Subject: [manet] question about bandwidth reservation

From: Bin Lu <[email-masked]>
Date: Wed, 10 Mar 2004 11:12:09 -0600 (CST)

Hi,

I have a question on bandwidth reservation in ad hoc networks:

Some MAC layer protocol that supports QoS (such as ieee802.11e) is using
Traffic Categories (different priority queues) to implement priority
differentiation. But this is just at one node, I mean it
doesn't consider the case of shared bandwidth, right? Considering
the characteristics of wireless networks, the bandwidth at a node is
actually shared by its neighboring nodes since the node can not send
packets to its neighbor if the neighboring node is also transmitting
or receiving from another node. IEEE802.11e doesn't consider this case,
right? or it doesn't need to?

I'd appreciate it if someone could clarify this to me!

Bin Lu

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From: Rex Buddenberg <[email-masked]>
Date: 10 Mar 2004 10:10:33 -0800

> I have a question on bandwidth reservation in ad hoc networks:

First, back up one level of abstraction:
	- at layer 3, QoS control is primarily a priority queuing issue.
	- at layer 2, QoS control is a media access issue.  How does a station,
in a shared media, get priority access (permission to transmit) when it
is in possession of urgent packets?  
> doesn't consider the case of shared bandwidth, right? 

The Traffic Categories only identify urgent packets; still begs the
question of how you get priority access.

In contention queues like all the .11 variants, you have no access
control that can handle the QoS needs.  All stations with traffic to
send compete, using a carrier sense algorithm to take turns.  This,
while better than nothing, has several shortcomings:
	- no way to handle more-equal pigs, as you pointed out
	- poorly equipped to handle silent hosts.  Wired ethernet (802.3) MAC
works on the assumption that everybody can hear everybody else.  802.11
stretches that but lives with the same assumption.  In a radio-WAN, we
have to trade that assumption in for one where all leaf nodes can hear
the base station but not necessarily each other.  Which drives you to
polling or scheduling MAC algorithms.  Both of these approaches can
handle priority access if designed properly.  
	- carrier sense algorithms trade off bandwidth efficiency for other qos
parameters (interactivity, low latency ... and simplicity of design).  

> Considering

.11 standards took a very large step forward -- we got vendor
interoperability and the prices for the gear went way down compared to
pre-802.11 wireless LAN equipment (got some of that in lab and it was
comparatively pricey).  But we didn't get 
	- bandwidth efficient MAC algorithm
	- decent security (the MAC addresses remain uncovered with WEP)
	- QoS controls -- which you cannot with a carrier sense algorithm in
any real sense.
	- layer 2 multicast

You might want to look at the 802.16 (aka WiMax) standards which, IMHO,
represent the next generation and fix a good deal of these problems. 
The MAC is a dual-queue reservation protocol and that does afford some
QoS control at layer 2.  
-- 
b

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From: "Chi-Hsiang Yeh" <[email-masked]>
Date: Wed, 10 Mar 2004 19:55:14 -0500

Hi,

At layer 3, QoS control is also a routing issue.

IEEE 802.11e employs different persistent factors (PF) for different traffic
categories. A higher-priority class has a smaller PF so that its contention
window (CW) and thus typical backoff times grow slower. Moreover, a
higher-priority class has a smaller AIFS required for sensing the carrier,
and thus has a better chance for access of the channel. Based on these two
mechanisms, 802.11e can differentiate the delay and bandwidth for different
traffic classes among nodes, not just within a node.

The problem with IEEE 802.11e for MANET is that its differentiation
capability is not effective in multihop wireless networking environments
(though 802.11e is fine for QoS provisioning in single-hop wireless LANs).
There have been several effective differentiation mechanisms proposed for ad
hoc networks though.

IEEE 802.16 is not appropriate for MANET.

Chihsiang
___________________________________________________________
Chi-Hsiang Yeh (Mr./Dr./Prof.)
Dept. of Electrical & Computer Eng.
Queen's University
Kingston, Ontario, K7L 3N6
Canada
 
phone:  +1 613-533-6368
fax:    +1 613-533-6615

e-mail: [email-masked] , [email-masked]
URL:    http://www.ece.queensu.ca/hpages/faculty/yeh/
___________________________________________________________

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Rex
Buddenberg
Sent: Wednesday, March 10, 2004 1:11 PM
To: Bin Lu
Cc: [email-masked]
Subject: Re: [manet] question about bandwidth reservation

	- at layer 2, QoS control is a media access issue.  How does a
station,

	- poorly equipped to handle silent hosts.  Wired ethernet (802.3)
MAC
	- carrier sense algorithms trade off bandwidth efficiency for other
qos

-- 
b

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From: Ram Ramanathan <[email-masked]>
Date: Thu, 11 Mar 2004 12:24:04 -0500

> There have been several effective differentiation mechanisms proposed 

Why is it not effective in multihop networking? If the idea is that 
lower priority packets get to wait longer and higher priority are quick 
out of the gate, why should it be affected by single/multihop?

Not arguing a case, just would be interested in a clarification.

Any papers on the subject of 802.11e-like things for ad hoc nets? Any 
paper that summarizes 802.11e?

-Ram.

---

From: "Philippe Jacquet" <[email-masked]>
Date: Fri, 12 Mar 2004 16:21:24 +0100

Ram,

One problem of multihop networks versus bandwidth reservation is that out of
range links interfer (hidden nodes, interference area larger than data
reception area, etc). As far as we know this greatly complicates bandwidth
reservation since reservation affects links and nodes that are not involved
in the path of data. This should fairly reduce the efficiency of local
priorities use. In fact it can be proven that finding a good route for
bandwidth that does not downgrade the bandwidth of existing connections is
NP hard (http://www.inria.fr/rrrt/rr-4876.html ). The result is fairly
independent on the MAC layer.

Philippe
----- Original Message -----
From: Ram Ramanathan <[email-masked]>
To: Chi-Hsiang Yeh <[email-masked]>
Cc: 'Rex Buddenberg' <[email-masked]>; <[email-masked]>; 'Bin Lu'
<[email-masked]>
Sent: Thursday, March 11, 2004 6:24 PM
Subject: Re: [manet] question about bandwidth reservation

---

From: "Jack Chan's Hotmail Account" <[email-masked]>
Date: Sun, 14 Mar 2004 16:09:54 -0500

Hi everybody,

    I am trying to test NIST's Kernel AODV implementation on my wireless
testbed. I have successfully poured the code into my wireless testbed.
However, we are not quit sure on how to test the performance of this routing
protocol. I have tried NFS (Network File Sharing) and SCP (remote command)
in Linux to send file to destination node through intermediate nodes, but it
seems these two functions do not work with AODV. Is there any better
suggestion to send file or create video conferencing to other nodes and
using AODV protocol?  What I am trying to do is to test the performance of
AODV by generating some control traffic. Any help would be greatly
appreciated. Thank you

Sincerely,
Jack Chan
----- Original Message ----- 
From: "Bin Lu" <[email-masked]>
To: "Ram Ramanathan" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, March 12, 2004 3:45 PM
Subject: Re: [manet] question about bandwidth reservation

> Here is a paper that gives an overview of the new features of IEEE
> 802.11e:
>
> "IEEE 802.11e Wireless LAN for Quality of Service", Stefan Mangold etc.,
> http://citeseer.ist.psu.edu/537394.html
>

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From: Bin Lu <[email-masked]>
Date: Fri, 12 Mar 2004 14:45:00 -0600 (CST)