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

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'''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.

{{more footnotes|date=April 2016}}

'''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.

MC-CDMA spreads each user symbol in the frequency ___domain. That is, each user symbol is carried over multiple parallel subcarriers, but it is phase shifted (typically 0 or 180 degrees) according to a code value. The code values differ per subcarrier and per user. The receiver combines all subcarrier signals, by weighing these to compensate varying signal strengths and undo the code shift. The receiver can separate signals of different users, because these have different (e.g. orthogonal) code values.

Since each data symbol occupies a much wider bandwidth (in hertz) than the data rate (in bit/s), a signal-to-noise-plus-interference ratio (if defined as signal power divided by total noise plus interference power in the entire transmission band) of less than 0  dB is feasible.

One way of interpreting MC-CDMA is to regard it as a direct-sequence CDMA signal ([[DS-CDMA]])

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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 5 Gbit/s transmissions to receivers travelling at 10&nbsp;km/h using its [[4G]] prototype system in a 100&nbsp; MHz-wide channel. This [[4G]] prototype system also uses a 12x12 antenna [[MIMO]] configuration, and [[turbo coding]] for error correction coding.<ref>{{cite web|url = http://www.nttdocomo.com/pr/2007/001319.html|date=2007-02-09|publisher=[[NTT DoCoMo]] Press|title=DoCoMo Achieves 5&nbsp;Gbit/s Data Speed}}</ref>

Summary

1. [[OFDMA]] with frequency spreading (MC-CDMA)

2. [[OFDMA]] with time spreading ([[MC-DS-CDMA]] and [[MT-CDMA]])

3. [[OFDMA]] with both time and frequency spreading (Orthogonal Frequency Code Division Multiple Access([[OFCDMA]]))

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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.&nbsp; 109–113 (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.&nbsp; 468–472

* 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.&nbsp;1723–1728, 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.&nbsp;900–904.

* 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.&nbsp; 1723–1728, 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.&nbsp; 900–904.

* 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 1375–1387. [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.

* Hughes Software Systems, [http://www.hssworld.com/whitepapers/whitepaper_pdf/service4.pdf ''Multi Carrier Code Division Multiple Access''], March 2002.

* German Aerospace Center, Institute of Communications and Navigation, [http://www.kn-s.dlr.de/mcss2007/history.php ''History of Multi-Carrier Code Division Multiple Access (MC-CDMA) and Multi-Carrier Spread Spectrum Workshop''], November 2006.

* Wireless Communication Reference Web Site, section about [http://www.wirelesscommunication.nl/reference/chaptr05/mccdma/mccdma.htm''MC-CDMA''], 2001.

==See also==

* [[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.

* [[Hybrid OFDM]], This page covers Hybrid OFDM referred as OFCDM which is a combination of OFDM and CDMA.It provides comparison between MC/DS-CDMA,MC-CDMA and OFCDM, Visit http://www.rfwireless-world.com/Terminology/Hybrid-OFDM-OFCDM.html.

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