Multi-carrier code-division multiple access: Difference between revisions

Revision as of 21:50, 9 April 2020

Revision as of 21:36, 10 August 2020

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A number of alternative possibilities exist as to how this frequency ___domain spreading can take place, such as by using a long PN code and multiplying each data symbol, d_i, on a subcarrier by a chip from the PN code, c_i, or by using short PN codes and spreading each data symbol by an individual PN code — i.e. d_i is multiplied by each c_i and the resulting vector is placed on N_freq subcarriers, where N_freq is the PN code length.

Once frequency ___domain spreading has taken place and the [[OFDM]] subcarriers have all been allocated values, [[OFDM]] modulation then takes place using the [[Fastfast Fourier Transformtransform|IFFT]] to produce an [[OFDM]] symbol; the [[OFDM]] guard interval is then added; and if transmission is in the downlink direction each of these resulting symbols are added together prior to transmission.

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]].