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 chapter provides an overview of the System Architecture Evolution (SAE) work in 3GPP and explores the core network used by WCDMA/ High-Speed Packet Access (HSPA)The chapter describes the system architecture of WCDMA/HSPA and Long-Term Evolution (LTE), their connections, similarities, and differences. The term system architecture describes the allocation of necessary functions to logical nodes and the required interfaces between the nodes. The system architecture is divided into a radio-access network (RAN) part and a core-network part. The chapter discusses the functional split between radio access network and core network. For WCDMA/HSPA, the philosophy behind the functional split is to keep the core network unaware of the radio access technology and its layout. This means that the RAN should be in control of all functionality optimizing the radio interface and that the cells should be hidden from the core network. As a consequence, the core network can be used for any radio access technology that adopts the same functional split.

System Architecture Evolution

The present disclosure describes example techniques for configuring and utilizing common control channels and configuration thereof in wireless communication systems For instance, in an aspect, the present disclosure describes an example method performed by a network node (106) (also referred to herein as a base station, eNB, next-generation NodeB (gNB), or the like) that includes generating resource location information identifying one or more candidate time-frequency resource locations for a common control channel utilized in the cell In addition, the example method can include transmitting the resource location information to one or more UEs and/or one or more other network nodes

Common PDCCH Configuration

Limited uplink bandwidth radio network devices (30) are supported on wide bandwidth uplink carriers by configuring and controlling the use of multiple control regions within the uplink carrier bandwidth. In some embodiments, the total bandwidth of the uplink carrier is divided into a plurality of sub-band portions, wherein at least one sub-band portion includes at least one control region nominally dedicated to the transmission of uplink control signaling. The control regions may be configured at one or both edges of sub-band portions, or elsewhere within a sub-band portions. Sub-band portions may share a control region. Radio network devices (30) are configured with a specified portion of the uplink carrier bandwidth for use for uplink transmission, which includes at least one control region. The specified portion may comprise an integer number of sub-band portions, or may span only part of one or more sub-band portions. Radio network devices (30) may be dynamically configured to allow or suppress data signaling in control regions.

Uplink transmission bandwidth control and support

There is disclosed a method of operating a network node in a radio access network, the method includes transmitting a resource allocation message comprising a bit field, the resource allocation message being transmitted for reception in a common search space to which a first bandwidth part with a first unit size of resource allocation is associated. The bit field allocates resources in a second bandwidth part with a second unit size of resource allocation. The disclosure also pertains to related devices and methods.

Efficient control signaling using common search space

In the past, cellular systems have mostly focused on transmission of data intended for a single user and not on broadcast services. Traditional broadcast networks, exemplified by the radio and TV broadcasting networks, have on the other hand focused on covering very large areas and have offered no or limited possibilities for transmission of data intended for a single user. Multimedia Broadcast and Multicast Services (MBMS), introduced for WCDMA in release 6, supports multicast/broadcast services in a cellular system, thereby combining multicast and unicast transmissions within a single network. With MBMS, the same content is transmitted to multiple users located in a specific area, the MBMS service area , in a unidirectional fashion. The MBMS service area typically covers multiple cells, although it can be made as small as a single cell. In this chapter, the principles behind MBMS in the radio access network and their introduction into WCDMA are discussed.

Stefan Parkvall

Papers

System Architecture Evolution

Common PDCCH Configuration

Uplink transmission bandwidth control and support

Efficient control signaling using common search space

Multimedia broadcast multicast services