Physical Layer Framing for ATSC 3.0

In this paper, we present performance evaluation of multiple physical layer pipe (PLP) based layered division multiplexing (LDM) systems for the next generation terrestrial broadcasting. In addition to a conventional multiple-PLP configuration, which is based on time division multiplexing (TDM), a variety of LDM configurations, which includes combinations of TDM and two-layer LDM, and three-layer LDM, are considered. Given three different broadcasting contents are delivered by three PLPs, performance comparison and analysis are provided when four different multiple-PLP configurations including TDM, two-layer LDM, and three-layer LDM are used.

In this paper, we present an efficient transmission method of multiple broadcasting services using layered division multiplexing (LDM) and scalable high efficiency video coding (SHVC) based on the next generation terrestrial digital broadcasting standard, advanced television systems committee 3.0. In a two-layer LDM system, each layer forms a physical layer pipe that carries base layer and enhancement layer video streams of SHVC, respectively. This combination of physical and presentation layers technologies can maximize channel utilization when multiple broadcasting services are delivered in a single radio frequency channel with different robustness and reception conditions. An intensive performance analysis is provided when the proposed combination of LDM and SHVC is compared with other approaches, such as time division multiplexing and/or high efficiency video coding simulcast broadcasting. Several performance measurements are also introduced, such as constant data rate measurement and constant quality measurement, which are used to evaluate the performance of video codecs in conjunction with different physical layer system parameters. A prototype hardware system with LDM and SHVC capable of selecting different parameter combinations is tested in the laboratory and in real field environments to verify the performance and feasibility of the proposed LDM and SHVC combination. Results show that the proposed LDM and SHVC combination provides significant gains on video service quality as well as reception robustness.

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.

Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention as a broadband wireless access technique for the next generation mobile communications systems. Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can take advantage of the channel frequency-selectivity and improve the average bit error rate (BER) performance due to frequency-diversity gain. However, conventional MC-CDMA requires the insertion of guard interval (GI) and this reduces the transmission efficiency. Overlap FDE technique has been proposed that requires no GI insertion. Recently, we showed that MC-CDMA using overlap FDE can provide almost the same BER performance as the conventional MC-CDMA downlink using the GI insertion. However, our previous work assumed the ideal channel estimation. In this paper, we propose a pilot assisted channel estimation technique suitable for MC-CDMA downlink using overlap FDE and evaluate the BER performance by computer simulation.

Cloud transmission (Cloud-Txn) with layer-division-multiplexing (LDM) was proposed as a candidate Physical Layer (PHY) technology for the next generation digital TV broadcasting system. In this paper, we investigate the performance of the upper-layer signal cancellation with DFT-based channel estimation techniques, due to their capability of providing near-optimal performance for challenging channels with long delay spread at low Signal to Noise Ratio (SNR). Both Pilot-Aided (PA) and Decision-Directed (DD) techniques are investigated and their performances are compared. The major issue with DFT-based techniques is the “edge effect” for OFDM systems with Null spectrum on either side of the useful spectrum, which serves as guard band. A Cloud-Txn/LDM system usually requires very accurate channel estimation to achieve very low residual upper-layer signal after the cancellation. In this case, the “edge effect” becomes a significant impairment. In this paper, we evaluate different data-padding methods to reduce the “edge effect”, which fill the Null spectrum with Virtual Pilots (VP). It is shown that, with proper data-padding technique, 30 to 40 dB signal cancellation can be achieved.

In ATSC 3.0 physical layer standard, a layered division multiplexing (LDM) scheme has newly accepted as one of the multiplexing schemes in order to improve the reception performance when multiple broadcasting contents are simultaneously delivered through a single RF channel. This paper presents comparison results of LDM and time division multiplexing (TDM) schemes under fixed reception environments, and analyzes the performance gain of LDM over TDM. From the field test results, it was confirmed that the LDM gain in the theoretical analysis is still maintained in the actual field.

In this paper, we propose a robust transmission scheme using Aggregated Physical Protocol Data Units (APPDU). The proposed method includes a Media Access Control (MAC) layer control for determining the number of preambles to be inserted based on the feed-back reply signal from a receiver; the generation of a multi-preamble aggregation frame by inserting the determined number of preambles into frames received from an upper layer; a physical layer for forming the multi-preamble aggregation frame generated in a data processing unit by using a physical layer frame; and the transmission of the formed multi-preamble aggregation frame. The proposed technique obtains performance improvement of about 3 dB in terms of SNR and 35% in terms of throughput efficiency.

"(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.")

The next generation digital TV (DTV) broadcast, namely Advanced Television System Committee (ATSC) 3.0, relies on substantial single frequency networks (SFN), each of which requires a studio to transmitter link (STL) to transmit data from the broadcast gateway (BG), leading to significant construction costs. Therefore, the wireless in-band distribution link (IDL) technology is proposed, which uses layered-division multiplexing (LDM) to transmit the STL data via wireless links from the BG to the SFN transmitters within the same spectrum as the broadcast services. In this paper, we propose the time synchronization and signal detection algorithm for wireless IDL systems with both unicast and broadcast signals. We introduce two multiplexing schemes, N-LDM and 3-LDM, and demonstrate their superiority over traditional frequency division multiplexing (FDM). To overcome the challenge of multi-access interference and synchronization errors caused by multipath, we develop a unique word (UW) design algorithm for transmitted signals and a double threshold correlation detection algorithm (DTCDA) that outperforms traditional ones. We employ a second threshold to enhance detection performance at low signal-to-noise ratios, and utilizes successive interference cancellation (SIC) to mitigate multiple-access interference. More importantly, our approach requires no knowledge of the unicast user number or channel state information. Simulation results validate the effectiveness of the proposed scheme.

The next-generation U.S. digital terrestrial television (DTT) standard ATSC 3.0 is the most flexible DTT standard ever developed, outperforming the state-of-the-art digital video broadcasting-terrestrial 2nd generation (DVB-T2) standard. This higher flexibility allows broadcasters to select the configuration that better suits the coverage and capacity requirements per service. Regarding the selection of pilot patterns, whereas DVB-T2 provides eight different patterns with a unique pilot amplitude, ATSC 3.0 expands up to 16, with five different amplitudes per pattern. This paper focuses on the pilot pattern and amplitude performance and optimization for time and power multiplexing modes, time division multiplexing and layered division multiplexing (LDM), respectively, of ATSC 3.0. The selection of the optimum pilot configuration is not straightforward. On the one hand, the pilots must be sufficiently dense to follow channel fluctuations. On the other hand, as long as pilot density is increased, more data overhead is introduced. Moreover, this selection is particularly essential in LDM mode, because the LDM implementation in ATSC 3.0 requires that both layers share all the waveform parameters, including pilot pattern configuration. In addition, there is an error proportional to the channel estimate of the top layer that affects to the lower layer performance.

A time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) scheme with dual Pseudonoise (PN) sequence is proposed for underwater acoustic (UWA) communication. Instead of using cyclic prefix (CP) or zero padding (ZP) as the guard interval, the proposed TDS-OFDM scheme uses two identical PN sequences as guard interval, and utilizes them for frame synchronization and channel estimation. The proposed TDS-OFDM increases the spectrum efficiency over the conventional CP or ZP OFDM systems where additional pilots have to be inserted for channel estimation. With the dual PN at each frame header, compressed sensing channel estimation is adopted and a rather simple equalization design reduces the receiver complexity. With a low-density parity-check (LDPC) code, the proposed system is simulated in doubly selective underwater acoustic channels with long multipath delay spread and severe Doppler spread. The results show that the TDS-OFDM achieves slightly better BER performance and higher spectrum efficiency than the conventional ZP-OFDM.

In this paper, we propose a new use of LMMSE and Lr-LMMSE algorithms for channel estimation in OFDM (Orthogonal Frequency Division Multiplexing) system which, as known suffers from the time variation of the channel under high mobility conditions using block pilot insertion. The loss of sub channel orthogonality leads to inter-carrier interference (ICI). Using many algorithms for channel estimation, we will show that, for a 16- QAM modulation, the LMMSE algorithm performs well to achieve this estimation but when the SNR (Signal Noise Rate) is high, the three algorithms (LS, LMMSE and Lr-LMMSE) performs similarly. The challenge in this paper is that we will demonstrate that the LMMSE algorithm performs well with the block pilot insertion and is not suitable just with comb pilot insertion.

Ubiquitous in modern critical infrastructure, networked cyber-physical systems (CPSs) are a collection of task-oriented systems whose cyber and physical resources are conjoined and coordinated to achieve unprecedented capabilities. In this paper, we study how physically independent systems can be made interdependent in the CPS context. In order to understand such interdependencies, we establish a system framework to investigate the effect of cyber coupling on physical control systems. In particular, we study the optimal control of networked control system jointly with power control problems in wireless communication networks. We show that the information exchange between cyber and physical layers not only makes the control system more efficient but also enhances its resilience to adversarial behaviors. In addition, as a result of interdependencies, a jamming attack on one CPS can benefit the performance of the other CPS. We use a two-CPS case study to demonstrate performance of the coupled system at both the physical and cyber layers.

In cellular communications, recently Multi In Multi Out (MIMO) and Massive MIMO research is getting attention for the need of high data rates in Long Term Evolution Advanced(LTE-A) and 5G Communications. In MIMO baseband signal processing at physical layer, both the channel estimation and the detection algorithms play a crucial role. In this paper it is discussed the estimation algorithms least square (LS) and minimum mean square error (MMSE) and the channel detection algorithms Zero Forcing (ZF) and MMSE. Currently none of the channel estimation algorithms of LTE-A offers twin advantages of low battery consumption and very low latency, which is a key requirement of 5G. It is expected the massive MIMO with 128 or more antennas will be a norm at 5G base stations. To achieve the ultra-low latency, the matrix computations for massive MIMO are the very big bottleneck in realizing the channel estimation and massive MIMO detection algorithms. For the optimization of the 5G Massive MIMO channel estimation and detection algorithms, the prerequisite is massive complex matrix inversion speed. In this paper, a parallel processing based coding scheme is proposed by using Gauss-Jordan elimination kernel algorithm on a single instruction multiple data (SIMD) stream vector processor to realize a complex matrix inverse with optimum speed which is the need of 5G channel estimation and detection.

The proposed work is aimed at improving bit error rate (BER) performance and spectral efficiency, increasing data rate, reducing inter-symbol interference (ISI) and inter-channel interference (ICI). Implementation of a conventional MC-CDMA system normally involves the use of QAM techniques for mapping. In the proposed work a mapping technique based on finite radon transform is used. The use of finite radon transform (FRT) improves orthogonality between the subcarriers. It also reduces ISI and ICI, which is due to the loss of orthogonality between carriers. Since discrete wavelet transform (DWT) is used instead of fast Fourier transform (FFT), which is employed in conventional multi-carrier CDMA techniques, the insertion of guard interval is not required and it offers better spectral efficiency. The result shows that the bit error rate performance of the proposed algorithm is far better than conventional techniques in AWGN channel.