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

Revision as of 07:31, 15 February 2009

Revision as of 20:52, 19 May 2009

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In the downlink (one base station transmitting to one or more terminals), MC-CDMA typically reduces to Multi-Carrier Code Division Multiplexing. All user signals can easily be synchronized, and all signals on one subcarrier experience the same radio channel properties.

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 I-FFT.

== Variants ==

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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.

As an example of how the 2D spreading on [[VSF-OFCDM]] works, if you take the first data symbol, ''d''₀, and a spreading factor in the time ___domain, ''SF''_time, of length 4, and a spreading factor in the frequency ___domain, ''SF''_frequency of 2, then the data symbol, ''d''₀, will be multiplied by the length-2 frequency-___domain PN codes and placed on subcarriers 0 and 1, and these values on subcarriers 0 and 1 will then be multiplied by the length-4 time-___domain PN code and transmitted on [[OFDM]] symbols 0, 1, 2 and 3.<ref>http://citeseer.ist.psu.edu/atarashi02broadband.html Broadband Packet Wireless Access Based On VSF-OFCDM And MC/DS-CDMA (2002) Atarashi et al.</ref>

[[NTT DoCoMo]] has already achieved 1 Gbit/s transmissions to receivers travelling at 20 &nbsp;km/h and 2.5 Gbit/s to stationary receivers using its [[4G]] prototype system in a 100 MHz-wide channel. This [[4G]] prototype system also uses a 4x4 antenna [[MIMO]] configuration, and [[turbo coding]] for error correction coding.

==References==

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==Literature==

* N. Yee, J.P.M.G. Linnartz and G. Fettweis, "Multi-Carrier CDMA in indoor wireless Radio Networks", IEEE Personal Indoor and Mobile Radio Communications (PIMRC) Int. Conference, Sept. 1993, Yokohama, Japan, pp. 109-113109–113 (1993: first paper proposing the system and the name MC-CDMA)

* K. Fazel and L. Papke, "On the performance of convolutionally-coded CDMA/OFDM for mobile communication system", IEEE Personal Indoor and Mobile Radio Communications (PIMRC) Int. Conference, Sept. 1993, Yokohama, Japan, pp. 468-472468–472

* A. Chouly, A. Brajal, and S. Jourdan, "Orthogonal multicarrier techniques applied to direct sequence spread spectrum CDMA systems," in Proceedings of Global Telecommunications Conference (GLOBECOM'93), pp. 1723-17281723–1728, Houston, Tex, USA, November 1993.

* N.Yee, J.P.M.G. Linnartz and G. Fettweis, "Multi-Carrier-CDMA in indoor wireless networks", IEICE Transaction on Communications, Japan, Vol. E77-B, No. 7, July 1994, pp. 900-904900–904.

* J.P.M.G. Linnartz, "Performance Analysis of Synchronous MC-CDMA in mobile Rayleigh channels with both Delay and Doppler spreads", IEEE VT, Vol. 50, No. 6, Nov. 2001, pp 1375-13871375–1387. [http://www.wireless.per.nl/wireless/articles/01_j2.mc_cdma_doppler.pdf ''PDF'']

* K. Fazel and S. Kaiser, ''Multi-Carrier and Spread Spectrum Systems: From OFDM and MC-CDMA to LTE and WiMAX'', 2nd Edition, John Wiley & Sons, 2008, ISBN 978-0-470-99821-2.

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{{Channel access methods}}

{{telecomm-stub}}