Subject: [manet] Ad-Hoc compared to TETRA

From: "Berner Vegge" <[email-masked]>
Date: Wed, 19 Jun 2002 09:19:06 +0200

Hello!
I have read a little about Ad-Hoc and also a little about TETRA (Terrestrial Trunked Radio) which is defined by ETSI.

As I understand TETRA and AD-Hoc are very much adressing the same users, where the main users are police, ambulance, firemen, but also civil users and military users may be relevant.

The technology is very different for TETRA and Ad-Hoc. TETRA uses a

GSM alike principle with switches and base stations, while Ad-Hoc uses

nodes that are combined routers and terminals (no base stations).

But although the technique is different the features seem to be very much the same with security, priority, group calls etc.

From this I wonder if TETRA and Ad-Hoc are competing technologies in the same market or complementary in some ways. Is it e.g. relevant to use an Ad-Hoc network out in the field in a rescue operation and then use TETRA for communication towards hospitals etc?

I also wonder what the benefits of using Ad-Hoc compared to TETRA are.
Can anyone help me?

Thanks for your help!

Best Regards Berner

Get your FREE download of MSN Explorer at http://explorer.msn.com.

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---

From: "Vincenzo Cipolla" <[email-masked]>
Date: Wed, 19 Jun 2002 10:05:18 +0200

Berner,

My personal feeling is that the Tetra Technology could be one the most
suitable and real working technology to implement Ad-Hoc Networks,
specially if we look the promising ETSI TETRA Release 2, currently under
standardisation. If you want to explore the TETRA Technology I suggest to
compare the TETRA Release 1 Direct Mode(DMO) operation against of the
paradigms of the Ad-Hoc Network Technology. I'm sure that you will realise
that this part of the TETRA standard could be a way to implement Ad-Hoc
Networks.

BR,

Vincenzo Cipolla

**************************************************************
Vincenzo Cipolla

Marconi Mobile
Private Mobile Networks SBU
Software Development Director

Wireless Software Competence Centre
Galleria G.B. Gerace, 7
56124 Pisa  - Italy

Tel +39 (0) 50 3132421 (my office)
Tel.  +39 (0) 50 3132420(Secretary's Office)
Fax. +39 (0) 50 3132431 (my office)
Mobile Phone +39 (0) 335 7198283

http://www.marconi.com
**************************************************************

"Berner Vegge" <[email-masked]>@ietf.org on 19/06/2002 09.19.06

Sent by:  [email-masked]

To:   [email-masked]
cc:

Subject:  [manet] Ad-Hoc compared to TETRA

Hello!
I have read a little about Ad-Hoc and also a little about TETRA
(Terrestrial Trunked Radio) which is defined by ETSI.

As I understand TETRA and AD-Hoc are very much adressing the same users,
where the main users are police, ambulance, firemen, but also civil users
and military users may be relevant.
The technology is very different for TETRA and Ad-Hoc. TETRA uses a
GSM alike principle with switches and base stations, while Ad-Hoc uses
nodes that are combined routers and terminals (no base stations).
But although the technique is different the features seem to be very much
the same with security, priority, group calls etc.

   From this I wonder if TETRA and Ad-Hoc are competing technologies in the
   same market or complementary in some ways. Is it e.g. relevant to use an
   Ad-Hoc network out in the field in a rescue operation and then use TETRA
   for communication towards hospitals etc?
   I also wonder what the benefits of using Ad-Hoc compared to TETRA are.
   Can anyone help me?

Thanks for your help!
Best Regards Berner

---

From: "Vincenzo Cipolla" <[email-masked]>
Date: Wed, 19 Jun 2002 10:05:18 +0200

Berner,

BR,

Vincenzo Cipolla

Marconi Mobile

http://www.marconi.com

To:   [email-masked]
cc:

Hello!

Thanks for your help!
Best Regards Berner

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 07:13:55 -0600

Dear Berner,
 
I would add to Philippe that the term "MANET" describes a type of
communications situation in which all elements of the network are apt to be
in motion, rather than a particular standard or implementation.  TETRA, on
the other hand, is a specific solution to a problem, which as Philippe
points out, is somewhat different.  In any event, I don't think it is
possible to compare the two, since they are two different things.  One can
only say whether or not TETRA is a reasonable solution to the MANET problem.
 
Certainly, elements of TETRA may be helpful in dealing with the MANET
problem, but the very fact that TETRA relies on base stations would rule out
its entire adaptation as a general solution.  For example, if emergency
services are extended into an area that has suffered an earthquake or
hurricane, it is likely that any base stations, towers, etc. would be
unusable and the system would have to depend solely on what the service
agencies bring with them.  This would be a MANET problem.  
 
While, in my opinion, urban and suburban police and other emergency
communications would be more resilient if they had at least a capability to
function as a MANET, I recognize that in most situations, the added routing
efficiency due to base stations is beneficial.  In addition, there needs to
be a sufficient number of nodes in a area to support a MANET.  In extreme
rural areas, there would be too few mobile police and other emergency units,
so both base and relay stations would be necessary (unless one relies on
satellites or includes other, non-public service users in the MANET).
 
John Mullen  

-----Original Message-----
From: Philippe Jacquet [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re: [manet] Ad-Hoc compared to TETRA

Dear Berner,
 
TETRA is a mobile networks specificaly dedicated for police, fireman and
ambulance. It is based on a base station architecture like GSM and provides
similar low throughput. MANET is a mobile network based on multihop routing
but is not dedicated to specific applications. Since the hop distance can be
small, ad hoc architecture is suitable for high speed data transfer such as
in IEEE 802.11. 
 
In WTC attack 15 base stations were knocked out and the remaining base
stations isolated from network were unable to route data between them. This
is probably a situation where an ad hoc technology could help (see WERT
recommendation). I don't know whether TETRA can do that either. 
 
Philippe

----- Original Message ----- 
From: Berner Vegge <mailto:[email-masked]>  
To: [email-masked] <mailto:[email-masked]>  
Sent: Wednesday, June 19, 2002 9:19 AM
Subject: [manet] Ad-Hoc compared to TETRA

Hello! 
I have read a little about Ad-Hoc and also a little about TETRA (Terrestrial
Trunked Radio) which is defined by ETSI. 

*	From this I wonder if TETRA and Ad-Hoc are competing technologies in
the same market or complementary in some ways. Is it e.g. relevant to use an
Ad-Hoc network out in the field in a rescue operation and then use TETRA for
communication towards hospitals etc? 

*	I also wonder what the benefits of using Ad-Hoc compared to TETRA
are. 
Can anyone help me? 

Thanks for your help! 

Best Regards Berner 

  _____  

Get your FREE download of MSN Explorer at http://explorer.msn.com
<http://g.msn.com/1HM504101/43> .
_______________________________________________ manet mailing list
[email-masked] https://www1.ietf.org/mailman/listinfo/manet

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 07:13:55 -0600

Dear Berner,

 
 
John Mullen  

-----Original Message-----
From: Philippe Jacquet [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re: [manet] Ad-Hoc compared to TETRA

Dear Berner,

 
Philippe

----- Original Message ----- 
From: Berner Vegge <mailto:[email-masked]>  
To: [email-masked] <mailto:[email-masked]>  
Sent: Wednesday, June 19, 2002 9:19 AM
Subject: [manet] Ad-Hoc compared to TETRA

Hello! 

Thanks for your help! 

Best Regards Berner 

  _____

---

From: "Vincenzo Cipolla" <[email-masked]>
Date: Wed, 19 Jun 2002 15:47:48 +0200

Dear John,

just a short  clarification.

Implementing MANET systems using TETRA Direct Mode(DMO) operation doesn't
require, by definition of the ETSI TETRA standards, any use of Tetra Base
Station or Tetra Network capability.

In other words the emergency services could operate in the scenarios that
you are highlighting using only DMO TETRA Terminals implementing  the MANET
paradigms.

BR,

Vincenzo Cipolla

"Mullen, John P. (Contractor)" <[email-masked]>
@ietf.org on 19/06/2002 15.13.55

To:   [email-masked]
cc:

Subject:  RE: [manet] Ad-Hoc compared to TETRA

Dear  Berner,

I  would add to Philippe that the term "MANET" describes a type of
communications  situation in which all elements of the network are apt to
be in motion, rather  than a particular standard or implementation.  TETRA,
on the other hand, is  a specific solution to a problem, which as Philippe
points out, is somewhat  different.  In any event, I don't think it is
possible to compare the two,  since they are two different things.  One can
only say whether or not TETRA  is a reasonable solution to the MANET
problem.

Certainly, elements of TETRA may be helpful in dealing  with the MANET
problem, but the very fact that TETRA relies on base stations  would rule
out its entire adaptation as a general solution.  For example,  if
emergency services are extended into an area that has suffered an
earthquake  or hurricane, it is likely that any base stations, towers, etc.
would be  unusable and the system would have to depend solely on what the
service agencies  bring with them.  This would be a MANET problem.

While,  in my opinion, urban and suburban police and other emergency
communications  would be more resilient if they had at least a capability
to function as a  MANET, I recognize that in most situations, the added
routing efficiency due to  base stations is beneficial.  In addition, there
needs to  be a sufficient number of nodes in a area to support a  MANET.
In extreme rural areas, there would be too few mobile police  and other
emergency units, so both base and relay stations would be necessary
(unless one relies on satellites or includes other, non-public service
users in  the MANET).

John  Mullen
-----Original Message-----
From: Philippe Jacquet  [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002  3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re:  [manet] Ad-Hoc compared to TETRA

Dear Berner,

TETRA is a mobile networks specificaly dedicated  for police, fireman and
ambulance. It is based on a base station architecture  like GSM and
provides similar low throughput. MANET is a mobile network based  on
multihop routing but is not dedicated to specific applications. Since the
hop distance can be small, ad hoc architecture is suitable for high speed
data  transfer such as in IEEE 802.11.

In WTC attack 15 base stations were knocked out  and the remaining base
stations isolated from network were unable to route  data between them.
This is probably a situation where an ad hoc technology  could help (see
WERT recommendation). I don't know whether TETRA can do that  either.

Philippe
----- Original Message -----
From:  Berner Vegge
To: [email-masked]
Sent: Wednesday, June 19, 2002 9:19  AM
Subject: [manet] Ad-Hoc compared to  TETRA

Hello!

   From this I wonder if TETRA and Ad-Hoc are competing technologies in
   the same market or complementary in some ways. Is it e.g. relevant to
   use  an Ad-Hoc network out in the field in a rescue operation and then
   use  TETRA for communication towards hospitals etc?
   I also wonder what the benefits of using Ad-Hoc compared to TETRA are.
   Can anyone help me?

Thanks for your help!
Best Regards Berner

---

From: "Vincenzo Cipolla" <[email-masked]>
Date: Wed, 19 Jun 2002 15:47:48 +0200

Dear John,

BR,

Vincenzo Cipolla

To:   [email-masked]
cc:

Dear  Berner,

John  Mullen
-----Original Message-----
From: Philippe Jacquet  [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002  3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re:  [manet] Ad-Hoc compared to TETRA

Dear Berner,

Philippe
----- Original Message -----
From:  Berner Vegge
To: [email-masked]
Sent: Wednesday, June 19, 2002 9:19  AM
Subject: [manet] Ad-Hoc compared to  TETRA

Hello!

Thanks for your help!
Best Regards Berner

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 09:24:59 -0600

Dear Vincenzo,

Thanks for the information.  I was under the impression that direct mode was
only capable of supporting local communications, rather than a full network
(say 100 or more nodes) over a wide area (say several counties).  Also,
according to the press release below, those nodes using direct mode cannot
communicate with nodes using normal TETRA operation.  

http://www.nokia.com/networks/pmr/tetra_terminals/models_tmr420.html

But, it wouldn't be the first time that a press release was in error.

:-)

John Mullen

-----Original Message-----
From: Vincenzo Cipolla [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 7:48 AM
To: [email-masked]
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

Dear John,

BR,

Vincenzo Cipolla

To:   [email-masked]
cc:

Dear  Berner,

John  Mullen
-----Original Message-----
From: Philippe Jacquet  [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002  3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re:  [manet] Ad-Hoc compared to TETRA

Dear Berner,

Philippe
----- Original Message -----
From:  Berner Vegge
To: [email-masked]
Sent: Wednesday, June 19, 2002 9:19  AM
Subject: [manet] Ad-Hoc compared to  TETRA

Hello!

Thanks for your help!
Best Regards Berner

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 09:24:59 -0600

Dear Vincenzo,

:-)

John Mullen

-----Original Message-----
From: Vincenzo Cipolla [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 7:48 AM
To: [email-masked]
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

Dear John,

BR,

Vincenzo Cipolla

To:   [email-masked]
cc:

Dear  Berner,

John  Mullen
-----Original Message-----
From: Philippe Jacquet  [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002  3:34 AM
To: Berner Vegge; [email-masked]
Subject: Re:  [manet] Ad-Hoc compared to TETRA

Dear Berner,

Philippe
----- Original Message -----
From:  Berner Vegge
To: [email-masked]
Sent: Wednesday, June 19, 2002 9:19  AM
Subject: [manet] Ad-Hoc compared to  TETRA

Hello!

Thanks for your help!
Best Regards Berner

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Wed, 19 Jun 2002 11:57:56 -0400

The direct mode appears to be a short range option, for groups of terminals which are close together, but out of range of a base station. Is it like using walkie talkies? Just broadcast on a given frequency? Hard to say from the Nokia description, but that's the implication.

Why isn't Tetra an option, similar to IEEE 802.11, to use as physical and link layers under MANET? It would seem to me that Tetra or 3G cellular would provide similar functionality at the lower 2 layers. And it seems to me that using Tetra with a base station, or IEEE 802.11b in so-called "infrastructure mode," allows one to layer IP over these schemes without any need for MANET. They just become extensions of the cabled Internet, used this way.

Bert

> From: Mullen, John P. (Contractor)
> [mailto:[email-masked]]
> Sent: Wednesday, June 19, 2002 11:25 AM
> To: Vincenzo Cipolla
> Cc: [email-masked]

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 10:41:15 -0600

Hi Bert,

I infer from your last sentence that you consider "MANET" to be some sort of
commercial package.  Just to make it clear, "MANET" describes a type of
communications situation, not a product or particular implementation.  The
term simply means "Mobile Ad Hoc Network" and any network that fits that
description could be termed a "MANET."  The working characteristics of
MANETs arise as logical consequences of that fundamental description.  For
example, most people agree that "mobile" implies "wireless."  Any number of
protocols and commercial products could be considered solutions to at least
some MANET problems.

Also, I want to make clear that there are degrees of "MANET"ness.  In the
MANET model, for example, all nodes could be mobile, while in practical
situations, that may not be the case.  

As far as I can tell, the real juicy problems in MANETs are at the lowest
two or three levels.  This is where the MANETS differ most from conventional
nets.  For example, link capacity varies continuously and randomly, so one
has to find a way to sort trivial changes from important ones to avoid
congesting the net with too many update packets.  If you can manage the
problems at level three and below, then the upper levels can look pretty
much that of like other networks.  

So, if you are saying that there are situations in which at least some nodes
are mobile in which TETRA would perform well, I would say that most people
would agree.  However, whether or not those situations are sufficiently
messy enough to be considered a MANET type of situation is debatable.  I
think each of us colors the MANET definition a bit by the nature of networks
we work with.  For example, I'm working in military tactical communications
networks, which is probably as "MANET"ty as one can get.  In fact, given
that the enemy is expected to try to disrupt the network, maybe a little too
"MANET"ty.

:-)

So, TETRA might be able to perform as a MANET under certain conditions.  I
really don't know enough technical details to say.  However, to say that it
is an alternative to a MANET is akin to saying a Chevrolet is an alternative
to an automobile.

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 9:58 AM
To: 'Mullen, John P. (Contractor)'
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

The direct mode appears to be a short range option, for groups of terminals
which are close together, but out of range of a base station. Is it like
using walkie talkies? Just broadcast on a given frequency? Hard to say from
the Nokia description, but that's the implication.

Why isn't Tetra an option, similar to IEEE 802.11, to use as physical and
link layers under MANET? It would seem to me that Tetra or 3G cellular would
provide similar functionality at the lower 2 layers. And it seems to me that
using Tetra with a base station, or IEEE 802.11b in so-called
"infrastructure mode," allows one to layer IP over these schemes without any
need for MANET. They just become extensions of the cabled Internet, used
this way.

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 10:41:15 -0600

Hi Bert,

:-)

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 9:58 AM
To: 'Mullen, John P. (Contractor)'
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 11:06:02 -0600

-----Original Message-----
From: Daniel Hollos [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 10:55 AM
To: Manfredi, Albert E
Cc: 'Mullen, John P. (Contractor)'; [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

You are right, the TETRA DMO targets short distance kommunikations when
it's needed, either when a base station is reachable or not. The
max. distance in this mode is around 1km, I also tested it.

Yours, Daniel

> The direct mode appears to be a short range option, for groups of
terminals which are close together, but out of range of a base station. Is
it like using walkie talkies? Just broadcast on a given frequency? Hard to
say from the Nokia description, but that's the implication.

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 11:06:02 -0600

-----Original Message-----
From: Daniel Hollos [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 10:55 AM
To: Manfredi, Albert E
Cc: 'Mullen, John P. (Contractor)'; [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

Yours, Daniel

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Wed, 19 Jun 2002 13:15:46 -0400

> much that of like other networks.

John,

The way I see it, if you solve the routing problem at the link layer, such as using Tetra with base station, using IEEE 802.11 in infrastructure mode, or using 2.5G or 3G cellular, then the only problem left is potentially a problem with variable link capacity. But that is a standard IP problem, even in the wired Internet.

Every problem needs to be bound. In this instance, a standard, fixed Internet structure, with a few wireless links to hosts which would otherwise appear fixed as well, should not be considered under the MANET umbrella. Or if it is, it would be a trivial case.

> messy enough to be considered a MANET type of situation is 
> debatable.

Let's assume that Tetra in its "direct mode" is functionally like a walkie talkie net except that each mobile acts as a repeater (I'm not positive it is). If one wants to implement unicast communications over such a broadcast net, then MANET would provide added value. In this case, I would consider Tetra to offer a physical and link layer to MANET, similar to what IEEE 802.11 provides when used in ad-hoc mode.

But if one is happy to use the broadcast paradigm, then there is no reason to layer MANET over this, is there? Just broadcast the voice, or broadcast the data, over the link layer as provided, and perhaps use IP and UDP encapsulation if there's a reason to. I don't see anything MANET about this last approach?

Bert

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Wed, 19 Jun 2002 13:15:46 -0400

John,

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 11:40:31 -0600

Hi Bert,

I think we pretty much agree.

Whether or not a situation would classify as a MANET situation could be a
matter of kind or degree.  For example, I don't think a cellular network is
a MANET because the backbone is fixed.  Now, of course, a lightning strike
would knock out a tower and the system might be able to recover from this.
So, in a sense, the backbone is not absolutely fixed.  However, I think most
people would agree that even if the cellular net is self-healing, such a
rare event would not qualify the situation to be a MANET.

To me, an emergency services deployment would qualify if it involved a few
base stations, such as at command centers, together with a moderately large
number of nodes, some of which are out of range of the base stations, but
within range of each other.  If, without user intervention,  the nodes can
function as routers to enable those nodes that are out of the range of the
base station to behave as if they are just as much part of the net as those
in direct contact, the result would probably be a MANET.  I would further
expect that a large fraction of the nodes (80 or 90 percent) would be highly
mobile, frequently changing their ability to communicate with base stations
or each other.  One final thing would be that these nodes are capable of
communicating any voice, data, etc. that would be necessary in order to
manage the emergency services under these conditions.

Now, if you have a product that is affordable and performs these necessary
functions, then you have something useful.  I would also call it a MANET.

I'm not sure what to say about the last couple of sentences.  I get the
impression that you are treating "MANET" as a specific protocol or product.
I'm not aware of any use of the term in this way.  As far as I know, "MANET"
is a classification of network type, much like "leafy vegetable" is a
classification of food.  

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 11:16 AM
To: 'Mullen, John P. (Contractor)'
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

John,

The way I see it, if you solve the routing problem at the link layer, such
as using Tetra with base station, using IEEE 802.11 in infrastructure mode,
or using 2.5G or 3G cellular, then the only problem left is potentially a
problem with variable link capacity. But that is a standard IP problem, even
in the wired Internet.

Every problem needs to be bound. In this instance, a standard, fixed
Internet structure, with a few wireless links to hosts which would otherwise
appear fixed as well, should not be considered under the MANET umbrella. Or
if it is, it would be a trivial case.

> messy enough to be considered a MANET type of situation is 

Let's assume that Tetra in its "direct mode" is functionally like a walkie
talkie net except that each mobile acts as a repeater (I'm not positive it
is). If one wants to implement unicast communications over such a broadcast
net, then MANET would provide added value. In this case, I would consider
Tetra to offer a physical and link layer to MANET, similar to what IEEE
802.11 provides when used in ad-hoc mode.

But if one is happy to use the broadcast paradigm, then there is no reason
to layer MANET over this, is there? Just broadcast the voice, or broadcast
the data, over the link layer as provided, and perhaps use IP and UDP
encapsulation if there's a reason to. I don't see anything MANET about this
last approach?

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 11:40:31 -0600

Hi Bert,

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 11:16 AM
To: 'Mullen, John P. (Contractor)'
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

John,

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 14:37:53 -0600

Hi Bert, 

We seem to be in agreement, so I'm cutting most stuff for the sake of
bandwidth.

I use the area emergency response as an example of a situation in which
there are sufficient nodes to provide networking, but little or no
supporting infrastructure.  This is a rather unusual situation.  Usually, if
there is an opportunity to provide a fixed backbone, people will take it.
If a stub network will do it, that is usually a more reliable, less
expensive choice.  On the other hand, if there are too few nodes in an area
to support networking, then a MANET approach will not work and some sort of
infrastructure must be provided.  The area emergency response would be an
example of a situation with enough nodes to support networking would be in
an area that does not have a great deal of infrastructure.  Of course, other
examples are possible.

The bottom line is that no one with sense would implement a MANET unless it
was needed.  With varying link capacity and mobile nodes, the situation is
very difficult to manage.  A big problem is the unstable backbone.  In very
dynamic cases, the best we can hope for is the avoidance of chaos.

In all likelihood, MANET performance will always lag that of stable nets.
The varying topology of the MANET is a complication that fixed nets do not
have to deal with.  If someone does come up with something that works under
those conditions, in all likelihood, it work as well or better in a fixed
net.  

For example, one key feature of MANETs is their "ad hoc" nature.  The
ability to join (or leave) a net without being computer gurus or having to
call network services to hook us in is definitely a plus.  If a reliable way
to manage this is developed, it will probably become very popular in fixed
nets and, maybe in the near future, ad hoc nets would become the norm.
Thus, what could be, in the short run, an advantage of MANETS would quickly
become a common feature of most nets.

I don't think of "MANET" as a set of protocols, but a classification of the
communications problem.  MANETS differ in the frequency and degree at which
the topology changes, as well as node density, size, etc.  A protocol that
works well in one MANET may not work well in another.  One purpose of the
MANET working group is to attempt to come up with a single protocol that
works for all MANETs, but that protocol does not exist yet.  For now, there
are still MANET situations for which there are no good answers.  

But, that makes life more interesting.

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 12:42 PM
To: 'Mullen, John P. (Contractor)'
Subject: RE: [manet] Ad-Hoc compared to TETRA

<snip>

I think of MANET as a family of protocols, yes of course. I don't see
anything I said that implies I think MANET is a product, however.

I think it pointless to give anything a label if it isn't to set boundaries
around what this label describes. I would feel silly to call a couple of
walkie talkies a "MANET."

Years ago, when I was involved in the ATMF's wireless ATM working group,
someone gave an example of emergency crews on the scene using wireless ATM
among one another, for voice communications. But the example he described
was far more efficiently served by broadcast radios with frequency division.
Sorry, that didn't qualify in my book.

Same situation here, and I think we agree. It might make MANET sound more
impressive if one uses emergency crews as an example, but the risk is that
you'll be looking hard for an answer to a question no one asked.

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Wed, 19 Jun 2002 14:37:53 -0600

Hi Bert, 

John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Wednesday, June 19, 2002 12:42 PM
To: 'Mullen, John P. (Contractor)'
Subject: RE: [manet] Ad-Hoc compared to TETRA

<snip>

Bert

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Thu, 20 Jun 2002 10:24:15 -0600

Hi William,

Well, sorta...

In many civilian situations, the satellite is a good resource.  The UAVs
might be a bit much at this time, but their price will eventually come down.
For example, see

http://www.personal.psu.edu/faculty/l/n/lnl/rc/

In the military arena, a number of developers have hyped the satellite and
UAVs up, but they always do that with every project.

:-)

Both UAVs and satellites are vulnerable to a number of threats.  In the
first attempt to get an Army satellite up (late 70s), there was a delay in
establishing terrestrial stations.  By the time the Army got them working,
they discovered someone had pirated their satellite.  (Nothing sinister,
just some guy who saw an opportunity to make a few quick bucks and took it).
They had to modify their terrestrial stations to operate at higher power in
order to get the satellite back.  As far as UAVs go, the current philosophy
seems to be that they are best used where human pilots would be most at
risk, so their current attrition rate is pretty high.  It is hard to say how
long they would stay up if simply performing a relay function.  However,
their primary LOS advantage for communications also makes them an obvious
target.

Beyond that, neither are physically connected to each other, other nodes, or
any wired infrastructure.  Because they must rely on radio links to remain
connected, they can be jammed.  (Of course, the link from a mobile node to a
base station can be jammed, too, but not the wire link from the base station
to the backbone).  If we use geostationary satellites, we must have
sophisticated antennas to communicate with the satellite because of the
range (36,000 km).  If we use lower orbits we can use antennas with less
focused beams, but now the satellite is a moving target that must be tracked
by the node to remain in contact.  The UAV is a moving target, but
omnidirectional antennas would probably work.  Staying in its LOS footprint
might be a bigger problem.  

Neither are exceptionally good alternatives in certain locations.  For
example, in mountainous territory, there may be large regions in which
neither the satellite nor the UAV can cover.  In urban areas, there is a
similar problem.  For satellites in equatorial orbits, coverage is spotty in
extreme northern or southern locations.  Also, if you have cable TV, you are
aware of the problems caused by sunspot activity.  If you've seen satellite
reports on TV, you are also aware of the nearly two second round-trip delay,
which leads to an immense bandwidth product and associated difficulties with
network communications.

Because they do not necessarily have a reliable connection to each other or
the rest of the world, I would think of them more as relay nodes than base
stations.  I think their primary function is to provide sufficient node
density in an area to maintain connectivity in the MANET, but not as base
stations per se.

Developer hype notwithstanding

:-)

John Mullen

-----Original Message-----
From: Josephson, William [mailto:[email-masked]]
Sent: Thursday, June 20, 2002 9:31 AM
To: 'Mullen, John P. (Contractor)'; Manfredi, Albert E
Cc: [email-masked]
Subject: RE: [manet] Ad-Hoc compared to TETRA

One shouldn't forget that UAVs and satellites can play a part in a MANET.

So these can be the base stations.

---

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Thu, 20 Jun 2002 10:24:15 -0600

Hi William,

Well, sorta...

:-)

:-)

John Mullen

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Thu, 20 Jun 2002 12:43:16 -0400

> So these can be the base stations.

Agreed.

I'd break that down into different categories, to decide whether the system qualifies as a MANET or not.

1. If these satellite base stations are stationary with respect to the earth's surface, for example satellites in geosynchronous orbit that also provide routing services, then this would not qualify as MANET. The satellites are merely an extension of the fixed Internet.

2. If the satellites are providing "bent pipes" only, and the routers are stationary on the earth's surface, again, I don't see where the resulting IP structure would be a MANET. It would be an extension of the fixed Internet.

3. If the satellites (or manned aircraft or UAVs) are not geosynchronous, and are providing routing services for devices not located on those moving platforms, or are providing a link to the fixed Internet by continuously handing over to new links to the fixed Internet as the vehicle moves, then we have the difficult problem MANET addresses.

The qualifications in #3 are important, IMO. You can postulate a case where aircraft are connected to the fixed Internet via a satellite link, routing services are only provided for hosts on that aircraft, and the satellite link always ties the aircraft to a single location on the earth's surface, where a router connects to the fixed Internet. In this scenario, there again is nothing MANET about the network, IMO. The routing problem sees all the hosts on the aircraft as being in a fixed location with respect to the earth's surface.

Bert