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 invention relates to a method and an arrangement for obtaining efficient radio resource allocation in a mobile communication network comprising a communication network entity (15) and at least one user equipment (18) transmitting data to said mobile communication network entity (15) over a radio interface. A first data transmission from said at least one user equipment (18) is received, whereby said first transmission is decoded and a message (ACK/NACK) based on a result of the decoding is sent on a downlink channel (13) comprising information of said first received data transmission. A second data transmission from said at least one user equipment (18) is received, whereby the power on said downlink channel (13) is adjusted depending on the result of said decoding and the content in said received second data transmission.

Arrangement And Method In A Mobile Communication Network

A method performed by a wireless device (121, 122) for determining Channel State Information, CSI, estimates to be transmitted in a CSI report for at least one CSI process configured for the wireless device (121, 122) to a network node (110) in a radio communications network (100) is provided The wireless device (121, 122) receives a message comprising an indication to discard existing CSI estimates and/or an indication to use CSI estimates corresponding to a determined period of time In response to said message, the wireless device (121, 122) determines CSI estimates to be used in the CSI report to the network node (110) according to the received indication A wireless device (121, 122) is also described Furthermore, a network node (110) and method therein for controlling CSI estimates transmitted by one or more wireless devices (121, 122) in CSI reports of at least one CSI process configured for the one or more wireless devices (121, 122) to the network node (110) in a radio communications network (100) are also provided

A wireless device, a network node and methods therein for reporting channel state information (csi) in a radio communications network

The invention relates to a method for scheduling resources for uplink transmissions in a radio access network comprising access points which own pre-assigned resources. The invention also relates to an access point (5-7), a user terminal (1-4) and an access point controller 8. Characteristic features of the invention are that each AP places its resources to the disposition of other APs in the access network, and that an AP (7) transmits a blocking signal (BLOCK R3) if it does not allow a UT (3) , which is served by an AP (5) in another cell, to use its resources (R3). A UT that detects a blocking signal from an AP that owns the resources on which the UT is transmitting immediately stops transmission on said resources. The signal quality of a detected blocking signal may be used for setting the transmission power on the resources the UT has borrowed from the AP which transmits the blocking signal. Based on statistics on the APs which transmit blocking signals long-term pre-allocation of resources among the APs is made.

Resource scheduling in a cellular system

Joint communication and sensing is emerging as a potential extension to the existing wireless communication systems. In this paper, we present an overview of sensing using a primarily wireless communication network and investigate different design aspects such as hardware implications, spectrum requirements and multiplexing of communication and sensing signals. Also, we present sensing signal design based on the required sensing accuracies for an OFDM-based communication system and show the corresponding detection performance. One interesting finding is the large difference between transmission power of sensing compared to transmission power used for communication. We will discuss how this impacts the design, including duplex direction as well as waveform that is used for sensing. Finally, we discuss some tradeoffs between sensing accuracy and the overhead of sensing signal and solutions to reduce the overhead in a joint communication and sensing system.

Introducing sensing into future wireless communication systems

Methods and arrangements for resource allocation in a telecommunication system in which aggregation of component carriers is applied. The size of the resource allocation field is determined based on the transmission bandwidth of a selection of component carriers. The selection of component carriers comprises the component carrier on which the resource allocation message is monitored and the component carriers which are cross-scheduled from said component carrier. The resource allocation message comprising the resource allocation field with the determined size is transmitted to the user equipment over a particular component carrier of the selection of component carriers. Furthermore, with only one size of the resource allocation field a smaller number of code word sizes needs to be monitored by the UE. This leads to a smaller number of blind decodings performed in the UE. The present invention enables a more tailored approach when determining the size of the resource allocation field to avoid too high overhead but also a too coarse resource allocation.

Stefan Parkvall

Papers

Arrangement And Method In A Mobile Communication Network

A wireless device, a network node and methods therein for reporting channel state information (csi) in a radio communications network

Resource scheduling in a cellular system

Introducing sensing into future wireless communication systems

Compromise resource allocation field size when aggregating component carriers of differing size