Optimization and Performance of Non-Uniform Rotated Constellations With Multi-RF Transmission Techniques

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We introduce an automatic repeat request (ARQ) scheme that uses nonuniform signal constellations in order to adapt the data rate to the received signal-to-noise ratio (SNR) in a fading channel without using channel state feedback or incremental redundancy. We have defined nonuniform phase shift key (PSK) and quadrature amplitude modulation (QAM) constellations with an arbitrary number of classes of bits. These constellations may also be of interest for further research into unequal error protection. We present simulations of the throughput in Rayleigh fading and lognormal shadowing, and discuss the cases where our proposed scheme may improve the throughput compared to standard ARQ using uniform signal constellations.

The Advanced Television System Committee (ATSC) is currently developing the next-generation U.S. Digital Terrestrial Television (DTT) standard, known as ATSC 3.0. Two disruptive technologies for the physical layer are being evaluated, Layer Division Multiplexing (LDM) and Time Frequency Slicing (TFS). LDM consist in the transmission of a signal composed of two independent signals (layers) which are superimposed together at different power levels. These two layer can be configured with the desired robustness and capacity. LDM enables the efficient provision of services addressed to mobile and fixed reception in a more efficient way than the classical Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) since full bandwidth and transmission time are used in both layers. However, practical operation is restricted due to several implementation constraints such as the use of common parameters and transmitter blocks for both layers (e.g. a common time interleaver). The use of TFS allows for an improved frequency diversity by the distribution of the service data across multiple Radio Frequency (RF) channels instead of using a single RF channel. The paper investigates the potential gains provided by the increased frequency diversity with TFS in conjunction with LDM.

In constellation rearrangement (CoRe), the basestation and the relay use different constellations, with the same modulation level, to communicate with the user terminal. Unlike the existing CoRe techniques, which are restricted to uniform constellations, we propose to use non-uniform quadrature amplitude modulation (QAM) constellations for CoRe. We devise an optimization to find the optimal QAM constellation, which minimizes an upper bound on the symbol error rate (SER). We show how to decompose the optimization problem, which is not convex, into a set of convex optimization problems to solve it. Since the set of non-uniform constellations is a superset of uniform constellations (used in literature), the proposed non-uniform CoRe outperforms all the existing uniform CoRe schemes, with respect to the SER bound. Simulation results show that the proposed non-uniform CoRe scheme yields large gains, with no additional complexity penalty.

Complex field network coding has been shown to achieve a throughput of 1/2 symbol per user per channel use in a multi-way relay channel (MWRC). To achieve this throughput, a superimposed combination of user symbols must be distinguishable at the relay. In [1], precoding vectors were designed for an MWRC with all users employing the same rectangular quadrature amplitude modulation (QAM) constellation. These precoding vectors guarantee that every superimposed combination of user symbols at the relay is distinguishable and a QAM constellation is received. There are many precoding vectors with such properties. In this paper, we consider a more general problem in which each user can employ an arbitrary rectangular QAM constellation and we design a precoding vector for the users such that the power efficiency of the received rectangular QAM constellation at the relay is maximized.

Quadrature amplitude modulation (QAM) constellation and Golay complementary sequences (GCSs) are usually applied in orthogonal frequency division multiplexing (OFDM) systems to obtain a higher data rate and a lower peak-to-mean envelope power ratio (PMEPR). In this paper, after a sufficient search of the literature, it was found that increasing the family size is an effective way to improve the data rate, and the family size is mainly determined by the number of offsets in the general structure of QAM GCSs. Under the guidance of this idea, we propose a new construction for -QAM GCSs through generalized Boolean functions (GBFs) based on a new description of a -QAM constellation, which aims to enlarge the family size of GCSs and obtain a low PMEPR. Furthermore, a previous construction of -QAM GCSs presented by Li has been proved to be a special case of the new one, and the family size of new sequences is much larger than those previously mentioned, which means that there was a great improvement in the data rate. On the other hand, a previous construction of 16-QAM GCSs presented by Zeng is also a special case of the new one in this paper, when . In the meantime, the proposed sequences have the same PMEPR upper bound as the previously mentioned sequences presented by Li when applied in OFDM systems, which increase the data rate without degrading the PMEPR performance. The theoretical analysis and simulation results show that the proposed new sequences can achieve a higher data rate and a low PMEPR.

High speed integrated RF–VLC data communication system: Performance constraints and capacity considerations

The discussion of mobile multimedia broadcasting technologies and service implementation in this chapter is limited to the broadcasting network based scheme can be received by portable or hand-held devices with a small screen. Similar to DTTB systems, digital mobile multimedia broadcasting systems are designed for high-data-throughput (to support multiple low-data-rate services) transmission through wireless channels (VHF/UHF bands in terrestrial, S- or L-band for satellite networks). The chapter summarizes the features of DVB-H, Advanced Television Systems Committee (ATSC)-M/H, China Multimedia Mobile Broadcasting (CMMB), and the new released DVB Next Generation Broadcasting System to Handheld (NGH) standards with the focus on the technical merits of reliable transmission under wireless, mobile environment and the robust reception using the portable or hand-held devices. ATSC-Mobile/Handheld (ATSC-M/H) is the standard for the DTV mobile transmission developed by the ATSC in 2007. The ATSC-M/H system shares the same RF channel of the traditional ATSC broadcast services.

Decision letter: Neural markers of predictive coding under perceptual uncertainty revealed with Hierarchical Frequency Tagging

A low complexity maximum likelihood (ML) detection method is proposed for the square quadrature amplitude modulation (QAM) constellation. In order to reduce the implementation complexity of ML detection, set-partition, subset-selection, and subset-shift are recursively applied to the square QAM constellation. The estimated square QAM symbol is finally given in a closed form as a function of the received signal and the estimated channel. Complexity analysis and numerical simulation confirm that the proposed detection method reduces the implementation complexity substantially and achieves exactly the same performance as the conventional ML detection irrespective of the channel estimation error.

In the presence of channel fluctuation, rate adaptation is one way to maintain the quality of the link at a desired level. This is especially important in ad hoc wireless networks, where temporary channel fluctuations might create frequent needs for rerouting that would result in severe overhead and adversely affect the performance. We study an unusual method of passive rate adaptation in which some bits are dropped at the receiver end of a link. The symbol-error probability decreases as some bits are dropped. In terms of the distortion for a realtime analog signal, the tradeoff is between more reliable detection of fewer bits and less reliable detection of more bits. Our scheme achieves smaller distortion for a certain region of signal-to-noise ratio (SNR) values when compared with the original scheme without rate adaptation. Two examples, uniformly spaced, uncoded pulse amplitude modulation and quadrature amplitude modulation, are studied and compared for both a Gaussian channel and a Rayleigh fading channel. We conclude that our scheme is more suitable to use in a fading channel than in a Gaussian channel. We also verify that our scheme has a larger applicable region of SNR values when a nonuniform constellation is used, since the important bits are given additional protection.

In this paper, we propose a noisy and dynamic-index partitioned modulation (IPM) to secure a quadrature amplitude modulation (QAM) constellation transmission over a non-degraded wiretap channel. Unlike approaches that rely on multi-antenna systems or tight amplitude-phase tracking, IPM partitions QAM into multiple disjoint subsets that are separately indexed by a dynamic key, known at the transmitter (Alice) and the legitimate receiver (Bob), but not at the eavesdropper (Eve). The proposed IPM maps the information bits into multiple sequences, each one lying in a different partition of the QAM constellation space. This mapping is performed through a cross-bit labeling that we define to increase the confusion at the eavesdropper, while minimizing the bit error rate (BER) at the legitimate receiver. As the eavesdropper is not aware of the dynamic index pointing to the different partitions, the IPM creates larger Voronoï detection zones around Bob’s symbol compared to Eve. To induce further confusion at Eve, we inject random uniform noise into IPM symbols. The noise varies in a domain that is fully included in Bob’s larger detection zone, but it exceeds Eve’s detection zone. The performances of the noisy IPM scheme in terms of error rate and secrecy rate are analytically and numerically evaluated. Our results show that the IPM scheme creates on the Eavesdropper’s link an error floor, independently of its signal-to-noise ratio (SNR). However, the IPM scheme preserves the legitimate link, for which the BER decreases as the SNR increases. Indeed, the secrecy rate remains positive for all SNR values and achieves an asymptotical constant plateau value.

In South Korea, Broadcast companies have begun a trial 3D broadcasting service by delivering dual streams, such as a left view sequence with MPEG-2 video and a right one with MPEG-4 AVC video, within the 19.4 Mbps terrestrial bandwidth. However, this limitation of transmission bandwidth in the terrestrial broadcasting system may cause quality degradation compared to the current 2D broadcasting service. Recently, the Advanced Television System Committee (ATSC) has released a new service model called non-real-time (NRT) technology, which provides file download functionality over a terrestrial broadcasting system. And electronic manufactures have developed smart TV which enables to receive RF channel and IP protocol. In order to operate a full quality 3D service, this paper proposes an NRT-based hybrid broadcasting system in which one of two view sequences is transmitted as a real-time broadcasting program, and the other is transmitted prior to a real-time broadcasting program and is stored as a file. This system uses a method of referential relation and synchronization between MPEG-2 transport stream (TS) and the file downloaded by ATSC NRT or IP. Therefore, the proposed hybrid broadcasting system can provide stable, high quality 3D content while maintaining a backward compatibility with the current 2D broadcasting system, despite the terrestrial bandwidth limitation.

Fluid antenna systems (FAS) represent an emerging technology that enhances spatial diversity for wireless communications through reconfigurable antennas. Recently, coded modulation has been integrated into FAS. However, the system adopts uniform Gray-coded quadrature amplitude modulation (QAM) constellations, resulting in a gap between Bit-interleaved coded modulation (BICM) capacity and Shannon capacity. Geometric shaping non-uniform constellations (NUCs) is a promising approach for nearing Shannon capacity. In this paper, we derive the BICM capacity within the FAS system and use this metric to design NUCs for FAS. Simulation results confirm that the designed NUCs can achieve higher BICM capacity, approaching Shannon capacity, while providing improved error performance of 0.4 dB in link-level simulations.

We have studied direct RF undersampling reception to reduce the size and power consumption. We already developed a series/shunt switching type sample and hold (S/H) integrated circuit (IC) by using 90 nm complementary metal oxide semiconductor (CMOS) process for Ka-band (19.4 - 20.2 GHz) very small aperture terminal (VSAT) application. This IC performed signal-to-noise ratio (SNR) of higher than 27.3 dB. For the higher frequency operation and the reception of multi-level modulated signal, the SNR improvement will be required. In this paper, a 28 GHz-band S/H IC with higher SNR has been developed. In order to improve SNR at higher RF frequency, 65 nm CMOS process is introduced to enhance the switching speed of sampling, the size of hold capacitor is optimized and the two-stage output buffer amplifier is employed. The fabricated S/H IC performs the SNR of higher than 41.2 dB and the error vector magnitude (EVM) of 4.4% (32 Mbaud 64 quadrature amplitude modulation (QAM)) in 28 GHz-band.