Rina Pudji Astuti

The performance analysis of multiuser WCDMA systems using D-STBC in Rayleigh fading channel

The development of wireless communication systems is focusing to provide a link with a high capacity and good quality. The multi-hop communication system using relays diversity with a reliable coding is designed to fulfil the above requirements. Using multi-user WCDMA system, this research applies the above multi-hop technique using a relay with Alamouti code which can be defined as Distributed-Space Time Block Code or D-STBC. Therefore it does not need multi antenna but act like MIMO and that is why it is also called virtual MIMO using a cooperative multi-hop system. The simulation results show that the 2×1 virtual MIMO multi hop system performs better than a single hop system. Targeting BER of 10-3, the multi hop system give 12 dB gain compared with a single hop system.

A Novel MC-CDMA Multilevel Coding Scheme on High Data Rate MIMO-Wireless Communication Systems

Wireless broadband access system will operate in high mobility and high data rate environment It is necessary to consider a system that is applied with or without perfect channel information, having more spectrum efficiency, and mitigating selective fading problems. We propose an MC CDMA multilevel coding system model that capable to solve those problems. We consider to this system accommodate various bandwidth usage, QoS or channel response for every user. From the research results, it is concluded that in general the MC CDMA multilevel coding scheme will provide a good performance with high speed user in non coherent channel transmission scheme.

Optimum UAV flying path for Device-to-Device communications in disaster area

In this paper, we propose the usage of Unmanned Aerial Vehicle (UAV) as a flying mobile base tower station for discovering Device-to-Device (D2D) devices in the disaster area. In a disaster area, energy consumption of both devices and network become an important constraint. Therefore, there is a need to establish wireless network communication in large area rapidly under the condition of infrastructure failure. The previous works does not calculate the energy consumption of the UAV and consider the use cases of UAV flight path for specific disaster condition, e.g. flood, earthquake, etc. The objective of this paper is to provide UAV flying paths that can adapt according to disaster condition which satisfy the UAV energy constraint. We enhance four schemes for the UAV flying paths: O-path, Rectangular path, ZigZag-path, and S-path. This enhancement reduces the flight path gap area and lead the increasing of covered area. To examine the best UAV flight path for certain disaster cases, several simulations were performed and discussed. The results show that for distributed damage pattern, the optimum UAV flying pattern is an S - path because of its large coverage area (covering around 80 percent of total devices in altitude 100 m). Otherwise, for centralized damage pattern, the optimum UAV flying patterns are O, Rectangular, and Zigzag path because of its short flight duration and less energy consumption (eight times smaller than the S - path in altitude 100 m).

Dual polarized antenna decoupling for 60 GHz planar massive MIMO

Millimeter-wave (mm-Wave) Massive Multiple Input Multiple Output (MIMO) at 60 GHz is a candidate of advanced wireless communications for indoor environment. Mm-Wave massive MIMO antenna with lower frequency with sectoring technique has been proposed in previous research. Also dual polarized configuration for MIMO in lower frequency and lower number of antenna. Massive MIMO at 60 GHz mm-Wave is not evaluated yet in these previous research. In this paper, dual polarized mm-Wave massive MIMO has been proposed. Antennas are modeled in circular disk proximity coupled planar array. Bandwidth of dual polarized configuration is 4.349 GHz, wider than 4.303 GHz in single polarized configuration. Envelope Correlation Coefficient (ECC) of dual polarized configuration is 25 times lower compared to single polarized configuration. Dual polarized configuration shows better performance both in bandwidth and ECC compared to single polarized configuration.

Modeling of massive MIMO transceiver antenna for full-duplex single-channel system (in case of self interference effect)

Massive MIMO technology can increase capacity, data rate, and link reliability significantly without additional bandwidth or transmission power. Most of the previous study on Massive MIMO systems are using low frequency (2.6 GHz). This frequency is not suitable for future broadband technology, because IoT devices will use high frequency and possible cell coverage would be smaller. This work proposes Massive MIMO transceiver antenna that can be implemented in high frequency (60 GHz). This system provides broadband wireless communication which gives high capacity, high data rate and wide bandwidth. In this works the number of antennas is 64×64. Antennas can be set adaptively to capacity. In this case all of the antennas as a receiver are functioned to get redundancies and 32 antennas as transmitter adjusted to the required capacity. Configuration of antenna has been set to eliminate the mutual coupling effect. The system utilizes full duplex single channel (FDSC) which use the same frequency and time to transmit and receive data. In FDSC, bandwidth can be minimized, but self interference effect appeared and disturbing the system performance of Massive MIMO. The effect of self interference for Massive MIMO transceiver antenna simulated from 10% to 100%. The proposed system provides the channel capacity ≈ 390 bits/s/Hz or ≈ 39× spectral efficiency of SISO system. The simulation result shows that mutual coupling effect ≈ 0. The Massive MIMO have a tolerance of 20% self interference effect, however it could decrease 20% channel capacity as well.

A multiuser interference mitigation scheme in uplink MC-CDMA with CFO Estimation-MMSE FEQ technique

In the uplink system, different carrier frequency offsets (CFO) of different users at the receiver resulting multiuser interference (MUI) and thus degrade the performance of Multicarrier Code Division Multiple Access (MC-CDMA) system. In the previous study, Modified Minimum Mean Square Error Frequency Domain Equalization (Modified MMSE-FDE) has been proposed by Agnihotri which results in a better performance than the conventional MMSE. However, the achieved Bit Error Rate (BER) is not smaller than 10−2 for Signal to Noise Ratio (SNR) below 20. This paper proposed a new algorithm to improve Modified MMSE-FDE performance in mitigating multiuser interference (MUI) in single cell MC-CDMA system, that is called as Carrier Frequency Offset Estimation-Minimum Mean Square Error Frequency Domain Equalization (CFO Estimation-MMSE FEQ). CFO Estimation-MMSE FEQ takes into account the rest of MUI as well as Modified MMSE-FDE to design equalization coefficient, but CFO Estimation-MMSE FEQ uses CFO estimation that is not on Modified MMSE-FDE. The value of CFO is estimated and regenerated in the receiver and then used to estimate MUI. In order to get signal processing more efficient, CFO Estimation-MMSE FEQ only takes the real trace of equalization coefficient matrix. MC-CDMA with CFO Estimation-MMSE FEQ has better performance than MC-CDMA with Modified MMSE-FDE. However, the complexity of CFO Estimation-MMSE FEQ is higher than Modified MMSE-FDE. By taking only the real trace of equalization coefficient matrix, the complexity of CFO Estimation-MMSE FEQ is getting simpler than taking the whole of equalization coefficient matrix. Furthermore, CFO Estimation-MMSE FEQ that takes only the real trace of equalization coefficient matrix is 2.9 % more efficient than CFO Estimation-MMSE FEQ that takes the whole of equalization coefficient matrix.

PERBANDINGAN POWER SPECTRAL DENSITY SISTEM OWDM DAN OFDM PADA KANAL RAYLEIGH

OFDM (Orthogonal Frequency Division Multiplexing) merupakan teknik modulasi multicarrier untuk mengatasi permasalahan kanal multipath seperti frekuensi selektif fading. Orthogonalitas pada sistem OFDM menghasilkan banyak sub-carrier yang dapat ditransmisikan secara bersamaan pada spektrum frekuensi yang terbatas tanpa saling berinterferensi. Efesiensi bandwidth didapat karena masing-masing sub-carrier saling orthogonal sehingga antara sub-carrier yang berdekatan dapat dibuat overlapping. OWDM (Orthogonal wavelet division multiplex) merupakan suatu sistem multicarrier alternatif dariOFDM dan telah diteliti sebagai kandidat yang dapat diaplikasikan pada wirelesscommunication. Sistem OWDM menggunakan Inverse Discrete wavelet transform (IDWT) sebagai pembangkit subcarrier-subcarrier yang saling orthogonal dan berfungsi sebagai modulator. Sedangkan DWT (Discrete Wavelet Transform) digunakan sebagai demodulator. Penelitian ini membandingkan power spectral density dari sistem OWDM dan OFDM. Dari hasil simulasi perbandingan power spectral density (PSD) didapatkan bahwa PSD darimasing-masing sistem sama. Pada OWDM, pembagian band frekuensi untuk setiap sub-band berbeda kecuali sub-band pada level yang sama. Semakin tinggi level sub-band maka semakin lebar band frekuensinya.

Scaling technique of triple play services in passive optical network using subcarrier allocation algorithm

Data consumption increased sharply, all triple play services such as Voice, Data-Internet & Video can be performed on one communication path, even fiber optic has also bandwidth limitations, previous studies tried to maintain the fairness among the users, but there is no fairness of service therefore the allocation of data transmission must be optimized as their needs. A Passive Optical Communication in downstream direction are presented. We proposed to modify current burst methods to scheduling distribution SC on system OFDM from OLT to ONU by utilize FDMA to allocating SubCarrier based on the services are applied. Significant gain of bandwidth efficiency up to 60% obtained when link is being congest.

Enhancement of MC-CDMA performance system using Rotated Modulation

The transmission system with high data rate and high mobility is needed. However, the system is susceptible to frequency selective fading and fast fading. We propose MC - CDMA system with Rotated Modulation that be able to solve the problems. MC - CDMA is a combination of OFDM and CDMA system which offer high spectral efficiency. However, this system still requires high power, so in this study Rotated Modulation is added to reduce the power. Rotated Modulation implements rotating signal constellation and use quadrature and inphase interleaver. The simulations result show MC - CDMA with Rotated Modulation produce a system that require less power compared with MC-CDMA non Rotated Modulation systems.

Utilizing mean greedy algorithm using user grouping for chunk allocation in OFDMA systems with carrier aggregation

In this paper, utilizing user-order chunk allocation algorithm for OFDMA systems using carrier aggregation environment is proposed and evaluated. Chunk allocation algorithm is performed based on mean greedy algorithm which has low complexity. In order to adopt this algorithm to those system, all users are divided into a certain group in accordance with the number of available aggregated carriers. The simulation results are shown that the performance and time complexity of the proposed scheme is same with the system without user grouping. Therefore, the proposed scheme could be considered to realize in LTE-Advanced platform.