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## On the Reusage of Primary Radio Resources through the Exploitation of the Spatiotemporal Robustness of the MIMO Transmissions

### Citations

1534 | BCognitive radio: Brain-empowered wireless communications - Haykin - 2005 |

1164 | Diversity and multiplexing: a fundamental tradeoff in multiple-antenna channels - Zheng, Tse - 2003 |

448 | A survey of dynamic spectrum access - Zhao, Sadler - 2007 |

416 | A survey of spectrum sensing algorithms for cognitive radio applications - Yücek, Arslan - 2009 |

162 |
Extreme Value Theory in Engineering
- Castillo
- 1988
(Show Context)
Citation Context ...he Central Limit Theorem, any population or parent distribution having finite variance will lead to the following fulfillment: the probability density function (PDF) of the means coming from n observations (consisting each of a block or number of successive independent and identically distributed random variables) will get closer and closer to a normal distribution as n increases. So, once the Central Limit Theorem has been cited, then it is possible to introduce an analogous result which applies for the extreme values instead of the means, leading this time to a PDF having the following form [16] ( highlighting that the variable x is shown in (10) and is different to the one utilized in (7)) H ( x;K , σ ,μ ) = exp [ − ( 1 + K x − μ σ )−1/K] , for 1 + K x − μ σ > 0. (10) The above equation is known as the Generalized Extreme Value (GEV) distribution and encompasses the Gumbel (Type I), Frechet (Type II), and Weibull (Type III) distributions. In general, for some values of K (shape parameter), σ (scale parameter), and μ (location parameter) the distribution of the maximums (or minimums) must take the form of the GEV distribution, which is classified as Type III when K < 0, as Type II wh... |

155 | Spectrum sensing in cognitive radio networks: the cooperation-processing tradeoff - Ghasemi, Sousa - 2007 |

142 | CRAHNs: Cognitive Radio Ad Hoc Networks
- Akyildiz, Lee, et al.
- 2009
(Show Context)
Citation Context ...are intended to be offered. So, the idea behind the suggested scheme consists in reusing the information that is already available within the primary MIMO networks aiming at cotransmitting opportunistically in a clever manner, which at the end will allow us to make a much more efficient use of both the natural and technical resources. 1. Introduction After reviewing the vast activity related with the cognitive radio (CoRa) technology, it is quite easy to realize that the spectrum awareness turns out to be the keystone of this technology. This is because, according to the cognitive radio cycle [1], the first step for embedding cleverness to a radio transceiver has to do with the perception of the radio environment. In this regard, a methodology known as active spectrum awareness (i.e., spectrum sensing) has been widely studied for over ten years aiming at addressing this issue [2– 6]. However until now it is still unclear which is (are) going to be the globally recommended technique(s) for carrying out this task. This because nowadays there are many scientific and technical issues (not expected to be solved in less than ten years) preventing that we be able to have a full CoRa device. ... |

135 | Exploiting multi-antennas for opportunistic spectrum sharing in cognitive radio networks - Zhang, Liang - 2008 |

118 | Antenna Selection in MIMO Systems, - Sanayei, Nosratinia - 2004 |

19 | Opportunistic spectrum sharing in cognitive radio networks based on primary limited feedback - Li, Zhang, et al. - 2011 |

15 | Breaking the barriers of Shannon’s capacity: an overview - Gesbert, Akhtar - 2002 |

12 | Single carrier orthogonal multiple access technique for broadband wireless communications [Ph.D. - Myung - 2007 |

9 | Statistical analysis of the smallest singular value in MIMO transmission system,”
- Burel
- 2002
(Show Context)
Citation Context ... uplink, we refer to the particular case of having two transmit antennas and two receive antennas, just as it was described in Section 2.2. We know that after decomposing the channel matrix H (e.g., by using SVD), it is possible to obtain a matrix Σ of singular values λi: Σ = [ λ1 0 0 λ2 ] = [ λ1 0 0 λmin ] (6) highlighting that every transmitted subcarrier undergoes the impairments given by all the channels involved, and hence each of them has associated a matrix of singular values like the one shown above. In this regard, we know from matrix algebra that for any vector x the following holds [15] ‖Hx‖ ≥ λmin‖x‖, (7) where λmin is the smallest singular value of H. If x is considered as the difference between the possible transmitted symbols (i.e., x = si − s j , being i /= j): we have ∥∥ ∥H ( si − s j )∥∥ ∥ ≥ λmin ∥∥ ∥si − s j ∥∥ ∥. (8) For a symbol error to occur, the norm of the noise vector would have to go beyond half the minimum distance: ‖n‖ ≥ ( mini /= j ∥ ∥ ∥H ( si − s j )∥∥ ∥ ) 2 or ‖n‖ ≥ dmin 2 . (9) But (8) tell us that a large value of λmin guarantees a large value of dmin, leading hence to a lower probability of error. So, our hypothesis is that channel matrices having the... |

8 | Introduction to Single Carrier FDMA,” - Myung - 2007 |

5 |
SVD-based vs. Release 8 codebooks for single user MIMO LTE-A uplink,”
- Berardinelli, Sørensen, et al.
- 2010
(Show Context)
Citation Context ... steps per layer at the receiver consists in removing the cyclic prefix, putting the information into parallel form, and utilizing the M-point FFT to transform back the received information to the frequency domain, and later on a demapping procedure is carried out aiming at strictly preserving the N subcarriers allocated to that user, which are equalized on a per subcarrier procedure in order to provide a better estimation of the originally modified complex numbers. The output of the embedded MMSE equalizer (i.e., by assuming perfect channel knowledge) for the kth subcarrier can be written as [13] yeq[k] = ( F[k]HH[k]HH[k]F[k] + σ2wIR )−1 × ( F[k]HH[k]Hy[k] ) . (3) In the above equation, σ2 refers to the variance of the additive white Gaussian noise, IR has to do with an identity Journal of Electrical and Computer Engineering 3 OFDMA transmitter module per layerProcedure per subcarrier MIMO SC-FDMA transmitter (spatial multiplexing) Transmitted symbols D em u x Codeword 1 Codeword 2 Serial to parallel Serial to parallel Serial to parallel Serial to parallel Q-PSK mapping Q-PSK mapping N-point FFT N-point FFT Matrix precoder V er t. ca t. Subcarrier mapping Subcarrier mapping M-point IF... |

2 | Addressing the feasibility of Cognitive Radios [using test bed implementation and experiments for exploration and demonstration],” - Cabric - 2008 |

2 | LTE For UMTS OFDMA and SCFDMA Based Radio Acces, - Holma, Toskala - 2009 |

1 |
LTE Physical Layer Overview,”
- Wang
- 2011
(Show Context)
Citation Context ...taining the input needed by the demodulator, which provides the recovered symbols that are finally feed to a MUX and rearranged in serial form. In the SC-FDMA system a generic radio frame has a duration of 10 ms and consists of 20 slots. On the other hand, a subframe is composed by 2 slots each slot, being built from seven or six SC-FDMA symbols depending on the cyclic prefix length configuration (i.e., normal or extended). So, based on the above, it is possible to write an equation describing the way of computing the peak bit rates of the system (i.e., per every branch of the MIMO structure) [14]: Peak bit rate = (bits)(subcarriers) ( symbols per subframe ) 1 ms . (5) In the numerator, starting from left to right we have the number of bits given by the modulation in use (e.g., Q-PSK will lead to 2 bits), then the subcarriers are related with those that were allocated to the user in question, while the number of symbols per subframe depends on the cyclic prefix length just as it was mentioned before. For its part, the denominator refers to the required time for transmitting a subframe. 3. An Opportunistic Cognitive Radio Communication Model over MIMO Transmissions 3.1. The Role of the ... |