Temat: time division multiple access

Skocz do pozycji: 1.

Tytuł:: Underwater Acoustic Sensor Node Scheduling using an Evolutionary Memetic Algorithm
Autorzy:: Sivakumar, V.
Rekha, D.
Tematy:: broadcast UASN scheduling
memetic algorithm
time division multiple access
underwater acoustic sensor network; Pokaż więcej
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/307911.pdf Link otwiera się w nowym oknie
Opis:: Underwater Acoustic Sensor Networks (UWASNs) play an important role in monitoring the aqueous environment which has created a lot of interest for researchers and scientists. Utilization of underwater acoustic sensor node (UASN) scheduling for transmission remains, due to the limited acoustic bandwidth available, a challenge in such an environment. One of the methods to overcome this problem is to efficiently schedule UASN data using time division multiple access (TDMA) protocols the parallel transmissions, simultaneously avoiding interference. The paper shows how to optimize the utilization of acoustic sensor node bandwidth by maximizing the possible node transmissions in the TDMA frame and also by minimizing the node's turnaround wait time for its subsequent transmissions by using an evolutionary memetic algorithm (MA). The simulation of MA-TDMA proves that as the size of the network increases, every node in UWASN transmits with an average minimal turnaround transmission time. It also proves that as the TDMA cycle repeats, the overall network throughput gets maximized by increasing the possible node transmissions in the MA-TDMA frame.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Implementation of Multiple Access Techniques Applicable for Maritime Satellite Communications
Autorzy:: Ilcev, S. D.
Tematy:: Global Maritime Distress and Safety System (GMDSS)
Maritime Mobile Satellite Communications (MMSC)
Multiple Access (MA)
Multiple Access Techniques
Code Division Multiple Access (CDMA)
Time Division Multiple Access (TDMA)
Frequency Division Multiple Access (FDMA)
Random (Packet) Division Multiple Access (RDMA); Pokaż więcej
Wydawca:: Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Powiązania:: https://bibliotekanauki.pl/articles/116635.pdf Link otwiera się w nowym oknie
Opis:: In this paper are introduced fundamentals, characteristics, advantages and disadvantages of Multiple Access (MA) employed as transmission techniques in the Maritime Mobile Satellite Communications (MMSC) between ships and Coast Earth Station (CES) via Geostationary Earth Orbit (GEO) or Not-GEO satellite constellations. In fixed satellite communication, as a rule, especially in MMSC many users are active at the same time. The problem of simultaneous communications between many single or multipoint mobile satellite users can be solved by using MA technique, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Space Division Multiple Access (SDMA) and Random (Packet) Division Multiple Access (RDMA). Since the resources of the systems such as the transmitting power and the bandwidth are limited, it is advisable to use the channels with complete charge and to create a different MA to the channel. This generates a problem of summation and separation of signals in the transmission and reception parts, respectively. Deciding this problem consists in the development of orthogonal channels of transmission in order to divide signals from various users unambiguously on the reception part.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: AIS R-mode trilateration for GPS positioning and timing insurance
Autorzy:: Shyshkin, O. V.
Konovets, V. I.
Koshevyy, V. M.
Tematy:: Automatic Identification System
Global Navigation Satellite System
Global Positioning System
positioning
navigation and timing
time division multiple access
R-mode
time of arrival
time difference of arrival; Pokaż więcej
Wydawca:: Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Powiązania:: https://bibliotekanauki.pl/articles/59123272.pdf Link otwiera się w nowym oknie
Opis:: Satellite navigation is the backbone of maritime navigation today. However, the technical vulnerability of on-board Global Navigation Satellite System (GNSS) receivers the satellite system greatly destabilizes maritime security due to the loss of ship’s position and accurate time. This article devoted to study an alternative method for obtaining coordinates and accurate time based on the use of automatic identification system (AIS) radio channels, so-called range mode (R-Mode). We use other AIS ship stations with reliable position data as reference stations and determine time of arrival for received AIS transmissions. To improve the accuracy of measuring signal arrival instance in the time difference of arrival (TDOA), that we utilize for trilateration, it is proposed signal oversampling and applying the fast Fourier transform (FFT) to the product of quadrature components of the baseband Gaussian minimum shift keying (GMSK) signal in the window of AIS time slot. To take into account the movement of other ships, appropriate coordinate corrections are foreseen, which can be calculated by dead reckoning or by the inertial navigation system of our ship. The proposed method is fully compatible with the existing AIS signals and may be employed in critical situations of locally limited (jamming, spoofing) GNSS abilities. It can be implemented as a separate unit, working for receiving in parallel with the mandatory AIS transponder.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Reduction of BER using RSC code for Optical Code Division Multiple Access Networks
Autorzy:: Panda, Satyasen
Tematy:: Cross Correlation (CC)
Multiple Access Interface (MAI)
Optical Code Division Multiple Access (OCDMA)
Random Sparse Code (RSC)
Wavelength hopping time spreading (WHTS); Pokaż więcej
Wydawca:: Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:: https://bibliotekanauki.pl/articles/1178316.pdf Link otwiera się w nowym oknie
Opis:: In this study, a two dimensional (2-D) wavelength hopping and time spreading (WHTS) optical code division multiple access (OCDMA) code is designed using Sparse ruler technique. The proposed 64 bit 2-D code is constructed by an algorithm based on random spacing of sparse codes referred in this work as Random Sparse Code (RSC). The performance of the proposed 2-D RSC is evaluated in terms of bit error rate (BER), received signal power and time domain analysis of received signals. The system performance of the OCDMA system utilizing 2-D RSC code improved significantly due to less BER, low cross correlation property and simple encoder/decoder design. The output BER is much lower at a data rate of 1.25 gbps and 2.5 gbps for a distance of 100 km with ITU-T standard single mode fiber with attenuation level of 0.2dB/km.
Dostawca treści:: Biblioteka Nauki

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