Stefan Parkvall

Bio: Stefan Parkvall is an academic researcher from Ericsson. The author has contributed to research in topics: Telecommunications link & Node (networking). The author has an hindex of 58, co-authored 502 publications receiving 19083 citations. Previous affiliations of Stefan Parkvall include Royal Institute of Technology & University of California, San Diego.

Information on reference signal structure for neighbouring cell measurements

Abstract: The present invention relates to cellular radio communication and in particular to providing information on neighbour cells to enable terminals to perform neighbour cell measurements. In the prior art the terminal attempts to make neighbour cell measurements in a reference signal structure that is the same in the neighbour cell as in the cell the terminal camps in. The present invention is based on the insight that the reference signal structure may differ between neighbouring cell for example in the situation of an MBSFN area that is restricted to a region of all cells of a radio network, or in the situation of TDD mode being applied there may be different regions with different allocation of sub-frames for transmission in the uplink and downlink directions. The present invention solves the problem by broadcast information in a cell indicative of the reference signal structure in neighbour cells.

The impact of timing errors on the performance of linear DS-CDMA receivers

Abstract: In this paper, an asynchronous direct-sequence code-division multiple-access (DS-CDMA) communication system operating over an additive white Gaussian noise (AWGN) channel is considered. In many applications, the near-far problem can be the limiting factor for the capacity of a DS-CDMA system. Several near-far resistant receivers have, therefore, been proposed (e.g., the decorrelating receiver). These receivers assume perfect knowledge of the propagation delay from all users to the receiver. In practice, the delays are estimated and therefore subject to errors. The performance degradation these errors impose on linear detectors, especially the decorrelating detector, is the topic of this paper.

Radio resource management for a high-speed shared channel

Abstract: Radio resources like spreading codes and transmission power are optimally allocated to various different types of radio channels supported in the cell including a specialized channel like a high-speed shared channel. One or more measurements made at the base station are provided to the radio resource manager. Such measurements include other-channel power, high speed shared channel code usage, high speed shared channel transport format usage, average active load on the high speed shared channel, empty buffer, excess power, and similar parameters that relate to a high speed shared channel. One or more of these reported measurements may then be used to access, allocate, and/or regulate resources associated with the base station's cell.

Technique for performing a random access procedure over a radio interface

Abstract: The invention relates to a technique for performing a random access procedure over a radio interface (106), for example between a mobile terminal (102) and a radio base station (104) of a mobile network (108). A method aspect of the invention comprises the steps of transmitting a synchronization request (112) for synchronization information; receiving synchronization information (114) in response to the synchronization request; and transmitting, based on at least one transmission parameter adjusted in accordance with the synchronization information, a resource request (116) for data transmission resources.

The high speed packet data evolution of WCDMA

Abstract: The first step of evolving WCDMA towards higher data rates through the introduction of HSDPA is discussed. By applying fast link adaptation together with higher order modulation, fast hybrid ARQ and fast scheduling, the best-effort packet data support of WCDMA can be improved in terms of increased throughput, lower delays and increased peak data rates. Simulations illustrate the potential of the concept.

Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas

Abstract: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.

Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays

Abstract: Multiple-input multiple-output (MIMO) technology is maturing and is being incorporated into emerging wireless broadband standards like long-term evolution (LTE) [1]. For example, the LTE standard allows for up to eight antenna ports at the base station. Basically, the more antennas the transmitter/receiver is equipped with, and the more degrees of freedom that the propagation channel can provide, the better the performance in terms of data rate or link reliability. More precisely, on a quasi static channel where a code word spans across only one time and frequency coherence interval, the reliability of a point-to-point MIMO link scales according to Prob(link outage) ` SNR-ntnr where nt and nr are the numbers of transmit and receive antennas, respectively, and signal-to-noise ratio is denoted by SNR. On a channel that varies rapidly as a function of time and frequency, and where circumstances permit coding across many channel coherence intervals, the achievable rate scales as min(nt, nr) log(1 + SNR). The gains in multiuser systems are even more impressive, because such systems offer the possibility to transmit simultaneously to several users and the flexibility to select what users to schedule for reception at any given point in time [2].

Two decades of array signal processing research: the parametric approach

Abstract: The quintessential goal of sensor array signal processing is the estimation of parameters by fusing temporal and spatial information, captured via sampling a wavefield with a set of judiciously placed antenna sensors. The wavefield is assumed to be generated by a finite number of emitters, and contains information about signal parameters characterizing the emitters. A review of the area of array processing is given. The focus is on parameter estimation methods, and many relevant problems are only briefly mentioned. We emphasize the relatively more recent subspace-based methods in relation to beamforming. The article consists of background material and of the basic problem formulation. Then we introduce spectral-based algorithmic solutions to the signal parameter estimation problem. We contrast these suboptimal solutions to parametric methods. Techniques derived from maximum likelihood principles as well as geometric arguments are covered. Later, a number of more specialized research topics are briefly reviewed. Then, we look at a number of real-world problems for which sensor array processing methods have been applied. We also include an example with real experimental data involving closely spaced emitters and highly correlated signals, as well as a manufacturing application example.

On the capacity of a cellular CDMA system

Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >