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.

Distribution Of Cell-Common Downlink Signals In A Hierarchical Heterogeneous Cell Deployment

Abstract: A high-power point (110) and one or more low-power points (120) transmit signals that are associated with the same cell-identifier in a heterogeneous cell deployment. The coverage areas corresponding to the low-power points (120) fall at least partly within the coverage area for the high-power point (110), so that mobile stations (130) within range of a low-power point are also within range of the high-power point (110), from a downlink perspective. The same CRS signals are transmitted by both the high-power (macro) point (110) and some or all of the low-power (pico) points (120). At the same time, the network transmits CRS-based PDSCH for a particular UE on both the high-power point (110) as well as on some or all of the low-power points (120). In some embodiments only a subset of the points, e.g., those points that the UE hears sufficiently well, participate in the PDSCH transmission using CRS for channel estimation.

Key features of the LTE radio interface

Abstract: Mobile broadband based on high-speed packet access (HSPA) technology is already a great success. But even so, to meet future demands for mobile broadband services, the industry must further improve service delivery, for example, through higher data rates, shorter delays, and even greater capacity. These are the very targets of 3GPP radioaccess networks, specifically through HSPA Evolution and LTE. Ericsson is committed to the development of HSPA and LTE as can be seen through an active driving role in standardization and open prototyping. Examples of improved performance compared with early 3G systems include peak data rates in excess of 300Mbps, delay and latencies of less than 10ms, and manifold gains in spectrum efficiency. LTE can be deployed both in new and existing frequency bands and it facilitates simple operation and maintenance. In addition, LTE both targets smooth evolution from legacy 3GPP and 3GPP2 systems and constitutes a major step toward IMT-Advanced (International Mobile Telecommunication – Advanced, sometimes referred to as 4G). In fact, LTE includes many of the features originally considered for a future 4G system.

Uplink scheduling in a cellular system

Abstract: A method for use in a wireless cellular access system, according to which users in a cell in the system receive one or more transmission power control commands on a control channel, where the transmission power control commands comprise an identifier for the intended user or users, said identifier being either an identifier for a specific user or for a group of users. A user disregards one or more predefined control commands if the identifier of the control command is for a group of users in which said user is included.

Method and system for providing autonomous retransmissions in a wireless communication system

Abstract: A transmitter that may have marginal power availability is enabled to autonomously retransmit previously transmitted frames containing the same data. The transmitter sends an initial frame to a base transceiver station (BTS) and immediately retransmits the same frame without regard to any ACK/NAK transmission from the BTS. The retransmissions are accumulated in the receiver and decoded after a sufficient quantity of the frame is transmitted. After receiving the last retransmitted frame the BTS sends an ACK/NAK to the transmitter that is accepted.

Technique for radio resource management

Abstract: A radio resource management technique in a cellular telecommunication system is disclosed. The telecommunication system comprises at least one radio network controlling component and one or more base station components operable to implement an uplink scheduling scheme in relation to one or more user terminals. A method embodiment comprises the steps of receiving, by one of the base station components from the at least one radio network controlling component, at least one interference control parameter, of generating one or more scheduling grants taking into account the at least one interference control parameter, and of issuing the one or more scheduling grants to one or more 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. >