Article

The road to IMT-advanced communication systems: State-of-the- art and innovation areas addressed by the WINNER + project

Ericsson AB, Stockholm
IEEE Communications Magazine (Impact Factor: 4.46). 07/2009; DOI: 10.1109/MCOM.2009.5116799
Source: IEEE Xplore

ABSTRACT Phases I and II of the WINNER project contributed to the development, integration, and assessment of new mobile network techniques from 2004 to 2007. Some of these techniques are now in the 3GPP LTE and IEEE 802.16 (WiMAX) standards, while others are under consideration for LTE-Advanced and 802.16m. The WINNER+ project continues this forwardlooking work for IMT-advanced technologies and their evolution, with a particular focus on 3GPP LTE-advanced. This article provides an overview of the WINNER system concept and several of its key innovative components.

0 Bookmarks
 · 
92 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The practical time-varying channel between a high-speed train (HST) and infrastructure has a single Doppler shift on each resolvable multipath in most cases. As a result, the HST channel can be modelled by only 2L parameters: L Doppler shifts and L complex channel gains. Based on this observation, we propose a novel channel estimation technique for orthogonal frequency-division multiplexing (OFDM) systems running on a HST, with the name PIece-wise Time-Invariant Approximation (PITIA). In PITIA, the HST channel is approximated by a bunch of time-invariant channels, whose channel impulse responses (CIRs) can be estimated through pilots. Variations of these CIR samples over time derive both Doppler shifts and complex channel gains, so the whole time-varying channel can be reconstructed. PITIA enjoys low computation complexity of O(NL)O(NL) for N subcarriers. The optimal duration of time-invariant channels used to approximate HST channel is derived from both analytical analysis and simulations. Compared to basis expansion model (BEM) methods, PITIA uses fewer channel parameters with comparable modelling error, shows better normalized mean squared error (NMSE) performance under high-mobility and high signal-to-noise ratio (SNR) environments, and achieves comparable NMSE in low SNR regime.
    Vehicular Communications. 04/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Inter-cell interference coordination (ICIC) is attracting attention recently. This is a technique mainly improving cell-edge throughput by coordinating scheduling and signal transmission of multiple BSs. Different from joint transmission (JT), in which the desired signals for a user equipment (UE) are simultaneously transmitted from multiple BSs, the burdens of information exchange among BSs and its attendant signal processing are mitigated in ICIC because it requires only the exchange of scheduling and control information. In ICIC, the cell-edge throughput is improved by adaptively preventing BSs from transmitting signals (in other words, muting BSs) that would otherwise impose strong interference on the cell- edge UEs in the neighbor cells. Although this improves cell-edge throughput, it may degrade cell overall performance because no radio resource is assigned to UEs belonging to the muted BS. To resolve this issue, we first propose a scheduling method, which enables muting only when the throughput improvement (cell-edge UE) obtained by muting is superior to the total throughput possible without muting. Also, when considering applying this ICIC technique to current commercial systems such as LTE, it should be noted that reference signal, also known as pilot signal, is always transmitted regardless of muting because reference signal is a common signal used for channel estimation. To solve this issue, we also propose a reference signal interference canceller, in which the UE cancels the reference signal being transmitted from the neighbor BS. We evaluate the performance improvement by computer simulations and confirm that cell-edge throughput is dramatically improved by introducing the proposed canceller. We also propose a control algorithm that activates the canceller only when throughput improvement is possible. A basic lab experiment was also conducted to confirm the effect of the proposed interference canceller with 3GPP Rel-8 LTE-compliant equipment.
    Vehicular Technology Conference (VTC Spring), 2012 IEEE 75th; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: The knowledge of channel state information (CSI) is crucial for improving the performance of cooperative communication systems. In multiuser two-hop relay systems, the global CSI between a relay and multiple source-and-destination nodes can be estimated at the relay, and the local CSI between each node and the relay can be estimated at each node. In this paper, we analyze the spectral efficiency of multicarrier code-division multiple-access (MC-CDMA) two-hop relay systems, either with global CSI only at the relay or with local CSI only at every node. We resort to asymptotical analysis with random-matrix theory to derive the average spectral efficiency of decode-and-forward (DF) and amplify-and-forward (AF) two-hop relay systems. We then analyze the impact of spreading sequences, fading channel statistics, and low-complexity transceivers. Analytical and simulation results show that when an orthogonal spreading sequence is used, the relay system with local CSI only at every node is spectrally more efficient than that with global CSI only at the relay. Moreover, an artificially constructed one-tap spreading sequence can achieve a good tradeoff between the performance and the complexity.
    IEEE Transactions on Vehicular Technology 10/2012; 61(8):3603-3614. · 2.64 Impact Factor

Full-text (2 Sources)

Download
267 Downloads
Available from
May 30, 2014