QAM – RAYmaps

June 4, 2014November 17, 2019BER Performance, Fundamentals, LTE

Theoretical BER of M-QAM in Rayleigh Fading

We have previously discussed the Bit Error Rate of M-QAM in Rayleigh Fading using Monte Carlo Simulation. We now turn our attention to calculation of Bit Error Rate (BER) of M-QAM in Rayleigh fading using analytical techniques. In particular we look at the method used in MATLAB function berfading.m. In this function the BER of 4-QAM, 16-QAM and 64-QAM is calculated from series expressions having 1, 3 and 5 terms respectively. These are given below (M is the constellation size and must be a power of 2). if (M == 4) ber = 1/2 * ( 1 – sqrt(gamma_c/k./(1+gamma_c/k)) ); elseif […]

May 22, 2012May 31, 2022BER Performance, Fundamentals, LTE, Modulation, WiMAX

M-QAM Bit Error Rate in Rayleigh Fading

We have previously discussed the bit error rate (BER) performance of M-QAM in AWGN. We now discuss the BER performance of M-QAM in Rayleigh fading. The one-tap Rayleigh fading channel is generated from two orthogonal Gaussian random variables with variance of 0.5 each. The complex random channel coefficient so generated has an amplitude which is Rayleigh distributed and a phase which is uniformly distributed. As usual the fading channel introduces a multiplicative effect whereas the AWGN is additive. The function “QAM_fading” has three inputs, ‘n_bits’, ‘M’, ‘EbNodB’ and one output ‘ber’. The inputs are the number of bits to be passed […]

May 21, 2012May 31, 2022BER Performance, Fundamentals, LTE, Modulation, WiMAX

M-QAM Bit Error Rate in AWGN

Quadrature Amplitude Modulation has been adopted by most wireless communication standards such as WiMAX and LTE. It provides higher bit rates and consequently higher spectral efficiencies. It is usually used in conjunction with Orthogonal Frequency Division Multiplexing (OFDM) which provides a simple technique to overcome the time varying frequency selective channel. We have previously discussed the formula for calculating the bit error rate (BER) of QAM in AWGN. We now calculate the same using a simple Monte Carlo Simulation. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % FUNCTION THAT CALCULATES THE BER OF M-QAM IN AWGN % n_bits: Input, number of bits % M: Input, constellation […]

December 8, 2011June 4, 2014BER Performance, LTE, WiMAX

QAM Theoretical BER in AWGN

Quadrature Amplitude Modulation (QAM) is an important modulation scheme as it allows for higher data rates and spectral efficiencies. The bit error rate (BER) of QAM can be calculated through Monte Carlo simulations. However this becomes quite complex as the constellation size of the modulation schemes increases. Therefore a theoretical approach is sometimes preferred. The BER for Gray coded QAM, for even number of bits per symbol, is shown below. Gray coding ensures that a symbol error results in a single bit error. The code for calculating the theoretical QAM BER for k even (even number of bits per symbol) […]

September 9, 2011May 31, 20225G, BER Performance, LTE, Modulation, WiMAX

BER of 64-QAM OFDM in Frequency Selective Fading-II

It 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.

July 9, 2011November 15, 2011Capacity, LTE

LTE Data Rate Calculation

Peak LTE data rate can be calculated using the following parameters: 1 Time-slot=0.5 ms (i.e 1 Sub-frame = 1 ms) 1 Time-slot=7 Modulation Symbols (when normal CP length is used) 1 Modulation Symbol=6 bits; if 64 QAM is used as modulation scheme Data rate for a single carrier=Number of symbols per time slot*Bits per symbol/Duration of a time slot=7*6/0.5e-3=84kbps If 1200 carriers (100RBs) are used then the aggregated throughput would be=1200*84kbps=100.8Mbps If 4×4 MIMO is used then the capacity would increase four fold to=403.2Mbps With 3/4 channel coding the data rate would be reduced to=302.4Mbps Note: 1. A Resource Block […]