text:
- Research Article
- Open Access
A Time-Variant MIMO Channel Model Directly Parametrised from Measurements
© Nicolai Czink et al. 2009
- Received: 2 July 2008
- Accepted: 12 March 2009
- Published: 26 April 2009
This paper presents the Random-Cluster Model (RCM), a stochastic time-variant, frequency-selective, propagation-based MIMO channel model that is directly parametrised from measurements. Using a fully automated algorithm, multipath clusters are identified from measurement data without user intervention. The cluster parameters are then used to define the propagation environment in the RCM. In this way, the RCM provides a direct link between MIMO channel measurements and MIMO channel modelling. For validation, we take state-of-the-art MIMO measurements, and parametrise the RCM exemplarly. Using three different validation metrics, namely, mutual information, channel diversity, and the novel Environment Characterisation Metric, we find that the RCM is able to reflect the measured environment remarkably well.
- Mutual Information
- MIMO Channel
- Kernel Density Estimator
- Reference Channel
- Multipath Component
1. Introduction
Multiple-input multiple-output technology (MIMO) [1] made its way in the recent years from an information-theoretic shooting star [2] to actual products on the mass market [3, 4]. Currently the 3GPP [5] is standardising MIMO for the next generation's mobile communications, what is called Long Term Evolution (LTE) as well as IEEE is standardising MIMO for WiMAX [6]. Already information theory told that the promise of increased spectral efficiency of MIMO systems is only available when the radio channel permits, but this seems to have faded out of people's memory.
Despite this fact, numerous algorithms were developed, mostly considering ideal uncorrelated i.i.d. Rayleigh fading channels between the transmit and receive antennas, which is only true in rich-scattering environments with sufficiently large antenna spacings at both transmitter and receiver. Otherwise, the performance of the algorithms deteriorates. To reach the goal of gigabit transmissions over the wireless link, one needs to include the knowledge of the actual channel into the algorithms. Thus, an accurate model of the propagation channel is paramount.
One can distinguish between three different types of MIMO channel models: (i) channel models for developing signal-processing algorithms, for example, [7, 8]. These models describe the radio channel by the correlations between the different links, established between individual antenna elements. This makes the model mathematically tractable, yet inaccurate when it comes to reflecting real-world propagation conditions, because current correlation-based models always base on the Rayleigh-fading (or, to some extent, Ricean fading) assumption. While the so-called "Kronecker" model [7] is favoured by many people because it can be treated by random-matrix theory [9], the Weichselberger Model [8] shows a much better fit to measurement data [10, 11]. (ii) channel models for MIMO deployment in a given environment, for example, ray-tracing [12, 13]. These models try to predict MIMO conditions given a map (or floor plan) for optimal positioning of MIMO-enabled base stations, which comes with high demands on computational power and accuracy of environment data bases; (iii) channel models for testing of algorithms and systems, for example, [14–16]. These models typically represent a certain kind of propagation scenario (like indoor offices, or outdoor picocells), without considering a specific propagation environment. This is achieved by modelling the propagation environment in a stochastic way. Such models usually have a medium complexity and represent realistic channels very well, however a closed-form expression of the channel model, as in the first case, does not exist. The major difference between these models is their ability to describe time variation.
A time-variant channel is an essential feature of mobile communications. The 3GPP Spatial Channel Model (SCM) [14] is well suited for simulating random-access communications. It models the channel in blocks (so-called "drops"), during which the channel only undergoes Doppler fading, but after a drop, the channel changes completely. This assumption makes it impossible to test signal processing algorithms that track the channel parameters between different snapshots. Additionally, the abrupt changes between the drops are challenging for hardware testing using channel simulators, since the device under test and the channel model need to be synchronized. A major improvement is the WINNER II geometry-based stochastic channel model [15], which includes a smooth transition between drops. This smooth transition is only provided by the full implementation of the WINNER II model. The popular down-scaled version "clustered-delay line" does not provide the basis to track the channel! The COST 273 MIMO channel model [16, Chapter 6.8] does not use the concept of drops, but intrinsically models the channel in a smooth way. While the user is moving through a randomly-generated map, he is illuminated via groups of different propagation paths depending on his location on this map. When the receiver moves out of a certain region "visibility region", a particular group of paths fades out, and vice versa. Unfortunately, the COST 273 model is not yet completely parametrised, nor fully implemented.
1.1. Contribution
In this paper, we present the novel Random-Cluster Model (RCM), a geometry-based stochastic MIMO channel model for time-variant frequency-selective channels. The application of the RCM focuses on algorithm and system testing, yet it is parametrised directly from measurements.
The Random-Cluster Model uses multipath clusters to model the radio channel. Generally, multipath clusters can be seen as groups of propagation paths having similar parameters. We concisely define a cluster by its mathematical description provided in Section 2.2. Clusters allow to characterise the propagation environment in a compact way using much less parameters than characterisation by individual multipath components (MPCs). This data reduction is the primary purpose for using clusters in radio channel models. Clusters were first only observed in delay domain by Saleh and Valenzuela [17]. Their concept was extended to the joint angle-of-arrival/delay domain in [18]. Recently [19] developed a test to prove the existence or non-existence of clusters in propagation path estimates from channel measurements, showing that clusters indeed exist independent of the authors' view. We were able to match clusters to real-world scattering objects [20].
Several innovations were necessary to construct the RCM, some of which have been introduced in conference papers. First, to accurately parametrise the RCM, automatic clustering techniques are necessary. The first semiautomatic approach for clustering MIMO channel data was introduced in [21]. We gradually extended these ideas by a meaningful joint clustering approach [22], a power-weighted clustering algorithm [23], a criterion to decide on the number of clusters, a reasonable initial guess, and the ability to track clusters over multiple time-variant snapshots [24]. The mere fact that clusters can be tracked demonstrates that clustering makes sense showing that they obviously stem from scattering objects. The automatic parametrisation by identifying clusters without user intervention turned out to be essential to process a large amount of multiantenna measurement data.
Regarding the ability to describe time-variant channels, the RCM is capable to model random-access channels, and, in addition, to cover continuous transmission in a time-variant environment as well by creating smoothly time-variant channel realisations. A major innovation of the RCM is the concept of linearly moving clusters. In this article, we will use the RCM to model smoothly time-variant channels. (A first description of the RCM, modelling random-access channels only was provided in [25], and [26] briefly outlines the ideas of using clusters for time-variant channel modelling.)
The RCM is a stochastic MIMO channel model, yet it is parametrised directly from measurements. By double-directional MIMO channel measurements in a specific environment, a single multivariate pdf of the cluster parameters is created, which is representative for the electromagnetic wave propagation in this environment. The parameters of a single realisation are drawn from this distribution. In this way, the RCM is a stochastic channel model, deriving its parameters directly from measurements.
The complexity of the RCM should be divided into (i) the parametrisation complexity and (ii) the execution complexity. Regarding the parametrisation complexity, the RCM is parametrised automatically from measurements, even if the number of parameters appears to be high. The execution complexity of the RCM is governed by the calculation of the channel matrix, as in all other prominent physical channel models [27]. It adds up to real operations, where denotes the number of MPCs, and denote the number of transmit and receive antennas, respectively, and denotes the number of frequency samples, for which the channel matrix is calculated.
The ultimate challenge for any channel model is its comparison to measurements. We will describe the extensive validation of the RCM against measurements using three different validation metrics: (i) mutual information [2], (ii) channel diversity [28], and (iii) the novel Environment Characterisation Metric [29]. We find that the RCM is able to reflect the measured time-variant environment noticeably well. Additionally, we will demonstrate why the popular mutual information "capacity" is a poor validation metric for time variant MIMO channel models.
1.2. Organisation
This article is organised as follows. Section 2 provides a first overview of the features of the Random Cluster Model. Section 2.1 outlines the structure of the RCM, Section 2.2 details the description of the environment by multipath clusters. The initialisation of the model is provided in Section 2.3, and details on the implementation of the time variance are given in Section 2.4. Section 3 describes the model validation by first outlining the validation framework. We then introduce the validation metrics used in Section 3.2, followed by the validation results in Section 3.3. Finally, Section 4 concludes the article. In Appendix , we provide an overview of the measurements used for parametrisation and validation.
2. The Random-Cluster Model
The RCM is based on the concept of multipath clusters. The most significant feature of the RCM is that it is parametrised directly from channel measurements by an automatic procedure. In this way, the RCM is specific to the environment; it closes the gap between channel measurements and channel modelling. Nonetheless it is a stochastic model as we will clarify shortly.
The novel approach of the RCM is to describe the time-variant geometry of the channel completely by statistical cluster parameters. Clusters provide a compact way of describing the underlying propagation environment. To accurately parametrise the clusters, we extract their parameters from measurements. An important feature of the MIMO channel also reflected by the model is the coupling between propagation paths in space and time, also known as the double-directional MIMO channel model [30]. To enable time-variance, clusters may move, relative to the Tx or Rx. By this, the RCM creates correlated snapshots in time of the propagation environment.
- (i)
- (ii)
propagation-based, but stochastic,
- (iii)
- (iv)
What the RCM Provides
The main focus of the RCM is link-level simulation, for both algorithm testing and device testing. It is well suited to reflect time-variant scenarios that are similar, but not equal to the ones measured before. A major feature is that the parametrisation of the RCM, directly derived from measurements, is achieved automatically. In this way it perfectly fills the gap between channel sounding and channel simulation. Typical applications include testing in specifically challenging channel situations, or in specific application scenarios.
In contrast to "playback simulations" [31] where previously recorded impulse response data from a channel sounder are used to directly model the environment, the RCM is neither fixed in bandwidth, antenna array parameters, or simulation duration.
What the RCM Does Not Provide
By the way it is parametrised, the RCM is very specific in reflecting a certain type of environment. Being rooted in the COST 273 model [16, Chapter 6.8], one might think that the RCM is an all-purpose model. The model user will be warned that it does not perform like this. Many aspects that make a model very general have been intentionally omitted in the RCM in order to reduce complexity, for example, a dedicated path loss calculation, or a description of general environments.
For scenarios close to the measured ones, the RCM will still perform better than other (even standardised) models available, but proper parametrisation is always necessary.
The RCM is definitely not intended for supporting MIMO deployment. Since the model does not include any geometry, it is not suited for predicting the properties of the electromagnetic field in specific locations on a map, particularly not in environments that were not measured before.
2.1. General Model Structure
- (1)
During initialisation, a first snapshot of the scenario is generated from the environment parameter function.
- (2)
The implementation of the smooth time variation is split in two parts: (i) moving the clusters introduces small-scale changes to the environment and generates the Doppler-induced fading; (ii) the birth/death-process accounts for shadowing and large-scale changes.
Both of these parts rely on an accurate parametrisation of the environment. In the next paragraphs we will first detail how the environment is described. Subsequently we will explain the model flow step by step.
2.2. Environment Description—Multipath Clusters
Cluster parameters of a single cluster, contained in .
Cluster parameter
Cluster mean delay
Azimuth cluster position at Tx
Azimuth cluster position at Rx
Elevation cluster position at Tx
Elevation cluster position at Rx
Cluster delay spread
Cluster azimuth spreads seen from Tx
Cluster azimuth spreads seen from Rx
Cluster elevation spreads seen from Tx
Cluster elevation spreads seen from Rx
Cluster mean power
Total snapshot power, in which the cluster occurs
Number of clusters coexisting in the snapshot
Number of paths within a cluster
Change rate of cluster power per travelled wavelength in dB
Change rate of cluster mean delay per travelled wavelength
Change rate of cluster mean AOA per travelled wavelength
Change rate of cluster mean AOD per travelled wavelength
Change rate of cluster mean EOA per travelled wavelength
Change rate of cluster mean EOD per travelled wavelength
Cluster lifetime
A time-variant environment may contain transitions between different propagation conditions, for example, from LOS to NLOS and back. Clusters in these propagation conditions have quite different properties. Different propagation conditions are mainly reflected by two simple parameters: the snapshot power and the number of clusters. These two parameters are included in the set of cluster parameters, being cluster selection parameters. They label clusters for specific propagation conditions in a statistical way.
2.2.1. Geometrical Interpretation
A straight-forward extension of a MIMO channel description by single, discrete MPCs, is the usage of multipath clusters.
This leads to a significant reduction in the number of parameters. One cluster describing a manifold of multipath components showing similar propagation parameters is described by only 21 parameters (see Table 1), while a single MPC already needs 12 parameters (such seemingly large numbers of parameters are necessary for a time-variant description of clusters and propagation paths).
When we look at a cluster that stems from multiple bounces of an electromagnetic wave on its way from Tx to Rx, Figure 2 shows how a cluster appears when perceived from Tx and Rx separately. The cluster splits up in two parts. For single-bounce scattering, these two parts of a cluster overlap physically. For a direct path (line-of-sight), the cluster contains only a strong, single path. From the cluster parameters, one cannot deduct whether the cluster stems from single or from multiple-bounces scattering. From a modelling perspective concentrating on clusters, however, this knowledge is redundant (the same applies to MIMO modelling by multipath components). Note that we are using multiple clusters to describe the multipath structure of the radio channel, but Figure 2 shows just one cluster.
2.2.2. Environment pdf
The environment pdf characterises the multipath structure in a specific measured environment. In this way, the environment is completely parametrised by a description that is purely statistical. In some cases, this multivariate distribution may be multimodal and does not necessarily follow a simple closed-form distribution.
2.2.3. Parametrisation
- (1)
MIMO channel measurements provide multiple impulse responses of the scenario. While the channel sounder continuously records frequency-selective MIMO channel matrices at each time instant "snapshots", the transmitter is moved to capture the time-variant properties of the scenario.
- (2)
Propagation paths are estimated from each snapshot of the channel measurements using a high-resolution parameter estimation. For this purpose we used the Initialization-and-Search-Improved SAGE (ISIS) estimator [32] to estimate paths from every measured snapshot.
- (3)We identify and track clusters in these propagation paths using the fully automatic framework presented in [24]. This framework has the following key features.
- (a)
The initial guess algorithm identifies the cluster locations by separating clusters as far as possible in the parameter space while taking already existing clusters from previous snapshots into account. The number of clusters is estimated by a power-threshold criterion.
- (b)
The clustering is optimized using the KPowerMeans algorithm [23], which makes clusters as compact as possible. This is achieved by including the concept of path power into the classic KMeans algorithm and by enabling joint clustering by appropriate scaling of the input data.
- (c)
Clusters are tracked using a Kalman filter between snapshots, where a probabilistic cluster fitting criterion decides whether a cluster has actually moved or has to be regarded as new.
- (a)
- (1)
We estimate the environment pdf from all identified clusters using a kernel density estimator (KDE) [34].
where and denote the mean and covariance of the th kernel, and denotes the number of kernels used.
where denotes the dimension of the cluster parameter vector. We used Gaussian kernels for their low complexity and analytical tractability. Furthermore, Gaussian kernels manage to describe all kinds of (continuous) pdfs with low error [35].
The kernel parameters and need to be estimated. The input data for this estimation are the identified clusters from a measurement route.
A straight-forward way to find the kernel parameters is to choose the equal to the total number of identified clusters. Each individual identified cluster is used as (mean) parameter for an individual kernel. The variances of the kernel can then be estimated using the minimum average mean integrated squared error (AMISE) criterion [35]. This parametrisation approach is the most accurate one, although the number of kernels may become quite large.
Of course, the obtained environment pdf is very specific to the measured environment since it is directly parametrised from measurements.
It becomes obvious that the environment pdf is indeed a multimodal distribution, strongly depending on which parameters are observed. For example, Figure 3(a) demonstrates that clusters with large mean delay usually have weaker power, which was to be expected. Additionally, Figure 3(b) details from which Rx directions clusters with stronger power appear. Some of the cluster parameters are even intrinsically correlated. For instance, Figures 3(c)-3(d) show that there is a correlation between the cluster azimuth spreads. Additional values of the environment pdf can be found in [33, 36].
2.3. RCM Initialisation
The initialisation procedure generates the first snapshot of the model.
2.3.1. Drawing Initial Cluster Parameters
The environment pdf provides a description for all kinds of clusters that were identified in the environment. To actually generate a snapshot, the momentary propagation condition of the environment must be selected. This is done by determining the intended snapshot power and the number of clusters (which are the cluster selection parameters). Their joint distribution function is contained in the environment pdf.
- (i)
First, we obtain the pdf of the number of clusters, , by marginalizing the environment pdf to the number of clusters, which is done by integrating the environment pdf over the other dimensions. Then the actual number of clusters for the first snapshot, , is determined by drawing a random sample from this pdf. Since the number of clusters must be an integer number, the ceiling of the drawn value is assigned to .
- (ii)
Then, we obtain the pdf of the snapshot power (given the number of clusters) by conditioning the environment pdf on the chosen number of clusters , and marginalising it to the snapshot power. From this marginal distribution , the intended snapshot power, , is determined by drawing a random sample from this pdf. This intended snapshot is only used as a selection criterion for the clusters to be drawn in the next steps. In general, the sum power of the clusters will not exactly match the intended snapshot power.
- (iii)
Finally, to select a specific type of clusters, the environment pdf is conditioned on both the number of clusters and on the intended snapshot power, . From this final distribution, we draw cluster parameter sets .
These parameters are drawn from a multivariate sum-of-Gaussian distribution, which sometimes leads to invalid parameters because of the Gaussian tails. For this reason, the drawn spread parameters and the mean delay are lower-bounded by zero, the number of paths within a cluster is rounded to the next larger integer and lower bounded by one, and the drawn cluster lifetime is rounded to the closest integer value larger or equal to one. In this way, we can retain the low-complexity kernel density estimation but still create valid cluster parameters for the model.
These (post-processed) cluster parameters specify the multipath structure of the initial snapshot.
2.3.2. Placing Multipath Components within the Clusters
- (1)
In every cluster , the corresponding number of paths (which is an initial cluster parameter drawn before), , is placed as follows. Every path is described by the path parameters: complex amplitude ( , total delay ( , and the azimuth and elevation of arrival and departure, respectively, ( .
The delay is drawn from a Gaussian distribution with its mean and variance given in the cluster parameters. Similarly, the angular parameters are drawn from a wrapped Gaussian distribution [37] (in the wrapped Gaussian distribution, all realisations are mapped to their principal value in ), where the mean and variance are again determined in the cluster parameters (Table 1). All paths within a cluster show the same amplitude, , determined by the total cluster power and the number of paths within a cluster, and have a random phase, which is drawn from a uniform distribution .
After having placed paths in all clusters, the propagation environment of the initial snapshot is completely specified by its multipath structure.
2.3.3. Generating the MIMO Channel Matrix "System Model"
To calculate the MIMO channel matrix, we use the common approach of a bandwidth filter and antenna filters [38].
at a certain frequency bin equidistantly spaced on a limited bandwidth between , where denotes the carrier frequency and the simulated bandwidth. The antenna array patterns are described in , and the subset denotes the th path in cluster . This calculation dominates the computational complexity of the model (a low-complexity implementation of this equation is also available in [39]).
For the exemplary implementation of the RCM that we validated (see Section 3), we imply an MIMO configuration with uniform linear arrays at both link ends, a bandwidth of 20 MHz, and 32 frequency bins. The centre frequency was set to either 2.55 GHz or to 5.25 GHz matching the measurement. An configuration provides a much tougher test whether a model renders the spatial environment properties correctly than the or configurations envisaged for LTE. By including the actual antenna array pattern, the RCM can easily be extended to arbitrary array configurations other than ULAs.
2.4. Implementation of the Time Variation
After the generation of the initial snapshot, the RCM generates channels correlated in time. The implementation of the time variation, based on the novel idea of linearly moving clusters, is an integral part of the model. In this way, both stationary and nonstationary time-variant channels can be modelled.
2.4.1. Time Bases
We distinguish between small-scale and large-scale time variations. Small-scale variations, which introduce fading, take place every sampling instant. Large-scale variations, reflecting changes in the propagation structure, occur in less frequent intervals.
For this reason, the RCM distinguishes between two time bases: the sampling time interval, , and the cluster-lifetime interval, , where . Cluster lifetimes, , are multiples of (see Table 1).
2.4.2. Large-Scale Variation—Cluster Birth/Death Process
In time-variant scenarios, where at least one of the transceivers is moving, the propagation conditions can change significantly. To introduce these large-scale changes into the model, we included a cluster birth/death process.
This birth/death process is motivated from observations in measurements, where clusters smoothly show up, exist over a period of time, and eventually fade away. We reflect this behaviour in our model by three parameters: (i) the cluster lifetime, responsible for the cluster death, (ii) a cluster birth pdf, and (iii) a fade-in/fade-out coefficient.
The lifetime of each cluster is already intrinsically defined in the cluster parameters (see Table 1), which was drawn from the environment pdf when the cluster was created. Cluster death is implemented by decreasing the lifetime of each cluster in every cluster lifetime interval, . Dying clusters are fading out during the next cluster lifetime interval.
An additional probability mass function (pmf), describing the number of cluster births per cluster lifetime interval, is also extracted from the measurements. The extraction method and examples of extracted parameters are provided in [33]. According to this pmf, a number of new clusters are drawn every cluster lifetime interval. After drawing the number of new clusters, the actual parameters of these new clusters are drawn in the same way as described in the initialisation procedure in Section 2.3.1. New-born clusters fade in during the next cluster lifetime interval.
The appearance or disappearance of clusters is done exponentially in the small-scale updates, controlled by the cluster fade-in/fade-out coefficient . Empirical evaluations showed that a maximum cluster attenuation of 10 dB provides best results, hence .
Note that our approach is different from using "visibility regions" [40], which cannot be used since we do not consider the actual geometry of the environment.
2.4.3. Small-Scale Variation—Cluster Movement
The RCM models small-scale changes by the movement of the clusters in parameter space. In every sampling time interval, the parameters of the paths within a cluster are linearly incremented. These increments are provided in the cluster parameters of the respective cluster (see Table 1).
In this way, clusters are moving in delay (causing Doppler shifts) and in angles, and they smoothly change their power. The speed is a scalar defining how fast clusters move. The "direction" of movement is defined by the cluster movement parameters.
These small-scale changes intrinsically introduce correlated fading. This repeated update inherently creates a Doppler spectrum, where each individual path contributes with its Doppler shift (equal for all paths within a cluster). Of course, linear movement is just a first-order approximation of the true movement of clusters, a more complex method can be found in [41]. However, the model validation will show that modelling movements linearly is sufficient to accurately reflecting the time-variant propagation environment.
3. Model Validation
Validation is paramount, it scrutinises whether a model reflects important properties of the propagation channel. Particularly for MIMO channels, models need to reflect the spatial structure of the channel correctly.
We validated the RCM against MIMO channel measurements carried out with an Elektrobit Propsound CS wideband channel sounder at two centre frequencies of 2.55 GHz and 5.25 GHz. Details about the measurements and the validated scenarios are presented in Appendix . For validation we will use three different validation metrics reflecting the spatial structure of the channels.
3.1. Validation Framework
- (1)
Perform radio channel measurements in representative scenarios and estimate propagation paths [32] from the measurements for every snapshot of the channel.
- (2)
Parametrise the RCM (see Section 2.2.3).
- (3)
Generate reference channels by applying the system model (see Section 2.3.3) to the estimated paths parameters.
- (4)
Generate smoothly time-variant modelled channels by invoking the RCM.
- (5)
Compare the modelled channels with the reference channels according to the cdf of different validation metrics.
3.2. Validation Metrics
Before detailing the validation results, we present the different validation metrics. We concentrate on the validation of the spatial properties of the modelled channels.
3.2.1. Mutual Information
For the purpose of comparison with literature we take mutual information (MI) for model validation [42, 43]. (Quite frequently the term "capacity" is misused for mutual information.) However, we will show later in this section that MI has an intrinsic disadvantage, which disqualifies it as a good metric for validating the double-directional multipath structure of a time-varying channel.
where denotes the number of frequencies. Then, the validation metric reflects the spatial structure of the channel best. We chose an SNR of 10 dB for the following validation evaluations. For creating a cdf, we use all time realisations and frequencies as our ensemble of samples.
The deficiencies of MI as a validation metric will now be demonstrated by a meaningful example. This example will also highlight the difference between average MI and ergodic capacity.
Figure 5(b) shows the cdf of the so-computed MI. The MI varies considerably, even though the spatial structure of the channel remains the same. The reason for this effect is the fading created by randomly changing the phases of the paths. One can see that mutual information fails to reflect the spatial structure of a single realisation of an environment. A validation metric reflecting the spatial structure should provide one unique result, and not a wide-spread distribution. For this reason, MI is not suited to assess whether a channel model provides a correct spatial representation of the scenario or not.
As the spatial structure determines which gains the channel offers, the RCM strives to reflect the spatial structure as accurately as possible. Thus, also the validation metric should be specific to the spatial structure. Nevertheless, as MI is frequently used for validating MIMO channel models, we will also use MI in this paper, for reasons of comparison, but point out its deficiencies in the results.
3.2.2. Environment Characterisation Metric
The Environment Characterisation Metric (ECM) [29] is directly applied to the path parameters rather than to the channel matrix. This section shortly describes the significance of the ECM. For better readability, we will (i) enumerate all paths in each time instant from , disregarding cluster structures for the time being, and (ii) skip the time index in the following derivations whenever it is redundant.
and by its power . When considering only azimuthal propagation, the -direction must be excluded. (Since the elevation estimation from our data was not trustworthy, we excluded elevation in the validation.)
with the mean parameter vector given as .
- (i)
The metric is system independent as it is calculated from the propagation paths directly. Additionally, the metric is independent of the phases of the propagation paths.
- (ii)
The main diagonal contains the directional spreads (comparable to the azimuth and elevation spreads) at Rx and Tx, and the (normalized) rms delay spread. In this way, the ECM jointly represents the spatial structure, and wideband properties of the channel.
- (iii)
The trace is the sum of the directional spreads [46] at Rx and Tx plus the (normalized) delay spread.
- (iv)
The determinant describes the volume spanned in the parameter space.
- (1)
Validating the spatio-temporal multipath structure: the singular values of the ECM (SV-ECM) can be interpreted as the fingerprint of the scenario, by which one can judge the compactness of the paths in the channel. Assuming that the parameters of all paths span a multidimensional ellipsoid, the SVs describe the lengths of the main axes of this ellipsoid. In this way, it transforms the traditional view of individual parameter spread values into a joint-spread approach. These properties make the SV-ECM genuinely suited for comparing channels. Calculating the SV-ECM for the example shown in Figure 5(a), the snapshot would result in the same values of the SV-ECM, no matter which phases the paths have. This demonstrates that the SV-ECM is a consistent metric, reflecting the multipath structure of the channel.
- (2)Validating the time-variance: the rate of change of the ECM shows how strongly the parametric channel changes between two neighbouring time instants. To quantify the rate of change between two ECM matrices of adjacent snapshots, we use the Frobenius inner matrix product [47] as
where denotes the matrix trace operator, and denotes the Frobenius matrix norm. The Frobenius inner product quantifies how similar the eigenvectors of the two matrix arguments are. For collinear matrices, we have , while for orthogonal matrices, .
3.2.3. Diversity Measure
Spatial diversity describes the number of independent fading links between the Tx and Rx antenna arrays. In a full-diversity system, where all links between the Tx and Rx arrays are independent, one observes a spatial diversity of [48]. This diversity is directly linked with the uncoded bit-error ratio (BER) performance of MIMO systems [1].
Channel correlation reduces this diversity significantly. Ivrlac and Nossek provided the Diversity Measure [28], a way to quantify the available diversity directly from the MIMO channels without taking the detour via BER simulations. We will use this measure to quantify the diversity in both the measured and the modelled channels, and subsequently compare the results.
with defined in (4). These estimated correlation matrices for all time instants are taken as ensemble to obtain the cdf of (13).
3.3. Validation Results
This paper presents validation results for two particularly interesting scenarios, (i) a measurement route in an office scenario, without line of sight between transmitter and receiver, and (ii) a route within a cafeteria (large room) mostly with LOS between transmitter and receiver (see Figure 11 in Appendix ). The Tx was moved through the rooms while the Rx was placed at a fixed position. The cafeteria scenario is a particularly challenging one, difficult to represent by any MIMO channel model, as it is a combination of two totally different propagation environments, depending on whether the LOS between Rx and Tx is blocked or not. For validation we generated smoothly-time varying channels using the RCM and used the three validation metrics described in the previous paragraphs. The validation of more scenarios can be found in [36, Chapter 4].
In the NLOS office scenario, where the SNR of the measurement was only average, we observe that the model has a slightly lower number of small changes than the reference channels (rightmost part of Figure 7(a)). This is due to the path parameter estimation algorithm, which always estimates a number of outlier paths that appear at random in any single time snapshot. In the cafeteria scenario, we observe much stronger changes than in the office scenario due to the changes in the LOS part of the environment. The measurement SNR was high, so random outliers were no problem, as the rightmost part of the curves show. Between the outage probabilities of and , the model fits the measurement very well, which is the statistically relevant part. The few much larger changes that are observed in the measurements occur during the abrupt transition from LOS to NLOS.
4. Conclusions
The presented Random-Cluster Model is well able to reflect the spatial properties of measured time-variant MIMO channels, even if the properties of the environment are varying between LOS and NLOS. By its direct parametrisation from measurement data, the RCM is specific to the measured environment. Since the RCM is propagation-based, the RCM is also scalable in carrier frequency, in bandwidth, and in its antenna array configuration. Still, it is a stochastic model. The propagation environment is described using a multivariate pdf of the cluster parameters. Depending on the accuracy of the estimation of this pdf from measurements, the parametrisation complexity is scalable. Time variance is implemented by linear cluster movement. Using the recommended clustering algorithm in combination with a Kernel Density Estimator, the RCM is parametrised automatically without user interaction.
Validation showed a close fit between the channels modelled by the RCM, and reference channels obtained from the measurements. Even though the RCM was only successfully validated against indoor measurements, the model structure is also well suited to represent outdoor radio channels, when adapting the parameters, respectively. This renders the RCM to be ideally suited to model particularly interesting propagation conditions that were measured before.
This work was partly carried out in the frameworks of the European Projects NEWCOM, COST 273, and COST 2100. The authors thank Elektrobit for partly funding the Ph.D. work of N. Czink and for providing the measurement equipment. The authors gratefully acknowledge the help of Veli-Matti Holappa and Mikko Alatossava during the measurement campaign. The Telecommunications Research Center Vienna (ftw.) is supported by the Austrian Government and the City of Vienna within the competence centre programme COMET.
Authors' Affiliations
- Paulraj AJ, Gore DA, Nabar RU, Bölcskei H: An overview of MIMO communications—a key to gigabit wireless. Proceedings of the IEEE 2004, 92(2):198-218. 10.1109/JPROC.2003.821915View ArticleGoogle Scholar
- Telatar IE: Capacity of multi-antenna Gaussian channels. AT&T Bell Laboratories, Murray Hill, NJ, USA; 1995.Google Scholar
- http://www.beceem.com
- http://www.linksys.com
- 3GPP—The 3rd Generation Partnership Project 2008, http://www.3gpp.org
- IEEE 802.16 working group on broadband wireless access standards 2008, http://wirelessman.org
- Shiu D-S, Foschini GJ, Gans MJ, Kahn JM: Fading correlation and its effect on the capacity of multielement antenna systems. IEEE Transactions on Communications 2000, 48(3):502-513. 10.1109/26.837052View ArticleGoogle Scholar
- Weichselberger W, Herdin M, Özcelik H, Bonek E: A stochastic MIMO channel model with joint correlation of both link ends. IEEE Transactions on Wireless Communications 2006, 5(1):90-100.View ArticleGoogle Scholar
- Edelman A, Rao NR: Random matrix theory. Acta Numerica 2005, 14: 233-297.MathSciNetView ArticleMATHGoogle Scholar
- Wood LC, Hodgkiss WS: MIMO channel models and performance metrics. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '07), November 2007, Washington, DC, USA 3740-3744.Google Scholar
- Wyne S, Molisch AF, Almers P, Eriksson G, Karedal J, Tufvesson F: Outdoor-to-indoor office MIMO measurements and analysis at 5.2 GHz. IEEE Transactions on Vehicular Technology 2008, 57(3):1374-1386.View ArticleGoogle Scholar
- Fügen T, Maurer J, Kuhnert C, Wiesbeck W: A modelling approach for multiuser MIMO systems including spatially-colored interference. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '04), November-December 2004, Dallas, Tex, USA 2: 938-942.View ArticleGoogle Scholar
- Degli-Esposti V, Guiducci D, de'Marsi A, Azzi P, Fuschini F: An advanced field prediction model including diffuse scattering. IEEE Transactions on Antennas and Propagation 2004, 52(7):1717-1728. 10.1109/TAP.2004.831299View ArticleGoogle Scholar
- Spatial channel model for Multiple Input Multiple Output (MIMO) simulations 3GPP, Valbonne, France; 2003.Google Scholar
- Kyösti P, Meinilä J, Hentilä L, et al.: WINNER II channel models (d1.1.2v1.1). November 2007, http://www.ist-winner.org
- Correia L (Ed): Mobile Broadband Multimedia Networks. Academic Press, San Diego, Calif, USA; 2006.Google Scholar
- Saleh A, Valenzuela R: A statistical model for indoor multipath propagation. IEEE Journal on Selected Areas in Communications 1987, 5(2):128-137.View ArticleGoogle Scholar
- Spencer QH, Jeffs BD, Jensen MA, Swindlehurst AL: Modeling the statistical time and angle of arrival characteristics of an indoor multipath channel. IEEE Journal on Selected Areas in Communications 2000, 18(3):347-360. 10.1109/49.840194View ArticleGoogle Scholar
- Xiao H, Burr AG, Hentilä L, Kyösti P: Statistical technique to identify clusters from multi-dimensional measurement data. Proceedings of the 2nd European Conference on Antennas and Propagation (EuCAP '07), November 2007, Edinburgh, UK 1-7.Google Scholar
- Galdo GD, Czink N, Haardt M: Cluster spatial localization from high-resolution parameter estimation. Proceedings of IEEE/ITG Workshop on Smart Antennas (WSA '06), March 2006, Ulm, Germany 1-7.Google Scholar
- Salo J, Salmi J, Czink N, Vainikainen P: Automatic clustering of nonstationary MIMO channel parameter estimates. Proceedings of the 2nd International Conference on Telecommunications (ICT '05), May 2005, Cape Town, South AfricaGoogle Scholar
- Czink N, Cera P, Salo J, Bonek E, Nuutinen J-P, Ylitalo J: Improving clustering performance using multipath component distance. Electronics Letters 2006, 42(1):33-35. 10.1049/el:20063917View ArticleGoogle Scholar
- Czink N, Cera P, Salo J, Bonek E, Nuutinen J-P, Ylitalo J: A framework for automatic clustering of parametric MIMO channel data including path powers. Proceedings of IEEE Vehicular Technology Conference (VTC '06), September 2006, Montreal, Canada 114-118.Google Scholar
- Czink N, Tian R, Wyne S, et al.: Tracking time-variant cluster parameters in MIMO channel measurements. Proceedings of the 2nd International Conference on Communications and Networking in China (ChinaCom '07), August 2007, Shanghai, China 1147-1151.Google Scholar
- Czink N, Bonek E, Hentilä L, Nuutinen J-P, Ylitalo J: A measurement-based random-cluster MIMO channel model. Proceedings of IEEE Antennas and Propagation International Symposium, June 2007, Honolulu, Hawaii, USA 5363-5366.Google Scholar
- Czink N, Bonek E, Ylitalo J, Zemen T: Measurement-based time-variant MIMO channel modelling using clusters. Proceedings of the 29th General Assembly of the International Union of Radio Science (URSI '08), August 2008, Chicago, Ill, USAGoogle Scholar
- Kyösti P, Jämsä T: Complexity comparison of MIMO channel modelling methods. Proceedings of the 4th IEEE Internatilonal Symposium on Wireless Communication Systems (ISWCS '07), October 2007, Trondheim, Norway 219-223.Google Scholar
- Ivrlac MT, Nossek JA: Quantifying diversity and correlation in Rayleigh fading MIMO communication systems. Proceedings of the 3rd IEEE International Symposium on Signal Processing and Information Technology (ISSPIT '03), December 2003, Darmstadt, Germany 158-161.Google Scholar
- Czink N, Galdo GD, Yin X, Bonek E, Ylitalo J: A novel environment characterization metric for clustered MIMO channels: used to validate a SAGE parameter estimator. Wireless Personal Communications 2008, 46(1):83-98. 10.1007/s11277-007-9357-1View ArticleGoogle Scholar
- Steinbauer M, Molisch AF, Bonek E: The double-directional radio channel. IEEE Antennas and Propagation Magazine 2001, 43(4):51-63. 10.1109/74.951559View ArticleGoogle Scholar
- Kolu J, Nuutinen J-P, Jämsä T, Ylitalo J, KyÖsti P: Playback simulations of measured MIMO radio channels. In COST 273, TD(04)110. COST, Gothenburg, Sweden; June 2004.Google Scholar
- Fleury BH, Tschudin M, Heddergott R, Dahlhaus D, Pedersen KI: Channel parameter estimation in mobile radio environments using the SAGE algorithm. IEEE Journal on Selected Areas in Communications 1999, 17(3):434-450. 10.1109/49.753729View ArticleGoogle Scholar
- Czink N, Tian R, Wyne S, et al.: Cluster parameters for time-variant MIMO channel models. Proceedings of the 2nd European Conference on Antennas and Propagation (EuCAP '07), November 2007, Edinburgh, UK 1-8.Google Scholar
- Ihler A: Kernel Density Estimation Toolbox for MATLAB (R13). July 2007, http://ttic.uchicago.edu/~ihler/code
- Scott DW: Multivariate Density Estimation. John Wiley & Sons, New York, NY, USA; 1992.View ArticleMATHGoogle Scholar
- Czink N: The random-cluster model—a stochastic MIMO channel model for broadband wireless communication systems of the 3rd generation and beyond, Ph.D. dissertation. Technische Universität Wien, Vienna, Austria; FTW Dissertation Series, December 2007Google Scholar
- Mardia KV, Jupp PE: Directional Statistics. John Wiley & Sons, New York, NY, USA; 2000.MATHGoogle Scholar
- Almers P, Bonek E, Burr A, et al.: Survey of channel and radio propagation models for wireless MIMO systems. EURASIP Journal on Wireless Communications and Networking 2007, 2007:-19.Google Scholar
- Kaltenberger F, Zemen T, Üeberhuber CW: Low-complexity geometry-based MIMO channel simulation. EURASIP Journal on Advances in Signal Processing 2007, 2007:-17.Google Scholar
- Asplund H, Glazunov AA, Molisch AF, Pedersen KI, Steinbauer M: The COST 259 directional channel model—part II: macrocells. IEEE Transactions on Wireless Communications 2006, 5(12):3434-3450.View ArticleGoogle Scholar
- Wallace JW, Jensen MA: Time-varying MIMO channels: measurement, analysis, and modeling. IEEE Transactions on Antennas and Propagation 2006, 54(11):3265-3273.View ArticleGoogle Scholar
- Erceg V, Schumacher L, Kyritsi P, et al.: TGn channel models. IEEE P802.11, Geneva, Switzerland; 2004.http://grouper.ieee.org/groups/802/11/Google Scholar
- Kyösti P, Laselva D, Hentilä L, Jämsä T: Validating IST-WINNER indoor MIMO radio channel model. IST Mobile and Wireless Summit, June 2006, Mykonos, GreeceGoogle Scholar
- Molisch AF, Steinbauer M, Toeltsch M, Bonek E, Thomä RS: Capacity of MIMO systems based on measured wireless channels. IEEE Journal on Selected Areas in Communications 2002, 20(3):561-569. 10.1109/49.995515View ArticleGoogle Scholar
- Steinbauer M, Özcelik H, Hofstetter H, Mecklenbräuker CF, Bonek E: How to quantify multipath separation. IEICE Transactions on Electronics 2002, E85-C(3):552-557.Google Scholar
- Fleury BH: First- and second-order characterization of direction dispersion and space selectivity in the radio channel. IEEE Transactions on Information Theory 2000, 46(6):2027-2044. 10.1109/18.868476View ArticleMATHGoogle Scholar
- Golub G, van Loan C: Matrix Computations. 3rd edition. The Johns Hopkins University Press, London, UK; 1996.MATHGoogle Scholar
- Oestges C, Clerckx B: MIMO Wireless Communications. Academic Press, London, UK; 2007.MATHGoogle Scholar
- Elektrobit EB Propsim 2008, http://www.propsim.com
- Hentilä L, Kyösti P, Ylitalo J, Zhao X, Meinilä J, Nuutinen J-P: Experimental characterization of multi-dimensional parameters at 2.45 and 5.25 GHz indoor channels. Proceedings of the Wireless Personal Multimedia Communications (WPMC '05), September 2005, Aalborg, Denmark 254-258.Google Scholar
- Fleury BH, Jourdan P, Stucki A: High-resolution channel parameter estimation for MIMO applicationsusing the SAGE algorithm. Proceedings of the International Zurich Seminar on Broadband Communications, February 2002, Zurich, Switzerland 1-9.Google Scholar
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


text:
The brahmin Māgandiya asked the Buddha about how to find inner peace:
Mental purity is neither caused by particular views, nor by learning, nor by
knowledge, nor even by perfect morality. Neither by absence of right view,
missing learning, lack of knowledge, or tainted morality, not by that either!
Discarding all these oppositions, detached, calmed, independent, one stops
longing for any form of existence... Whoever thinks himself equal, superior,
or inferior, he will dispute on that account! But the imperturbable one does
not enter any self-deceit! Since for such one, there is no I-Me-Self or Ego
how much less can there then ever be any equal, inferior or superior I-Ego!
Leaving home, wandering homeless, not making acquaintances in any village,
free from desire for sensual pleasures, showing no preferences, such sage
will never engage in any controversy. One who really knows does not become
proud because of any particular view, learning, thought, or experience, for
he is not tied to, influenced by, or led by any of these momentary illusions..
He is completely released through his understanding. But those who cling to
certain experiences and particular views wander about causing controversy!
Sutta-Nipāta 839-842-844-846-847 Edited excerpt.
More on selfless impersonality, ego-lessness, the No-Self fact (Anattā):Ego-Projection, Who_or_what_is_the_Agent, Anatta No Self, The Egoless,
I-dentification, The Anatta Doctrine, No_Agent_is_Inside, We_Are_Not,
Empty_of_What, Neither_Agent_nor_Actor, Experiencing_Egolessness,
The_Smoke_of_Self, Input_'I'-dentification, No-Agent_but_Dependence,
Anti-EGO-Tool, Non-'I'-dentification, Uprooting_Egoism, Prison_of_Pride,
Mistaken_Reference, Solo_Self-Deception, Invisible_Impersonlatity,
Empty_of_What?, Who_is_the_Creator, Not_Who_but_What,
Self-less_Anatta, No_Being_No_Person, Deed_without_Doer.
Without Controversy!
Have a nice & noble day!
Friendship is the Greatest! Bhikkhu Samāhita _/\_ ]

subset: commoncrawl


text:
Today I am going to discuss about one of the easiest ways of making money online. In this post, I will show how you can one single website to make thousands of dollars. And to make that money you will need to put minimum of efforts. The website that we will use is very popular among the people; though most of them are not exploring it properly. Yes the website I am talking about is Reddit; better known as the front page of internet.
When I use this method, I make money almost instantly. The best day I had with this method when I made around $150. Whenever I tried this method, I could easily make $100 per day. I used to work for only 2 hours per day. You too can make similar amount of money or even more if you give it a try! I am going to start this case study right now to show you exactly I make money from Reddit.


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- Create a constituent query for the mailing. If creating envelopes for another function in Mail, such as Donor Acknowledgement Letters, mark the Create Constituent output query checkbox on the General tab to generate a query of the constituents in the mailing.
- On the General tab of the Envelopes mailing, click Include, Selected Records to search for and select the query created in step 1
If only soft credit recipients are missing, ensure the query includes soft credits.
If the issue still occurs, refer to How to troubleshoot missing or incorrect records in a mailing (labels, envelopes, Quick Letters, etc.).


text:
Recent Blog Posts
We're on Instagram!
Dated Posted: February 5th, 2015
Written By: Leila
Dated Posted: September 15th, 2014
Written By: Leila
We just got in a container full of gorgeous doors, iron, furniture and more! We're working on getting photos on our gallery page soon, but last time the nicest doors were selling before we could set them up, so do stop by!
Dated Posted: April 11th, 2014
Written By: Leila
We will be closed Friday, April 18th to Monday, April 21st. Have a safe & chocolatey long weekend, and happy spring!
Save the Doorknobs!
Dated Posted: January 18th, 2014
Written By: Leila
Have you heard about the motion to ban doorknobs from new construction in Ontario? You can read about it in this Toronto Star article. Although we completely understand the importance of accessibility in public/commercial buildings, do we really need to be told what kind of handles we have in our homes? We'd love to hear your feedback on this – 'Like' us on Facebook and leave a comment.
Glass Ornaments
Dated Posted: December 6th, 2013
Written By: Leila
These vintage-y glass ornaments make wonderful hostess gifts, and they're so lovely you might want to keep some for yourself! They include: a British phone booth, Big Ben, beefeater, Eiffel Tower, robot, igloo, glittery owl, goldfish, pink poodle and more! They always sell quickly, so come in soon for the best selection!


text: "Head up straight slave". Lady Bellatrix pours baked beans over the slave's head and they trickle down his face. Next we've got mushy peas. Generally served with fish and chips but today we are serving them with slave. Lady Bellatrix scrapes them over the slave's head. You look like a green alien took a shit on your head". Lady Bellatrix shovels the food mess over the slave's cock


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To support an upcoming streaming event I needed to create a gif. (Let's not digress into a debate on how to pronounce gif.) Denver Public Schools has a commitment box that is made available at all large culture-building events. Since this upcoming event will be solely online I came up with an idea to make a virtual commitment box to interact with.
First, I needed to create a gif showing someone dropping a commitment card into the box. I searched for gif creators that could do the job for free and with the least amount of hassle. I tried giphy.com, Imgflip and gifmaker.me with the latter winning out for ease of use. I shot a four photo sequence of my coworker, Anna, dropping a commitment card into the box. When I uploaded the images to gifmaker.me the interface was intuitive and simple. Although all I had to do was upload and reorder the images, there were multiple choices available to me: resizing, animation speed, repeats, and even the option to add music. In about a minute total working time, I had my gif downloaded.
My next task was to create the Google form and add it to the top. Google forms is becoming more and more open to customization. I chose a blank form, changed the color to match the card Anna holds in the animation and then uploaded the gif to the description area of the form. You can take a look at the finished product here:
I think this is going to work out pretty well for the event. What do you think? What is your favorite gif maker?
Tags: elearning, gif, Google Forms, graphics, streaming, Technology


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The Christmas season is upon us and the carols are being sung around the world and throughout the land. Today I am thankful that here in America we still have the freedom to worship the Lord Jesus with virtually no hindrances. Unlike many in other lands, we have been truly blessed with this freedom. My prayers go out to my brothers and sisters in the other lands who have to hide to read a passage of Scripture or pray. But thanks be to God He always hears the cries of His children. A silent prayer or a passage memorized can never be taken away from the heart. In America Christians have yet to be be tried through these fires. It is altogether possible that they may never be, simply because of the faith of the many faithful today and that of our forefathers who saw to it that the Lord would be the foundation upon which this land would be built.
It warms my heart when I look back into the past history of the United States. Even though humanity will never be perfect and many of those who graced the halls of Christianity were never perfect themselves we still have a heritage that we always strive to be what the Lord calls us to be. In the past, most every family has parents or grandparents who faithfully attended a worship assembly. The traditions are deep and the faith they fostered still rises warmly in the hearts of us who so treasure the examples of faith that they left for us to follow. God is so good. Surely He looks upon the heart and He knows those who are faithfully His.
During this coming Christmas season may the light of Christ burn brightly in our hearts and may its flame warm the hearts of those we come in contact with. God's call to His church is obedience. Listen to Him when He speaks and walk in humble obedience and the Glory of God will suround your life and your heart. Others too, will see Jesus. Remember His immortal words, "And I, if I am lifted up from the earth, will draw all peoples to Myself," (John 12:32).
May God richly bless you and yours during this hallowed time of the year!


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Princess Grace enjoyed playing this piano. We're proud to have this beautiful - and romantic - piece of history here at Breezes Bahamas for our guests to enjoy.
(PRWEB) January 28, 2014
The piano was on board the 298-ton 147-foot yacht (built in the 1920s) given to Prince Ranier and Princess Grace of Monaco as a wedding gift from Aristotle Onassis. In 1956, the royal couple honeymooned aboard the yacht along the coasts of Corsica and Sardinia. Princess Grace often played this piano for Prince Ranier and their guests aboard the yacht, which was christened Deo Juvente II.
In 1987, John Issa, owner and chairman of SuperClubs - the parent company of Breezes Bahamas - acquired the yacht along with the piano. Bearing the name M/Y Zein after one of Issa's daughters, the vessel was fully restored before taking up residence along the coast of Negril, Jamaica where it remained the official yacht of one of Issa's popular beach resorts for nearly twenty years.
"Princess Grace enjoyed playing this piano," said Muna Issa, vice president operations to SuperClubs. "We're proud to have this beautiful - and romantic - piece of history here at Breezes Bahamas for our guests to enjoy."
Guests of Breezes Bahamas can now view the piano, on display in the foyer of the brand new Banana Boat restaurant, which opened in early January 2014.
Breezes Bahamas Resort & Spa
Breezes Bahamas, the first and only Super-Inclusive resort in The Bahamas, sits on legendary Cable Beach where guests can sink their toes into the white sand under the Caribbean sun. The beachside resort boasts activities ranging from rock wall climbing, tennis, and beach volleyball to kayaking and windsurfing. Guests can also indulge in relaxing spa treatments at the à la carte Blue Mahoe Spa. At night, adults can enjoy a lively piano bar which stays open until the last person leaves, or they can take their chances at one of the many nearby casinos. For young adults, the resort prepares activities throughout the day and the evenings such as local Bahamian performances, games and more to keep them entertained. The resort welcomes singles, couples and families with children age 14 and older.
Breezes' "Super-Inclusive" concept offers the best vacation value. Make a single payment for accommodations, all meals, and multiple dining options including Continental, Italian, and authentic regional cuisine, unlimited premium brand drinks, myriad land and water sports including equipment and instruction, entertainment, weddings, recreational activities and hotel taxes. Gratuities are included.
SUGGESTED TWEET: Princess Grace's piano now on display @Breezes_Resorts. #romantichistory.
For more information or reservations, visit http://www.breezes.com, call 1-877-BREEZES (273-3937) or contact a local travel agent.


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Anyways, my quest for free music has yielded some astonishing results, and this album, or rather EP, is so far my favourite. It's in Russian, but who cares. The melodies are great and the vocals even better.
The sound is jazzy, and all tracks but number three are about sun and happiness, and all that good and yellow stuff.
Reminds me that I need some sort of auxiliary audio input for the yellow car stereo so I can enjoy all the new tracks collected over the past few months from the comfort of my wind-blown seat.


text:
The APACHE incorporates a closed muzzle, which helps with ease of loading and improved accuracy. The sealed barrel is anodized for enhanced corrosion resistance, while the ergonomic molded handle permits easier maneuverability and quick muzzle pointing. The power band is fitted with a standard stainless wishbone and the gun includes the widely preferred Tahitian style flopper shaft.
Technical features:
- Soft grip with sternal support and new ergonomic design
- Release mechanism automatically derived from the Comanche.
- Watertight Ø 26 mm aluminium barrel
- Open head for use with circular elastic
- Tahitian shaft steel
- It comes in the 45-60-75 cm long versions.


text:
A new version of Vyapin's SharePoint data import tool External Data Connector for SharePoint (v2.0) has been released. This release has two new features to connect and bridge your SharePoint content with Exchange mail content. These features help users import MS Exchange mail items from Mailboxes and Public Folders into SharePoint Lists as Items. Mail items can be imported selectively and made available for sharing and collaboration in SharePoint. For example, you can import all mails specific to a project or specific to a common mailbox (say for example, firstname.lastname@example.com) etc. You can perform a very granular import of mails based on various mail item properties such as From, To, Cc, Date range, Subject and Body content and message headers. Here are some of the benefits of importing your mails from exchange into SharePoint:
- You can setup a repository of content intelligence in SharePoint by importing mails that have certain keywords that are important to proactively manage and grow your business. You can select mails that indicate certain characteristics that you may be interested in when employees receive or send mails.
- You can import mails of projects on a scheduled basis for sharing and collaboration. For example if you sent a Survey or Feedback mail to you customers, you can import these into SharePoint for further action by your project group.
- If you have dedicated mail boxes for different customer facing activities say, Sales, Support, Marketing, Customer Service etc., you can have these mails imported selectively for further analysis by the related departments using SharePoint.
- If you already have a well-established SharePoint infrastructure, you can use SharePoint as an archive repository for your mailboxes.
- You can setup a complete Knowledge Base in SharePoint using content extracted from certain categories of mails for further use within the organization. For example, all Product support mails carrying certain problem phrases and subject lines can be extracted and stored in SharePoint to create a knowledge base for Employee training.
- The ability to granularly import mails from Exchange to SharePoint opens up immense possibilities for organizations to improve business functions and associated processes.
Here is a screenshot showing the additional features introduced in the product.
Public Folders to SharePoint
As the name indicates, this option helps users import Public Folder contents to SharePoint Lists. You can import Folder contents from Exchange on-premises or online. EDC 2.0 supports Exchange 2007, 2010, 2013 as shown below.
It also offers an in-depth search option to select and import mails based on – Date Range, Subject / Body, From / To / Cc, Headers. And you can save your search queries for repeated use. Here's a snapshot showing the filter criteria.
Message Folders to SharePoint
Similar to the previous option, this one allows users to import relevant mails from Exchange User Mailboxes into SharePoint Lists. You can import mails from all mailboxes or limit to specific ones as shown here.
And you can select specific folders to import mails from as shown in the choices here.
You can further filter the mails you want to import by selecting specific attributes. This step is designed to import only those mails needed to be imported to SharePoint. Here's a screenshot showing the attributes you can select.
Do you want to import Exchange mails and folders to SharePoint?
Vyapin External Data Connector for SharePoint provides you an easy import method.
Download and try it today!


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Wednesday, 26 August 2009
New Music Review: Bon Jovi
We Weren't Born To Follow is taken from Bon Jovi's latest album The Circle due for release in early November. The band had barely been off the road from performing their Lost Highway Tour before they began writing again for this new record, which is promised to be more rockier and edgier than it's Nashville-influnced country-tinged predecossor. And in a nut case, it is simply Bon Jovi sticking to what they are good at; the formula they are comfortable with and know will do well amongst their loyal followers. That is not to say though that this is a bad thing, because the band have certainly got a kick ass rock song in this. Jon's sneering vocals hide his true age (now nearing fifty) as the track sounds like it might have been taken from their 2005 release Have A Nice Day with it's big chorus and light-rock-big-stadium feel. I think all that the track is missing is a signature Sambora solo, but that's to not to say it's any less of a great song; what Sambora does perform fits perfectly. The guitar work in the choruses is progressive and melodic; with its shimmering and gleaming post-production touches, whilst it sits back strumming ghostly chords just once every four beats in the verses. Tico Torres is living up to his 'hit-man' alter ego as he pounds his way with a precision only experience can bring, settling for an almost tribal feel throughout the verses whilst opening up in the choruses. Said choruses of course are bound to be a hit with the New Jersey quintet's fanbase in their promised stadium tour throughout 2010 but I can't see it taking over the charts much here in the UK. The guys know who their fans are and don't have anything new to prove to anybody anymore; they're doing what they're doing for the love of it and they know how the fans will respond.
Bon Jovi have never been the critic's favourite band, and I think the left-turn apparent in their previous album will be over-looked as critics will probably favour the critical 'they've have taken it easy' approach which the band have recently adopted every other album. Philanthropist and charity worker Jon Bon Jovi cannot help but be affected with what he donates his hard-earned millions to, and this is ever-more apparent in his lyric writing as he finds his politcal pen and gives the working man a song to sing that he can believe in.
Radio friendly; yes. Stadium friendly; yes. A great move and a great song. In short, it sounds great; another classic Bon Jovi anthem with cool lyrics and a real fist-clenching chorus that will be rising above the rooves of stadiums in the UK come the summer next year with the classic remedy of 'let me hear ya say yeah yeah yeah' and I for one can't wait.
Posted by Samborakid at 19:57 No comments:
Tuesday, 25 August 2009
New Music Review: Taking Dawn
Skimming through the 'music issue' of my favoured glossy yesterday, I came across a section entitled 'The only ones to watch'. The article selected six different artists from as many genres, picking those who are about ready to hit the big time and if you were to start name-dropping now, you'd look pretty cool come winter. I've selected the metal entry, Taking Dawn, to write a short review about their track, 'Endlessly.' The guys hail from Las Vegas and are busy recording their debut album, having signed recently to Roadrunner Records (Nickelback, Slipknot, Trivium) whilst being dubbed '80s hard rockers for the Myspace generation'. You heard them here first (hopefully).
Something fresh, something different; certainly what our current music industry is in dire need of. The new wave of 80s-inspired dance/pop acts taking over our airwaves this summer has been a sure fire hit on the popular festival circuit, but we are in need of a slightly different 80s revival. And this is where Taking Dawn step up. Endlessly smacks of a forgotten 80s metal scene, these kids grew up listening to their forefathers of rock; Skid Row, Guns n Roses, Bon Jovi and the like, and have certainly put a fresh spin on the genre nearly 30 years on. The often-wailing guitars of front-man Chris Babbitt and his aide Mikey Cross sit perfectly atop the riff-heavy verses and the many layered, harmoniuos vocal lines of the whole band throughout really give it that 80s pinch. Alan Doucette's drums are simple; sitting nicely at the back of the mix like they should be; none of this fancy over-the-top stuff that's all too apparent in the young metal scene. He provides the back beat and nothing more. Lead singer Babbitt's vocals compliment the band's sound brilliantly with their raunchy, gutty rock edge reminiscent not just of modern metal saviours such as Hinder, but also tipping their cap to a hint of Axl Rose. Defintely worth a listen if you're in need of something fresh with that retro edge. Endlessly is taken from their debut album, the 'Taking Dawn Digital EP', due for release in November this year and you can access a free download of Endlessly here.
Posted by Samborakid at 11:43 1 comment:
Labels: metal, new band, new music, taking dawn
Monday, 24 August 2009
Techno Dreams, Or So It May Seem.
I didn't think it would feel weird to have the clutches of my laptop back within reach but, after just three weeks without internet access, the small, compact keys beneath my fingertips feel almost alien to me. Strange, for someone who has used a computer almost every single day for the past six years. Alas, we now have a phone line and an internet connection in the flat. And I haven't really missed tracking everything and everyone's actions as much as I thought I might do. The novelty is wearing off slightly, I feel I won't be as addicted as before. It is though one of the safer addictions to fall victim of.
What this post is really saying is that I'm back in touch with the technological world and will continue now to maintain this blog. Glastonbury really does feel like an age away. I've always been a Country boy and the mere though of living in a City was a reality I'd rather ignore however, contrary to my previous fears, Southampton already feels like home. Moving day was swift (would have been far swifter had it not been for the too-large sofa which would not squeeze into the too-small door frame. Cue a dismantling operation followed by a trip to B&Q followed by a reinvention) and everything had a home after just two days. It hasn't taken long to find my way around and I feel accepted here already. I'm too excited for words ahead of the thought of starting uni, and am willing the final few weeks away eagerly. I have friends visiting on Thursday and I can't wait to show them around my new home town. That's not to say I've forgotten all about Glastonbury, I'm just a little glad to be somewhere that I don't see the same face twice. Small towns are perfect for young children and the older generation, but I've got some living to do and a city is the only place to be.
Posted by Samborakid at 20:42 No comments:
Labels: new home, new start, university
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Fianna Fáil TD for Dublin Mid-West, John Curran has said we must do all it takes over the coming months to reverse the increase trend in road deaths last year, in co-operation with motorists, the public and An Garda Síochána across Dublin Mid-West.
Deputy Curran made the comments after receiving new information from the Minister for Transport in relation to reviewing the Road Safety Strategy 2013-2020 which was set out to over time lead to a reduction in road traffic collisions, fatalities and injuries and contribute to reducing the cost of motor insurance. The Road Safety Authority is expected to publish a report on their midterm review in the coming weeks.
"I must acknowledge the ongoing and important work of local Gardaí in their efforts towards making our roads safe; however, our existing Road Safety Strategy appears to have failed to achieve its core objective in lowering the number killed or injured on our roads," commented Deputy Curran.
"The evidence is clear and there was a rise of 15% in road deaths in 2016 to 187 persons, up from the figure of 162 road deaths in 2015. In Dublin last year there were 21 people killed on our roads up from 17 the year previous – these are not just damning figures, these are local people from our own families and communities
"The Garda Traffic Corps have taken quite a hit over the past six years – there are 300 fewer now than there were at the end of 2010. To keep our roads safe we need the rules to be enforced and that requires resources to be put in place.
"With that in mind Fianna Fáil secured a commitment to increase Garda numbers by 2,000 by 2021 and insistent on the Traffic Corps – or the Roads Policing Unit as it is to become – benefitting from those additional numbers.
"It is therefore hugely welcome that the Minister has confirmed to me this week that there is a pledged increase of 10% in the traffic corps over the course of the next 12 months. I am hopeful that this will result in more check points and greater enforcement of traffic law.
"Road safety must be a priority in the 2017 to ensure obedience of newly introduced road safety measures including regarding drug driving, mutual recognition of driving disqualifications with the UK and a new optional 20km/hr speed limit in built-up areas.
"There is an onus on the Minister, the RSA and An Garda Siochana to set aside any public squabbles to work in a coordinated and constructive way to continually promote safe road use.
"I will be urging the government to act quickly on this pledged increase in Traffic Corps numbers and which are urgently needed to strengthen the enforcement of road laws and to renew the importance of safe driving."


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