Bluetooth Low Energy Controller Low IF GFSK Modem

This paper presents the implementation of Bluetooth Low Energy Controller (BTLE), Low Intermediate Frequency (IF), Gaussian Frequency Shift Keying (GFSK) Modulation and Demodulation technique. The GFSK modulation uses a bandwidth bit period product BT=0.5. The modulation index shall be configurable between 0.45 and 0.55. A binary one shall be represented by a positive frequency deviation, and a binary zero shall be represented by a negative frequency deviation. The GFSK modulation uses quadrature or IQ based modulation and the two algorithm for GFSK demodulation presented in the paper seems better for low power design of BTLE. The choice of demodulation algorithm is by comparing the Bit Error Rate (BER) performance curve over Signal To Noise Ratio (SNR). The Receiver with the lower curve having better performance. A MATLAB simulation model was build for comparing BER performance of the two algorithms. The ultimate goal is obviously a BER of 0 but since this is difficult to achieve in a real receiver with realistic noise levels, the BTLE standard defines a target BER of 1e^-3 (0.1%) at about 15dB SNR. This means that one bit in 1000 is wrongly received. Now, the simplest way to compare two receivers is to compare at which SNR this target BER is achieved. The lower the SNR the better the receiver. A more sophisticated way of comparing the SNR performance of two receivers is to compare the entire BER curves. The receiver with the "lower" curve wins.