<<<All Things Wireless>>>
Discussion of important elements of upcoming fifth generation wireless technology (5G) including Massive MIMO, Millimeter Wave and M2M.
60GHz Millimeter Wave Band is a band spread between 57GHz and 64GHz. This unlicensed band was first released in the US in 2001 but with limited allowance for transmit power (EIRP of 40dBm). Later on, in 2013, this limit was increased (EIRP of 82dBm) to allow for greater transmit power and larger range.
Read moreWe calculate the degradation in Bit Error Rate (BER) performance due to antenna correlation at the Mobile Station and the Base Station. Exponential Correlation Model is used in the simulation.
Read moreThe mmWave Channel It is well known that wireless signals at millimeter wave frequencies (mmWave) suffer from high path loss, which limits their range. In particular there are higher diffraction and penetration losses which makes reflected and scattered signals to be all the more important. Typical penetration losses for building materials vary from a few dBs to more than 40 dBs [1]. There is also absorption by the atmosphere which increases with frequency. But there are also some favorable bands where atmospheric losses are low (<1dB/km).
Read moreDiscussion of Multicarrier Beamforming particularly in the context of Massive MIMO and Millimeterwave
Read moreIt is observed that the BER performance of 64-QAM OFDM in the time-varying frequency-selective channel is quite similar to that in the static frequency-selective channel with complex filter taps. It must be noted that with 64-QAM the goal is to achieve higher bit rate, error rates can be improved using antenna diversity and channel coding schemes.
Read moreThe real benefits of OFDM become apparent in a frequency selective channel. The introduction of the cyclic prefix (guard period) allows us to remove the Intersymbol Interference (ISI) in the time domain and frequency domain equalization allows us to overcome the channel variations in the frequency domain.
Read more64-QAM is an important component of 4G/5G Air Interface that promises higher data rates and spectral efficiencies. Combined with OFDM and MIMO it successfully combats the detrimental effects of the wireless channels and provides data rates in excess of 100Mbps (peak data rate). Here, we discuss a simple example of 64-QAM modulation with OFDM in an AWGN channel. We assume a bandwidth of 1.25MHz which corresponds to an FFT size of 128.
Read more64-QAM is an important modulation scheme being used in WiMAX and LTE. It allows for transmission of 6 bits symbol which results in higher bit rate and spectral efficiency. The calculation of bit error rate of 64-QAM is a bit tricky as there are many different formulas available with varying degrees of accuracy. Here, we first calculate the bit error rate (BER) of 64-QAM using a simulation and then compare it to the theoretical curve for 64-QAM. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % FUNCTION TO CALCULATE 64-QAM BER USING SIMULATION % n_bits: Input, number of bits % EbNodB: Input, energy per bit to noise […]
Read moreWe have previously looked at a simple OFDM modulation and demodulation scheme. We saw that the BER performance of OFDM in AWGN was the same as the BER performance of the underlying modulation scheme (QPSK in this case). We will now continuously improve upon our basic simulation to get a more realistic picture. In this regard we introduce the cyclic prefix which is used in OFDM to overcome Intersymbol Interference. The duration of the cyclic prefix is 0.8usec (16 samples at 20MHz) resulting in a symbol duration of 4usec (IEEE 802.11a). Given below is the code for OFDM modulation and demodulation […]
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