Problems and simulations: Spread Spectrum, MIMO, OFDM, OFDMA \& ECG signals. 1. Assume we wish to transmit a 56kbps data stream using spread spectrum. a. Find the channel bandwidth required to achieve a 56-kbps channel capacity when SNR=0.1, 0.01 , and 0.001. b. In an ordinary (not spread spectrum) system, a reasonable goal for bandwidth efficiency might be 1bps/Hz. That is, to transmit a data stream of 56kbps, a bandwidth of 56kHz is used. In this case, what is the minimum SNR that can be endured for transmission without appreciable errors? Compare to the spread spectrum case. Hint: Review Channel capacity material [1]. 2. Investigate and contrast the main differences between MIMO, OFDM, and OFDMA. Draw and explain the architecture of a MIMO-OFDM system. Provide some application examples of MIMO-OFDM and MIMO-OFDMA. 3. For an 36Mbps data stream with a symbol time of 133.34s, how many subcarriers are created? 4. a) The sequence 1011011000101100 is the input to a 44 block interleaver. What is the output? Provide an example of burst errors using the same bit sequence. What is the output of the deinterleaved sequence at the receiver? b) Investigate and provide an example of Hamming codes. Simulation of a communication system with ECG signal transmission and QRS detection. 5. The electrocardiogram (ECG) is a recording of body surface potentials generated by the electrical activity of the heart. Clinicians can evaluate an individual's cardiac condition and overall health from the ECG recording and perform further diagnosis [2]. The ECG signals can be obtained from three sources: 1) Biomedical databases (e.g., MIT-BIH Arrhythmia Database) or other pre-recorded ECG data; 2) ECG simulator; 3) Real-time ECG data acquisition. In this experiment, ECGSYN may be used to generate synthetic ECG signals in MATLAB [3,5]. This ECG signal will be wireless transmitted by using the QPSK modulation technique. To simulate the QPSK transceiver use the communications system objects/code in MATLAB described in [4,6]. This simulation can also be done in Simulink, please refer to [4]. Explain also the process on how to detect the QRS complex of ECG signal using the Simulink model reported in [2]