Performance Improvement of LeastSquares Adaptive Filter for High-Speed Train Communication Systems

The downlink communication channel from high-altitude platform (HAP) to high-speed train (HST) in the Ka-band is a slowly time-varying Rician distributed flat fading channel with 10-25 dB Rician K factor. In this respect, the received signal is mainly affected by the Doppler shift of the line-of-sight (LOS) link. In order to increase receiver performance, we propose to firstly compensate the Doppler shift of the received signal before least-squares (LS) adaptive filtering is pursued. Implementing the proposed method requires a priori knowledge of the time-varying phase of the LOS component. This is justified since signalling between the train and the controller exists such that the train velocity and location are predictable. Implementing the proposed method to the recursive LS (RLS) received beamforming algorithm shows reduction of mean square error (MSE) and bit error rate (BER)

Wideband and Multiband Antenna Design and Fabrication for Modern Wireless Communications Systems

One of the major challenges due to spectrum scarcity in modern wireless communication is on antenna design that can serve a non-contagious frequency spectrum. In this paper, wideband and multiband design approaches are proposed to produce antennas that can serve various wireless technologies using different frequencies from 2.3 to 6.0 GHz, covering WiFi frequencies at 2.4-2.48 GHz, 5,15-5,35 GHz and 5,725-5,825 GHz, as well as WiMax frequencies at 2.3-2.4 GHz, 2.495-2.695 GHz, 3.3-3.8 GHz, and 5.25-5.85 GHz. The wideband and multiband antenna were implemented on an 0.8 mm thick of FR4 epoxy dielectric substrate with permittivity εr="4".3. The return loss of 10 dB can be achieved for 2.3 to 6 GHz in wideband antenna, and a tripe band of 2.3-2.8 GHz, 3.3-3.7 GHz, and above 4.6 GHz in multiband antenna. The gain of both antennas increases almost linearly from 0 dB at 2.3 GHz to around 4.5 dB at 6 GHz, except for the stop band at 2.8-3.3 GHz which has a significant drop of gain, corresponding to the stop frequency band. Antenna radiation pattern is bidirectional at x-y plane and nearly omnidirectional at y-z plane, and shows a similar patern for both wideband and multiband design approaches

Joint Routing and Congestion Control in Multipath Channel based on Signal to Noise Ratio with Cross Layer Scheme

Routing protocol and congestion control in Transmission Control Protocol (TCP) have important roles in wireless mobile network performance. In wireless communication, the stability of the path and successful data transmission will be influenced by the channel condition. This channel condition constraints come from path loss and the multipath channel fading. With these constraints, the algorithm in the routing protocol and congestion control is confronted with the uncertainty of connection quality and probability of successful packet transmission, respectively. It is important to investigate the reliability and robustness of routing protocol and congestion control algorithms in dealing with such situation.  In this paper, we develop a detailed approach and analytical throughput performance with a cross layer scheme (CLS) between routing and congestion control mechanism based on signal to noise ratio (SNR) in Rician and Rayleigh as multipath fading channel. We proposed joint routing and congestion control TCP with a cross layer scheme model based on SNR (RTCP-SNR). We compare the performance of RTCP-SNR with conventional routing-TCP and routing-TCP that used CLS with routing aware (RTCP-RA) model. The analyses and the simulation results showed that RTCP-SNR in a multipath channel outperforms conventional routing-TCP and RTCP-RA

A 2.3/3.3 GHz Dual Band Antenna Design for WiMax Applications

A triangular-slot antenna with rectangular patch for 2.3/3.3 GHz WiMax applications has been implemented on DICLAD 527 substrate (relative permittivity εr = 2.5) with 1.524 mm of substrate thickness. A rectangular patch printed on one side of the substrate is fed by a 50 Ω microstrip line and acts as the frequency tuning stub, while the triangular slot is positioned on the opposite side of the substrate, center lined to the rectangular stub. From the measurement results based on VSWR = 2 or equal to the return loss of 9.53 dB, at the lower band of 2.3 GHz the resulting impedance bandwidth is 290 MHz (from 2.16 to 2.45 GHZ) and at the upper band of 3.3 GHz is  370 MHz (from 3.31 to 3.68GHz), providing services for 2.3 GHz and 3.3 GHz frequency bands allocated for WiMax applications. The antenna gain measurement at 2.3 GHz frequency band is almost agrees with the simulation result of 3.2 dBi. While at 3.3 GHz the gain is approximately 4.4 dBi and continues to decrease with increasing frequency. The antenna gain measurement achieves maximum of 4.8 dBi (6 dBi from simulation) at about 3 GHz. The simulation and measurement results are evaluated and discussed

Layering of CDMA Wireless Sensor Network Cluster to Improve Network Capacity

Nowadays, the network capacity of the wireless sensor network is a critical research topic area in the world. As the number of sensors connected to the network is quickly growing, it is important that they can sense and transmit data instantly. One of the approaches to increase the network capacity is clustering the sensors to control communication. The approach will divide sensors into several groups and drive the sensors to send the data through the cluster head.  However, the approach will arise inter-cluster interference problems from the sensors near the border that is higher level than other sensors. All of those will cause the fewer sensor that can send the data so that reducing the network capacity. In order to overcome the problem, layering the sensor cluster is proposed which each cluster is divided into two layers.  Moreover, the outer layer is divided into four zones and assigned one intermediary sensor in each zone. Sensors in the outer layer will communicate with the cluster head through the intermediary sensors. The method will reduce the transmission power and lessen the interference to other clusters. The approach not only can minimize interference coming from the sensors near the outer layer but also reduce the power consumption. The study concludes that applying the layering technique will drive the sensors near the border to generate minimum interference in their cluster and neighbor clusters. As a result, the network can deliver more capacity than approaches using either only clustering or layering

Realization of a Second Harmonic Antenna for Rural Communications*

In this research, an active antenna operated at the second harmonic frequency is investigated, and is implemented using microstrip antenna material. The antenna consists of a FET oscillator which plays as a fundamental frequency oscillator and a frequency multiplier, and a patch antenna resonated at the second harmonic frequency as the radiator. A maximum second-harmonic output power can be extracted when the load impedance of the oscillator is optimized both at the fundamental and at the second harmonic frequencies. A rectangular patch antenna is used to radiate the second harmonic output power from the oscillator. The patch impedance is matched resistively at the second harmonic frequency. The patch antenna is fabricated using Diclad 522 microstrip substrates (relative permitivity ï¥r = 2.5) with a dielectric thickness of 1.57 mm. A GaAs FET AT-8250 transistor is used as an oscillator and a frequency multiplier and acts as the active component. Fundamental frequency is designed at 2,4 GHz band, so that the second harmonic frequency operates at 4,8 GHz band. The frequency is chosen to facilitate and to extend the needs of communications in rural areas using the unlicensed Industrial Scientific, and Medical (ISM) band. Operating the communication infrastructures intended for the use at 2.4 GHz band at its second harmonic frequency, is intended to alleviate interference levels at 2.4 GHz

IDENTIFIKASI TURUNNYA KERJA CRANE HYDRAULIC YANG MEMPENGARUHI PROSES BONGKAR MUAT PADA KM. GUNUNG DEMPO

Crane hydraulic merupakan pesawat bantu yang digunakan untuk proses bongkar muat di atas kapal yang harus mendapatkan perhatian dan perawatan secara intensif dan continue, agar crane hydraulic tersebut dapat beroperasi dengan lancar dan tahan dalam jangka waktu yang lama. Jika crane hydraulic mengalami penurunan kerja maka akan mengaikibatkan terlambatnya proses bongkar muat, hal ini sangat merugikan sekali pada perusahaan pelayaran pada umumnya. Adapun faktor yang menyebabkan turunnya kerja crane hydraulic diantaranya adalah ausnya roda gigi pada pompa hidrolik, viskositas oli hidrolik yang sudah rendah, air cooler yang rusak, dan kurangnya perawatan. Sebagaimana fungsi dari ausnya roda gigi pada pompa hidrolik, oli hidrolik, dan air cooler adalah untuk menjaga agar kerja dari crane hydraulic tetap optimal. Untuk itu crane hydraulic yang digunakan haruslah mempunyai kriteria yang baik dan mutu yang sesuai dengan spesifikasinya. Dapat dilihat dari kerja crane hydraulic saat beroperasi apakah apakah bekerja secara optimal. Selain itu roda gigi pada pompa hidrolik, oli hidrolik, dan air cooler yang digunakan harus dijaga kualitasnya agar tidak cepat rusak, karena jika salah satu bagian dari crane hydraulic rusak tentu saja akan menimbulkan pengaruh negatif dan juga akan mengakibatkan lebih lama proses bongkar muat di atas kapal. Oleh karena itu perawatan pada roda gigi pada pompa hidrolik, oli hidrolik, dan air cooler yang teratur dan sistematis adalah sangat mutlak diperlukan pada crane hydraulic, dan untuk menjaga kerja crane hydraulic maka perlu dilakukan perawatan atau pemeliharaan terhadap komponen-komponen yang semua itu akan penulis bahas pada skripsi ini. Kata Kunci: Viskositas, perawatan kerja crane hydrauli

Femtocell Performance Over Non-SLA xDSL Access Network

Environmental medicin

Variable step closed-loop power control with space diversity for low elevation angle High Altitude Platforms communication channel [Langkah variabel kontrol daya tertutup dengan keragaman ruang untuk sudut elevasi rendah pada kanal komunikasi HAPs]

This paper proposes variable step closed loop power control algorithm combined with space diversity to improve the performance of High Altitude Platforms (HAPs) communication at low elevation angle using Code Division Multiple Access (CDMA). In this contribution, we first develop HAPs channel model which is derived from experimental measurement. From our experiment, we found HAPs channel characteristic can be modeled as a Ricean distribution because the presence of line of sight path. Different elevation angle resulting different K factor value.  This value is then used in Signal to Interference Ratio (SIR) based closed loop power control evaluation. The variable step algorithm is simulated under various elevation angles with different speed of mobile user. The performance is presented in terms of user elevation angle, user speed, step size and space diversity order. We found that the performance of variable step closed-loop power control less effective at low elevation angle. However our simulation shows that space diversity is able to improve the performance of closed loop power control for HAPs channel at low elevation angle.*****Kajian ini mengusulkan suatu algoritma kontrol daya langkah variabel loop tertutup dikombinasikan dengan keragaman ruang untuk meningkatkan kinerja komunikasi High Altitude Platforms(HAPs) pada sudut elevasi rendah menggunakan Code Division Multiple Access (CDMA). Kami berkontribusi untuk mengembangkan model kanal HAPs yang berasal dari pengukuran eksperimental sebelumnya. Dari percobaan tersebut, kami menemukan karakteristik kanal HAPs yang dapat dimodelkan sebagai distribusi Ricean karena kehadiran jalur tanpa penghalang. Eksperimen menunjukkan bahwa perbedaan sudut elevasi menghasilkan perbedaan nilai factor K. Nilai ini kemudian digunakan dalam Signal to Interference Ratio (SIR) berbasiskan evaluasi kontrol daya loop tertutup. Algoritma langkah variabel disimulasikan dibawah sudut elevasi yang berbeda dengan kecepatan yang berbeda dari pengguna vobile. Kinerja tersebut disajikan dalam hal sudut elevasi pengguna, kecepatan pengguna, ukuran langkah dan ketertiban ruang keanekaragaman. Kami menemukan bahwa kinerja langkah variabel kontrol daya loop tertutup kurang efektif pada sudut elevasi rendah. Namun simulasi kami menunjukkan bahwa ruang keragaman mampu meningkatkan kinerja kontrol daya loop tertutup untuk kanal HAPs di sudut elevasi rendah.