Sungmoon Yeo

A satellite radio interface for IMT-Advanced system using OFDM

In this paper, we introduce a new satellite radio interface technology to provide efficient IMT-Advanced services. Maximizing the commonalities with the terrestrial system is one of the most important factors for cost-effective service delivery, which will finally bring successful deployment of the system. For this purpose, we adopt an OFDM based radio interface. At the same time, the interface should be tailored in order to compensate a long round trip delay of satellite systems. In this paper, we present a number of satellite specified techniques which was developed for this purpose, including frequency reuse technique, uplink synchronization technique, random access technique, and interleaving technique combined with adaptive modulation and coding.

Adaptive modulation and coding for Long Term Evolution-based mobile satellite communication system

SUMMARY The adaptive modulation and coding (AMC) scheme is mandatory for modern wireless communication systems to overcome inevitable channel impairments. Many of the limitations using AMC are due to the long round-trip delay of a satellite system. This paper proposes an efficient AMC scheme with power control and symbol interleaving that can be effectively applied to satellite systems. In particular, we focus on mobile satellite systems that have maximum compatibility in a Long Term Evolution system. Simulations reveal that the proposed scheme can provide a maximum 10.2% increase of average beam spectral efficiency and a maximum of 8-dB power gain compared with a conventional AMC scheme. Copyright

Efficient utilization of an adaptive modulation and coding for mobile satellite systems using LTE-Advanced

One of the most important features of the IMT-Advanced system is to utilize adaptive modulation and coding (AMC) in order to counteract time and/or frequency varying channel conditions. Due to increasing importance of integrated satellite and terrestrial networks, a satellite system specification needs to be designed by considering compatibility with terrestrial systems. In this paper, we propose an efficient utilization of AMC scheme for mobile satellite systems compatible with the LTE-Advanced. Due to a long round-trip delay (RTD) of a satellite system, the adaptation strategy of a satellite system should be quite different from that for the terrestrial system. In our scheme, a variable margin is allocated along with AMC in a comparatively slow fading condition such as open environment, while a long time interleaver is utilized along with AMC in a comparatively fast fading condition such as sub-urban area.

Design of long time interleaver for future S-DMB services

In this paper, we present an efficient interleaver, designed for future personal mobile satellite services. Burst errors incurred by long term fading of mobile satellite channels will seriously degrade the service quality. Interleaving is an effective solution to this situation, by randomizing the errors before the channel decoders. This paper describes the design and the simulation results of a convolutional interleaver for personal mobile satellite system based on orthogonal frequency division multiplexing (OFDM) transmissions, especially IEEE mobile WiMax specification. We first analyze long term fading characteristics of mobile satellite channels, and analyze the simulation results of bit error rate (BER) performance according to various system parameters and channel conditions.

SNR Estimation for DVB-S2 System

[Abstract] This paper proposes an efficient signal to noise ratio (SNR) estimation method, especially costumed to the second generation digital video broadcasting via satellite (DVB-S2) system. The proposed method estimates SNR by investigating the distributions of the received signals. The hardware structure of the proposed estimator requires just a couple of comparators and counters, and thus the complexity is extremely low. The estimator satisfies the estimation ranges defined in the DVB-S2 system, and it requires about few hundreds of samples for average estimation error of about 1dB. In order to satisfy the accuracy performance of 1dB defined in the system, the estimator requires about two thousand samples when SNR is larger than 10 dB.

A Simple Hardware Structure for SNR Estimation

In this paper, we present an efficient hardware structure to estimate signal to noise ratio (SNR) for M-ary amplitude and phase modulation schemes at the receiver. The proposed hardware structure requires a counter and two comparators with a predetermined look up table (LUT). For an estimation error of less than 1 dB, it needs just about a few hundred samples. We can design the LUTs with theoretically derived values and tailor them for special purposes. We demonstrate a few simulation results of the estimation algorithm, and present hardware implementation results.

Estimation of the error performance objectives for satellite communication systems

We consider the physical layer error performance parameters and design criteria for digital satellite systems established by ITU-R Recommendation S.1062, where the performance objectives are given in terms of the bit error rate (BER) divided by the average number of errors within a cluster. It is well known that errors on satellite links employing forward error correction (FEC) schemes tend to occur in clusters. The resulting block error rate is the same as if it was caused by randomly occurring bit errors with an error-event ratio of BER/α, where α is the average number of errors within a cluster. The factor, α, accounts for the burstiness of the errors and also represents the ratio between the BER and the error-event ratio. This paper proposes theoretical methods to estimate the factor, α. Using the weight distributions of the FEC codes, we derive a set of expressions for the factor, α, as well as their compact lower bounds. We present lower bounds for various FEC schemes including binary BCH codes, block turbo codes, convolutional codes, and turbo codes. The simulation results show that the proposed lower bounds are good estimates in the high signal-to-noise ratio region. Copyright

ITU-R Standardization of Digital Performance for Fixed Satellite Services

This paper presents recent ITU-R standardization activities on digital performance for fixed satellite services. Recently, a few new research results on the error performance objectives and efficient digital transmission techniques including adaptive transmissions have been reported and they are now reflected to revise ITU-R Recommendations. In this paper, we summarize these activities by detailing the backgrounds and various examples. In addition, we briefly report other related standardization activities and future works under studying.