Guest editorial for the special issue on software-defined radio transceivers and circuits for 5G wireless communications

Yichuang Sun, Baoyong Chi, and Heng Zhang, Guest Editorial for the Special Issue on Software-Defined Radio Transceivers and Circuits for 5G Wireless Communications, published in IEEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 63 (1): 1-3, January 2016, doi: https://doi.org/10.1109/TCSII.2015.2506979.Peer reviewedFinal Accepted Versio

D/A Resolution Impact on a Poly-phase Multipath Transmitter

In recent publications the Poly-phase multipath technique has been shown to produce a clean output spectrum for a power upconverter (PU) architecture. The technique utilizes frequency independent phase shifts before and after a nonlinear element to cancel out the harmonics and sidebands due to the nonlinearity. A major advantage of this technique is that it circumvents the need to use dedicated RF filters which makes it a potential candidate for cognitive radio transmitters. This paper addresses the requirements on the digital and mixed signal part of such a transmitter. An architecture is proposed based on complex multiplication which can be used to generate the digital multiphase signals required by the multipath technique. Due to equal phase difference of all the paths the same digital hardware could be utilized for carrying out all the phase shifts. When the digital signals pass through a D/A converter which doesn’t have a reconstruction filter, the output in this case would be amplitude discrete like that of a zero order hold. The spectrum of this amplitude discrete signal would have distortion components in it. This can be termed as quantization distortion but now in the context of limited D/A resolution. The multipath technique’s effect on harmonic cancellation, in the presence of such a quantization distortion is explored in this paper. It is shown through simulation that when using ideal phase shifts the multipath technique is able to cancel most of the harmonics produced by an amplitude discrete representation of pure sinusoids. When (upconversion) mixers are used for the second set of phase shifts then with multipath the highest quantization spurs go down with roughly 8db/bit for a single tone and around 10db/bit for two tone inputs

A Comparison of Hybrid Beamforming and Digital Beamforming with Low-Resolution ADCs for Multiple Users and Imperfect CSI

For 5G it will be important to leverage the available millimeter wave spectrum. To achieve an approximately omni- directional coverage with a similar effective antenna aperture compared to state of the art cellular systems, an antenna array is required at both the mobile and basestation. Due to the large bandwidth and inefficient amplifiers available in CMOS for mmWave, the analog front-end of the receiver with a large number of antennas becomes especially power hungry. Two main solutions exist to reduce the power consumption: hybrid beam forming and digital beam forming with low resolution Analog to Digital Converters (ADCs). In this work we compare the spectral and energy efficiency of both systems under practical system constraints. We consider the effects of channel estimation, transmitter impairments and multiple simultaneous users. Our power consumption model considers components reported in literature at 60 GHz. In contrast to many other works we also consider the correlation of the quantization error, and generalize the modeling of it to non-uniform quantizers and different quantizers at each antenna. The result shows that as the SNR gets larger the ADC resolution achieving the optimal energy efficiency gets also larger. The energy efficiency peaks for 5 bit resolution at high SNR, since due to other limiting factors the achievable rate almost saturates at this resolution. We also show that in the multi-user scenario digital beamforming is in any case more energy efficient than hybrid beamforming. In addition we show that if different ADC resolutions are used we can achieve any desired trade-offs between power consumption and rate close to those achieved with only one ADC resolution.Comment: Submitted to JSTSP. arXiv admin note: text overlap with arXiv:1610.0290

High-Speed Communications Over Polymer Optical Fibers for In-Building Cabling and Home Networking

This paper focuses on high-speed cabling using polymer optical fibers (POF) in home networking. In particular, we report about the results obtained in the POF-ALL European Project, which is relevant to the Sixth Framework Program, and after two years of the European Project POF-PLUS, which is relevant to the Seventh Framework Program, focusing on their research activities about the use of poly-metyl-metha-acrilate step-index optical fibers for home applications. In particular, for that which concerns POF-ALL, we will describe eight-level pulse amplitude modulation (8-PAM) and orthogonal frequency-division multiplexing (OFDM) approaches for 100-Mb/s transmission over a target distance of 300 m, while for that which concerns POF-PLUS, we will describe a fully digital and a mixed analog-digital solution, both based on intensity modulation direct detection, for transmitting 1 Gb/s over a target distance of 50 m. The ultimate experimental results from the POF-ALL project will be given, while for POF-PLUS, which is still ongoing, we will only show our most recent preliminary results

A Fully Differential Digital CMOS Pulse UWB Generator

A new fully-digital CMOS pulse generator for impulse-radio Ultra-Wide-Band (UWB) systems is presented. First, the shape of the pulse which best fits the FCC regulation in the 3.1-5 GHz sub-band of the entire 3.1-10.6 GHz UWB bandwidth is derived and approximated using rectangular digital pulses. In particular, the number and width of pulses that approximate an ideal template is found through an ad-hoc optimization methodology. Then a fully differential digital CMOS circuit that synthesizes the pulse sequence is conceived and its functionality demonstrated through post-layout simulations. The results show a very good agreement with the FCC requirements and a low power consumptio

A survey on OFDM-based elastic core optical networking

Orthogonal frequency-division multiplexing (OFDM) is a modulation technology that has been widely adopted in many new and emerging broadband wireless and wireline communication systems. Due to its capability to transmit a high-speed data stream using multiple spectral-overlapped lower-speed subcarriers, OFDM technology offers superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, etc. In recent years, there have been intensive studies on optical OFDM (O-OFDM) transmission technologies, and it is considered a promising technology for future ultra-high-speed optical transmission. Based on O-OFDM technology, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation could be built to support diverse services and the rapid growth of Internet traffic in the future. In this paper, we present a comprehensive survey on OFDM-based elastic optical network technologies, including basic principles of OFDM, O-OFDM technologies, the architectures of OFDM-based elastic core optical networks, and related key enabling technologies. The main advantages and issues of OFDM-based elastic core optical networks that are under research are also discussed

56+ Gb/s serial transmission using duo-binary signaling

In this paper we present duobinary signaling as an alternative for signaling schemes like PAM4 and Ensemble NRZ that are currently being considered as ways to achieve data rates of 56 Gb/s over copper. At the system level, the design includes a custom transceiver ASIC. The transmitter is capable of equalizing 56 Gb/s non-return to zero (NRZ) signals into a duobinary response at the output of the channel. The receiver includes dedicated hardware to decode the duobinary signal. This transceiver is used to demonstrate error-free transmission for different PCB channel lengths including a state-of-the-art Megtron 6 backplane demonstrator