Networking Interference

by Brian Ohlhausen

Bishop O'Connell High School

Abstract

            The purpose of this experiment is to investigate the interference common household appliances cause to Wireless-G networks. A network is a system that allows a group of computers to communicate with one another. Wireless networks use radio transmitters and receivers to send the packets of information. Certain household appliances use the same radio frequency as the wireless router and reduce the strength of the signal sent by the router to the laptop. With the results of this project, one can set up a wireless network without external interference. The hypothesis was, “If common household appliances compete with Wireless-G networking for use of the electromagnetic spectrum, then the signal strength will be reduced.”

            The materials needed are a microwave oven, cordless phone, two-way radios, cell phone, laptop with Wireless-G capability, and a Linksys Wireless-G Broadband Router. To begin, set up the laptop with an unobstructed view of the router, which is 10 meters away. Second, record the signal strength shown on the laptop with each bar of connectivity equaling 20%. Third, place the microwave oven next to the laptop. Fourth, turn on the microwave. Fifth, record the signal strength shown on the laptop. Sixth, repeat steps 1-5 replacing the microwave with the cell phone, the two-way radio, and the cordless phone. Seventh, repeat Steps 1-6 ten times.

            The hypothesis “If common household appliances compete with Wireless-G networking for the use of the electromagnetic spectrum, then the signal strength will be reduced” was proven partially correct in that even though all of the appliances ran on the electromagnetic spectrum, only appliances that ran on the same frequency reduced the signal strength. The microwave, two-way radios, and cell phone had a minimal effect on the connection strength. The cordless phone was the only appliance to have a strong negative effect on the network.

Introduction

            This project deals with wireless computer networking and the causes for interference with its signal strength. Wireless networking is a system that allows a group of computers to communicate with one another and share devices such as hard drives, printers, and modems. For a computer or another device to be a part of the network, it must be equipped with an accessory called a network adapter. A router is a device that transfers packets of information to resources within the network. (James, 2000)

            There are two kinds of networks, wired and wireless. Wired networks use Ethernet, which is a type of networking technology for local area networks and is the most reliable. These networks use cables to connect the computers directly. Wireless networks, or Wi-Fi, use radio transmitters and receivers instead of cables. (Federal Trade Commission Staff, 2006) These networks are more versatile, but are subject to interference. (James, 2000) The wireless standard being used in this experiment is 802.11g, which broadcasts at 2.4 GHz. The 2.4 GHz band is unlicensed and can be used by other appliances. (Wong, 2003) All of the appliances being tested broadcast on the electromagnetic spectrum.

            It was observed that the use of certain household appliances greatly reduce the signal strength of this wireless networking standard. The purpose of this experiment is to investigate the interference to Wireless-G networks caused by the common household appliances. If the experiment is successful, the causes of wireless networking interference should be identified. The hypothesis for the experiment is “If common household appliances compete with Wireless-G networking for use of the electromagnetic spectrum, then the signal strength will be reduced.” The hypothesis will be tested by the use of the appliances while the wireless network is in use. The signal strength will be recorded during the use of each of the appliances.

Materials and Methods

            The materials used in this experiment were a microwave oven, a cordless phone, a pair of two-way radios, a cell phone, a laptop with Wireless-G capability, and a Linksys Wireless-G Broadband Router. The Linksys Wireless-G Broadband Router broadcasts a wireless network, which the laptop attempts to receive. The reason the microwave, cordless phone, two-way radio, and cell phone were chosen is because they all use the electromagnetic spectrum while in use. (Panasonic 2.4GHz Cordless Answering System: Operating Instructions) For the first test, the strength of the wireless signal is tested without any extra interferences. (Refer to Figure 1 in Appendix) After which, the strength of the network is tested at the same time as either the microwave oven, cordless phone, two-way radio, or cell phone is in use. After the network is tested against each of these appliances individually, the data is recorded. The specific materials and procedures can be found in the experiment lab book.

Experimental Design

Electromagnetic Frequency

(Silver, 2004)

Results

Networking Interference Data Table

             When no other appliances were in use at the same time as the network, the network signal strength was at 100% for all ten trials. The microwave only interfered with the connection once with a signal decrease of only 20%. The cell phone did not interfere with the wireless connection at all. The cordless phone interfered with the network eight out of ten times with an average decrease in reception of 24%. The two-way radios interfered with the connection one time with a decrease in signal strength of 20%.

Discussion and Conclusion

            The hypothesis “If common household appliances compete with Wireless-G networking for the use of the electromagnetic spectrum, then the signal strength will be reduced” was proven partially correct in that even though all of the appliances ran on the electromagnetic spectrum, only appliances that ran on the same frequency reduced the signal strength. The microwave, which runs at about 2.45 GHz, only interfered with the connection once and it was only 20% weaker. The reason for the microwave not interfering with the connection is that the microwave contains the waves as much as possible. The cell phone, which broadcasts between 824 MHz and 894 MHz, did not interfere with the wireless connection at all. The cordless phone, which broadcasts at 2.4 GHz, interfered with the network eight out of ten times with an average decrease in reception of 24%. The two-way radios, which run at 2.4 GHz, interfered with the connection only once and only decreased it by 20%.       

            All of the appliances that broadcasted at 2.4 GHz interfered with the network at least once. The microwave only interfered once because it purposely contains the waves. The phone interfered the most because it has to broadcast the strongest to maintain a clear signal. The two-way radios interfered only once because they do not broadcast very strongly.

            In conclusion, the appliances that broadcast at 2.4 GHz are more likely to interfere with a wireless network, and the stronger the source of interference broadcasts its signal, the greater the interference will be. With the information gained, a person hoping to set up a wireless network will know where to put the network in relation to his cordless phone, microwave, and any sort of two-way radio. It is also known that a cell phone will not harm the signal strength of a wireless network. For another experiment that would further research this topic, the strength of output of the appliance along with the output frequency should be included. (McCullough, 2004) Also to continue with this project, more wireless networks could be tested, including 802.11b (2.4 GHz), 802.11a (5GHz), and 802.11n (2.4 GHz). (Stevens, 2006)

Literature Cited

James, Michael. 2000. Home Networking. Baltimore Sun 1C-3C.

McCullough, Jack. 2004. 185 Wireless Secrets: Unleash the Power of PDAs, Cell Phones, and Wireless Networks. Wiley Publishing Inc. Indianapolis, Indiana. Chapter 3.

Stevens, Alan. July 20, 2006. ‘A’ Is for Alternative. (Wireless Networking Equipment’s Standards)(Brief Article). Personal Computer World. NA.

Silver, H. Ward. 2004. Two-Way Radios and Scanners for Dummies. Wiley Publishing Inc. Indianapolis , Indiana. Pg. 27.

Wong, May. November 30, 2003. Wi-Fi Woes, Wows. Palm Beach Post. 4F.

Federal Trade Commission Staff. 2006. Municipal Provision of Wireless Internet. Washington (DC): Federal Trade Commission. Available at:http://www.ftc.gov/os/2006/10/V060021municipalprovwirelessinternet.pdf

Panasonic 2.4GHz Cordless Answering System: Operating Instructions. No Date. Panasonic Consumer Electronics Company. Secaucus, New Jersey.

Eileen T. Kraemer, University of Georgia, Athens, Georgia, Personal Communication

Walt Houser CPCUG Coordinator at .

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