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

There is disclosed a method of operating a user equipment in a radio access network. The method includes transmitting control information utilizing a control information format, the control information format being selected from a plurality of different control information formats based on a format indication. The disclosure also pertains to related devices and methods.

Feedback signaling format selection

The invention relates to a method and arrangement for transmitting and receiving control information in a radio-access network. A network node (100)transmits first control information in a first part (300) and second control information in a second part (302)of a time-frequency region (305) that is transmitted after a control region (200) in a subframe (310). The second part (302) is located later in the subframe (310) than the first part 300. The second control information may be less time-critical than the first control information. An intermediate node (103) receives and decodes the first control information at the end (320) of the first part. When the first control information indicates that the subframe (310) comprises data payload to the intermediate node(103), the intermediate node (103) receives and decodes the data payload. The intermediate node (103) receives second control information at the end(330) of the second part.

Control information assigning method

Methods, network device and terminal device are disclosed time advance adjustment. A method comprises receiving a time advance, TA, command from a network device; determining a TA granularity or range; and determining a TA value based at least partly on the TA command and the TA granularity or range, wherein different numerologies are configured for at least two carriers and/or at least two bandwidth parts (BWPs) in one carrier, wherein the at least two carriers and/or the at least two BWPs serve the terminal device and/or the terminal device supports at least one numerology.

Method, terminal device and network device for time advance adjustment

A system and a method for wireless linking in a cellular communication system are disclosed such that a mobile station is maintained in simultaneous communication with at least a first node and a second node for access to the cellular communication system. Information going to and from the first node is not identical to the information going to and from the second node. In one embodiment the second node, or secondary access point is a relay node forwarding received information to and from the first node, or primary access point. In another embodiment the second node is another mobile station performing a direct mobile-to-mobile communication (MS-to-­MS). In still an embodiment a first wireless link to the first node is for control information only. In still a further embodiment a second wireless link to the second node is only for communication of information from the mobile station or only for communication of information to the mobile station.

Provision of a continous wireless connection using a mobile station as relay

There is provided mechanisms for handling client network nodes backhauled by a hub network node. The hub network node acquires a need for backhaul re-configuration of a client network node being backhauled by the hub network node. The hub network node provides an indication to the client network node that a user equipment served by the client network node is to be handed over. The hub network node receives a report that the client network node has handed over the user equipment. The hub network node transmits at least one of synchronization and reference signals enabling client network nodes to search for the hub network node.

Stefan Parkvall

Papers

Feedback signaling format selection

Control information assigning method

Method, terminal device and network device for time advance adjustment

Provision of a continous wireless connection using a mobile station as relay

Backhaul of Client Network Nodes