• Journal of Communications and Networks
• /
• v.15 no.4
• /
• pp.362-369
• /
• 2013

The optimal number of users achieving the maximum sum throughput is analyzed in zero-forcing (ZF) based multiuser multiple-input multiple-output (MIMO) systems with a large number of base station (BS) antennas. By utilizing deterministic ergodic sum rates for the ZF-beam forming (ZF-BF) and ZF-receiver (ZF-R) with a large number of BS antennas [1], [2], we can obtain the ergodic sum throughputs for the ZF-BF and ZF-R for the uplink and downlink frame structures, respectively. Then, we can also formulate and solve the optimization problems maximizing the ergodic sum throughputs with respect to the number of users. This paper shows that the approximate downlink sum throughput for the ZF-BF is a concave function and the approximate uplink sum throughput for the ZF-R is also a concave function in a feasible range with respect to the number of users. The simulation results verify the analyses and show that the derived numbers of users provide the maximum sum throughputs for the ZF-BF as well as ZF-R in multiuser MIMO systems with a large number of BS antennas.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.7
• /
• pp.1291-1298
• /
• 2017

In this paper, we propose a decoding method that improves the transmission rate and reliability by integrating MIMO(Multiple Input Multiple Output) communication scheme using turbo code and FTN(Faster Than Nyquist) scheme among high rate and high reliability wireless communication schemes in wireless communication. The existing MIMO-FTN(Multiple Input Multiple Output-Faster Than Nyquist) scheme based on hierarchical space-time coded method induced data rate loss due to the application of the space-time trellis coding scheme to remove adjacent symbol interference due to FTN scheme. To solve these problems, this paper proposes a method using W-ZF(Weighted-Zero Forcing) which overcomes the disadvantages of ZF(Zero Forcing) scheme in MIMO-FTN scheme using ZF scheme. In this paper, we compared the performance and the transmission rate of the MIMO-FTN scheme based on the hierarchical space-time coding, the MIMO-FTN scheme using W-ZF and the SISO-FTN scheme. As a result, the MIMO-FTN scheme using the W-ZF scheme is two times better than the other two schemes.

• Journal of Advanced Navigation Technology
• /
• v.15 no.3
• /
• pp.392-404
• /
• 2011

In this paper, we address the issue of joint detection schemes for uplink cellular system when base station cooperation is possible for multi-user detection in multi-cell scenario. The ZF, ML, MMSE and SIC detection are analyzed and evaluated as a conventional scheme. ML attains the optimal performance but the complexity increases exponentially, ZF/MMSE have simple structure but have poor detection performance and SIC has better performance but it has large complexity and potential of the error propagation. However, they need the increased decoder complexity as the number of iteration is increased. We propose a new joint ML and ZF/MMSE detection scheme, which combines the partial ML decoding and ZF/MMSE detection, in order to decrease the decoder complexity. Simulation results show that the proposed scheme attains same or a little bit better BER performance and expect reduced decoder complexity, specially in the case of large number of Base Station are cooperated each other.

• ETRI Journal
• /
• v.38 no.2
• /
• pp.291-301
• /
• 2016

In this paper, we study an optimized block-diagonal zero-forcing (BD-ZF) precoder in a two-tiered cognitive network consisting of a macro cell (MC) and a small cell (SC). By exploiting multiuser multiple-input and multiple-output Vandermonde-subspace frequency-division multiplexing (VFDM) transmission, a cognitive SC can coexist with an MC. We first devise a cross-tier precoder based on the idea of VFDM to cancel the interference from the SC to the MC. Then, we propose an optimized BD-ZF intra-tier precoder (ITP) to suppress multiuser interference and maximize the throughput in the SC. In the case where the dimension of a provided null space is larger than that required by the BD-ZF ITP, the optimized BD-ZF ITP can collect all limited channel gain by optimizing rotating and selecting matrices. Otherwise, the optimized BD-ZF ITP is validated to be equivalent to the conventional BD-ZF ITP in terms of throughput. Numerical results are presented to demonstrate the throughput improvement of the proposed optimized BD-ZF ITP and to discover the impact of imperfect channel state information.

• Journal of Plant Biotechnology
• /
• v.36 no.1
• /
• pp.23-29
• /
• 2009

We have previously isolated a CCCH type zinc-finger protein gene, OsZF2 (Oryza sativa Zinc Finger 2), from the cold-treated rice cDNA library. To investigate the potential role of OsZF2, transgenic rice lines over-expressing OsZF2 under the control of CaMV 35S promoter have been developed through Agrobacterium-mediated transformation. Elevated level of OsZF2 transcripts was confirmed by RNA gel blot analysis in transgenic rice. Under the 100 mM NaCl condition, the transgenic rice showed significantly enhanced growth rate in terms of shoot length and fresh weight, implicating that OsZF2 is likely to be involved in salt response of rice. In the field condition, however, the transgenic rice showed a dwarf phenotype and flowering time was delayed. Genome expression profiling analysis of transgenic plants using the 20K NSF rice oligonucleotide array revealed many up-regulated genes related to stress responses and signaling pathways such as chaperone protein dnaJ 72, salt stress-induced protein, PR protein, disease resistance proteins RPM1 and Cf2/Cf5 disease resistance protein, carbohydrate/ sugar transporter, OsWAK kinase, brassinosteroid LRR receptor kinase, and jasmonate O-methyltransferase. These data suggest that the CCCH type zinc-finger protein OsZF2 is a upstream transcriptional factor regulating growth and stress responsiveness of rice.

• Journal of the Korea Computer Graphics Society
• /
• v.6 no.1
• /
• pp.29-36
• /
• 2000

In this work, we propose ZF-buffer algorithm in order to accelerate the intersection test of ray-tracing algorithm. ZF-buffer is used in the preprocessing of ray-tracing and records the pointer that points to a parent face of a depth value(z value) of an object determined in Z-buffer. As a result, the face which intersects with the first ray can be determined easily by using the pointer stored in F-buffer. Though ZF-buffer and vista-buffer resemble each other, the difference between the two methods is that what ZF-buffer records is not bounding volume but the pointer of a displayable face. We applied the ZF-buffer algorithm for the first ray to Utah teapot which consists of 9216 polygons. By comparing the elapse time of our method with vista-buffer algorithm, we can acquire improvement in speed that it is 3 times faster than vista-buffer algorithm. We expanded our algorithm to the second ray.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.4
• /
• pp.1-8
• /
• 2008

In orthogonal frequency division multiplexing (OFDM) system the time selectivity of wireless channel introduces intercarrier interference (ICI), which degrades system performance in proportion to Doppler frequency. To mitigate the ICI effect, we can generally employ a classical zero-forcing (ZF) equalizer. However, the ZF scheme requires an inverse of a large matrix, which results in prohibitively high computational complexity. In this paper, we propose a low complexity ZF equalization scheme for suppressing the ICI caused by highly time-varying channels in OFDM systems. From the fact that the ICI on a subcarrier is mainly caused by several neighboring subcarriers, the proposed scheme exploits a numerical approximation for matrix inversion based on Neumann's Series (truncated second order). To further improve performance, the partial ICI cancellation technique is also used with reduced complexity. Complexity analysis and simulation results show that the proposed scheme provides the advantage of reducing computational complexity significantly, while achieving almost the same performance as that of the classical ZF a roach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.11
• /
• pp.2145-2147
• /
• 2015

In this letter, we investigate the performance analysis of massive MIMO systems using MRT and ZF precodings according to the number of DoF. We analyze the ergodic received SINRs with MRT and ZF precodings as closed-forms over the number of DoF normalized by the number of antennas. In simulation results, we verify the analyzed results and observe that MRT precoding is better than ZF precoding in terms of the ergodic received SINR with a small number of DoF.

• ETRI Journal
• /
• v.44 no.1
• /
• pp.117-124
• /
• 2022

In this paper, the performance of precoding-aided differential spatial modulation (PDSM) systems with optimal transmit antenna subset (TAS) selection is examined analytically. The average bit error rate (ABER) performance of the optimal TAS selection-based PDSM systems using a zero-forcing (ZF) precoder is evaluated using theoretical upper bound and Monte Carlo simulations. Simulation results validate the analysis and demonstrate a performance penalty < 2.6 dB compared with precoding-aided spatial modulation (PSM) with optimal TAS selection. The performance analysis reveals a transmit diversity gain of (N_T-N_R+1) for the ZF-based PDSM (ZF-PDSM) systems that employ TAS selection with N_T transmit antennas, N_S selected transmit antennas, and N_R receive antennas. It is also shown that reducing the number of activated transmit antennas via optimal TAS selection in the ZF-PDSM systems degrades ABER performance. In addition, the impacts of channel estimation errors on the performance of the ZF-PDSM system with TAS selection are evaluated, and the performance of this system is compared with that of ZF-based PSM with TAS selection.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2002.11a
• /
• pp.169-174
• /
• 2002

It has known that the DCMP(Directionally Constrained Minimization of power)and the ZF(Zero Forcing) can improve the SINR performance of an array antenna system by using spatial signature of wireless channel. This paper analyzes performance of DCMP and ZF in multiple scattering environments. To obtain the spatial signature of wireless channel. bothe DOA(Directional of Arrival) and AS(Angular Spread) of the received signals were estimated by using ESPRIT. The performance of the DCMP and the ZF was analyzed theoretically. Through computer simulation, the SINR performance were evaluated.