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Bluetooth

2,792 bytes added, 22:44, 23 August 2017
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==Bluetooth FCC Regulation====Bluetooth Radio==For Bluetooth transmission 79 RF channels spaced 1 MHz apart are defined.  The transmitting frequencies can be calculated by: f = (2402 + k) MHz                    k= 0,...,78 (channel number) In the standard the transmitting power level is classified into three classes: 0 dBm = 1mW, 4 dBm = 2,5 mW and 20 dBm = 100 mW. The requirement for a Bluetooth receiver is an actual sensitivity level of -70 dBm or better. ===Bluetooth FCC Regulation======Bluetooth and Wifi Coexistence===For the radio transmission Bluetooth and WLAN (IEEE 802.11b) both uses the unprotected ISM-band (Industrial, Scientific, Medical) at 2.4 GHz. In the US and in most countries of Europe, a band of 83.5 MHz width is available.  In 802.11b systems the channel bandwidth is 22 MHz.  The impact of Bluetooth personal area networks on a WLAN system is a problem.  The degree to which an IEEE 802.11b terminal is susceptible to interference from nearby Bluetooth transmitters is clearly dependent upon the strength of the desired DSSS signal from the access point.* An 11 Mbps DSSS radio can provide reliable service with a narrow band interferer (such as a Bluetooth transmitter) falling within its pass band as long as the Signal-to-Interference Ratio (SIR) is greater than roughly 10 dB. *There is only about a 25% probability that an active Bluetooth transmitter will be in the DSSS passband on any given hop period. *Collision is also reduced because a Bluetooth transmitter is only active for 366 msec in each 625 msec Bluetooth hopping period.*An active Bluetooth device present can drop down of the WLAN throughput rate from about 6 Mbit/s without interferences to 3.5 Mbit/s at a typical packet size of 750 bytes. The impact of a 20dBm 802.11 Direct-Sequence WLAN system on a 0dBm Bluetooth link is pretty much minimal.  When transmitting in its 22 MHz channel, the WLAN system effectively occupies about 17MHz of the 2.45GHz ISM band (20dBm bandwidth). The total amount of power transmitted amounts to 20dBm. When the Bluetooth receiver hops in the WLAN band, it filters out the Bluetooth hop bandwidth. For the Bluetooth receiver, the WLAN signal is regarded as white noise. Assuming a 0.85MHz noise bandwidth in the Bluetooth receiver, a filter suppression of 13dB is achieved.Under normal traffic conditions in the WLAN (40 emails, 20 file transfers and 1000 Internet accesses per WLAN terminal in 8 hours, resulting in a total transfer of approximately 11 Mbyte per terminal), the Bluetooth voice user is not affected as long as his operating distance remains below 6½ feet.  At five times that distance the probability that there is a noticeable interference on the link increases to 8%.  A throughput reduction of more than 10% occurs with 24% probability at an operating distance of 32 feet.
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