Subject: RE: [manet] Bandwidth vs Transmission Range

From: "#LI ZHIFEI#" <[email-masked]>
Date: Mon, 24 Nov 2003 12:48:39 +0800

hi,

I think the reason is: for higher transmission rate you need a higher SNR to receive the packet correctly. The SNR 
in turn depends on the distance between the communicating pair if all the other stuff are assumed as the same.
Therefore, when a higher transmission rate is used, the effective transmission range should decrease.

Best regards
li zhifei

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Prasanna.Padmanabhan-1
Sent: dilluns, 24 / novembre / 2003 05:15
To: [email-masked]
Subject: [manet] Bandwidth vs Transmission Range

Hello Everyone,

In one of the WLAN cards (Wireless LAN Mini PCI Type 3A card), I see that for higher bandwidth cards they offer, the transmission range decreases.

For example, a 1 Mbps WLAN card has a tranmission range of 550m,
a 2 Mbps WLAN card has a tranmission range of 400m,
a 11 Mbps WLAN card has a tranmission range of 160m.

Does that mean that bandwidth and transmission range are inversely proportional.
I understand transmission range is related to Power. But how is it related to Bandwidth?

Please let me know.
Thanks,
Prasanna

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From: "John Mullen" <[email-masked]>
Date: Mon, 24 Nov 2003 08:31:48 -0700

Hi Li,

Exactly!  Shannon's limit restricts the bandwidth of a reliable channel
to B log_2 (1 + S/N), where B is the channel bandwidth and S/N is the
ratio of signal to noise.  It is a theoretical limit which is
approached, but not surpassed, by some existing coding schemes.  It also
ignores interference and some other factors, but is useful in that it is
an upper limit.  Plotting the S/N due to expected power at a given range
will clearly demonstrate that data rate and bandwidth are linked.

Prasanna, it is also good to remember that such estimates may assume a
RF environment that is more stable than the one you are working in, so
you may not get the promised range.  Also, because of shadowing and
fading, you will find that dropouts and interference may be a problem at
even moderate ranges.

John Mullen

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
#LI ZHIFEI#
Sent: Sunday, November 23, 2003 9:49 PM
To: Prasanna.Padmanabhan-1; [email-masked]
Subject: RE: [manet] Bandwidth vs Transmission Range

hi,

I think the reason is: for higher transmission rate you need a higher
SNR to receive the packet correctly. The SNR 
in turn depends on the distance between the communicating pair if all
the other stuff are assumed as the same. Therefore, when a higher
transmission rate is used, the effective transmission range should
decrease.

Best regards
li zhifei

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Prasanna.Padmanabhan-1
Sent: dilluns, 24 / novembre / 2003 05:15
To: [email-masked]
Subject: [manet] Bandwidth vs Transmission Range

Hello Everyone,

In one of the WLAN cards (Wireless LAN Mini PCI Type 3A card), I see
that for higher bandwidth cards they offer, the transmission range
decreases.

For example, a 1 Mbps WLAN card has a tranmission range of 550m, a 2
Mbps WLAN card has a tranmission range of 400m, a 11 Mbps WLAN card has
a tranmission range of 160m.

Does that mean that bandwidth and transmission range are inversely
proportional. I understand transmission range is related to Power. But
how is it related to Bandwidth?

Please let me know.
Thanks,
Prasanna