Very Small Aperture Terminal Networks Research Articles

Implementasi Automatic Uplink Power Control (AUPC) Pada VSAT Single Channel Per Carrier (SCPC)

The cable network is not suitable for connecting geographically distant communication systems such as Indonesia due to the low efficiency of the installation process, which requires large capital. It needs alternative technology, such as Very Small Aperture Terminal (VSAT) but it is vulnerable to interference and equipment weaknesses that will reduce performance. W eather in Indonesia is erratic, sometimes suddenly raining makes VSAT communication network vulnerable to interference, because it adjusts transmit power manually. Especially for VSAT network of PT. Megah Surya Pertiwi, PIC in location does not understand VSAT. Based on results of analysis and testing, there was a decrease in ping quality, Eb/No, C/N when it rained. Need to adjust transmit power so that quality returns to normal with weather at location. Prior to implementation of Automatic Uplink Power Control, modem at Graha HUB independently defaulted power at 0dB and at Kawasi site at 2dB, when it rained and power was not increased link became unstable there was a Request time out and intermittent with occasional ping>1000ms, current C/N value weather is good at a value of 20.34dB while when it rains at 17.42dB and Eb / No value is unstable. After AUPC power transmits automatically adjusts. P ing value becomes more stable, ping on VSAT can be good if delay value is 500-800ms, with a maximum delay of 770ms to IP Modem monitoring site and 789ms to IP Lan PT. MSP. C/N value obtained is 21.09dB in accordance with ideal C/N range for VSAT networks. Eb/No value is stable according to target, namely 10 dB on the HUB modem and 9 db on monitoring site modem. When modem detects a decreasing or increasing Eb/No value, system automatically adjusts transmit power so that the Eb/No value match ing target .

Next-generation multiservice VSAT networks

Very-small-aperture terminal (VSAT) satellite networks have so far been successful in the provision of specific communication services to geographically dispersed users. However, user demands are becoming more complex and VSAT networks are expected to provide a much wider range of services (voice, data and multimedia). This paper investigates how this service integration could be achieved and shows that performance improvements are possible if efficient multi-access protocols and speech compression with voice-activity-detection techniques are used. It also discusses the future role that VSATs could play in the provision of access to the integrated broadband communication network to remote users. It is shown that it could be possible to use VSATs for ATM service provision, but there are limitations on the system's performance from the satellite delay and limited link capacity.

Response-time evaluation of transaction-oriented applications in VSAT networks

The authors present modeling of an integrated terrestrial-satellite network using very small aperture terminals (VSATs), for transaction-oriented computer applications. They address the analytical and simulation modeling techniques used to study the network performance. More specifically, these models are used to obtain network response times for an integrated terrestrial-VSAT network for inquiry-response applications under various load conditions at the cluster controller units. The major result obtained through this analytical and simulation modeling suggests that communications satellite channels can be used efficiently for the interactive inquiry-response traffic at an acceptable response time, provided that the system parameters including the link transmission rates are chosen appropriately. >

SS/FDMA router for flexible satellite communications networks

The subchannel switched frequency-division multiple-access (SS/FDMA) system improve the routing flexibility of transponder banks in channelized multibeam satellites. This system can efficiently be utilised to construct a VSAT (very small aperture terminal) network and/or a business satellite communications network using small aperture terminals. The authors address the application of the SS/FDMA system to such networks. A proof-of-concept (POC) model of SS/FDMA onboard equipment called the SS/FDMA router is described in terms of its configuration and measured electrical performance. Results of transmission experiments using the POC model as well as computer simulations are presented. In addition, a redundant SS/FDMA router configuration is proposed, and its reliability is calculated for a 15-year satellite mission time. Finally, estimated values of volume, mass, and DC power consumption of the redundant SS/FDMA router are presented. >

VSAT technology, trends, and applications

A survey of very small aperture terminal (VSAT) technology is provided, and systems and services using VSAT technology are described. Trends in VSAT technology and applications, the three general categories of VSAT networks (broadcast, point-to-point, and interactive), and system architecture and design are discussed. >

VSAT data networks

The use of satellite channels for very small-aperture terminal (VSAT) data networks such as spread spectrum and ALOHA is reviewed. Certain basic aspects of the architecture of VSAT data networks are discussed. Although spread spectrum and ALOHA have different origins and are sometimes represented as competing technologies, they can in fact be characterized as different ways of viewing the same low-dimensional signals in a high-dimensional signal space. After a brief introduction to the architecture of VSAT networks, it is shown how a simple linear transformation of conventional ALOHA packets called spread ALOHA leads to signals identical in all respects to the most common form of spread-spectrum signals. Two practical consequences of this theoretical result are discussed. First, for the case of small earth stations it is not possible to find an Access technique with a higher throughput than spread ALOHA. Second, the use of different spreading sequences for different users in a packet network using spread spectrum is not necessary for user separation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A performance analysis of DS-CDMA and SCPC VSAT networks

Spread-spectrum and single-channel-per-carrier (SCPC) transmission techniques work well in very small aperture terminal (VSAT) networks for multiple-access purposes while allowing the Earth station antennas to remain small. Direct-sequence code-division multiple-access (DS-CDMA) is the simplest spread-spectrum technique to use in a VSAT network since a frequency synthesizer is not required for each terminal. An examination is made of the DS-CDMA and SCPC Ku-band VSAT satellite systems for low-density (64-kb/s or less) communications. A method for improving the standard link analysis of DS-CDMA satellite-switched networks by including certain losses is developed. The performance of 50-channel full mesh and star network architectures is analyzed. The selection of operating conditions producing optimum performance is demonstrated. >

Compact private hubs for corporate VSAT networks

Satellite communications has played a significant role in making information networks a strategic corporate asset. Very small aperture terminal (VSAT) networks, in particular, have special appeal for the corporate network user community because of unique advantages in cost, operations, and user control. The recent rapid proliferation of these networks in a multitude of market segments, as diverse as retail and financial services, is evidence of their wide acceptance for business communications.

VSAT user network examples

A brief description of representative VSAT (very small aperture terminal) networks is presented. The samples were selected to provide a realistic picture about the VSATs current status. The discussion covers Telesat Canada's VSAT networks and services; NICNET, the Indian government's VSAT information network; VSAT network developments in Europel; AT&T's VSAT networks and services; and six private VSAT networks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

VSAT network economics: a comparative analysis

The economics of virtual circuit services offered through very small aperture terminal (VSAT) networks are examined and compared with terrestrial alternatives. It is shown that VSAT networks are cost-competitive with terrestrial networks at around $300 per month per VSAT. For HUB costs in the range of $100000 the VSAT network can be cost-competitive for networks as small as 100 VSATs. Networks smaller than 100 VSATs are not cost-competitive, because the space segment cost becomes a dominant cost contributor. >

Personal computer communications via VSAT networks

The very small aperture terminal (VSAT) satellite network, a transport medium that is becoming important for long-distance personal computer (PC) communications, is described and analyzed. The mature and readily available VSAT technology offers many benefits and advantages over conventional terrestrial networks, including lower operating costs, ease of installation and maintenance, support for multiservices, bringing locations where the cost of leased lines is exorbitant into the communications loop, and integrating a large number of VSATs into a single network to provide a cost-effective expansion from small to large systems. The following aspects of VSAT networks are discussed: network configurations, networking and multiaccess, error-control protocols, and end-to-end performance analysis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Advanced satellite concepts for future generation VSAT networks

Advanced communication networks that use very-small-aperture terminals (VSATs) are considered. The techniques and technologies suitable for powerful satellites and system architectures for future VSAT networks are discussed. These include high effective isotropic radiated power, multiple-beam satellite antennas, and various access techniques. Examples of systems planned by the government and private industry are described. >

Packet switch architectures and user protocol interfaces for VSAT networks

The architecture of VSAT (very-small-aperture terminal) satellite networks is discussed. The use of VSAT networks in existing applications is examined. Internal VSAT architectures, most of which are designed as packet-switching networks in a star configuration with a central packet switch performing routing and relay functions, are discussed. Three types of interface-synchronous-multipoint-protocol, asynchronous, and X.25-are then considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

VSAT networks: architectures, protocols, and management

VSAT (very-small-aperture terminal) satellite networks, are discussed, focusing on a particular network called STARCOM. The STARCOM system architecture is presented. A multiple-access protocol developed specifically for the STARCOM system is described and its performance is examined. The management capabilities of the STARCOM system are considered in detail. >

Application of renewal theory to unslotted ALOHA in VSAT networks

Renewal theory is used to develop the probability of successfully transmitting variable-length packets in a finite-user unslotted ALOHA channel operating in an satellite network of very small aperture terminals (VSAT). This result, which does not depend on the arrival distribution, is then used to determine the equilibrium or operating point from which the normalized throughput, traffic and delay are estimated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Channel access protocols for Ku-band VSAT networks: a comparative evaluation

The performance of candidate protocols for first-generation Ku-band very small aperture terminal (VSAT) satellite networks is compared. The goal is to assist the process of selecting a protocol. The performance comparison is carried out over a range of possible traffic, channel and satellite parameters, leading to an understanding of the appropriate regime for each of the protocols under consideration. The protocols considered are unslotted Aloha, slotted Aloha, selective-reject (SRE) Aloha, and demand-assigned time-division multiple-access (TDMA) or DAMA. >

Performance analysis of Ku-band VSAT networks

A critical parameter of a very small aperture terminal (VSAT) satellite network, namely the availability of its links, is defined as the percentage of time that information can be transmitted and received with acceptable quality. The information quality is quantified, and the factors that affect it are described. Link unavailability (outage) due to equipment problems and rainfall is discussed. The use of spread-spectrum techniques is considered. A performance analysis example is provided and some conclusions are drawn. >

Design and operational issues of VSAT application in ISDN-type networks

Advances in satellite technology in the area of very small aperture terminals (VSATs) offer economical data and voice services for corporate networks and rural applications. The authors describe VSAT application and technology with emphasis on analyzing the issues of quality after the sale. The quality and maintenance requirements of the VSAT networks in operation are defined. The reliability, maintainability, and availability calculations for VSAT networks with different topologies are evaluated. Results show that both star and point-to-point VSAT networks are capable of meeting higher availability standards.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation models for performance evaluation of satellite multiple access protocols

Simulation models are described for the performance evaluation of satellite multiple-access protocols used in VSAT (very small aperture terminal) data networks. Since the design of VSAT-based wide-area networks for interactive applications is critically dependent on the delay-throughput characteristics of the channel access protocol used, detailed simulation models have been developed to augment analytical performance-evaluation methods. Simulation models for several candidate VSAT access protocols, including random-access techniques such as Aloha, selective reject Aloha and slotted Aloha and demand-assignment multiple-access based techniques, are discussed in terms of traffic-source models, access algorithms, and performance-evaluation criteria. Numerical results for a realistic interactive data VSAT network environment are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

VSAT Networks—an overview

AbstractThis paper examines the technology and constraints of very small aperture terminals (VSAT) networks, a special type of wide‐area thin‐route satellite network that represents a recent innovation in the field of satellite communications. VSAT network architectures suitable for both data and voice communications are studied in this paper. Several issues concerning the frequency of operations, that is, C‐band versus Ku‐band are examined, and trade‐offs between non‐spread spectrum and spread spectrum techniques, as well as modulation and multiple access schemes, are considered in detail. Link design examples are given to illustrate the performance of various types of VSAT networks.