TP-LINK outdoor access points mainly used for long distance transmission in many scenarios. Among these, PtP topology is a typical application, and distance most common used varies from 1~4km so we take 4km for example to explain how to build a PtP link. Now let’s begin the experience sharing.

Preliminary investigation

Testing environment
Since wireless performance has something to do with real environment, it’s important to select a suitable location for field test. Factors to be concerned contains obstructions, interference, etc. For this field test, we finally located two sites at Dameisha beach after times of research.
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Refer to above map, the two places are at a distance of 3.8km that it is a significant distance to test throughput. In addition, there is no obstructions over the sea so the 1st Fresnel zone between the two access points is surely clear. Last but not least, the wireless link could be more stable with few interference source around by the sea.
As for most place in the city/town where buildings are normally in access points’ way we could only mount the devices as high as possible.

Selection of access point
In PtP topology, we don’t need a wide coverage so almost all TP-LINK outdoor access points are suitable for this scenario. Considering the using distance, 4km is so short that both CPE210 and CPE510 are feasible models. Another factor we should pay attention to is interference and in this regard CPE510 is better choice than CPE210 since it works on cleaner 5GHz frequency. With above advantage finally we put CPE510 into use.

Materials preparation
Here we don’t talk about detailed material needed but recommend some helpful tools:
  • Laptops – Necessary for field test and should be installed with speed test software like IxChariot.
  • Long network cable – Since device might be installed far away from outlet a long cable is very useful.
  • Smart phone – Apart from communication function, a smart phone could help to roughly align device’s direction.
  • Spider – With this tool we are able to change the position and height of device flexibly.

Field deployment

In the following is real deployment step by step.

1. Device installation
When using tripod, installation of device becomes so simple. What we have to do is mount the device higher than obstacle before and use the attached ribbon to fix it.Name:  2.png
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2. Rough alignment
Before software configuration, generally we take a rough alignment for sure that Client device is in good coverage. In this procedure, we use a smart phone to share the position to our partner. Afterwards open an application with Map service. With the help of arrow, we can tune smartphone to face the other side and adjust front panel of access point to face this orientation.
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3. Channel optimization
Then, use the Spectrum Analysis tool on Web-UI for frequency scan and select a relative clean channel for AP. Channel optimization is necessary because without this step the AP is possible to work on busy channel, which results in inaccurate alignment and bad throughput performance.
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From the above analysis we can see 5300~5700MHz is clean so corresponding channel from 60 to 136 is good choices for AP.

4. Software configuration
This step we configure basic setup of AP and have the Client to connect to it. Pay attention to some key parameters such as distance and region, etc. And if you see information of root AP in red box, that means Client has connected to AP and then we can take precise alignment.
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Kindly note that distance parameter is recommended to set as approximately 110% of real distance. That’s why distance is 4.0km.

5. Precise alignment
After Client device connects to AP, we can start to align precisely. Generally we take this procedure on both sides to obtain better alignment. Take Client side for example, we generally tune the device little by little until signal strength/SNR reaches maximum like below image shows. The tuning operation should be done intermittently since transmit delay in a distance of 4km should be taken into consideration.
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Throughput test
So far, we have finished all testing environment. Now we’re able to have a throughput test to see whether the performance meets bandwidth requirement. Topology as below:
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There are different tools for throughput test and here we use IxChariot. As above PC_A is installed with IxChariot Console and PC_B installed with Endpoint. Kindly note that the version of Console and Endpoint should be the same. Running the program, we got finally result as below:
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Data showed inside red box is the real time throughput during 1 minute and 93.963Mbps indicates that the performance of device is pretty well so this location is a good choice for ultimate deployment.
Of course we can change the setup to meet demand in different application. For example, we have enabled MAXtream on AP to see if this TDMA protocol makes improvement when there is only one client. Similarly we can change operating channel to congested one to test anti-interference ability.

Annex - Troubleshooting
In field test, we may meet a lot of unpredictable problem. To finish test project in finite time some practical troubleshooting skill is needed. This part shares tips for frequently meet questions:
1. Fail to find AP’s SSID in Client side.
  • Use the smartphone to search the SSID of AP to see if AP successfully broadcast SSID.
  • Turn the orientation of both devices to face to each other for sure that Client is under coverage.
  • Check whether Client’s region option same as AP.
  • Check whether channel width on Client same as AP.
  • Check whether AP works on a DFS channel. For DFS mechanism refer to FAQ763
  • Check whether AP enable Wireless Radio and SSID broadcast option
2. See AP’s SSID but Client device couldn’t connect to it
  • Check whether Client’s connection type is of type ‘Dynamic’ while AP doesn’t enable DHCP.
  • Check whether distance setting on both devices correct.