Implementable wireless access for B3G networks. I. MIMO mimo channel measurement, analysis, and modeling [Topics in Radio Communications]

Within Mobile VCE, a team of several leading U.K. universities, in dose association with major manufacturers and international telecom operators from the mobile industry, have been addressing the challenging task of designing transceiver structures for beyond 3G networks. Innovative approaches led to a plethora of cross-layer optimized technologies of low complexity and high robustness, allowing for the much promised multimedia-centric services over future wireless networks. This article presents a comprehensive overview of the research conducted within Mobile VCE's Core Wireless Access Research Programme, a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article, the first of four, MIMO channel measurements, analysis, and modeling are presented, which were then utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aimed at securing major improvements in delivery efficiency in future wireless systems through cross-layer operation     

Channel-adaptive wideband wireless video telephony

The fundamental advantage of burst-by-burst (BbB) adaptive intelligent multimode multimedia transceivers (IMMTs) is that-irrespective of the propagation environment encountered-when the mobile roams across different environments subject to path loss; shadow- and fast-fading; co-channel-, intersymbol-, and multiuser interference, while experiencing power control errors, the system will always be able to configure itself in the highest possible throughput mode, while maintaining the required transmission integrity. Finding a specific solution to a distributive or interactive video communications problem has to be based on a compromise in terms of the inherently contradictory constraints of video quality, bit rate, delay, robustness against channel errors, and the associated implementational complexity. Considering some of these tradeoffs and proposing a range of attractive solutions to various video communications problems is the basic aim of this overview. The article portrays a range of proprietary video codecs and compares them to some of the existing standard video codecs. A number of multimode video transceivers are also characterized. Systems employing the standard H.263 video codec in the context of wideband BbB adaptive video transceivers are examined, and the concept of BbB-adaptive video transceivers is then extended to CDMA-based systems     

三维粗糙面上的MIMO信道模型

多天线构成的多输入多输出MIMO（Multiple-Input Multiple-Output）信道是B3G/4G系统的关键技术之一。文章建立下垫三维粗糙面的MIMO信道模型,用基尔霍夫（KA,Kirchhoff approximation）近似随机粗糙面散射的数值计算方法研究下垫粗糙面产生的随机多路径传输对MIMO信道矩阵的影响,并数值地讨论接收、发射天线阵列位置以及下垫粗糙面几何参数对MIMO系统信道容量的影响。结果表明,双站距离大、天线高度低时,下垫随机粗糙面对MIMO信道容量的影响显著。当天线阵元间距小时,下垫粗糙面将显著增大MIMO系统信道容量;当天线间距大时,粗糙面减小MIMO系统信道容量。     

A novel multi-antenna impulse radio UWB transceiver for broadband high-throughput 4G WLANs

In the last years, a lot of attention has been devoted to both multi-antenna systems with space-time orthogonal block coding (STOBC) and ultra wideband (UWB) transceivers based on impulse-radio (IR) technologies. In this short contribution we anticipate the architecture of a novel transceiver merging both multi-antenna and pulse position modulation (PPM) IR-UWB techniques and then we test the performance in flat-faded application scenarios typical of emerging broadband 4G WLANs. Three main appealing features are retained by the sketched transceiver scheme. First, it allows to equip the UWB receiver with reliable estimates of the (possibly time-varying) underlying multiple-input multiple-output (MIMO) UWB without reducing the overall information throughput conveyed by the system. Second, the performance confirms that the proposed transceiver is able to achieve "full diversity" even at SNRs as low as 1.5-2 dB. As a consequence, the resulting BERs outperform those of current Single-Input Single-Output (SISO) IR-UWB transceivers over two orders of magnitude even at SNR's as low as 3-4 dB. Third, at target BER's below 10/sup -2/ and radiated powers around 250 /spl mu/W, the coverage ranges allowed by the proposed MIMO IR-UWB scheme typically outperform those of conventional SISO IR-UWB ones of about two orders of magnitude.     

TDD-CDMA for the 4th generation of wireless communications

This article discusses an evolutionary TDD mode of CDMA-based path for 3.5G/4G systems. This technology has already been the basis of two 3G standards: TD-CDMA and TD-SCDMA with a synchronous uplink. Several techniques have been developed that allow TDD-CDMA-based systems to transmit at rates usually associated with 3.5G to 4G, up to 10-20 Mbit/s with wide area coverage. The present TDD-CDMA-based 3G standards are evolving to provide these higher rates, while fully retaining the coverage and mobility associated with, and expected from, the present mobile communications systems. This article discusses how TDD-CDMA specific techniques facilitate delivering services at data rates associated with 3.5G and 4G. We review how TDD-CDMA can provide for asymmetric uplink and downlink transmissions, facilitate deployment of advanced antennas for improved downlink coverage, and enable provision of advanced receiver techniques in base stations and mobiles. We also discuss how these techniques affect systems capacity in full packet-switched IP-based systems. We then discuss 4G TDD CDMA systems: those with different modulation techniques for uplink and downlink communications. These are generally based on a multicarrier mode of CDMA, and may incorporate OFDM technique.     

MIMO系统自适应均衡技术进展与展望

随着3G，B3G／4G通信技术的发展，均衡技术在MIMO通信系统的应用越来越受到关注。本文分类总结了MIMO系统均衡的LMS，RLS，CMA等常用及其改进算法，介绍了线性、格型、判决反馈（DFE）、Turbo等类型均衡器。研究了国内外MIMO均衡领域的发展现状，指出了其困难所在，并对未来的研究重点及其方向进行了展望。     

Improved AGC method for B3G MIMO-OFDM system

Automatic gain control (AGC) has an important role in multi-input multi-output-orthogonal frequency-division multiplexing (MIMO-OFDM) system, especially, when receiving antennas are distributed.In recent years, much work has been done on efficiency and simplification of AGC, but few of them are aiming at multiple antennas.This article, on the assumption of ideal AGC for single receiving antenna, analyzes feasible AGC methods for MIMO system from a new aspect, then brings forward three applicable AGC methods separate automatic gain control, joint automatic gain control, and partly-joint automatic gain control (PJ-AGC).After simulation, when parameters are properly set, PJ-AGC has the best performance and can be applied to B3G MIMO-OFDM system.     

Transceiver design for MIMO wireless systems incorporating hybrid ARQ

Hybrid ARQ, an extension of ARQ that incorporates forward error correction coding, is a retransmission scheme employed in current communications systems. The use of HARQ can contribute to efficient utilization of the available resources and the provision of reliable services in latest-generation systems. This article focuses on wireless systems using HARQ with emphasis on the multiple-input multiple-output paradigm. MIMO-HARQ offers new opportunities because of the additional degrees of freedom introduced by the multiple antennas at the transmitter and receiver. The architecture of MIMO transceivers that are based on bit-interleaved coded modulation and employ HARQ is described. Additionally, receiver implementations are presented and compared in terms of complexity, memory requirements, and performance.     

Radio resource allocation in third generation mobile communicationsystems

Code-division multiple access has been widely accepted as the major multiple access scheme in third-generation mobile communication systems. Wide-band CDMA and its hybrid associate time-division CDMA are key elements of the IMT2000 framework of standards. Since the beginning of the 1990s there has been enormous research activity in analysis of the soft (i.e., interference limited) capacity of these CDMA-based systems. Optimal usage of the soft capacity to provide, maintain, and guarantee QoS for different service classes is now becoming a very important issue. Therefore, interest in radio resource allocation has recently. This article presents an overview of RRA schemes (primarily for CDMA-based systems) that are flexible, support traffic services with various QoS requirements, minimize call/session blocking and dropping probabilities, and have acceptable radio resource utilization     

Convex primal decomposition for multicarrier linear MIMO transceivers

The design of linear transceivers for multiple-input-multiple-output (MIMO) communication systems with channel state information is particularly challenging for two main reasons. First, since several substreams are established through the MIMO channel, it is not even clear how the quality of the system should be measured. Second, once a cost function has been chosen to measure the quality, the optimization of the system according to such criterion is generally difficult due to the nonconvexity of the problem. Recent results have solved the problem for the wide family of Schur-concave/convex functions, resulting in simple closed-form solutions when the system is modeled as a single MIMO channel. However, with several MIMO channels (such as in multi-antenna multicarrier systems), the solution is generally more involved, leading in some cases to the need to employ general-purpose interior-point methods. This problem is specifically addressed in this paper by combining the closed-form solutions for single MIMO channels with a primal decomposition approach, resulting in a simple and efficient method for multiple MIMO channels. The extension to functions that are not Schur-concave/convex is also briefly considered, relating the present work with a recently proposed method to minimize the average bit error rate (BER) of the system.     

Distributed radio access technology selection for adaptive networks in high‐speed,B3G infrastructures

Wireless systems migrate towards the era of ‘Beyond the 3rd Generation’ (B3G). A fundamental facilitator of this vision is the evolution of high speed, adaptive networks, needed for better handling the offered demand and improving resource utilization. Adaptive networks dynamically select their configuration, in order to optimally adapt to the changing environment requirements and conditions. This paper presents optimization functionality that can be used to support network adaptability (cognition‐reconfigurability) in a B3G context. The paper starts from the business case that justifies the need for placing research onto adaptive networks and then continues with the management functionality for (re)configuration decisions, which is targeted to the dynamic selection of the appropriate radio access technologies (RATs). RAT selection is modelled through an optimization problem called (RAT, Demand and QoS‐Assignment problem—RDQ‐A), the solution of which assigns in a distributed manner the available RATs to adaptive Base Station transceivers and the demand (users) to these transceivers and to QoS levels, respectively. The RDQ‐A optimization problem is decoupled in several sub‐problems and is implemented in phases corresponding to the aforementioned assignments, while efficient custom greedy algorithms are mobilized in each phase for obtaining the optimum assignment. Finally, indicative results from the application of the proposed functionality to a simulated network are presented. Copyright © 2006 John Wiley & Sons, Ltd.     

B3G空中接口技术分析--MIMO信道测量

在多径信道中,使用多天线的MIMO无线系统能够比单天线系统提供更高的信道容量,而信道测量是决定通信性能的一个重要因素。对目前国际范围内现有的MIMO信道测量进行了研究,并做了归纳和分类。此外,对MIMO信道测量方法进行了分析,并给出了一些针对MIMO信道测量系统设计的建议,为B3G空中接口技术研究提供了技术支持。     

Hybrid Beamforming for Massive MIMO Using Rectangular Antenna Array Model in 5G Wireless Networks

Fifth and future generation (5G and B5G) wireless networks aim to serve users with higher data rates and lower latency. Data traffic due to the rapid growth in communication has motivated the study of Multiple Input Multiple Output (MIMO) systems. They utilize multiple antennas in both transmitter and receiver sides. It is necessary to improve the existing technology to achieve fast and reliable communication. In this research work, a rectangular array antenna based hybrid beamforming in a massive MIMO model has been proposed to improve the spectral efficiency of the system. Thus channel capacity with small RF chains is used. To achieve the high signal strength in the main lobe, Chebyshev tapering has been used to suppress the side lobes signals. In this manner, the proposed Hybrid Beamforming for Massive Output MIMO has been realized with a small complexity and higher spectral efficiency. In this research work, the spectral efficiency of both proposed Hybrid and fully-digital beamforming with a different number of RF chains for a various number of antennas at the transmitter, the receiver side has been analyzed. From the simulation results, it has been observed that the proposed rectangular array antenna based Hybrid beamforming in a massive MIMO system reduces the computational complexity up to 99% as compared with conventional fully digital beamforming to achieve the same spectral efficiencies, which is a productive model for 5G wireless networks.

     

Design of compact two-port dual-band dual-polarized MIMO antenna for CBRS and WLAN sub-6-GHz applications

This communication presents a compact field de-correlation lines integrated dual band with dual-polarized (LP & CP) multiple-input multiple-output (MIMO) antenna for the fifth generation (5G) sub-6-GHz wireless communication systems. Dual working bandwidths, smaller interelement gaps, and superior isolation within the MIMO components are the distinguishing characteristics that give the proposed MIMO system an aspect of novelty. The modeled MIMO antenna has compact configurations of 20 × 21 × 0.8 mm³. The unit cell consists of a microstrip feed line with optimized rectangular slots branches etched from the radiated patch. The MIMO module is generated by the antiparallel replication of a single unit cell. To enhance the isolation, two rectangular slots are incorporated on the patch between the unit elements, which act as field de-correlation lines. The MIMO identity is supported by diversity performance calculations in terms of ECC, DG, and TARC. Simulated and measured counterparts are found in the agreement.     

TD-CDM-OFDM: Evolution of TD-SCDMA toward 4G

TD-SCDMA, which is the "homemade" 3G standard in China, has received considerable attention and is believed to play a critical role in the development of China's mobile communication. Meanwhile, advanced MIMO and OFDM techniques shed light on the feasibility of high-performance 4G broadband systems. We discuss an evolutionary path of TD-SCDMA toward 4G systems in this article, which combines the existing advanced traits in TD-SCDMA with new features for broadband wireless communication systems.     

A miniaturized uniplanar MIMO antenna for n79/n46/millimeter-wave applications

This research suggests a compact uniplanar multiple-input multiple-output (MIMO) with four ports for n79/n46/millimeter-wave (mm-wave) applications. The size of the quad MIMO is only 30 × 30 × 0.8 mm³. MIMO system consists of four identical Z-shaped radiators and common ground on the same plane and no decoupling structures are used for isolation. The system covers the bandwidth of 1.9 GHz (4.4–6.3 GHz) with a mid-frequency of 5.6 GHz and also covers the high-band frequencies ranging from 18 to 30 GHz with a bandwidth of 12 GHz. The suggested quad MIMO is fabricated on an FR-4 board, and the measured outcomes are well in line with the simulated results. An isolation value of −11 dB has been achieved for mid-band frequency and −24 dB has been attained for mm-wave bands. Through the value of DG = 10 dB, ECC < 0.07, TARC < −3 dB, MEG < −5 dB, and the ratio of MEG = 1 dB, uniplanar quad MIMO shows acceptable MIMO diversity performance. The entire system was evaluated for the users' hand specific absorption rate (SAR) impacts and is within the limits. After the complete analysis of the miniature quad MIMO antenna, an 8-port, and a 16-port uniplanar MIMO are simulated for smartphone-sized dielectric substrates and the performances were examined. The suggested MIMO system provides an efficient single-layer MIMO antenna to 5G smartphones with high bandwidth and low SAR. The proposed quad MIMO systems are suitable for both the sub-6 GHz band and the mm-wave band.     

THz antennas design,developments, challenges,and applications: A review

Terahertz (0.1–10 THz) wireless communication will be the future technology to reach a top-notch data rate. THz is one of the most promising candidates for 6G systems because it provides enormous bandwidth, up to 100 GHz, and a massive data rate of up to 1 Tbps. THz antennas, antenna arrays, and MIMO antenna arrays in 6G are hot research topics for implementing 6G wireless communication systems. The 6G aims to continue to enhance the features of the 5G as it is capable of achieving the maximum high-speed data rate, excellent reliable communication, massive connectivity, and very low latency connectivity. The 6G requirements need high-gain antenna arrays and MIMO antenna arrays to combat the effect of atmospheric losses in high frequencies. An in-depth discussion of the planar THz antennas that have been extensively used in THz applications like imaging, sensing, and Internet-of-Things (IoT) has been conducted. The study of the THz antennas, antenna arrays, and MIMO antennas on different conducting materials such as copper and graphene, which are designed on different dielectric substrates such as polyimide, quartz, liquid crystalline polymer, and polytetrafluoroethylene, has been carried out in detail. Metamaterial, photoconductive, plasmonic antennas, and THz beamforming are significant parts of THz communications. This paper also provides antennas and antenna arrays based on them.     

Multiuser MIMO OFDM Based TDD/TDMA for Next Generation Wireless Communication Systems

Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency division multiplexing (MIMO OFDM) is an attractive air-interface solution for next-generation wireless local area networks (WLANs), wireless metropolitan area networks (WMANs), and fourth-generation mobile cellular wireless systems. In this paper, one multiuser MIMO OFDM systems with TDD/TDMA was proposed for next-generation wireless mobile communications, i.e., TDD/TDMA 4G, which can avoid or alleviate the specific limitations of existing techniques designed for multiuser MIMO OFDM systems in broadband wireless mobile channel scenarios, i.e., bad performance and extreme complexity of multiuser detectors for rank-deficient multiuser MIMO OFDM systems with CDMA as access modes, extreme challenges of spatial MIMO channel estimators in rank-deficient MIMO OFDM systems, and exponential growth complexity of optimal sub-carrier allocations for OFDMA-based MIMO OFDM systems. Furthermore, inspired from the Steiner channel estimation method in multi-user CDMA uplink wireless channels, we proposed a new design scheme of training sequence in time domain to conduct channel estimation. Training sequences of different transmit antennas can be simply obtained by truncating the circular extension of one basic training sequence, and the pilot matrix assembled by these training sequences is one circular matrix with good reversibility. A novel eigenmode transmission was also given in this paper, and data symbols encoded by space–time codes can be steered to these eigenmodes similar to MIMO wireless communication systems with single-carrier transmission. At the same time,, an improved water-filling scheme was also described for determining the optimal transmit powers for orthogonal eigenmodes. The classical water-filling strategy is firstly adopted to determine the optimal power allocation and correspondent bit numbers for every eigenmode, followed by a residual power reallocation to further determine the additional bit numbers carried by every eigenmode. Compared with classical water-filling schemes, it can also obtain larger throughputs via residual power allocation. At last, three typical implementation schemes of multiuser MIMO OFDM with TDMA, CDMA and OFDMA, i.e., TDD/TDMA 4G, VSF-OFCDM and FuTURE B3G TDD, were tested by numerical simulations. Results indicated that the proposed multiuser MIMO OFDM system schemes with TDD/TDMA, i.e., TDD/TDMA 4G, can achieve comparable system performance and throughputs with low complexity and radio resource overhead to that of DoCoMo MIMO VSF-OFCDM and FuTURE B3G TDD.     

Policies for the reconfiguration of cognitive wireless infrastructures to 3G Radio Access Technologies

The ceaseless evolution of wireless communications is reflected nowadays on the introduction of Beyond-3G (B3G) systems, characterized by the coexistence and cooperation of various Radio Access Technologies (RATs), over a common infrastructure. Major facilitator of this convergence is the advent of cognitive networks, which deploy elements (base stations and mobile terminals) that are able to proactively adapt to environmental stimuli, so that to optimize their performance. Part of the adaptation action takes place in cognitive base stations that own several reconfigurable transceivers, which are controlled by appropriate management functionality and may dynamically change their operating parameters. Each reconfiguration set includes a specific RAT, carrier frequency, as well as demand volume to be allocated per transceiver. Accordingly, proper evaluation of the various candidate reconfiguration sets appears to be of high significance. To this effect, in this paper we consider a cognitive network segment with transceivers operating at 3G RAT/carrier and we solve the DAMC problem (Demand Allocation into Multiple Carriers problem), which aims at evaluating and selecting the optimum policy to allocate the demand into the available 3G carrier frequencies. Optimality is expressed in terms of minimizing the total transmitted/received power per base station, thus deciding for the reconfigurations with the least impact on network interference. Indicative simulation scenarios and results are also presented for the validation and verification of the proposed functionality.