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.

Downlink scheduling in heterogeneous networks

Abstract: The present invention provides methods to support scheduling of transmissions from a pico base station or micro base station to a mobile terminal operating in a link imbalance zone where interference from macro base station is present. A method is provided to enable the mobile terminal to detect when it is in a link imbalance zone, and for triggering scheduling restrictions when the mobile terminal is in the link imbalance zone.

Wireless device, network node, methods therein, for respectively sending and receiving a report on quality of transmitted beams

Abstract: Embodiments herein relate to a method performed by a wireless device (850) for sending a report on channel information to a network node; a method performed by a network node (830) for receiving a report on channel information; a wireless device (850) and a network node (830).The network node (830) controls at least one Transmission Point (TP) that transmits TP beams. Each TP beam is associated with respective beamformed Beam-specific Reference Signal (BRS) for channel information measurements. The wireless device (850) sends the report, which comprises a number of sub-reports, to the network node (830). Each sub-report is associated with a TP beam. Each associated TP beam comprises at least one BRS and is selected by the device (830).. Each sub-report is also associated with an indicator of channel quality value for one code word transmitted by the network node (850) on the associated TP beam. Publ. Figure 17

Methods and devices relating to downlink assignments

Abstract: The invention relates to a method in a first communication device of receiving control information over a radio channel from a second communication device. The first communication device receives a subframe over the radio channel, and determines whether the subframe is a downlink subframe with downlink assignment intended for the first communication device by reading data in the subframe. That being the case, the first communication device decodes data within the subframe, and determines whether any data packet being sent from the second communication device before the subframe has been missed by analysing an indicator associated to the subframe in the data. The indicator provides knowledge about previous downlink subframes with downlink assignment intended for the first communication device.

Variability of user performance in cellular DS-CDMA-long versus short spreading sequences

Abstract: The uplink performance in a cellular direct-sequence code-division multiple-access system using long and short spreading sequences is compared in terms of the distribution of the bit-error probability. Three different receiver types are considered: conventional; MMSE; and interference cancellation, both with and without forward-error correction. The short code system has a slightly higher performance variability among the user population than the corresponding long code system, which requires attention when designing a short code system. Code hopping as a technique to mitigate this is investigated.

Performance of WCDMA high speed packet data

Abstract: WCDMA release 5 supports peak bitrates for data services in the order of 10 Mbit/s, together with reduced delays and increased system throughput. In this paper, a brief introduction to release 5 is given and radio resource management principles associated with the high speed packet data bearers are discussed. Scheduling performance for WWW services, provision of bearers for streaming services, as well as the simultaneous use of high speed packet data bearers and conversational bearers is elaborated upon. Simulation results indicate that with appropriate radio resource management, all the above challenges may be successfully dealt with.

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. >