In-Woong Kang

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.

Simplified log likelihood ratio calculation in soft ordered successive interference cancellation for multiple-input multiple-output digital video broadcasting-second generation terrestrial receivers

This study proposes a soft ordered successive interference cancellation (OSIC) receiver accompanied by a simplified log-likelihood ratio calculation method for a dual-polarised multiple-input multiple-output (MIMO) digital video broadcasting-second generation terrestrial system. The future terrestrial transmission systems will be required to provide high data rates for ultra-high definition television service. For this purpose, dual-polarised MIMO techniques with a little cross-antenna interference and high-order modulation schemes have been considered. As the cross-antenna interference needs to be removed, a soft OSIC receiver can be used effectively. However, the receiver has to endure high computational complexity for calculating soft values. To reduce it, the authors simplified the calculation based on the decision threshold (DT) method. The main contribution of this study is to extend the conventional DT method, which is restricted to only low-order modulations, to an algorithmic process applicable to any modulation order. The proposed soft OSIC receiver has about 1 dB degradation from the soft OSIC receiver with the maximum-likelihood calculation of soft values. The degradation can be fully rewarded by the significantly reduced computational complexity. Furthermore, this study presents an additional possibility of improving the decoding performance by modelling the OSIC equaliser as a biased estimator.

Low-Complexity LLR Calculation for Gray-Coded PAM Modulation

Higher-order modulation schemes are employed to improve the spectral efficiency in modern communication systems. However, the conventional Max-Log-MAP symbol-to-bit demapper suffers from a large computational burden. To cope with this problem, this letter proposes a novel log-likelihood ratio computation algorithm for Gray-coded higher-order pulse-amplitude modulation (PAM). The proposed method reduces the order of complexity from O(2M) to O(M) without any difference of the LLR values compared with the Max-Log-MAP demapper, where M is the number of bits in one PAM symbol. Moreover, it is also shown that the proposed algorithm achieves superior complexity reduction compared with a recently proposed low-complexity demapper.

A MIMO DVB-T2 system with a newly designed bit mapper for UHDTV broadcasting

We propose a design methodology of a bit mapper based on the extrinsic information transfer (EXIT)-chart analysis for the dual-polarized multiple-input multiple-output (MIMO) digital video broadcasting-2nd generation terrestrial (DVB-T2) system. The proposed methodology reduces the design complexity and the simulation results show that newly-designed bit mappers outperform over the conventional bit mapper in the DVB-T2 specification under a MIMO fading channel.

Design of a bit interleaver for the high-order constellation DVB-T2 system

Since the DVB-T2 system provides high spectral efficiency among commercialized digital terrestrial transmission (DTT) systems, it has been considered as a prospective option for the base system of next generation DTT systems providing UHDTV service. However, when the high order modulation scheme such as 1024-QAM is employed, a bit interleaver in DVB-T2 should be newly designed. The design of a bit interleaver aims to improve the decoding performance not only by obtaining time diversity gain but also by eliminating multi-edge symbols. Although there are a few literatures about the design of a bit interleaver exploiting the multi-edge elimination, they cannot be directly applied to the bit interleaver of the DVB-T2 because they work as a group with a bit-to-cell demultiplexer. In this respect, this paper presents a bit interleaver design procedure for the high-order constellation DVB-T2 system. The proposed procedure generates bit interleavers for any modulation orders and makes it possible that a newly designed bit interleaver performs multi-edge elimination with all the LDPC code rates. Simulation results show that a newly designed bit interleaver for 1024-QAM achieves about 0.6dB SNR gain over a random interleaver under a Rayleigh fading channel.

Performance evaluation of the MIMO bit mapper of the DVB-T2 dual-polarized MIMO system

In this paper, a MIMO bit mapper structure is introduced and its bit error rate performance is evaluated. As the amount of the required transmission data rate of the future broadcasting service, such as UHDTV, is much greater than that of the current digital terrestrial transmission (DTT) system, the dual-polarized MIMO system is expected to be equipped for higher data rate in the future generation of the DTT system in order to overcome the shortage of the data rate of the conventional terrestrial broadcasting system. Accordingly, this paper presents the effect of the MIMO spatial multiplexing on the conventional DTT system by introducing a MIMO bit mapper and providing analysis of its BER performance according to different MIMO bit mapping cases.

A reduced-complexity demapping algorithm for gray-labeled PSK constellations

This paper proposes a novel symbol-to-bit demapping algorithm for Gray-labeled phase shift keying (PSK) constellations. Unlike the Max-Log-MAP demapper, the proposed algorithm does not perform exhaustive search operations, but directly computes the soft information by exploiting the binary search and the symmetry of the Gray-labeled PSK constellations. Hence its complexity is remarkably reduced from the order of O(2m) of the Max-Log-MAP to O(M), where M denotes the number of bits per symbol. A pair of recent methods are used as bench markers in this paper. One of them reduces the complexity without any performance loss, while the other is a recursive method that reduces the complexity by approximating the original bit metric. It is shown that the proposed algorithm achieves a more substantial complexity reduction than the former bench marker. The proposed algorithm achieves a similar complexity reduction to the latter bench marker and yet, it does not suffer from any performance degradation.

A dual-polarized MIMO system based on DVB-T2 for UHDTV transmission

Serving a huge data rate of the ultra-high definition television (UHDTV) standard requires an enhancement of the transmission data rate of the conventional digital terrestrial transmission (DTT) systems. In order to improve the data rate, adopting dual-polarized MIMO techniques and higher order modulation schemes has been spotlighted. However, there are only few performance evaluations of the system in literature. In this respect, as one of possible candidates for UHDTV transmission, we implement a dual-polarized MIMO system based on the digital video broadcasting-2nd generation terrestrial (DVB-T2) and investigate its performance with various combinations of parameters.