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Showing papers on "Base station published in 2011"


Journal ArticleDOI
Zhouyue Pi1, Farooq Khan1
TL;DR: This article introduces a millimeter-wave mobile broadband (MMB) system as a candidate next generation mobile communication system and demonstrates the feasibility for MMB to achieve gigabit-per-second data rates at a distance up to 1 km in an urban mobile environment.
Abstract: Almost all mobile communication systems today use spectrum in the range of 300 MHz-3 GHz. In this article, we reason why the wireless community should start looking at the 3-300 GHz spectrum for mobile broadband applications. We discuss propagation and device technology challenges associated with this band as well as its unique advantages for mobile communication. We introduce a millimeter-wave mobile broadband (MMB) system as a candidate next generation mobile communication system. We demonstrate the feasibility for MMB to achieve gigabit-per-second data rates at a distance up to 1 km in an urban mobile environment. A few key concepts in MMB network architecture such as the MMB base station grid, MMB interBS backhaul link, and a hybrid MMB + 4G system are described. We also discuss beamforming techniques and the frame structure of the MMB air interface.

2,487 citations


Journal ArticleDOI
TL;DR: The most important addenda of the proposed E3F are a sophisticated power model for various base station types, as well as large-scale long-term traffic models, which are applied to quantify the energy efficiency of the downlink of a 3GPP LTE radio access network.
Abstract: In order to quantify the energy efficiency of a wireless network, the power consumption of the entire system needs to be captured. In this article, the necessary extensions with respect to existing performance evaluation frameworks are discussed. The most important addenda of the proposed energy efficiency evaluation framework (E3F) are a sophisticated power model for various base station types, as well as large-scale long-term traffic models. The BS power model maps the RF output power radiated at the antenna elements to the total supply power of a BS site. The proposed traffic model emulates the spatial distribution of the traffic demands over large geographical regions, including urban and rural areas, as well as temporal variations between peak and off-peak hours. Finally, the E3F is applied to quantify the energy efficiency of the downlink of a 3GPP LTE radio access network.

1,462 citations


Journal ArticleDOI
TL;DR: The paper shows that the precoding matrix used by the base station in one cell becomes corrupted by the channel between that base station and the users in other cells in an undesirable manner and develops a new multi-cell MMSE-based precoding method that mitigates this problem.
Abstract: This paper considers a multi-cell multiple antenna system with precoding used at the base stations for downlink transmission. Channel state information (CSI) is essential for precoding at the base stations. An effective technique for obtaining this CSI is time-division duplex (TDD) operation where uplink training in conjunction with reciprocity simultaneously provides the base stations with downlink as well as uplink channel estimates. This paper mathematically characterizes the impact that uplink training has on the performance of such multi-cell multiple antenna systems. When non-orthogonal training sequences are used for uplink training, the paper shows that the precoding matrix used by the base station in one cell becomes corrupted by the channel between that base station and the users in other cells in an undesirable manner. This paper analyzes this fundamental problem of pilot contamination in multi-cell systems. Furthermore, it develops a new multi-cell MMSE-based precoding method that mitigates this problem. In addition to being linear, this precoding method has a simple closed-form expression that results from an intuitive optimization. Numerical results show significant performance gains compared to certain popular single-cell precoding methods.

1,306 citations


Journal ArticleDOI
TL;DR: The technical background to the VCE Green Radio project is discussed, models of current energy consumption in base station devices are discussed and some of the most promising research directions in reducing the energy consumption of future base stations are described.
Abstract: Recent analysis by manufacturers and network operators has shown that current wireless networks are not very energy efficient, particularly the base stations by which terminals access services from the network. In response to this observation the Mobile Virtual Centre of Excellence (VCE) Green Radio project was established in 2009 to establish how significant energy savings may be obtained in future wireless systems. This article discusses the technical background to the project and discusses models of current energy consumption in base station devices. It also describes some of the most promising research directions in reducing the energy consumption of future base stations.

793 citations


Journal ArticleDOI
TL;DR: It is discussed how dynamic operation of cellular base stations, in which redundant base stations are switched off during periods of low traffic such as at night, can provide significant energy savings, and quantitatively estimate these potential savings through a first-order analysis.
Abstract: The operation of cellular network infrastructure incurs significant electrical energy consumption. From the perspective of cellular network operators, reducing this consumption is not only a matter of showing environmental responsibility, but also of substantially reducing their operational expenditure. We discuss how dynamic operation of cellular base stations, in which redundant base stations are switched off during periods of low traffic such as at night, can provide significant energy savings. We quantitatively estimate these potential savings through a first-order analysis based on real cellular traffic traces and information regarding base station locations in a part of Manchester, United Kingdom. We also discuss a number of open issues pertinent to implementing such energy-efficient dynamic base station operation schemes, such as various approaches to ensure coverage, and interoperator coordination.

587 citations


Patent
30 Mar 2011
TL;DR: This paper considers the case of two cognitive users and shows how the inherent asymmetry in the network can be exploited to increase the probability of detection and proposes a practical algorithm which allows cooperation in random networks.
Abstract: Providing for cooperative sensing in wireless communications that improves user terminal throughput and minimizes interference is described herein. According to some aspects, a network entity, such as a base station, can assign a set of SUTs to measure a subset of wireless channels in a target frequency according to a cooperative sensing arrangement. In particular aspects, this assignment can be implemented so as to increase or maximize potential traffic throughput of those SUTs within the target frequency, in a given wireless time slot. In this manner, cooperative sensing can be structured so as to provide more efficient traffic communications within the target frequency.

413 citations


Journal ArticleDOI
TL;DR: This paper develops an algorithm for optimizing the performance of the ground-to-relay links through control of the UAV heading angle, and proposes a smart handoff algorithm that updates node and relay assignments as the topology of the network evolves.
Abstract: In this paper, we investigate a communication system in which unmanned aerial vehicles (UAVs) are used as relays between ground-based terminals and a network base station. We develop an algorithm for optimizing the performance of the ground-to-relay links through control of the UAV heading angle. To quantify link performance, we define the ergodic normalized transmission rate (ENTR) for the links between the ground nodes and the relay, and derive a closed-form expression for it in terms of the eigenvalues of the channel correlation matrix. We show that the ENTR can be approximated as a sinusoid with an offset that depends on the heading of the UAV. Using this observation, we develop a closed-form expression for the UAV heading that maximizes the uplink network data rate while keeping the rate of each individual link above a certain threshold. When the current UAV relay assignments cannot meet the minimum link requirements, we investigate the deployment and heading control problem for new UAV relays as they are added to the network, and propose a smart handoff algorithm that updates node and relay assignments as the topology of the network evolves.

378 citations


Patent
14 Feb 2011
TL;DR: In this article, a system and method of receiving a channel state information reference signal (CSI-RS) is presented, where a first CSI-RS transmitted from a base station is received at a first periodicity using a first set of antenna ports.
Abstract: A system and method of receiving a channel state information reference signal (CSI-RS) is presented. At a user equipment, a first CSI-RS transmitted from a base station is received. In some implementations, the first CSI-RS is transmitted at a first periodicity using a first set of antenna ports. At the user equipment, a second CSI-RS transmitted from the base station is received. In some implementations, the second CSI-RS is transmitted at a second periodicity using a second set of antenna ports. At least one of the first CSI-RS and the second CSI-RS is used to perform channel measurement.

374 citations


Proceedings ArticleDOI
01 Dec 2011
TL;DR: It is shown that orthogonality improves with increasing number of antennas, but for two single-antenna users there is very little improvement beyond 20 antennas, and sum-rate performance for two linear pre-coding schemes, zero-forcing (ZF) and minimum mean squared error (MMSE), as a function of the number of base station antennas.
Abstract: Wireless communication using very-large multiple-input multiple-output (MIMO) antennas is a new research field, where base stations are equipped with a very large number of antennas as compared to previously considered systems. In theory, as the number of antennas increases, propagation properties that were random before start to become deterministic. Theoretical investigations with independent identically distributed (i.i.d.) complex Gaussian (Rayleigh fading) channels and unlimited number of antennas have been done, but in practice we need to know what benefits we can get from very large, but limited, number of antenna elements in realistic propagation environments. In this study we evaluate properties of measured residential-area channels, where the base station is equipped with 128 antenna ports. An important property to consider is the orthogonality between channels to different users, since this property tells us how advanced multi-user MIMO (MU-MIMO) pre-coding schemes we need in the downlink. We show that orthogonality improves with increasing number of antennas, but for two single-antenna users there is very little improvement beyond 20 antennas. We also evaluate sum-rate performance for two linear pre-coding schemes, zero-forcing (ZF) and minimum mean squared error (MMSE), as a function of the number of base station antennas. Already at 20 base station antennas these linear pre-coding schemes reach 98% of the optimal dirty-paper coding (DPC) capacity for the measured channels.

298 citations


Journal ArticleDOI
TL;DR: A coordinated beamforming approach whereby multiple base stations jointly optimize their downlink beamforming vectors in order to simultaneously improve the data rates of a given group of cell edge users is considered.
Abstract: In a cellular wireless system, users located at cell edges often suffer significant out-of-cell interference. Assuming each base station is equipped with multiple antennas, we can model this scenario as a multiple-input single-output (MISO) interference channel. In this paper we consider a coordinated beamforming approach whereby multiple base stations jointly optimize their downlink beamforming vectors in order to simultaneously improve the data rates of a given group of cell edge users. Assuming perfect channel knowledge, we formulate this problem as the maximization of a system utility (which balances user fairness and average user rates), subject to individual power constraints at each base station. We show that, for the single-carrier case and when the number of antennas at each base station is at least two, the optimal coordinated beamforming problem is NP-hard for both the harmonic mean utility and the proportional fairness utility. For general utilities, we propose a cyclic coordinate descent algorithm, which enables each transmitter to update its beamformer locally with limited information exchange and establish its global convergence to a stationary point. We illustrate its effectiveness in computer simulations by using the space matched beamformer as the benchmark.

284 citations


Proceedings ArticleDOI
01 Nov 2011
TL;DR: A characterization of full-duplex performance in the context of a base station transmitting to one device while receiving from another is presented and shows that at 10 m distance and with 12 dBm transmit power the gains over half-duple are as high as 90% and no lower than 60% as long as the directional antennas at the base station are separated by 45° or more.
Abstract: The use of directional antennas in wireless networks has been widely studied with two main motivations: 1) decreasing interference between devices and 2) improving power efficiency We identify a third motivation for utilizing directional antennas: pushing the range limitations of full-duplex wireless communication A characterization of full-duplex performance in the context of a base station transmitting to one device while receiving from another is presented In this scenario, the base station can exploit “directional diversity” by using directional antennas to achieve additional passive suppression of the self-interference The characterization shows that at 10 m distance and with 12 dBm transmit power the gains over half-duplex are as high as 90% and no lower than 60% as long as the directional antennas at the base station are separated by 45° or more At 15 m distance the gains are no lower than 40% for separations of 90° and larger Passive suppression via directional antennas also allows full-duplex to achieve significant gains over half-duplex even without resorting to the use of extra hardware for performing RF cancellation as has been required in the previous work

Journal ArticleDOI
TL;DR: Several downlink multiuser multiple input multiple output (MIMO) DAS strategies are proposed and compared in terms of per-user throughput and area spectral efficiency and approximations of the ergodic rate are proposed to facilitate rapid simulation and design space exploration.
Abstract: Distributed antenna systems (DAS) augment the base station's transmit capability by adding multiple remote radio units, connected to the base station via a high bandwidth and low latency link. With DAS, the base station operates as if it had multiple antennas, but the antennas happen to be in different geographic locations. DAS have been shown to enhance coverage and capacity in cellular systems, in a variety of different configurations. This paper proposes, analyzes, and compares several downlink multiuser multiple input multiple output (MIMO) DAS strategies in terms of per-user throughput and area spectral efficiency. Zero-forcing transmit beamforming is used for transmission, the remote radio units may have one or more antennas, and the subscriber has a single receive antenna. Techniques considered include beamforming across all remote radio units (full transmission), using the same beamforming vector for each remote radio unit (simplified transmission), and selecting a subset of remote radio units. To facilitate rapid simulation and design space exploration, approximations of the ergodic rate are proposed for each technique assuming path-loss, small-scale Rayleigh fading, and out-of-cell interference. Simulations accounting for multiple interfering cells are used to compare the different transmission techniques. Full transmission is found to have the best performance even accounting for out-of-cell interference, though gains diminish for higher numbers of active users. Simplified transmission improves over no DAS but performance degrades with more active remote radio units.

Patent
11 Feb 2011
TL;DR: In this article, the authors consider the use of multiple base stations for transmission to user equipment in order to improve the band-with if a UE is on a cell edge, or may be split by user equipment for transmissions to multiple BSs in a wireless communications network.
Abstract: Splitting data in a wireless communications network. Data may be split to use multiple base stations for transmission to user equipment in order to improve the bandwith if a UE is on a cell edge, or may be split by user equipment for transmission to multiple base stations in order to improve handover. Data splitting may be performed at the Packet Data Convergence Protocol layer, at the Radio Link Control layer, or at the Media Access Control layer on user equipment or on a base station. Data may instead be split in a network node, such as in a serving gateway, in order to reduce X2 interface load or delay carrier aggregation.

Patent
16 Mar 2011
TL;DR: In this paper, a method and apparatus for transmitting and receiving a CSI-Reference Signal (CSI-RS) in a wireless communication system supporting multiple antennas is described, which includes transmitting, at a base station, information of one or more CSI-RS configurations to a mobile station.
Abstract: A method and apparatus for transmitting and receiving a Channel State Information-Reference Signal (CSI-RS) in a wireless communication system supporting multiple antennas are disclosed. The method includes transmitting, at a base station, information of one or more CSI-RS configurations to a mobile station, wherein the one or more CSI-RS configurations include one CSI-RS configuration for which the mobile station assumes non-zero transmission power for CSI-RS, transmitting, at the base station, information indicating a CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS among the one or more CSI-RS configurations to the mobile station, mapping, at the base station, CSI-RSs to resource elements of a downlink subframe based on the one or more CSI-RS configurations, and transmitting, at the base station, the downlink subframe mapped with the CSI-RSs to the mobile station.

Proceedings ArticleDOI
01 Dec 2011
TL;DR: A distributed suboptimal joint mode selection and resource allocation scheme is proposed that performs close to the optimal scheme both in terms of resource efficiency and user fairness and is benchmarked with respect to the centralized optimal solution.
Abstract: Device-to-device (D2D) communications underlaying a cellular infrastructure has recently been proposed as a means of increasing the cellular capacity, improving the user throughput and extending the battery lifetime of user equipments by facilitating the reuse of spectrum resources between D2D and cellular links. In network assisted D2D communications, when two devices are in the proximity of each other, the network can not only help the devices to set the appropriate transmit power and schedule time and frequency resources but also to determine whether communication should take place via the direct D2D link (D2D mode) or via the cellular base station (cellular mode). In this paper we formulate the joint mode selection, scheduling and power control task as an optimization problem that we first solve assuming the availability of a central entity. We also propose a distributed suboptimal joint mode selection and resource allocation scheme that we benchmark with respect to the centralized optimal solution. We find that the distributed scheme performs close to the optimal scheme both in terms of resource efficiency and user fairness.

Proceedings ArticleDOI
15 May 2011
TL;DR: The necessary enhancements over existing performance evaluation frameworks are discussed, such that the energy efficiency of the entire network comprising component, node and network level contributions can be quantified.
Abstract: In order to quantify the energy savings in wireless networks, the power consumption of the entire system needs to be captured and an appropriate energy efficiency evaluation framework must be defined. In this paper, the necessary enhancements over existing performance evaluation frameworks are discussed, such that the energy efficiency of the entire network comprising component, node and network level contributions can be quantified. The most important addendums over existing frameworks include a sophisticated power model for various base station (BS) types, which maps the RF output power radiated at the antenna elements to the total supply power of a BS site. We also consider an approach to quantify the energy efficiency of large geographical areas by using the existing small scale deployment models along with long term traffic models. Finally, the proposed evaluation framework is applied to quantify the energy efficiency of the downlink of a 3GPP LTE radio access network.

Patent
Wei-Peng Chen1
03 Feb 2011
TL;DR: In this paper, a method for deploying a wireless network in accordance with particular embodiments includes deploying one or more base stations configured to provide wireless connections between the one/more base stations and one/ more endpoints.
Abstract: A method for deploying a wireless network in accordance with particular embodiments includes deploying one or more base stations configured to provide wireless connections between the one or more base stations and one or more endpoints. The method also includes deploying one or more remote transceivers configured to provide wireless connections between the one or more remote transceivers and one or more endpoints. The method further includes modifying at least one base station of the one or more base stations. The modified base station is configured to control the one or more remote transceivers. The method additionally includes modifying at least one remote transceiver of the one or more remote transceivers. The modified remote transceiver is configured to control the at least one remote transceiver without receiving control information from the at least one base station.

Journal ArticleDOI
TL;DR: Experimental results show that the P2P spatial cloaking algorithm is scalable while guaranteeing the user’s location privacy protection, and a cloaked area adjustment scheme guarantees that the spatial cloaked algorithm is free from a “center-of-cloaked-area” privacy attack.
Abstract: This paper tackles a privacy breach in current location-based services (LBS) where mobile users have to report their exact location information to an LBS provider in order to obtain their desired services. For example, a user who wants to issue a query asking about her nearest gas station has to report her exact location to an LBS provider. However, many recent research efforts have indicated that revealing private location information to potentially untrusted LBS providers may lead to major privacy breaches. To preserve user location privacy, spatial cloaking is the most commonly used privacy-enhancing technique in LBS. The basic idea of the spatial cloaking technique is to blur a user's exact location into a cloaked area that satisfies the user specified privacy requirements. Unfortunately, existing spatial cloaking algorithms designed for LBS rely on fixed communication infrastructure, e.g., base stations, and centralized/distributed servers. Thus, these algorithms cannot be applied to a mobile peer-to-peer (P2P) environment where mobile users can only communicate with other peers through P2P multi-hop routing without any support of fixed communication infrastructure or servers. In this paper, we propose a spatial cloaking algorithm for mobile P2P environments. As mobile P2P environments have many unique limitations, e.g., user mobility, limited transmission range, multi-hop communication, scarce communication resources, and network partitions, we propose three key features to enhance our algorithm: (1) An information sharing scheme enables mobile users to share their gathered peer location information to reduce communication overhead; (2) A historical location scheme allows mobile users to utilize stale peer location information to overcome the network partition problem; and (3) A cloaked area adjustment scheme guarantees that our spatial cloaking algorithm is free from a "center-of-cloaked-area" privacy attack. Experimental results show that our P2P spatial cloaking algorithm is scalable while guaranteeing the user's location privacy protection.

Journal ArticleDOI
TL;DR: This paper proposes a multi-step sensor selection strategy to schedule sensors to transmit for the next T steps of time with the goal of minimizing an objective function related to the Kalman filter error covariance matrix.

Patent
Fu I Kang1, Chao-Chin Chou
14 Mar 2011
TL;DR: In this paper, a method of multi-radio interworking to provide integrated cellular and WLAN access for a multiuser device is provided, where a serving base station in a cellular network first obtains wireless local area network (WLAN) information and then forward the WLAN information to a serving device such that the serving device is capable to connect with both the cellular network and a WLAN.
Abstract: A method of multi-radio interworking to provide integrated cellular and WLAN access for a multi-radio device is provided. A serving base station in a cellular network first obtains wireless local area network (WLAN) information and then forward the WLAN information to a serving device such that the serving device is capable to connect with both the cellular network and a WLAN. The WLAN information may comprise scanning information, WLAN QoS information, WLAN layer-3 information, or additional WLAN access point information. The WLAN information is forwarded based on triggering events associated with the serving base station information, WLAN coverage information, or the serving device information. Based on the received WLAN information, when entering WLAN coverage, the serving device activates its WLAN access to forward traffic from the cellular access network to the WLAN access network. When leaving WLAN coverage, the serving device deactivates its WLAN access to save power consumption.

Patent
Sunghoon Jung1, Sung Duck Chun1, Seung June Yi1, Youngdae Lee1, Sung Jun Park1 
07 Feb 2011
TL;DR: In this paper, a method and apparatus of reporting logged measurements of an user equipment in a wireless communication system is provided, where the user equipment transitions from the RRC connected mode to an RRC idle mode and logs measurements based on the MDT configuration.
Abstract: A method and apparatus of reporting logged measurements of an user equipment in a wireless communication system is provided. The user equipment in a Radio Resource Control (RRC) connected mode receives from a base station a Minimization of Drive Tests (MDT) configuration. The user equipment transitions from the RRC connected mode to an RRC idle mode and logs measurements based on the MDT configuration. The user equipment transmits to the base station a logging indicator indicating an availability of the logged measurement.

Patent
28 Feb 2011
TL;DR: In this paper, a location system is disclosed for commercial wireless telecommunication infrastructures, which is an end-to-end solution having one or more location centers for outputting requested locations of commercially available handsets or mobile stations (MS) based on, eg, CDMA, AMPS, NAMPS or TDMA communication standards.
Abstract: A location system is disclosed for commercial wireless telecommunication infrastructures The system is an end-to-end solution having one or more location centers for outputting requested locations of commercially available handsets or mobile stations (MS) based on, eg, CDMA, AMPS, NAMPS or TDMA communication standards, for processing both local MS location requests and more global MS location requests via, eg, Internet communication between a distributed network of location centers The system uses a plurality of MS locating technologies including those based on: (1) two-way TOA and TDOA; (2) pattern recognition; (3) distributed antenna provisioning; (5) GPS signals, (6) angle of arrival, (7) super resolution enhancements, and (8) supplemental information from various types of very low cost non-infrastructure base stations for communicating via a typical commercial wireless base station infrastructure or a public telephone switching network Accordingly, the traditional MS location difficulties, such as multipath, poor location accuracy and poor coverage are alleviated via such technologies in combination with strategies for: (a) automatically adapting and calibrating system performance according to environmental and geographical changes; (b) automatically capturing location signal data for continual enhancement of a self-maintaining historical data base retaining predictive location signal data; (c) evaluating MS locations according to both heuristics and constraints related to, eg, terrain, MS velocity and MS path extrapolation from tracking and (d) adjusting likely MS locations adaptively and statistically so that the system becomes progressively more comprehensive and accurate Further, the system can be modularly configured for use in location signaling environments ranging from urban, dense urban, suburban, rural, mountain to low traffic or isolated roadways Accordingly, the system is useful for 911 emergency calls, tracking, routing, people and animal location including applications for confinement to and exclusion from certain areas

Journal ArticleDOI
TL;DR: A new limited feedback strategy is proposed for multicell beamforming where cooperation is restricted to sharing only the CSI of active users among base stations, and a new feedback-bit allocation strategy, to partition the available bits between the desired and interfering channels, is developed.
Abstract: Base station cooperation improves the sum-rates that can be achieved in cellular systems. Conventional cooperation techniques require sharing large amounts of information over finite-capacity backhaul links and assume that base stations have full channel state information (CSI) of all the active users in the system. In this paper, a new limited feedback strategy is proposed for multicell beamforming where cooperation is restricted to sharing only the CSI of active users among base stations. The system setup considered is a linear array of cells based on the “soft hand-off model,” where each cell contains single-antenna users and multi-antenna base stations. Beamforming vectors are designed using a generalized eigenvector approach to maximize the sum-rate in a single-interferer scenario, at high signal to noise ratio. Users are assumed to feedback quantized CSI of the desired and interfering channels using a finite-bandwidth feedback link. An upper bound on the mean loss in sum rate due to random vector quantization is derived. A new feedback-bit allocation strategy, to partition the available bits between the desired and interfering channels, is developed to reduce the mean loss in sum-rate due to quantization for the soft hand-off model. The proposed feedback-bit partitioning algorithm is shown, using simulations, to yield sum-rates close to the those obtained using full CSI at base station.

Patent
06 Sep 2011
TL;DR: In this article, the authors present a system to track one or more indoor persons that includes an application server with a first processor, a base station, a plurality of tags, and medical device sensors that include a wireless blood pressure sensor, a wireless temperature measurement sensor, or a wireless heart rate sensor.
Abstract: The present invention is a system to track one or more indoor persons that includes an application server with a first processor, a base station, a plurality of tags, a plurality of medical device sensors that includes a wireless blood pressure sensor, a wireless temperature measurement sensor, or a wireless heart rate sensor with a plurality of predetermined boundary readings that are in communication with the tags, a camera that is in communication with the base station and transmits video or a plurality of picture images to the base station and a mobile device that is in communication with the base station within the system. The system can also be modified to track one or more outdoor persons and one or more new or used vehicles as well.

Journal ArticleDOI
TL;DR: A framework for a total cost analysis is proposed and some recent, more radical, "clean slate" approaches exploiting combinations of new spectrum opportunities, energy-efficient PHY layers, and novel deployment and backhauling strategies that target minimizing overall system cost are surveyed.
Abstract: Mobile communication networks alone today consume 0.5 percent of the global energy supply. Meeting the rapidly increasing demand for more capacity in wireless broadband access will further increase the energy consumption. Operators are now facing both investing in denser and denser networks as well as increased energy cost. Traditional design paradigms, based on assumptions of spectrum shortage and high cost base station sites, have produced current cellular systems based on 3G and 4G (LTE) standards. The latter ones are characterized by very high spectrum efficiency, but low energy efficiency. Deployment has favored strategies with few high-power bases stations with complex antenna systems. The key method for indoor coverage has so far been to literally "blast signals through walls" - a solution that is neither energy-efficient nor very sound from a radiation perspective. As environmental aspects may be perceived as important from a societal perspective, the cost remains the short- to medium-term concern for operators of future mobile broadband systems. What becomes evident now is that the so far mostly neglected energy cost will be a major concern. Future system deployment has to balance infrastructure deployment, spectrum, and energy cost components. Ongoing incremental improvements in electronics and signal processing are bringing down the power consumption in the base station. However, these improvements are not enough to match the orders-of-magnitude increase in energy consumption cause by demands for more capacity. It is clear that solutions to this problem have to be found at the architectural level, not just by increasing the efficiency of individual components. In this article we propose a framework for a total cost analysis and survey some recent, more radical, "clean slate" approaches exploiting combinations of new spectrum opportunities, energy-efficient PHY layers, and novel deployment and backhauling strategies that target minimizing overall system cost. The latter involve network deployment tightly tailored to traffic requirements, using low-power micro base stations tailored specifically to decrease the power consumption compared to today's highpower macro base station schemes. To illustrate our findings, a power consumption model for mobile broadband access networks taking backhaul into account is presented, and the main trade-offs between infrastructure, energy, and spectrum costs are analyzed. We demonstrate optimal deployment strategies in some simple scenarios where a certain capacity has to be provided in a dense interference-limited scenario.

Patent
Inkwon Seo1, Hanbyul Seo1, Byoung-Hoon Kim1, Kijun Kim1, Hakseong Kim1 
29 Mar 2011
TL;DR: In this article, a measurement method and apparatus for inter-cell interference coordination in a wireless communication system is described, which includes the steps of acquiring information of the downlink subframe configuration of a second base station, determining measurement objects of downlink resource of the first base station and transmitting information of measurement objects to the UE, and receiving measurement result for the measurement objects from the UE.
Abstract: A wireless communication system and, more specifically, a measurement method and apparatus for inter-cell interference coordination in a wireless communication system are disclosed. Herein, a method for supporting measurement of a User Equipment (UE) by a first base station in a wireless communication system includes the steps of acquiring information of downlink subframe configuration of a second base station, determining measurement objects of downlink resource of the first base station based on the downlink subframe configuration of the second base station; transmitting information of the measurement objects to the UE, and receiving measurement result for the measurement objects from the UE.

Patent
22 Dec 2011
TL;DR: In this paper, the P2P configuration information from a base station at a UE supporting peer-to-peer (P2P) communication is provided in a system information block (SIB) broadcast by the base station.
Abstract: Configuring a peer-to-peer (P2P) link in a multi-access wireless network includes receiving P2P configuration information from a base station at a UE supporting P2P communication. The first UE communicates directly with a second UE based on the P2P configuration information received from the base station. The first UE may send a configuration request message to the base station, and receive a responsive configuration message with the P2P configuration information from the base station, which messages may be Radio Resource Control (RRC) messages supporting P2P. In the alternative, the P2P configuration information may be provided in a system information block (SIB) broadcast by the base station. The P2P configuration information may indicate allocation of physical layer or Medium Access Control resources, or both allocated for P2P communication, and other information.

Patent
Hanbyul Seo1, Daewon Lee1
20 Dec 2011
TL;DR: In this paper, the authors present a method for reporting channel state information (CSI) in a wireless communication system, and the method performed by a terminal comprises the steps of: receiving, from a base station, a radio resource control (RRC) signaling including control information relating to a configuration of a 12-port CSI-reference signal (RS); receiving from the base station the 12-Port CSI-RS through a 12port CSI reference signal resource on the basis of the received control information; and reporting CSI to the Base Station on the based of the Received CSI-
Abstract: The present specification relates to a method for reporting channel state information (CSI) in a wireless communication system, and the method performed by a terminal comprises the steps of: receiving, from a base station, a radio resource control (RRC) signaling including control information relating to a configuration of a 12-port CSI-reference signal (RS); receiving, from the base station, the 12-port CSI-RS through a 12-port CSI-RS resource on the basis of the received control information; and reporting CSI to the base station on the basis of the received CSI-RS. Therefore, full power transmission per port is enabled in the transmission of a 12-port CSI-RS.

Journal ArticleDOI
TL;DR: This work aims to design linear transceivers that optimize a worst-case QoS measure in downlink transmissions and focuses on maximizing the worst- Case weighted sum-rate of the network and the minimum worst- case rate of thenetwork.
Abstract: Coordinated information processing by the base stations of multi-cell wireless networks enhances the overall quality of communication in the network. Such coordinations for optimizing any desired network-wide quality of service (QoS) necessitate the base stations to acquire and share some channel state information (CSI). With perfect knowledge of channel states, the base stations can adjust their transmissions for achieving a network-wise QoS optimality. In practice, however, the CSI can be obtained only imperfectly. As a result, due to the uncertainties involved, the network is not guaranteed to benefit from a globally optimal QoS. Nevertheless, if the channel estimation perturbations are confined within bounded regions, the QoS measure will also lie within a bounded region. Therefore, by exploiting the notion of robustness in the worst-case sense some worst-case QoS guarantees for the network can be asserted. We adopt a popular model for noisy channel estimates that assumes that estimation noise terms lie within known hyper-spheres. We aim to design linear transceivers that optimize a worst-case QoS measure in downlink transmissions. In particular, we focus on maximizing the worst-case weighted sum-rate of the network and the minimum worst-case rate of the network. For obtaining such transceiver designs, we offer several centralized (fully cooperative) and distributed (limited cooperation) algorithms which entail different levels of complexity and information exchange among the base stations.

Patent
Hyojin Lee1, Kim Youn Sun1, Joon-Young Cho1, Ju-Ho Lee1, Jin Kyu Han1, Young-Bum Kim1 
17 Nov 2011
TL;DR: In this article, an uplink power control method and apparatus of a terminal in a mobile communication system are provided, which includes receiving, by the terminal, a location parameter corresponding to at least one antenna selected among a plurality of antennas distributed in a service area of a base station, each of which being connected to the base station.
Abstract: An uplink power control method and apparatus of a terminal in a mobile communication system are provided. The method includes receiving, by the terminal, a location parameter corresponding to at least one antenna selected among a plurality of antennas distributed in a service area of a base station, each of the plurality of antennas being connected to the base station; and calculating uplink power based on the location parameter.