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Showing papers on "Base station published in 2005"


Proceedings ArticleDOI
13 Mar 2005
TL;DR: This paper suggests that the base station be mobile; in this way, the nodes located close to it change over time and the obtained improvement in terms of network lifetime is in the order of 500%.
Abstract: Although many energy efficient/conserving routing protocols have been proposed for wireless sensor networks, the concentration of data traffic towards a small number of base stations remains a major threat to the network lifetime. The main reason is that the sensor nodes located near a base station have to relay data for a large part of the network and thus deplete their batteries very quickly. The solution we propose in this paper suggests that the base station be mobile; in this way, the nodes located close to it change over time. Data collection protocols can then be optimized by taking both base station mobility and multi-hop routing into account. We first study the former, and conclude that the best mobility strategy consists in following the periphery of the network (we assume that the sensors are deployed within a circle). We then consider jointly mobility and routing algorithms in this case, and show that a better routing strategy uses a combination of round routes and short paths. We provide a detailed analytical model for each of our statements, and corroborate it with simulation results. We show that the obtained improvement in terms of network lifetime is in the order of 500%.

937 citations


Proceedings ArticleDOI
12 Dec 2005
TL;DR: An energy-efficient unequal clustering mechanism for periodical data gathering in wireless sensor networks that partitions the nodes into clusters of unequal size, and clusters closer to the base station can preserve some energy for the inter-cluster data forwarding.
Abstract: Clustering provides an effective way for prolonging the lifetime of a wireless sensor network. Current clustering algorithms usually utilize two techniques, selecting cluster heads with more residual energy and rotating cluster heads periodically, to distribute the energy consumption among nodes in each cluster and extend the network lifetime. However, they rarely consider the hot spots problem in multihop wireless sensor networks. When cluster heads cooperate with each other to forward their data to the base station, the cluster heads closer to the base station are burdened with heavy relay traffic and tend to die early, leaving areas of the network uncovered and causing network partition. To address the problem, we propose an energy-efficient unequal clustering (EEUC) mechanism for periodical data gathering in wireless sensor networks. It partitions the nodes into clusters of unequal size, and clusters closer to the base station have smaller sizes than those farther away from the base station. Thus cluster heads closer to the base station can preserve some energy for the inter-cluster data forwarding. We also propose an energy-aware multihop routing protocol for the inter-cluster communication. Simulation results show that our unequal clustering mechanism balances the energy consumption well among all sensor nodes and achieves an obvious improvement on the network lifetime

654 citations


Proceedings ArticleDOI
13 Mar 2005
TL;DR: SyncScan is described, a low-cost technique for continuously tracking nearby base stations by synchronizing short listening periods at the client with periodic transmissions from each base station and it is demonstrated that it allows better handoff decisions and over an order of magnitude improvement in handoff delay.
Abstract: Wireless access networks scale by replicating base stations geographically and then allowing mobile clients to seamlessly "hand off" from one station to the next as they traverse the network. However, providing the illusion of continuous connectivity requires selecting the right moment to handoff and the right base station to transfer to. Unfortunately, 802.11-based networks only attempt a handoff when a client's service degrades to a point where connectivity is threatened. Worse, the overhead of scanning for nearby base stations is routinely over 250 ms - during which incoming packets are dropped - far longer than what can be tolerated by highly interactive applications such as voice telephony. In this paper we describe SyncScan, a low-cost technique for continuously tracking nearby base stations by synchronizing short listening periods at the client with periodic transmissions from each base station. We have implemented this SyncScan algorithm using commodity 802.11 hardware and we demonstrate that it allows better handoff decisions and over an order of magnitude improvement in handoff delay. Finally, our approach only requires trivial implementation changes, is incrementally deployable and is completely backward compatible with existing 802.11 standards.

556 citations


Proceedings ArticleDOI
13 Mar 2005
TL;DR: This paper shows that a combination of queue-length-based scheduling at the base station and congestion control implemented either atThe base station or at the end users can lead to fair resource allocation and queue- length stability.
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.

417 citations


Journal ArticleDOI
TL;DR: By applying recent advances in probabilistic inference of position and sensor fusion from noisy signals, it is shown that the RF emissions from base stations as measured by off-the-shelf wireless Ethernet cards are sufficiently rich in information to permit a mobile device to reliably track its location.
Abstract: A key subproblem in the construction of location-aware systems is the determination of the position of a mobile device. This article describes the design, implementation and analysis of a system for determining position inside a building from measured RF signal strengths of packets on an IEEE 802.11b wireless Ethernet network. Previous approaches to location-awareness with RF signals have been severely hampered by non-Gaussian signals, noise, and complex correlations due to multi-path effects, interference and absorption. The design of our system begins with the observation that determining position from complex, noisy and non-Gaussian signals is a well-studied problem in the field of robotics. Using only off-the-shelf hardware, we achieve robust position estimation to within a meter in our experimental context and after adequate training of our system. We can also coarsely determine our orientation and can track our position as we move. Our results show that we can localize a stationary device to within 1.5 meters over 80% of the time and track a moving device to within 1 meter over 50% of the time. Both localization and tracking run in real-time. By applying recent advances in probabilistic inference of position and sensor fusion from noisy signals, we show that the RF emissions from base stations as measured by off-the-shelf wireless Ethernet cards are sufficiently rich in information to permit a mobile device to reliably track its location.

323 citations


Patent
20 Jun 2005
TL;DR: In this article, a method and apparatus for determining a position of a base station in a wireless communication network that includes a mobile station in communication with base stations is presented, where a BTS calibration server is networked with the base stations.
Abstract: A method and apparatus for determining a position of a base station in a wireless communication network that includes a mobile station in communication with base stations. A BTS calibration server is networked with the base stations. A BTS calibration program is programmed into a group of mobile stations that have position location capabilities. Using the BTS calibration program, calibration information may be requested by the BTS calibration server, or a session may be initiated by the mobile station. The BTS calibration program also provides privacy features that allow user of the mobile station to prevent it from being used for base station location. If authorized, the BTS calibration program determines the position of the mobile station, and provides calibration information, such as position and base station phase measurements, to the server. The calibration information may be used to calibrate the base station almanac.

297 citations


Journal ArticleDOI
Yang Xiao1
TL;DR: Energy consumption for the IEEE 802.16e broadband wireless access (BWA) network is studied and the sleep-mode scheme is analytically model and validated with simulations.
Abstract: In this paper, we study energy consumption for the IEEE 802.16e broadband wireless access (BWA) network, A mobile subscriber station goes to sleep-mode after negations with the base station and temporarily wake-up periodically for a short interval to check whether there is downlink traffic to it to decide whether it goes to wake-mode or continues to be in the sleep-mode. The sleep interval is increased exponentially upon no arrival traffic. We analytically model the sleep-mode scheme and validate the model with simulations.

292 citations


Proceedings ArticleDOI
05 Sep 2005
TL;DR: The paper investigates several countermeasures against traffic analysis techniques aimed at disguising the location of a base station, and evaluates them analytically and via simulation using three evaluation criteria: total entropy of the network, total energy consumed, and the ability to guard against heuristic-based techniques to locate a base stations.
Abstract: Wireless sensor networks are highly vulnerable to the failure of base stations. An adversary can render a wireless sensor network useless by launching remote, softwarebased attacks or physical attacks on the base stations. This paper addresses the problem of defending a base station against physical attacks by concealing the geographic location of a base station. Typical packet traffic in a sensor network reveals pronounced patterns that allow an adversary analyzing packet traffic to deduce the location of a base station. The paper investigates several countermeasures against traffic analysis techniques aimed at disguising the location of a base station. First, a degree of randomness is introduced in the multi-hop path a packet takes from a sensor node to a base station. Second, random fake paths are introduced to confuse an adversary from tracking a packet as it moves towards a base station. Finally, multiple, random areas of high communication activity are created to deceive an adversary as to the true location of the base station. The paper evaluates these techniques analytically and via simulation using three evaluation criteria: total entropy of the network, total energy consumed, and the ability to guard against heuristic-based techniques to locate a base station.

284 citations


Patent
18 May 2005
TL;DR: In this article, a first antenna exchanges first communications with wireless devices, and exchanges the first communication with a first base station The service node processes the first and second communications to provide a communication service to the wireless devices.
Abstract: At a first site, a first antenna exchanges first communications with wireless devices, and exchanges the first communications with a first base station The first base station exchanges the first communications with a service node At a second site, a second antenna exchanges second communications with other wireless devices, and exchanges the second communications with a first surface wave interface The first surface wave interface exchanges the second communications with a second surface wave interface at the first site The second surface wave interface exchanges the second communications with a second base station at the first site The second base station exchanges the second communications with the service node The service node processes the first and second communications to provide a communication service to the wireless devices

280 citations


Journal ArticleDOI
TL;DR: A new algorithm for distributed power control in cellular communication systems that requires only interference power measurements and/or SIR measurements from the base station and converges even in cases where limits on available power render the target SIRs unattainable.
Abstract: We propose a new algorithm for distributed power control in cellular communication systems. We define a cost for each mobile that consists of a weighted sum of power and square of signal-to-interference ratio (SIR) error and obtain the static Nash equilibrium for the resulting costs. The algorithm requires only interference power measurements and/or SIR measurements from the base station and converges even in cases where limits on available power render the target SIRs unattainable. Examples generated using realistic data demonstrate that, in demanding environments, the Nash equilibrium power provides substantial power savings as compared to the power balancing algorithm while reducing the achieved SIR only slightly. Additional simulations show that the benefit of the Nash equilibrium power control over the power balancing solution increases as the receiver noise power or number of users in the cell increases. The algorithm has the advantage that it can be implemented distributively. An additional benefit of the algorithm is that, based on their chosen cost function, mobiles may choose to "opt out", i.e., stop transmitting, if they determine that the power required to achieve their SIR objectives is more expensive to them than not transmitting at all.

234 citations


Journal ArticleDOI
TL;DR: It is shown that the 3GPP AKA protocol is vulnerable to a variant of the so-called false base station attack, and a new authentication and key agreement protocol is presented which defeats redirection attack and drastically lowers the impact of network corruption.
Abstract: This paper analyzes the authentication and key agreement protocol adopted by Universal Mobile Telecommunication System (UMTS), an emerging standard for third-generation (3G) wireless communications. The protocol, known as 3GPP AKA, is based on the security framework in GSM and provides significant enhancement to address and correct real and perceived weaknesses in GSM and other wireless communication systems. In this paper, we first show that the 3GPP AKA protocol is vulnerable to a variant of the so-called false base station attack. The vulnerability allows an adversary to redirect user traffic from one network to another. It also allows an adversary to use authentication vectors corrupted from one network to impersonate all other networks. Moreover, we demonstrate that the use of synchronization between a mobile station and its home network incurs considerable difficulty for the normal operation of 3GPP AKA. To address such security problems in the current 3GPP AKA, we then present a new authentication and key agreement protocol which defeats redirection attack and drastically lowers the impact of network corruption. The protocol, called AP-AKA, also eliminates the need of synchronization between a mobile station and its home network. AP-AKA specifies a sequence of six flows. Dependent on the execution environment, entities in the protocol have the flexibility of adaptively selecting flows for execution, which helps to optimize the efficiency of AP-AKA both in the home network and in foreign networks.

Patent
07 Jun 2005
TL;DR: In this paper, the authors proposed a technique for adjusting transmit power to mitigate both intra-sector interference to a serving base station and inter-segment interference to neighbor base stations.
Abstract: Techniques for adjusting transmit power to mitigate both intra-sector interference to a serving base station and inter-sector interference to neighbor base stations are described. The amount of inter-sector interference that a terminal may cause may be roughly estimated based on the total interference observed by each neighbor base station, channel gains for the serving and neighbor base stations, and the current transmit power level. The transmit power may be decreased if high interference is observed by a neighbor base station and increased otherwise. The transmit power may be adjusted by a larger amount and/or more frequently if the terminal is located closer to the neighbor base station observing high interference and/or if the current transmit power level is higher, and vice versa. The intra-sector interference is maintained within an acceptable level by limiting a received SNR for the terminal to be within a range of allowable SNRs.

Patent
31 Aug 2005
TL;DR: In this paper, the authors proposed a multiband antenna array for cellular base stations, which provides a reduced width of the base station antenna and minimizes the environmental and visual impact of a network of cellular base station antennas, in particular in mobile telephony and wireless service networks.
Abstract: This invention is in the field of base station antennas for wireless communications. The present invention refers to a slim multi-band antenna array for cellular base stations, which provides a reduced width of the base station antenna and minimizes the environmental and visual impact of a network of cellular base station antennas, in particular in mobile telephony and wireless service networks. A multiband antenna array comprises a first set of radiating elements operating at a first frequency band and a second set of radiating elements operating at a second frequency band, said radiating elements being smaller than λ/2 or smaller than λ/3, being (λ) the longest operating wavelength. The ratio between the largest and the smaller of said frequency bands is smaller than 2.

Patent
23 Sep 2005
TL;DR: In this paper, the authors proposed a method for scheduling in a mobile communication system where data of priority flows is transmitted by mobile terminals via dedicated uplink channels to a base station.
Abstract: The invention relates to a method for scheduling in a mobile communication system where data of priority flows is transmitted by mobile terminals via dedicated uplink channels to a base station. Each mobile terminal transmits at least data of one priority flow via one of the dedicated uplink channels. Moreover, the invention relates to a base station for scheduling priority flows transmitted by mobile terminals via dedicated uplink channels to the base station. Further, a mobile terminal transmitting at least data of one priority flow via a dedicated uplink channel to a base station is provided. In order to optimize base station controlled-scheduling functions in a mobile communication system the invention proposes to provide the scheduling base station with QoS requirements of individual priority flows transmitted via an uplink dedicated channel and to adapt the mobile terminals to indicate the priority flows of which data is to be transmitted to the base stations for scheduling.

Patent
Jianglei Ma1, Hang Zhang1, Wen Tong1, Ming Jia1, Peiying Zhu1, Mo-Han Fong1 
23 Jun 2005
TL;DR: In this article, a preamble that is inserted into an OFDMA frame and has a common sequence for all the base stations participating in a transmission is presented, which may be used in different systems, including multi-output, multi-input (MIMO) systems.
Abstract: The present invention provides a preamble that is inserted into an OFDMA frame and has a common sequence for all the base stations participating in a transmission The subscriber station performs fine synchronization using the common sequence on the common preamble, and the resulting peaks will provide the locations of candidate base stations The base station specific search is then performed in the vicinities of those peaks by using base station specific pseudo-noise sequences With this two stage cell search, the searching window is drastically reduced The preamble is matched to known values by a respective receiver to decode the signals and permit multiple signals to be transferred from the transmitter to the receiver The preamble may comprise two parts, Preamble-1 and Preamble-2, which may be used in different systems, including multioutput, multi-input (MIMO) systems

Journal ArticleDOI
TL;DR: A centralized downlink scheduling scheme in a cellular network with a small number of relays is proposed and it is found that, with four relays deployed in each sector, it is possible to achieve significant throughput gain including the signaling overhead.
Abstract: Future cellular wireless networks could include multihop transmission through relays. We propose a centralized downlink scheduling scheme in a cellular network with a small number of relays. The scheduling scheme has the property that it guarantees stability of the user queues for the largest set of arrival rates. We obtain throughput results by simulation for various scenarios and study the effect of number of relays, relay transmit power relative to the base station (BS) power, and the effect of distributing a given total power between the BS and different numbers of relays. We also present results for the case without channel fading to determine what fraction of the throughput gain is achieved from diversity reception. We find that, with four relays deployed in each sector, it is possible to achieve significant throughput gain including the signaling overhead.

Patent
01 Apr 2005
TL;DR: In this article, a closed-loop power control method is proposed for a mobile communication system, in which a mobile station provides information on the quality of the signal received from the base station, and the BS responds by adjusting the power allocated to that user in a shared base station signal.
Abstract: A method and apparatus for controlling transmission power levels in a mobile communication system. The method provides for a closed-loop power control method. A mobile station provides information on the quality of the signal received from the base station, and the base station responds by adjusting the power allocated to that user in a shared base station signal. The transmission power is adjusted initially by a large increment and then ramped down at an increasingly decreasing rate. The mobile station also provides information to the base station as to its relative velocity and the base station adjusts its transmission power in accordance with this velocity information.

Patent
12 Jul 2005
TL;DR: In this article, a communication system is described, including a mobile communication device, a mobile communications base station, and a server computer system, where the location of the mobile device may be correlated with certain user preferences stored on the server computer.
Abstract: A communication system is described, including a mobile communications device, a mobile communications base station, and a server computer system. The location of the device may be correlated with certain user preferences stored on the server computer system. The components of the larger system are also described. In some cases, various location related mapping functions for a device are discussed. In other cases, systems and methods which provide for activities to be undertaken based on the location of a device are described. The disclosure also addresses systems and methods of efficiently determining the location of a mobile device. In some cases, different notification schemes based on the location of a device and specified preferences are described. The disclosure also addresses systems and methods for keyword monitoring based on the location of a device.

Journal ArticleDOI
TL;DR: A simple algorithm is devised using time-of-arrival measurements of the signal from the mobile station received at three or more base stations, via modifying the classical multidimensional scaling technique, which has been developed for analyzing data obtained from physical, biological, and behavioral science.
Abstract: Localization of mobile phones is now a very popular research topic. A simple algorithm is devised for mobile location estimation using time-of-arrival measurements of the signal from the mobile station received at three or more base stations, via modifying the classical multidimensional scaling technique, which has been developed for analyzing data obtained from physical, biological, and behavioral science. The bias and variance of the proposed algorithm are also derived. Computer simulations are included to corroborate the theoretical development and to contrast the estimator performance with several conventional approaches as well as the Crame/spl acute/r-Rao lower bound.

Patent
24 Jun 2005
TL;DR: In this article, a method of allocating a radio resource in an orthogonal frequency division multiplexing (OFDM) system comprises receiving data associated with radio resource allocation map from a base station, wherein the radio allocation map comprises control parameters for transmitting uplink data to the base station.
Abstract: An uplink capacity is increased by a method in which more than two mobile stations simultaneously use a radio resource allocated to one mobile station. A method of allocating a radio resource in an orthogonal frequency division multiplexing system comprises receiving data associated with a radio resource allocation map from a base station, wherein the radio allocation map comprises control parameters for transmitting uplink data to the base station. The control parameters comprises orthogonal pilot pattern indicator for using orthogonal pilot patterns associated with supporting at least concurrent dual transmission by at least one mobile station, and for use in the same frequency band and same time duration. The orthogonal pilot patterns comprises at least a minus pilot being used for an uplink basic allocation unit. The mobile station then transmits uplink data to the base station by using the orthogonal pilot patterns.

Patent
Shlomo Ovadia1
14 Nov 2005
TL;DR: In this article, the authors propose a handover system for broadband wireless networks, where a determination is made to which target base station (BS) an air interface for a mobile subscriber station (MSS) is to be handed over.
Abstract: Method and system to support fast hand-over of mobile subscriber stations in broadband wireless networks. In connection with a hand-over process, a determination is made to which target base station (BS) an air interface for a mobile subscriber station (MSS) is to be handed-over. Various service requirements are requested by the MSS, including a Quality of Service (QoS) level. Based on feedback from potential target BSs, a target BS for hand-over is selected. Current connection context data corresponding to current service flows provided by a serving BS is passed to the target BS to pre-provision service such that a minimal amount of re-entry messaging is required. In one embodiment, a Management Information Base (MIB) instance is maintained at each BS in a broadband wireless network. To pre-provision service, applicable connection context data are transferred between MIB instances at the serving and target BS using Simple Network Management Protocol (SNMP) messaging.

Journal ArticleDOI
TL;DR: An overview of the scheduling algorithms proposed for fourth-generation multiuser wireless networks based on multiple-input multiple-output technology is presented and several resource allocation schemes are discussed for this hybrid multiple access system.
Abstract: In this article an overview of the scheduling algorithms proposed for fourth-generation multiuser wireless networks based on multiple-input multiple-output technology is presented. In MIMO systems a multi-user diversity gain can be extracted by tracking the channel fluctuations between each user and the base station, and scheduling transmission for the "best" user. Based on this idea, several opportunistic scheduling schemes that attempt to improve global capacity or satisfy users with different QoS requirements have been proposed. Transmit beamforming procedures aimed at increasing the channel fluctuations have been proposed. The simultaneous exploitation of both spatial and multi-user diversity is not straightforward; however, it may be achieved by a refined selection of the "best" user. In addition, a multiple access gain can be obtained from a simple SDMA/TOMA system. Finally, several resource allocation schemes are discussed for this hybrid multiple access system.

Patent
07 Mar 2005
TL;DR: In this article, a radio communication system which includes a base station and terminal apparatuses and performs TDD two-way communications using an OFDM signal including subcarriers in a downstream communication from the base station apparatus to each terminal apparatus, and an FH signal having the same frequency band as that of the subcarrier in an upstream communication from each terminal device to the BS, is described.
Abstract: a radio communication system which includes a base station apparatus and terminal apparatuses and performs TDD two-way communications using an OFDM signal including subcarriers in a downstream communication from the base station apparatus to each terminal apparatus, and an FH signal having the same frequency band as that of the subcarriers in an upstream communication from the each terminal apparatus to the base station apparatus, the each terminal apparatus estimates transmission channel characteristics of the subcarriers based on the OFDM signal received, transmits an estimation result of the estimation unit to the base station apparatus, and the base station apparatus assigns, to the each terminal apparatus, at least one of subcarriers to be used in the downstream communication of the subcarriers and a hopping pattern to be used in the upstream communication, based on the estimation result transmitted from the each terminal apparatus.

Patent
Seung Eun Hong1, Bong Gee Song1, Kwang-Seop Eom1, Min-hee Cho1, Hyeong Jong Ju1 
14 Feb 2005
TL;DR: In this paper, the authors proposed a handover protocol for a broadband wireless communication system including a serving base station communicating with the SS, and at least one neighbor BS neighboring the serving BS.
Abstract: A method for performing a handover by a subscriber station (SS) in a broadband wireless communication system including a serving base station (BS) communicating with the SS, and at least one neighbor BS neighboring the serving BS. The SS receives downlink signals from the serving BS and the neighbor BS; measures an arrival time difference between the downlink signal received from the serving BS and the downlink signal received from the neighbor BS; and transmits the measured arrival time difference to the serving BS.

Patent
19 Sep 2005
TL;DR: In this paper, a multi-mode base station includes a transmit standby mode and an active mode, where the active mode has no active state registered wireless terminals being serviced but may have some sleep state registered WSNs being served.
Abstract: A multi-mode base station includes a transmit standby mode and an active mode. Transmit standby mode of base station operation is a low power/low interference level of operation as compared to active mode. In transmit standby mode at least some of the synchronization signaling such as pilot tone signaling is reduced in power level and/or rate with respect to the active mode. In transmit standby mode, the base station has no active state registered wireless terminals being serviced but may have some sleep state registered wireless terminals being serviced. Mode transitions from active to transmit standby may be in response to: a detected period of inactivity, scheduling information, base station mode change signals, and/or detected wireless terminal state transition. Mode transitions from transmit standby to active may be in response to: scheduling information, access signals, wake-up signals, hand-off signals, wireless terminal state change signals, and/or base station mode change signals.

Proceedings ArticleDOI
01 Dec 2005
TL;DR: This paper devise provable approximation schemes for locating a base station and constructing a network among a set of sensors each of which has a data stream to get to the base station.
Abstract: This paper study two problems that arise in optimization of sensor networks: First, we devise provable approximation schemes for locating a base station and constructing a network among a set of sensors each of which has a data stream to get to the base station Subject to power constraints at the sensors, our goal is to locate the base station and establish a network in order to maximize the lifespan of the network Second, we study optimal sensor placement problems for quality coverage of given domains cluttered with obstacles We assume "line-of-site", sensors, that sense a point only if the straight segment connecting the sensor to this point (the "line-of-site") does not cross any obstacle so obstacles occludes area from using line-of-site sensors, the goal is to minimize the number of sensors required in order to have each point "well covered" according to precise criteria (eg, that each point is seen by two sensors that form at least angle a, or that each point is seen by three sensors that form a triangle containing the point)

Proceedings ArticleDOI
Sik Choi1, Gyung-Ho Hwang1, Taesoo Kwon1, Ae-Ri Lim, Dong-Ho Cho 
05 Dec 2005
TL;DR: This paper proposes an enhanced link-layer handover algorithm that an MSS can receive downlink data before synchronization with uplink during handover process and reduces data transmission delay and packet loss probability for real-time downlink service.
Abstract: IEEE 802.16 WirelessMAN aiming to broadband wireless access (BWA) is evolving to 4G mobile communication systems through the standardization of IEEE 802.16e supporting mobility on existing fixed WirelessMAN systems. Because IEEE 802.16e system is based on OFDM(A) technology, a mobile subscriber station (MSS) basically conducts hard handover operation when it moves to another base station (BS). Therefore, the MSS is not able to send or receive the data during handover process and these data should be delayed. As a result, real-time packet could be dropped by handover delay. In this paper, we propose an enhanced link-layer handover algorithm that an MSS can receive downlink data before synchronization with uplink during handover process. Our proposed scheme reduces data transmission delay and packet loss probability for real-time downlink service.

Journal ArticleDOI
TL;DR: This paper develops a simple algorithm to obtain a power allocation that is asymptotically optimal in the number of mobiles based on dynamic pricing and provides numerical results that illustrate the performance of the algorithm.
Abstract: In this paper we consider a power allocation problem in multi-class wireless systems. We focus on the downlink of the system. Each mobile has a utility function that characterizes its degree of satisfaction for the received service. The objective is to obtain a power allocation that maximizes the total system utility. Typically, natural utility functions for each mobile are nonconcave. Hence, we cannot use existing convex optimization techniques to derive a global optimal solution. We develop a simple (distributed) algorithm to obtain a power allocation that is asymptotically optimal in the number of mobiles. The algorithm is based on dynamic pricing and consists of two stages. At the mobile selection stage, the base station selects mobiles to which power is allocated. At the power allocation stage, the base station allocates power to the selected mobiles. We provide numerical results that illustrate the performance of our scheme. In particular, we show that our algorithm results in system performance that is close to the performance of a global optimal solution in most cases.

Patent
03 Jun 2005
TL;DR: In this paper, the authors proposed a method and system for facilitating efficient handoff and data throughput in mobile broadband communication systems, which includes selectively enabled soft handoff, performing Layer 2 bearer functions at the base station and using the mobile device to coordinate soft handover and interference avoidance without the need for a centralized coordination function.
Abstract: The present invention provides a method and system for facilitating efficient handoff and data throughput in mobile broadband communication systems. Methods implemented by a system constructed in accordance with the principles of the present invention include selectively enabled soft handoff, performing Layer 2 bearer functions at the base station and using the mobile device to coordinate soft handoff and interference avoidance without the need for a centralized coordination function.

Book
30 Jun 2005
TL;DR: This chapter discusses the architecture of a Software-Defined Radio architecture, the relationship between EVM, PCDE, and Rho, and the impact of Superconducting Technologies on Software Defined Radio.
Abstract: Introduction--What is Software Defined Radio. The Requirements for Software-Defined Radio. The Benefits of Multi-Standard Terminals. Operational Requirements. Business Models for Software-Defined Radio. New Base Station and Network Architectures. Smart Antenna Systems. Projects and Sources of Information for Software-Defined Radio. Organization of the Text. References. Basic Architecture of a Software-Defined Radio--Ideal Software-Defined Radio Architecture. Required Hardware Specifications. Digital Aspects of a Software Radio. Current Technology Limitations. Impact of Superconducting Technologies on Software Defined Radio. References. Flexible RF Receiver Architectures--Introduction. Receiver Architecture Options. Implementation of a Digital Receiver. Multi-Band and General Coverage Systems. The Problem of the Duplexer. Achieving Image Reduction. Dynamic Range Enhancement. Influence of Phase-Noise on EVM for a Linear Transceiver. Relationship between EVM, PCDE, and Rho. References. Flexible Transmitters and PAS--Introduction. Differences in PA Requirements and for Base-Stations and Handsets. Basic Upconversion Architectures. Broadband Quadrate Techniques. Linearization Applied to Software Radio Transmitters. Power Amplifier Linearization Techniques. Transmitter Linearization Techniques. RF Synthesis Techniques. Power Efficiency. References.