Taejin Jung

New 4-dimensional constellation-rotation modulation method for DVB-NGH

This paper proposes a new 4-dimensional constellation-rotation (CR) method that uses two consecutive CR operations for the constellation of QAM signals. The computer simulation results show that the proposed method performs better than a conventional 2-dimensional CR method as both a channel code rate and an erasure ratio increase.

Design of New Quasi-Orthogonal STBC with Minimum Decoding Complexity for Four Transmit Antennas

A new Space-Time Block Code (STBC) achieving full rate and full diversity for general QAM and four transmit antennas is proposed. This code also possesses a quasi-orthogonal (QO) property like the conventional Minimum Decoding Complexity QO-STBC (MDC-QO-STBC), leadingg to joint ML detection of only two real symbols. The proposed code is shown to exhibit the identical error performance with the existing MDC-QO-STBC. However, the proposed code has an advantage in transceiver implementation since this code can be modified so that the increase of PAPR occurs on only two transmit antennas, whereas MDC-QO-STBC incurs a PAPR increase on all transmit antennas.

Cost-Effective Multicast Routings in Wireless Mesh Networks

In order to reflect multicast routing characteristics in wireless mesh networks, multicast routing metric is required for qualifying the multicast tree cost under wireless environments. We design a new multicast routing metric called the multicast-tree transmission ratio which quantifies the multicast tree cost, considering the link quality of wireless multicast channels as well as wireless multicast advantage. The multicast-tree transmission ratio represents the product of the multicast transmission ratios of all nodes in the constructed multicast tree. This paper proposes a wireless multicast routing which constructs the multicast tree by maximizing the multicast-tree transmission ratio in wireless mesh networks and extends the multicast routing in mesh networks with multiple gateways. The proposed wireless multicast routings show a higher delivery ratio and a lower average delay than the multicast routing minimizing the forwarding nodes in its multicast tree. In comparison with other multicast routings, simulation results show that the proposed multicast heuristics maximizing the multicast tree transmission ratio construct a cost-effective multicast tree in terms of its delivery ratio, average delay, and required network resources.

New Minimum Decoding Complexity Quasi-Orthogonal Space-Time Block Code for 8 Transmit Antennas

In this paper, a new full-rate space-time block code (STBC) possessing a quasi-orthogonal (QO) property is proposed for QAM and 8 transmit antennas. This code is designed by serially concatenating a real constellation-rotating precoder with the Alamouti scheme. The QO property enables a maximum likelihood (ML) decoding to only require joint detection of four groups of real symbols at a receiver. Hence, this code has an identical and greatly reduced ML decoding complexity with the conventional minimum decoding complexity QO-STBC (MDC- QO-STBC) and the Xians QO-STBC, respectively. Especially, the proposed QO-STBC is guaranteed to enjoy full diversity for general QAM unlike the existing MDC-QO-STBC presented for only QPSK. By simulation results, we show that the proposed code exhibits the identical and slightly degrade error performance with the existing MDC-QO-STBC for 4-QAM and the Xians QO-STBC for 4 and 16-QAM, respectively.

Design of New Minimum Decoding Complexity Quasi-Orthogonal Space-Time Block Code for 8 Transmit Antennas

In this paper, a new full-rate space-time block code (STBC) possessing a quasi-orthogonal (QO) property is proposed for QAM and 8 transmit antennas. This code is designed by serially concatenating a real constellation-rotating precoder with the Alamouti scheme. The QO property enables a maximum likelihood (ML) decoding to only require joint detection of four groups of real symbols at a receiver. Hence, this code has an identical and greatly reduced ML decoding complexity with the conventional minimum decoding complexity QO-STBC (MDC- QO-STBC) and the Xians QO-STBC, respectively. Especially, the proposed QO-STBC is guaranteed to enjoy full diversity for general QAM unlike the existing MDC-QO-STBC presented for only QPSK. By simulation results, we show that the proposed code exhibits the identical and slightly degrade error performance with the existing MDC-QO-STBC for 4-QAM and the Xians QO-STBC for 4 and 16-QAM, respectively.

A new spatial modulation scheme based on quasi-orthogonal sequences

In this paper, we propose a new spatial modulation (SM) scheme based on quaternary quasi-orthogonal sequences (Q-QOSs), referred to as Q-QOS-SM. Unlike an original SM scheme, the proposed scheme uses the indices of the Q-QOSs for mapping of input bits, resulting in two times more bits to be allocated to an antenna-selection part compared to the original SM. From simulation results, the Q-QOS-SM is shown to achieve much higher bit throughput than the existing SM and generalized SM schemes for all simulation cases.

New hardware-efficient ML detection for spatial modulation scheme

In this paper, we propose a new hardware-efficient ML decoding algorithm for a spatial modulation scheme which is basically constructed by serially concatenating maximum-ratio receive combiners with traditional slicers. With respect to complex multiplications, the new algorithm has a greatly reduced decoding complexity compared to the conventional one, especially, for higher-order modulation. This is mainly because the complexity of the slicer is practically negligible without regard to a modulation order.

New PAPR reduction method for spatial modulation using an unitary precoder

In this paper, a new peak-to-average power ratio reduction method for spatial modulation is presented. This is done by multiplying an unitary precoder to modulated signals so that total transmit energy is uniformly scattered into all transmit antennas. When using an ideal amplifier, the proposed method guarantees performance identical with the conventional scheme due to the orthogonality of the precoder with almost same decoding complexity. When using a nonideal amplifier, the proposed method is shown to exhibit significant performance improvement, especially, for high input-back-off and a large number of antennas.

Design of New Differential Space-Time Modulation Using Real Precoder

The conventional Zhu`s differential space-time modulation(DSTM) based on quasi-orthogonal design adopted a complex precoder in order to allow an independent joint detection of two complex symbols without any channel informations at a receiver. In this paper, by simply replacing the complex precoder used in Zhu`s DSTM with a real precoder, a new DSTM is presented for four transmit antennas. The real precoder enables the receiver to decode two real symbols pair separately, and thus the new DSTM has greatly reduced decoding complexity compared to the Zhu`s DSTM. By computer simulation results, the proposed scheme is shown to exhibit almost identical or improved error performance compared to the existing DSTMs.

New Delay Optimum Quasi-Othogonal Space-Time Block Codes with Full Spatial Diversity

In this paper, we propose a novel, systematic structure for quasi-orthogonal space-time block codes (QO-STBCs) achieving full rate for even number of transmit antennas over quasi-static Rayleigh fading channels. Especially, the new codes are delay optimal unlike conventional QO-STBCs and thus have a great advantage in ML decoding complexity at a receiver. In order to exploit full spatial diversity, we utilize a constellation rotation method and also examine optimal rotation angles through brute-force search for some cases of modulations and transmit antennas. Computer simulation results show that the proposed codes exhibit average error performance almost the same as or better than the existing QO-STBCs.