Pairs Of Stations Research Articles

Crustal Structure across the West Antarctic Rift System from Multicomponent Ambient Noise Surface Wave Tomography

Abstract Approximately 2 yr (2010–2011) of continuous seismic records from a subset of the Antarctic component of the Polar Earth Observing Network (POLENET-ANET) seismic network deployed in West Antarctica are used to compute the nine components of the correlation tensor between each pair of stations in the network. Rayleigh wave velocity information from the vertical and radial components was extracted in the form of group and phase velocity dispersion curves, whereas the transverse component provided complimentary Love wave velocity information. The multicomponent Rayleigh wave measurements (ZZ, RR, ZR, and RZ) were averaged and used to infer the measurement uncertainties. The Rayleigh and Love wave group and phase velocities were then regionalized in space using a 2D deterministic tomography. A transect that spans the West Antarctic rift system was extracted from the tomography at individual periods between 7 and 60 s for the four types of surface wave velocities (i.e., Rayleigh and Love phase and group velocities). A transdimensional Bayesian joint inversion algorithm was used to invert these four datasets for a 1D model of isotropic shear-wave velocity versus depth at each point along the transect. In this way, surface wave dispersion curves from multicomponent noise correlations were used to build a 2D isotropic shear-wave velocity model down to ∼55 km depth. In this model, the top of the large low-velocity zone beneath Marie Byrd Land was imaged (up to a 5% decrease in velocity at ∼50 km depth), which provides further evidence for a mantle hot spot beneath the crust that supports the high topography in this region. We also observed a large velocity contrast in the lower crust beneath Marie Byrd Land at a depth where previous long-period seismicity has been observed. This strong contrast occurs more shallow than in previous crustal models, which compared to our model identify a deeper Moho (∼5–10 km deeper) beneath Marie Byrd Land. This new model has implications for interpreting earthquake locations in this region and perhaps necessitates that we revisit past hypocenter estimation studies using updated velocity models for the region.

Imaging the crust and uppermost mantle structure of Portugal (West Iberia) with seismic ambient noise

SUMMARYWe present a new high-resolution 3-D shear wave velocity (Vs) model of the crust and uppermost mantle beneath Portugal, inferred from ambient seismic noise tomography. We use broad-band seismic data from a dense temporary deployment covering the entire Portuguese mainland between 2010 and 2012 in the scope of the WILAS project. Vertical component data are processed using phase correlation and phase weighted stack to obtain empirical Green functions (EGFs) for 2016 station pairs. Further, we use a random sampling and subset stacking strategy to measure robust Rayleigh-wave group velocities in the period range 7–30 s and associated uncertainties. The tomographic inversion is performed in two steps: First, we determine group-velocity lateral variations for each period. Next, we invert them at each grid point using a new trans-dimensional inversion scheme to obtain the 3-D shear wave velocity model. The final 3-D model extends from the upper crust (5 km) down to the uppermost mantle (60 km) and has a lateral resolution of ∼50 km. In the upper and middle crusts, the Vs anomaly pattern matches the tectonic units of the Variscan Massif and Alpine basins. The transition between the Lusitanian Basin and the Ossa Morena Zone is marked by a contrast between moderate- and high-velocity anomalies, in addition to two arched earthquake lineations. Some faults, namely, the Manteigas–Vilariça–Bragança fault and the Porto–Tomar–Ferreira do Alentejo fault, have a clear signature from the upper crust down to the uppermost mantle (60 km). Our 3-D shear wave velocity model offers new insights into the continuation of the main tectonic units at depth and contributes to better understanding the seismicity of Portugal.

Walk this way: Visualizing accessibility and mobility in metro station areas on a 3D pedestrian network

Accessibility and mobility are positioned differently at the heart of transportation planning; whilst a transportation system with high accessibility will not necessarily be able to support high mobility. In this short article, we evaluate and visualize the accessibility and mobility of pedestrian networks around the metro station areas in a transit-oriented city – Hong Kong. By using the newly released 3D pedestrian network for the whole of Hong Kong under the Open and Big Data Plans, we have created visualizations to compare the 500-m walking coverage area and reachable area with a 10-min walking distance that reflects the accessibility and mobility around metro station areas, respectively. We find that there are significant differences between accessibility and mobility for some stations. We illustrate the potential underlying causes by comparing three representative pairs of stations as examples.

Extracting reliable empirical Green's functions using weighted cross-correlation functions of ambient seismic noise in west-central and southern Brazil

SUMMARYAmbient seismic noise is now routinely used to study the Earth's interior. For an isotropic homogeneous medium, the basic assumption to extract seismic phases from a station pair is that the sources of seismic noise are distributed in such a way that there is a uniform energy flux around the station pair. In general, however, some particular azimuthal directions may dominate the energy flux, which directly affects the extracted interstation empirical Green's function (EGF). To solve this problem, we analysed synthetic cross-correlation functions (CCFs) from seismic pulses propagated in isotropic and anisotropic heterogeneous half-space media towards a station pair under the assumptions of uniformly and non-uniformly distributed sources of noise. A reliable EGF signal can be extracted by applying three processing steps: (1) normalizing the number of repeated stationary sources, (2) normalizing the energy of each excited source and (3) selecting coherent CCFs in the final stacking. In this way, three different classes of station pairs were identified based on the number of CCFs used in the stacking procedure. We introduced and applied a new method based on weighted root-mean-square stacking (WRMS) to the CCFs of more than 33 months of ambient noise recorded from January 2016 to September 2018 at 75 broad-band stations in West-Central Brazil. In the case of non-uniform distribution of source of noise, simple classical linear stacking of CCFs produces distorted EGFs. However, the waveform extracted by the WRMS method is very similar to the Rayleigh waves excited by an earthquake (on 2017 January 3) near one receiver observed at the other receiver. Moreover, synthetic tests and a comparison between extracted and earthquake signals show that although the WRMS method can extract the main part of the signal that is propagated on the shortest path, it cannot recover the energy parts propagated on multipath. Despite the N–W directionality in the geometry of the array, the rose-diagram results indicate no significant spatial variations in the energy level of EGFs extracted by the WRMS stacking, whereas the EGFs extracted by the classical linear stacking indicate the extreme directionality of energy flow in different period ranges. Rayleigh wave group and phase velocity tomographic maps resolved by the EGFs derived from the WRMS method indicate a clear boundary along the Asuncion and Rio Grande Arches between the Chaco-Paraná and the Paraná basins at the shorter period, while the tomographic maps in the same periods which were calculated by other stacking methods cannot clearly separate basins and arcs. Our tomographic maps at longer periods indicate variations of Moho depth and lithospheric velocities.

The Cheapest Ticket Problem in Public Transport

Route choice models in public transport have been discussed for a long time. The main reason why a passenger chooses a specific path is usually based on its length or travel time. However, also the ticket price that passengers have to pay may influence their decision because passengers prefer cheaper paths over more expensive ones. In this paper, we deal with the cheapest ticket problem, which asks for a cheapest ticket to travel between a pair of stations. The complexity and the algorithmic approach to solve this problem depend crucially on the underlying fare structure; for example, it is easy if the ticket price is proportional to the distance traveled (as in distance tariff fare structures), but may become NP-complete in zone tariff fare structures. We hence discuss the cheapest ticket problem for different variations of distance- and zone-based fare structures. We start by modeling the respective fare structure mathematically, then identify its main properties, and finally provide a polynomial algorithm, or prove NP-completeness of the cheapest ticket problem. We also provide general results on the combination of two fare structures, which is often observed in practice.

Research of the seismic velocity variation under the Redoubt volcano

Volcanoes are the most rapidly changing and difficult to study geological features. Identifying physical signatures of processes occurring during seismic and volcanic activity is one of the most important problem in seismology. Here we reveal temporal changes of seismic velocity in the upper crust for two years of eruption activity of the Redoubt volcano. Based on correlation of continuous records of seismic noise at pairs of stations, we obtained correlograms for selected time periods. Using the stretching method, we obtained relative velocity changes between stations. These variations appear to be consistent with the results of repeated tomography that was previously derived based on body waves from local earthquakes.

Droughts in Serbia through the analyses of De Martonne and Ped indices.

Due to global warming, droughts have become one of the focal points of researchers in the field of climate and water, all over the world. The analyses in this paper include spatial pattern and temporal trend for the territory of Serbia, over the 1949-2016 period. The De Martonne aridity index and the Ped drought index have been applied. Eighteen pairs of temperature and precipitation stations all over the country have been analyzed. The obtained results show a tendency toward a drier condition, which are not yet drastic.Drought areas for the territory of Serbia are increasing, but drought intensity and frequency should certainly be lower than those predicted for the Mediterranean coastal area, except in regions with very high human water use. Comparing the obtained results from stations at the original altitude and calculated data for the same stations at fixed virtual altitudes has shown that the natural direction of drought, which decreases from west to southeast, has shifted to a north to south direction.

The investigation on daytime conjugate hemispheric asymmetry along 100°E longitude using observations and model simulations: New insights

The hemispherical asymmetry of the low latitude region along 100°E ± 5°E is scrutinized for the year 2015 at magnetically conjugate points on seasonal and intra-seasonal time scales. Two conjugate Ionosonde station pairs are selected- one pair in the inner valley (from SEALION) and the other in the outer edges of the EIA region. The anomaly in the stations is estimated using the difference of low latitude NmF2 from the dip equatorial NmF2 in the same meridian. A monthly average scheme is used instead of a seasonal mean, as the month-to-month variations are found to provide intricate details. The anomaly at the conjugate stations is highly asymmetric even during the equinoctial months of March and October, whereas it is nearly symmetric during April. During June/July, the morning time hemispheric asymmetry (larger on the winter side) temporarily reduces in the midday period and then reverses sign (larger in summer) in the afternoon. The NmF2 observations suggest a close relation of hemispheric symmetry to the position of the subsolar point with respect to the dip equator and a shift/expansion of the trough region of the EIA towards the summer hemisphere. The inter-hemispheric comparison of the hmF2 suggests a strong modulating influence of meridional winds at both the inner and outer stations which depend strongly on the relative position of the subsolar point with respect to the field line geometry. Theoretical (SAMI3/SAMI2) and empirical model (IRI) simulations show a meridional movement of the EIA region with the subsolar point. The winter to summer hemisphere movement of the EIA trough and crest region is also reproduced in the GIM-TEC along 100°E for 2015. This shifting or tailoring of the trough and the crest region is attributed primarily to the meridional wind field, which varies with the shifting position of subsolar point relative to the field line geometry. The seasonal and intra-seasonal difference in the NmF2 hemispheric asymmetry is attributed to the misalignment of the two centers of power viz., the thermospheric/neutral processes and the electromagnetic forces, due to the geographic-geomagnetic offset in this longitude.

A Local Magnitude Scale from Borehole Recordings with Site Correction of the Surface to Downhole

Abstract The Central Weather Bureau of Taiwan deployed 62 borehole seismic stations equipped with accelerometers and broadband seismometers by the end of 2018. Currently, a large number of earthquake records has been accumulated because of the high seismicity rate of Taiwan. These records can be used to detect microseismicity because the background seismic noise level is lower at downhole stations than surface stations. However, the magnitudes of the waveforms recorded by the downhole stations are lower than those of surface stations because of near-surface site effects. In Taiwan, local magnitude (ML) determinations use an attenuation function derived from surface stations, and ML will be underestimated if this attenuation function is used for downhole stations. Records of 14,653 earthquakes were used to determine site amplifications corresponding to site corrections of the surface to downhole. For all available earthquake–station pairs, a total of 5470 amplification factors satisfied condition of the incident angle less than 35°, which are used for further discussion in this work. The results reveal that amplification factors ranging from 1.11 to 6.07 can be used to describe site effects. These amplification factors are strongly correlated with VS30 (average shear-wave velocity for the top 30 m of strata). The amplification factor was used to revise station ML for downhole accelerometer (denoted MLB), and revised MLB (MLBNEW) was compared with ML from the surface accelerometer (denoted MLS). Results show that MLBNEW and MLS are similar. Using the derived site corrections of surface to downhole, the downhole seismograms can be used to directly determine ML, especially for the borehole broadband waveforms, enhancing detection capabilities for microearthquakes and improving the Taiwanese earthquake catalog.

DORIS Alcatel ground antenna: Evaluation of the phase center variation models

The DORIS ground antenna phase center variation (PCV) modeling is an important factor of the DORIS solution accuracy and affects also the DORIS solutions employed in the ITRF2020 realization. There are two different elevation dependent models available for the Alcatel antenna, called here 1.0 and 2.0. For the Starec antenna we have only one PCV model. We demonstrate the effect of the Alcatel PCV model selection, reaching a value around 15 mm in the estimated DORIS station height. The post-fit Doppler observation residual analysis proved a better performance of the residuals derived from the solution employing Alcatel PCV model 2.0, particularly in several specific elevation intervals over 50 degrees. The elevation dependent systematics in the residuals have been proven by the separation of the ascending and descending portions of the residuals. The residual mean calculated for the elevation intervals reached values with a mutually opposite sign for the ascending and descending observations. Moreover, we have compared the residuals of the Starec and Alcatel stations, whereas the Starec residual RMS was lower for elevations approximately under 50 degrees, the Alcatel residual RMS was lower for higher elevations. This result could relate to an eventual Starec PCV model imperfection at higher elevations.To check the compatibility of the Starec and Alcatel PCV models impact on the station height, we have performed the comparison of the measured vertical component of the DORIS-DORIS local ties to a value calculated from the DORIS observations. The pairs of the Alcatel-Starec stations were the object of interest. When repeating the experiment with both Alcatel models 1.0 and 2.0, we have found a similar level of agreement of the measured and observed/computed height difference, but with the opposite sign. The average difference reached 8.7 ± 2.5 mm for Alcatel PCV model 1.0 and −7.2 ± 2.4 mm for Alcatel PCV model 2.0.

An innovative approach to select urban-rural sites for Urban Heat Island analysis: the case of Turin (Italy)

A novel metric – the Mean Temperature Difference (MTD) – is proposed for the selection of urban-rural pairs of stations needed in the Urban Heat Island (UHI) quantification. This metric highlights the thermal pattern typical of each weather station with respect to the average one of the area of interest. Afterwards, Principal Component Analysis is adopted to cluster stations into subsets exhibiting similar thermal behaviors. The joint use of MTD and PCA allows one to classify stations objectively and without the need of preliminary assumptions about the station landscapes. An application to the metropolitan area of Turin (Italy) and a comparison with validated methods to select urban-rural pairs demonstrate that the proposed approach is easily interpretable and reliable also when the study area exhibits a non-trivial landscape categorization.

Constraining the depth extent of low-velocity zone along the Chenghai Fault by dense array ambient noise interferometry and horizontal-to-vertical spectral ratio

The depth extent of low velocity fault zones is still a matter of debate due to the lack of vertical resolution for most seismic methods. Autocorrelations and cross-correlations of seismic ambient noise provide us new constraints on this issue by obtaining the shallow subsurface reflections without the need of active sources or earthquakes. The horizontal-to-vertical spectral ratio (HVSR) method can also give constraints on this interface and does not need any extra cost of data collection. In this study, we used one-month continuous seismic data from a dense linear array deployed crossing the Chenghai Fault (CHF) in Yunnan, southwest China. Single station autocorrelation and adjacent station pair cross-correlation methods were used to retrieve body wave reflections from the interface of the shallow crustal low-velocity zone (LVZ). The HVSR method was also performed to delineate the shape of the LVZ. Results show an inverted trapezoidal LVZ which extends to ~1.0 km depth across the fault zone with a lateral extent of ~3 km. Previous studies based on ambient noise surface-wave tomography and teleseismic travel time analysis in the same area show similar characteristics, consistent with the interpretation of our results.

Can site effects be estimated with respect to a distant reference station? Performance of the spectral factorization of coda waves

SUMMARY The reliability of the ground motion simulation is highly dependent on the quality of the site response (or site effects) evaluation. There are several methods to estimate the Site Amplification Factor (SAF) corresponding to Fourier Amplitude Spectra (FAS), either by using numerical simulation tools or empirical approaches. A widely used empirical method is the ‘Standard Spectral Ratio’ (SSR) technique based on the FAS ratio of the seismic record at a target site to the corresponding one at a nearby amplification-free ‘rock’ site (reference site). The main limitation of this method lies in the availability of a reference site relatively close to the target one. In this study a SAF estimation technique at a target site in relation to a distant reference site is presented and evaluated. This technique is based on the retrieval of the minimum phase Source Time Function (mpSTF) at a pair of examined sites (target-reference), with the Spectral Factorization analysis of Coda waves (SFC) proposed by Sèbe et al. The so derived mpSTF are considered as a convolution of the actual source function, and of the SAF, so that the FAS ratio of the mpSTF, derived at one site (target) and at a distant reference site, should be an estimate of the target SAF. The latter is confirmed in this study. Under the conditions of a common STF at the examined sites and of similar coda waves excitation factor, the ratio of the FAS of the mpSTFs (target over reference site) can safely approach the actual SAF, at least when target-reference distance is up to ∼60 km and provides encouraging results at longer distances. This technique was applied at 24 sites in western Greece in relation to 4 reference sites located at varying distances from the target ones (from 0.4 to 110 km). More than 700 STFs were calculated for 89 moderate magnitude earthquakes (3.9 ≤ M ≤ 5.1) located in this high seismicity area and SAFs were determined from each pair of target-reference stations using common seismic sources. Finally, the average SAFs were computed and compared to the ones computed by other methods (e.g. SSR, GIT and HVSR) demonstrating the reliability and robustness of the proposed technique in site effect estimation.

Square Kilometre Array Low Atomic commercial off-the-shelf correlator and beamformer

The Square Kilometre Array Low is a next generation radio telescope, consisting of 512 antenna stations spread over 65 km, to be built in Western Australia. The correlator and beamformer (CBF) design is central to the telescope signal processing. CBF receives 6 Tera-bits-per-second (Tbps) of station data continuously and processes it in real time with a compute load of 2 Peta-operations-per-second (Pops). The correlator calculates up to 22 million cross products between all pairs of stations, whereas the beamformers (BFs) coherently sum station data to form more than 500 beams. The output of the correlator is up to 7 Tbps, and the BF 2 Tbps. The design philosophy, called “Atomic COTS,” is based on commercial off-the-shelf (COTS) hardware. Data routing is implemented in network switches programmed using the Programming Protocol-Independent Packet Processors (P4) language and the signal processing occurs in COTS field-programmable gate array (FPGA) cards. The P4 language allows routing to be determined from the metadata in the Ethernet packets from the stations. That is, metadata describing the contents of the packet determines the routing. Each FPGA card inputs a fraction of the overall bandwidth for all stations and then implements the processing needed to generate complete science data products. Generation of complete science products in a single FPGA is named here as Atomic processing. A Tango distributed control system configures the multitude of processing modes as well as maintaining the overall health of the CBF system hardware. The resulting 6 Tbps in and 9 Tbps out, 2 Pops Atomic COTS network attached accelerator occupies five racks and consumes 60 kW.

Investigation of the relationship between f0f2 and the TEC using single station neural network models

The relationship between the ionospheric critical plasma frequencies (f0F2) and GNSS-TEC (Global Navigation Satellite System –Total Electron Content) measurements was investigated using an artificial neural network method. About 20 pairs of ionosonde-GNSS receiver stations from 2000 to 2016 were used. Results from this work indicate that the relationship between f0F2 and TEC is mostly affected by the seasons, followed by the level of solar activity, and then the local time. Geomagnetic activity was the least significant of the factors investigated. The relationship between f0F2 and TEC was also shown to exhibit spatial variation; the variation is less conspicuous for closely located stations. Single station models predicted the f0F2 more accurately at their particular localities and clearly overestimated values of the f0F2 ionosonde observations when used at different localities. This finding indicates that model predictions are better (in terms of reduced prediction errors) for the stations for which they are developed than for a different station. Our result visibly point out that models developed for a particular station cannot be effectively applied in another station located farther apart in space. The new approach described in this study represents an important contribution in space weather prediction.

Suitability Assessment of Weather Networks for Wind Data Measurements in the Athabasca Oil Sands Area

The Athabasca Oil Sands Area (AOSA) in Alberta, Canada, is considered to have a high density of weather stations. Therefore, our objective was to determine an optimal network for the wind data measurement that could sufficiently represent the wind variability in the area. We used available historical data records of the weather stations in the three networks in AOSA, i.e., oil sands monitoring (OSM) water quantity program (WQP) and Wood Buffalo Environmental Association (WBEA) edge sites (ES) and meteorological towers (MT) of the air program. Both graphical and quantitative methods were implemented to find the correlations and similarities in the measurements between weather stations in each network. The graphical method (wind rose diagram) was found as a functional tool to understand the patterns of wind directions, but it was not appropriate to quantify and compare between wind speed data of weather stations. Therefore, we applied the quantitative method of the Pearson correlation coefficient (r) and absolute average error (AAE) in finding a relationship between the wind data of station pairs and the percentage of similarity (PS) method in quantifying the closeness/similarity. In the correlation analyses, we found weak to strong correlations in the wind data of OSM WQP (r = 0.04–0.69) and WBEA ES (r = 0.32–0.77), and a strong correlation (r = 0.33–0.86) in most of the station pairs of the WBEA MT network. In the case of AAE, we did not find any acceptable value within the standard operating procedure (SOP) threshold when logically combining the values of the u and v components together. In the similarity analysis, minor similarities were identified between the stations in the three networks. Hence, we presumed that all weather stations would be required to measure wind data in the AOSA.

Quantifying relations and similarities of the meteorological parameters among the weather stations in the Alberta Oil Sands region.

Our objective was to quantify the similarity in the meteorological measurements of 17 stations under three weather networks in the Alberta oil sands region. The networks were for climate monitoring under the water quantity program (WQP) and air program, including Meteorological Towers (MT) and Edge Sites (ES). The meteorological parameters were air temperature (AT), relative humidity (RH), solar radiation (SR), barometric pressure (BP), precipitation (PR), and snow depth (SD). Among the various measures implemented for finding correlations in this study, we found that the use of Pearson’s coefficient (r) and absolute average error (AAE) would be sufficient. Also, we applied the percent similarity method upon considering at least 75% of the value in finding the similarity between station pairs. Our results showed that we could optimize the networks by selecting the least number of stations (for each network) to describe the measure-variability in meteorological parameters. We identified that five stations are sufficient for the measurement of AT, one for RH, five for SR, three for BP, seven for PR, and two for SD in the WQP network. For the MT network, six for AT, two for RH, six for SR, and four for PR, and the ES network requires six for AT, three for RH, six for SR, and two for BP. This study could potentially be critical to rationalize/optimize weather networks in the study area.

ГЕОДИНАМІКА

The differential and source terms locations of a series of small (1.0<ML<2.5) similar (recurrent) earthquakes that occurred during 2013-2015 near the village of Trosnyk in the south of Transcarpathians were determined. Adaptive filtering was proposed to reduce the effect of correlated noise in records with very low signal-to-noise ratio and to improve the reliability of differential arrivals. The maximum correlation criterion was modified to include the minimum departure from the calculated arrival times. Analysis of the intervals between phase arrivals at pairs of stations was proposed to further reduce the number of problematic arrivals. The sensitivity of the final solution to the network configuration was assessed using the jack-knife principle, when the coordinates are calculated, each time removing one station from the full set. The focal mechanism common to all earthquakes in the series was defined using the polarities of P-wave arrivals at 16 stations. Based on the results of the 3D interpretation of the differential hypocenters, the nodal plane with a strike of 150° was identified as the rupture plane, and the mechanism itself was classified as left-lateral slip with a component of thrust. The epicenter of the strongest earthquake was located almost exactly on the fault of the pre-Neogene basement with a strike parallel to the Carpathian arc, almost the same as the strike of the rupture plane. The axis of compression in the focal mechanism is directed to the east, which is fully consistent with the northeast direction of the general regional field.

Temperature inversions in France – Part B: Spatial variations

Our database comprises daily minimum and maximum temperatures observed over 10 years at 859 pairs of meteorological stations throughout France. Each pairing associates a low and a high station. The influence of six predictors on the intensity, frequency, and duration of temperature inversions is measured by linear regressions. Five predictors are drawn from a 250 m-resolution DTM: elevation, depth of the valley where the low stations are located, magnitude of positive relief (ridge, hills), gradient of the slope of the hill or mountainside, and altitudinal amplitude between the high and the low station. The sixth descriptor used is the distance to the nearest sea. Topography exerts a major influence over the formation of thermal inversions. Three of the descriptors account for more than 80% of the variance of the inversion characters: distance to the sea, valley depth, and altitudinal amplitude. Elevation explains only 24% of that variance. The spatial distribution of the three characteristics of the inversions highlights several categorizations that fit into several nested scales. The 859 sites can be arranged into three classes relating to mountains, coastal areas, and plateaus. However, their distribution over the area under consideration is unclear and fails to indicate sharply delimited groupings.

User Association and Hybrid Beamforming Designs for Cooperative mmWave MIMO Systems

Hybrid analog and digital beamforming has emerged as a key enabling technology for millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) communication systems since it can balance the trade-off between system performance and hardware efficiency. Owing to the strong ability of central control, cooperative networks show great potential to enhance the spectral efficiency of mmWave communications. In this paper, we consider cooperative mmWave MIMO systems and propose user association and hybrid beamforming design algorithms for three typical hybrid beamforming architectures. The central processing unit (CPU) of the cooperative networks first matches the service pairs of base stations (BSs) and users. Then, an iterative hybrid beamforming design algorithm is proposed to maximize the weighted achievable sum-rate performance of the mmWave MIMO system with fully connected hybrid beamforming architecture. Moreover, a heuristic analog beamforming design algorithm is introduced for the fixed subarray hybrid beamforming architecture. In an effort to further exploit multiple-antenna diversities, we also consider the dynamic subarray architecture and propose a novel antenna design algorithm for the analog beamforming design. Simulation results illustrate that the proposed hybrid beamforming algorithms achieve a significant performance improvement than other existing approaches and the dynamic subarray architecture has great advantages of improving the energy efficiency (EE) performance.