• Journal of Convergence for Information Technology
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• v.11 no.9
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• pp.1-7
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• 2021

Since recently only an auto-correlated superposition coding (SC) scheme for non-orthogonal multiple access(NOMA) has been investigated, this paper proposes a cross-correlated SC scheme for NOMA. First, we derive the closed-form expression of the sum rate of the proposed cross-correlated SC scheme. Then, numerical analyses demonstrate that the sum rate of the proposed cross-correlated SC scheme is larger than that of the conventional auto-correlated SC scheme. We also show that for the stronger channel gain user, the signal-to-noise ratio (SNR) gain of the proposed cross-correlated SC scheme is about 15, compared with the conventional auto-correlated SC scheme. As a result, the proposed cross-correlated SC scheme could be a promising technology for 6G ultra-reliable low-latency communications (URLLC).

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.611-616
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• 2021

This paper investigates the improved outage probability of correlated superposition coding(CSC)/non-successive interference cancellation(SIC) non-orthogonal multiple access(NOMA) scheme. For this, first, we calculate the outage probability of the conventional independent superposition coding(ISC)/SIC NOMA scheme. Then, simulations demonstrate that the outage probability of CSC/non-SIC NOMA improves greatly, with respect to that of conventional ISC/SIC NOMA. As a result, CSC/non-SIC NOMA schemes could be a promising technique in 5G networks, especially with such improved outage probability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.267-273
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• 2021

Non-orthogonal multiple access is the promised candidates in the next generation wireless networks to improve the spectral efficiency by superposing multiple signals. In general, the superposition coding is performed using the difference in channel gain between users based on the user's power allocation. However, when user pairs have the similar channel gain problem, NOMA can not be allowed in the scenario. To overcome this problem, phase rotation based NOMA is presented to increase minimum distance between superposed signals in the constellation point. This paper proposed a novel non-orthogonal multiple access based index modulation using phase rotation. The additional bits can transfer using the index bits that is allocated according to the activated state of the phase rotation. Simulation results are shown that bit error rate and achievable sum rate are better than conventional NOMA.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1029-1036
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• 2021

Recently it has been proposed that lossless 2-user non-orthogonal multiple access (NOMA) can be implemented without successive interference cancellation (SIC) via correlated superposition coding (CSC). However only the 2-user case was considered. Thus this paper proposes a lossless 3-user non-SIC NOMA scheme. This can be achieved via the 3-user CSC scheme. Simulations show that the lossless 3-user non-SIC NOMA scheme can be implemented over power allocation ranges of user-fairness.

• Journal of Korea Game Society
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• v.16 no.1
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• pp.51-62
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• 2016

This study tries to present a new perspective for the coding and coding education. Therefore, this study analyzes coding game as performative writing. First, coding as writing process has the mechanism of serial expansion and circulation by utilizing basic code blocks. And coding as writing process produces a meaning as unit operation that generate an emergent game play. Second, coding as performative writing displays the speaking and writing at the same time and is embodied in game play. Also, absence of failure and correction makes possible users to explore the problem area and to strengthen the problem-solving ability.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.44-51
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• 2008

In this paper, we propose a modified clipping scheme for iterative decoding of superposition coding system by losing less power than clipping scheme. Our proposed scheme in superposition coding system shows good performance in peak-to-average power ratio(PAPR) and system performance with the same Clipping Ratio especially in low Clipping Ratio case. Finally in order to alleviate the performance degradation due to clipping noises, we combine a soft compensation algorithm that is combined with soft-input-soft-output(SISO) decoding algorithms in an iterative manner proposed by [1][2]. Simulation results show that with the proposed scheme, most performance loss can be recovered.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.107-115
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• 1998

A multiplier bit-pair recoding technique derived from Booth algorithm is used as an effective method that can carry out a fast binary multiplication regardless of a sign of both multiplicand and multiplier. In this paper, we propose an implementation of an optical high-speed multiplier which consists of a symbolic substitution adder and an optical multiplication algorithm, which transforms and enhances the multiplier bit-pair recoding algorithm to be fit for optical characteristics. Specially, a symbolic substitution addition rules are coded with a dual-rail logic, and so the complement of the logic of the symbolic substitution adder is easily obtained with a shift operation because it is always present. We also construct the symbolic substitution system which makes superposition image by superimposing two shifted images in a serial connection and recognizes a reference image by feeding this superimposed image to a mask. Thus, the optical multiplier, which is compared with a typical system, is implemented to the smaller system by reducing the number of optical passive elements and the size of this system.

• Journal of Convergence for Information Technology
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• v.10 no.8
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• pp.7-14
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• 2020

In the fifth generation (5G) mobile networks, the mobile services require 100 times faster connections. One of the promising 5G technologies is non-orthogonal multiple access (NOMA). In NOMA, the users share the channel resources, so that the more users can be served simultaneously. There are several advantages offered by NOMA, such as higher spectrum efficiency and low transmission latency, compared to orthogonal multiple access (OMA), which is usually used in the fourth generation (4G) mobile networks, for example, long term evolution (LTE). In this paper, we compare the receivers for NOMA. The standard NOMA receiver, the non-SIC NOMA receiver, and the symmetric superposition coding (SC) NOMA receiver are compared. Specifically, it is shown that the performance of the standard receiver is the best, whereas the performances of the non-SIC receiver and symmetric SC receiver are dependent on the power allocation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.274-279
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• 2021

Since conventional massive antenna systems require too many RF chains, they have disadvantages of high implementation cost and complexity. To overcome this problem, hybrid precoding schemes have been proposed. But, they are still of high implementation cost and complexity because RF chains are connected to all antenna elements. In this paper, we consider massive MIMO systems with overlapped sub-array (OSA) structure and then, propose a hybrid precoding scheme. In the overlapped subarray structure, RF analog precoding matrix has a sparse structure where many elements of RF analog precoding matrix are zeros. Using this sparse property, we propose a GTP-based precoder design method for RF and baseband digital precoding. Through simulation, we show that the proposed scheme has more than 85% of the spectral efficiency of the fully-connected structure while having 20~30% of complexity of it.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.26-34
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• 2000

In this paper, we propose a 4kbps speech coder that combines the harmonic vector excitation coding with time-separated transition coding. The harmonic vector excitation coding uses the harmonic excitation coding in the voiced frame and uses the vector excitation coding with the structure of analysis-by-synthesis in the unvoiced frame, respectively. But two mode coding method is not effective for transition frame mixed in voiced and unvoiced signal and a new method beyond using unvoiced/voiced mode coding is needed. Thus, we designed a time-separated transition coding method for transition frame in which a voiced/unvoiced decision algorithm separates unvoiced and voiced duration in a frame, and harmonic-harmonic excitation coding and vector-harmonic excitation coding method is selectively used depending on the previous frame U/V decision. In the decoder, the voiced excitation signals are generated efficiently through the inverse FFT of harmonic magnitudes and the unvoiced excitation signals are made by the inverse vector quantization. The reconstructed speech signal are synthesized by the Overlap/Add method.