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

For future wireless systems, it is desired to keep network implementation aspects, such as transmission point selection, precoder selection, etc, transparent to the terminal. This means that terminals are envisaged to be unaware of e.g. from which specific network node a transmission is made. This may be referred to as the transparency principle. The proposed solution comprises enabling a receiver to determine a type of antenna association that may be assumed in regard of two blocks of information, based on the result of the decoding of e.g. the first data block. The determination is done in a way such that the principle of transparency is not broken.

Signaling of antenna associations

Switching method and device between open and closed loop multi-stream transmission

PROBLEM TO BE SOLVED: To advantageously maintain synchronism, a current channel structure and a current coding system, and perform autonomous re-transmission for an E-DCH channel.SOLUTION: A user equipment unit is configured for operation with a synchronous HARQ protocol and with capability of sending data on an E-DCH channel either (1) in a nominal mode in single transmission time intervals of a predetermined length, or (2) in an extended mode in a pseudo transmission time interval. The pseudo transmission time interval comprises a first transmission time interval in which the data is transmitted and a second transmission time interval in which the data is re-transmitted. The second transmission time interval is consecutive to the first transmission time interval, and the first transmission time interval and the second transmission time interval are each of the (same) predetermined length.

Method of autonomous transmission for extended coverage

A network node, such as a base station, identifies radio resources within an overall bandwidth using a first resource referencing scheme, while a wireless communication device identifies radio resources within an allocated portion of the overall bandwidth using a second resource referencing scheme. Advantageously, the device correctly identifies given radio resources pointed to by a resource identifier expressed according to the first resource referencing scheme, by translating the resource identifier into the second resource referencing scheme according to mapping information that relates the two schemes. Correspondingly, the network node enables the wireless communication device to perform such translations by providing the mapping information either implicitly or explicitly.

Method and apparatus for identifying and using radio resources in a wireless communication network

FIELD: information technology. ^ SUBSTANCE: transmission facilities on shared downlink cannel are divided into blocks of resources where each block of resources includes predetermined number of subcarriers during predetermined time period. Blocks of resources are subdivided into localised blocks of resources and distributed blocks of resources. User requiring sufficient amount of resources can get multiple above mentioned localised blocks of resources. User who require only small quantity of above mentioned localised blocks of resources can get instead of them multiple submodules of above mentioned distributed blocks of resources. ^ EFFECT: higher transmission channel capacity. ^ 17 cl, 4 dwg

Stefan Parkvall

Papers

Signaling of antenna associations

Switching method and device between open and closed loop multi-stream transmission

Method of autonomous transmission for extended coverage

Method and apparatus for identifying and using radio resources in a wireless communication network

Localised or distributed transmission