Inter-Symbol Interference in LTE Definition: ISI is a phenomenon in LTE where symbols transmitted over a communication channel overlap, causing distortion in the received signal. Causes: Multipath Propagation: Signals take multiple paths with different delays, leading to overlapping symbols. Time Dispersion: Variation in signal arrival times at the receiver contributes to ISI. Impact on LTE: … Read more
Constellation in LTE In LTE (Long-Term Evolution), the term “constellation” typically refers to the modulation scheme used for transmitting data over the air interface. LTE uses Quadrature Amplitude Modulation (QAM) to encode multiple bits into a single symbol. The constellation diagram visually represents how the amplitude and phase of the modulated signals correspond to specific … Read more
RF engineering is a trade off between: required radio spectrum (bandwidth), speed of data transmission (bit rates) and complexity of implementation. The pulse form used to modulate complex data symbols to the radio carrier frequency is the major element of this story. Over the years several pulse forms and their associated pulse shaping filters have … Read more
The 3G LTE uses 3 Quadrature Amplitude Modulations (QAMs) depending on the radio quality. QAM uses both the amplitude and the phase. LTE devices use QPSK, 16QAM and 64QAM to modulate data and control information. The eNodeB supports all of these modulation techniques for the downlink direction. However, 64QAM is optional in the uplink direction. … Read more
Different modulation methods corresponding to different transmitting abilities in air interface. R99/R4: QPSK HSDPA: QPSK or 16QAM The UTRAN air interface uses QPSK modulation in the downlink, although HSDPA may also employ 16 Quadrature Amplitude Modulation (16QAM). 16QAM requires good radio conditions to work well. As seen, with 16QAM also the amplitude of the signal … Read more
SC-FDMA utilizes single carrier modulation, DFT-spread orthogonal frequency multiplexing, and frequency domain equalization. LTE uses OFDMA on the DL. It allocates DL bandwidth to the user based on resource blocks, rather than individual subcarriers. When the signal is a combination of subcarriers, high amplitude power peaks can occur. The base stations power amplifiers are designed … Read more