Multi-carrier code-division multiple access

multi-carrier code division multiple accessMC-CDMAmulti-carrierMulti-carrier CDMAmulti-carrier communication systemVSF-OFCDM
Multi-carrier code-division multiple access (MC-CDMA) is a multiple access scheme used in OFDM-based telecommunication systems, allowing the system to support multiple users at the same time over same frequency band.wikipedia
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Channel access method

multiple accessmultiple access methodchannel access
Multi-carrier code-division multiple access (MC-CDMA) is a multiple access scheme used in OFDM-based telecommunication systems, allowing the system to support multiple users at the same time over same frequency band.
Other techniques include orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA).

Orthogonal frequency-division multiplexing

OFDMCOFDMOFDM system comparison table
Multi-carrier code-division multiple access (MC-CDMA) is a multiple access scheme used in OFDM-based telecommunication systems, allowing the system to support multiple users at the same time over same frequency band.
In multi-carrier code division multiple access (MC-CDMA), also known as OFDM-CDMA, OFDM is combined with CDMA spread spectrum communication for coding separation of the users.

4G

4G LTE3G evolution4-G
2-dimensional spreading in both the frequency and time domains is also possible, and a scheme that uses 2-D spreading is VSF-OFCDM (which stands for variable spreading factor orthogonal frequency code-division multiplexing), which NTT DoCoMo is using for its 4G prototype system. This 4G prototype system also uses a 12×12 antenna MIMO configuration, and turbo coding for error correction coding.
As seen below, the spread spectrum radio technology used in 3G systems is abandoned in all 4G candidate systems and replaced by OFDMA multi-carrier transmission and other frequency-domain equalization (FDE) schemes, making it possible to transfer very high bit rates despite extensive multi-path radio propagation (echoes).

Direct-sequence spread spectrum

DSSSDirect Sequence Spread SpectrumDS-CDMA
One way of interpreting MC-CDMA is to regard it as a direct-sequence CDMA signal (DS-CDMA), which is transmitted after it has been fed through an inverse FFT (fast Fourier transform). An alternative form of multi-carrier CDMA, called MC-DS-CDMA or MC/DS-CDMA, performs spreading in the time domain, rather than in the frequency domain in the case of MC-CDMA — for the special case where there is only one carrier, this reverts to standard DS-CDMA.

Hadamard transform

Hadamard gateWalsh transformWalsh–Hadamard transform
In such case a preferred system implementation is to take N user bits (possibly but not necessarily for different destinations), to transform these using a Walsh Hadamard Transform, followed by an IFFT.

Fast Fourier transform

FFTFast Fourier Transform (FFT)Fast Fourier Transforms
One way of interpreting MC-CDMA is to regard it as a direct-sequence CDMA signal (DS-CDMA), which is transmitted after it has been fed through an inverse FFT (fast Fourier transform).

Code-division multiple access

CDMAcode division multiple accessCDMA-450
An alternative form of multi-carrier CDMA, called MC-DS-CDMA or MC/DS-CDMA, performs spreading in the time domain, rather than in the frequency domain in the case of MC-CDMA — for the special case where there is only one carrier, this reverts to standard DS-CDMA.

NTT Docomo

DoCoMoDoCoMo Capital90xi Series Mobile Phone
2-dimensional spreading in both the frequency and time domains is also possible, and a scheme that uses 2-D spreading is VSF-OFCDM (which stands for variable spreading factor orthogonal frequency code-division multiplexing), which NTT DoCoMo is using for its 4G prototype system.

MIMO

multiple-input multiple-outputMultiple-input multiple-output communicationsmultiple-input and multiple-output
This 4G prototype system also uses a 12×12 antenna MIMO configuration, and turbo coding for error correction coding.

Turbo code

turbo codesTurbo codingTurbo
This 4G prototype system also uses a 12×12 antenna MIMO configuration, and turbo coding for error correction coding.

Orthogonal frequency-division multiple access

OFDMAOrthogonal Frequency Division Multiple AccessOFDM
* OFDMA, an alternative multiple access scheme for OFDM systems, where the signals of different users are separated in the frequency domain by allocating different sub-carriers to different users.

Frequency domain

frequency-domainFourier spaceFourier domain
* OFDMA, an alternative multiple access scheme for OFDM systems, where the signals of different users are separated in the frequency domain by allocating different sub-carriers to different users.

Georgios B. Giannakis

G GiannakisG. GiannakisGiannakis
Seminal work includes the development of linear precoding wireless communication systems, which provided a unified approach for designing space-time block codes that achieve data high rates and reliability, and proposal of zero-padding as an alternative to the cyclic prefix for multi-carrier communication systems, which had impact in the multi-band ultra wide band standard.

Modulation

modulatedmodulatordigital modulation
OFDM can be extended to multi-user channel access method in the orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA) schemes, allowing several users to share the same physical medium by giving different sub-carriers or spreading codes to different users.

Mobile phone features

featuresCameras in mobile phonesmobile phone content
A final interesting case is that of mobiles covering the DS-WCDMA and MC-CDMA 3G variants of the CDMA-2000 protocol.