Sebastien Lafleche

An ATSC DTV receiver with improved robustness to multipath and distributed transmission environments

This paper presents the design and implementation of an 8-VSB DTV receiver for indoor and distributed transmission environments. The receiver is designed to handle severe multipath distortion from indoor and Single Frequency Network (SFN) transmission conditions. The architecture of the receiver is first introduced. The adaptive equalizer structure and design are then discussed in detail. A channel-matched filter is employed as a pre-filter such that the signal energies from different echoes are combined optimally and the signal to noise ratio of the equalizer input is maximized. Feedforward and feedback equalizers are used to handle the pre-echo (pre-cursor) and post-echo (post-cursor), respectively. The feedforward filter is designed to minimize the pre-cursors or convert them into post-cursors, while the feedback equalizer is used to eliminate the post-cursors. Initial tap coefficients are computed to speed up the convergence of these two filters based on the channel estimation. Laboratory tests show that the new prototype DTV receiver has very robust performance in multipath environments. 0 dB echoes can be handled with this receiver due to the enhanced design of the equalizer. It can withstand a -10 dB single echo within a -29.5 to +38.5 microsecond range and a 0 dB echo within a 12 microsecond range.

A channel characterization technique using frequency-domain pilot time-domain correlation method for DVB-T systems

A new channel characterization technique using frequency-domain pilot time-domain correlation (FPTC) method for DVB-T systems is proposed in this paper. The proposed technique is based on the time-domain correlation between the received signal and the pilot sequence embedded in the DVB-T signal, which is derived from the frequency domain pilots and known to the receiver. Interruption to the broadcasting service can be avoided, since only regular DVB-T signal is needed for channel characterization. In comparison with other digital TV characterization techniques, the major advantages of this proposal are its implementation simplicity, large dynamic range, and the robustness against synchronization errors. Channel impulse responses can be accurately estimated without timing recovery. The impact of the non-perfect carrier recovery is very small, since the correlation is only computed on a short time period of the received signal. The proposed method has been verified through numerical simulations and lab tests. Possible ways of improving the estimation accuracy are also discussed.

Cloud Transmission: System simulation and performance analysis

The Cloud Transmission (Cloud Txn) is a new paradigm of broadcasting or point-to-multipoint transmission system, designed for efficient and flexible use of the spectrum, robustness against noise, multipath and co-channel interference, and capability to provide fixed or mobile reception while using low transmission power. Besides system capability, the system should meet many other challenging issues. The main purpose of this work is to demonstrate that this proposed new system is feasible and it meets today and future needs of the broadcasting industry.

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.

The effects of public safety mobile systems operations (in TV channels 63/68) on DTV and NTSC broadcasting

The issue of Public Safety (PS) in North America has become more crucial since the Digital Television (DTV) transition allotment plans were developed. Therefore, Canada has designated a modest amount of spectrum in Television broadcast channels 63 and 68 for PS use. As a result of this decision, Co-channel Interference (CCI) and Adjacent-Channel Interference (ACI) resulting from PS operation in channels 63/68 into and from surrounding NTSC or DTV service need to be considered. This paper discusses the impact that (CCI) and (ACI), produced by PS mobile system operation in channel 63/68, has on DTV and NTSC operating in and around channels 63/68.

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.

Field Measurements of EM Radiation From In-House Power Line Telecommunications (PLT) Devices

This paper presents the results of the tests performed by the Communications Research Centre Canada (CRC) to determine the levels of electromagnetic radiation resulting from the operation of commercially available in-house power line telecommunication (PLT) devices, and to evaluate their potential effects on FM radio and low-VHF TV broadcasting services. The tests were performed when the devices were operating under real conditions in a number of typical Canadian suburban residential houses. The corresponding field strength measurements were made at specific distances from the houses and could then be compared with the present regulatory limits.

Layered-Division Multiplexing: An Enabling Technology for Multicast/Broadcast Service Delivery in 5G

Future 5G systems will include a point-to-multipoint (P2MP) transmission mode to achieve high capacity and high spectrum efficiency for multiple use cases, such as IoT, lifeline communications, and broadcast-type services. Layered-division-multiplexing (LDM) is a novel non-orthogonal multiplexing technology recently adopted by the next generation digital TV broadcast system, ATSC 3.0, which is capable of providing significant capacity improvement when delivering multiple broadcast services simultaneously. This article explores the application of LDM as an enabling technology for 5G to achieve high-efficiency P2MP transmission and to deliver more diversified broadcast-type services using the mobile broadband infrastructure. The potential advantages that can be offered by LDM are demonstrated by capacity analysis and computer simulations. Coverage studies show that a 5G P2MP subsystem with LDM can deliver high-quality broadcast services using the broadband infrastructure. Finally, some general guidelines on the receiver implementation are presented to minimize the hardware complexity of consumer devices.

Coverage study of ATSC 3.0

The ATSC 3.0 next generation digital TV standard adopts state-of-the-art coding and modulation, as well as the new Layered Division Multiplexing (LDM) technology in addition to the traditional TDM/FDM. It is a very flexible system capable of combining different services in one RF channel with different robustness and reception conditions. The coverage for ATSC 3.0 is very different from the legacy one-tower-one-coverage ATSC 1.0 system. With the new enabling technologies, the ATSC 3.0 can greatly increase the coverage/service areas, reduce the distance between co-channel assignments, and introduce local program insertion and targeted advertisement. This paper discusses the ATSC 3.0 coverage and co-channel interference issues, using LDM technology with different operating parameters. Similar to LTE, the ATSC 3.0 co-channel assignment could be reduced to two times of service coverage radius (2R). This means an improvement of the spectrum efficiency by up to 4 times in comparison with todays system. The deployment of Single Frequency Network (SFN) can further improve the coverage and reduce the interference.

Channel estimation strategy for using LDM to deliver local content insertion in ATSC 3.0

Delivering local content in terrestrial digital TV (DTV) single-frequency-networks (SFNs) is of great interest to broadcasters, which can support business cases such as local news, location-based applications and targeted advertisements. The recently adopted Layered-Division-Multiplexing (LDM) technology offers a new solution to achieve high-throughput local content insertion from any transmitters, at anytime, and with flexible coverage areas. To achieve the high-throughput and flexbile coverage of the local services delivered using LDM, the receivers need to estimate the specific channel response corresponding to the trasnmitter emitting the desired local service. This is difficult to achieve in reality since the ATSC 3.0 standard does not provide an inherent mechanism to help receivers obtain separate channel estimates when receiving signals from different transmitters in SFN. This paper addresses this challenge and presents several channel estimation solutions at receivers to enable high-efficiency local content insertion within an ATSC 3.0 SFN. In addition, a novel channel separation algorithm is proposed to significantly reduce the performance degradation caused by the inaccurate channel estimate due to the deterministic co-channel interference.