Citation Context

...O (multiple-input, multiple-output). This technique promises significant enhancements of system performance without requiring the allocation of extra spectrum. Since the first analytic investigations =-=[1, 2, 3]-=- the scientific research in this field has made vast progress and MIMO is believed to be the key technology for future wireless standards. Multiple antennas can be applied in various ways. A technique...

Citation Context

...O (multiple-input, multiple-output). This technique promises significant enhancements of system performance without requiring the allocation of extra spectrum. Since the first analytic investigations =-=[1, 2, 3]-=- the scientific research in this field has made vast progress and MIMO is believed to be the key technology for future wireless standards. Multiple antennas can be applied in various ways. A technique...

Citation Context

...s, parameterized by ρr. 39 Chapter 4 Alamouti STBC In the following antenna selection is applied to a system that utilizes the well known Alamouti transmit diversity scheme. This STBC was proposed in =-=[24]-=- and uses two transmit antennas and one receive antenna simultaneously. Its most attractive features are given by: • Diversity order of two. • Only one receive antenna. • Low complexity detection prin...

Citation Context

...independent data streams. This is done by turning multipath propagation, normally a handicap of mobile communication into a benefit for the system [4]. One alternative method called space-time coding =-=[5, 6]-=- improves the link reliability by introducing so called spatial diversity (also referred to as antenna diversity). A single data stream is encoded and the resulting signals transmitted from the multip...

Citation Context

...a trellis search and its complexity grows exponentially with the number of used antennas and the length of the trellis. The second category of space-time codes is based on block orientated processing =-=[9, 10]-=-. In the first trivial encoding step the bit sequence is mapped onto a symbol sequence. Subsequently, a block of successive symbols is linearly combined to a space-time coding matrix whose columns rep...

Citation Context

...a trellis search and its complexity grows exponentially with the number of used antennas and the length of the trellis. The second category of space-time codes is based on block orientated processing =-=[9, 10]-=-. In the first trivial encoding step the bit sequence is mapped onto a symbol sequence. Subsequently, a block of successive symbols is linearly combined to a space-time coding matrix whose columns rep...

Citation Context

...rom the multiple antenna elements are highly correlated. This redundancy in time and space enables the receiver to optimally combine the signal components picked up by the respective receive antennas =-=[7]-=-. While spatial multiplexing directly tries to improve the data-rate of the system, one can attain a similar benefit with the help of space-time coding. In a multipath fading situation the additional ...

Citation Context

...ith a rate of R = 0.75. However, for the code that will presented in the remainder of this chapter another approach is taken. 5.1 The Extended Alamouti Scheme This specific STBC was first proposed in =-=[25]-=-. It also utilizes four transmit antennas and offers a transmission rate of one in combination with an arbitrary complex symbol constellation. As has been mentioned above, this unavoidably means that ...

Citation Context

...O (multiple-input, multiple-output). This technique promises significant enhancements of system performance without requiring the allocation of extra spectrum. Since the first analytic investigations =-=[1, 2, 3]-=- the scientific research in this field has made vast progress and MIMO is believed to be the key technology for future wireless standards. Multiple antennas can be applied in various ways. A technique...

Citation Context

...rocessing power becomes ever cheaper, the RF elements are expensive and do not follow Moore’s law.” 2 Chapter 1: Introduction One attractive way to reduce the number of RF chains is antenna selection =-=[13, 14, 15, 16]-=-. Systems equipped with this capability optimally choose a subset of the available transmit and receive antennas and only process the signals associated with them. This allows to maximally benefit fro...

Citation Context

... spectrum efficiency by simultaneous transmission of independent data streams. This is done by turning multipath propagation, normally a handicap of mobile communication into a benefit for the system =-=[4]-=-. One alternative method called space-time coding [5, 6] improves the link reliability by introducing so called spatial diversity (also referred to as antenna diversity). A single data stream is encod...

Citation Context

...aster then in the domain of low cost integration of high frequency analog equipment. Consequently, the need for more DSP power will eventually become less of a problem. The following quote taken from =-=[12]-=- confirms this conjecture: “While additional antenna elements (patch or dipole antennas) are usually inexpensive, and the additional digital signal processing power becomes ever cheaper, the RF elemen...

Citation Context

...rocessing power becomes ever cheaper, the RF elements are expensive and do not follow Moore’s law.” 2 Chapter 1: Introduction One attractive way to reduce the number of RF chains is antenna selection =-=[13, 14, 15, 16]-=-. Systems equipped with this capability optimally choose a subset of the available transmit and receive antennas and only process the signals associated with them. This allows to maximally benefit fro...

Citation Context

...independent data streams. This is done by turning multipath propagation, normally a handicap of mobile communication into a benefit for the system [4]. One alternative method called space-time coding =-=[5, 6]-=- improves the link reliability by introducing so called spatial diversity (also referred to as antenna diversity). A single data stream is encoded and the resulting signals transmitted from the multip...

Citation Context

... ρt, ρr ≤ 1 . These Toeplitz structured matrices are appropriate for modelling the statistical behavior when the antenna elements at the transmitter as well as at the receiver are collocated linearly =-=[22]-=-. When applying the synthetic correlation matrices given by (2.17) and (2.18) the normalization factor in (2.16) needs to be omitted, resulting in: Hcorr = (Rr) 1 2H[(Rt) 1 2 ]T (2.19) because otherwi...

Citation Context

...rocessing power becomes ever cheaper, the RF elements are expensive and do not follow Moore’s law.” 2 Chapter 1: Introduction One attractive way to reduce the number of RF chains is antenna selection =-=[13, 14, 15, 16]-=-. Systems equipped with this capability optimally choose a subset of the available transmit and receive antennas and only process the signals associated with them. This allows to maximally benefit fro...

Citation Context

... of the received signal. Within given transmit-power constraints this can for instance be exploited by applying higher modulation formats, thus indirectly enhancing the achievable spectrum efficiency =-=[8]-=-. Generally, space-time codes can be divided into two classes. The first group is called space-time trellis codes (STTC) [6]. As the name implies their encoding procedure involves trellis stages to de...

Citation Context

...rocessing power becomes ever cheaper, the RF elements are expensive and do not follow Moore’s law.” 2 Chapter 1: Introduction One attractive way to reduce the number of RF chains is antenna selection =-=[13, 14, 15, 16]-=-. Systems equipped with this capability optimally choose a subset of the available transmit and receive antennas and only process the signals associated with them. This allows to maximally benefit fro...

Citation Context

...s an estimate for the diversity order for this system with D=2.2. Another point of interest are the statistical properties of the channel dependent interference parameter X in the unselected case. In =-=[26]-=- the analytic 58 5.2 Selection Criteria Chapter 5: Extended Alamouti STBC solution for the pdf of X is found: pdfX(α) = { 3 4 (1− α2) , for|α| < 1, 0 , elsewhere. (5.8) In the next section antenna sel...

Citation Context

... Selection Approaches An alternative way of improving the statistics of X and thereby enhancing the performance of the resulting closed loop system is the application of code selection as proposed in =-=[17]-=-. Here, the feedback link is utilized to select one out of a small set of available STBCs which is then used for transmission. These STBCs are all similarly structured and exhibit the same instantaneo...

Citation Context

...wing to keep the notation less bloated). Real and imaginary parts of h are modelled as i.i.d. real valued gaussian random variables with zero mean: h , X + jY . Thus, the pdfs of X and Y are given by =-=[23]-=-: pdfX(ξ) = 1√ 2piσ exp −ξ2 2σ2 ξ ∈ R , (2.8) pdfY (ζ) = 1√ 2piσ exp −ζ2 2σ2 ζ ∈ R . (2.9) Since both random variables are statistically independent and zero mean the mean and variance of h work out t...