M-ary Modulation and Error Performance

A type of digital modulation where data is split into parallel streams and transmitted over multiple subcarriers. Each subcarrier carries a smaller amount of data at a specific frequency, allowing for higher data rates over a given bandwidth.

Represents data as combinations of in-phase (I) and quadrature (Q) components in a 2D plane. Each combination corresponds to a unique four-bit code, increasing data density.

In OFDM, subcarrier frequencies are spaced by the data rate divided by the number of subcarriers.

The process of converting a serial data stream into multiple parallel data streams for parallel processing. This is a crucial step in OFDM to feed the parallel subcarriers.

The digital signal used to modulate the subcarriers. It typically takes the form of binary bipolar values.

Each subcarrier is modulated using a separate M-QPSK modulator, effectively splitting the overall data stream into smaller chunks.

The resulting modulated signal after combining all modulated subcarriers. It is the final signal ready for transmission.

The bandwidth of the transmitted OFDM signal is determined by the number of subcarriers and the data rate.

The duration of the Cyclic Prefix (CP) in OFDM systems must be greater than the channel's time spread parameter. This parameter is determined by the environment, and increasing the CP allows for single frequency networks (SFN).

The Peak-to-Average Power Ratio (PAPR) is a measure of the peak signal power divided by the average signal power. It describes how much the signal's power fluctuates and is important for optimizing transmitter design.

OFDM allows multiple mobile users to access different sets of subcarriers in a frequency band. This technique is called OFDMA and is especially important in the uplink (mobile to base station), where proper synchronization and power adjustment are crucial to ensure successful signal reception.

In the LTE 20 MHz 32-QAM system, the data bitrate is calculated by considering the number of subcarriers, subcarrier spacing, and the modulation scheme. The bitrate can also be affected by the length of the Cyclic Prefix (CP) used, with a longer CP leading to a lower bitrate.

The total number of subcarriers used in the system, along with their spacing, determines the overall bandwidth of the LTE system. The subcarrier spacing is the frequency difference between adjacent subcarriers.

A mathematical concept where vectors are perpendicular to each other.

A modulation scheme that uses multiple subcarriers to transmit data simultaneously. Each subcarrier is orthogonal to the others, ensuring that they don't interfere with each other.

The frequency separation between two adjacent subcarriers in an OFDM system.

The relationship between the subcarrier spacing and the symbol duration in OFDM. The subcarriers are spaced so that their symbols are orthogonal, preventing interference.

The process of combining multiple digital data streams into one signal for transmission.

A type of multiplexing where the total bandwidth is divided into multiple frequency bands, each carrying a separate data stream.

A type of multiplexing where data is transmitted over multiple subcarriers that are orthogonal to each other.

The frequency spectrum of an OFDM signal, where each subcarrier is represented by a separate frequency band.

The total bandwidth used by an OFDM system, which is the sum of the bandwidths of all the subcarriers.

The process of converting a block of data from the time domain into the frequency domain using the Inverse Discrete Fourier Transform (IDFT). This allows for efficient transmission over a wide frequency band.

The period before and after each OFDM symbol, containing a copy of the last part of the data symbol. This helps to mitigate the effects of multipath fading by creating a smooth transition between symbols and reducing inter-symbol interference.

The process of converting a single stream of data into multiple parallel streams. This allows for each data stream to be transmitted over a separate subcarrier in OFDM.

A digital-to-analog converter that converts discrete-time digital signals into continuous-time analog signals. Used to convert the digital data into analog signals for transmission.

A modulation scheme that uses multiple levels of amplitude and phase shifts to represent digital data. This allows for higher data rates and improved spectral efficiency compared to simpler modulation schemes.

An interval between the end of one OFDM symbol and the beginning of the next, allowing time for the signal to decay and preventing inter-symbol interference.

The time it takes for a signal to decay to a certain level. The guard interval should be longer than the channel's coherence time for effectively mitigating inter-symbol interference.

A digital modulation scheme where the transmitted signal's phase is varied to represent different data bits. The number of distinct phase shifts, or symbols, is denoted by 'M', where 'M = 2^n' and 'n' is the number of bits per symbol. Examples: 8-PSK, 16-PSK, 32-PSK.

The number of distinct phase shifts or symbols used in M-PSK modulation. It determines the number of bits represented by each symbol. It's calculated as M = 2^n, where 'n' is the number of bits per symbol.

A graphical representation of the possible signal states in M-PSK modulation. Each point in the constellation represents a unique combination of phase and amplitude.

A method for encoding data bits into symbols, where the phase shift between consecutive symbols is kept minimal to minimize error propagation. This reduces the probability of incorrect decoding.

It measures the probability of an error occurring during transmission in M-PSK modulation. It's influenced by the signal-to-noise ratio and the number of symbols (M).

A digital modulation scheme that combines multiple amplitude levels with multiple phase shifts to represent different symbols. It offers a more efficient way to transmit data than M-PSK alone. Example: 16-QAM.

A graphical representation of the possible signal states in M-QAM modulation. Each point in the constellation represents a unique combination of amplitude and phase, forming a constellation diagram that looks like a grid.

It measures the probability of an error occurring during transmission in M-QAM modulation. It's influenced by the signal-to-noise ratio and the chosen constellation size (M).

A measure of the efficiency of a modulation scheme in terms of the number of bits transmitted per second per unit of bandwidth. Higher spectral efficiency means more data can be transmitted over a given bandwidth.

A block diagram for the combined process of modulating both the in-phase (I) component and quadrature (Q) component of the signal in both M-PSK and M-QAM.