Showing papers by "NTT DoCoMo published in 2012"

Coordinated multipoint transmission and reception in LTE-advanced: deployment scenarios and operational challenges

Abstract: 3GPP has completed a study on coordinated multipoint transmission and reception techniques to facilitate cooperative communications across multiple transmission and reception points (e.g., cells) for the LTE-Advanced system. In CoMP operation, multiple points coordinate with each other in such a way that the transmission signals from/to other points do not incur serious interference or even can be exploited as a meaningful signal. The goal of the study is to evaluate the potential performance benefits of CoMP techniques and the implementation aspects including the complexity of the standards support for CoMP. This article discusses some of the deployment scenarios in which CoMP techniques will likely be most beneficial and provides an overview of CoMP schemes that might be supported in LTE-Advanced given the modern silicon/DSP technologies and backhaul designs available today. In addition, practical implementation and operational challenges are discussed. We also assess the performance benefits of CoMP in these deployment scenarios with traffic varying from low to high load.

HEVC Complexity and Implementation Analysis

Abstract: Advances in video compression technology have been driven by ever-increasing processing power available in software and hardware. The emerging High Efficiency Video Coding (HEVC) standard aims to provide a doubling in coding efficiency with respect to the H.264/AVC high profile, delivering the same video quality at half the bit rate. In this paper, complexity-related aspects that were considered in the standardization process are described. Furthermore, profiling of reference software and optimized software gives an indication of where HEVC may be more complex than its predecessors and where it may be simpler. Overall, the complexity of HEVC decoders does not appear to be significantly different from that of H.264/AVC decoders; this makes HEVC decoding in software very practical on current hardware. HEVC encoders are expected to be several times more complex than H.264/AVC encoders and will be a subject of research in years to come.

Intra Coding of the HEVC Standard

Abstract: This paper provides an overview of the intra coding techniques in the High Efficiency Video Coding (HEVC) standard being developed by the Joint Collaborative Team on Video Coding (JCT-VC). The intra coding framework of HEVC follows that of traditional hybrid codecs and is built on spatial sample prediction followed by transform coding and postprocessing steps. Novel features contributing to the increased compression efficiency include a quadtree-based variable block size coding structure, block-size agnostic angular and planar prediction, adaptive pre- and postfiltering, and prediction direction-based transform coefficient scanning. This paper discusses the design principles applied during the development of the new intra coding methods and analyzes the compression performance of the individual tools. Computational complexity of the introduced intra prediction algorithms is analyzed both by deriving operational cycle counts and benchmarking an optimized implementation. Using objective metrics, the bitrate reduction provided by the HEVC intra coding over the H.264/advanced video coding reference is reported to be 22% on average and up to 36%. Significant subjective picture quality improvements are also reported when comparing the resulting pictures at fixed bitrate.

Achieving "Massive MIMO" Spectral Efficiency with a Not-so-Large Number of Antennas

Abstract: Time-Division Duplexing (TDD) allows to estimate the downlink channels for an arbitrarily large number of base station antennas from a finite number of orthogonal uplink pilot signals, by exploiting channel reciprocity. Based on this observation, a recently proposed "Massive MIMO" scheme was shown to achieve unprecedented spectral efficiency in realistic conditions of distance-dependent pathloss and channel coherence time and bandwidth. The main focus and contribution of this paper is an improved Network-MIMO TDD architecture achieving spectral efficiencies comparable with "Massive MIMO", with one order of magnitude fewer antennas per active user per cell (roughly, from 500 to 50 antennas). The proposed architecture is based on a family of Network-MIMO schemes defined by small clusters of cooperating base stations, zero-forcing multiuser MIMO precoding with suitable inter-cluster interference mitigation constraints, uplink pilot signals allocation and frequency reuse across cells. The key idea consists of partitioning the users into equivalence classes, optimizing the Network-MIMO scheme for each equivalence class, and letting a scheduler allocate the channel time-frequency dimensions to the different classes in order to maximize a suitable network utility function that captures a desired notion of fairness. This results in a mixed-mode Network-MIMO architecture, where different schemes, each of which is optimized for the served user equivalence class, are multiplexed in time-frequency. In order to carry out the performance analysis and the optimization of the proposed architecture in a systematic and computationally efficient way, we consider the large-system regime where the number of users, the number of antennas, and the channel coherence block length go to infinity with fixed ratios.

A novel architecture for LTE-B :C-plane/U-plane split and Phantom Cell concept

Abstract: This paper introduces a novel approach in increasing the capacity of LTE cellular networks. The solution is based on massive deployment of small cells by leveraging high frequency reuse at high frequency bands in conjunction with a Macrocell. The presence, discovery and usage of the small cells are controlled dynamically by a Macrocell in a master-slave configuration hence they are called Phantom Cells. To realize this concept, a new method of managing the connections between mobile terminals and small cell nodes is introduced. It is achieved by splitting the Control and User (C/U) planes of the radio link. The combination of C/U-plane split and Phantom Cells can achieve high capacity enhancement using small cells at the same time taking into consideration mobility, scalability and flexibility requirements for massive deployment. The advantages of this approach as well as the implementation aspects are described in the paper. Simulations were also conducted to verify the concept and the results show some promising capacity enhancements. The rest of the paper describes the Phantom Cell concept as well as the challenges of deploying small cells in LTE networks.

Distribution of Downlink SINR in Heterogeneous Cellular Networks

Abstract: The Signal to Interference Plus Noise Ratio (SINR) on a wireless link is an important basis for consideration of outage, capacity, and throughput in a cellular network. It is therefore important to understand the SINR distribution within such networks, and in particular heterogeneous cellular networks, since these are expected to dominate future network deployments . Until recently the distribution of SINR in heterogeneous networks was studied almost exclusively via simulation, for selected scenarios representing pre-defined arrangements of users and the elements of the heterogeneous network such as macro-cells, femto-cells, etc. However, the dynamic nature of heterogeneous networks makes it difficult to design a few representative simulation scenarios from which general inferences can be drawn that apply to all deployments. In this paper, we examine the downlink of a heterogeneous cellular network made up of multiple tiers of transmitters (e.g., macro-, micro-, pico-, and femto-cells) and provide a general theoretical analysis of the distribution of the SINR at an arbitrarily-located user. Using physically realistic stochastic models for the locations of the base stations (BSs) in the tiers, we can compute the general SINR distribution in closed form. We illustrate a use of this approach for a three-tier network by calculating the probability of the user being able to camp on a macro-cell or an open-access (OA) femto-cell in the presence of Closed Subscriber Group (CSG) femto-cells. We show that this probability depends only on the relative densities and transmit powers of the macro- and femto-cells, the fraction of femto-cells operating in OA vs. Closed Subscriber Group (CSG) mode, and on the parameters of the wireless channel model. For an operator considering a femto overlay on a macro network, the parameters of the femto deployment can be selected from a set of universal curves.

Flexible power modeling of LTE base stations

Abstract: With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters.

Performance of non-orthogonal access with SIC in cellular downlink using proportional fair-based resource allocation

Abstract: This paper investigates the system-level throughput of non-orthogonal access with a successive interference canceller (SIC) in the cellular downlink assuming proportional fair (PF)-based radio resource (bandwidth and transmission power) allocation. The purpose of this study is to examine the possibility of applying non-orthogonal access with a SIC to the systems beyond the 4G (thus IMT-Advanced) cellular system. Both the total and cell-edge average user throughput are important in a real system. PF-based scheduling is known to achieve a good tradeoff by maximizing the product of the average user throughput among users within a cell. In non-orthogonal access with a SIC, the scheduler allocates the same frequency to multiple users, which necessitates multiuser scheduling. To achieve a better tradeoff between the total and cell-edge average user throughput, we propose and compare three power allocation strategies among users, which are jointly implemented with multiuser scheduling. Extensive simulation results show that non-orthogonal access with a SIC with a moderate number of non-orthogonally multiplexed users significantly enhances the system-level throughput performance compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.

LTE-advanced: an operator perspective

Abstract: LTE-Advanced extends the capabilities originally developed in LTE within the 3GPP. Carrier aggregationis the most significant, albeit complex, improvement provided by LTE-Advanced. Bandwidths from various portions of the spectrum are logically concatenated resulting in a virtual block of a much larger band, enabling increased data throughput. Additionally, enhancements to MIMO antenna techniques in the uplink and downlink further increase the data throughput. Cell coverage is improved by means of relay nodes, which connect to donor eNode-Bs. To cope with the many varieties of cell types and sizes (macro, pico, femto), intercell interference control is enhanced to handle these heterogeneous networks. Operators hope to leverage LTE-Advanced to offer their mobile wireless customers a vastly superior user experience.

On the Expanded Region of Picocells in Heterogeneous Networks

Abstract: In order to expand the downlink (DL) coverage areas of picocells in the presence of an umbrella macrocell, the concept of range expansion has been recently proposed, in which a positive range expansion bias (REB) is added to the DL received signal strengths (RSSs) of picocell pilot signals at user equipments (UEs). Although range expansion may increase DL footprints of picocells, it also results in severe DL inter-cell interference in picocell expanded regions (ERs), because ER picocell user equipments (PUEs) are not connected to the cells that provide the strongest DL RSSs. In this paper, we derive closed-form formulas to calculate appropriate REBs for two different range expansion strategies, investigate both DL and uplink (UL) inter-cell interference coordination (ICIC) to enhance picocell performance, and propose a new macrocell-picocell cooperative scheduling scheme to mitigate both DL and UL interference caused by macrocells to ER PUEs. Simulation results provide insights on REB selection approaches at picocells, and demonstrate the benefits of the proposed macrocell-picocell cooperative scheduling scheme over alternative approaches.

Interference-aware resource allocation for device-to-device communications as an underlay using sequential second price auction

Abstract: An innovative resource allocation scheme is proposed to improve the performance of device-to-device (D2D) communications as an underlay in the downlink (DL) cellular networks. To optimize the system sum rate over the resource sharing of both D2D and cellular modes, we introduce a sequential second price auction as the allocation mechanism. In the auction, all the spectrum resources are considered as a set of resource units, which are auctioned off by groups of D2D pairs in sequence. We first formulate the value of each resource unit for each D2D pair, as a basis of the proposed auction. And then a detailed auction algorithm is explained using a N-ary tree. The equilibrium path of a sequential second price auction is obtained in the auction process, and the state value of the leaf node in the end of the path represents the final allocation. The simulation results show that the proposed auction algorithm leads to a good performance on the system sum rate, efficiency and fairness.

Enhanced local access in mobile communications

Abstract: A hybrid user equipment and advanced user equipment data offloading architecture is provided. In this hybrid architecture, the advanced user equipment includes a backhaul link to a telecommunication network and/or the Internet. The user equipment can send and receive data through the advanced user equipment using the backhaul link.

IDMA vs. CDMA: Analysis and Comparison of Two Multiple Access Schemes

Abstract: This article presents comprehensive comparisons of interleave division multiple access (IDMA) and direct sequence code division multiple access (DS-CDMA) in terms of performance and complexity assuming iterative multiuser detection. IDMA can be seen as a special case of DS-CDMA with spreading gain of one using very low rate code and user-specific interleavers for user separation. We focus on three suboptimum linear detectors: minimum mean square error (MMSE), rake (or matched filter), and soft-rake detectors from practical concerns. We analytically prove that the three detectors are equivalent for asynchronous users of IDMA on frequency flat channels for complex modulation alphabets. Such equivalence has been shown only for binary phase shift keying (BPSK) in the literature. The equivalence guarantees the MMSE solution for IDMA without computationally expensive matrix inversions or matrix-vector multiplications. This is generally not the case for DS-CDMA since DS-CDMA is sensitive to user asynchronism. We also discuss complexity aspects when the MMSE detector is used where we focus on essential differences in complexity between IDMA and DS-CDMA, instead of discussing particular complexity reduction techniques. Computer simulations are performed in various scenarios and the performance is analyzed by bit error rate simulations as well as by extrinsic information transfer (EXIT) charts. The analysis reveals the advantages of IDMA over DS-CDMA in terms of performance and complexity under practical considerations, particularly in highly user loaded scenarios.

Network virtualization: a hypervisor for the Internet?

Abstract: Network virtualization is a relatively new research topic A number of articles propose that certain benefits can be realized by virtualizing links between network elements as well as adding virtualization on intermediate network elements In this article we argue that network virtualization may bring nothing new in terms of technical capabilities and theoretical performance, but it provides a way of organizing networks such that it is possible to overcome some of the practical issues in today?s Internet We strengthen our case by an analogy between the concept of network virtualization as it is currently presented in research, and machine virtualization as proven useful in deployments in recent years First we make an analogy between the functionality of an operating system and that of a network, and identify similar concepts and elements Then we emphasize the practical benefits realized by machine virtualization, and we exploit the analogy to derive potential benefits brought by network virtualization We map the established applications for machine virtualization to network virtualization, thus identifying possible use cases for network virtualization We also use this analogy to structure the design space for network virtualization

Multiple-antenna techniques in LTE-advanced

Abstract: In this article we discuss the different multiple antenna techniques introduced in LTE-Advanced. Rather than describing the technical details of the adopted solutions, we approach the problem starting from the design targets and the antenna deployments prioritized by the operators. Then we present the main enabling solutions introduced for downlink and uplink transmissions, and subsequently assess the performance of these solutions in different scenarios. Finally, we discuss some possible future developments.

Uplink non-orthogonal access with MMSE-SIC in the presence of inter-cell interference

Abstract: This paper investigates the system-level throughput performance of non-orthogonal access with minimum mean squared error-based linear filtering followed by a successive interference canceller (MMSE-SIC) in the cellular uplink. Although non-orthogonal access employing the MMSE-SIC achieves the entire region of the multiuser capacity in a multiple access channel (MAC), which should be beneficial in enhancing the total user throughput and cell-edge user throughput simultaneously compared to orthogonal access, the multiplexing of multiple users within the same frequency block increases the inter-cell interference in the context of the cellular uplink. The aim of the transmission power control method investigated in this paper is to mitigate the inter-cell interference increase due to non-orthogonal user multiplexing. We employ a weighted proportional fair (PF)-based multiuser scheduling scheme to achieve a good tradeoff between the total user throughput and cell-edge user throughput. Simulation results show that non-orthogonal access employing the MMSE-SIC using the proposed transmission power control significantly enhances the system-level throughput performance compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.

Receiver, transmitter and radio communication method

Abstract: A mobile station includes: a physical channel segmentation unit to receive radio signals including multiple orthogonal signals which are orthogonal to each other, and multiple non-orthogonal signals which are not orthogonal to each other; and data demodulating/decoding units to extract the non-orthogonal signal addressed to the mobile station from the multiple non-orthogonal signals by demodulating and cancelling the radio signal addressed to another mobile station by use of the orthogonal signals included in the radio signals received by the physical channel segmentation unit, and demodulate the signal included in the orthogonal signals and addressed to the mobile station, and the extracted non-orthogonal signal addressed to the mobile station.

Minimization of drive tests solution in 3GPP

Abstract: Providing network coverage and quality of service (QoS) is an important task of a cellular network operator. This is because cellular spectrum is normally licensed under certain coverage obligations, and operators need to be competitive in market. To improve their networks, operators often send engineers in the field to collect radio measurements, to discover problems such as coverage holes in the network, and to determine whether certain parameter tuning is needed. However, such conventional "drive tests" require large Operation Expenditure (OPEX), while the collected measurements can only give limited snap shots of the entire network. In their Release 10 (Rel-10) specification, 3GPP studied and specified solutions to reduce this OPEX for drive tests, under the work item named ?Minimization of Drive Tests (MDT)." The solution utilizes the user (customer) equipments (UEs) to collect field measurements, including radio measurements and location information. This article describes in details the solution adopted in 3GPP MDT; how they were developed and intended to be used.

Minimization of drive tests in 3GPP release 11

Abstract: Minimization of drive tests is a feature introduced in 3GPP Release 10 that enables operators to utilize users' equipment to collect radio measurements and associated location information, in order to assess network performance while reducing the OPEX associated with traditional drive tests. However, in the increasingly complex wireless packet data networks of today, performance is affected by many different factors and cannot easily be estimated by simple radio measurements. Therefore, in 3GPP Release 11 specifications, MDT is enhanced in order to provide a more complete view of network performance. This article describes the MDT enhancements added in Release 11, explains how measurements collected by MDT can be used to draw conclusions that are relevant for network management, and discusses similarities and differences between MDT and traditional drive tests.

Radio communication system, radio base station apparatus, user terminal and radio communication method

Abstract: To reduce overhead of CSI feedback without decreasing throughput in applying CoMP transmission, a radio communication method of the invention is characterized by including, in a user terminal measuring quality information for each of cells to perform Coordinated Multi-Point transmission, and notifying a radio base station apparatus of the quality information, in the radio base station apparatus calculating a quality difference between the cells to perform Coordinated Multi-Point transmission, by using the quality information for each the cells from the user terminal, determining granularity of inter-cell channel state information for each of the cells based on the quality difference, and notifying the user terminal of the granularity, and, in that the user terminal generating inter-cell channel state information for each of the cells according to the granularity from the radio base station apparatus, and transmitting the inter-cell channel state information for each of the cells to radio base station apparatuses of cells to perform Coordinated Multi-Point transmission

Dynamic TDD support in the LTE-B enhanced Local Area architecture

Abstract: The Third Generation Partnership Project (3GPP) has been studying dynamic allocation of sub-frames to uplink (UL) or downlink (DL) in Time Division Duplex (TDD), called ‘Dynamic TDD,’ since the Long Term Evolution (LTE) Rel. 11 timeframe. At the same time, 3GPP is also standardizing Enhanced Local Area (eLA) small-cell heterogeneous architectures for inclusion in LTE-B (LTE Rel. 12) as a solution offering high data rate to user terminals (UEs) along with high system capacity through spatial reuse of spectrum. In this paper, we focus on a particular eLA architecture proposed by DOCOMO, called the Phantom Cell architecture, that has the option to support dynamic TDD. For an arbitrarily-located UE in an eLA cell network, we apply results from stochastic geometry to derive expressions for the distribution of DL signal to interference plus noise ratio (SINR) at an arbitrary UE and the distribution of UL SINR at its serving eLA base station (BS). We use these results to study aspects of eLA cell system design, and the sensitivity of SINR to the extent of coordination across eLA cells employing dynamic TDD.

Method and apparatus at the physical and link layer for mobile communications

Abstract: In a cellular telecommunications network, a mobile communication system to offload data traffic from base stations to small-node devices, includes a radio base station, a plurality of small-node devices, a macro-base-station-to-the-small-node-device (BS2D) communication section configured to receive a first control-plane message from the radio base station over a BS2D communication link, a small-node-device-to-user-equipment (D2UE) communication section configured to transmit user-plane data to a user equipment over a wireless D2UE communication link established responsive to the first control-plane message, and a center small-node device. The center small-node device includes a buffer section, a backhaul communication section configured to receive the user-plane traffic data from a server over a backhaul link, and is configured to manage D2UE connections between the plurality of small-node devices and the mobile station, buffer data to be transmitted in downlink and uplink for the plurality of small-node devices, and conduct a link adaptation for the D2UE connections.

Enhancing user fairness in non-orthogonal access with successive interference cancellation for cellular downlink

Abstract: Aiming at a better tradeoff between the system frequency efficiency measured by the mean user throughput and the user fairness measured by the cell-edge user throughput, we propose applying fractional frequency reuse (FFR) and weighted proportional fair (PF)-based multiuser scheduling to non-orthogonal access with a successive interference canceller (SIC) in the cellular downlink. We also propose a frequency block access policy for cell-interior and cell-edge user groups in FFR, which are appropriate for non-orthogonal access with the SIC. The optimum power is allocated to the non-orthogonally multiplexed users in conjunction with the weighted multiuser PF scheduler. Extensive simulation results show that the proposed non-orthogonal access scheme with the SIC significantly enhances the system frequency efficiency and user fairness at the same time compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.

Wireless base station, user terminal, wireless communication system, and wireless communication method

Abstract: The present invention inhibits the calculation processing load of a mobile station and the feedback data volume of a CSI from increasing and prevents the capacity of the entire system from reducing. This wireless communication system (1) is provided with a wireless base station (200) capable of forming a plurality of vertical sectorization beams. The wireless base station (200) at least forms, in parallel, a first beam facing the cell edge and a second beam facing the cell center by using an array antenna (10). A mobile station (100) measures the channel quality of the first beam and the second beam by extracting the reference signals from the first beam and the second beam, generates a communication quality feedback signal containing the channel quality obtained by measuring at least one of the beams, and feeds said signal back to the wireless base station (200) via uplink.

MobiSurf: improving co-located collaboration through integrating mobile devices and interactive surfaces

Abstract: One of the most popular scenarios for advertising interactive surfaces in the home is their support for solving co-located collaborative tasks. Examples include joint planning of events (e.g., holidays) or deciding on a shared purchase (e.g., a present for a common friend). However, this usually implies that all interactions with information happen on the common display. This is in contrast to the current practices to use personal devices and further, most people's behavior to constantly switch between individual and group phases because people have differing search strategies, preferences, etc. We therefore investigated how the combination of personal devices and a simple way of exchanging information between these devices and an interactive surface changes the way people solve collaborative tasks compared to an existing approach of using personal devices. Our study results clearly indicate that the combination of personal and a shared device allows users to fluently switch between individual and group work phases and users take advantage of both device classes.

Theoretical analysis of handover failure and ping-pong rates for heterogeneous networks

Abstract: In this paper, we characterize the relation between handover failure and ping-pong rates in a 3GPP heterogeneous network scenario as a function of relevant system parameters such as time-to-trigger, user equipment velocity, range expansion bias, etc. Under the assumptions that the picocell coverage and radio link failure areas are circular regions, and that users follow linear trajectories, handover failure and ping-pong rates are derived in closed-form expressions. Simulation results verify the accuracy of our analytical derivations, which shed new light on key aspects of the handover process in a heterogeneous network.

Personal Projectors for Pervasive Computing

Abstract: Projectors are pervasive as infrastructure devices for large displays but are now also becoming available in small form factors that afford mobile personal use. This article surveys the interaction space of "projectors on the move" and reviews input and output concepts, underlying sensing challenges, and emerging applications.

Evolution concept and candidate technologies for future steps of LTE-A

Abstract: This paper presents our views on the evolution concept and candidate technologies for future steps of 3GPP LTE-Advanced (LTE-A), which was the first major step in the continuous evolution of LTE. In the future steps of LTE-A, we will need to ensure the sustainability of 3GPP radio access technologies in order to respond to the anticipated challenging requirements in the future. Taking into account the ever-increasing importance of local area (small cells) and the need for further spectrum extension in particular, we present a common evolution concept for the future steps of LTE-A (referred to as LTE-B, C, and so on). This concept emphasizes integration of local area and wide area and focuses on frequency-separated deployment between local area and wide area as an important scenario for the efficient utilization of higher frequency bands. Furthermore, we identify key potential technologies for further spectrum efficiency enhancements, e.g., 3D/massive MIMO/beamforming, receiver interference cancellation, and dynamic TDD, and for integrating local area with wide area assuming the frequency-separated scenario using the proposed macro-assisted small cell that we refer to as a Phantom cell.

Proactive seeding for information cascades in cellular networks

Abstract: Online social networks (OSNs) play an increasingly important role today in informing users about content. At the same time, mobile devices provide ubiquitous access to this content through the cellular infrastructure. In this paper, we exploit the fact that the interest in content spreads over OSNs, which makes it, to a certain extent, predictable. We propose Proactive Seeding-a technique for minimizing the peak load of cellular networks, by proactively pushing (“seeding”) content to selected users before they actually request it. We develop a family of algorithms that take as input information primarily about (i) cascades on the OSN and possibly about (ii) the background traffic load in the cellular network and (iii) the local connectivity among mobiles; the algorithms then select which nodes to seed and when. We prove that Proactive Seeding is optimal when the prediction of information cascades is perfect. In realistic simulations, driven by traces from Twitter and cellular networks, we find that Proactive Seeding reduces the peak cellular load by 20%–50%. Finally, we combine Proactive Seeding with techniques that exploit local mobile-to-mobile connections to further reduce the peak load.

Base station and communication control method

Abstract: A base station includes a congestion state determination unit that determines whether the base station is in a congestion state; a barring target setting unit that sequentially sets targets of barring among a plurality of the targets of the barring when a determination is made that it is the congestion state; a barring time interval setting unit that sets a time interval of the barring based on the congestion state when the determination is made that it is the congestion state; and a transmitter that transmits information representing the targets of the barring and information representing the time interval of the barring to the user equipment.