Residential Microwave Oven Interference on Bluetooth Data Performance

856 IEEE Transactions on Consumer Electronics, Vol. 50, No. 3, AUGUST 2004 Residential Microwave Oven Interference on Bluetooth Data Performance Thomas W. Rondeau, Student Member, IEEE, Mark F. D Souza, Student Member, IEEE, and Dennis G. Sweeney, Member, IEEE Abstract With both Bluetooth and microwave ovens operating in the same frequency band, fears have arisen about the effects of microwave oven interference on Bluetooth networks. While Bluetooth devices use frequency hopping spread spectrum (FHSS), the high power output of microwave ovens may still pose a threat to Bluetooth networks. We therefore endeavored to characterize microwave oven behavior and understand its effect upon Bluetooth networks. Our experimental results show that Bluetooth devices will tolerate a high level of interference. With two Bluetooth devices forming a piconet placed within 1 m of an oven, the Bluetooth throughput was significantly greater than half of the maximum throughput rate. Moving to a distance around 10 m from the oven showed very little degradation to the throughput due to interference. The effects of microwave oven interference, while noticeable, are by no means fatal. The results also showed no gain from the forward error correction (FEC) used on some Bluetooth packets. Index Terms Bluetooth, interference, ISM band, microwave oven. I. INTRODUCTION Bluetooth is an emerging standard for short-range, low-cost, and low power wireless connectivity for consumer devices and Personal Area Networks (PAN). It is a frequency hop spread spectrum (FHSS) system intended for worldwide operation in the unlicensed 2.45 GHz Industrial Scientific Medical (ISM) band. Bluetooth is more than just a radio: it is an entire networking standard. A number of microwave devices operate in the ISM band. Bluetooth, 802.11, and Zigbee are examples of Manuscript received October 22, 2003. This work was supported by The Virginia Center for Innovative Technology, who supported both the laboratory equipment and Mark D Souza. Thomas Rondeau was supported by the Bradley Scholarship of Virginia Tech. Thomas W. Rondeau is with the Center for Wireless Telecommunications at Virginia Tech, Blacksburg, VA 24061-0111 USA (phone: 540-231-2569; fax: 540-231-3004; e-mail: trondeau@vt.edu). Mark D'Souza works for Northrop Grumman Corporation, Electronics Systems Sector, P.O. Box 1897, MS 1155, Baltimore, MD 21203 USA (phone: 410-765-3314; fax: 410-765-7982; e-mail: mark.dsouza@ngc.com). Dennis G. Sweeney is with the Bradley Department of Electrical Engineering and the Center for Wireless Telecommunications, Virginia Tech, Blacksburg, VA 24061-0111 USA (e-mail: dsweeney@vt.edu). communications devices that operate in the ISM band, but the primary occupants of this spectrum are non communications devices such as microwave ovens and RF-excited lighting. The power leakage from these devices is limited by concerns about user safety rather limiting interference to unlicensed devices. The relatively large leakage power of microwave ovens is a potent source of interference to unlicensed Federal Communications Commission (FCC) Part 15 [1] communications devices. Because of the disproportionately large power output of microwave ovens compared to the low power Bluetooth devices, there is a concern about how well Bluetooth devices will perform in the presence of microwave ovens. Researchers have suggested that microwave oven interference can greatly reduce the data throughput of a Bluetooth network, which will severely impair its operation and usability [2] [3]. [2] and [4] have suggested methods to mitigate the effects of microwave oven interference on Bluetooth communications, but none have performed physical studies to observe the actual effects of microwave oven interference on Bluetooth networks. We therefore set out to determine how microwave ovens interfere with Bluetooth systems and to determine the severity of microwave oven interference on Bluetooth data throughput. This project combines physical analysis of Bluetooth networks with microwave oven interference and throughput measurements as a metric of performance. Section 2 of this paper describes the power and frequency characteristics of Bluetooth devices and microwave ovens. Section 3 discusses the experimental setup and measurements and the tools used to conduct the experiments. Section 4 discusses the results from the experiments, and Section 5 concludes the study with our observations on Bluetooth operations in the presence of microwave ovens. II. BLUETOOTH AND MICROWAVE OVEN OPERATIONS A. Bluetooth Operation Bluetooth is a well-defined open standard maintained by the Bluetooth Special Interest Group (SIG). The devices used in this study all conform to the Bluetooth 1.1 specifications [5]. Contributed Paper Original manuscript received February 26, 2004 Revised manuscript received May 25, 2004 0098 3063/04/$20.00 2004 IEEE

T. W. Rondeau et al.: Residential Microwave Oven Interference on Bluetooth Data Performance 857 Bluetooth operates in the ISM band with data being transmitted in the range of 2.402 GHz to 2.480 GHz. Bluetooth is a FHSS device where each packet is transmitted or received on a different channel. Bluetooth operates under FCC Part 15 rules, which stipulate that it must not give interference, and it must take any inference it receives [1]. The FHSS reduces Bluetooth s ability to produce interference to other ISM band devices by spreading the power throughout the spectrum. The FHSS has the added benefit of being able to reduce the effects of interference sources: if another device is using a portion of the ISM band, the Bluetooth device will retransmit on another channel unacknowledged packets lost to interference on a particular channel. The FHSS is pseudorandom, and as of the 1.1 specs, there is no intelligence in the FHSS to avoid hopping onto certain channels. Even with the pseudorandom FHSS sequence, interference from devices such as microwave ovens may still produce significant packet errors and reduce throughput. The most important aspects of a Bluetooth device for an interference study are its frequency and power output. The FHSS employed by Bluetooth uses 79 channels 1 MHz wide with a hopping rate of 1600 channels per second. Bluetooth communication is also time division duplex (TDD) where, between two entities on the same Bluetooth piconet (a network of two or more Bluetooth devices), one device transmits in a period followed by another device s transmission. With more than two members of a piconet, the master controls the transmission sequence by polling each slave sequentially to indicate when it may transmit. Bluetooth devices have output power levels up to 20 dbm, but all the devices used in this study were limited to 12 dbm due to the default settings in the radios. B. Microwave Oven Operation Microwave ovens are a dominant operator in the ISM band. They use magnetron tubes to generate microwave energy, which in turn heats the food. Ideally, the magnetrons generate a continuous wave centered at 2.45 GHz, exactly in the middle of the ISM band. In practice, the output spectrum of a microwave oven varies in frequency (frequency wander) and can show side-bands (or multiple interfering tones) at other frequencies in the ISM band. At full-power operation, a microwave oven usually has an output spectrum about 2 MHz wide, but in the start-up and shutdown cycles, the spectrum can be as wide as 20 MHz [6]. Residential microwave ovens generate power output from 400 800 watts and they operate from half-wave rectified AC power. The actual duty cycle is about 45% [3]. The output power cycle is tied to the 60 Hz AC input cycle, so the oven is on for about 8.8 ms and off for about 8.8 ms. The effective isotropic radiated power (EIRP) of microwave ovens can range from 16 dbm to 33 dbm [6]. Much of our information about microwave oven operation came from the NTIA reports that measured spectrum and leakage power from several microwave ovens [7] [8]. We repeated many of their experiments to verify that the ovens we used operated like standard ovens used in the NTIA reports, which they did. In accordance with the NTIA s results, we wanted to maintain as constant a power output as possible from the ovens during all the experiments run. As such, we always placed the oven door facing the Bluetooth piconet, and they were always on the same horizontal plane so that vertical variations in the output power were not a concern. In order to maintain a constant temperature of the oven load to minimize any fluctuations resulting from different loads, we used a 1 L cup of water and operated the oven for 3 minutes before any tests were performed and then 30 seconds prior to any individual test. III. MEASUREMENTS A. Spectrum Capture We used a computer-controlled spectrum analyzer to capture the oven spectrum over a period of time. We approximated a real-time spectrum analyzer by programming a computer interface to capture data from the spectrum analyzer at a rate of approximately 2 sweeps per second. Each sweep captured the signal power levels over the entire 79 MHz spectrum occupied by Bluetooth transmissions. The system was incapable of operating any faster than the 2 sweeps per second due to data transfer limitations. The major relevance of this technique to capture the spectrum over a period of time is to improve upon the standard peak-hold measurements used to classify microwave oven outputs. Unlike the spectrum plots shown in Figs. 1 and 2, a peak-hold plot gives no indication of power fluctuations or frequency wander that occurs during the oven s operation. Fig. 1 gives a clear indication that the output power levels are not constant, and Fig. 2 shows that while this oven is fairly narrowband, the power densities do move around the center frequency of 2.53 GHz. The spectrum analyzer used to capture the Power Spectral Density (PSD) data swept the 79 MHz ISM band for 33 ms twice a second. During the 33 ms sweep, the oven completed 2 full periods of operation to produce the resulting spectrum of Figs. 1 and 2. The sweep was triggered from the AC line to ensure that the sweep would coincide with the oven output. The received power recorded in Figs. 1 and 2 peaked around 25 dbm at about 2.455 GHz, which is about 30 db higher than the upper limit of the received power range of Bluetooth, and even the most significant sideband (at approximately 2.433 GHz) peaked around 61 dbm, which is in the range of the Bluetooth s minimum received power.

858 While looking at the microwave oven output power characteristics, we used a number of different ovens, each of which had widely varying spectrums. The microwave oven used for the interference tests was chosen because of its high power output; it should represent a worst-case situation for residential microwave oven interference. However, the exact effects of any given microwave oven on a Bluetooth network will inevitably vary from the data collected in our experiments. Our data should provide an upper bound on the interference problems a Bluetooth network will have in the presence of any microwave oven. Fig. 1. PSD of microwave oven IEEE Transactions on Consumer Electronics, Vol. 50, No. 3, AUGUST 2004 stack, an application called Bluetooth Test Program was created that allows any computer to interface with any Bluetooth device over a serial or USB line. From the interface, any command available through the HCI stack can be issued such as reading or writing hardware registers, performing inquiries, creating and destroying connections, and transmitting data. For our experiments, we were interested in the maximum data throughput. A packet must fill every time slot in order to achieve maximum throughput and for us to accurately observe the entire hopping sequence and the effect of the microwave oven on each timeslot. The Bluetooth Test Program was programmed in order to ensure that the Bluetooth device transmitted a data stream with a full payload during every timeslot. The program ensured that, under optimal conditions of no interference or packet errors, maximum data throughput was always achieved. By the careful tuning of the program, we guaranteed that any reduction in throughput was caused by bit errors and interference. C. Data Collection Techniques To analyze the interference effects on the Bluetooth network, we wanted to know the contents of every data packet on the link. By knowing the data packets, we can calculate the data throughput of the link and observe lost data packets or any errors in the data packets. Errors could occur either from the interference source or through routine errors introduced by the radio channel, and a lost packet is a packet with so many bit errors that it can no longer be recognized as a Bluetooth packet. Because the Bluetooth Test Program ensured all time slots were filled with a data packet, any empty time slot observed at the receiver corresponded to a lost packet. Fig. 2. Top view of PSD of microwave oven B. Bluetooth Devices and Control Software The Bluetooth devices used in all experiments are Bluetooth 1.1 compliant and class 1 devices. The configuration of the Bluetooth devices was set to limit the maximum transmit power to 12 dbm even though they were capable of a maximum power of 20 dbm. The devices were controlled via a USB bus by two separate computers running Center for Wireless Telecommunications (CWT) Bluetooth Protocol Stack. The protocol stack was written at the CWT and handles all layers above and including the Host Controller Interface (HCI). To utilize the protocol We used a Bluetooth protocol analyzer to capture all data packets. The protocol analyzer captures all packets including the frequency of the transmission, time slot of the transmission based on the master s clock, packet payload, and whether the packet had a recoverable error (errors correctable by the FEC information) or a non-recoverable error (the FEC could not correct the errors or no FEC was present). A histogram is used to analyze the interference. It shows the number of packets of each type on all 79 channels as captured by the protocol analyzer. The histogram gives a visual representation of the Bluetooth network transmissions. For all tests, the master transmitted a single type of data packet (DM1, DH1, DM3, or DH3) and, according to the acknowledgement system in the Bluetooth protocol, the slave acknowledged with a NULL packet. The histogram displays recoverable error packets, non-recoverable error packets, and lost packets. Fig. 3 shows the configuration of a bar in the histograms, segmented by the type of packet. A channel with a highpowered interferer will have fewer usable data packets and more lost and erroneous packets.

T. W. Rondeau et al.: Residential Microwave Oven Interference on Bluetooth Data Performance 859 Fig. 3. Histogram bar setup D. Experimental Setup During all the experiments, the slave unit was connected to the spectrum analyzer through a power splitter fed by a printed dipole antenna with 0 db gain, and the protocol analyzer sat as close to the antenna as physically possible as shown in Fig. 4. Unfortunately, there was no access to the antenna port of the protocol analyzer, and so there was no way to connect the protocol analyzer to the slave antenna. The spectrum analyzer, protocol analyzer, and slave Bluetooth device were all controlled by a laptop while a separate computer controlled the master Bluetooth device. Each of the test setups used for the experiment can be found in Fig. 5.The setups include the slave configuration of Fig. 4 as well as the master Bluetooth device, the controlling computer, and the distances separating the two Bluetooth devices from each other and the oven along with any obstacles in the environment. Fig. 4. Slave Unit Test Setup The first test we performed was to generate a CW signal in the ISM band with enough power to interfere with Bluetooth transmissions. This test was used as a check to verify the Bluetooth devices reaction to an interferer. Fig. 5a was used as the experimental setup for the CW interference test. The CW signal generator replaced the oven as the interference source. Fig. 6a shows the histogram generated by the protocol analyzer information for a noninterfering case and Fig. 6b shows the histogram for the network with a 5 dbm CW tone at 2.440 GHz. As expected, there were few errors in the non-interfering environment and all errors were uniformly distributed across the channels. Given 50000 packets over 79 channels, there should be about 632 packets per channel, as Fig. 6a confirms. In the CW interference environment, all packets transmitted on frequency 2.440 GHz were lost due to the extremely high interfering tone. Furthermore, the adjacent channels showed lost packets due to adjacent channel interference. All the packets lost on frequencies 2.439, 2.440, and 2.441 GHz would then have to be retransmitted, which causes the increase in the number of packets on the other channels. Fig. 5. Experimental Test Setups After the CW tests confirmed the operation of our test setup, we ran tests using the microwave oven as the interference source in a number of different setups. We used three basic environments for tests with different setups in each environment. The first environment is a modular building, where the CWT Bluetooth Lab is located, the second environment is an office setting, and the third environment is an outdoor line-of-sight path, each of which is shown in Fig. 5.

860 IEEE Transactions on Consumer Electronics, Vol. 50, No. 3, AUGUST 2004 The PSD plot of Fig. 7 shows the oven output at the time of the test, which exhibits widely varying signal powers over the capture period. The operating frequencies of the microwave oven correspond to the frequencies where the most number of lost packets occurred. The histograms of Fig. 8 show a wide range of channels being affected by the oven. The most notable areas are the frequencies around 2.453 GHz and the wide range of effected channels from roughly 2.430 to 2.450 GHz. Moving in frequency away from the oven s center frequencies of operation shows a decrease in the number of lost packets, although significant error packets still occur. Fig. 7. PSD of the oven in experimental setup of Figure 5a Fig. 6. (a) DM1 packet transmissions with no interference (b) DM1 packet transmissions with 5 dbm CW interference Each test consisted of a 30 second transmission where a total of 24000 packets were transmitted by both the master (data packets) and the slave (NULL packets). All setups were run for both DM1 packets, which contain 2/3 rate FEC, and DH1 packets which contain no FEC. The different packet types provide insight into the value of the FEC. All tests followed the same procedure. To start each test, the oven was warmed up for 30 seconds, and then the computer controlled spectrum analyzer captured the oven spectrum for 30 seconds. After the spectrum capture was completed, the Bluetooth devices were connected and the protocol analyzer began to capture all the traffic. Upon connection, data transmission began and the master transmitted 24000 data packets to the slave. To illustrate the results, the experimental setup of Fig. 5a will be used as an example. Following our experimental procedure, the spectrum of the oven was captured for 30 seconds and can be seen in Fig. 7. DM1 packets were then transmitted and captured by the protocol analyzer, and then the test was repeated with DH1 Packets. The histograms for the DM1 and DH1 packets are shown in Fig. 8a and 8b. Fig. 8. Packet histogram for modular building tests with (a) DM1 packets and (b) DH1 packets for Fig. 5a

T. W. Rondeau et al.: Residential Microwave Oven Interference on Bluetooth Data Performance 861 The large number of channels affected by the oven output is due to both the bandwidth of the output spectrum of the oven as well as the adjacent channel interference. The CW tests show that adjacent channels are susceptible to high-power transmitters, and the histograms of Fig. 8 reiterate the issue of adjacent channel interference and how high power interferers pose a larger threat than to just a single channel. While we have seen the correlation between the microwave output and the Bluetooth piconet packet performance, we used a qualitative metric to provide a measure of the damage caused by microwave ovens. The metric used was the effective data rate of the piconet during the test period. The data rate can be calculated using the information from the protocol analyzer data in the following formula: ( Num Packets) ( Bytes / Packet) ( Bits / Byte) R = ( End Time) ( Start Time) In a perfect channel with no interference, if 24000 DM1 packets were sent across during each timeslot followed by a NULL packet acknowledgment, then the amount of time to transmit all the packets is (24000 (DM1) + 24000 (NULL) ) * 625 µs/packet = 30 s. The data rate is then: (24000 packets) (17bytes/ packet) (8 bits/ byte) R = (30 seconds) R = 108. 8 kbps experimental scenarios for both DM1 and DH1 packet transmissions. The letter marking each scenario in Table I directly matches the setups in Fig. 5. With no oven interference, the piconet approached the maximum transmission speed. The worst scenarios were the outside measurements where the radio link was pushed to extreme limits while the microwave oven sat just 1 m away from the slave. The results show that at this distance a majority of packets were lost due to the interference. The general trend was that the closer the Bluetooth slave was to the oven, the worse the performance became due to the higher interference power of the oven output, but moving the master closer to the slave improved the throughput. By placing a drywall partition between the piconet and the microwave oven as in Fig. 5d, data rates are comparable to the line-of-sight data rates at an increased distance of 4 or 5 m between the piconet members and the microwave oven. The attenuation caused by the drywall on the interference power of the microwave oven resulted in an improvement of the data rate. The corresponding packet histogram is shown in Fig. 9. These results indicate that if a microwave oven was causing interference to a piconet, just a small increase in distance or a small amount of attenuation due to some object between the piconet and the oven will improve the traffic data rate within the piconet. This is the maximum data rate possible for a DM1 packet. Each DM1 packet contains a maximum of 17 bytes per packet, and a DH1 packet contains a maximum of 27 bytes per packet, which gives the DH1 packets a maximum data rate of 172.8 kbps. The data collected by the protocol analyzer over a comparable frame of time can be used to calculate the data rates of the interference setups. To calculate the data rates, 24000 data packet samples were taken from the piconet, and the total number of packets sent by the master minus the packets with non-recoverable errors and the lost packets yields the total number of usable data packets received. The transmission time was taken directly from the protocol analyzer data. The channel with no interference produced 108.4 kbps for DM1 packets and 166.3 kbps for DH1 packets. Turning on the microwave oven in Fig. 7a dropped the data rates to 75.3 kbps for DM1 packets and 99.9 kbps for DH1 packets. IV. RESULTS Several different experimental setups were used to develop trends in the microwave oven interference environment. Table I summarizes the data rates calculated for the different Fig. 9. Packet histogram for office tests with drywall separation with DH1 packets for Fig. 5d The extreme case is the 72 m link of Fig. 5e, and the corresponding packet histogram is shown in Fig. 10. Fig. 10 shows that the microwave oven interference power is spread throughout the entire band and significantly decreased the number of good data packets that were transmitted during the test period of 30 seconds. Conversely, the histogram of Fig. 9 shows few lost packets and a definite improvement in the number of data packets transmitted. The other histogram scenarios and the subsequent effect of the microwave oven interference on the piconet can be extrapolated from Figs. 8, 9, and 10.

862 IEEE Transactions on Consumer Electronics, Vol. 50, No. 3, AUGUST 2004 TABLE I: BLUETOOTH DATA RATES IN INTERFERENCE ENVIRONMENT Fig. 10. Packet histogram for outdoor tests at 72 m master/slave separation with DH1 packets for Fig. 5e While the trends in the results are fairly obvious, the severity of the interference is not. The data shows that at reasonable piconet distances, the total data throughput still exceeded 50% of the maximum possible throughput. This result is significant because Bluetooth was designed for short range and mobile communications, and so large separations, especially like the setups we had in the outdoor experiments, are unlikely. During normal operation and location of the Bluetooth devices and the microwave oven, the effects of interference will be slight. The CW interference test results shown in Fig. 4b clearly illustrate the problem of adjacent channel interference, and the results of Fig. 10 show how much more of a problem adjacent channel interference can be with a wider and noisier source of interference. The issue of frequency wander, which will spread the signal bandwidth out over time, amplifies the adjacent channel interference problem because the interferer affects more channels. The issue of adjacent channel interference must therefore be a much greater consideration when discussing Bluetooth interference than past simulations and researchers have previously suggested [9]. Another aspect addressed by our experiments is the lack of benefit of FEC coding on the packets. The higher throughput of the DH1 to the DM1 packets in the same setup suggests that the FEC encoding does not improve throughput. The 2/3 FEC coding used on DMx packets is a (15,10) shortened Hamming code, which is a weak channel code [10]. The small coding gain obtained is offset by the additional overhead, and so the packet throughput decreases significantly, even in the presence of interference. Only for the worst-case scenario of the 72 m outside test did the DM1 packets provide a better data rate then the DH1 packets. In all indoor cases, the DH1 packets provided better data rates for any interference setup than the DM1 packets with no interference. V. CONCLUSIONS The distance between the piconet members and the distance to the microwave determines the extent to which the microwave ovens affect Bluetooth networks. The weaker the Bluetooth signal and the closer the oven was, the greater the effect of the interference. This result is no surprise; however, the Bluetooth devices maintained connection and usable throughput even in the extreme situation where the oven was very close. If a more reasonable distance of 10 m is maintained between the oven and any member of a Bluetooth piconet, the effects of interference will be minimal, and if closer, the interference does not significantly degrade the performance until within about 5 m of the oven. Placing obstructions in the path between the piconet and oven such as a drywall can also improve performance at closer distances. This study also found the lack of throughput improvement due to the FEC coding used on some data packets. The overhead required for the FEC is not worth the small coding gains in almost any situation. This study only investigated 1-slot packets. For a more complete analysis, similar experiments must be done for 3-slot and 5-slot packets to see if the general trends still hold. We suspect DHx packets will continue the trend and provide greater throughput over DMx packets. The FHSS should provide the same channel distribution for multi-slot packets, and so the oven s interference will affect the same number of packets for any packet payload size. However, there is reduced overhead in the multi-slot packets, so for each packet that is successfully transmitted, much more data has been transmitted (over 3 times the amount of data for 3-slot packets and over 5 times the amount of data for 5-slot packets). The work in [11] studied the throughput of different packet sizes for multiple Bluetooth networks operating in the same environment and found DH5 packets to produce the maximum total throughput in the presence of interference. A similar study should be performed to determine if the results of [10] change if a microwave oven is used as the interference source instead of other Bluetooth networks. Farther analysis could also be done regarding the Bluetooth audio channels, which do not require acknowledgments and have different FEC and CRC requirements. With the new version 1.2 of the Bluetooth specifications, the introduction of adaptive FHSS (AFHSS) will lead to new

T. W. Rondeau et al.: Residential Microwave Oven Interference on Bluetooth Data Performance 863 questions about how Bluetooth will hold up in the presence of interference. With the understanding of how Bluetooth systems currently handle microwave interference, a study should be conducted with version 1.2 Bluetooth devices to understand how much benefit the AFHSS provides. REFERENCES [1] Title 47 of the Code of Federal Regulations: Part 15 Radio Frequency Devices, 2001. [2] P.S. Neelakanta and J. Sivaraks, A Novel Method to Mitigate Microwave Oven Dictaded EMI on Bluetooth Communications, Microwave Journal, July 2001, pp. 70 88. [3] C.R. Buffler and P.O. Risman, Compatibility Issues between Bluetooth and High Power Systems in the ISM Band, Microwave Journal, July 2000, pp. 126 131. [4] Horne Jonathan, Vasudevan Subramanian, and Mahesh Varanasi, Reliable Wireless Telephony using the 2.4 GHz ISM Band: Issues and Solutions, Proceedings of the 4 th IEEE International Symposium on Spread Spectrum Technologies and Applications, vol. 2, 1996, pp. 789 793. [5] (2001, Feb. 22) Specification of the Bluetooth System: Version 1.1, Available: www.bluetooth.com. [6] P.E.Gawthrop, F.H. Sanders, K.B. Nebba, and J.J. Sell, Radio spectrum measurements of individual microwave ovens, NTIA Report 94-303-2. [7] A. Kamerman, Microwave Oven Interference on Wireless LANs Operating in the 2.4 GHz ISM Band, 8 th IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications, vol. 3, 1997 pp.1221 1227. [8] P.E. Gawthrop, F.H. Sanders, K.B. Nebba, and J.J. Sell, Radio spectrum measurements of individual microwave ovens, NTIA Report 94-303-1. [9] A. El-Hoiydi, Interference Between Bluetooth Networks-Upper Bound on the Packet Error Rate", IEEE Communications Letters, vol. 5, June 2001, pp. 245 247. [10] J.G. Proakis, Block and Convolutional Channel Codes, in Digital Communications, 4th ed., New York: McGraw-Hill, 2001, pp. 416 547. [11] S. Zurbes, W. Stahl, K. Matheus, and J. Haartsen, Radio Network Performance of Bluetooth, IEEE International Conference on Communications, vol. 3, 2000, pp 18 22. Thomas W. Rondeau (S 02) was born in Pittsfield, MA in 1981. He graduated Suma Cum Laude and received his B.S degree in electrical engineering with a minor in English literature from Virginia Tech in 2003 and is currently working towards his M.S. degree in electrical engineering, also at Virginia Tech. He is currently on the National Science Foundation s (NSF) Disaster Communications project with the Center for Wireless Telecommunications (CWT), focusing his research in rapidly deployable radios through the use of cognitive wireless technology. While an undergraduate at Virginia Tech, he helped establish and run the Bluetooth Lab of the CWT. His current research interests include cognitive radios, rapid deployment of radios for emergency response, software radios, genetic algorithms, and local and personal area wireless networks. Mr. Rondeau was awarded the IEEE MTT-S Undergraduate/Pre-Graduate Scholarship in 2003. Mark F. D'Souza (S'01) was born in Mumbai, India in 1978. He received his BS and MS degrees in electrical engineering from VA Tech, Blacksburg, VA in 2000 and 2002 respectively. While at VA Tech, he researched the application of Bluetooth Radio as an emerging wireless technology for the Center for Wireless Telecommunications and jointly with Luna Innovations, Inc., Blacksburg VA. In addition, he has worked as an Intern at the Orbital Sciences Corporation on aerospace applications and on analog low-power mixed signal IC design at Analog Devices, Inc. He currently works for Northrop Grumman Corporation's Electronic Systems Sector (ESSS) in the Systems Development and Technology Group. At NGC, he works on Anti-Tamper Effectiveness/Reverse Engineering projects for Advanced Airborne Radar applications. Dennis G. Sweeney (M 96) received his BS in Electrical Engineering from VA Tech, Blacksburg, VA, a M.A. Degree from Catholic University of America, Washington, DC, and the M.S. and PhD degrees in Electrical Engineering at VA Tech in 1971, 1976, 1986, and 1992 respectively. He is currently Assistant Research Professor with the Center for Wireless Telecommunications at VA Tech. His current interests include unlicensed wireless applications including Bluetooth, wireless system propagation issues, and radio frequency circuit design. He is currently involved in propagation measurement for Ultra Wideband (UWB) systems. He worked with the VA Tech Satellite Communications Group and he also worked at the Jet Propulsion Laboratory with GPS applications. Dr. Sweeney has served as an Associate Editor for the IEEE Transactions on Vehicular Technology.