Deock-Gil Oh

Enhanced Frame Synchronization for DVB-S2 System Under a Large of Frequency Offset

This paper investigates the possible robust technique of frame synchronization for DVB-S2 system. Basically, we focus on the improvement of correlation characteristic, instead of establishing the strategy of frame synchronization with optimal scenario due to variable transmission frame lengths of DVB-S2 standard. To cope with a large frequency offset as a maximum 20% value normalized to symbol rate, the differential generalized post detection integration scheme is newly proposed in the paper. The fruitful results of the paper are described by the suitable analytical approach through parameter optimization. The proposed scheme is shown to provide a good trade-off relation between complexity and performance and is verified in detail their improved performance.

Clock Synchronization for One-Way Delay Measurement: A Survey

In this paper we present the comprehensive survey on the clock synchronization algorithms, which should be considered for the measurements of the network delay. We categorize the clock synchronization algorithms into two basic types according to how they acquire synchronization between clocks, which are external source based schemes and end-to-end measurement based schemes. While external source based schemes are the synchronization methods using centralized time source such as NTP, GPS and IEEE 1588 to have global synchronization for all end hosts, end-to-end schemes obtain synchronization information through network measurements between end hosts. We briefly introduces some algorithms in both categories. However, we have focused more on the end-to-end schemes which can be classified again into online and offline shemes according to whether they can be applied for real time operation. We survey the recent progresses on these end-to-end algorithms and special concerns are on the estimation of true the one-way delay without the effect of clock skew. The problems in depolying each end-to-end scheme are also described. The potential further research issues in online one-way delay estimation are discussed.

A fast LUT predistorter for power amplifier in OFDM systems

We proposed a new predistortion scheme that result in a last convergence performance by using a gradual quantization on input signal value from rough to fine. We compare the performance of the proposed scheme to conventional methods. Simulation results of the OFDM system on an AWGN channel reveal that the proposed method show improved convergence performance without any loss in accuracy.

Analysis of the Rain fading channel and the system applying MIMO

The aim of the research is to increase the capacity of the satellite communication in rain fall environment. Therefore, the paper analyzes and implements the rain fading channel model, and then applies results of analysis to proposed satellite MIMO system. The proposed system is composed of two satellites. A comparison between Rayleigh and Morita model is also treated. We can insist that the rain fading channel has better condition than Rayleigh model, and performance of proposed MIMO system is substantially good comparison with the existing satellite system

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

Reduced order RLS polynomial predistortion

In this paper, a modified recursive least square (RLS) based polynomial predistortion algorithm is proposed by reducing the order of the polynomials used in the RLS algorithm. The basic idea of the reduced order RLS based polynomial predistortion algorithm is to approximate the target function with two simpler functions (with a smaller number of coefficients) instead of a single function. A complex function is decomposed into two simpler functions so that we can compute the RLS algorithm with much less complexity. The proposed reduced order RLS polynomial predistortion shows superior performance compared to the conventional RLS polynomial predistortion with the same number of coefficients or with the same computational complexity.

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

Stereo image coding with disparity compensation using dynamic programming

In this paper, we propose a disparity estimation and stereo compression method based on dynamic programming. We introduced an occlusion indicating parameter to the cost function to take into account discontinuity and occlusion. For occluded area, occluded points are coded independently and non-occluded points are fed into the dynamic programming to find disparity vectors. Since the proposed method provides a more realistic disparity vector field and increased coding efficiency, improved picture quality can be obtained.

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.

Practical vertical handover mechanisms between satellite and terrestrial networks

In this paper, we propose practical vertical handover mechanisms for interworking between satellite and terrestrial network, which include new handover procedures and TCP congestion control. To support seamless handover, it should be considered L2-L4 layer operation all together. The proposed mechanisms include a vertical handover procedure using IEEE 802.21 and a TCP performance enhancing mechanism by adopting efficient congestion control scheme. IEEE 802.21 standard provides unified event messages from link layer to upper layer for helping seamless handover regardless whatever the physical layer interfaces are. The proposed TCP congestion control uses TCP Explicit Handover Notification which informs TCP sender directly of new available link bandwidth. We used ns-2 network simulator to evaluate our proposed mechanisms. Simulation results show that our mechanism can support a seamless handover and provide a better Internet service for fast train when there are different types of access networks such as a satellite and terrestrial network.