Subject: [manet] Re: Calculating usy time in wireless channel

From: Jangeun Jun <[email-masked]>
Date: Tue, 10 Feb 2004 13:38:16 -0500 (EST)

Hi,
The real-time utilization of a wireless channel can be calculated from:

A. Given the MAC and Physical parameters with the frame size, determine
the minimum transmission time required to transmit the frame. Note that
the inverse of this minimum transmission time gives the theoretical
maximum throughput (i.e., TMT which indicates the throughput with the
maximum channel utilization)

B. Have a node capture all the frames on the fly and measure the
interarrival time.

The ratio of A to B gives an instantaneous (real-time) utilization of the
wireless channel being monitored.

A paper published in IEEE NCA 2003 (see below) provides an easy-to-use
table and formula one can immediately apply. Furthermore, the paper
comes with a downloadable software package that monitors the
real-time channel utilization based on the table & formula.

Hope you find this helpful and convenient.
Regards,

-Jangeun Jun

Jangeun Jun, Pushkin Peddabachagari and Mihail Sichitiu,
"Theoretical Maximum Throughput of IEEE 802.11 and its Applications,"
in Proc. of the 2nd IEEE International Symposium on Network Computing and
Applications (NCA'03), Cambridge, MA, April 16-18, 2003, pp. 249-256.

> Message: 1
> From: "yazeed al-sbou" <[email-masked]>
> To: [email-masked]
> Date: Mon, 09 Feb 2004 18:03:15 +0000
> Subject: [manet] Calculating usy time in wireless channel
>
> Hi all....
> Could anyone please tell me how the busy time in a wireless network
channel can
> be calculated to be used for estimation of the channel utilization...???
>
> Any help is appreciated..
> YOURS..
> Yazeed Ahamd Al-Sbou
> School of Engineering
> Sheffield Hallam University
> Sheiffield
> Tel. 00441142424419,
> Mobile 00447813402741
> [email-masked]
> United Kingdom

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---

From: "John A. Stine" <[email-masked]>
Date: Tue, 10 Feb 2004 15:01:41 -0500

In ad hoc networks the utilization of a wireless channel is not so linear.
An objective of ad hoc networking is to spatially reuse the channel and so
capacity has a volume and range component, i.e. bps across a distance per
volume. Assuming a terrestrial system, volume can be reduced to area and so
the units of capacity can be reduced to bits/(secs * distance).  Measuring
this is difficult since it is so dependent on scenario.  Ideally, an access
protocol will fix the capacity of a physical volume in a way that is
independent of scenario factors such as the density of contenders.
Utilization would then be the average spatial use divided by this capacity.

The best known papers on this subject are by Gupta and Kumar but they try to
determine end-to-end capacity of an ad hoc network using the scenario
assumption that every node is equally likely to communicate to every other
node.  This is different than the spatial capacity of a channel. In the
former, capacity is dependent on the size of the network whereas, as
mentioned above, channel capacity should be independent of the size of the
network and density of contenders, just dependent on the range of
transmission and the rate at which bits are transmitted. One of the
shortcomings of most access protocols is that this is not true.  Early work
by the likes of Tagachi, Kleinrock, Silvester, and Nelson show that the
capacity of Aloha and CSMA type protocols remain sensitive to node degree.
Also, despite the access protocol, capacity will remain a function of the
placement of nodes.  So we can then start the argument that optimum capacity
has to be determined for a given placement of nodes before we can make an
assessment of utilization.

I really haven't answered the question, but the reason for that is, as I
have written, it is not an easy question to answer.

John

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Jangeun Jun
Sent: Tuesday, February 10, 2004 1:38 PM
To: [email-masked]
Cc: [email-masked]; Mihail L Sichitiu
Subject: [manet] Re: Calculating usy time in wireless channel

Hi,

A. Given the MAC and Physical parameters with the frame size, determine the
minimum transmission time required to transmit the frame. Note that the
inverse of this minimum transmission time gives the theoretical maximum
throughput (i.e., TMT which indicates the throughput with the maximum
channel utilization)

A paper published in IEEE NCA 2003 (see below) provides an easy-to-use table
and formula one can immediately apply. Furthermore, the paper comes with a
downloadable software package that monitors the real-time channel
utilization based on the table & formula.

-Jangeun Jun

Jangeun Jun, Pushkin Peddabachagari and Mihail Sichitiu, "Theoretical
Maximum Throughput of IEEE 802.11 and its Applications," in Proc. of the 2nd
IEEE International Symposium on Network Computing and Applications (NCA'03),
Cambridge, MA, April 16-18, 2003, pp. 249-256.

channel can