Eduardo Garro

Coexistence of digital terrestrial television and next generation cellular networks in the 700 MHz band

With the spectrum liberation obtained by the deployment of digital terrestrial television and the analog TV switch-off, new bands are being assigned to IMT LTE. In the first cellular deployments in the digital dividend at the 800 MHz band, problems emerged due to the interference cellular networks can cause to DTT signals. Possible solutions imply either an inefficient use of the spectrum (increasing the guard band and reducing the number of DTT channels) or a high cost (using anti-LTE filters for DTT receivers). The new spectrum allocated to mobile communications is the 700 MHz band, also known as the second digital dividend. In this new IMT band, the LTE uplink is placed in the lower part of the band. Hence, the ITU-R invited several studies to be performed and reported the results to WRC-15. In this article, we analyze the coexistence problem in the 700 MHz band and evaluate the interference of LTE signals to DTT services. Several coexistence scenarios have been considered, and laboratory tests have been performed to measure interference protection ratios.

MIMO Scattered Pilot Performance and Optimization for ATSC 3.0

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.

Pilot optimization for mobile services in ATSC 3.0

The Advanced Television System Committee (ATSC) has released ATSC 3.0, the next-generation U.S. Digital Terrestrial Television (DTT) standard. ATSC 3.0 allows a higher flexibility compared to the previous state-of-the-art DTT standard, DVB-T2 (Digital Video Broadcasting - Terrestrial 2nd Generation). This higher flexibility allows broadcasters to adapt transmission configuration to network and reception requirements. Regarding pilot patterns (PP), whereas DVB-T2 provides 8 different PPs with a unique pilot boosting, ATSC 3.0 extends up to 16 different PPs, with 5 different boostings per each one. This paper is focused on the study of the PP and boosting combination that optimizes performance for time (Time Division Multiplexing, TDM) and power (Layered Division Multiplexing, LDM) multiplexing modes of ATSC 3.0 in mobility reception conditions. The selection of the optimum PP is particularly essential in LDM mode, because it must be shared between the two LDM layers.

Performance evaluation of Layer Division Multiplexing (LDM) combined with Time Frequency Slicing (TFS)

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.

Performance evaluation of MIMO channel estimation for ATSC 3.0

ATSC 3.0, the latest Digital Terrestrial Television (DTT) standard, allows a higher spectral efficiency and/or a transmission robustness with Multiple-Input Multiple-Output (MIMO) technology compared to existing single-antenna DTT networks. Regarding MIMO channel estimation, two pilot encoding algorithms known as Walsh-Hadamard encoding and Null pilot encoding are possible in ATSC 3.0. The two MIMO pilot algorithms are standardized so as to have the same pilot positions and the same pilot boosting as SISO, but the performance has not been evaluated. This paper focuses on the performance evaluation of the two MIMO pilot encoding algorithms in ATSC 3.0 using physical layer simulations. Results can be used as guidelines or recommended practices to broadcasters to select the MIMO pilot encoding algorithm that better suits their service requirments. Several channel estimation algorithms have been evaluated in both mobile and fixed reception conditions. The simulation results show that Null pilot encoding provides slightly better performance than Walsh-Hadamard encoding for fixed reception but worse performance for mobile reception, especially at high signal-to-noise ratios.

Layered Division Multiplexing With Multi-Radio-Frequency Channel Technologies

The advanced television system committee (ATSC) is to release the next-generation U.S. digital terrestrial television standard, known as ATSC 3.0. Layered division multiplexing (LDM) is one of the new physical layer technologies included in the standard, which enables the efficient provision of mobile and fixed services by superposing two independent signals with different power levels. ATSC 3.0 has also adopted a novel transmission technique known as channel bonding (CB), which splits the data of a service into two sub-streams that are modulated and transmitted over two radio-frequency (RF) channels. This paper investigates the potential use cases, implementation aspects, and performance advantages, for combining LDM with CB and also with the multi-RF channel technology time frequency slicing (TFS) introduced in digital video broadcasting - terrestrial second generation (DVB-T2) (as an informative annex) and digital video broadcasting - next generation handheld (DVB-NGH) which allows distributing the data of a service across two or more RF channels by means of time slicing and frequency hopping.