Showing papers on "Base station published in 2010"

Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas

Abstract: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.

Power consumption modeling of different base station types in heterogeneous cellular networks

Abstract: In wireless communications micro cells are potentially more energy efficient than conventional macro cells due to the high path loss exponent. Also, heterogeneous deployments of both cell types can be used to optimize the energy efficiency. Energy efficiency of any deployment is impacted by the power consumption of each individual network element and the dependency of transmit power and load. In this paper we developed such power models for macro and micro base stations relying on data sheets of several GSM and UMTS base stations with focus on component level, e.g., power amplifier and cooling equipment. In a first application of the model a traditional macro cell deployment and a heterogeneous deployment are compared.

Challenges and enabling technologies for energy aware mobile radio networks

Abstract: Mobile communications are increasingly contributing to global energy consumption. In this article, a holistic approach for energy efficient mobile radio networks is presented. The matter of having appropriate metrics and evaluation methods that allow assessing the energy efficiency of the entire system is discussed. The mutual supplementary saving concepts comprise component, link and network levels. At the component level the power amplifier complemented by a transceiver and a digital platform supporting advanced power management are key to efficient radio implementations. Discontinuous transmission by base stations, where hardware components are switched off, facilitate energy efficient operation at the link level. At the network level, the potential for reducing energy consumption is in the layout of networks and their management, that take into account slowly changing daily load patterns, as well as highly dynamic traffic fluctuations. Moreover, research has to analyze new disruptive architectural approaches, including multi-hop transmission, ad-hoc meshed networks, terminal-to-terminal communications, and cooperative multipoint architectures.

Fiber-Wireless Networks and Subsystem Technologies

Abstract: Hybrid fiber-wireless networks incorporating WDM technology for fixed wireless access operating in the sub-millimeter-wave and millimeter-wave (mm-wave) frequency regions are being actively pursued to provide untethered connectivity for ultrahigh bandwidth communications. The architecture of such radio networks requires a large number of antenna base-stations with high throughput to be deployed to maximize the geographical coverage with the main switching and routing functionalities located in a centralized location. The transportation of mm-wave wireless signals within the hybrid network is subject to several impairments including low opto-electronic conversion efficiency, fiber chromatic dispersion and also degradation due to nonlinearities along the link. One of the major technical challenges in implementing such networks lies in the mitigation of these various optical impairments that the wireless signals experience within the hybrid network. In this paper, we present an overview of different techniques to optically transport mm-wave wireless signals and to overcome impairments associated with the transport of the wireless signals. We also review the different designs of subsystems for integrating fiber-wireless technology onto existing optical infrastructure.

Radio Over Fiber Link Design for Next Generation Wireless Systems

Abstract: The performance of radio over fiber (RoF) links using low cost optoelectronic components is assessed for distributed antenna applications in next generation wireless systems Important design issues are discussed and an example link design is presented for a wireless system requiring the transmission of four radio channels per link direction, each with 100 MHz bandwidth, modulation complexity of 256-QAM and 2048 OFDM subcarriers We show that the noise introduced by the RoF links does not have a significant impact on wireless range, provided the wireless system has uplink power control Finally, we compare the cost and performance of RoF links for this application with alternative link types that use digitized radio transmission and show that RoF is the optimum choice from a cost perspective

Cooperative Multicell Precoding: Rate Region Characterization and Distributed Strategies With Instantaneous and Statistical CSI

Abstract: Base station cooperation is an attractive way of increasing the spectral efficiency in multiantenna communication. By serving each terminal through several base stations in a given area, intercell interference can be coordinated and higher performance achieved, especially for terminals at cell edges. Most previous work in the area has assumed that base stations have common knowledge of both data dedicated to all terminals and full or partial channel state information (CSI) of all links. Herein, we analyze the case of distributed cooperation where each base station has only local CSI, either instantaneous or statistical. In the case of instantaneous CSI, the beamforming vectors that can attain the outer boundary of the achievable rate region are characterized for an arbitrary number of multiantenna transmitters and single-antenna receivers. This characterization only requires local CSI and justifies distributed precoding design based on a novel virtual signal-to-interference noise ratio (SINR) framework, which can handle an arbitrary SNR and achieves the optimal multiplexing gain. The local power allocation between terminals is solved heuristically. Conceptually, analogous results for the achievable rate region characterization and precoding design are derived in the case of local statistical CSI. The benefits of distributed cooperative transmission are illustrated numerically, and it is shown that most of the performance with centralized cooperation can be obtained using only local CSI.

Enhancing cell-edge performance: a downlink dynamic interference avoidance scheme with inter-cell coordination

Abstract: Interference management has been a key concept for designing future high data-rate wireless systems that are required to employ dense reuse of spectrum. Static or semi-static interference coordination based schemes provide enhanced cell-edge performance but with severe penalty to the overall cell throughput. Furthermore, static resource planning makes these schemes unsuitable for applications in which frequency planning is difficult, such as femtocell networks. In this paper, we present a novel dynamic interference avoidance scheme that makes use of inter-cell coordination in order to prevent excessive inter-cell interference, especially for cell or sector edge users that are most affected by inter-cell interference, with minimal or no impact on the network throughput. The proposed scheme is comprised of a two-level algorithm - one at the base station level and the other at a central controller to which a group of neighboring base stations are connected. Simulation results show that the proposed scheme outperforms the reference schemes, in which either coordination is not employed (reuse of 1) or employed in a static manner (reuse of 3 and fractional frequency reuse), in terms of cell edge throughput with a minimal impact on the network throughput and with some increase in complexity.

Cooperative Interference Management With MISO Beamforming

Abstract: In this correspondence, we study the downlink transmission in a multi-cell system, where multiple base stations (BSs) each with multiple antennas cooperatively design their respective transmit beamforming vectors to optimize the overall system performance. For simplicity, it is assumed that all mobile stations (MSs) are equipped with a single antenna each, and there is one active MS in each cell at one time. Accordingly, the system of interests can be modeled by a multiple-input single-output (MISO) Gaussian interference channel (IC), termed as MISO-IC, with interference treated as noise. We propose a new method to characterize different rate-tuples for active MSs on the Pareto boundary of the achievable rate region for the MISO-IC, by exploring the relationship between the MISO-IC and the cognitive radio (CR) MISO channel. We show that each Pareto-boundary rate-tuple of the MISO-IC can be achieved in a decentralized manner when each of the BSs attains its own channel capacity subject to a certain set of interference-power constraints (also known as interference-temperature constraints in the CR system) at the other MS receivers. Furthermore, we show that this result leads to a new decentralized algorithm for implementing the multi-cell cooperative downlink beamforming.

Energy Savings through Dynamic Base Station Switching in Cellular Wireless Access Networks

Abstract: Reducing the energy consumption of cellular wireless access networks is not only beneficial for the global environment but also makes commercial sense for telecommunication operators. Since access networks are designed to support peak time traffic, the utilization of base stations can be very inefficient during off-peak time because the traffic profile is time varying. We study the dynamic switching of base stations (BS) to reduce the energy consumption considering the time varying characteristic of the traffic profile. We show via analysis that the mean and variance of traffic profile and the BS density are the dominant factors that determine the amount of energy saving that can be achieved. Simulations using ideal and real traffic profiles are used to quantify the potential savings from dynamic BS switching in a realistic setting.

MR-LEACH: Multi-hop Routing with Low Energy Adaptive Clustering Hierarchy

Abstract: In this paper, we present a Multi-hop Routing with Low Energy Adaptive Clustering Hierarchy (MR-LEACH) protocol. In order to prolong the lifetime of Wireless Sensor Network (WSN), MR-LEACH partitions the network into different layers of clusters. Cluster heads in each layer collaborates with the adjacent layers to transmit sensor’s data to the base station. Ordinary sensor nodes join cluster heads based on the Received Signal Strength Indicator (RSSI). The transmission of nodes is controlled by a Base Station (BS) that defines the Time Division Multiple Access (TDMA) schedule for each cluster-head. BS selects the upper layers cluster heads to act as super cluster heads for lower layer cluster heads. Thus, MR-LEACH follows multi-hop routing from cluster-heads to a base station to conserve energy, unlike the LEACH protocol. Performance evaluation has shown that MR-LEACH achieves significant improvement in the LEACH protocol and provides energy efficient routing for WSN.

Coordinated linear beamforming in downlink multi-cell wireless networks

Abstract: We consider a multi-cell wireless network with universal frequency reuse and treat the problem of co-channel interference mitigation in the downlink channel. Assuming that each base station serves multiple single-antenna mobiles via space-division multiple-access, we jointly optimize the linear beam-vectors across a set of coordinated cells and resource slots: the objective function to be maximized is the instantaneous weighted sum-rate subject to per-base-station power constraints. After deriving the general structure of the optimal beam-vectors, a novel iterative algorithm is presented which attempts to solve the Karush-Kuhn-Tucker conditions of the non-convex problem at hand. The proposed algorithm admits a distributed implementation which we illustrate. Also, various approaches to choose the initial beam-vectors are considered, one of which maximizes the signal-to-leakage-plus-noise ratio. Finally, simulation results are provided to assess the performance of the proposed algorithm.

Self-contained wireless camera device, wireless camera system and method

Abstract: A self-contained wireless camera ( 10 ) and a wireless camera system ( 25 ) having such a device and a base station ( 20 ). Video processing (e.g. video compression) circuitry ( 200, 210 ) of the camera device receives video signals from a camera ( 130 ) and provides processed video signals. These are transmitted over a shared radio channel. A radio receiver ( 101 ) receives processed (e.g. compressed) video signals from the base station or another camera device. Images from the camera or the base station are displayed in a selected manner on a display or monitor ( 140 ). The base station device ( 20 ) receives processed (e.g. compressed) video signals, stores them and retransmits them. A command signal is received by the radio receiver to modify operation in such a manner as to control bandwidth usage. Wireless camera devices can adjust their operation to accommodate other wireless camera devices. Different transport protocol modules 230 and 240 can be selected according to the application that the user selects for operation.

Self-configuration and self-optimization for LTE networks

Abstract: With the rapid growth of mobile communications, deployment and maintenance of cellular mobile networks are becoming more and more complex, time consuming, and expensive. In order to meet the requirements of network operators and service providers, the telecommunication industry and international standardization bodies have recently paid intensive attention to the research and development of self-organizing networks. In this article we first introduce both the market and technological perspectives for SONs. Then we focus on the self-configuration procedure and illustrate a self-booting mechanism for a newly added evolved NodeB without a dedicated backhaul interface. Finally, mobility load balancing as one of the most important selfoptimization issues for Long Term Evolution networks is discussed, and a distributed MLB algorithm with low handover cost is proposed and evaluated.

A method and apparatus for mimo repeater chains in a wireless communication network

Abstract: In one or more embodiments taught herein, a multi-band MIMO repeater is configured to translate normal wireless mobile bands into other frequency bands in the physical layer. An advantageous, multi-hop repeater chain includes two or more such repeaters, for propagating downlink signals from a base station, and for propagating uplink signals to the base station. Each such repeater may use paralleled homodyne structure transceivers for better SNR, spectrum combiners for uplink signal aggregation, spectrum separators for downlink signal de-aggregation, water mark signal inserters for optimization, and, among other things, spectrum analyzers for frequency band selection. In at least one such embodiment, a multi-hop repeater chain is configured for MIMO operation in an LTE Advanced or other MIMO network, to deliver high data rate over larger distances — e.g., further away from cell base stations.

Developed Distributed Energy-Efficient Clustering (DDEEC) for heterogeneous wireless sensor networks

Abstract: Typically, a wireless sensor network contains an important number of inexpensive power constrained sensors, which collect data from the environment and transmit them towards the base station in a cooperative way. Saving energy and therefore, extending the wireless sensor networks lifetime, imposes a great challenge. Clustering techniques are largely used for these purposes. In this paper, we propose and evaluate a clustering technique called a Developed Distributed Energy-Efficient Clustering scheme for heterogeneous wireless sensor networks. This technique is based on changing dynamically and with more efficiency the cluster head election probability. Simulation results show that our protocol performs better than the Stable Election Protocol (SEP) by about 30% and than the Distributed Energy-Efficient Clustering (DEEC) by about 15% in terms of network lifetime and first node dies.

Energy-Efficient Wake-Up Scheduling for Data Collection and Aggregation

Abstract: A sensor in wireless sensor networks (WSNs) periodically produces data as it monitors its vicinity. The basic operation in such a network is the systematic gathering (with or without in-network aggregation) and transmitting of sensed data to a base station for further processing. A key challenging question in WSNs is to schedule nodes' activities to reduce energy consumption. In this paper, we focus on designing energy-efficient protocols for low-data-rate WSNs, where sensors consume different energy in different radio states (transmitting, receiving, listening, sleeping, and being idle) and also consume energy for state transition. We use TDMA as the MAC layer protocol and schedule the sensor nodes with consecutive time slots at different radio states while reducing the number of state transitions. We prove that the energy consumption by our scheduling for homogeneous network is at most twice of the optimum and the timespan of our scheduling is at most a constant times of the optimum. The energy consumption by our scheduling for heterogeneous network is at most ? (log Rmax/Rmin) times of the optimum. We also propose effective algorithms to construct data gathering tree such that the energy consumption and the network throughput is within a constant factor of the optimum. Extensive simulation studies show that our algorithms do considerably reduce energy consumption.

A practical wireless charging system based on ultra-wideband retro-reflective beamforming

Abstract: Numerous portable electronic devices (such as laptops, cell phones, digital cameras, and electric shavers) rely on rechargeable batteries and must be routinely charged by the line power. A wireless charging technique capable of delivering electromagnetic energy to these portable devices would make them tether free and “truly portable.” Wireless charging is especially valuable for devices with which wired connections are intractable, e.g., unattended radio frequency identification tags and implanted sensors. In recent years, enormous research efforts have been devoted to wireless charging. In 1990s, a case study is reported in [1] to construct a point-to-point wireless electricity transmission to a small isolated village called Grand-Bassin in France. In 2007, an inductive resonance coupling scheme, which makes use of near-field coupling between two magnetic resonators, was demonstrated able to power a 60-Watt light bulb over two meters by a team of Massachusetts Institute of Technology [2]. In addition, several companies (PowerCast, WildCharge, WiPower, etc.) have developed products targeting specific applications. Nevertheless, several technical challenges remain to be resolved in order to accomplish practical wireless charging. Specifically, (i) to achieve efficient charging over long distance, severe power loss due to electromagnetic wave propagation must be remedied; (ii) humans' exposure to electromagnetic radiation should always be kept below safety level while sufficient power is delivered to devices; and (iii) some existing systems are unsuitable for ubiquitous deployment due to high cost, large size, and/or heavy weight. In this paper, an innovative wireless charging system based on ultrawideband retro-reflective beamforming is proposed to address the above challenges. The proposed charger consists of multiple antenna elements distributed in space. According to pilot signals (which are short impulses) they receive from the target device, the antenna elements jointly construct a focused electromagnetic beam onto the device (i.e., beamforming). Beamforming enables spatially focused/dedicated power delivery to devices while keeping power level in all the other locations minimal. As a result, the proposed system attains high charging efficiency and leads to little hazard/interference to other objects. Performance of the proposed wireless charging system is demonstrated by some simulation results obtained by a full-wave Maxwell's equations solver.

Mobile communication system

Abstract: A mobile communication system including a plurality of base stations includes a radio communicator for communicating with mobile terminal devices with a plurality of carriers, and a communication controller for changing radio field intensity of the radio communicator; and a management device including: a storage for storing information of each of the base stations, the information including time slots and a number of registration requests from the mobile terminal devices in each communication area of the base station in accordance with the time slots, and an instructor for instructing to change radio field intensity of the plurality of carriers to the radio communicator in the base stations on the bases of the stored information in the storage when the number of the registration requests in the time slot exceed a specified predetermined threshold value.

Improving Energy Efficiency of Femtocell Base Stations Via User Activity Detection

Abstract: Femtocells, which operate in licensed spectrum and provide improved cellular coverage inside homes and offices, have attracted significant interest in the wireless industry. As a result, an extensive deployment of femtocells is expected in the near future. One prime concern with a large-scale femtocell deployment is the resultant substantial energy consumption. In this paper, we address this issue by proposing a novel energy saving procedure which allows the femtocell base station (BS) to completely switch off its radio transmissions and associated processing when not involved in an active call. The results indicate that based on a certain voice traffic model, the proposed procedure introduces an average reduction of approximately 37.5% in the femtocell's power consumption. Moreover, for a high femtocell traffic scenario, a fivefold reduction in the occurrence of mobility events can also be achieved, compared to a fixed pilot transmit power strategy.

Constrained relay node placement in wireless sensor networks: formulation and approximations

Abstract: One approach to prolong the lifetime of a wireless sensor network (WSN) is to deploy some relay nodes to communicate with the sensor nodes, other relay nodes, and the base stations. The relay node placement problem for wireless sensor networks is concerned with placing a minimum number of relay nodes into a wireless sensor network to meet certain connectivity or survivability requirements. Previous studies have concentrated on the unconstrained version of the problem in the sense that relay nodes can be placed anywhere. In practice, there may be some physical constraints on the placement of relay nodes. To address this issue, we study constrained versions of the relay node placement problem, where relay nodes can only be placed at a set of candidate locations. In the connected relay node placement problem, we want to place a minimum number of relay nodes to ensure that each sensor node is connected with a base station through a bidirectional path. In the survivable relay node placement problem, we want to place a minimum number of relay nodes to ensure that each sensor node is connected with two base stations (or the only base station in case there is only one base station) through two node-disjoint bidirectional paths. For each of the two problems, we discuss its computational complexity and present a framework of polynomial time O(1) -approximation algorithms with small approximation ratios. Extensive numerical results show that our approximation algorithms can produce solutions very close to optimal solutions.

Power Control and Channel Allocation in Cognitive Radio Networks with Primary Users' Cooperation

Abstract: We consider a point-to-multipoint cognitive radio network that shares a set of channels with a primary network. Within the cognitive radio network, a base station controls and supports a set of fixed-location wireless subscribers. The objective is to maximize the throughput of the cognitive network while not affecting the performance of primary users. Both downlink and uplink transmission scenarios in the cognitive network are considered. For both scenarios, we propose two-phase mixed distributed/centralized control algorithms that require minimal cooperation between cognitive and primary devices. In the first phase, a distributed power updating process is employed at the cognitive and primary nodes to maximize the coverage of the cognitive network while always maintaining the constrained signal to interference plus noise ratio of primary transmissions. In the second phase, centralized channel assignment is carried out within the cognitive network to maximize its throughput. Numerical results are obtained for the behaviors and performance of our proposed algorithms.

Pilot Contamination Reduction in Multi-User TDD Systems

Abstract: This paper considers the problem of interference mitigation in multi-cell multi-antenna time division duplex (TDD) wireless systems for downlink transmission. An efficient way to obtain channel state information (CSI) at the base station is by using uplink pilots and reciprocity of the downlink channel. At the same time, it has been shown that pilots from different cells contaminate each other, resulting in corruption of precoding matrices used by base stations, and high inter-cell interference. This paper studies the effects of shifting the location of pilots in time frames used in neighboring cells, and its effectiveness in obtaining better channel estimates, and, thereby, inter-cell interference reduction.

Method and apparatus for transmitting control information for interference mitigation in multiple antenna system

Abstract: A multiple antenna system including a mobile station and a base station are operable to perform a method for transmitting control information for interference mitigation. A Mobile Station (MS) can transmit control information for interference mitigation. The MS determines a first Precoding Matrix Index (PMI) and a second PMI for interference from an adjacent Base Station (BS). Based on a correlation level from correlation values between one of the first PMI and second PMI and the remaining PMIs in the codebook, the MS determines a level of a subset of PMIs, and feeds back information indicating the correlation level.

Method and arrangement in a wireless communication system

Abstract: Method and arrangement in a user equipment for transmitting scheduling requests to a base station The base station is adapted to serve the user equipment The user equipment is configured to transmit scheduling requests to the base station only at certain predetermined scheduling request opportunities The method comprises triggering a scheduling request transmission, transmitting a scheduling request to the base station at the next occurring scheduling request opportunity, starting a scheduling request prohibiting timer and prohibiting any further scheduling request retransmission at future scheduling request opportunities while the scheduling request prohibiting timer is running Also, a corresponding method and arrangement in a base station is described

Method and apparatus for generating reference signals for accurate time-difference of arrival estimation

Abstract: A base station communicates a positioning reference signal (PRS) to wireless communication devices over a downlink in a wireless communication system by encoding a PRS into a first set of transmission resources, encoding other information into a second set of transmission resources, multiplexing the two sets of resources into a subframe such that the first set of resources is multiplexed into at least a portion of a first set of orthogonal frequency division multiplexed (OFDM) symbols based on an identifier associated with the base station and the second set of resources is multiplexed into a second set of OFDM symbols. Upon receiving the subframe, a wireless communication device determines which set of transmission resources contains the PRS based on the identifier associated with the base station that transmitted the subframe and processes the set of resources containing the PRS to estimate timing (e.g., time of arrival) information.

Apparatus and methods of whitespace communication

Abstract: The described apparatus and methods provide communication services utilizing a combination of non-white space (NWS) and white space (WS) networks. For example, in an aspect, the described apparatus and methods receive, at a first base station (BS) and on a licensed frequency, a communication request for network access from a wireless access terminal (AT). The aspects also determine at least one available unlicensed frequency corresponding to a location of the wireless AT. Further, the aspects partition at least a portion of the network access for the wireless AT to be via the at least one available unlicensed frequency. Additionally, the aspects inform the wireless AT of the at least one available unlicensed frequency for use to obtain at least the portion of the network access. Additional aspects relate to NWS BS assisted handoffs of WS calls, dynamic caching of WS information, peer-to-peer WS communication, and WS BS venue-specific broadcasting.

Handover of direct peer to peer communication

Abstract: Methods and apparatus, including computer program products, are provided for D2D handovers. The method may include sending to a target base station a handover request message including a proposed common identifier for a device-to-device pair and a proposed allocation of radio resources for the device-to-device pair; receiving, from the target base station in response to the handover request message, a handover request reply message including a confirmation of the proposed allocation and of the proposed common identifier; sending to a first device of the device-to-device pair a handover command including the proposed allocation and the proposed common identifier; receiving, from a second device of the device-to-device pair, a measurement report representative of the target base station; and determining whether to initiate a handover of the second device to the target base station, wherein when the handover is initiated, the first device of the device-to-device pair and the second device of the device-to-device pair are handed over to the target base station. Related apparatus, systems, methods, and articles are also described.

Interference control, sinr optimization and signaling enhancements to improve the performance of otdoa measurements

Abstract: A wireless terminal receives signaling information, pertaining to a reference signal transmission in at least one specifically designated sub frame, the signaling information including a list, the list including base station identities The terminal determines, from at least one of the base station identities in the list, the time-frequency resources associated with a reference signal transmission intended for observed time difference of arrival (OTDOA) measurements from a transmitting base station associated with said one base station identity The time of arrival of a transmission from the transmitting base station, relative to reference timing, is measured The wireless terminal can receive a command from a serving cell to start performing inter-frequency OTDOA measurement on a frequency layer containing reference signals, the frequency layer distinct from the serving frequency layer, the serving frequency layer not containing positioning reference signals The wireless terminal can perform OTDOA measurements subsequent to the reception of the command on a carrier frequency different from the serving cell carrier frequency A base station transmitter can jointly schedule a reference signal transmission from a plurality of base station transmitters for the purpose of OTD estimation enhancement, and transmit identical reference signals from the plurality of base station transmitters, the reference signals being identical both in the signal sequence and time-frequency resources used for transmission

Cooperative Sensing via Sequential Detection

Abstract: Efficient and reliable spectrum sensing plays a critical role in cognitive radio networks. This paper presents a cooperative sequential detection scheme to reduce the average sensing time that is required to reach a detection decision. In the scheme, each cognitive radio computes the log-likelihood ratio for its every measurement, and the base station sequentially accumulates these log-likelihood statistics and determines whether to stop making measurement. The paper studies how to implement the scheme in a robust manner when the assumed signal models have unknown parameters, such as signal strength and noise variance. These ideas are illustrated through two examples in spectrum sensing. One assumes both the signal and noise are Gaussian distributed, while the other assumes the target signal is deterministic.

Inter-cell interference coordination method and apparatus for wireless communication system

Abstract: An inter-cell interference coordination method and apparatus is provided for mitigating inter-cell interference in a wireless communication system by using interference coordination information exchanged among neighbor base stations. The method includes receiving, at a serving base station, power control messages transmitted by neighbor base stations, receiving incoming interference coordination messages transmitted by neighbor base stations, each message including interference indicators of resource blocks, allocating the resource blocks with transmission power per resource block to user equipments served by the base station based on the power control and interference coordination messages, generating outgoing interference coordination messages for the respective neighbor base stations based on the resource block allocation result, and transmitting the interference coordination messages to the neighbor base stations, respectively.