Subject: [manet] RE : Re : basic routing protocol

From: "moez gadri" <[email-masked]>
Date: Thu, 24 Oct 2002 16:42:56 +0100

Hi,

Thanks for advice to search in www.google.com,

I'm interresting to QoS routing protocols for ad hoc networks, witch
are in general a variant of basic routing protocols, so i search a full
list of basic routing protocol. I found a list below in
http://www.cis.ohio-state.edu/~jain/cis788-99/adhoc_routing/index.html

there are other protocols like DREAM and RDMAR. but is it the full list
of protocol ? there is the question. 

table-driven Protocols:
DSDV - Dynamic Destination-Sequenced Distance-Vector Routing Protocol 
WRP - The Wireless Routing Protocol 
GSR - Global State Routing 
FSR - Fisheye State Routing 
HSR - Hierarchical State Routing 
ZHLS - Zone-based Hierarchical Link State Routing Protocol 
CGSR - Clusterhead Gateway Switch Routing Protocol 

on-demond Protocols : 
CBRP - Cluster based Routing Protocols 
AODV - Ad Hoc On-demand Distance Vector Routing 
DSRP - Dynamic Source Routing Protocol 
TORA - Temporally Ordered Routing Algorithm 
ABR - Associativity Based Routing 
SSR - Signal Stability Routing

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From: Girish Borkar <[email-masked]>
Date: Thu, 24 Oct 2002 12:06:35 -0400 (EDT)

Hi all,

I am having some trouble with some fundamental concepts in wireless
communication. Its about hidden and exposed nodes. I guess if I am clear
on one of those, I'll be clear on the the other too.

So, here is my confusion....

Lets say we have 2 nodes A and B and A is sending data to B. And, there
are other nodes (C, D and E)  around B that cannot hear A, but can
communicate with B.

			  E

		A ------> B	 C

 			   D

So are all of these nodes(C, D and E) considered hidden even though they
may not be trying to tranmit ?
OR
Are they considered hidden only if they try to transmit ?

Another question is ....

Does A have to be tranmitting to make any or all of C, D and E  as
hidden terminal(s) ?
OR...
Can we call C, D and E as hidden with respect to A even if A is not
transmitting ? Is there some term called "geographically hidden" ??

I hope my doubts are clear.

Any clarifications ??
Thanks

Girish Borkar

---------------------------------------------
Univ. of Delaware

Ph: 302-731-7504 (Home)
    302-831-3643 (Lab)
---------------------------------------------

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From: Girish Borkar <[email-masked]>
Date: Thu, 24 Oct 2002 12:06:35 -0400 (EDT)

Hi all,

			  E

		A ------> B	 C

 			   D

Another question is ....

Any clarifications ??
Thanks

Girish Borkar

Ph: 302-731-7504 (Home)
    302-831-3643 (Lab)

---

From: "Tao Lin" <[email-masked]>
Date: Thu, 24 Oct 2002 14:44:21 -0400

There are some of others listed in www.ietf.org => MANET group web site.

  ----- Original Message ----- 
  From: moez gadri 
  To: [email-masked] 
  Sent: Thursday, October 24, 2002 11:42 AM
  Subject: [manet] RE : Re : basic routing protocol

Hi,

table-driven Protocols:

on-demond Protocols :

---

From: "Tao Lin" <[email-masked]>
Date: Thu, 24 Oct 2002 14:44:21 -0400

----- Original Message ----- 
  From: moez gadri 
  To: [email-masked] 
  Sent: Thursday, October 24, 2002 11:42 AM
  Subject: [manet] RE : Re : basic routing protocol

Hi,

table-driven Protocols:

on-demond Protocols :

---

From: John Stine <[email-masked]>
Date: Thu, 24 Oct 2002 16:07:22 -0400

Girish,

    Hidden and exposed nodes are a phenomenon of carrier sensing and packet
sensing MAC protocols.  These protocols regulate access by the mechansim
where nodes defer from attempting to gain access when they sense another
node using the channel.  A hidden node is a node that does not hear the
transmission that a node within its range is receiving and thus does not
defer from attempting to gain access. (The reason for not hearing the
transmission can be distance, be an obstacle in the propagation path, be
being in the null of an antenna,  or in the case of DSSS, be the use of a
different code) When it tries to gain access it interferes with the
reception at the destination.  The exposed node problem is very different.
An exposed node is a node that hears multiple disjoint sections of a network
and never gets the opportunity to contend since it is always deferring to
someone.  Technically, Aloha, Slotted Aloha, and TDMA do not suffer from
these problems since they do not use carrier sensing to regulate their
access attempts.  Collisions may occur but this has nothing to do with them
hearing each other.  Carrier sensing protocols that provide no hidden node
suppression will perform as Aloha in congested environments.

So, in conclusion, in your example, hidden nodes only occur when you are
using a carrier sensing access protocol and there is nothing in place to
cause C, D, or E to defer from contending when A is sending data to B.  Your
illustration does not provide an example of an exposed node so consider the
following:

A   B      C      D   E
F   G             H   I

Say A, B, F, G, and C can hear each other and C, D, E, H, and I can hear
each other but A,B, F, G cannot hear D, E, H, I and vice versa.  Then C is
exposed to these two partitions in the network.  In order for C to contend,
both partitions must be quiet.  Addionally, all nodes in each partition have
the potential to be hidden nodes when a node in the opposite partition tries
to communicate with C.

The term "hidden node" and "exposed node" refer to the problems described
above, not really to the layout of the nodes.  So in the example above, C is
not exposed if no one else is transmitting.  Another way to understand this,
consider a continuous tessellation of nodes on a rectangular grid where each
node can hear transmissions up to two nodes away in each direction.  Such a
grid could be separted into partitions of transmitting nodes where any node
could be an exposed node at different times in its operation.  Similarly,
any node could be a hidden node.

John

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From: John Stine <[email-masked]>
Date: Thu, 24 Oct 2002 16:07:22 -0400

Girish,

A   B      C      D   E
F   G             H   I

John