Showing papers on "Base station published in 2007"

Radio communication system

Abstract: PROBLEM TO BE SOLVED: To suppress wiring costs even if there is an area that can not be watched from a base station device, by utilizing a radio repeater station, to construct a radio system wherein useless traffic is not generated, by utilizing a route control table and further, to also deal with the movement of a radio terminal device. SOLUTION: Regarding a base station device 24, a radio relay station 40 and a radio terminal device 26 existent under control of an information transfer apparatus 22 itself, the information transfer apparatus 22 stores in a table storage section 22a the relation between layer-3 addresses of the devices and its own communication port 28-i to which those devices are connected. Therefore, a communication port 28-i for outputting is determined in accordance with the layer-3 destination address of a packet, and the packet can be outputted from the communication port 28-i. If the radio terminal device 26 moves, the information transfer apparatus 22 and the radio relay station 40 then rewrite their tables. COPYRIGHT: (C)2008,JPO&INPIT

On the Feasibility of Distributed Beamforming in Wireless Networks

Abstract: Energy efficient communication is a fundamental problem in wireless ad-hoc and sensor networks. In this paper, we explore the feasibility of a distributed beamforming approach to this problem, with a cluster of distributed transmitters emulating a centralized antenna array so as to transmit a common message signal coherently to a distant base station. The potential SNR gains from beamforming are well-known. However, realizing these gains requires synchronization of the individual carrier signals in phase and frequency. In this paper we show that a large fraction of the beamforming gains can be realised even with imperfect synchronization corresponding to phase errors with moderately large variance. We present a master-slave architecture where a designated master transmitter coordinates the synchronization of other (slave) transmitters for beamforming. We observe that the transmitters can achieve distributed beamforming with minimal coordination with the base station using channel reciprocity. Thus, inexpensive local coordination with a master transmitter makes the expensive communication with a distant base station receiver more efficient. However, the duplexing constraints of the wireless channel place a fundamental limitation on the achievable accuracy of synchronization. We present a stochastic analysis that demonstrates the robustness of beamforming gains with imperfect synchronization, and demonstrate a tradeoff between synchronization overhead and beamforming gains. We also present simulation results for the phase errors that validate the analysis

Joint optimization of relay strategies and resource allocations in cooperative cellular networks

Abstract: This paper considers a wireless cooperative cellular data network with a base station and many subscribers in which the subscribers have the ability to relay information for each other to improve the overall network performance. For a wireless network operating in a frequency-selective slow-fading environment, the choices of relay node, relay strategy, and the allocation of power and bandwidth for each user are important design parameters. The design challenge is compounded further by the need to take user traffic demands into consideration. This paper proposes a centralized utility maximization framework for such a network. We show that for a cellular system employing orthogonal frequency-division multiple-access (OFDMA), the optimization of physical-layer transmission strategies can be done efficiently by introducing a set of pricing variables as weighting factors. The proposed solution incorporates both user traffic demands and the physical channel realizations in a cross-layer design that not only allocates power and bandwidth optimally for each user, but also selects the best relay node and best relay strategy (i.e. decode-and-forward vs. amplify-and-forward) for each source-destination pair

System and method for distributed input-distributed output wireless communications

Abstract: A method is described comprising: transmitting a training signal from each antenna of a base station to each of a plurality of client devices, each of the client devices analyzing each training signal to generate channel characterization data, and transmitting the channel characterization data back to the base station; storing the channel characterization data for each of the plurality of client devices; receiving data to be transmitted to each of the client devices; and precoding the data using the channel characterization data associated with each respective client device to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device.

Portable base station device

Abstract: This invention provides a mobile base station device which allows tamper resistance to be adequately secured even when the housing is opened illicitly. In a mobile base station device 1, when a housing 2 is opened illicitly, a user ID or similar is transmitted to a service management server 20, and the user attempting an illicit operation is identified. By registering the identified user on a blacklist, subsequent use of the mobile base station device 1 by this user can be prohibited. Also, in the mobile base station device 1, together with transmission of the user ID, a communication control program 7 is deleted from a communication control module 6, so that the interior of the housing 2 is rendered a “black box”, and modification and illicit use of the communication control program can be deterred. As a result, even when the housing 2 of the mobile base station device 1 is opened illicitly, tamper resistance can be adequately secured.

Multiuser MIMO-OFDM for Next-Generation Wireless Systems

Abstract: This overview portrays the evolution of orthogonal frequency division multiplexing (OFDM) research. The amelioration of powerful multicarrier OFDM arrangements with multiple-input multiple-output (MIMO) systems has numerous benefits, which are detailed in this treatise. We continue by highlighting the limitations of conventional detection and channel estimation techniques designed for multiuser MIMO OFDM systems in the so-called rank-deficient scenarios, where the number of users supported or the number of transmit antennas employed exceeds the number of receiver antennas. This is often encountered in practice, unless we limit the number of users granted access in the base station's or radio port's coverage area. Following a historical perspective on the associated design problems and their state-of-the-art solutions, the second half of this treatise details a range of classic multiuser detectors (MUDs) designed for MIMO-OFDM systems and characterizes their achievable performance. A further section aims for identifying novel cutting-edge genetic algorithm (GA)-aided detector solutions, which have found numerous applications in wireless communications in recent years. In an effort to stimulate the cross pollination of ideas across the machine learning, optimization, signal processing, and wireless communications research communities, we will review the broadly applicable principles of various GA-assisted optimization techniques, which were recently proposed also for employment in multiuser MIMO OFDM. In order to stimulate new research, we demonstrate that the family of GA-aided MUDs is capable of achieving a near-optimum performance at the cost of a significantly lower computational complexity than that imposed by their optimum maximum-likelihood (ML) MUD aided counterparts. The paper is concluded by outlining a range of future research options that may find their way into next-generation wireless systems.

Fair resource allocation in wireless networks using queue-length-based scheduling and congestion control

Abstract: We consider the problem of allocating resources (time slots, frequency, power, etc.) at a base station to many competing flows, where each flow is intended for a different receiver. The channel conditions may be time-varying and different for different receivers. It is well-known that appropriately chosen queue-length based policies are throughput-optimal while other policies based on the estimation of channel statistics can be used to allocate resources fairly (such as proportional fairness) among competing users. In this paper, we show that a combination of queue-length-based scheduling at the base station and congestion control implemented either at the base station or at the end users can lead to fair resource allocation and queue-length stability.

Channel Estimation for Amplify and Forward Relay Based Cooperation Diversity Systems

Abstract: Cooperation diversity schemes have been proposed for cellular networks that permit a base station (or a mobile station) to relay signals to a destination receiver, thereby increasing the network coverage and reliability. The mobile relays either decode and forward (DF) or amplify and forward (AF) the received signal. Most existing analyses of cooperation diversity assumes perfect channel information at the receiver. A realistic assessment should consider the effects of practical channel estimation schemes. This paper considers pilot symbol aided channel estimation for cooperation diversity systems. Since the overall channel in AF systems is different from conventional cellular channels, the channel estimation problem is interesting and challenging and therefore our focus is on AF systems. The paper addresses issues such as the estimator design, pilot symbol spacing based upon realistic channel models, and an approximate bit error rate (BER) analysis that accounts for imperfect channel estimation.

Energy-Aware Clustering for Wireless Sensor Networks using Particle Swarm Optimization

Abstract: Wireless sensor networks (WSNs) are mainly characterized by their limited and non-replenishable energy supply. Hence, the need for energy efficient infrastructure is becoming increasingly more important since it impacts upon the network operational lifetime. Sensor node clustering is one of the techniques that can expand the lifespan of the whole network through data aggregation at the cluster head. In this paper, we present an energy-aware clustering for wireless sensor networks using particle swarm optimization (PSO) algorithm which is implemented at the base station. We define a new cost function, with the objective of simultaneously minimizing the intra-cluster distance and optimizing the energy consumption of the network. The performance of our protocol is compared with the well known cluster-based protocol developed for WSNs, LEACH (low-energy adaptive clustering hierarchy) and LEACH-C, the later being an improved version of LEACH. Simulation results demonstrate that our proposed protocol can achieve better network lifetime and data delivery at the base station over its comparatives.

Hybrid Wireless-Optical Broadband-Access Network (WOBAN): A Review of Relevant Challenges

Abstract: The hybrid wireless-optical broadband-access network (WOBAN) is a promising architecture for future access networks. Recently, the wireless part of WOBAN has been gaining increasing attention, and early versions are being deployed as municipal access solutions to eliminate the wired drop to every wireless router at customer premises. This architecture saves on network deployment cost because the fiber need not penetrate each end-user, and it extends the reach of emerging optical-access solutions, such as passive optical networks. This paper first presents an architecture and a vision for the WOBAN and articulates why the combination of wireless and optical presents a compelling solution that optimizes the best of both worlds. While this discussion briefly touches upon the business drivers, the main arguments are based on technical and deployment considerations. Consequently, the rest of this paper reviews a variety of relevant research challenges, namely, network setup, network connectivity, and fault-tolerant behavior of the WOBAN. In the network setup, we review the design of a WOBAN where the back end is a wired optical network, the front end is managed by a wireless connectivity, and, in between, the tail ends of the optical part [known as optical network unit (ONU)] communicate directly with wireless base stations (known as ldquogateway routersrdquo). We outline algorithms to optimize the placement of ONUs in a WOBAN and report on a survey that we conducted on the distribution and types of wireless routers in the Wildhorse residential neighborhood of North Davis, CA. Then, we examine the WOBAN's routing properties (network connectivity), discuss the pros and cons of various routing algorithms, and summarize the idea behind fault-tolerant design of such hybrid networks.

Mobile Element Scheduling with Dynamic Deadlines

Abstract: Wireless networks have historically considered support for mobile elements's an extra overhead. However, recent research has provided the means by which a network can take advantage of mobile elements. Particularly in the case of wireless sensor networks, mobile elements can be deliberately built into the system to improve the lifetime of the network and act as mechanical carriers of data. The mobile element, whose mobility is controlled, visits the nodes to collect their data before their buffers are full. In general, the spatio-temporal dynamics of the sensed phenomenon may require sensor nodes to collect samples at different rates, in which case, some nodes need to be visited more frequently than others. This work formulates the problem of scheduling the mobile element in the network so that there is no data loss due to buffer overflow. The problem is shown to be NP-complete and an integer-linear-programming formulation is given. Finally, some computationally practical algorithms for a single mobile and for the case of multiple mobiles are presented and their performances compared

SenCar: An Energy-Efficient Data Gathering Mechanism for Large-Scale Multihop Sensor Networks

Abstract: In this paper, we propose a new data gathering mechanism for large-scale multihop sensor networks. A mobile data observer, called SenCar, which could be a mobile robot or a vehicle equipped with a powerful transceiver and battery, works like a mobile base station in the network. SenCar starts the data gathering tour periodically from the static data processing center, traverses the entire sensor network, gathers the data from sensors while moving, returns to the starting point, and, finally, uploads data to the data processing center. Unlike SenCar, sensors in the network are static and can be made very simple and inexpensive. They upload sensed data to SenCar when SenCar moves close to them. Since sensors can only communicate with others within a very limited range, packets from some sensors may need multihop relays to reach SenCar. We first show that the moving path of SenCar can greatly affect network lifetime. We then present heuristic algorithms for planning the moving path/circle of SenCar and balancing traffic load in the network. We show that, by driving SenCar along a better path and balancing the traffic load from sensors to SenCar, network lifetime can be prolonged significantly. Our moving planning algorithm can be used in both connected networks and disconnected networks. In addition, SenCar can avoid obstacles while moving. Our simulation results demonstrate that the proposed data gathering mechanism can prolong network lifetime significantly compared to a network that has only a static observer or a network in which the mobile observer can only move along straight lines.

Dynamic Association for Load Balancing and Interference Avoidance in Multi-cell Networks

Abstract: In promising OFDMA systems, downlink signals originating from the same base station (BS) are orthogonal, while those from different BSs interfere with each other. As a consequence, inter-cell interference (ICI) becomes major performance degradation factor. Particularly, boundary users suffer from severe ICI in addition to the inherent near-far problem. To improve cell edge performances and support a more balanced data rate among all users, partial frequency reuse (PFR) and load-balancing schemes are investigated in this paper. We have formulated a utility maximization problem with network-wide proportional fairness (PF) as an objective in a multi-cell network with PFR. To solve this problem, we propose an offline optimal algorithm and also efficient online algorithms. Our online algorithms are based on simple inter/intra-handover and cell-site selection in which a metric is changed from the signal strength to the average throughput. Through extensive simulations, we demonstrate that our online algorithms can achieve network-wide PF very closely. Compared to the conventional system with a universal frequency reuse where a user is bound to the best signal strength base station, the proposed algorithms bring two types of performance gain: interference avoidance (IA) and load balancing (LB) gain. These gains improve the system performance, especially for users at the cell boundary.

Wireless communication systems

Abstract: A wireless communication method in a system in which subscriber stations are each operable for communication with a base station is provided. The base station is capable of performing simultaneous communications with a plurality of the subscriber stations simultaneously by exchange of packets each conforming with a layered protocol of said system. The packets include a first portion for defining physical layer (PHY) parameters and a second portion for defining media access layer (MAC) parameters. Furthermore, communications between the subscriber stations and the base station are performed wholly or partly through at least one relay station. In this system, the method includes, in the relay station, receiving a plurality of packets from the subscriber stations, detecting the second portion of each of the packets, combining the detected second portions to form a second portion of at least one new packet, and transmitting the new packet to the base station.

Effects of User-Deployed, Co-Channel Femtocells on the Call Drop Probability in a Residential Scenario

Abstract: The femtocell concept aims to combine fixed-line broadband access with cellular telephony using the deployment of low-cost, low-power 3G base stations in the subscriber's homes. These plug-and-play residential base stations would be deployed without much consideration to cell planning on the part of the user, relying instead on inbuilt auto-configuration abilities to minimise the impact on the macro cellular network by self-provisioning parameters such as the transmit and pilot power levels. In this paper, simulations of the deployment of such femtocells in a residential scenario were performed to study its effects on the service experienced by users that are connected to the underlay macrocells. The results show that with auto-configuration, the deployment of the femtocells would not pose a significant impact on the dropped call rate, causing an additional 0.45% increase in chance of a macrocell user's call dropping in the simulation's worst case scenario. In addition the impact of such femtocell deployment on the network signalling is discussed.

Wireless network camera systems

Abstract: Apparatus, systems and techniques associated with battery powered wireless camera systems. One aspect of the subject matter described in this specification can be embodied in a system that includes a battery powered wireless camera including an internal battery to provide energy and a burst transmission unit to transmit information during burst periods. The system includes a base station, separated from the battery powered wireless camera, in wireless communication with the battery powered wireless camera to receive information from the battery powered wireless camera. The base station is configured to process the received information and includes a web server to transmit the processed information to a client. Other embodiments of this aspect include corresponding systems, apparatus, and computer program products.

Adaptive modulation and coding

Abstract: A mobile communication system for transmitting or receiving a signal among a user equipment and a base station, includes the user equipment and the base station. The user equipment includes a unit operable to measure a received signal quality, and a unit operable to report the measuring received signal quality to the base station or a selected modulation and coding scheme to the base station. The base station includes a unit operable to receive the measuring received signal quality at the user equipment or an information indicating a selected modulation and coding scheme at the user equipment.

The Concentric Clustering Scheme for Efficient Energy Consumption in the PEGASIS

Abstract: The wireless sensor network is a type of the wireless ad-hoc networks. It is composed of a collection of sensor nodes. Sensor nodes collect and deliver necessary data in response to user's specific requests. It is expected to apply the wireless sensor network technology to various application areas such as the health, military and home. However, because of several limitations of sensor nodes, the routing protocols used in the wireless ad-hoc network are not suitable for the wireless sensor networks. For this reasons, many novel routing protocols for the wireless sensor networks are proposed recently. One of these protocols, the PEGASIS (power-efficient gathering in sensor information systems) protocol is a chain-based protocol. In general, the PEGASIS protocol presents twice or more performance in comparison with the LEACH (low energy adaptive clustering hierarchy) protocol. However, the PEGASIS protocol causes the redundant data transmission since one of nodes on the chain is selected as the head node regardless of the base station's location. In this paper, we propose the enhanced PEGASIS protocol based on the concentric clustering scheme to solve this problem. The main idea of the concentric clustering scheme is to consider the location of the base station to enhance its performance and to prolong the lifetime of the wireless sensor networks. As simulation results, the enhanced PEGASIS protocol using the concentric clustering scheme performs better than the current PEGASIS protocol by about 35%.

Fixed mobile convergence (FMC) architectures for broadband access: integration of EPON and WiMax

Abstract: EPON and WiMAX are two promising broadband access technologies for new-generation wired and wireless access. Their complementary features motivate interest in using EPON as a backhaul to connect multiple dispersed WiMAX base stations. In this article we propose four broadband access architectures to integrate EPON and WiMAX technologies. The integrated architectures can take advantage of the bandwidth benefit of fiber communications, and the mobile and non-line-of-sight features of wireless communications. Based on these integrated architectures, we elaborate on related control and operation issues to address the benefits gained by this integration. Integration of EPON and WiMAX enables fixed mobile convergence, and is expected to significantly reduce overall design and operational costs for new-generation broadband access networks.

Energy-efficient wireless sensor network design and implementation for condition-based maintenance

Abstract: A new application architecture is designed for continuous, real-time, distributed wireless sensor networks. We develop a wireless sensor network for machinery condition-based maintenance (CBM) in small machinery spaces using commercially available products. We develop a hardware platform, networking architecture, and medium access communication protocol. We implement a single-hop sensor network to facilitate real-time monitoring and extensive data processing for machine monitoring. A new radio battery consumption model is presented and the battery consumption equation is used to select the most suitable topology and design an energy efficient communication protocol for wireless sensor networks. A new streamlined matrix formulation is developed that allows the base station to compute the best periodic sleep times for all the nodes in the network. We combine scheduling and contention to design a hybrid MAC protocol, which achieves 100p collision avoidance by using our modified RTS-CTS contention mechanism known as UC-TDMA protocol. A LabVIEW graphical user interface is described that allows for signal processing, including FFT, various moments, and kurtosis. A wireless CBM sensor network implementation on a heating and air conditioning plant is presented as a case study.

Fixed Mobile Convergence Architectures for Broadband Access: Integration of EPON and WiMAX [Topics in Optical Communications]

Abstract: EPON and WiMAX are two promising broadband access technologies for new-generation wired and wireless access. Their complementary features motivate interest in using EPON as a backhaul to connect multiple dispersed WiMAX base stations. In this article we propose four broadband access architectures to integrate EPON and WiMAX technologies. The integrated architectures can take advantage of the bandwidth benefit of fiber communications, and the mobile and non-line-of-sight features of wireless communications. Based on these integrated architectures, we elaborate on related control and operation issues to address the benefits gained by this integration. Integration of EPON and WiMAX enables fixed mobile convergence, and is expected to significantly reduce overall design and operational costs for new-generation broadband access networks.

A method and apparatus for using distributed antennas

Abstract: A distributed antenna system for using distributed antennas provides for locating a plurality of distributed antennas on existing infrastructure such as existing utility poles, traffic lights/signals, streetlights, etc. Each of the distributed antennas is connected to a base station hotel using a fiber optic cable. The distributed antenna system allows users to access wireless services provided by a plurality of carriers and using a plurality of communication technologies using a truly shared network and without having to implement duplicative wireless infrastructure components.

Multi-user MIMO-SDMA for finite rate feedback systems

Abstract: A multi-user MIMO downlink beamforming system with limited feedback ( 200 ) is provided to enable precoding for multi-stream transmission, where a channel codeword (u i ) and one or more channel quality indicator values (CQI A , CQI B ) are computed at the user equipment ( 201. i ) on the basis of maximizing a predetermined SINR performance metric (ρ i ) which estimates the receive signal-to-noise-ratio (SINR) at the user equipment ( 201. i ). The computed codeword (u i ) and CQI values (or differential values related thereto) are quantized and fed back to help the base station ( 210 ) which applies a correction to the appropriate CQI value in the course of designing the transmit beamforming vectors w and determining the appropriate modulation and coding level to be used for downlink data transmission.

Coordinating Base Stations for Greater Uplink Spectral Efficiency in a Cellular Network

Abstract: We propose an ambitious approach towards lifting the limits imposed by cochannel interference on the uplink spectral efficiency of a cellular network, viz., coordinating several base stations in the reception of users within their coverage area, and suppressing interference between users by means of coherent linear beamforming across the base stations. We evaluate by simulation the potential gain in spectral efficiency from such coordination, when there is 1 user per base station antenna in the network, and all users (but for a small fraction in outage) must be served at a constant and common data rate. We highlight the dependence of the spectral efficiency gain on the number of rings of neighbors with which each base station is coordinated, as well as the underlying signal-to-noise ratio (SNR) distribution in the network. Results from this study point to the possibility of doubling the uplink spectral efficiency with 1-ring coordination and nearly quadrupling it with 4-ring coordination, under high-SNR conditions.

Distributed antenna communications system and methods of implementing thereof

Abstract: The present invention provides a distributed antenna communications system and methods of implementing a distributed antenna communications system. In accordance with an embodiment of the invention, a distributed antenna system comprises: a base station configured for communication with a telecommunications network; a multi-port repeater hub connected to the base station to receive a communications signal from the base station and to distribute the communications signal to a plurality of ports of the multi-port repeater hub, the multi-port repeater hub comprising a scanner for scanning a plurality of frequency channels to identify one or more channels of the communications signal received from the base station; and a plurality of antenna units, each coupled to one of the ports of the multi-port repeater hub

A dynamic clustering and energy efficient routing technique for sensor networks

Abstract: In the development of various large-scale sensor systems, a particularly challenging problem is how to dynamically organize the sensors into a wireless communication network and route sensed information from the field sensors to a remote base station. This paper presents a new energy-efficient dynamic clustering technique for large-scale sensor networks. By monitoring the received signal power from its neighboring nodes, each node estimates the number of active nodes in realtime and computes its optimal probability of becoming a cluster head, so that the amount of energy spent in both intra- and inter-cluster communications can be minimized. Based on the clustered architecture, this paper also proposes a simple multihop routing algorithm that is designed to be both energy-efficient and power-aware, so as to prolong the network lifetime. The new clustering and routing algorithms scale well and converge fast for large-scale dynamic sensor networks, as shown by our extensive simulation results.

Mobile communication system and mobile terminal

Abstract: A mobile terminal (3) judges whether or not the mobile terminal is able to make a transition to a DTX period during Active, and, when judging that the mobile terminal is able to make a transition to a DTX period during Active, notifies a base station (2) to that effect. If the base station (2) judges that the mobile terminal is able to make a transition to a DRX period during Active when triggered by the notification from the mobile terminal (3), the base station (2) temporarily stops supply of electric power to the data transmission processing units and the data reception processing units of the mobile terminal (3).

Ranging regions for wireless communication relay stations

Abstract: One embodiment of the present invention provides a unique ranging technique in wireless communication environments that employ relay stations associated with a base station. Each relay station, and optionally the base station itself, can be allocated a unique ranging region having unique ranging resources that may be used by a mobile station to initiate a ranging function with the corresponding relay station or base station.

Active service redirection for a private femto cell

Abstract: A femto cell at a customer premises, such as an IP-based femto Base Transceiver System (IP-BTS), can be configured as a “private access” node intended to service a limited set of mobile stations. However, mobile stations not associated with the private femto cell may acquire and lock onto the femto BTS. To avoid service blockages in such cases, the private femto BTS will allow call access attempts by, and call deliveries to, a non-associated mobile station, despite the “private access” configuration. However, upon completion of call set-up, the non-associated mobile station is directed to initiate handoff, from the private femto cell coverage provided by the femto BTS into a cell coverage of a base station of the macro network, to conserve femto cell resources for use in servicing calls of the associated mobile station(s).

Method and apparatus for handover in a wireless communication system

Abstract: A method and apparatus for handover in a wireless communication system. A connection can be established with a mobile station (110). A measurement report can be received at a source base station (120) from the mobile station. The source base station can determine that the mobile station should perform a handover from the source base station to the target base station (130). Timing advance information can be received at the source base station from the target base station. The timing advance information can be forwarded from the source base station to the mobile station. A connection of the mobile station can be switched from the source base station to the target base station.