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

This paper provides a detailed overview of the key technology features of the new 5G/NR radio-access technology, the first release of which has recently been published by 3GPP release 15, of the NR specifications finalized by the end of 2017. This first release is limited to non-standalone NR operation, implying that NR devices rely on LTE for initial access and mobility. The final release-15 specifications, to be available in June 2018, will also support stand-alone NR operation. The difference between stand-alone and non-standalone operation is primarily affecting higher layers and the interface to the core network; the basic radio technology is the same in both cases. This paper will give a detailed overview of the NR radioaccess technology with focus on the key features that distinguish it from 4G LTE.

NR - The New 5G Radio-Access Technology

Methods and apparatus for generating and determining multi-component carrier cells, without the use of neighbor-cell lists, are described. Methods for generating and informing a communication system terminal about other component carriers belonging to a certain cell identity (ID), and methods and apparatus for a mobile terminal utilizing extended synchronization information for doing multi-component carrier cell search are described. Also, methods for multi-component carrier measurements and methods of reporting such measurements to a network are described.

Identifying Multi-Component Carrier Cells

A mobile terminal sends rapidly changing information relating to the downlink transmission of packet data from a base station sector to the mobile terminal at a higher rate on a fast channel. This rapidly changing information may include, for example, a current data transmission rate and/or current base station sector identification. Information that changes more slowly, such as the identification of a base station to handle the mobile terminal communication, is communicated to the base station at a lower rate on a slow channel. The information received from the mobile terminal at the higher rate is used by the base station to request a particular sector (and preferably also a sector antenna) to transmit data to the mobile terminal and/or to adjust the current maximum data transmission rate to the mobile terminal. A mobile terminal may also make similar sector/rate requests from plural sectors at the same time as well as from plural sector antennas.

Efficient radio link adaptation and base station sector selection in a radio communication system

The present invention relates to methods and arrangements for handling unreliable scheduling grants in a WCDMA-communication system. A user equipment detects that a received scheduling grant is unreliable and adjust its serving grant based on that information. The user equipment is also able to report continuously received unreliable grants as an event to the network, allowing the network to adapt its operation to reduce the unreliable grants.

Methods and arrangements for handling unreliable scheduling grants in a telecommunication network

There is provided a method in a cellular telecommunications network, the cellular telecommunications network comprising at least a first cell and a second cell. The method comprises the steps of transmitting (302) first periodic physical signals, usable by a device to determine its location, to the first cell; and transmitting (304) second periodic physical signals, usable by a device to determine its location, to the second cell. The second periodic physical signals are synchronized with the first periodic physical signals and have a timing offset, such that the first periodic physical signals and the second periodic physical signals are not transmitted simultaneously. The method is characterized in that transmission of data or control signals to the first cell is inhibited when the second periodic physical signals are transmitted to the second cell.

Stefan Parkvall

Papers

NR - The New 5G Radio-Access Technology

Identifying Multi-Component Carrier Cells

Efficient radio link adaptation and base station sector selection in a radio communication system

Methods and arrangements for handling unreliable scheduling grants in a telecommunication network

Methods and arrangements in a telecommunication system