the performance of multiuser and massive MIMO schemes, by taking into account the spatial correlation of small-scale parameters, as well as of continuous ultra-dense networks (UDNs).

This paper shows, by means of extensive numerical results, that the 3GPP 3D channel model consistently underestimates the achievable SIR in LoS multiuser MISO settings.

However, in NLoS scenarios and urban micro-cell deployments, the 3GPP 3D channel model significantly overestimates the SIR experienced by the users. Hence, the achievable performance of massive MIMO schemes and continuous UDNs can only be assessed with channel models that take into account the spatial correlation of small-scale parameters.

P. Lähdekorpi, K. Schober, M. Kokkonen, M. Mäenpää, M. Enescu, “CSI Enhancement for Multi-User Superposed Transmission Using the Second Best Feedback“, Proc. of the IEEE 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications 2016, Valencia, Spain, September 4-7, 2016.

In this paper we investigate and enhance the user-pairing probability in a system employing multi-user superposition transmission (MUST). In order to improve the multiuser pairing probability, we propose an additional feedback of the second best channel state information (CSI) consisting of channel quality indicator (CQI) and precoding matrix indicator (PMI).

We analyze the pairing-probability and show that the additional feedback increases significantly the pairing possibilities at the scheduler. By system level simulations we confirm that the proposed enhanced feedback is improving significantly MUST performance in the context of MUST operation on the same-beam with Gray-mapped super-constellation.

In addition, we suggest a simple link-to-system mapping for maximum likelihood (ML) MUST receiver, which can re-use legacy mutual-information-to-block-error-rate tables.

J. Puttonen, J. Zhang, O. Puchko, J. Kurjenniemi, H. Kim, H. Paaso, J. Seppänen, P. Järvensivu, P. Salaris, A. Masci, R. Romanato, D. Di Lanzo, S. Falzini, G. Martini, A. Pagnani, N. Buchanan, I. Aguillar Sanches, “Robust telemetry system for future launchers“, ESA International Workshop on Tracking, Telemetry and Command Systems for Space Applications (TTC 2016), Noordwijk, The Netherlands, September 13 – 16, 2016.

This article presents a consideration of a new robust telemetry (TM) system for future launchers. The main target is to increase the maximum data rate of TM system to at least 5 Mbps with improvements such as more efficient physical layer, advanced antenna solutions, lossless data compression, satellite relays, and adaptive coding and modulation (ACM).

An extension module for Network Simulator 3 (ns-3) for launch vehicle (LV) TM communications was developed, which is capable of evaluating the system performance and potential gains of the proposed enhancements.

The results show that the proposed telemetry system can reach close to the target capacity with new physical layer modulation and coding scheme and the performance may be further improved with retro directive antenna array and satellite relays.

J. Puttonen, L. Sormunen and J. Kurjenniemi, “Radio Resource Management in DVB-RCS2 Satellite Systems”, Proc. of the 34th AIAA International Communications Satellite Systems Conference, Cleveland, USA, October 18 – 20, 2016.

The 2nd generation interactive satellite return channel specifications DVB-RCS2 have been standardized by ETSI in 2014. DVB-RCS2 specification provides flexible, adaptive and efficient means to manage the radio resources of the return link.

However, many of the major features of the return link have been left open for implementation, such as Demand Assignment Multiple Access (DAMA) capacity evaluation algorithms and burst scheduler; the former being used for indicating the capacity needs of Return Channel Satellite Terminals (RCSTs) to the Network Control Center (NCC) and latter for scheduling the burst based on the received capacity requests from RCST.

This article studies these specific Radio Resource Management (RRM) algorithms and presents a performance analysis by using an open-source system simulator called Satellite Network Simulator 3 (SNS3).

J. Puttonen, S. Rantanen, L. Sormunen and J. Kurjenniemi, “Performance Analysis of Secure Multicast Service Delivery over Multi-spot Beam Satellite Network“, Proc. of the 22nd Ka and Broadband Communications Conference, Cleveland, USA, October 18 – 20, 2016.

Secure multicast services on top of multi-spot beam satellite networks is an attractive combination. The services can benefit from the inherent advantages of the satellite system, such as large coverage area, as well as effective multicast transmissions. However, security solutions must address multi-spot beam interactive satellite system specific challenges to offer seamless access for the users.

This article presents an end-to-end performance assessment of secure multicast service delivery over multi-spot beam geostationary satellite network. The security framework relies on IP security with multicast extensions and Group Domain of Interpretation (GDOI) multicast key management.

Several performance enhancements are proposed for the delivery of secure interactive unicast/multicast services on top of multi-spot beam satellite networks and their performance are analysed with extensive network level simulations.

The results indicate that Logical Key Hierarchy (LKH) should be preferred in case periodical, forward or backward security is required. In addition, in satellite context, the signalling overhead may be reduced by making spot-beam specific rekey groups.

Higher layer control message prioritization and rekey repetition improves the multicast security signalling enabling smaller drop rates and less reconnections. Secure PEP is identified as a promising alternative to enable different performance enhancement functions for encrypted unicast and multicast data flows.