Vertical Sectorization Research Articles

Experimental investigation on a vertical sectorization system with active antenna

Cell splitting is an effective way of implementing network densification in order to boost the capacity of a mobile system. Traditionally, the cell splitting procedure has been carried out in the azimuth dimension. However, another approach known as vertical sectorization has been gaining momentum recently, where the sectors of a conventional cellular system are split vertically instead, creating inner and outer cells by using AAS technology. Then vertical sectorization can use the same communication resources in both inner and outer parts of the cells. Performance of vertical sectorization has been extensively studied in the literature using advanced system simulations. However, field measurements to characterize the actual performance of vertical sectorization with AAS have been scarce so far. In this article, we first identify key issues that may hinder the smooth implementation of commercial cellular systems using vertical sectorization. Then we present the results of a measurement campaign that was carried out to study these limitations and to identify the actual vertical radiation patterns when AAS technology is used. Finally, we reflect on some problems that remain open to make future cellular systems using vertical sectorization with AAS commercially viable.

MIMO Transmission With Vertical Sectorization for LTE-A Downlink

Recently, vertical sectorization (VS) has been proposed for multiple-input multiple-output (MIMO) transmission in long term evolution advanced (LTE-A) downlink systems. In this paper, we will investigate MIMO transmission with VS for LTE-A systems. We first divide each cell into two sectors in vertical direction so that more users can be co-scheduled and more refined beams can be formed in each sector. We then address how to jointly optimize two tilt angles, user scheduling, and resource block allocation for a practical LTE-A system, and provide an efficient VS-based MIMO scheduling algorithm with low-complexity. The performance improvement of the proposed algorithm is demonstrated by system level simulation.

Optimizing Radio Network Parameters for Vertical Sectorization via Taguchi's Method

In vertical sectorization, multiple antenna elements form two beams to better serve users based on their locations in the cell. However, it is not known how to choose the radio network parameters to ensure good network performance and the amount of capacity gain achievable with vertical sectorization. In this paper, we propose an optimization approach based on Taguchi's method for vertical sectorization deployment to improve the 50th and the 5th percentile user throughput. Unlike conventional works, our proposal is a scientifically disciplined approach optimizing jointly the downtilt angles, vertical beamwidths, and transmit powers of the two beams and taking into account the interaction amongst these network parameters. With the proposed method, the resulting 50th and 5th percentile user throughput and the total network throughput outperform those of the conventional networks without vertical sectorization.

Spatial Distribution of the SINR in Poisson Cellular Networks With Sector Antennas

A model of cellular networks where the base station locations constitute a Poisson point process and each base station is equipped with three sectorial antennas is proposed. This model permits studying the spatial distribution of the signal-to-interference-and-noise ratio (SINR) in the downlink. In particular, this distribution is shown to be insensitive to the distribution of antenna azimuths. Moreover, the effect of horizontal sectorization is shown to be equivalent to that of shadowing. Assuming ideal vertical antenna pattern, an explicit expression of the Laplace transform of the inverse of SINR is given. The model is validated by comparing its results to measurements in an operational network. It is observed numerically that, in the case of dense urban regions where interference is preponderant, one may neglect the effect of the vertical sectorization when calculating the distribution of the SINR, which provides considerable tractability. Combined with queuing theory results, the SINR’s distribution permits to express the user’s quality of service as function of the traffic demand. This permits in particular to operators to predict the required investments to face the continual increase of traffic demand.

Vertical sectorization in self-organizing LTE-advanced networks

Cellular radio networks continuously evolve to respond the exponential growth in data traffic volume in mobile communications. Active antenna technology contributes to this evolution by introducing vertical sectorization, which splits the horizontal sector into two subsectors with respect to the elevation plane and doubles the number of cells that can be deployed. However, in order to guarantee a reliable and near-optimal operation of vertical sectorization in a system that applies universal frequency reuse, such as LTE-advanced, co-channel interference mitigation is essentially needed. In this article we propose a decentralized self-optimization method that can be used to mitigate the undesirable inter-cell interference by self-tuning the electrical antenna downtilt toward the optimal antenna elevation angle. The performance evaluations for the proposed self-optimization method are carried out for both coordinated and uncoordinated subsector transmission scenarios within the LTE-advanced framework using a dynamic LTE-advanced compliant system level SON simulator. Based on the extensive performance evaluations carried out for a realistic urban scenario, it is found that self-optimization improves the vertical sectorization performance 25 % in terms of virtual load. Furthermore, the performance gain reaches up to 30 % when vertical vectorization is provided with dynamic point selection and muting feature. Therefore, the article concludes that in LTE-advanced networks vertical sectorization can largely benefit from the antenna self-optimization and outperform the traditional horizontal sectorization approach with low algorithmic complexity .

Interference Management by Vertical Beam Control Combined with Coordinated Pilot Assignment and Power Allocation in 3D Massive MIMO Systems

In order to accommodate huge number of antennas in a limited antenna size, a large scale antenna array is expected to have a three dimensional (3D) array structure. By using the Active Antenna Systems (AAS), the weights of the antenna elements arranged vertically could be configured adaptively. Then, a degree of freedom (DOF) in the vertical plane is provided for system design. So the three-dimension MIMO (3D MIMO) could be realized to solve the actual implementation problem of the massive MIMO. However, in 3D massive MIMO systems, the pilot contamination problem studied in 2D massive MIMO systems and the inter-cell interference as well as inter-vertical sector interference in 3D MIMO systems with vertical sectorization exist simultaneously, when the number of antenna is not large enough. This paper investigates the interference management towards the above challenges in 3D massive MIMO systems. Here, vertical sectorization based on vertical beamforming is included in the concerned systems. Firstly, a cooperative joint vertical beams adjustment and pilot assignment scheme is developed to improve the channel estimation precision of the uplink with pilots being reused across the vertical sectors. Secondly, a downlink interference coordination scheme by jointly controlling weight vectors and power of vertical beams is proposed, where the estimated channel state information is used in the optimization modelling, and the performance loss induced by pilot contamination could be compensated in some degree. Simulation results show that the proposed joint optimization algorithm with controllable vertical beams’ weight vectors outperforms the method combining downtilts adjustment and power allocation.

Design and Evaluation of a Dynamic Sectorization Algorithm for Terminal Airspace

Given its static and rigid structure, the current National Airspace System lacks the ability to cope efficiently with the increasingly severe demand–capacity imbalances expected to develop over the coming years. To better accommodate the flexibility desired for future flight operations and to alleviate the demand–capacity imbalances, research initiatives have been conducted under the dynamic airspace configuration concept. Although most past dynamic airspace configuration researchers have focused on en route airspace, this paper investigates terminal airspace operations. A dynamic sectorization algorithm for terminal airspace is developed, which combines a -means clustering-based vertical sectorization algorithm, an integer-programming-based horizontal sectorization algorithm, and an -shapes-based airspace sectorization algorithm. This dynamic sectorization algorithm is validated with real traffic data from several major international airports in the United States and simulated traffic data with projected future air routes and traffic patterns. Performance evaluation demonstrates that the algorithm can improve the efficiency of terminal airspace utilization and reduce traffic complexity.

LTE 시스템에서 수직적 섹터구분 방식의 성능 분석 및 최적 빔 조합 도출

Recently, owing to the development of active array antenna techniques, various sector beams can be applied to the LTE systems with vertical sectorization. In this paper, we evaluate the system performance and suggest an optimum beam combination and parameters by using a system level simulator

Resource Allocation for Vertical Sectorization in LTE-Advanced Systems

Massive multiple input multiple output (MIMO) technology has been discussed widely in the past few years. Three-dimensional MIMO (3D MIMO) can be seen as a promising technique to realize massive MIMO to enhance the performance of LTE-Advanced systems. Vertical sectorization can be introduced by means of adjusting the downtilt of transmitting antennas. Thus, the radiowave from a base station (BS) to a group of user equipments (UE) can be divided into two beams which point at two different areas within a cell. Intrasector interference is inevitable since the resources are overlapped. In this paper, the influence of intrasector interference is analyzed and an enhanced resource allocation scheme for vertical sectorization is proposed as a method of interference cancellation. Compared with the conventional 2D MIMO scenarios, cell average throughput of the whole system can be improved by vertical sectorization. System level simulation is performed to evaluate the performance of the proposed scheme. In addition, the impacts of downtilt parameters and intersite distance (ISD) on spectral efficiency and cell coverage are presented.