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

Apparatus and method for identifying pucch format 3 resources

FIELD: wireless communication equipment.SUBSTANCE: invention relates to wireless communication and can be used to transmit control information. Control unit comprises a transmitter for communication with at least one receiving unit, herewith the connection is structured in frames containing multiple subframes, and a controller configured able to control the transmitter for transmitting the control channel within the area of search only in a subset of one of the subframes, herewith the search area includes a configurable time range, and a subset of subframes, wherein the control channel is transmitted, is indicated by a bitmap.EFFECT: higher efficiency of transmission, including due to energy saving of the power supply source.20 cl, 10 dwg

Monitoring control channel basing on search area

A method and apparatus according to the present invention addresses and/or prevents lost protocol synchronization in HARQ systems caused by ACK/NACK errors. One embodiment detects lost synchronization errors for NDI-based retransmission protocols and restores synchronization by sending an explicit RESET message. In response to the RESET message, the transmitter aborts the transmission of a current PDU and transmits a new PDU and corresponding NDI. Another embodiment prevents protocol synchronization errors by sending scheduling grants on a packet by packet basis. The receiver sends a subsequent explicit scheduling grant to the transmitter based on an error evaluation of a received PDU. The transmitter will not send the next PDU unless it receives the subsequent explicit scheduling grant.

Improved protocol synchronization for harq

This chapter provides an overview of LTE and its evolution. The most important technology components of LTE release 8—including transmission schemes, scheduling, multi-antenna support, and spectrum flexibility—as well as the additional features and enhancements (e.g., carrier aggregation, relaying, license-assisted access, enhancements for machine-type communication, and direct device-to-device communication) introduced in later releases up to and including release 13 are presented. The chapter can either be read on its own to get a high-level overview of LTE, or as an introduction to the subsequent chapters.

Chapter 3 – LTE Radio Access: An Overview

Publisher Summary
This chapter introduces computer simulation of mobile systems as a powerful tool to assess the system performance. One of the main advantages of computer simulations is that evaluation can be made of system concepts that are not deployed or still under development. There is full control of the environment, including propagation parameters, traffic, system layout, etc., and full traceability of all parameters affecting the result. Well-controlled “experiments” comparing similar system concepts or parts of concepts can be done under repeatable conditions. A very good picture of system performance can be obtained with computer simulations, and it can often be used to find the potential limits for performance. The simulation results presented in this chapter demonstrate the high potential of LTE/LTE-Advanced in terms of both overall spectral efficiency to the benefit of operators and high cell-edge performance to the benefit of the end-user. The performance is assessed in four different test environments. The results for FDD and TDD in downlink and uplink all exceed the requirements set up by ITU-R for the evaluation of IMT-Advanced candidates. In addition, the peak radio-interface data rates and the latency achieved by LTE meet the ITU-R requirements.

Stefan Parkvall

Papers

Apparatus and method for identifying pucch format 3 resources

Monitoring control channel basing on search area

Improved protocol synchronization for harq

Chapter 3 – LTE Radio Access: An Overview

Chapter 18 – Performance