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

This paper surveys recent advances in the area of very large MIMO systems. 
With very large MIMO, we think of systems that use antenna arrays with an order of magnitude more elements than in systems being built today, say a hundred antennas or more. Very large MIMO entails an unprecedented number of antennas simultaneously serving a much smaller number of terminals. The disparity in number emerges as a desirable operating condition and a practical one as well. The number of terminals that can be simultaneously served is limited, not by the number of antennas, but rather by our inability to acquire channel-state information for an unlimited number of terminals. Larger numbers of terminals can always be accommodated by combining very large MIMO technology with conventional time- and frequency-division multiplexing via OFDM. Very large MIMO arrays is a new research field both in communication theory, propagation, and electronics and represents a paradigm shift in the way of thinking both with regards to theory, systems and implementation. The ultimate vision of very large MIMO systems is that the antenna array would consist of small active antenna units, plugged into an (optical) fieldbus.

/pdf/scaling-up-mimo-opportunities-and-challenges-with-very-large-1gai688763.pdf

Scaling up MIMO: Opportunities and Challenges with Very Large Arrays

Cloud Radio Access Network (C-RAN) is a novel mobile network architecture which can address a number of challenges the operators face while trying to support growing end-user's needs. The main idea behind C-RAN is to pool the Baseband Units (BBUs) from multiple base stations into centralized BBU Pool for statistical multiplexing gain, while shifting the burden to the high-speed wireline transmission of In-phase and Quadrature (IQ) data. C-RAN enables energy efficient network operation and possible cost savings on baseband resources. Furthermore, it improves network capacity by performing load balancing and cooperative processing of signals originating from several base stations. This paper surveys the state-of-the-art literature on C-RAN. It can serve as a starting point for anyone willing to understand C-RAN architecture and advance the research on C-RAN.

/pdf/cloud-ran-for-mobile-networks-a-technology-overview-1t5y44pa7z.pdf

Cloud RAN for Mobile Networks—A Technology Overview

Future generation cellular networks are expected to provide ubiquitous broadband access to a continuously growing number of mobile users. In this context, LTE systems represent an important milestone towards the so called 4G cellular networks. A key feature of LTE is the adoption of advanced Radio Resource Management procedures in order to increase the system performance up to the Shannon limit. Packet scheduling mechanisms, in particular, play a fundamental role, because they are responsible for choosing, with fine time and frequency resolutions, how to distribute radio resources among different stations, taking into account channel condition and QoS requirements. This goal should be accomplished by providing, at the same time, an optimal trade-off between spectral efficiency and fairness. In this context, this paper provides an overview on the key issues that arise in the design of a resource allocation algorithm for LTE networks. It is intended for a wide range of readers as it covers the topic from basics to advanced aspects. The downlink channel under frequency division duplex configuration is considered as object of our study, but most of the considerations are valid for other configurations as well. Moreover, a survey on the most recent techniques is reported, including a classification of the different approaches presented in literature. Performance comparisons of the most well-known schemes, with particular focus on QoS provisioning capabilities, are also provided for complementing the described concepts. Thus, this survey would be useful for readers interested in learning the basic concepts before going into the details of a particular scheduling strategy, as well as for researchers aiming at deepening more specific aspects.

/pdf/downlink-packet-scheduling-in-lte-cellular-networks-key-1z27kezket.pdf

Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey

This very up-to-date and practical book, written by engineers working closely in 3GPP, gives insight into the newest technologies and standards adopted by 3GPP, with detailed explanations of the specific solutions chosen and their implementation in HSPA and LTE. The key technologies presented include multi-carrier transmission, advanced single-carrier transmission, advanced receivers, OFDM, MIMO and adaptive antenna solutions, advanced radio resource management and protocols, and different radio network architectures. Their role and use in the context of mobile broadband access in general is explained. Both a high-level overview and more detailed step-by-step explanations of HSPA and LTE implementation are given. An overview of other related systems such as TD SCDMA, CDMA2000, and WIMAX is also provided.This is a 'must-have' resource for engineers and other professionals working with cellular or wireless broadband technologies who need to know how to utilize the new technology to stay ahead of the competition.The authors of the book all work at Ericsson Research and are deeply involved in 3G development and standardisation since the early days of 3G research. They are leading experts in the field and are today still actively contributing to the standardisation of both HSPA and LTE within 3GPP. * Gives the first explanation of the radio access technologies and key international standards for moving to the next stage of 3G evolution: fully operational mobile broadband* Describes the new technologies selected by the 3GPP to realise High Speed Packet Access (HSPA) and Long Term Evolution (LTE) for mobile broadband * Gives both higher-level overviews and detailed explanations of HSPA and LTE as specified by 3GPP

3G Evolution : HSPA and LTE for Mobile Broadband

Reflecting the recent completion of LTEs specification, the new edition of this bestseller has been fully updated to provide a complete picture of the LTE system. The latest LTE standards are included on the radio interface architecture, the physical layer, access procedures, MBMS, together with three brand new chapters on LTE Transmission Procedures, Flexible Bandwidth in LTE and LTE evolution into IMT-Advanced. Key technologies presented include multi-carrier transmission, advanced single-carrier transmission, advanced receivers, OFDM, MIMO and adaptive antenna solutions, advanced radio resource management and protocols, and different radio network architectures. Their role and use in the context of mobile broadband access in general is explained. Both a high-level overview and more detailed step-by-step explanations of HSPA and LTE implementation are given. An overview of other related systems such as TD SCDMA, CDMA2000, and WiMAX is also provided.The new edition has up-to-date coverage of the recently published LTE Release 8 radio-access standard, giving the reader insight into the ongoing and future process of LTE and LTE-Advanced standardisation. Coverage on LTE in this edition includes (an extra 160 pages): Easy-to-access overview of the LTE protocol layers Complete description of LTE physical layer including reference signals, control signalling, multi-antenna transmission schemes Covers both FDD and TDD, their fundamental difference and their impact on the LTE design Detailed description of access procedures including cell search, random access, broadcast of system information Transmission procedures, including retransmission protocols, scheduling, uplink power control Evolution towards IMT-Advanced ("4G") This book is a must-have resource for engineers and other professionals in the telecommunications industry, working with cellular or wireless broadband technologies, giving an understanding of how to utilize the new technology in order to stay ahead of the competition.The authors of the book all work at Ericsson Research and are deeply involved in 3G development and standardisation since the early days of 3G research. They are leading experts in the field and are today still actively contributing to the standardisation of both HSPA and LTE within 3GPP.* Includes details of the standards and technologies (160 new pages): LTE radio interface architecture, LTE physical layer and LTE access procedures* Contains three brand new chapters on LTE: Transmission Procedures, Flexible Bandwidth and LTE Evolution and expanded details on the physical layer (total LTE content is 270 pages)* Examines the latest developments in the evolution of LTE into IMT-Advanced, the next stage of 3G Evolution* Gives clear explanations of the role of OFDM and MIMO technologies in HSPA and LTE* Outlines the System Architecture Evolution (SAE) supporting LTE and HSPA evolution

3G Evolution, Second Edition: HSPA and LTE for Mobile Broadband

The first step of evolving WCDMA towards higher data rates is discussed. It is shown how techniques such as fast link adaptation, fast hybrid ARQ and fast scheduling, among others, can be applied to WCDMA, leading to increased throughput, lower delays, and downlink peak rates in the order of 10 Mbit/s. Through system simulations, the packet-data performance of such an evolved WCDMA system is illustrated.

The evolution of WCDMA towards higher speed downlink packet data access

The first step of evolving WCDMA towards higher data rates through the introduction of HSDPA is discussed. By applying fast link adaptation together with higher order modulation, fast hybrid ARQ and fast scheduling, the best-effort packet data support of WCDMA can be improved in terms of increased throughput, lower delays and increased peak data rates. Simulations illustrate the potential of the concept.

The high speed packet data evolution of WCDMA

In spread spectrum communications, a method for allocating and re-allocating channelization codes to new and existing channels in a way that makes the maximum number of codes available at a given time for channels of different rates and different spreading factors. If re-allocations are not performed, a communication system employing the invention has a higher capacity than a system employing a random allocation strategy. The invention also reduces signaling overhead for re-allocations in comparison to a random allocation strategy because fewer re-allocations are necessary.

Per Beming

Papers

3G Evolution : HSPA and LTE for Mobile Broadband

3G Evolution, Second Edition: HSPA and LTE for Mobile Broadband

The evolution of WCDMA towards higher speed downlink packet data access

The high speed packet data evolution of WCDMA

Code allocation in CDMA