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.

Subframes in a cellular communications system

Abstract: The invention discloses a method for a cellular communications system, in which traffic is sent in frames, each frame comprising a first number of subframes, with a second number of said subframes being available for at least either uplink or downlink traffic. At least one of said second number of subframes is made to comprise at least three parts, as follows: One part which is utilized for uplink traffic, One part which is utilized for downlink traffic, One part which is utilized as a guard period, with said guard period part being scheduled between the uplink and the downlink parts. The duration of at least two of said three parts may be varied to fit the current system need.

Controlling Energy Consumption of a Wireless Network Node

Abstract: An arrangement for controlling energy consumption of a network node associated with a cell includes a terminal activity monitor (16) configured to detect active terminals served by the cell. A transmission controller (18) is connected to the terminal activity monitor and is configured to restrict transmission downlink in the cell during time periods when there are no active terminals served by the cell. During these time periods transmission is restricted to inermittent transmission of information assisting active terminals not served by the cell in finding the cell.

A Wireless Device, a Radio Node, and Methods Therein

Abstract: A wireless device 108 and a method therein for assisting in precoder selection for wireless communication with a Radio Node (RN) 106 , and a RN 106 for performing precoder selection for wireless communication with a wireless device 108 . The wireless device is configured with a set of precoders. The wireless device determines a subset of precoders out of the set of precoders; and transmits, to the RN, at least one Sounding Reference Signal (SRS) precoded with a respective at least one precoder comprised in the subset. The RN receives, from the wireless device, at least one SRS precoded with a respective at least one precoder comprised in a subset of precoders; and transmits, to the wireless device, a signal indicative of a selected precoder to be used for a transmission to the RN, wherein the selected precoder is indirectly selected based on the received at least one SRS.

Switching between Open and Closed Loop Multi-Stream Transmission

Abstract: The present invention relates to a method and apparatus for multi-stream wireless communication between a transmitter node and a receiver node. The method comprises applying an open-loop multi-stream transmission technique during an initial part of a transmission burst. In another step of the method, detailed channel state information is received (54). The detailed channel state information indicates transmission pre-coding to be used during the transmission burst when applying a closed-loop multi-stream transmission technique. The method further includes switching (55) from the open-loop multi-stream transmission technique to the closed-loop multi-stream transmission technique during the transmission burst, in response to receiving the detailed channel state information. The method is applicable to both uplink and downlink transmission bursts.

Method and arrangement for reducing power consumption in a mobile communication network

Abstract: The invention relates to a method and an arrangement for reducing power consumption of a receiver in a mobile communication network comprising a sender transmitting packet data on a downlink channel to one or more receivers over a radio interface. Inactive time instants and listening time instants are defined according to provided rules. The receiver is arranged to listen for information from the sender during the listening time instants and to sleep during the inactive time instants. Thus, less power will be consumed during the inactive time instants.

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. >