1. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Bad Channels: Why They Must Be Used in the Adapted Hopping Sequence Date Submitted: October 3, 2001 Source:Anuj Batra Company:Texas Instruments, Inc. Address:12500 TI Boulevard, Dallas, TX 75243 Tel: 214 480 4220, FAX: 972 761 6966, E-mail: batra@ti.com Re: [] Abstract:Examples of when bad channels will needed in the adapted hopping sequence are provided. Purpose:Submission to Task Group 2 for comparing the two mechanisms. Notice:This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

2. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 2 Bad Channels: Why They Must Be Used in the Adapted Hopping Sequence Anuj Batra Texas Instruments batra@ti.com

3. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 3 Worldwide Regulatory Regulations United States (FCC): –FH devices must hop over a minimum of 75 channels. –NPRM suggests a new minimum value of 15 channels. Europe (ETSI): –FH devices must hop over a minimum of 20 channels. Japan: –No minimum restriction on the number of channels. –Average transmit power is a function of the number of hopping channels.

4. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 4 IEEE 802.11b Transmit Mask Current IEEE 802.11b transmit mask: 30-dB bandwidth of IEEE 802.11b signal = 22 MHz (worst case). IEEE 802.11b signal occupies 23 Bluetooth channels.

5. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 5 Three IEEE 802.11b Access Points Three collocated access points (on channels 1, 6, and 11) will be common in the enterprise environment. The three networks will occupy a total (30-dB) bandwidth of 66 MHz, which implies that these networks occupy 67 Bluetooth channels. Only 12 Bluetooth channels are free of interference. If N min = 15, then we are forced to use 3 bad channels in the adapted hopping sequence. Bad channels not used intelligently in the adapted hopping sequence can result in higher packet loss and lower throughput.

6. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 6 Lower Bound on N min (1) Should N min = 15 ever be used? Consider the following scenario: –Only 15 good Bluetooth channels are available. –Three independent Bluetooth piconets, each with a HV3 connection. –Each piconet has a single HV3 connection. Probability of collision = 1/15 = 6.7%. This packet error rate is unacceptable for a voice connection.

7. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 7 Lower Bound on N min (2) Consider the same scenario as before, except raise N min to 45. The proposed AFH mechanisms can protect all of the voice slots. In this case, the probability of collision = 1/45 = 2.2% (upper bound). This packet error rate is acceptable for a voice connection. In this example, using bad channels helps to improve the quality of the voice connection.

8. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 8 Effects of the NPRM Proposed rules in NPRM are less strict than the current rules. NPRM was issued to allow new modulation schemes, such as PBCC-22 and OFDM, into the 2.4 GHz band. An OFDM signal has a larger bandwidth than the current IEEE 802.11b signals. Because of the flexibility in the proposed rules, more new technologies will be moving into the already crowded 2.4 GHz ISM band. Therefore, spectrum free of interference will become even more difficult to find.

9. doc.: IEEE 802.15-01/443r0 Submission October 2001 Anuj Batra, Texas InstrumentsSlide 9 Conclusion When three IEEE 802.11b access points are present in an enterprise environment, it could be difficult to find 15 totally clear channels. NPRM will allow newer technologies, such as PBCC-22 and OFDM, into the 2.4 GHz ISM band. In the future, the spectrum will become even more crowded. Is N min = 15 even appropriate? To answer this question, we need to consider Bluetooth-on-Bluetooth interference.