The satellitecommunication system proposed in this paper complies with the specifications of the DVB standards, , providing a standardised broadband interactivity connection. The forward link adopts the DVB-S2 protocol, and the return link adopts the DVB-RCS2 protocol to implement all-IP networking communication based on the satellite links. The system consists of one or more gateways and several terminals, forming a star-shaped topology network with a gateway as the core.
Some of the other issues with the geo-stationary systems are that they have a very low elevation angle (about 1-4 degrees) from Poles, which combined with high altitude of the satellites results in extremely large field equipment, e.g. antennas, that has to be properly pointed towards the satellite. The GOES and TDRS 1 installations at South Pole  use parabolic antennas of 10-meter radii built on large platforms. Though such installations provide high bandwidth, they cannot be used for numerous small field camps and science expeditions conducted each year at various locations in Arctic and Antarctic. NASA has demonstrated the use of lighter mobile PORTCOMM (Portable Communications) terminals with TDRS satellite system at North Pole in April-May 1999 . With an elevation angle of 0.8 degrees they were able to achieve data rate of 4.8 kilobits per second. Higher bandwidths up to 1 Mbps are possible with heavier TILT (TDRS Internet Link Terminal) systems that consume higher power.
systems while avoiding many of their drawbacks. Thus they provide alternative and complementary means of communications. In comparison to terrestrial wireless technologies, HAPs require considerably less communications infrastructure, they can serve potentially large coverage areas from a single site, little multipath fading and the cell planning is more straightforward since they are able to provide a line of sight and a free-space- like channel path. When compared to satellitecommunicationsystems, HAP communications system will provide a quasi-stationary coverage area, easy maintenance, short propagation delay, wide bandwidth, broadband capability using small size antennas and terrestrial terminal equipment, upgrading of the payload during the lifetime of the platform and the cost for fabrication and operation of airship is competitive compared with satellite system and it is a great advantage that airship can be recovered and repaired when system failure occurs.
multiband filters have been gaining wide attention in recent years. Dual-band filter is the most common multiband filter, which has been analyzed deeply in many articles with various configurations [1–6]. The dual-band filters were reported in [4–6] using SLR. Tri-band microstrip planar filters were also reported in [7–13]. However, RF filter is a basic and important component in the modern wireless communication system, and bandpass filter with the features of micro-package, good performance, low cost and ease of use has been the focus of device miniaturization. With the development of wireless communications, spectrum has become increasingly crowded, and the needs for multi-frequency filter applications are also gradually increasing. Special wireless transceiver is required to work in a number of respective bands, in order to allow users to adopt an individual terminal to achieve different services.
7. Ismail, A. F. and P. A. Watson, “Characteristics of fading and fade countermeasures on a satellite-earth link operating in an equatorial climate, with reference to broadcast applications,” IEE Proc. Microw. Antennas Propag., Vol. 147, No. 5, 369–373, 2000. 8. Matricciani, E., “Time diversity as a rain attenuation counter- measure in satellite links in the 10–100 GHz frequency bands,” European Conference on Antennas and Propagation (EuCAP06), 1–6, Nice, France, 2006.
A smarter solution to perform network security over links, including TCP PEP agents installed in intermediate nodes, is based on a IPsec extension called Multi-Layer IPsec (ML-IPsec) . The ML- IPsec principle is to divide IP datagram into different zones and apply different protection schemes at each zone. A protection scheme is then composed of: a set of security associations (SAs), a set of private keys and access control rules. Therefore, one or more authorized/trusted intermediate nodes can decrypt, modify and re-encrypt a certain part of the incoming segments according to what established in the security associations. An ML-IPsec security protection scheme well suited to satellite networks involving TCP PEP agents installed on both satelliteterminal and gateway to accelerate TCP over satellite channel can be structured as follows (Figure 4).
Abstract. In order to test the functions and performance of the satellite relay communicationterminal comprehensively before the satellite access network test and satellite relay communication test, a flexible automatic test system based on general hardware platform and special software was designed with electronic, communication, computer and network technologies. The testing system can provide equipment testing capability such as bit error rate, modulation signal quality and sensitivity analysis. The practical application results show that the flexible test system of relay communicationterminal has the characteristics of complete function, simple operation, accurate result, stable and reliable, which is suitable for application in practical engineering.
When the UE is able to support GPRS, external data tran- smission parameters can be characterized. These meas- urements just can take place when GPRS and WCDMA networks are considered . The configurations parame- ters are shown in Figure 7. We can appreciate in Figure 7, that GPRS system is configured; the power level of the base station (–40 dBm), the power of the mobile terminal (33 dBm), just like the power in the channels likewise establishes the power control.
5G technology is definitely the next most crucial mobile technology stage after 4G networks . It can be called as the real wireless world because it is a complete wireless communication with no boundaries.5G is expected to be an intelligent innovation technology which will interconnect the whole world with no limits. Now 5G is not a formally utilized term but new versions will give rise to system performance and in addition to this it will add latest features with new application domain. Figure 1 shows evolution of 1G to 5G. 5G is futuristic mobile technology which will be a successor of 4G network technology. 5G is a Fifth Generation wireless communication technology. 5G is an unused network system that has undoubted high data rate, trustworthy and low latency than the preceding generations. 5th generation technology framed on the footing created by 4G, the technologies to be used in 5G, are still being outlined. The 5th generation networks works on encoding type known as OFDM. The air interface outlined for considerable lower latency and better adaptability. 5G networks can work as low frequencies and high as “millimeter wave” and that frequency can communicate huge quantity of information/data, but few blocks at a moment of time. 5G networks are further probably to be networks of mini cells such as size of a house router than to be big tower; it is to extend network scope. The objective is to have great speed accessible and large scope at low latency than 4G. The latency rate of 4G is close to 50 milliseconds, but 5G cut down to almost one millisecond. This is specifically valuable for driverless vehicles and automated applications. The purpose of 5G is to achieve transmission speed to 20-30Gbps, which is 50 times speedy than 4G networks. And its speed has been being tested uninterrupted up to 1.5Gbps while traveling 100km/h and max up to 7.5 Gbps. 5th generation network is determine to provide up to a million of connections per square kilometer. It also implies the whole wireless world interconnection together with very high data rates.
2) a means of access to electronic information systems using various forms of data transmission, including, as a rule, via the Internet (for example, for communication in various chats, social networks, namely, Facebook, Twitter, Instagram, Telegram, Snapchat, etc.; or for use of e-mail, including using the so-called “cloud-based technologies” (“cloud computing”) for storing and processing information (for example, Google Drive or the like); or using so-called “messengers” such as Viber, WhatsApp, Skype, Facebook Messenger, Telegram, etc.). As the researchers point out, these telecommunication technologies represent network convergence supporting a wide range of access methods (traditional telephony, DSL, networks WLAN, RAN, etc.); at the level of service convergence during mobile communication sessions with the help of specialized software, mobile access to data, audio and video contraction, voice and instant messaging can be carried out. The widespread use of smartphones with installed programs that combine IP-telephony and instant messengers (Skype, Viber, etc.) or only instant messengers (ICQ, Telegram, WhatsApp, etc.) by mobile telecommunication subscribers form them as elements of distributed electronic information systems (hereinafter, DIS) . DIS components are distributed, therefore, on several computers. In turn, DIS is composed of file-server information systems and client-server information systems. In the latter, for example, a database and database management system are located on the server, and client-side software is located on the workstations. As specified in the literature, both local and distributed electronic information systems can be open for the public and closed, i.e. access to which is limited to their owner, proprietor or holder, to obtain more information on the features of individual electronic information systems and IREIS . At the same time one very significant feature should be mentioned. As a rule, information displayed on the device screen is not physically stored on it. It is stored in electronic information systems (information (automated) systems), on servers of the relevant companies  providing appropriate information and telecommunication services. In other words, in this case, a mobile device serves only as a means of access (a kind of “key”) to information that constitutes communication content. Otherwise, if specified information is stored in the memory of the device itself, the features of the use of the latter will be described below, in the third group. In addition, it should also be noted that some of the mentioned messengers or social networks also allow real-time communication (online). Therefore, in such cases, the smartphone should be assigned to the previous group according to its functional (functional, technical and communication) purpose;
TWTA transmitters are used extensively in radar, particularly in airborne fire-control radar systems, and in electronic warfare and self-protection systems. In these types of applications, a control grid is typically introduced between the TWT's electron gun and slow-wave structure to allow pulsed operation. The circuit that drives the control grid is usually referred to as a grid modulator.
found as components in broadcasting transmitters and in satellite transponders. Modulators are also used by CATV companies to place a baseband video television signal onto a desired VHF or UHF channel. Home video tape recorders also have built-in modulators which
The results revealed the dynamic characteristics of fading with respect to the local rainfall peculiarity in this particular region. The first order statistics are found to be good agree- ment with another measured statistics from a satellite beacon receiver located in Kuala Lumpur, Malaysia. On the other hand the fade duration distribution depicts the same behavior as ITU-R prediction model while the slope distributions were found to be substantially symmetrical around 0 dB/s and the conditional pdf of ITU-R which predicted fade slope follows closely the measurements. In addition, it is found that the highest rain-fade slope is likely to occur during evening hours (12 pm to 6 pm) due to the local convective events that frequently occur at this particular time. Such results provide critical information on the number and duration of outages as well as on system unavailability that together with the statistics of fade slope are useful for system designers to develop suitable PIMTs such as power control, adaptive modulation schemes, and diversity techniques to improve the link quality and availability especially during the heavy rain events in this particular region.
Satellitecommunication service industry has grown more rapidly than was forecasted in1992. This growth has been a global phenomenon as the economies of world have increased and improved communication services for both business and consumer market. Satellites orbit around the earth. These orbits can be circular or elliptical depending on its applications. Satellite is also known as space segment, and consists of three units, namely the fuel system, the satellite and the telemetry control, and the transponder. The transponder includes the receiving antenna to pick up signals from ground station, a broad band receiver, an input multiplexer, and a frequency converter which is use to reroute the received signals through a high powered amplifier for downlink. The primary role of satellite is to reflect electronic signals. In the case of satellites primary task is to receive signals from ground station and send them down to another ground station which may away over a distance from the first. This action can be two way, as in case of long distance phone calls. Another use of satellite is in the case of TV and radio broadcast, the ground station’s uplink is then downlinked over a wide region. Another use of satellites is observation, in which satellite equipped with cameras and various sensors.
Gateway: The point to which the satellite relays the call to the nearest ground receiver. The gateway do the work to patch the calls through. If a call to India originates in America, the gateway won’t be able to patch the call through the existing phone network. Than the gateway will transmit the call to the near most satellite, which will help to pass the call along till it reaches one that can help linking to the receiver. It depends on the location of the caller (transmitter) and receiver that how many times it may happen.