Wireless Feasibility Survey And Site Survey For Sandersville, GA. Jay Sexton and Jeffrey Lee Georgia Tech Research Institute

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1 Wireless Feasibility Survey And Site Survey For Sandersville, GA Jay Sexton and Jeffrey Lee Georgia Tech Research Institute On November 7-8, 2001, two representatives from the Georgia Tech Research Institute traveled to Sandersville, GA, to study the feasibility of delivering wireless Internet service to that area. The GTRI representatives were Jay Sexton, a Research Engineer with the Information Technology and Telecommunications Laboratory, and Jeffrey Lee, a student in the Georgia Tech cooperative study program. This is a summary of the tests performed, the results of the tests, and the recommendations based on these results. Test Descriptions and Results The first test that was performed was to assess the possibility of the city providing a point-to-point wireless connection to a facility belonging to Imerys, a French-owned kaolin company. The facility that is to be connected is located in Deepstep, a community about 11 miles WNW of downtown Sandersville. This link distance would require the erection of tall towers (at least 75 above any obstacles in the line of sight) in both Sandersville and Deepstep. However, after discussions with Frank Hill and studying a map of the area, and alternative configuration was discovered. Imerys has a separate facility located about halfway between the Sandersville square and the Deepstep facility. This intermediate facility, called Plant 2, is already located on the Sandersville fiber network and would be a logical place for one end of the wireless link to be installed. With the help of the City of Sandersville electrical personnel, Mr. Sexton examined the potential of providing this link by going up in a bucket truck on both ends of the link to look at the line of sight. It turns out that the geography for the area is perfect for a wireless link. In addition, Imerys already has tower structures in place at both facilities. Plant 2 has a very tall water tower that would provide a sturdy location with a great vantage point for the placement of one antenna. The Deepstep facility has a radio tower erected to provide voice communications. This tower also has the necessary height to provide line of sight coverage back to Plant 2. The second test that was performed was to see if a wireless network could be used to provide high speed Internet access to an affluent neighborhood in Sandersville. To perform these tests, Mr. Lee took a wireless bridge and antenna up in a bucket truck at 2 different locations in the neighborhood. Mr. Sexton drove to various spots in the neighborhood and measured the signal strength and download speeds at each location. After checking a total of 6 locations, signal could only be received at 2 locations that were very near the transmitters (within a quarter of a mile). Even then, the performance was severely degraded to the point that it would not be viable for point-to-multipoint delivery. Going beyond that distance, a combination of hills and foliage prevented any signal from reaching the receivers. After reviewing the results of these tests, it was

2 determined that any wireless delivery would require extensive engineering and installation costs and efforts, which defeat the purpose of having a wireless network. The third test involved studying the feasibility of delivering wireless network access to businesses in the downtown area. To perform this test, Mr. Lee once again set up the bridge and antenna in the bucket truck, which was parked next to the police booth in the courthouse parking lot. Mr. Sexton then walked around the downtown area with a laptop equipped with a wireless PCMCIA card. The tests performed were a) monitoring the signal strength using the built-in site survey tools, and b) measuring the download speed from another laptop communicating with the same base station. This test was performed with two systems. The first was the Breezecom (now owned by Alvarion) AP-10D Frequency Hopped Spread Spectrum (FHSS) system rated at 3 megabits per second (Mbps). The second was the Cisco Aironet BR340 Direct Sequence Spread Spectrum (DSSS) system rated at 11 Mbps. Both the Breezecom transmitter and PCMCIA card use a radio that transmits at 100 mw. The Cisco BR340 bridge uses 30 mw, while the 350 PCMCIA card uses 100 mw. When the 2 systems were compared side by side, the Cisco Aironet system outperformed the Breezecom system in both throughput and coverage. As soon as line-of-sight was lost, the Breezecom system experienced a sharp decline in signal strength and download speed. Contrastingly, the Cisco Aironet System provided coverage all the way around the square and a good distance down Highway 15. Additionally, the Cisco Aironet system s download rates outperformed the Breezecom system by a factor of 3-4 (600 Kbps Breezecom vs. 2.4 Mbps Cisco, average download speed). Equipment Performance and Pricing As evidenced above, the tests performed in the downtown area showed that the Cisco Aironet equipment outperformed the Breezecom equipment in both download speed and coverage area. This would make it seem that the Cisco Aironet system would be far and away the best choice. However, there are advantages to the Breezecom system. The difference is in the frequency hopped (FHSS) vs. direct sequence (DSSS) radios. While DSSS is supposed to maximize throughput, FHSS is supposed to maximize immunity to interference. During discussions with city officials, it was mentioned that there might be a competing wireless system set up in the downtown area. This system would be a Breezecom system and begs the question of what effect the Breezecom/FHSS system and the Cisco Aironet/DSSS system would have on each other. In order to determine if interference would be a problem, a test was performed in GTRI s Network Application and Integration Lab (NAIL). In this test, three trials were run. In the first, the Cisco Aironet System was run in the absence of other wireless systems and its average download speed was measured. Next, the Breezecom system was run in the same manner. Finally, both systems were run concurrently and their average downloads speeds were measured side-by-side. The results are as follows:

3 Cisco Aironet alone: Mbps Cisco Aironet with Breezecom: Mbps Breezecom alone: Mbps Breezecom with Cisco Aironet: Mbps As expected, the Breezecom system was more resistant to interference than the Cisco Aironet system. In fact, in our trial, the Breezecom performed slightly better with the interference than without! It was only a 34 Kbps difference, which fits into the margin of error for this sort of test, but it demonstrates the FHSS system s resistance to interference. While the DSSS showed a more marked decrease in throughput, this ~7% decrease still has a performance that more than doubles the FHSS performance. So, while the interference is there, it is not enough to make the FHSS system outperform the DSSS system. Another issue that was brought up was whether or not the Cisco Aironet equipment supports VLAN implementation. The equipment used in the testing and quoted in this report does support VLANs, except where noted. Recommendations: After analyzing the results of the study, the following are the recommendations for the Sandersville wireless effort (all prices given are list, * denotes estimate [no quote available]): 1) For the wireless point-to-point link between Imerys Plant 2 and Deepstep location, a solution using the Cisco Aironet system is proposed. This is due to cost, performance, and known reliability (GTRI has similar systems implemented in other areas in the state). A representative network setup would include the following parts: Each wireless node would need: 350 Series Wireless Bridge $ dbi Solid Dish Antenna $ Series Power Injector $ 59 Lightning Arrestor $ 209 Low-Loss Antenna Cable (20 ft) $ 89 NEMA Enclosure (for bridge) $ 200* This would be the basic equipment necessary to implement a wireless point-to-

4 point connection. To connect the wireless node to its local network (i.e. Plant 2 and Deepstep), a Category 5 cable would be run up the tower to the antenna. This cable would provide both data communication and power delivery. If a wireless connection were desired between the water tower and IT office at Plant 2, two more nodes would be needed. However, a lower power antenna would be sufficient. A good antenna for this would be a 13.5 dbi Yagi antenna that lists at $369. Another item of interest that was mentioned was a hardened switch for outdoor implementation. As an example of what is available, a company called SIXNET has an 8+1 port Ethernet switch with an operating temperature range of 40 to 85 degrees Celsius (-40 to 185 degrees Fahrenheit). These list for $750. In addition, the possibility of using a higher speed, proprietary system was discussed. These systems can provide up to 54 Mbps throughput. However, the price point appears to be too high right now. As an example, the Western Multiplex Tsunami solution lists at $20,000+ per node. If this price is acceptable the option could be explored further, but it does not seem prudent at this time. 2) For the wireless distribution to the residential area just west of downtown, our tests showed a substantial problem with the geography and foliage in the area. While a wireless solution is possible, it would require a large distribution tower to distribute data to a number of smaller, strategically placed towers, which would then distribute content to the homes. Each tower would need a wireless node similar to that described above. The sheer number of towers, along with the huge planning and engineering effort that would be necessary to design and implement such a system, would create a cost so high and a timeline so long that it would defeat the purpose of using wireless delivery to the home. Therefore, it is recommended that the wireless delivery option not be pursued at this time and other delivery methods be investigated. 3) For the downtown wireless coverage, a node (or multiple nodes to provide extra coverage and throughput) such as that described in part 1) could be mounted on a tower near the downtown area and provide coverage to the entire downtown area. There are already at least 2 towers in existence that could provide the necessary coverage, although the availability of the towers is unknown. Each subscriber would simply mount a small, unobtrusive 3 dbi ($199) or 6 dbi ($399) patch antenna on the roof or side of their building facing the main tower. The choice of antennas would depend on their distance and orientation to the main distribution antenna, but most locations should be able to use the lower gain antenna. These antennas could then be connected to a 350 Series Workgroup Bridge ($659). A Workgroup Bridge is made to bridge the gap between a wired small office and a wireless LAN. The limitations are that it only supports 8 computers on its wired network, and it does not support VLAN capability. If either of these limitations were unacceptable to a subscriber, then a standard 350 Series bridge would be needed. Whichever option is chosen, the bridge/workgroup bridge would be

5 Summary plugged into the local switch or hub. This solution would still require a lightning arrestor kit, low loss cable, and power injector, but mounting the electronics inside the building would eliminate the need for a NEMA enclosure. This report gives a picture of what is needed to implement a wireless data network in the Sandersville area. The next steps would be to select vendors, select an installation company, and determine exact locations and other details for the wireless nodes. GTRI is very interested in working with Sandersville in this effort and would love to discuss the details of such an arrangement. If there is interest in pursuing this further please contact Jay Sexton. His contact information is below. Jay Sexton Research Engineer Georgia Tech Research Institute Information Technology and Telecommunications Laboratory Communications and Networking Division th Street NW Suite 243A Atlanta, GA Phone: (404) Fax: (404) jay.sexton@gtri.gatech.edu