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Radio AP with Integrated Antenna for Outdoor Usage...

Hi friends !

Previously I had posted a question regarding Wireless Implementation. I am going to implement wireless in my workplace. My workplace covers 1 to 1.5 km. circular area and it has huts/blocks at some distances. It does not have building-like structure.

Previously I was suggested to use Radio AP with Omni-Directional Antenna. I searched some sites and I found that Cisco and D-link products will be very expensive. I am looking for some low budget solution. So I am looking for Linksys, a division of Cisco system that provides equipments on low cost.

I explored the www.linksys.com site. I found some products there. Here is the short list of these products:


1. WAP54GPE  Wireless-G Access Point with Power over Ethernet
High-Speed Wireless Access for Exterior Environments

RF Power (EIRP) in dBm: 11.g: Typical - 14 dBM
                                           11.b: Typical - 18 dBM
Antenna Gain in dBi: 9 dBi

***************************************************************************************************************************

2. WRT100  RangePlus Wireless Router
Expand Your Wireless Coverage with MIMO

RF Power (EIRP) in dBm: 16.5 dBM
Antenna Gain in dBi: 1.8 dBi


***************************************************************************************************************************

3. WAP200  Wireless-G Access Point with Power over Ethernet and RangeBooster High-Speed Wireless Access for Exterior Networks

Transmit Power in dBm: 11.g: Typical - 14 dBM
                                        11.b: Typical - 18 dBM
Antenna Gain in dBi: 2 dBi
Two Omni Directional Antennas


***************************************************************************************************************************

4. WAP54G  Wireless-G Access Point
Add High-Speed Wireless Access to Your Wired Network

Transmit Power in dBm: 11.g: Typical - 13.5 +/- 2 dBM
                                        11.b: Typical - 16.5 +/- 2 dBM
Antenna Gain in dBi: 2 dBi
Two Omni Directional Antennas


***************************************************************************************************************************


5. WRT300N  Wireless-N Broadband Router
Start a Wireless Network With Up To 4X the Range and 12X the Range

Transmit Power in dBm: 17 dBm
Antenna Gain in dBi: 2 dBi
Three Omni Directional Antennas


***************************************************************************************************************************

I have the following queries to ask&

1. How can I measure the Signal Range propagated by the product ? Previously I was suggested to use a Wireless Range Calculator but I couldnt understand it.

2. What is better for covering more area ? More Antenna Gain or Less Antenna Gain !!! More RF Power or Less RF Power !!!


Note: In some of the above products, Antenna Gain is very low  i.e. 2 dBi, 1.8 dBi. Only one product WAP54GPE ( Product No. 1) has Antenna Gain: 9 dBi and can be placed on the roof. (Outside)

Please tell me which of these products may be suitable for my workplace the coverage at least 700-800 meters circular area ?

I have given maximum points to this question as it is very important for me to know the suitable product for my workplace.

Thanks,

Hemant




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JatinHemant
Asked:
JatinHemant
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3 Solutions
 
TreyHCommented:
Are you trying to cover the entire work area with one wireless access point or are you trying to connect each individual building together. The usual approach is to connect the buildings using wireless bridge/directional antennas . Then each building could have it's own wired network or it's own access point to cover it's immediate area. If you are trying to use one access point to cover the entire area, you'll have to remember the weakest link will be the workstations/laptops TX pwr. You can have the max dbi/tx power on the access point but a built-in wireless card on a laptop might not be able to transmit back to the access point. A number of wireless guys use the example of a game of catch: If you can throw a ball 700 meters but I can only throw a ball 50 meters, the game's not much fun if we are over 50 meters apart.....
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JatinHemantAuthor Commented:
Thanks for your quick reply and sorry for not responding instantly...

You see, I want to cover entire work area (approx 800 meters) with one Radio AP with antenna. As I told you that I am looking for low cost linksys products, I found that WAP54GPE  Wireless-G Access Point with Power over Ethernet (Serial No. 1 in my first post) may be suitable for it. It can be placed outside on the roof. The signal strength of thisequipment is :

RF Power (EIRP) in dBm: 11.g: Typical - 14 dBM
                                           11.b: Typical - 18 dBM
Antenna Gain in dBi: 9 dBi

But as you explained me with the example of game of catch, I got the concept that if my wireless receiver (typically Wireless Cards in Laptops/notebook PC or External Wi-Fi Cards in Desktops)
are not able to send the signals back with the same efficiency of Radio AP, then they will not get internet.

Q: 1 Please explain me what is better, to use Small-small APs in different different places or using this Power Outdoor AP - WAP54GPE ?

Q: 2 How can I know that what is the range of this WAP54GPE equipment ? (They have only given RF Power and Antenna Gain). So with these parameters, how can I evaluate the range ot this product ?

Q:3 How can I know that what is the TX Power of the wireless card in the laptop ?

Thanks,

Hemant
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TreyHCommented:
To cover the amount of area you are talking about, you will probably have to use multiple AP's dispersed equally about the area. I'm not really a wireless guru, I just go with rules of thumb and trial and error most of the time. If your wireless clients will primarily be workstations and laptops using built-in wireless cards, they will need to be within 120meters of the AP. That's under ideal conditions (outside & line of site). If they will be indoors, I'd say they would need to be within 60meters. Also, most AP's will only handle about 20 users at a time. I'ts better if you keep it to around 10 users per AP.
As to determining the range of a piece of equipment, it's best to refer to the manufacturer and their recommendations. There are so many factors involved that it's hard to go by any of the calculators to get a reliable answer. Sounds like in your situation the laptops are going to be the weakest link anyway and so about 120 meters is your max to the closest AP.
I would recommend that you use wireless bridges to connect each building/work area. Then each building could have its own network (wired or wireless AP).
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JatinHemantAuthor Commented:
Thanks TreyH !

In this discussion, Many of my doubts are cleared. Specially with the example of game of catch, I got the real concept of wireless networking. You are right that if I can throw ball 700 meters but you can throw it only 50 meters then there will no fun in the game. This is definately true in Wireless Networking also.

Q:  As you told me that there is no exact calculator that can give reliable answer regarding range of a wireless equipment, will you please tell me if at least we can ourselves calculate the range of the wireless equipment in approximation, if we place it in open space ? I am sure that just looking on the RF Power of the AP and Gain of Antenna, we can atleast know the approximate range capacity.

Thanks,

Hemant




Thanks,

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TreyHCommented:
You can get an approximate range for you wireless system by calculating the power budget or margin for the equipment being used. You have to figure in both ends of the system (An access point and a laptop for example). The rule of thumb is to have a power margin of 5db or better. I actually won't try it unless I have 8db or better. Here's a link to a page that shows the calculation. It can get quite confusing.

http://www.solwise.co.uk/los.htm
http://www.zytrax.com/tech/wireless/calc.htm#system

One important thing to keep in mind when choosing equipment is Receive Sensitivity of the radio. The receive sensitivity is actually more important than TX power. The receive sensitivity is the lowest db the unit can 'hear' and still accept it as a good signal. Lots of people simply look at TX power when choosing equipment and that can be a mistake. For most all my mid-range building bridges I've been using the D-LINK 2200AP. It has good TX and RX and the power output is adjustable so you can use high gain antennas and still stay within legal limits.

There are so many factors that can affect a wireless link that the only sure way to determine range is a site survey. A site survey is actually setting up some equipment and see if you can get a link. I'll use the calculators to get a ballbark idea when planning but that' about it. I always do a site survey before I tell anyone it will work. Also, the link I included has some reading about the Fresnal zone (pronounced fra-nel). Many first timers don't factor that in and it's important. If you have line of site between two points but some trees are within the Fresnal zone - the link might not work even though you have line-of site.
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JatinHemantAuthor Commented:
Thanks for your nice explaination.

From this discussion, I really knew concepts of wireless. Let me go through more documentations.

Thanks again.

Regards,

Hemant
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