services_sample-site-survey.pdf

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2004 Wirelessguys, http:// www.wirelessguys.com. All rights reserved. Confidential information. 1

SAMPLE Site Survey Customer information has been

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(Customer Name Here) WIRELESS SITE SURVEY RESULTS

(10-04)

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Participants: Company Name Telephone Email

Wirelessguys Karen Panet (805) 378-8590 x131 [email protected] Overview: (Customer) has had a wireless network installed at several of their facilities. The goal was to provide wireless access for their inventory system and client communications for their employees. The Access Points are Cisco 1200s. The antennas used are mostly an 8 dBi outdoor omni or an 8.5 indoor/outdoor diversity patch. The clients use a Teklogix device that is mounted to a forklift or hand held and they roam around the facilities quickly. Other clients are internal Cisco cards in laptops. Coverage of the wireless network is spotty. In lieu of available resources, (Customer) has contracted with WirelessGuys to perform a survey of the existing network, troubleshoot, and make suggestions for improving wireless coverage. The main survey was performed at the (Site) and (Site) Facilities. The Site Survey was performed on all floors and results of those readings are contained within this report. There are also three other facilities that have the same issues, but we did not physically visit them. The suggestions in this report could also be applied to the three other areas to improve performance. Survey Results The coverage of the wireless network is not consistent or contiguous in quite a few places. The main two reasons are:

1. The 8 dBi omni outdoor antennas are mounted upside down both inside the facility and outdoors.

These antennas are meant to be mounted with the connecting end down and the non-connected end up. Radiation for an Omni-directional antenna is shaped like a cone, it radiates down from the top of the cone in a circle to the ground. When the antennas are mounted this way, they are radiating into the air. There are ceiling mount versions of these antennas that could be mounted this way, but these are not them.

2. The access points are configured for diversity on both antenna ports. This means

that both antennas are sending and receiving at the same time and that can cause

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clients to bounce between antennas. Cisco Access points are designed to use diversity best when connected to Cisco diversity antennas. Since the antennas are close together and they are not diversity optimized antennas (like the Cisco ones), you should set one antenna to transmit and one to receive thereby making one cell as opposed to two. There is a setting in the Cisco radios to set the Receive Antenna and Transmit Antenna and you would want to set them to Left and Right respectively. Diversity is a way of overcoming multipathing, but it can also hinder a wireless network if not used correctly. Of course, the changes should be made and tests performed on every AP to optimize the antennas.

Another thing that could be contributing to the spotty coverage is the choice of antennas themselves. In our experience, Cisco APs work really well with Cisco antennas and not so well with third-party antennas. This is probably why the higher gain antennas were used, but we have found that even though you put a higher gain antenna on to try to push through the areas, they still do not work as well as the Cisco antennas do. The following are some readings from various sites in the (Site) Facility and (Site) Facilities as well as suggestions for improvements at the particular locations. (Site) Facility

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Test site was in the room in front of AP5. The RSSI should have been over 30 but was actually around 23. Cisco RSSI values are from 0-100 and should not be lower than 30. This is not an acceptable reading. Antennas on AP 5 are mounted upside down and antenna ports are both set for diversity. Recommend turning antennas right side up and setting transmit to left antenna and receive to the right antenna. Retest after these modifications have been made. If there is still not a sufficient signal, you can up the power but there is a very small signal from AP28 which is close to this one.

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From the wall, to the right of the office and left of AP 27, we can pick up 3 access points. All of them have good signal to the client. Once the antennas are pointed in the proper direction, it is possible that you would not need AP26 anymore. Of course testing should be done to make sure. A big problem is walking through the different areas and maintaining a signal. For example, when standing between APs 20 and 21, there are two APs within range with low signals, so the client will get poor signal quality because it will keep switching from one to another depending on which one has the best signal. You want that client hand-off to be more elegant. Once the antennas are turned right side up, there will be improvement. There are also quite a few places where the forklifts have accidentally hit the antennas and they are pointing in strange directions. These of course will have to be fixed, but relocating them might also be a better solution. You can switch out the antennas for 180 degree antennas that mount against a wall, or 90 degree antennas that mount in a corner. Different antennas mounted in areas where the forklifts wont hit them will help with over all stability. In a few areas there are 8.5 dBi 60 degree directional antennas. The horizontal beam width on these is only 3 degrees which is good for a point to point link, but not necessarily an application where client cards need to hand off to other APs in a timely manner. For example, from the hallway where a client would walk, the signal was extremely low to the AP and when we got closer the signal, of course, was stronger. Being up on a ladder at the beginning of the hallway made the signal as good as when we were 10 feet away from the AP. You can fix these issues by installing a different AP with a wider horizontal beam width, or try lowering the antenna by 2 to 4 feet and see if your signal gets better. The antenna is

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mounted over 10 feet above where the clients would roam so getting it a little closer to clients, but still higher, will improve signal. The power on most of the radios is turned way down. This was done at the request of (Customer) because of concerns that the APs would over power each other. Adjusting the power settings in a dense environment is an effective way of preventing interference from neighboring APs. However, sometimes you can hurt the performance by doing this. In a couple of areas, where you know you can not contact any other APs that share the same channel, it would be wise to turn up the power so that it would give clients plenty of signal. Clients require a minimum signal of -85 dBm to connect to the APs and have good signal quality which enables them to access applications. When the signal is turned down and there are several clients trying to connect at the same time, non-connection issues can occur. We would suggest testing all corners of each room and adjusting power as necessary. (Site) Facility

At this facility the antennas are again mounted upside down as shown in the pictures at the beginning of this document. Turning the antennas right side up will improve performance. This facility has an indoor/outdoor deployment of mostly APs for the Teklogix application, but also has a point to point bridge where the network is being extended to the facility from a building across the street. We do not have the data on that link, but we would suggest changing out the antennas to ones that are horizontally polarized and with a small beam width. This will help cancel out any interference with the client network and make that link more stable. Since this is an outside facility, neighboring APs will be a source of interference. We found many APs surrounding the complex and some are radiating at full power.

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The above is a small sampling of the surrounding APs. These APs also use the default channels of 1,6, and 11. We would suggest turning up the power on (Customer) APs to overcome any interference. We were also asked to use the spectrum analyzer to see if there was any interference in the 5GHz band for the BSU/SU link at the main office. We ran some logs that are inherent in the product and found that on the BSU log, the interference number was higher than is recommended.

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This indicates that there is some other equipment in the area that is around the same frequency. We scanned the band and found that the following frequencies are in use in the surrounding area: 5485 5665 5725 5775 5825 The frequencies that the Proxim units can be set to are: Channel Plan Frequency

Channel Plan Frequency

Channel Plan Frequency

4A 5743 5A 5740 6A 57404B 5764 5B 5757 6B 57544C 5785 5C 5774 6C 57684D 5806 5D 5792 6D 5781

5E 5809 6E 57956F 5809

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We would suggest using a plan that will be at least 20MHz away from any used or known channel. Plan 5B would probably work best. As always, testing after the change will need to be done. The last area of concern here was that the point to point bridges were not always working. When this happens, the network gets cut off to the rest of the network. We would need to get into the configuration of the Access Points to be sure, but AP5 has been indicated as a repeater of the bridge on the Box loading shed and we do not see how his is possible. The Box loading shed has a Yagi antenna pointed at another pre-existing bridge.

This Yagi is pointed away from AP5 which is a little to the left of this antenna.

We would need to communicate more to the internal IT associates in order to determine the correct configuration, but it is our understanding that the omni antennas above are trying to communicate with the Yagi. This is not a valid configuration for two reasons: APs cans be repeaters and APs without having two radios in the unit and the Yagi antennas are meant to communicate with another Yagi in a point to point configuration. If this is desired, then we suggest you get another AP and Yagi and install it near the existing one with at least 6 feet of separation. Then you can connect them with a cross-over cable or into a switch.

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Network Testing Testing the network was part of the diagnostic process. We tested the communication while wired into the network and then from a client to the AP in the office (AP1). The wired network performed well in general. We did not see any anomalies that would make us believe that something in the network was causing problem with the wireless network in general. With the AP 27, AP 28, AP5 triangle we did see some packet errors and long response times for being wired which supports the problems we experienced on the wireless side. AP15 also shows issues but this is an AP that has been accidentally hit by a forklift and the antennas are out of alignment.

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The results below were from pinging the access points for a couple of minutes at a time. The higher millisecond reading indicates that those APs might have connection issues:

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As you can see, when wired there are not many network related issues. The spikes here and there are normal. When wireless, there will always be some latency because it is inherent in the devices, but the rule of thumb is to add 20-50 milliseconds to what your wired network is clocked at. The following is a sample when connected to your wireless network:

As you can see the latency gets to be very high. This reading would indicate that there are issues with the transmitting and receiving of data on the wireless network. Antennas are the first thing we try to tweak when we see these kinds of issues. Summary Following the recommendations in the pages above will negate the issues that the wireless network has been having. Start with re-mounting the antennas and configuring them properly in the APs, then move to power settings, and finally possibly replacing some antennas. Testing throughout this process will assure you of success. If you would like Wirelessguys to perform the work, please call us and we can send you a quote.

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