In this paper, channel estimation for Spatial Multiplexing (SM) is investigated for MIMO-OFDM system. Due to the channel characteristic of the transmission system is always changed by the time and its importance in wireless transmission to reconstruct the transmitted signals, the channel needs to be known as well as possible. Pilot symbols are used to gather knowledge about the channel and try to estimate it. The channel estimation based on the pilot symbol is called pilot aided channel estimation. In this research, Least Square (LS) method was chosen for initial channel estimation. By using applicable proposed system design, channel state information is estimated through the use of channel information before in subcarriers with no pilot symbols. Zero forcing (ZF) algorithm is used to detect and separate the received signal. The result shows that channel estimation would be better by increasing SNR. Normalized Mean Square Errror (NMSE) value of the channel reached 5xlO· 5 for SNR 25 dB. The value of BER reached 3xlO· 4for SNR 25 dB. The estimated channel capacity has the values that closed to the known channel capacity.

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The development of telecommunications technology continues to increase, especially in the use of cellular communication networks. Users of cellular networks today need high-speed communication to be able to enjoy the facilities offered such as streaming video, web browsing, e-mail and others. With the current increase in user capacity, it causes a lot of interference. Therefore, the use of modulation techniques needs to be considered. To find out the proper use of modulation, in accordance with the conditions of the region and the network used, this study examines the performance of variations in modulation levels, namely QPSK, 16QAM, 64QAM and 256QAM. The parameters measured in this study include RSRP, CINR, BER, user connected and throughput. Based on the coverage by RSRP simulation results, it was found that the RSRP did not change because the power signal will always adjust to any use of the modulation level. For coverage by CINR obtained to obtain a higher rate value, a higher CINR value is needed and for coverage by BER parameters, BER does not affect the bit per symbol carried by each modulation, only affects the different types of modulation. Meanwhile, in the capacity by Throughput parameter, QPSK modulation produces the lowest average throughput value of 14.01 Mbps followed by 16QAM 21.58 Mbps 64QAM 28.6 Mbps and 256QAM 33.87 Mbps. In addition, for the capacity by user connected parameters all connected users on all modulation used will produce 100% for capacity by user connected.

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The development of communication services in remote rural areas is difficult to use cable-based systems such as Digital Subscriber Line (DSL) and FTTx. One solution to solve this problem is to use a wireless system such as radio communication. Free Space Optic (FSO) communication system is a better choice compared to radio communication because of the flexibility of frequency usage. One of the problems of the FSO communication system is the range not too far. The range of the FSO can be increased by using the space diversity method. This study compared FSO systems that not use space diversity and FSO systems that use space diversity in three weather conditions, namely clear, haze, and fog. In taking data results using Kim model propagation with variations in the range between 100 – 2000 meters. The modulation used in this study is external modulation. The result of the analysis of FSO performance after adding space diversity, the range of FSO increases as far as 1200 meters when the condition is clear. During the haze condition, the FSO range increase as far as 800 meters. During the fog condition, the FSO range has increased as far as 300 meters. By adding space diversity, the Q-factor value has increased, and BER (Bit Error Rate) has decreased.

High speed data transmision demands broader bandwidth. This has an effect towards the limitation of frequencies spectrum allocation as well as interference. To solve this, multi carrier modulation is one of choices. Having better power spectral density compared to OFDM, the FBMC-OQAM has been chosen as the multi carrier modulation. The FBMC is equipped with Poly Phase Network filter, makes it able to achieve better PSD. Frequently used filter, which is pre-emphasis, is popular in speech processing that is possibly able to be extended in use. Pre-emphasis is also accompanied with de-emphasis filter, which is similar to FBMC. Pre-emphasis filter suppresses low frequency magnitudes and emphasizes higher frequency. By assuming that noise presents in higher frequency, an approachment to protect audio signal by itself is proposed. Random noise is broadband signal where frequencies can have ranges from lower to higher with smaller magnitudes compared to signal. By providing slots in audio higher frequency and magnitudes, random noise occupied those slots with relatively weak magnitudes then sent through the air. At the receiver, a deemphasis filter invert the process to restore signal by deemphasizing higher frequency and removing noise as well. The result shows better BER with this approachment. For example, when Eb/No was 13 dB, BER with and without pre-emphasis are approximately 0.0184 dB and 0.0187 dB, consecutively. It means there was 250 bits or approximately 32 points has been corrected. It shows that pre-emphasis can work along with PPN FBMC filter to gain better BER values. Intisari-Transmisi data berkecepatan tinggi membutuhkan bandwidth yang lebih lebar. Hal ini berdampak pada terbatasnya alokasi spektrum frekuensi dan interferens. Solusinya adalah dengan menggunakan modulasi multi-carrier. Modulasi FBMC-OQAM dipilih sebagai modulasi multi-carrier yang memiliki power spectral density (PSD) lebih baik daripada OFDM. Modulasi ini menggunakan filter poly phase network sehingga PSD lebih baik. Filter pre-emphasis sering digunakan dalam pengolahan sinyal wicara dan diperluas penggunaannya dalam makalah ini.Filter pre-emphasis dilengkapi dengan filter de-emphasis yang identik dengan skema FBMC. Filter ini menekan magnitude pada frekuensi rendah dan memperkuat frekuensi tinggi. Dengan asumsi derau berada pada frekuensi tinggi, sebuah pendekatan untuk melindungi sinyal audio oleh dirinya sendiri ditawarkan. Derau acak (random noise) adalah sinyal broadband yang frekuensinya mulai dari terendah hingga tertinggi, tetapi magnitudenya lebih rendah daripada sinyal audio. Dengan menyediakan ruang spektrum pada frekuensi tinggi sinyal audio yang memiliki magnitude tinggi setelah proses pre-emphasis, derau akan masuk, tetapi magnitudenya rendah, lalu dikirimkan. Pada sisi penerima, filter de-emphasis akan mengembalikan sinyal audio dengan menekan frekuensi tinggi, yang berarti juga menekan derau. Hasil simulasi menunjukkan nilai BER yang semakin baik. Sebagai contoh, untuk Eb/No 13 dB, nilai BER dengan dan tanpa pre-emphasis...