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Bluetooth® Frequency Hopping

This model shows a simple Bluetooth® wireless data link. Bluetooth is a short-range radio link technology that operates in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. The example modulates signals using Gaussian frequency shift keying (GFSK) over a radio channel with maximum capacity of 1 Mbps.

The example uses frequency hopping over a 79 MHz frequency range to avoid interference with other devices transmitting in the band. In this scheme, the sender divides the transmission time into 625-microsecond slots, and uses a new hop frequency for each slot. Although the data rate is only 1 Mbps, a much larger bandwidth of 79 MHz is required to simulate the frequency hopping effects.

Structure of the Example

The example contains a master transmitter, a slave receiver, and an AWGN channel in between.

  • A Binary Cyclic Encoder block is used for the error correction encoder.

  • The frequency hopping GFSK modulation is constructed with a CPM Modulator block and an MFSK Modulator block.

  • An MFSK Demodulator block is used to construct the frequency hopping demodulator.

  • Receive Delay calculation: The 'Assemble Packets of 625 bits at 1Mbps' buffer causes a delay of 625 samples. The 'Disassemble packet' subsystem contains a buffer with the output size of 15 which cases a delay of 15. Further, the signals have to be aligned before they are passed through the decoder as each 10 bit message corresponds to a particular 15 bit sequence. For this a 5 sample delay is used in 'Disassemble packet'. Thus the total delay is 625 + 15 + 5 = 645. As the processing is done to the samples that have been cyclic encoded with a rate of 3/2, the effective sample delay in the system is 645*2/3 = 430.

The received signal spectrum is shown by the Spectrum Analyzer

Results and Displays

To examine the performance of this example, double-click the icons to open the error rate display and scopes.

References

The Bluetooth standards can be found at: http://www.bluetooth.com/

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