Contents
What is index modulation in OFDM?
More specifically, it relates to adding an additional dimension to the conventional two-dimensional (2-D) amplitude/phase modulation (APM) techniques, i.e. amplitude shift keying (ASK) and quadrature amplitude modulation (QAM). …
What is the index modulation?
Index modulation (IM) refers to a family of modulation techniques that rely on the activa- tion states of some resources/building blocks for information embedding. A distinct feature of IM is that part of the information is implicitly embedded into the transmitted signal.
Which modulation is used in OFDM?
Orthogonal Frequency Division Multiplexing (OFDM) is a digital multi-carrier modulation scheme that extends the concept of single subcarrier modulation by using multiple subcarriers within the same single channel.
What is OFDM channel?
OFDM is a subset of frequency division multiplexing in which a single channel utilizes multiple sub-carriers on adjacent frequencies. In addition the sub-carriers in an OFDM system are overlapping to maximize spectral efficiency. Ordinarily, overlapping adjacent channels can interfere with one another.
What is the formula of modulation index?
The modulation index is ratio of modulating signal voltage(Vm) to the carrier voltage(Vc). The modulation index equation is as follows. m = Vm/Vc. The modulation index should be a number between 0 and 1. When m is greater than 1, severe distortion results into the modulated waveform.
What is meant by modulation?
Modulation is the process of converting data into radio waves by adding information to an electronic or optical carrier signal. A carrier signal is one with a steady waveform — constant height, or amplitude, and frequency.
Can modulation index be greater than 1?
If the modulation index is greater than 1, then we call this condition over modulation. In such cases, the baseband signal is not preserved in the envelope of the AM signal and therefore, the recovered signal is distorted at the output of the receiver.
What is the formula for modulation index?
The FM modulation index is equal to the ratio of the frequency deviation to the modulating frequency. From the formula and definition of the modulation index, it can be seen that there is no term that includes the carrier frequency and this means that it is totally independent of the carrier frequency.
What is the use of modulation index?
The modulation index and modulation depth figures are widely used when describing the modulation applied to an amplitude modulated signal. Too little and the signal will not appear to have sufficiently loud audio. Too much and the signal will create interference well beyond the channel on which it is operating.
How is OFDM-im adapted to realistic channel conditions?
Then, the proposed scheme is adapted to realistic channel conditions such as imperfect channel state information and very high mobility cases by modifying the receiver structure. The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors.
Why is orthogonal frequency division multiplexing better than classical OFDM?
It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions.
How is the error probability of OFDM-im derived?
The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors. For the mobility case, several interference unaware/aware detection methods are proposed for the new scheme.