What do you mean by orthogonal frequency division multiplexing?
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.
What is OFDM system?
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 OFDM system explain with the help of a block diagram?
1. An OFDM is an Multicarrier Modulation Technique that use a overlap signals to divide the frequency selective channel into a number of narrow band flat fading channel. The block diagram of OFDM is shown in above figure. In this system input data are FEC coded with technique such as convolution code.
What are the applications of OFDM?
Orthogonal frequency division multiplexing (OFDM) is a modulation technique that is used in several applications ranging from cellular systems (3GLTE, WiMAX), wireless local area networks (LANs), digital audio radio, underwater communications, and even optical light modulation.
What is a characteristic of orthogonal frequency division multiplexing OFDM channel subcarriers?
OFDM: Orthogonal Frequency Division Multiplexing, is a form of signal modulation that divides a high data rate modulating stream placing them onto many slowly modulated narrowband close-spaced subcarriers, and in this way is less sensitive to frequency selective fading.
Which of the following 802.11 standards uses orthogonal frequency division multiplexing?
802.11a standard
The 802.11a standard uses the same core protocol as the original standard and was the first of the 802.11 family to operate in the 5 GHz band. It uses a 52-subcarrier orthogonal frequency-division multiplexing (OFDM) with a maximum raw data rate of 54 Mbit/s, which typically yields a throughput in the mid-20 Mbit/s.
What is orthogonal channel?
Two radio-frequency channels in which the emissions have orthogonal polarizations . Simply,we can say that Two transmissions are orthogonal if they have no influence on one another. This can be achieved in four domains: time, space, frequency and code. All channels can be considered as orthogonal channels.
What is the difference between OFDM and Ofdma?
OFDMA stands for orthogonal frequency division multiplexing access. It is an extension of OFDM. The difference is that OFDMA is multi-user where OFDM is single-user. It has 3x higher throughput than single-user OFDM for short packets of data or multiple endpoints.
What are orthogonal channels?
What are orthogonal carriers?
The use of orthogonal subcarriers allows more subcarriers per bandwidth resulting in an increase in spectral efficiency. In a perfect OFDM signal, Orthogonality prevents interference between overlapping carriers. In FDM systems, any overlap in the spectrums of adjacent signals will result in interference.
How does orthogonality in OFDM allow for increased capacity?
How does orthogonality allow for increased capacity? Spectral density -> 0, signals can overlap, allows signals to be packed together.
What are subcarriers in OFDM?
A single OFDM symbol contains 52 subcarriers; 48 are data subcarriers and 4 are pilot subcarriers. The center, “DC” or “Null”, zero subcarrier is not used. All data subcarriers use the same modulation format within a given burst. However, the modulation format can vary from burst to burst.
What is OFDM orthogonal frequency division multiplexing?
OFDM, Orthogonal Frequency Division Multiplexing uses multiple close spaced carriers each with low rate data for resilient communications. OFDM Orthogonal Frequency Division Multiplexing Includes: OFDM, Orthogonal Frequency Division Multiplexing is a form of signal waveform or modulation that provides some significant advantages for data links.
What is the difference between OFDM and modulation?
Orthogonal Frequency Division Multiplexing (OFDM) Modulation – a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. Multiplexing – method of sharing a bandwidth with other independent data channels. OFDM is a combination of modulation and multiplexing.
What is OFDM spread-spectrum technique?
Orthogonal frequency division multiplexing (OFDM) spread-spectrum technique takes a signal and transmits multiple signals simultaneously rather than one single-signal transmission (see Table 5.5 ). OFDM breaks down the frequency being used into smaller 1 MHz frequencies, and each signal travels within its own unique frequency range or carrier.
What is modulation in the frequency domain on OFDM subcarriers?
Therefore, modulation in the frequency domain on OFDM subcarriers is equivalent to modulation in conventional temporal systems. As mentioned earlier, the typical modulation scheme of the subcarriers is PSK, differential PSK, or QAM with either coherent or noncoherent demodulation.