Hyoungsoo Lim

A Higher Data-Rate T-DMB System Based on a Hierarchical A-DPSK Modulation

Hierarchical modulation can be effectively used to enhance terrestrial digital multimedia broadcasting (T-DMB) or digital audio broadcasting (DAB) systems in response to both the demand for higher data-rate and the need to be backward compatible with legacy receivers. QAM-type modulations are well-liked for hierarchical transmission but require coherent detection based on pilot symbol aided channel estimation. In the T-DMB or the DAB system using DQPSK modulation, however, any available pilot symbols except for the phase reference symbol do not exist. Differential amplitude phase shift keying (DAPSK) modulation is easily applied to the T-DMB system for a hierarchical modulation but may be susceptible to fast fading. As a good candidate for a hierarchical modulation of T-DMB to solve the above problems, we propose an amplitude differential phase shift keying (A-DPSK) modulation which is robust to fast fading by estimating only amplitude coefficients of the channel transfer function with the use of amplitude pilots. To raise the accuracy of channel estimation, we arrange the amplitude pilots in a come-type and introduce a noise-reduction scheme of averaging estimated channel coefficients. Simulation results show that the proposed A-DPSK provides a good choice for achieving a higher data-rate over other possible modulation schemes for advanced T-DMB or DAB systems.

Novel Interference Cancellation Technique Based on Matrix Computation for FTN Communication System

Since the communication system based on FTN signaling uses faster symbol rate than Niquist rate, the ISI is generated inevitably. Therefore, the interference cancellation process is required in the receiver with FTN signaling. The interference cancellation operation is a burden in the receiver. To reduce the complexity of the interference cancellation process, this paper proposes simple interference cancellation and signal detection technique. First, the signal modeling based on matrix computation is described, and then very simple interference cancellation and signal detection technique is introduced based on the described matrix signal model.

Detection of Hierarchically-Modulated Data for Advanced T-DMB Receivers

This paper proposes an efficient detection method of hierarchically-modulated data for an advanced terrestrial digital multimedia broadcasting (AT-DMB) receiver. Hierarchical modulation, where low-priority (LP) symbols are hierarchically added to the existing high-priority (HP) symbols, has been considered to be useful for increasing the data rate in AT-DMB systems. The distance between two neighboring LP symbols is limited by the noise margin of HP symbols and thus should be shortened to minimize the effect on the detection of HP symbols. To cope with the poor condition of LP symbols, we introduce a coherent detection method based on coded decision-directed (CDD) channel estimation (CE). CDD-CE may provide an accurate estimation result even under the infrequent pilot arrangement of the T-DMB system. Additionally, we propose a moving average (MA) method in frequency direction to reduce noise existing in the estimated channel coefficients. Simulation results show that the proposed method can be a good solution to successfully detect LP data.

A simple carrier frequency detection algorithm for fine compensation of Doppler shift in direct-sequence code division multiple access mobile satellite communications

A simple algorithm is proposed for carrier frequency synchronization after PN code acquisition using FFT (fast Fourier transform) in a direct-sequence code division multiple access mobile satellite communications system. The proposed algorithm shows almost the same performance as the phase differential algorithm under additive white Gaussian noise channel environments. The proposed algorithm, however, largely reduces hardware complexity when a two-dimensional search algorithm is employed for PN code timing acquisition and coarse Doppler shift compensation since the proposed algorithm shares the FFT operator with the two-dimensional search.

Performance of the DVB-T2 system with MIMO Spatial Multiplexing

This paper presents the performance of the DVB-T2 broadcasting system including SISO, 2×1 MISO Alamouti and 2×2 MIMO Spatial Multiplexing. The DVB-T2 standard is now optionally using 2×1 MISO Alamouti system that is known to be optimal to achieve greater diversity gain. However in the future it is expected that the next generation of various broadcasting systems will take the MIMO system to obtain higher spectral efficiency as well as diversity gain. Thus we adapt a simply-adjusted DVB-T2 system as one application of MIMO system and provide its computer simulation results comparing the performance of conventional DVB-T2 to MIMO DVB-T2.

Converged architecture for broadcast and multicast services in heterogeneous network

This paper proposes a converged architecture for broadcast and multicast services in a heterogeneous network. To support the broadcast/multicast services in the long-term evolution (LTE) network, the standard enhances multimedia broadcast multicast service (MBMS). In the broadcast network, digital video broadcasting for handhelds (DVB-H) is the standard for broadcasting IP data services to user equipment (UE). Accordingly, the converged LTE and DVB-H network can be used to service the broadcast/multicast services. To employ the converged network, additional entities are required for the contents management, electronic service guide (ESG) management and resource management. Therefore, we propose several logical entities to fulfill functionality from the above mentioned issues. The proposed logical entities are as follows: an integrated contents server, an integrated ESG server and an integrated management server. We also present several scenarios for implementing the converged architecture and compare the advantage of each scenario. Service providers can exploit the converged architecture according to preference and equipped devices. This study is of particular interest to the service providers because it provides the service providers with an insight of the various scenarios to make the converged architecture for broadcast/multicast service.

Augmented Data Transmission for the ATSC terrestrial DTV system

In this paper, we propose an Augmented Data Transmission (ADT) system which can transmit an additional data stream in the ATSC terrestrial DTV system. The proposed ADT system can offer an additional data of rate up to a few Mbps based on hierarchical modulation, DTV signal cancellation, and advanced error correction code. Since the proposed ADT system uses the in-band hierarchical modulation, it does not require any additional RF spectrum to increase the data capacity in a 6 MHz RF channel.

Joint masking and PAPR reduction for digital broadcasting system with faster-than-Nyquist signaling

Since FTN signaling uses greater symbol rate than Nyquist rate, the FTN signaling offers higher spectral efficiency than that of Nyquist signaling. However, ISI is derived from the non-orthogonality of FTN signaling. The ISI leads to an increase of the envelope fluctuations. Consequently, high PAPR occurs in the FTN signaling. In the satellite communication link, the high PAPR causes performance limitation because of non-linear amplification effects. Therefore, to adopt FTN signaling, PAPR reduction scheme is required in satellite digital broadcasting system. Furthermore, for various reasons such as security of pay-contents, data masking can be efficiently used for digital broadcasting system. Therefore, this paper proposes joint masking and PAPR reduction technique based on scrambling signal frame for the broadcasting system based on DVB-S2 standard with FTN signaling.

Synchronization of FTN systems for UHDTV

In this paper, a pilot pattern for multicarrier faster-than-Nyquist (MFTN) signaling is proposed to get a better synchronization with reduced inter-carrier interference (ICI). The MFTN signaling is suitable for the UHDTV services by improving the spectral efficiency up to twice that of the conventional orthogonal frequency division multiplexing (OFDM). However, the MFTN scheme causes ICI which reduces the performance of synchronization. The proposed scheme reduces the ICI to improve the performance over the conventional pilot patterns.

A Study of Transmission Structure for IP-based Digital Broadcast Systems

IP-based, next generation digital broadcast systems transmit DASH segment files. Designed by the DASH system, DASH segment files provide variable quality of contents, while the size of DASH segment files varies even if the file has the same quality. Delays and inefficient use of resources are major challenges in the transmission of variable size DASH segment files in broadcasting systems. Traditional broadcasting transmission systems are designed according to characteristics of physical layer of broadcast, and thus, delay and inefficient resources use is difficult to find. Yet, transmission content quantities continue to rise in the next-generation broadcasting systems (e.g. FHD, UHD (4k, 8k)) with variability of the segments file size as well. Resources for next-generation broadcast are more abundant than traditional broadcast with recent development, but continue to be limited and fixed. Resource delay and inefficiency are important but has not been extensively studied. We propose a transmission structure solution to analyze the delay and efficiency of the resource as each DASH segment file is transmitted, and have further performed simulation studies.