Yunfeng Guan

On channel estimation and equalization in TDS-OFDM based terrestrial HDTV broadcasting system

In TDS-OFDM (time-domain synchronous orthogonal frequency division multiplexing) systems, pseudonoise (PN) sequences rather than cyclic prefixes are inserted as guard interval, between consecutive inverse discrete Fourier transformed (IDFT) symbol blocks. Since the PN sequences can also be used as training symbols, such system can provide higher spectrum efficiency. However, due to non-cyclic property of the signal, the simple channel estimation and equalization techniques for conventional cyclic prefixed OFDM (CP-OFDM) can not be applied to TDS-OFDM. In this paper, we propose a channel estimation and equalization method for TDS-OFDM. Channel estimation depends on time domain correlation and iterative interference cancellation techniques, while equalization is based on tail cancellation and cyclic restoration algorithm (TCCR). It is shown that our proposed method can provide satisfactory performance in TDS-OFDM based terrestrial high-definition television (HDTV) broadcasting system.

Using LDM to Achieve Seamless Local Service Insertion and Local Program Coverage in SFN Environment

Layered division multiplexing (LDM) is a spectrum efficient non-orthogonal multiplexing technology that has been adopted in the Advanced Television Systems Committee (ATSC) 3.0 Physical Layer Standard as a baseline technology. This paper studies a two-layer LDM with one layer used for providing a global service through a single frequency network (SFN), and the other for providing local coverage/services, such as location targeted advertising or local content insertion. The pilot boosting effect on SNR and co-channel interference is also analyzed. The LDM upper layer can be used to deliver time-division multiplexed mobile-HD and 4k-UHD services. The LDM lower layer with a negative SNR threshold can reliably provide seamless local coverage/service from each SFN transmitter without coverage gaps among adjacent SFN transmitter service areas. No directional receiving antenna is required for the local service reception and receivers simply tune into the stronger signal. In such LDM systems, while the upper layer is operating in a traditional SFN mode, the lower layer operates in a special form of distributed MIMO or gap-filler mode to provide targeted local coverage. For implementing the two-layer system introduced in this paper, only ATSC 3.0 baseline technologies are used, i.e., there is no need to modify the ATSC 3.0 standard. Given the upper and lower layers’ data rate requirements and the SNR thresholds, the lower layer power, with respect to the upper layer (injection level), can be optimized to maximize upper and lower layer performance and coverage. Since the advertisement time of the local service is typically less than 20% of the program time, nonreal time could be used to play-back the local content at five times the transmission bit rate for better (audio/video) service quality.

A Robust and Adaptive Carrier Recovery Method for Chinese DTTB Receiver

This paper presents a robust and adaptive carrier recovery method for Chinese digital terrestrial television broadcasting (DTTB) system in which pilot signal and pseudonoise (PN) sequence are adopted to help carrier recovery. The conventional methods utilize pilot or PN sequence respectively. In this paper, we try to combine the advantage of each method together and propose a well designed state machine to control system state automatically. Moreover, as for using PN sequence, a fine PN tracking state is introduced to ensure the robustness of the proposed method. Software simulations show that the proposed method can provide large acquisition range, short acquisition time and small tracking jitter in severely distorted static and dynamic channels. Lab tests and field trials also prove its good performance in real propagation environments.

Using LDM to achieve seamless local service coverage in SFN environment

This paper studies layered division multiplexing (LDM) for local cover age/services, such as location targeted advertisement or local content insertion. The LDM upper layer can be used to deliver time-division multiplexed (TDM-ed) mobile-HD and 4k-UHD services. The LDM lower layer with a negative SNR threshold can reliably provide seamless local coverage/service from each single frequency network (SFN) transmitter without coverage gaps among adjacent SFN transmitter service areas. No directional receiving antenna is required and receivers simply tune into the stronger local received signal. This is the concept of Cloud Transmission. In LDM system, the upper layer is operating in a traditional SFN mode to provide network-wide coverage. The lower layer is actually operating in a special form of Distributed MIMO or gap-filler mode to provide a targeted local coverage. Only Advanced Television Systems Committee (ATSC) 3.0 Baseline Technologies are used, i.e., there is no need to modify the ATSC 3.0 standard. Giving the upper and lower layers data rate requirements and the SNR thresholds, the lower layer injection level can be optimized for maximizing upper and lower layer performance and coverage.

Dedicated Return Channel for ATSC 3.0

To support emerging interactive services, a consensus to include an optional, in-band dedicated return channel (DRC) for the next-generation terrestrial broadcast system (ATSC3.0) has been reached. This paper introduces the design of DRC as well as several implementation concerns. First, the network architecture, link budget, and radiation feature of DRC are described in detail. Then the requirements and detailed design of both the physical layer and the MAC layer of DRC are presented respectively. Meanwhile, the performance of DRC is evaluated and comparisons with typical techniques are carried out in terms of bit error rate, access probability, resource utilization, etc. Furthermore, the cooperation between downlink broadcast and DRC is analyzed.

Terrestrial broadcast technologies for next generation broadcast wireless systems

The next generation broadcast wireless (NGB-W) system is aimed to provide high-speed, ubiquitous, and secure tri-play services to massive users. In this paper, a new terrestrial broadcast solution for the NGB-W system is proposed. The system and the key techniques of the proposed solution are introduced. The performance of the proposed solution is evaluated by simulations. It is shown that the performance of the proposed solution is better than that of the second generation terrestrial broadcast systems of Digital Video Broadcasting (DVB).

Error rotated decision feedback equalizer for Chinese DTTB Receiver

In this paper, an error rotated decision feedback equalizer (DFE) based on the minimum-mean-square error (MMSE) criterion is proposed for Chinese DTTB Receiver. When the DFE is complex, the length of it is large and the convergence algorithm is least mean square (LMS), the residual carrier frequency error and the phase noise from tuner will seriously weaken the performance of DFE. As an adaptive filter, the DFE will respond to the variation of phase error. Furthermore, it is difficult to estimate the phase error when the other factors of channel distortion exist. The proposed DFE has properly solved these problems. Analysis and simulation show that not only phase noise can be estimated and nicely compensated but also DFE will not be interfered by the phase error. So the performance of DFE is improved.

Brief introduction on the key technologies of NGB-W broadcasting channel

With the rapid development of information technology, television has started the development evolution which is from the first generation digital television (DVB-C, DVB-S, DVB-T, ATSC, ISDB-T, DTMB) to the second generation digital television (DVB-C2, DVB-S2, DVB-T2, ATSC 3.0). Interiorly, to cooperate the information industry development strategic target of triple play in China, SARFT has launched the strategic plan of Next Generation Broadcasting (NGB), and set “suitable to Chinese conditions, triple play, combination of wire and wireless, the whole process and network” as strategic target of next generation broadcasting in China. NGB-W is the wireless part of Chinese Next Generation Broadcasting, it is a three-dimensional complete coverage intelligent fusion media network which includes terrestrial mobile, terrestrial fixed and satellite network. NGB-W is and advanced technology scheme which is suitable to Chinese conditions, and satisfies the business and technology requirements of NGB-W system. This scheme takes OFDM and LDPC as the core, meanwhile, it absorbs BICM, space diversity and space multiplexing, carrier aggregation and other the latest technological achievements and systematic design idea in existing wireless communication technique. It not only is relatively improved than the first generation technology on the transmission efficiency, but also has good flexibility and compatibility, and it can effectively satisfy all media services demand of next generation broadcasting television system. This paper will give a brief introduction to the new designed NGB-W broadcasting channel technology scheme, which includes network architecture, technology architecture, system parameters and scheme performance. In section 1, we will briefly introduce the corresponding background of NGB-W. In section 2, we will introduce the network architecture and link structure of NGB-W broadcasting. In section 3, we will emphatically introduce the technology architecture and system parameters of NGB-W broadcasting channel technology scheme. In section 4, we will compare the NGB-W technology with other existing technologies in the aspects of the key technologies and performance index. In the last section, we will give a brief conclusion.

Variable Min-Sum decoding based on generalized mutual information metric

Min Sum algorithm simplifies the non-linear check node operation of Belief Propagation algorithm via linear approximation, which greatly reduces the complexity of realization of decoder but degrades the performance as well. The resulting sub-optimality could be tempered via scaling of LLRs, e.g. fixed optimal scaling applied to Min Sum output resulting in the Normalized Min Sum algorithm, and variable scaling schemes gradually appear in literature. In this paper, we study the variable scaling decoding algorithm, and propose to generate variable scaling sequences via generalized mutual information (GMI) metric. Simulation results on real LDPC codes for different decoding algorithms have shown that our GMI metric performs better than the variable scaling scheme appearing in literature, and meanwhile improves substantially in terms of BER over the conventional Normalized Min Sum algorithm.

Combined NR Decoding With Decision Feedback Equalizer for Chinese DTTB Receiver

In this paper, the effect of the Minimum-Mean-Square Error Decision Feedback Equalizer (MMSE-DFE) when combined with decoding that is applied to the coded transmission, is studied. When the length of MMSE-DFE is large, it is more realizable to use the decoding value as the decision value. Here, the DFE using the Nordstrom-Robinson (NR) decoding value is proposed. Through simulation and by testing results, the DFE combined with NR decoding shows better performance than the traditional DFE. Moreover, this paper supports an approach to cancel partial residual Inter-Symbol Interference (ISI) that is caused by decision delay when DFE is combined with NR decoding.