Pansoo Kim

Robust frame synchronization for low signal-to-noise ratio channels using energy-corrected differential correlation

Recent standards for wireless transmission require reliable synchronization for channels with low signal-to-noise ratio (SNR) as well as with a large amount of frequency offset, which necessitates a robust correlator structure for the initial frame synchronization process. In this paper, a new correlation strategy especially targeted for low SNR regions is proposed and its performance is analyzed. By utilizing a modified energy correction term, the proposed method effectively reduces the variance of the decision variable to enhance the detection performance. Most importantly, the method is demonstrated to outperform all previously reported schemes by a significant margin, for SNRs below 5 dB regardless of the existence of the frequency offsets. A variation of the proposed method is also presented for further enhancement over the channels with small frequency errors. The particular application considered for the performance verification is the second generation digital video broadcasting system for satellites (DVB-S2).

Performance analysis of APSK modulation for DVB-S2 transmission over nonlinear channels

For increased bandwidth efficiency and receiver performance, standards for satellite broadcasting systems are evolving by utilizing efficient transmission techniques. The second-generation digital video broadcasting for satellites (DVB-S2) adopts the amplitude phase shift keying (APSK) modulation for enhanced performance over nonlinear channels. In this paper, we derive error rate bounds for APSK modulated symbols and generalize the bounds to the case of distorted constellation, which occurs when the maximum transmission amplitude is saturated by the soft-limiter type channel. The derived bound is shown to significantly improve the previously known result, to accurately predict both the symbol error rate and bit error rate in the entire signal-to-noise ratio (SNR) region of interest. Using the derived formula, the optimal input power level for the soft-limiter channel is determined, and the corresponding minimal error rates for 16- and 32-APSK are quantified. The result is also interpreted in terms of optimal input back-off (IBO) for nonlinear power amplifiers by evaluating the performance degradation as a function of IBO. Copyright

Design considerations of satellite-based vehicular broadband networks

Convergence between wireless networks is the main trend in current and future wireless communications. The distinct advantage of satellite and terrestrial network integration is the possibility to provide ubiquitous multimedia services in vehicles at any location. The key design considerations of mobile broadband satellite access technologies are given in this article. After presenting the conceptual models of a system and services, the design issues of satellite network synchronization and burst demodulation are described. The design considerations of medium access control, resource management, capacity, and buffer controls for internetworking are given. Also, the active antenna issues are provided along with a sample design.

The very short frame of mobile DVB‐RCS: Code design and QoS Performance

SUMMARY In this paper, the design of a new very short frame introduced in the upcoming version of DVB-RCS standard targeting interactive mobile services will be described. The frame design with a special focus on channel coding and performance are addressed in detail, as well as an evaluation of the QoS performance for realistic traffic scenarios, propagation channel conditions, and carrier sizes. Copyright r 2009 John Wiley & Sons, Ltd.

Robust frame synchronization for the DVB-S2 system with large frequency offsets†

This paper tackles the problem of frame synchronization design for the Digital Video Broadcasting standard via Satellite (DVB-S2) system. In particular, the design of a novel frame detection scheme exhibiting robustness against large frequency errors is proposed. Post-detection integration (PDI) is exploited to provide coarse frame alignment with limited complexity with respect to classical approximate maximum likelihood (ML) solutions. The novel scheme, denoted as differential generalized post-detection integration, derives from a pragmatic adaptation of the well-known generalized PDI scheme (IEEE Trans. Commun. 2007; 55(11):2159–2171), which eliminates its inherent source of weakness in the presence of large frequency offsets, i.e. its non-differential component given by non-coherent PDI. The proposed approach manages to reduce the remarkable performance gap with respect to approximate ML techniques available in the literature (IEEE Trans. Commun. 2002; 50(7):1062–1065), providing the designer with an interesting performance/complexity trade-off. Performance is numerically evaluated in terms of receiver operating characteristics and mean acquisition time (MAT), handling the acquisition procedure according to a single-dwell approach. Both threshold crossing and MAX criterion are contrasted to identify the best design solution. Copyright

Link Layer Coding for DVB-S2 Interactive Satellite Services to Trains

The railroad satellite channel is characterized by frequent signal outages due to tunnels, bridges and electrical trellises. While for medium/long tunnels the main option to offer reliable and uninterrupted connectivity deals with the adoption of gap-filling techniques, signal outages due to small bridges/tunnels or electrical trellises can be faced with ad-hoc recovery techniques. In this paper, we face the problem from a link layer perspective, showing how a proper design of an erasure correcting code operating at link layer represents a valuable countermeasure against short outage events. The performance evaluation is developed in comparison with a more traditional technique based on physical layer coding in combination with a long channel interleaver. Advantages of the link layer coding scheme will be shown.

Efficient coarse frequency synchronizer using serial correlator for DVB-S2

This paper proposes an efficient coarse frequency synchronizer for digital video broadcasting - second generation (DVB-S2). The input signal requirement of acquisition range for coarse frequency estimator in the DVB-S2 is around plusmn1.5625 Mhz, which corresponds to 6.25% of the symbol rate at 25 M baud. At the process of analyzing the robust algorithm among data-aided approaches, we find that the Luise & Reggiannini (L&R) algorithm is the most promising one for coarse frequency estimation with respect to estimation performance and complexity. However, it requires many multipliers and adders to compute output values of correlators. We propose an efficient architecture identifying the serial correlator with the buffer and multiplexers. The proposed coarse frequency synchronizer can reduce the hardware complexity about 92% of the direct implementation. The proposed architecture has been implemented and verified on the Xilinx Virtex II FPGA.

Broadband systems based on DVB-S2 and mobile DVB-RCS, and their future applications to broadband mobiles

In this paper, the design and implementation of broadband adaptive satellite communications and broadcasting convergence technology (BcSAT) system and a mobile broadband interactive satellite access technology (MoBISAT) system, are presented. The BcSAT system aims at providing the next generation satellite broadcasting service through Ka-band based on DVB-S2 standard. And, the MoBISAT system, which is a mobile broadband satellite access system, provides Ku-band satellite TV and Ka-band high speed internet based on DVB-S/DVB-RCS standards to the passengers and crews for land, maritime and aeronautical vehicles. Therefore, this paper addresses the main design features and implementation for the BcSAT and MoBISAT system, respectively

Efficient multiplierless architecture for frame synchronization in DVB-S2 standard

The first challenging step of the demodulation of the DVB-S2 signal with function of VCM (Variable Coding and Modulation)/ACM (Adaptive Coding and Modulation) is the detection of the Physical Layer (PL) header. PL header is transmitted using π/2-BPSK modulation and is composed of a fixed part (26 bits of Start Of Frame (SOF)) and a variable part (64 bits codeword of PL Signaling (PLS) code that defines the structure of the PL frame). Since the 90 bits corresponding to the PL header are affected by noise, the carrier frequency offset and the phase noise, the synchronization task in a DVB-S2 receiver is thus a critical task. In this paper, we present a properties of the Hadamard code used to encode the information of the PLS code to reinforce frame detection before knowing the actual value of the PL code. Moreover, we propose to perform the computation in the polar domain in order to avoid the need of multiplier and thus, to obtain a very low cost implementation. The associated decoder architecture is presented together with the measured performance at several SNRs.

Efficient channel equalization technique for DVB-S2 standard

This paper deals with design of the appropriate time domain equalizer based on DVB-S2 specification for mobile application. Firstly, we consider different ISI effect under various channel condition through field measurement. With reflection of channel effect, we suggest adaptive filter as channel condition and synchronization step mode like code start/hot start. Finally, we implement the blind FS equalizer compatible with entire DVB-S2 specification. In addition, at the practical point of view, we seek the performance impact by nonlinear satellite channel condition plus freq. selective channel and optimize it to minimize the performance loss.