System for remote access to computer network

A system for remotely accessing computer networks is provided in which a central hub is connected to a computer network. The central hub may then be connected to a plurality of remote sites through an earth-orbiting satellite. Users at multiple remote sites may be connected to the central hub simultaneously through frequency management techniques.

FIELD OF THE INVENTION 
The invention relates generally to a system for interconnecting computer 
systems. More specifically, the invention relates to a system for 
providing computer network access to remote computer workstations. 
BACKGROUND OF THE INVENTION 
Computer networking is rapidly becoming a standard way of life. Computer 
networks have grown from isolated connections among research scientists, 
to the "Information Superhighway" of today. Every day, millions of 
consumers, businesses and other organizations have access to a 
rapidly-increasing resource of materials over the Internet. Some examples 
of these resources are on-line universities, museums, libraries, and 
"Newsgroups," which provide forums for discussion on a huge variety of 
subjects. 
Perhaps the fastest-growing segment of the Internet is known as the World 
Wide Web. Through the use of standardized text and graphic formats, 
computer users can easily access and navigate through the wealth of 
available information. Due to its highly graphical format, businesses have 
also begun advertising through the Web, by allowing users to download 
images, video or sound clips, and/or text documents relating to their 
products. Some businesses have already begun to accept orders directly 
over the Internet, using credit card information, or an experimental new 
type of debit account known as "e-cash" or electronic cash. 
In the developed countries, gaining access to the Internet is a simple 
matter of desire. With proper computer equipment, users can easily 
contract, for a nominal fee, with any of a growing number of "providers" 
that allow access to the Internet, usually over the phone system. Some 
providers offer a simple direct link, while others, such as COMPUSERVE and 
AMERICA ONLINE offer their own services and resources in addition to 
access to the Web. Universities and other organizations are often directly 
connected to the Internet and automatically provide access to any of their 
students, professors, members, etc. As a result, information is becoming 
more and more readily available. Currently, AMERICA ONLINE alone estimates 
that it handles hundreds of thousands pieces of e-mail every day. 
As mentioned, access to the Internet is largely through phone lines or 
dedicated communications lines--in other words, a sophisticated 
telecommunications infrastructure. Such infrastructure only exists today 
in developed countries. In undeveloped countries, villages and communities 
separated by vast distances are fortunate if they have limited telephone 
service, if any. Even when there is phone service, the quality of the 
telephone connection is often poorly suited to sustain the bandwidth 
necessary to support digital data transfer at a usable rate. 
The lack of access to the Web and Internet has not been perceived as a 
problem in the past. Users were mostly academics, researchers, or computer 
enthusiasts and the information available was often of a highly 
specialized nature. Now, however, with more users coming from the general 
population, and with the information being more broad-based, it is 
believed that access to the Internet will be mandatory for a country or 
society to participate in the global community of the very near future. 
For example, physicians in developed countries can now confer 
electronically about cases, search massive medical databases and browse 
the latest medical journals, all from their personal workstation. 
Schoolchildren can search encyclopedias, visit faraway places on their 
screens, or even "chat" with other children around the country and the 
globe to discuss their homework. 
Similarly, as corporations and other organizations extend their reach 
globally, the need for computer access in remote locations has also 
increased. This need applies to internal networks, intranets or any other 
organizational network. 
Unfortunately, the obvious solution to the problem is not a currently 
economically viable one. If a proper infrastructure were installed 
connecting these remote communities, access would no longer be a problem. 
However, the astronomical cost of this installation, in the face of 
pressing healthcare, hunger and other priorities, simply cannot be 
justified today. Since the remote users will have potentially limited 
funds to expend on network access compared to their developed-world 
counterparts, it would be difficult, if not impossible, to recoup any 
investment spent on the infrastructure, notwithstanding the unquantifiable 
benefits to the users themselves. 
SUMMARY OF THE INVENTION 
In view of the foregoing deficiencies or lack of viable existing systems, 
it is an object of the invention to provide a system for remotely 
accessing computer networks. 
It is another object of the invention to provide a system for remotely 
accessing computer networks that does not rely on an existing, 
telecommunications infrastructure. 
It is a further object of the invention to provide a system for remotely 
accessing computer networks that is capable of interconnecting 
workstations over relatively long distances. 
It is yet another object of the invention to provide a system for remotely 
accessing computer networks that allows access by multiple users 
simultaneously. 
It is a still further object of the invention to provide a system for 
remotely accessing computer networks that is simple and economical to 
implement and maintain. 
According to the objects of the invention, a system for remotely accessing 
computer networks is provided in which a central hub is connected to a 
computer network. The central hub may then be connected to a plurality of 
remote sites through an earth-orbiting satellite. Users at multiple remote 
sites may be connected to the central hub simultaneously through frequency 
management techniques.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, a schematic chart of an overall system according 
to a preferred embodiment of the present invention is shown. The system 
provides a digital data connection between various remote users 10 and a 
computer network (represented at 20). In the preferred embodiment, the 
computer network is preferably the Internet, including any protocols and 
standards such as the World Wide Web. It is to be understood that the 
computer network can be any network or computer gateway that provides 
access to other computers at other remote locations. 
Preferably, the computer network is directly connected to a hub gateway 
station 30, which is part of the system of the present invention. By 
"directly connected," it is to be understood that the station 30 is 
connected to the computer network through any of various known means, such 
as a telephone, microwave or permanent hardwired connection. The hub 
gateway station provides hardware and software for processing multiple 
remote user connections simultaneously, as will be described more fully 
below. 
Connected to the hub gateway station 30 is a satellite dish 40 capable of 
transmitting and receiving multi-frequency signals, as described more 
fully below. Preferably, the satellite dish is aimed at and in 
communication with a communications satellite 50 in earth orbit. 
Preferably, the satellite is stationed in a geosynchronous orbit providing 
direct line-of-sight communications with all of the intended remote users. 
It is contemplated that more than one satellite may be employed in the 
system of the present invention if some remote users are too remote to be 
contacted by a single satellite. In such case, either additional hub 
gateway stations could be set up for each additional satellite, which 
would in essence create an entirely separate system, or more than one 
satellite dish may be used with a single hub gateway station. It is also 
contemplated that less-expensive lower earth orbit satellites may be used 
with the present invention. These satellites are not geosynchronous and 
thus continually pass in and out of the range of the hub station and 
remote stations. In such a case, proper tracking software would be needed, 
including system components such as the automatic frequency control 
system, disclosed in co-pending U.S. patent application Ser. No. 
08/650,616 to the present assignee. Any satellite communication frequency 
bands are contemplated, including, but not limited to, C-band, Ku-band, 
L-band, X-band, and Ka-band. 
The remote users each have smaller satellite dishes 60, such as a 0.3-meter 
to 2.4 meter dish. The remote users 10 may preferably be any persons or 
organizations desiring to access the computer network 20. Due to the low 
level of capital available in many remote communities, it is likely that a 
central location or organization, such as a school, hospital or town 
meeting place would have the required remote user equipment of the present 
invention. The term "remote user" is intended to refer both to individuals 
who may be transferring information from/to the computer network, and 
organizations that might collectively own one set of the required hardware 
for the system. 
Each remote user 10 will have a satellite dish 60 capable of 
transmitting/receiving data from the satellite 50. Each users' satellite 
dish 60 is connected to a workstation (see, e.g., 70). The exact 
configuration of each workstation 70 is unimportant, as long as the 
workstation is capable of communicating with the satellite 50 as discussed 
below. It is also preferred that the workstations, such as a personal 
computer, will contain the software necessary to interface ultimately with 
the computer network. For example, for accessing the World Wide Web, it is 
preferred that the workstation 70 would include a web "browser," which 
interprets data written in Hypertext Markup Language ("HTML"), Java, or 
other language used for documents on the Web. Alternatively, each 
workstation 70 might include a standard communications software package 
for connecting with the hub gateway, while the hub gateway server would 
include any interface software, such as a web browser, for interpreting 
any documents retrieved from the Internet. Each workstation preferably 
includes a keyboard and a monitor for input/output to the remote user. The 
remote workstation 70 can also act as a server for a local area network 
(LAN) so that multiple users can take advantage of the satellite 
connectivity of the system. 
As can be seen in FIG. 1, remote users 10 are connected to the computer 
network 20 by communicating with the satellite 50, which in turn 
communicates with the hub gateway station 30, which is in turn connected 
to the computer network 20. The details of how these communications are 
accomplished is described more fully below. 
Frequency Selection and Allocation 
Whenever a user at a remote system 10 desires to connect to the network 20, 
assuming now that the remote workstation 70 is properly loaded with the 
necessary software, the remote workstation will broadcast a request using 
its satellite antenna over a common signaling channel. After transmission 
through the satellite uplink, software within the hub station 30 will 
assign an available data channel and an available modem connected to the 
hub for the link to that particular remote workstation. The hub system 
will then broadcast the assigned channel code through the satellite to the 
remote workstation 70, causing the workstation to switch its transceiver 
to the appropriate channel. 
In the preferred embodiment, a single transponder on the satellite would 
provide enough data capacity to accommodate 11,550 customers, as follows: 
Each transponder of the satellite has a total of 36 MHz of bandwidth. 
Leaving certain control signals aside (discussed below), approximately 33 
MHz of usable bandwidth for data is available. Each user channel would be 
allocated 9.6 kbit duplex bandwidth, or 20,000 Hz, resulting in 
approximately 1650 simultaneous user channels. Of course, all customers 
will not be connected to the system all the time, so more than 1650 
customers can be accommodated for use with a single satellite. Experience 
in customer usage rates has shown that approximately seven (7) customers 
can be adequately accommodated for each available data channel. Thus, 
multiplying the 1650 available data channels by seven customers for each 
channel equals the 11,550 customers per transponder. Of course multiple 
variations in the above calculations, such as the number of transponders, 
or the total bandwidth for each transponder or individual channel, may be 
made, ultimately affecting the number of customers that may be 
accommodated for a single transponder. More than one transponder may also 
be used to allow for more customers. 
To allow for the possibility of more than one remote workstation requesting 
an available channel at a time, more than one signaling channel, 
preferably five, are reserved for communications from the remote 
workstation. Once requests are sent, however, the remote workstations will 
remain in a wait state for a response from the hub station, so only one 
channel is reserved for the responses, which are sent in sequence by the 
hub station. 
The preferred frequency/channel allocation scheme is diagramed in FIG. 2, 
in which the frequency spectrum for a single transponder operating in the 
frequency range of 5925 MHz to 5965 MHz is shown. At the lowest frequency 
of this range, 2 MHZ (indicated at 210) is reserved as a guard band and is 
not used by the system. This guard band helps ensure that transmissions in 
the usable frequency will not interfere with or be interfered by other 
transponders in the adjacent frequency ranges. A similar guard band (at 
220) is found at the highest frequency of the example range, between 5963 
and 5965 MHz. 
Signaling channels (at 230) are above the lower guard band. These are used 
by the remote systems for requesting data channels. Five duplex channels 
operating at 9.6 kilobits encompasses 100 KHz of the spectrum. Below the 
upper guard band is the single duplex channel (at 240) used by the hub 
system to transmit information to the remote sites with data channel 
assignments. This single duplex channel at 9.6 kilobits takes up 20 khz of 
the spectrum. In the majority middle section of the spectrum (at 250) are 
the 1650 duplex data channels, beginning at 5927.1 MHz and running up to 
5960.1 MHz. Each duplex channel, at 9.6 kilobits, uses 20 KHz of the 
spectrum. Above that, the upper guard band is found. Other data transfer 
rates besides 9600 kilobits-per-second may be used as well with higher 
rates, more bandwidth is needed per channel. Thus, to maintain the number 
of user channels, the overall available transponder bandwidth would have 
to be increased. Alternatively, data compression or modulation may be used 
to achieve the same number of channels with the same transponder 
bandwidth. 
By having a minimum of signaling channels from the remote workstation to 
the hub station, and only a single return channel from the hub station for 
data channel assignments, the maximum amount of bandwidth for a given 
transponder is left for data channels. Of course, the more data channels 
available for a given transponder, the greater is the number of 
subscribers that the system can effectively handle and the greater the 
revenues per transponder. 
Referring now to FIG. 3, a functional block diagram of the system is shown. 
The hub station primarily consists of a server 300, which would be 
connected to the computer network through a more conventional connection 
305, such as, but not limited to, ISDN lines, T1 lines or other telephone 
network connections. If necessary, multiple servers 300 and computer 
network connections 305 might be utilized. The specific hardware of the 
server is not critical. 
A plurality N of modems 310 are connected to the server 300, each having a 
high enough throughput rate to sustain a data connection with one remote 
workstation. The modems 310 are preferably connected to the server through 
a multiplexer 315, capable of handling data to/from the full complement of 
modems simultaneously. The multiplexer 315 and the modems 310 are 
controlled by a network controller 320, which independently assigns a 
specific modem 310 to communicate with a specific remote workstation on 
request. Preferably, there is one single channel per carrier (SCPC) modem 
for each of the possible data channels, i.e., 1650 in the preferred 
embodiment, plus six for the control channels for a total of 1656. Each 
SCPC modem is set to a particular data channel. When needed, the network 
controller selects an open modem 310 and corresponding channel (see 250, 
FIG. 2) and assigns it to the remote terminal. Another modem configuration 
contemplated is multiple SCPC modems (one for each in-bound channel) and a 
smaller number of broad-band time division multiplex (TDM) modems for 
out-bound channels. Each TDM modem would then communicate with multiple 
remote workstations using packets addressed to each of the remote 
stations. TDM modems may also be used for in-bound channels. 
The modems 310 are then connected into an RF terminal 330 which handles 
communications through the satellite dish to the orbiting satellite 50. 
Included in the RF terminal 330 is a mixer that receives data signals from 
the modems 310 and modulates the specific data channel selected for the 
modem 310 with those data signals. The data signals from all of the modems 
310 are modulated, combined and transmitted to the satellite by a 
satellite dish antenna 340. Since the remote workstation has already 
received its data channel assignment, it will only be tuned to its data 
channel and will receive the data signals from its assigned modem 310. 
In the other direction, data signals that are transmitted by the remote 
workstation 360 on its assigned data channel are received by the hub 
satellite dish 340 and RF terminal 330, which includes a frequency 
splitter and frequency converter so that only the data signals on the data 
channels will be passed through to the assigned modem 310. The data 
signals are then demodulated and sent through the multiplexer 315 to the 
server 300, which in turn passes the signals to the computer network. 
At the remote station, the workstation 360 hardware is not critical, 
although it is preferred that it include at least a 486-type 
microprocessor. Besides any communications software, or network 
browser-type software, the workstation would only need to be loaded with 
the control software for its own modem and frequency converter. In the 
up-transmission portion of the communications hardware, the workstation is 
connected to a modulator/coder 370 that modulates the digital data signals 
from the workstation into RF signals. The RF signals are then converted 
preferably into the I-band by a converter 380. Use of the I-band is not 
critical and may be any frequency band used by the satellite. The I-band 
signals are then passed through an amplifier 390 and sent to the remote 
satellite dish 400 for transmission to the orbiting satellite 50. 
In the down-transmission portion, the components are reversed. Data signals 
incoming on a satellite data channel are received by the antenna 400 and 
passed into an amplifier 410 and then into an I-band to RF converter 420. 
The resulting RF signals are then passed to the demodulator/decoder 430, 
which transmits the digital data signals to the workstation 360, 
completing the transmission. 
Referring now to FIG. 4, a logic flowchart shows the functioning of the 
system. Initially, the workstation 360, based on a user's command, 
initiates a request for connection by transmitting a request signal over 
one of the five control channels discussed above (FIG. 4, at block 450). 
The workstation 360 selects one of the five control channels by monitoring 
the channels and choosing one that is not in use at that time. The request 
signal would also include identifying information about the remote 
workstation, for use by the hub server in verifying the subscriber status 
of the remote user, or for billing purposes, if necessary. The hub server 
300 receives the request signal, and selects one of the free data 
channels. The server then causes the network controller 320 to assign one 
of the modems 310 to that data channel and transmits an identifier for 
that data channel back to the remote workstation (at block 460) on the 
single return control channel (240, FIG. 2). The workstation 360 then 
causes its modulator/demodulator/converter hardware to be set to the 
selected data channel as well (at block 470). With the modem at the hub 
site and the remote communications hardware both tuned to the same data 
channel, bi-directional data transfer may commence, making a transparent 
connection between the user and the computer network (at block 480). Upon 
terminating the session, the remote workstation 360 transmits a 
termination signal (at block 490), which is received by the server 300, 
which causes the network controller 320 to unassign the particular modem 
on that data channel, ultimately ending communication through the 
satellite link (at block 500). 
Of course, it is to be understood that the particular frequency bands, data 
rates, and channel characteristics disclosed are preferred, but not the 
only operative embodiments. Other selections may be made and would be 
similarly operative in the present invention. 
While the embodiments shown and described are fully capable of achieving 
the objects and advantages of the present invention, it is to be 
understood that the embodiments are shown and described for the purpose of 
illustration only and not for the purpose of limitation, the invention 
being limited only by the claims, which follow.