Shareware Grab Bag/Shareware Grab Bag.iso/090/gwsp88.arc/GW.304

Text File | 1988-04-11 | 18KB | 398 lines

This report is brought to you courtesy of Scott, W3VS, Roy, AA4RE,
HAMNET (a feature of COMPUSERV) and the Garlic Valley Packet Society,
Gilroy, California.
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Gateway: The ARRL Packet Radio Newsletter is published by the

American Radio Relay League          Stan Horzepa, WA1LOU
      225 Main Street                       Editor
    Newington, CT 06111

Larry E. Price, W4RA                    David Sumner, K1ZZ
     President                       Executive Vice President

Vol. 4, No. 12
March 4, 1988

NEW VERSION OF W0RLI PBBS NOW AVAILABLE

Version 4.5 of the W0RLI/VE3GYQ Packet Radio Bulletin Board
System software has been released.  It is available from the
usual sources or may be downloaded from the HamNet DL9 Data
Library of CompuServe.  If you have Version 4.4, you need only
download the special file MBEXE.ARC to get the changes.  Others
should download RUN45.ARC (the executable code) and SRC45.ARC
(the sources).

from CompuServe's HamNet


AMSAT-TAPR DIGITAL
SIGNAL PROCESSING PROJECT UPDATE

Steve Sagerian, KA0YRE, of Motorola has really come through for
the digital signal processing (DSP) project.  He arranged for the
DSP operations branch of Motorola to come up with two 56001 EXP
kits.  This kit comes with bare boards, boot ROMS (a debugger,
monitor), PALs and several manuals.  Just to get things rolling
in a hurry, they decided to be very generous and throw in two
DSP56001 chips.  This board has a 20.48-MHz clock and processes
10.25-million instructions per second.  Using the architecture to
its fullest, one could do a 1024-point Fourier transform in 3.48
ms.  Steve and Bob McGwier, N4HY, will be building up these two
units.  We may expect further support from Motorola as they get
applications back from us.  We wish to thank Motorola, Inc for
their generous support.

from Bob McGwier, N4HY, via CompuServe's HamNet


NEW TAPR OFFICERS ELECTED

At the February 21 annual meeting of Tucson Amateur Packet Radio
Corp (TAPR),  the following officers were announced as elected by
the Board of Directors: President Andy Freeborn, N0CCZ; Vice
President Tom Clark, W3IWI; and Secretary-Treasurer Scott
Loftesness, W3VS.  In addition, an Executive Committee was
appointed by the board to run the day-to-day affairs of the
organization.  The Executive Committee consists of the above
three officers plus Directors Lyle Johnson, WA7GXD, David Toth,
VE3GYQ, and Harold Price, NK6K.

from Scott Loftesness, W3VS
  via CompuServe's HamNet


UoSAT-C SPACECRAFT
TO BE BUILT AT UNIVERSITY OF SURREY

The UoSAT Spacecraft Engineering Research Unit at the University
of Surrey in the United Kingdom is now building a third UoSAT-
OSCAR spacecraft - UoSAT-C. NASA has agreed to provide a launch
for UoSAT-C on a DELTA launch vehicle currently scheduled for
late 1988. The DELTA should place UoSAT-C into a 43-degree-
inclination, 500-km circular orbit.

UoSAT-C will carry experimental engineering, science and
communications payloads developed in close collaboration between
international professional engineering and Amateur Radio
communities. These payload experiments develop further the
mission objectives supported by the highly successful UoSAT-1 and
2 (UoSAT-OSCAR-9 and UoSAT-OSCAR-11) satellites which are still
operational after six and four years in orbit, respectively. The
UoSAT program and series of satellites are intended to complement
the AMSAT-OSCAR, RS and FUJI-OSCAR Amateur Radio communications
satellites by providing a space science and engineering facility
readily available to both amateur and professional experimenters
alike, thus, generating a greater mutual awareness and
collaboration.

UoSAT-C, like the previous UoSAT missions, will have a strong
element of international collaboration - specifically with
members of AMSAT-UK, AMSAT-NA in the United States and Canada,
VITA, Quadron, NASA, the British National Space Centre and the
European Space Agency.

UoSAT-C Payloads

o  Store-And-Forward Communications

Since 1983, UoSAT has played a major role in an international
collaborative project developing cost-effective digital store-
and-forward satellite communications techniques. The UoSAT-OSCAR-
11 Digital Communications Experiment (DCE), funded by the
Volunteers In Technical Assistance (VITA) and built by VITA/AMSAT
volunteers in the US, UK and Canada, provided the first
operational tests of store-and-forward PACSAT communications
within the amateur satellite service. Drawing on the operational
and engineering data gained from the DCE, UoSAT and VITA are
developing a high performance digital store-and-forward
communications payload specially tailored for use by inexpensive
ground stations. To test this payload, UoSAT-C will carry the
PACSAT Communications Experiment (PCE). The PCE will be openly
accessible to radio amateurs operating in the 2-meter and 70-cm
bands (Mode-J). VITA is seeking additional frequency allocations
outside the amateur bands to allow limited use of the UoSAT-C PCE
by VITA ground stations in remote areas to provide technical
assistance and disaster relief.

o  Radiation Studies Experiments

Microprocessor-controlled payloads such as the PCE cannot be
built without VLSI semiconductors and most recent and affordable
VLSI devices have not yet been tested for space use. UoSAT-C will
host several experimental payloads studying the effects of the
space radiation environment on VLSI devices:

Cosmic Particle Experiment (CPE), comprising an array of large-
area PIN diodes, will detect energetic particles which cause
single event upsets (SEUs) in VLSI circuits (such as high-density
RAMs).

CCD Single Event Upset Experiment (CCD-SEU), comprising an
enclosed charge-coupled device (CCD) array, will detect energetic
cosmic particles and evaluate the effect of SEUs on CCD imagers.
This data is of particular importance for scientists using
sensitive CCDs as star sensors.

Total Dose Experiment (TDE), using special FETs located around
the spacecraft, will measure the total radiation dose accumulated
by the on-board subsystems and payloads. These dose measurements
will allow engineers to assess the shielding properties of the
spacecraft structure and to correlate changes in LSI-device power
consumption and performance with total radiation dose.

o  Satellite Technology Experiments

UoSAT-C will carry a range of satellite technology experiments
associated with power systems, on-board data handling (OBDH),
attitude determination, control and stabilization (ADCS) and RF
modulation.

o  Power

The spacecraft will be powered from GaAs solar cells and will
include experimental patches of novel GaAs, InPe and Si solar
cells with a variety of newly-developed cover-slides. The
performance of these cells will be monitored throughout the
mission as a function of radiation dose. The spacecraft on-board
computers will constantly monitor and adjust the Battery Charge
Regulator and Power Conditioning Module to optimize power
conversion and storage efficiency.

o  On-Board Computers

UoSAT-C will include several computers. In addition to the
primary RCA1802 on-board computer (OBC-1) running DIARY-type
software, there will be a more powerful 80C86-based, OBC-2
supporting complex attitude control algorithms and spacecraft
data networks. Four transputers in a parallel-processing array
will be available for highly sophisticated on-board image and
data processing and the PCE will employ an 80C186-family computer
to manage high-speed communications links and several megabytes
of RAM.

A wide range of memory devices using different technologies and
architectures will make up a total on-board capacity of around 5
megabytes of RAM. The radiation-induced effects on the processors
and associated memories will be monitored and evaluated
throughout the lifetime of the spacecraft.  The network of
computers on UoSAT-C will make this spacecraft the most
computationally powerful of its class and will support demanding
experiments in advanced spacecraft attitude determination and
control, data communications and image processing.

o  Attitude Determination and Control

The 43-degree-inclination, non-sun-synchronous nature of the UO-C
orbit will necessitate the use of new attitude determination and
control mechanisms to maintain accurate Earth pointing. In
addition to more-complex attitude control algorithms executed by
OBC-2, improved analog and digital sun sensors and Earth horizon
sensors are being developed at UoS for the mission.

o  Digital Signal Processing

If time and resources permit, a Digital Signal Processing
Experiment may be included on UO-C to evaluate
modulation/demodulation schemes.

o  Modular Construction

A new concept of highly modular construction has been developed
and is under test for UoSAT-C. This new, modular structure should
result in much improved utilization of the available spacecraft
envelope, greater ease of assembly and integration and allow a
more rapid response to future launch opportunities.

For The Users

Like UO-9 and UO-11, UoSAT-OSCAR-C will support a worldwide user
community of engineers, scientists, educators and communicators.
If all goes according to plan, UO-C will provide spacecraft
housekeeping telemetry, long-term telemetry surveys, results from
on-board experiments, news bulletins and communications
facilities on a single downlink through packet-radio techniques.
We will finalize and publish communications modem and protocol
details as soon as possible  to allow ground stations to equip
themselves.

While numerous international teams are already collaborating on
UO-C, UoSAT is interested in hearing from others interested in
possible collaboration, especially in the area of user ground
station support.

The UoSAT team are happy to be able to make a public announcement
of the UoSAT-C mission and we hope that it will contribute to the
long history of successful and technically important OSCAR and RS
missions and maintain the tradition of international
collaboration in the amateur satellite service.

from Dr. Martin Sweeting, G3YJO,
  Director of Satellite Engineering,
  University of Surrey


THE "STAGGERED BACKBONE" NETWORK CONCEPT

Florida's packet radio network has undergone many evolutionary
changes over the last several years.  First, there were many
individual packeteers connecting over long distances on quiet
channels.  Then, as more people joined in, dedicated digipeaters
were pressed into service.  Then came switches, the 220-MHz
backbone and, most recently, NET/ROM.  At a Southern Region Wide
Area Networking Symposium, I proposed what I believe will be the
next evolutionary step in the development of our network.  I call
it the "Staggered Backbone."

We knew a long time ago that as the number of users and PBBSs
grew, it would become impractical to move traffic between
portions of the network on the same 2-meter RF channels that were
shared by the users.  We also knew that packeteers in adjacent
towns would cause unnecessary interference to each other as they
all tried to access their local digipeater and hear each other.
We, therefore, moved towards an architecture in our network that
allowed users in a given area (called a Local Area Network, LAN)
to reside on a different 2-meter channel than their neighbors.
We tied all of the LANs together using the 220-MHz band.  This is
roughly where the network stands today.

There is still room for improvement.  We have discovered that the
same problems of "hidden transmitters" (where two stations cannot
hear each other and, therefore, transmit at the same time) and
"hold off" (where a station is prevented from transmitting for
long periods of time because of other traffic) exist on the
backbone and cause the same congestion there as on 145.010 MHz.
Because the number of stations which access the backbone directly
is deliberately kept small, the problem is minimized to a certain
extent, but not eliminated.

Another problem which confronts the current backbone structure is
the issue of how to increase its speed in the future.  With all
of the nodes on the backbone operating at 1200 bauds, speeding
things up might require that every node upgrade on the same day
(an impossible situation) or that some nodes move to a different
frequency, thus, breaking the backbone.

The staggered backbone solves many of these problems and has a
great potential for allowing a significant increase in the
overall network throughput.  The staggered backbone concept is
built upon the fact that NET/ROM software  allows a three-port or
four-port node to be assembled quite easily.  Three ports allow
the node to operate on three separate frequencies (or bands) at
the same time and to route packets between them.

In a network with a staggered backbone, most nodes would consist
of three TNCs and three transceivers operating on the 144, 220
and 440-MHz bands  (other bands may be used as appropriate). The
144-MHz port serves the local users on a preassigned LAN
frequency and connects to the other ports via a special serial
port cable and diode matrix.  The 220-MHz port handles the
transfer of information to neighbors in one direction; the 440-
MHz port handles information going in another direction.  The
reason for choosing three separate ham bands is to minimize
interference between the radios without the need for costly tuned
cavities and special filters.

The staggered backbone works best where the network topology is
basically linear.  Where Y-shaped splits in the network are
required, the options are to use still another band (eg, 900 MHz)
in place of 144 MHz (resulting in a dedicated three-port backbone
node with no LAN service), construct a four-port node (to serve
the node plus three backbone frequencies) or to stick with the
current scheme of having three different background nodes on a
common frequency (this last option should only be used if the
three nodes can all hear each other clearly).

A list of the benefits of using a staggered backbone follow.

1.  Since  there are  only two nodes  on any given backbone radio
link, "hidden transmitter" and "hold off" are completely
eliminated from these links.  In fact, the only place that
packets can collide (besides on the LAN) is in the cable that
mates the TNCs at the node.  And, since communication between
TNCs typically runs at 4800 or 9600 bauds and does not include
TXDELAYS and long DWAITS, the TNCs can recover from collisions on
the cable very quickly.  Also, all of the TNCs talking on the
cable can hear each other clearly, so there are no "hidden
transmitters" there.

2. The speed of  any  individual link can be increased at any
time without creating a logistics nightmare.  In fact, whenever
two adjacent nodes agree that they are prepared to go faster,
they can do it at their convenience.  The only thing that the
rest of the network will notice is improved performance and some
temporary down time while they switch over.

3. Backbone  nodes  can take advantage of directional antenna
systems to "squirt" all of their signals to a specific neighbor
instead of having to use omnidirectional antennas or directional
antennas with power splitters.  So, in addition to the
improvements gained by having a quieter channel, many nodes would
see an increased signal strength from their neighbors.

4.  Automatic routing table updates managed by the nodes can be
trusted again.  In many areas, nodes are operating with "permed"
tables because of NET/ROM's tendency to hear a distant broadcast
and add it to a routing table as a high quality path.  With less
traffic on the same frequency and directional antennas in use,
the chances of this happening are greatly reduced.

The transition from the current backbone to a staggered backbone
is very straight forward and, equipment costs aside, could be
accomplished in a short time.  Many of the nodes along the
Florida Gold Coast have made plans to proceed along this line;
the backbone link from Boca Raton to Hollywood will probably be
the first to move to 440 MHz on a permanent basis sometimes early
this year.  We hope that others will join us and continue to
strive for improvements in the network in all areas.

from Bill Piazza, KB4QVY @ W4NVC
  via FADCA>Beacon


GATEWAY CONTRIBUTIONS

Submissions for publication in Gateway are welcome.  You may
submit material via the US mail to:

   Gateway
   Stan Horzepa, WA1LOU
   75 Kreger Drive
   Wolcott, CT 06716-2702

or electronically, via CompuServe to user ID 70645,247.  Via
telephone, your editor can be reached at 203-879-1348 on evenings
and weekends, and he can switch a modem on line to receive text
at 300, 1200, or 2400 bauds.


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