ZTE Communications

The whole issue of ZTE Communications September 2011, Vol. 9 No. 3

2011, 9(3): 0.

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Guest Editorial: Advances in Digital Front-End and Software RF Processing: Part I

Jun Fang, Fa-Long Luo, Mikko Valkama, Serioja Ovidiu Tatu and Tomohisa Wada

2011, 9(3): 1-2.

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Adaptation of a Digitally Predistorted RF Amplifier Using Selective Sampling

R. Neil Braithwaite

2011, 9(3): 3-12.

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In this paper, a reduced-cost method of measuring residual nonlinearities in an adaptive digitally predistorted amplifier is proposed. Measurements obtained by selective sampling of the amplifier output are integrated over the input envelope range to adapt a fourth-order polynomial predistorter with memory correction. Results for a WCDMA input with a 101 carrier configuration show that a transmitter using the proposed method can meet the adjacent channel leakage ratio (ACLR) specification. Inverse modeling of the nonlinearity is proposed as a future extension that will reduce the cost of the system further.

A New Two-Branch Amplification Architecture and its Application with Various Modulated Signals

W. Hamdane, A. B. Kouki, and F. Gagnon

2011, 9(3): 13-21.

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This paper proposes a new two-branch amplification architecture that combines baseband signal decomposition with RF front-end optimization. In the proposed architecture, the filtered modulated signals are separated into two components that are then amplified independently and combined to regenerate an amplified version of the original signal. A branch with an efficient amplifier transmits a low-varying envelope signal that contains the main part of the information. Another branch amplifies the residual portion of the signal. The baseband decomposition and parameters of the RF part are optimized to find the configuration that gives the best power efficiency and linearity. For M-ary quadrature amplitude modulation (M-QAM) signals, this technique is limited in terms of power efficiency. However, for filtered continuous phase modulation (CPM) signals, especially for minimum shift keying (MSK) and Gaussian MSK (GMSK) signals, high power efficiency can be achieved with no significant impact on the overall linearity. The results show that this technique gives better performance than the single-ended class-B amplifier.

FPGA Implementation of a Power Amplifier Linearizer for an ETSI-SDR OFDM Transmitter

Suranjana Julius and Anh Dinh

2011, 9(3): 22-27.

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Most satellite digital radio (SDR) systems use orthogonal frequency-division multiplexing (OFDM) transmission, which means that variable envelope signals are distorted by the RF power amplifier (PA). It is customary to back off the input power to the PA to avoid the PA nonlinear region of operation. In this way, linearity can be achieved at the cost of power efficiency. Another attractive option is to use a linearizer, which compensates for the nonlinear effects of the PA. In this paper, an OFDM transmitter conforming to European Telecommunications Standard Institute SDR Technical Specifications 2007-2008 was designed and implemented on a low-cost field-programmable gate array (FPGA) platform. A weakly nonlinear PA, operating in the L-band SDR frequency, was used for signal transmission. An adaptive linearizer was designed and implemented on the same FPGA device using digital predistortion to correct the undesired effects of the PA on the transmitted signal. Test results show that spectral distortion can be suppressed between 6-9 dB using the designed linearizer when the PA is driven close to its saturation region.

Design Technologies for Silicon-Based High-Efficiency RF Power Amplifiers: A Brief Overview

Ruili Wu, Jerry Lopez, Yan Li and Donald Y.C. Lie

2011, 9(3): 28-35.

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This paper presents a brief overview of several promising design technologies for high efficiency silicon-based radio frequency (RF) power amplifiers (PAs) as well as the use of these technologies in mobile broadband wireless communications. Four important aspects of PA design are addressed in this paper. First, we look at class-E PA design equations and provide an example of a class-E PA that achieves efficiency of 65-70% at 2.4 GHz. Then, we discuss state-of-the-art envelope tracking (ET) design for monolithic wideband RF mobile transmitter applications. A brief overview of Doherty PA design for the next-generation wireless handset applications is then given. Towards the end of the paper, we discuss an inherently broadband and highly efficient class-J PA design targeting future multi-band multi-standard wireless communication protocols.

Multi-Gbit/s 60 GHz Transceiver Analysis Using FDM Architecture and Six-Port Circuit

Nazih Khaddaj Mallat, Emilia Moldovan, Serioja O. Tatu, and Ke Wu

2011, 9(3): 36-41.

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This paper presents an analysis and validation by advanced system simulation of compact and low-cost six-port transceivers for future wireless local area networks (WLANs) operating at millimeter-wave frequencies. To obtain realistic simulation results, a six-port model based on the measurement results of a fabricated V-band hybrid coupler, the core component, is used. A frequency-division multiplexing scheme is used by introducing four quadrature phase-shift keying (QPSK) channels in the wireless communication link. The data rate achieved is about 4 Gbit/s. The operating frequency is in the 60-64 GHz unlicensed band. Bit error rate (BER) results are presented, and a comparison is made between single-carrier and multicarrier architectures. The proposed wireless system can be considered an efficient candidate for millimeter-wave communication systems operating at quasi-optical data rates.

Millimeter-Wave Heterodyne Six-Port Receiver: New Implementation and Demodulation Results

D. Hammou, E. Moldovan, and S.O. Tatu

2011, 9(3): 42-48.

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This paper presents a new implementation of a millimeter-wave heterodyne receiver based on six-port technology. The six-port model is implemented in Advanced Design System (ADS) using S-parameter measurements for realistic advanced simulation of a short-range 60 GHz wireless link. Millimeter-wave frequency conversion is performed using a six-port down-converter. The second frequency conversion is performed using conventional means because of low IF. A comparison between the proposed receiver and a conventional balanced millimeter-wave mixer shows that the proposed receiver improves conversion loss and I/Q phase stability over the local oscillator (LO) and RF power ranges. The results of demodulating a V-band quadrature phase-shift keying (QPSK) signal at a high data rate of 100 Mb/s-1 Gb/s are discussed. The results of a bit error rate (BER) and error vector magnitude (EVM) analysis prove that the proposed architecture can be successfully used for wireless link transmission up to 10 m.

Security Service Technology for Mobile Networks

Aiqun Hu, Tao Li, and Mingfu Xue

2011, 9(3): 49-54.

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As mobile networks become high speed and attain an all-IP structure, more services are possible. This brings about many new security requirements that traditional security programs cannot handle. This paper analyzes security threats and the needs of 3G/4G mobile networks, and then proposes a novel protection scheme for them based on their whole structure. In this scheme, a trusted computing environment is constructed on the mobile terminal side by combining software validity verification with access control. At the security management center, security services such as validity verification and integrity check are provided to mobile terminals. In this way, terminals and the network as a whole are secured to a much greater extent. This paper also highlights problems to be addressed in future research and development.

Research on LTE Network Coverage Planning

Jun Gu and Ren Sheng

2011, 9(3): 55-58.

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When deploying an LTE network, coverage planning is critical to reduce construction costs and ensure network quality. This paper considers actual network planning requirements and combines theory with simulation analysis to study LTE wireless access link and network characteristics. A theory for LTE cellular coverage planning and application methods is proposed that lays the basic foundation for LTE cellular networks.

Cloud Computing in Mobile Communication Networks

Xinzhi Ouyang

2011, 9(3): 59-62.

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Cloud computing makes computing power universally available and provides flexibility in resource acquisition. It allows for scalable provision of services and more reasonable use of resources. This article considers cloud service deployment and virtualization from the perspective of mobile operators. A solution is proposed that allows mobile operators to maximize profits with minimal investment.

The Internet of Things and Ubiquitous Intelligence (3)

Dongliang Xie and Yan Shi

2011, 9(3): 63-65.

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