Wireless Communications

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.

Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas

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].

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Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays

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.

Two decades of array signal processing research: the parametric approach

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. >

On the capacity of a cellular CDMA system

The present disclosure relates to a technique for transmitting modulation symbols on multiple frequency resources. A method aspect of this technique includes applying a Discrete Fourier Transform (DFT) coding per set of modulation symbols of two or more sets of modulation symbols, wherein a first set of modulation symbols from the two or more sets of modulation symbols is transmitted on a set of frequency resources handled by the same power amplifier. Then, Orthogonal Frequency Division Multiplexing (OFDM) modulation is applied to the sets of DFT coded modulation symbols to output a first set of OFDM symbols for transmission on the set of frequency resources, and output another set of OFDM symbols for transmission on at least one additional frequency resource distinct from the set of frequency resources. Power amplification is then applied per set of frequency resources at the power amplifier.

Technique for transmitting on multiple frequency resources in a telecommunication system

The invention relates to a method in a user equipment 4 for determination of timing of a Hybrid Automatic Repeat re-Request, HARQ, response. The user equipment 4 operates in a communication network 1 comprising a primary radio access technology system 2and a secondary radio access technology system 3. The user equipment 4 receives on at least one downlink carrier on the first radio access technology system 2 and on at least one downlink carrier on the second radio access technology system 3. The method comprises determining a downlink timing related to the secondary radio access technology system 3; determining a virtual uplink timing for HARQ response on the secondary radio access technology system 3 based on the downlink timing; determining an uplink timing related to the primary radio access technology system 2; and determining, based on the virtual uplink timing and the uplink timing for the primary radio access technology system 2, an uplink time instance for transmission of the HARQ response on an uplink carrier of the primary radio access technology system 2, wherein the HARQ response relates to data received on the downlink carrier on the secondary radio access technology system 3. The invention also relates to user equipment, radio base stations and methods therein.

Determining timing of feedback information in wireless networks realised in different technologies

A method in a first user equipment (121) for adjusting a beacon signal (140) to be detected by at least one second user equipment (122) in a wireless telecommunications network (100) is provided. The beacon signal (140) is transmitted in order to enable an establishment of Device-to-Device, D2D, communication between the first user equipment (121) and the at least one second user equipment (122). The method is characterized in that the method comprises adjusting (205), prior to transmitting the beacon signal (140), the transmit power of the beacon signal (140) based on a requirement of an application in the first user equipment (121) for which the D2D communication is to be established. A user equipment (121), a network node (110), and a method in a network node (110) for enabling a D2D communication between a first user equipment (121) and at least one second user equipment (122) are also provided.

User equipment, a network node, and methods for device discovery in device-to-device (d2d) communications in a wireless telecommunications network

A method of scheduling wireless data transmissions between a mobile terminal (701) and a base station using multiple component carrier signals is disclosed. The method comprises the steps of: receiving in the mobile terminal information from the base station indicating available component carriers; detecting in the mobile terminal at least one dynamic parameter indicative of the mobile terminal's current ability to handle component carriers having non-contiguous bandwidths; determining in the mobile terminal in dependence of the at least one dynamic parameter which of the available component carriers to utilize; and transmitting from the mobile terminal to the base station information indicating the component carriers determined to utilize. By doing this the mobile terminal may choose to limit the number of component carriers used in situations where it is disadvantageous, such as situations where the power consumption of supporting multiple component carriers is high or situations where complex hardware is needed.

Stefan Parkvall

Papers

Technique for transmitting on multiple frequency resources in a telecommunication system

Determining timing of feedback information in wireless networks realised in different technologies

User equipment, a network node, and methods for device discovery in device-to-device (d2d) communications in a wireless telecommunications network

Scheduling Data Transmissions Between a Mobile Terminal and a Base Station in a Wireless Communications Network Using Component Carriers

5G Evolution and Beyond