Subject: RE: [manet] Extension to 802.11 needed for MANET?

From: "#LI ZHIFEI#" <[email-masked]>
Date: Fri, 7 Nov 2003 11:02:04 +0800

Hi,

I would comment my understanding as follows:

IEEE 802.11 operates well in a single-hop network (at least it can run in the practical scenario though QoS can not be ensured).

However, when IEEE 802.11 is adopted into multi-hop scenarios, the performance is really not promising as shown by many papers.
The key problem of IEEE 802.11 in multi-hop scenarios is that it cannot cope with the inteference from neighborhood nodes in an efficient manner.
The inteference problem is in turn mainly due to the following assumptions: single channel in the whole network, omi-directional antenna, 
and symetrical transmission power. That is why many work have introduced multi-channel (or sometimes busy-tone channel), directional-antenna,
and power control (from inteference point of view) into multi-hop ad hoc networks. Regarding to these issues, please see the tutorial of 
mobihoc 2002 given by professor Nitin Vaidya.

However, when we use multi-channel , directional-antenna, and power control, IEEE 802.11 may need considerable modifications or
we may have to design totally new MAC protocols. Therefore, when we talk about modifications of IEEE 802.11 in multi-hop sceanrios,
there may be two options: 
(1) extend IEEE 802.11 into multi-hop ad hoc networks while still keeping assumptions of single channel, 
omi-directional antenna, and symetrical transmission power?
(2) extend IEEE 802.11 into multi-hop ad hoc networks with multi-channel (or sometimes busy-tone channel), directional-antenna,
and complex power control ?

Now, my questions are: Is it technically possible for the above two options? If yes, which one is better in the multi-hop ad hoc networks?

Best regards

Li zhifei

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Chi-Hsiang Yeh
Sent: dimarts, 4 / novembre / 2003 20:57
To: [email-masked]
Subject: [manet] Extension to 802.11 needed for MANET?

Hi,

I'll appreciate your opinions toward the following issue.

In the literature, IEEE 802.11 is the most commonly assumed MAC protocol
for ad hoc networks. Most ad hoc network testbeds are also built based
on IEEE 802.11. However, some problems (e.g., concerning power control,
interference, QoS, directional antennas, security, or radio efficiency)
will be introduced when the MAC protocol of IEEE 802.11/11e is applied
to multihop networking environments, leading to inefficiency and
difficulties in QoS provisioning.

Do you think we need an extension to the MAC protocols of IEEE 802.11
and 802.11e for ad hoc networks and multihop WLANs?
 
Chi-Hsiang Yeh
___________________________________________________________
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/
___________________________________________________________

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