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.

Determining configuration of subframes in a radio communications system

Abstract: The technology disclosed provides the ability for a subframe to be configured as a “flexible” subframe As a result, at least three different types of subframes in a TDD system may be configured: a downlink (“DL”) subframe, an uplink (“UL”) subframe, and a “flexible” subframe The use of flexible subframes is determined based on a primary TDD configuration, and in a preferred example, on the existing primary TDD configuration in the network If there is secondary TDD configuration, flexible subframes may be determined based on both the primary and secondary configurations, eg, using specific rules Also, the HARQ feedback timing for downlink (DL) transmissions may be determined based on the secondary TDD configuration Preferred examples ensure that uplink (UL) feedback does not collide with a flexible subframe used for DL transmission The technology preferably is compatible with legacy UEs

Flexible ARQ for packet data transmission

Abstract: The present invention provides a flexible ARQ scheme. A communications channels is set up between a transmitter and a receiver. A value is selected for an ARQ parameter for data packets to be transmitted over the communications channel. The ARQ parameter value may be selected in accordance with a trade-off between a desired performance or goal, e.g., a specific throughput of data packets transmitted over the communications channel, and one or more communication resources required to support the desired performance or goal. An example of an ARQ parameter is a number of outstanding data packets to be acknowledged by the receiver before more packets can be sent to the receiver. Another parameter example is a delay associated with the ARQ scheme. In a preferred, non-limiting example embodiment, first and second ARQ parameter values are selected for a desired trade-off. Accordingly, a specific number of outstanding data packets to be acknowledged by the receiver and an acknowledgement or retransmission delay can be selected to achieve a desired performance, e.g., a desired throughput of data packets, at a particular resource cost. Because of the flexibility provided by the present invention, a communications device may set its own objectives for a particular connection based upon one or more performance requirements, communication resources, or other requirements.

System and method for beam-based physical random-access

Abstract: A method in a wireless device for performing random access to a network node. The method comprises receiving a set of downlink beam-specific reference signals, BRS, from the network node, and determining a preferred BRS based on the received signal power for each BRS. The method also comprises selecting, based on the preferred BRS, a random-access resource to be used for transmitting a random-access attempt to the network node, as well as using the selected random-access resource when transmitting a random-access attempt to the network node, whereby the selection of random-access resource indicates to the network node which downlink beam is preferred by the wireless device to be used for downlink transmissions.

Hybrid arq for packet data transmission

Abstract: The invention relates to a hybrid ARQ scheme with incremental data packet combining. In an example embodiment, the hybrid ARQ scheme with incremental data packet combining employs three feedback signaling commands: ACK, NACK, and LOST. Using these three feedback commands, the hybrid ARQ scheme with incremental data packet combining is provides both robustness and good performance. The invention is particularly advantageous in communication systems with unreliable communication channels, e.g., a fading radio channel, where forward error correction (FEC) codes are used, some of the code symbols being more important than other code symbols. The benefits of the invention are increased throughput and decreased delay of the packet data communication.

Uplink scrambling during random access

Abstract: The technology described in this case facilitates random access by a user terminal with a radio base station. A user terminal determines one of a first type of uplink scrambling sequences and generates a random access message using the determined one of the first type of uplink scrambling sequences. The random access message is transmitted to the base station. The user terminal receives from the base station a second, different type of uplink scrambling sequence and uses it for subsequent communication with the radio base station. For example, the first uplink scrambling sequences may be specifically associated with the radio base station's cell area or a random access radio channel associated with the radio base station, but they are not specifically assigned to any user terminal, and the second uplink scrambling sequence may be selected from a second set of uplink scrambling sequences specifically assignable to individual user terminals.

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. >