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| {{Antennas|Antenna Techniques}}
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| '''Bell Laboratories Layered Space-Time''' ('''BLAST''') is a [[transceiver]] architecture for offering [[spatial multiplexing]] over [[multiple-input multiple-output|multiple-antenna]] [[wireless communication]] systems. Such systems have multiple antennas at both the transmitter and the receiver in an effort to exploit the many different paths between the two in a highly-[[scattering]] wireless environment. BLAST was developed by [[Gerard Foschini]] at [[Lucent Technologies]]' [[Bell Laboratories]] (now Alcatel-Lucent Bell Labs). By careful allocation of the data to be transmitted to the transmitting [[Antenna (radio)|antenna]]s, multiple [[data stream]]s can be transmitted simultaneously within a single [[frequency band]] — the [[channel capacity|data capacity]] of the system then grows directly in line with the number of antennas (subject to certain assumptions). This represents a significant advance on current, single-antenna systems.<ref>{{cite journal | author=Gerard. J. Foschini | title=Layered Space-Time Architecture for Wireless Communication in a Fading Environment When Using Multi-Element Antennas | journal=Bell Laboratories Technical Journal | year=1996 | date=October 1996 | pages=41–59 | url=http://www.ece.ualberta.ca/~hcdc/Library/StCommClass/Fosc96.pdf}}</ref>
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| ==V-BLAST==
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| '''V-BLAST''' (Vertical-Bell Laboratories Layered Space-Time) is a detection [[algorithm]] to the receipt of multi-antenna [[MIMO]] systems.<ref>{{cite journal | author=P. W. Wolniansky, G. J. Foschini, G. D. Golden, R. A. Valenzuela | title=V-BLAST: An Architecture for Realizing Very High Data Rates Over the Rich-Scattering Wireless Channel | journal=Proc. URSI ISSSE | year=1998 | date=September 1998 | pages=295–300 | url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=738086&tag=1}}</ref> Available for the first time in 1996 at [[Bell Laboratories]] in New Jersey in the United States by [[Gerard J. Foschini]]. He proceeded simply to eliminate interference caused successively issuers.
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| Its principle is quite simple: to make a first detection of the most powerful signal. It regenerates the received signal from this user from this decision. Then, the signal is regenerated subtracted from the received signal and, with this new signal, it proceeds to the detection of the second user's most powerful, since it has already cleared the first and so forth. What gives a vector containing received less interference.
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| The complete detection algorithm can be summarized as recursive as follows:
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| Initialize:
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| <math> | |
| \begin{align}
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| i&\leftarrow 1 \\
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| r_1&=r \\
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| G_1&=(H^HH+\sigma ^2I_{N_r})^{-1}H^H \\
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| k_1&=\arg \min \left \| (G_1)_j \right \|^2 \\
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| \end{align}
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| </math>
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| Recursive:
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| <math> | |
| \begin{align}
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| w_k &= (G_i)_k \\
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| y_k&=w^T_k\times r_i \\
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| \hat{s}_k&=sign(y_k) \\
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| r_{i+1}&=r_i-\hat{s}_k(H)_{ki} \\
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| G_{i+1}&=((H^H_iH_i)+\sigma^2I_{Nr})^{-1}H^H_i \\
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| k_{i+1}&=\arg \min \left\| (G_{i+1})_j \right\|^2 \\
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| i &\leftarrow i+1
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| \end{align}
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| </math>
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| <!-- Please fix as necessary -->
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| ==See also==
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| *[[Space–time code]] — a means for using multiple antennas to improve reliability rather than data-rate.
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| *[[Telecommunication]]
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| ==References==
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| {{reflist}}
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| ==Further reading==
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| * {{Cite book |last=Jankiraman |first=Mohinder |title=Space-time codes and MIMO systems |year=2004 |publisher=Artech House |url=http://books.google.com/books?id=HU-T7y16AGEC&printsec=frontcover }}
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| ==External links==
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| * http://www.alcatel-lucent.com/wps/portal/BellLabs
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| [[Category:Antennas]]
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| [[Category:Detection theory]]
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| {{wireless-stub}}
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