Titiek Suryani
Sepuluh Nopember Institute of Technology
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Publication
Featured researches published by Titiek Suryani.
international conference on telecommunication systems services and applications | 2012
Walid Maulana Hadiansyah; Titiek Suryani; Gamantyo Hendrantoro
A method of estimating the Doppler spread in Orthogonal Frequency Division Multiplexing (OFDM) systems, known as Phase Difference method, is described. Channel estimation is performed in time domain over several OFDM symbols, which popularly performed in frequency domain. Channel frequency responses are affected by AWGN and propagation delay, and Rayleigh fading distributed. As a result, Doppler spread estimation is useful to improve Channel Impulse Response (CIR) performance. Furthermore, estimation bias is analyzed and error correcting modified method is advised to reduce estimation precision. From simulation results, it can be concluded that the greater Doppler spread is, the smaller number of pilot symbols are needed to form a circle on the constellation diagram, and conversely. The range of normalized Doppler shift that can be estimated is 0.0117-0.2997. For SNR = 10-30 dB, the error is ± 64.72%, whereas for SNR = 40-80 dB SNR, the error is ± 35.81%.
international conference on information and communication technology convergence | 2011
Titiek Suryani; Gamantyo Hendrantoro
In mobile-to-mobile channels, the Doppler shift is affected by mobile terminal velocities of the transmitter and the receiver end. Hence, the Doppler frequency becomes very high if both terminals move very fast. In this condition, the channel will change rapidly and cause large inter-carrier-interference (ICI) in OFDM system. A channel estimation technique using piece-wise linear approximation has previously been developed for ICI mitigation technique employing frequency-domain-equalizer (FEQ). Unfortunately, this channel estimation technique is limited by normalized maximum Doppler shift of 0.2, below which a negligible error results. In this paper, the carrier-frequency offset (CFO) compensation technique is proposed to improve this ICI mitigation technique, so that linear channel estimation still works well although normalized maximum Doppler shift is larger than 0.2. The CFO compensation frequency f<inf>0</inf> that should be added depends on transmitter Doppler shift f<inf>d</inf> and has an optimal value, i.e. f<inf>0</inf> = 0.55f<inf>d</inf> for mobile-to-fixed channels and f<inf>0</inf> = 0.6f<inf>d1</inf> for mobile-to-mobile channels. The channel estimation using linear approximation technique can be applied with negligible error up to normalized Doppler spread f<inf>d</inf> = 0.4 (100 % higher than systems without CFO compensation) and the sum f<inf>dT</inf> = f<inf>d1</inf> + f<inf>d2</inf> higher than 0.4 for mobile-to-mobile channels that is inversely proportional to the ratio a = f<inf>d2</inf> / f<inf>d1</inf>. Furthermore, assuming f<inf>d1</inf> ≥ f<inf>d2</inf> for mobile-to-mobile channel, the BER performance increases significantly if CFO compensation is applied.
International Journal of Distributed Sensor Networks | 2014
Titiek Suryani; Gamantyo Hendrantoro
In mobile cooperative orthogonal frequency division multiplexing (OFDM) systems with amplify-and-forward (AF) relays, in which the source and relay terminals are moving, Doppler frequency might become very large due to the formation of double-hop channels, possibly causing very large intercarrier interference (ICI). Therefore, ICI mitigation technique capable of reducing the impact of high Doppler frequency is required. This paper reports the study of ICI mitigation technique that uses frequency domain equalizer (FDE) with improvements in three aspects, namely, better channel estimation using cubic-spline approximation, use of selection combining to utilize cooperative diversity in order to suppress ICI, and simple error correcting code with double interleaving to suppress errors due to residual ICI. By using the proposed ICI mitigation technique, error rate performance of mobile cooperative OFDM systems can be improved significantly. Even at high Doppler frequencies, error floors due to residual ICI can be decreased by up to two decades.
Fifth International Conference on Wireless and Optical Communications | 2017
Farah Afianti; Wirawan Wirawan; Titiek Suryani
Broadcast authentication is used to determine legitimate packet from authorized user. The received packet can be forwarded or used for the further purpose. The use of digital signature is one of the compromising methods but it is followed by high complexity especially in the verification process. That phenomenon is used by the adversary to force the user to verify a lot of false packet data. Kind of Denial of Service (DoS) which attacks the main signature can be mitigated by using pre-authentication methods as the first layer to filter false packet data. The objective of the filter is not replacing the main signature but as an addition to actual verification in the sensor node. This paper contributes in comparing the cost of computation, storage, and communication among several filters. The result shows Pre- Authenticator and Dos Attack-Resistant scheme have the lower overhead than the others. Thus followed by needing powerful sender. Moreover, the key chain is promising methods because of efficiency and effectiveness.
international seminar on intelligent technology and its applications | 2016
Septriandi Wira Yoga; Titiek Suryani; Suwadi
Wireless communication system has been progressed rapidly. Transmission schemes used for the delivery of data was created such the Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM). Moreover, both combined (MIMO OFDM) can obtain a satisfactory data transmission capability. Starting from the data speed, efficiency, and Quality of Service is satisfactory. However, MIMO OFDM is often troubled by Peak to Average Power Ratio (PAPR), are due to the use of the powerful amplifier with a wide dynamic range and process Analog Digital Converter (ADC) in WARP (Wireless Access Research Platform). One of the ways to reduce PAPR is to apply the techniques Partial Transmit sequence (PTS) which essentially perform differently on each sub-block treatment to reduce the PAPR of MIMO OFDM and not reduce BER performance on the system (like Clipping scheme). PAPR itself can cause interference and degradation of Bit Error Rate (BER). PTS in WARP use two antennas transmitter where each an antenna has PTS scheme. Many papers have been created for this problem. This paper will propose to apply simulation method (Matlab) to real condition of using the Wireless Access Research Platform (WARP). From implementation got good BER performance compared with and without PTS scheme. In this research found nonlinear distortion on WARP.
Jurnal Teknik ITS | 2016
Rizkha Ajeng Rochmatika; Titiek Suryani; Suwadi Suwadi
Sistem OFDM cocok digunakan sebagai solusi yang dapat memenuhi layanan komunikasi data kecepatan tinggi karena memiliki efisiensi bandwidth dengan performansi terbaik. Namun dalam implementasinya, sistem OFDM memiliki kelemahan yang disebabkan oleh tingginya nilai Peak to Average Power Ratio (PAPR) sehingga sinyal OFDM rentan terkena distorsi nonlinear yang disebabkan oleh adanya komponen RF power amplifier yang menyebabkan kompleksitas komponen Analog to Digital Converter (ADC) yang terdapat pada Wireless Open Access Research Platform (WARP). Nilai PAPR yang besar pada OFDM membutuhkan power amplifier dengan dynamic range yang lebar untuk mengakomodasi sinyal, apabila hal tersebut tidak terpenuhi maka menyebabkan distorsi nonlinear dan pada akhirnya menurunkan performansi OFDM. Oleh karena itu, untuk mengatasinya dibutuhkan suatu metode yang dapat mereduksi nilai PAPR salah satunya menggunakan metode PTS. Guna melihat unjuk kerja teknik PTS, maka pada penelitian ini dibandingkan dua skema antara sistem OFDM tanpa dan dengan teknik PTS menggunakan analisa pada bit error rate dan nilai CCDF. Dari hasil pengukuran menunjukkan bahwa implementasi kinerja teknik PTS mampu meningkatkan kinerja sistem OFDM saat terkena distorsi nonlinear, terlihat pada pengukuran dengan modulasi 16-QAM untuk gain 56 didapatkan peningkatan BER sebesar 95.98%. Sedangkan pada grafik CCDF terjadi penurunan nilai PAPR sebesar 34.17% untuk M=4.
international conference on information technology, computer, and electrical engineering | 2014
Rizadi Sasmita Darwis; Suwadi; Wirawan; Endroyono; Titiek Suryani; Prasetiyono Hari Mukti
In this paper, an implementation of MIMO 2×2 system using Alamouti algorithm on Wireless Open Access Research Platform (WARP) is presented. The performance of the proposed system is evaluated in terms of Bit-error-rate (BER) for different environments that are indoor and outdoor which of each have Line-of-Sight (LOS) and non-Line-of-sight (NLOS) conditions. Afterwards, in order to validate the capability of the proposed system, SISO and MISO systems are also implemented. By an experimental analysis, MIMO system with NLOS condition in both indoor and outdoor environments show better performance than MISO and SISO. Meanwhile, for the conditions of LOS in both indoor and outdoor environment, the performance of SISO system is better than MIMO and MISO. In the case of NLOS conditions, the performance of proposed system is also examined and compared in the both environments. In indoor environment, at transmit power -21.48 dBm, MIMO, MISO and SISO systems have BER value of each of 1.172×10-4, 1.146×10-1, and 0.2551, respectively. Finally, in outdoor environment, at transmit power -25 dBm, MIMO system achieves BER of 0 better than MISO and SISO which achieves BER of 3.1×10-3 and 0.21, respectively.
Journal of communications software and systems | 2013
Titiek Suryani; Gamantyo Hendrantoro
international seminar on intelligent technology and its applications | 2015
Titiek Suryani; Suwadi; Hasan; Septriandi Wira Yoga
2018 International Conference on Information and Communications Technology (ICOIACT) | 2018
Wahyu Pamungkas; Titiek Suryani; Wirawan