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When I was doing the survey, I've encountered few places there was no signal strength. It was 0 only. But the packet transfer rate is almost 30-40 packets/sec.
And even the busses could able to communicate with the AP and then transfer the date to the main server as well.
We are using Proxim 802.11 AP only.
How come even though there is no signal strength we are able to getting the higher data transfer rate???

Why there is no reply for this???

Is the query was wrong or not clear???

If it is not clear I'll post it in clear manner later.

Yes, I'm afraid we're going to need much more information than this to be able to help you out. Sorry. :-)

About Our Site
We have a NT server that has our own software connected to switch and then few APs. And we are using omni as well as patch antennas depends on the situations. We have started to install this in year 1999 therefore we are still using 802.11 WLAN. We are using Proxim 7520 series of APs & EPs. Our Antenna gain is almost 7.5 dBi to 14 dBi.
Our client machines are fixed in the busses. That machine has proxim OEM module and antenna that can communicate with our AP and transfer the data from client machine to NT Server. And download configuration files from Server to client as well.

Most of our site are almost 0.6 km x 0.7 km size. And it has lots of trees, concrete building, bus washing bay (metal) & workshop (metal). And we have almost 500 - 600 buses parked during night time. And the buses are parked in more than 10 rows.

Our Site Survey

And we are using Proxim Range LAN2 card and the default proxim software to do the site survey.
In our site survey we are mainly check the average packets transfer rate using the proxim software as well as the signal strength. Our contractual requirement is to provide each point in the site atleast 20 packets/sec.

If we are very close to the antenna we used to get almost 70 packets/sec as well as 90% signal strength.

And if we are some what far away from the antenna then we used to get around 30 packets/sec and around 20-30% signal strength.

Our Problems

1. Sometimes we are getting good packets transfer rate around 30-50 packets/sec. But we are getting 0% signal strength.
Why this is happenening?

2. During day time when less buses are parked we don't get any BLIND SPOT. We used to get better packets transfer rate as well as the better signal strength also.
BUT during night time when almost around 500-600 buses are parked, few places we are having BLIND SPOT. We don't get desired packets transfer rate. And the client machine also cannot able to communicate with the server also.
In that case we used to move the buses where we are getting good signal and transfer the date to the server and then park it at its original position. But this is troublesome and we cannot do all the times.

I can understand since buses are made by metal and we have lots of trees, buildings we will have lots of multi path problem. But the customer is saying they want 100% coverage all the times.

What we can do to have better signal strength and better transfer rate all over the bus park and avoid all the blind spot.

If we can't get how should I make my customer to understand all these problem and compromise.

I'm expecting some suggections from your guys.

Please note that the following as well.

*** Day time when few buses (around 30-50) parked at the bus park the coverage is very good.

*** Only during night time when around 500-600 buses parked at the bus park, we are having this signal strength problem as well as blind spot also.

Most of our sites, concrete building is almost at one side. But trees are almost all over the site.

And almost 30-40% of the buses are double deck buses.

And our antennas are installed around 10m -12m height from the ground level. We cannot install higher than this because we cannot built our own tower and it is costly also.



We cannot install more APs because

1. We cannot get power source near by.

2. We cannot install the PoE because we need to dig the gorund and install and it will be very much costly.

*** We have tried to increase the Antenna gain and also we have tried to install the amplifier as well. But still we are facing few BLIND SPOTS as well as signal strength problem.

RangeLAN2 APs use Proxim's patented frequency-hopping spread-spectrum (FHSS) technology.

Consider a DSSS/ OFDM radio by Proxim if you desire.
http://www.proxim.com/products/wifi/ap/

A dual band b/g/ a AP may help. Give you more options and clients a higher throughput.

It may solve some of the multipath issues with the buses at night.


Another quick alternative is MIMO.


This is URL is an overview article. I will not promote any vendor persay , the IEEE standards are not released, but don't let this deter you from solving an issue that warrants this technology. Though infant, it has a fit.

http://www.businesssolutionsmag.com/Articles/2004_11/041116.htm

Hope this helps!

I'm thinking the buses are metal and are creating multipath like crazy. Depending on the network design going higher may help but it's very hard to tell.
"Only during night time when around 500-600 buses parked at the bus park, we are having this signal strength problem as well as blind spot also"