Fig 4.1 Systems Schematics
The HSTN is intended for the use of individuals, small businesses, schools, a ca
tegory of customers that do not have and do not need a permanent bidirectional h
igh speed Internet connection. It is true that such a connection would be
preferable, but we need to capture also the cost aspect of the problem. How
many customers from those listed above would afford to pay the price of a
classical Ethernet equivalent speed.
The HSTN is intended to cover the entire Earth surface.
The only necessary equipment a virtual customer has to provide is a phone line
(POTS) and of course a PC. As opposed to the HFCN, in the case of HSTN, there
are no restrictions concerning the customer's geographical location.
The system's schematics is represented in the following figure.
The following components (subsystems) are identified at systems level:
Fig 4.2a. The Wireless Segment - GEO Option
Fig 4.2.b. The Wireless Segment - LEO Option
The WS is basically the Satellite Network. Figures 4.2.a,b represent the possible choices to choose between: the GEO satellites network or the LEO satellites network. The choice between these two alternatives is to be made according to a study on costs involved and performance achieved. The WS receives information flow from the Network Services Subsegment and retranmitts it to the End User Subsegment.
The Terrestrial Segment (TS):
The TS communicates with the WS and the EIS.
Its structure is depicted in the following figure:
Fig 4.3 The Terrestrial Segment
The TS is the component which is physically located on the Earth.
At its turn, it is composed by:
The NSS is the heart of the HSTN. All transactions flow through the NSS.
Intuitively, it is the interface between the EIS and the EUS. Both request for
information and the reply are vehiculated through the NSS. The thick line
segment in figure 4.3 represents the high speed bidirectional link.
The thin bidirectional line segment represents the path for other services
than the main flow. In this category of services we can include a back-up line
for centralized maintainance support. As we will develop in the following
sections, the fault management function will be included in the NSS but, some
grade of redundancy may prove to be useful .
The EUS is the set of all components the customer needs for connecting to
the HSTN. They are as follows:
The HSTN network is a highly complex system. Thus at this point we identify the main categories to which applicable standards belong. In the following sections , from these categories we filter out the actual standards for the given subsystem.
The International Organization for Standardization, (ISO), is one governing body recognized throughout the world as an organization which defines models for computer communication protocols. The OSI model provides a standard set of computer communication protocols as defined by the ISO. In the United States the national standards organization is the American National Standards Institute, (ANSI), and it participates in the creation of ISO protocols.
Internet Standards are developed by the Internet Engineering Task Force (IETF) and approved by Internet Engineering Steering Group (IESG). Internet Standards are separated into two groups:
The ISO Standards and the Internet Standards are both based on the concept of communication layers.
Introduction
To Contents
HSTN Components