<<<All Things Wireless>>>
Transmit or receive beamforming has been around for a long time and it works like magic. But there is a down side to it; antenna arrays require multiple RF chains which can be a power hungry and expensive solution. What if instead of aligning the copies at the transmitter or receiver we do it while the signal is under transmission in the channel; this is achieved through a Reconfigurable Intelligent Surface (RIS).
Read moreConventional battery powered systems can be impractical, expensive, or have negative environmental impacts. Energy harvesting (EH) offers a potential solution to these problems. Through ambient sources such as solar, vibrational, thermal, and RF, self-sustaining IoT devices can be designed. These devices can be easily implemented in wearables, medical implants, and infrastructure. Companies such as TI and ADI have developed power management systems for EH and consumer products already exist. These products continue to increase in efficiency and practicality every year.
Read moreIt is widely believed that performance of non-coherent receivers is much worse than performance of coherent receivers in terms of Bit Error Rate (BER). Although this is true to some extent but as we show in this post the difference in performance is not that much in case of Minimum Shift Keying (MSK). In fact, there is only a difference of about one dB in an AWGN environment at high Signal to Noise Ratios (SNR). The difference is somewhat larger in flat fading environment but given the simplicity of implementation of a non-coherent receiver the trade-off might be worth it.
Read moreSome Background Before we delve deep into Minimum Shift Keying (MSK) and its performance in presence of co-channel interference the reader is advised to look at the following posts. Post 1 – MSK BER performance in AWGN and flat fading environment when viewed as extension of BPSK Post 2 – MSK Power Spectral Density and its BER performance in AWGN when viewed as a CPM Post 3 – MSK BER Performance in AWGN and flat fading environment when viewed as a CPM Co-channel interference is a phenomenon widely encountered in wireless communication systems and the main reason for that is […]
Read moreI – In the previous two posts we discussed MSK performance in an AWGN channel, first presenting the MATLAB/OCTAVE Code for one sample per symbol case [Post 1], and then extending it to the more general case of multiple samples per symbol [Post 2]. This helps us visualize the underlying beauty of Continuous Phase Modulation (CPM) which reduces out of band energy and consequently lowers Adjacent Channel Interference (ACI). We also briefly touched upon the case of MSK in Rayleigh fading, but did not go into the details. So here we take a deeper dive.
Read moreSome Background on MSK I – In the previous post we presented the mathematical model and code for BER calculation of a popular modulation scheme called MSK. However in the code we shared, we only considered one sample per symbol, which makes MSK look like BPSK. While BPSK symbols fall on the real axis, MSK symbols alternate between real and imaginary axes, progressing by π/2 phase during each symbol period. MSK signal thus has memory and this can help in demodulation using advanced techniques such as Viterbi Algorithm.
Read moreMinimum Shift Keying (MSK) is a type of Continuous Phase Modulation (CPM) that has been used in many wireless communication systems. To be more precise it is Continuous Phase Frequency Shift Keying (CPFSK) with two frequencies f1 and f2.
Read morePulse Amplitude Modulation (PAM) is a one dimensional or in other words real modulation. Simply put it is an extension of BPSK with M amplitude levels instead of two. This can be a bit confusing because BPSK can be looked at as a phase modulation and its natural extension must be QPSK or 8-PSK modulations. To remove this ambiguity lets call M-PAM an extension of simple amplitude modulation but with M levels. In the discussion below we consider M=4 but then extend it to the general case of M=2k (k=1,2,3…).
Read moreMassive MIMO is no longer a theoretical concept and it is already being adopted in the industry. So we now need to look beyond Massive MIMO or MaMIMO as it is popularly referred to.
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