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Showing papers by "NTT DoCoMo published in 2009"


Journal ArticleDOI
TL;DR: This paper aims to give a comprehensive review of different TOA-based localization algorithms and their technical challenges, and to point out possible future research directions.
Abstract: Localization of a wireless device using the time-of-arrivals (TOAs) from different base stations has been studied extensively in the literature. Numerous localization algorithms with different accuracies, computational complexities, a-priori knowledge requirements, and different levels of robustness against non-line-of-sight (NLOS) bias effects also have been reported. However, to our best knowledge, a detailed unified survey of different localization and NLOS mitigation algorithms is not available in the literature. This paper aims to give a comprehensive review of these different TOA-based localization algorithms and their technical challenges, and to point out possible future research directions. Firstly, fundamental lower bounds and some practical estimators that achieve close to these bounds are summarized for line-of-sight (LOS) scenarios. Then, after giving the fundamental lower bounds for NLOS systems, different NLOS mitigation techniques are classified and summarized. Simulation results are also provided in order to compare the performance of various techniques. Finally, a table that summarizes the key characteristics of the investigated techniques is provided to conclude the paper.

989 citations


Patent
23 Jun 2009
TL;DR: In this article, the authors proposed a mobile communication method in which a mobile station performs a handover from a handoff source radio base station to a hand over target radio BS, which includes the steps of acquiring, at the handover target radio base stations, from a switching center, a key for calculating a first key for generating a certain key used in a communication between the target radio station and the mobile station.
Abstract: The present invention relates to a mobile communication method in which a mobile station performs a handover from a handover source radio base station to a handover target radio base station. The mobile communication method includes the steps of: (A) acquiring, at the handover target radio base station, from the handover source radio base station or a switching center, a key for calculating a first key for generating a certain key used in a communication between the handover target radio base station and the mobile station; and (B) acquiring, at the handover target radio base station, from the switching center, a second key for calculating a first key for generating a certain key used in a communication between a next handover target radio base station and the mobile station.

225 citations


Journal ArticleDOI
TL;DR: The authors' evaluation identifies usability issues regarding the design of physical mobile interactions, interfaces, and applications and their framework for integrating Web services and mobile interaction with physical objects relies on information typing to increase interoperability.
Abstract: The advancement of ubiquitous computing technologies has greatly improved the availability of digital resources in the real world. Here, the authors investigate mobile interaction with tagged, everyday objects and associated information that's based on the Internet of things and its technologies. Their framework for integrating Web services and mobile interaction with physical objects relies on information typing to increase interoperability. Two prototypes for mobile interaction with smart posters build upon this framework to realize multi-tag interaction with physical user interfaces. The authors' evaluation identifies usability issues regarding the design of physical mobile interactions, interfaces, and applications.

202 citations


Proceedings ArticleDOI
19 Apr 2009
TL;DR: The results show that the barrier coverage of the line-based deployments significantly outperforms that of the Poisson model when the random offsets are relatively small compared to the sensor's sensing range.
Abstract: Barrier coverage of wireless sensor networks has been studied intensively in recent years under the assumption that sensors are deployed uniformly at random in a large area (Poisson point process model). However, when sensors are deployed along a line (e.g., sensors are dropped from an aircraft along a given path), they would be distributed along the line with random off- sets due to wind and other environmental factors. It is important to study the barrier coverage of such line- based deployment strategy as it represents a more realistic sensor placement model than the Poisson point process model. This paper presents the first set of results in this direction. In particular, we establish a tight lower-bound for the existence of barrier coverage under line-based deployments. Our results show that the barrier coverage of the line-based deployments significantly outperforms that of the Poisson model when the random offsets are relatively small compared to the sensor's sensing range. We then study sensor deployments along multiple lines and show how barrier coverage is affected by the distance between adjacent lines and the random offsets of sensors. These results demonstrate that sensor deployment strategies have direct impact on the barrier coverage of wireless sensor networks. Different deployment strategies may result in significantly different barrier coverage. Therefore, in the planning and deployment of wireless sensor networks, the coverage goal and possible sensor deployment strategies must be carefully and jointly considered. The results obtained in this paper will provide important guidelines to the deployment and performance of wireless sensor networks for barrier coverage.

196 citations


Proceedings ArticleDOI
31 Mar 2009
TL;DR: This paper identifies a new class of vulnerabilities -- buffer overreads -- that occur in practice and that can be exploited to read parts of the memory contents of a process running a vulnerable application.
Abstract: Many countermeasures exist that attempt to protect against buffer overflow attacks on applications written in C and C++. The most widely deployed countermeasures rely on artificially introducing randomness in the memory image of the application. StackGuard and similar systems, for instance, will insert a random value before the return address on the stack, and Address Space Layout Randomization (ASLR) will make the location of stack and/or heap less predictable for an attacker.A critical assumption in these probabilistic countermeasures is that attackers cannot read the contents of memory. In this paper we show that this assumption is not always justified. We identify a new class of vulnerabilities -- buffer overreads -- that occur in practice and that can be exploited to read parts of the memory contents of a process running a vulnerable application. We describe in detail how to exploit an application protected by both ASLR and stack canaries, if the application contains both a buffer overread and a buffer overflow vulnerability.We also provide a detailed discussion of how this vulnerability affects other, less widely deployed probabilistic countermeasures such as memory obfuscation and instruction set randomization.

189 citations


Patent
Hiroyuki Ishii1, Anil Umesh1
22 Apr 2009
TL;DR: In this article, a mobile station transmits uplink data to a radio base station by using an uplink radio resource assigned to the mobile station by predetermined scheduling information, in a predetermined cycle.
Abstract: In a mobile communication method according to the present invention, a mobile station (UE) transmits uplink data to a radio base station by using an uplink radio resource assigned to the mobile station by predetermined scheduling information, in a predetermined cycle. The method includes the steps: (A) notifying, to the mobile station (UE), the predetermined cycle and information on the uplink radio resource; (B) notifying, to the mobile station (UE), the predetermined scheduling information; and (C) transmitting uplink data in the predetermined cycle by using the uplink radio resource assigned by the predetermined scheduling information, the transmission starting at a certain point determined on the basis of the received predetermined scheduling information. In the step (C), the predetermined scheduling information is discarded, when the information on the uplink radio resource and information notified by the predetermined scheduling information are inconsistent with each other.

181 citations


Proceedings ArticleDOI
29 May 2009
TL;DR: This work addresses the data gathering problem in WSNs, where routing is used in conjunction with CS to transport random projections of the data, and considers a number of popular transformations and finds that none of them are able to sparsify the data while being at the same time incoherent with respect to the routing matrix.
Abstract: Compressive Sensing (CS) shows high promise for fully distributed compression in wireless sensor networks (WSNs). In theory, CS allows the approximation of the readings from a sensor field with excellent accuracy, while collecting only a small fraction of them at a data gathering point. However, the conditions under which CS performs well are not necessarily met in practice. CS requires a suitable transformation that makes the signal sparse in its domain. Also, the transformation of the data given by the routing protocol and network topology and the sparse representation of the signal have to be incoherent, which is not straightforward to achieve in real networks. In this work we address the data gathering problem in WSNs, where routing is used in conjunction with CS to transport random projections of the data.We analyze synthetic and real data sets and compare the results against those of random sampling. In doing so, we consider a number of popular transformations and we find that, with real data sets, none of them are able to sparsify the data while being at the same time incoherent with respect to the routing matrix. The obtained performance is thus not as good as expected and finding a suitable transformation with good sparsification and incoherence properties remains an open problem for data gathering in static WSNs.

156 citations


Patent
11 Mar 2009
TL;DR: In this paper, the authors proposed a method and system for handoff in a wireless communication network, where a common handoff encryption key is generated by an authentication server and transmitted to a first access point and a second access point.
Abstract: The present invention provides a method and system for handoff in a wireless communication network. In one embodiment, a common handoff encryption key is generated by an authentication server and transmitted to a first access point and a second access point. The first access point transmits the handoff encryption key to a wireless terminal. The wireless terminal encrypts output data with the handoff encryption key. When the wireless terminal is associated with the second access point, the second access point decrypts data from the wireless terminal with the handoff encryption key. In a second embodiment, a handoff WEP key generation secret parameter is provided to a first and a second access point. Both access points generate a handoff WEP key as a function of the handoff WEP key generation secret parameter and an address of a wireless terminal. The first access point transmits the handoff WEP key to the wireless terminal. The second access point communicates data packets encrypted with the handoff WEP key with the wireless terminal.

150 citations


Proceedings ArticleDOI
17 May 2009
TL;DR: Results of power and energy consumption measurements conducted on mobile phones for 2G and 3G networks for text messaging and voice services imply that mobile phones should switch the network in dependency of the service used to save the maximum amount of energy.
Abstract: Over the last years mobile phones had a remarkable evolution. From a simple device for voice communication, it became a full blown multimedia device with multiple features and appealing services. In parallel with the introduction of novel services, mobile devices became more and more energy-hungry reducing the operational time for the user. To extend the battery life of mobile phones is one of the top priorities for mobile phones' manufacturers. This paper presents results of power and energy consumption measurements conducted on mobile phones for 2G and 3G networks. The services under investigation were text messaging, voice and data. The paper reports larger energy consumption in 3G networks for text messaging and voice services than energy consumption in 2G networks. On the other side the 3G networks become more energy friendly when large volumes of data have to be downloaded. The results imply that mobile phones should switch the network in dependency of the service used to save the maximum amount of energy. As this handover consumes energy, we include its analysis in our measurements.

140 citations


Proceedings ArticleDOI
19 Apr 2009
TL;DR: This work re-define the encoding rules in order to break the chains of linear combinations that cannot be decoded after one of the packets is lost and shows that sending uncoded packets at key times ensures that all the receivers are able to meet specific delay requirements with very high probability.
Abstract: Motivated by streaming applications with stringent delay constraints, we consider the design of online network coding algorithms with timely delivery guarantees. Assuming that the sender is providing the same data to multiple receivers over independent packet erasure channels, we focus on the case of perfect feedback and heterogeneous erasure probabilities. Based on a general analytical framework for evaluating the decoding delay, we show that existing ARQ schemes fail to ensure that receivers with weak channels are able to recover from packet losses within reasonable time. To overcome this problem, we re-define the encoding rules in order to break the chains of linear combinations that cannot be decoded after one of the packets is lost. Our results show that sending uncoded packets at key times ensures that all the receivers are able to meet specific delay requirements with very high probability.

132 citations


Journal ArticleDOI
TL;DR: A co-channel framework for the coexistence of orthogonal frequency division multiple access (OFDMA) based macrocell and femtocell wireless networks is proposed, based on utilizing the resource blocks of macrocell-associated mobile stations that are far away to a fem tocell base station (fBS), therefore avoiding strong interference that may occur between a Femtocell and close-by mMSs.
Abstract: Femtocells have a strong potential for increasing the efficiency and coverage of next-generation broadband wireless networks. In this paper, a co-channel framework for the coexistence of orthogonal frequency division multiple access (OFDMA) based macrocell and femtocell wireless networks is proposed. It is based on utilizing the resource blocks of macrocell-associated mobile stations (mMSs) that are far away to a femtocell base station (fBS), therefore avoiding strong interference that may occur between a femtocell and close-by mMSs. An avoidance method that jointly utilizes the spectrum sensing results as well as scheduling information obtained from the macrocell base station (mBS) is introduced. Moreover, the impact of inter-carrier interference (ICI) from the mMSs in the uplink is discussed and evaluated through simulations.

Patent
08 May 2009
TL;DR: In this article, a frequency assignment scheme for femtocells minimizes interference between a femtocell and a macrocell using a spectrum-sensing technique carried out by the Femtocells.
Abstract: A method and a communication system including femtocells within a macrocell efficiently manage interference between the different femtocells, and between each femtocell and a macrocell. An efficient frequency assignment scheme for the femtocells minimizes interference between a femtocell and a macrocell and among different femtocells using a spectrum-sensing technique carried out by the femtocells. The frequency assignment scheme selects a suitable channel from a set of candidate channels and ensures that the femtocell has an acceptable coverage area even when it is close to the macrocell base station (BS). The frequency assignment scheme favors a co-channel implementation to take advantage of the hand-off and cell search characteristics of the co-channel implementation. In one embodiment, a joint power control and frequency band assignment technique is used, which partitions the coverage area of the macrocell into an inner region, a power control region, and an outer region. Depending on a femtocell's location, it is assigned a certain power level and a frequency band. Power control may be used within the power-control region while, in the other regions, a fixed transmission power may be used.

Journal ArticleDOI
Yoshitsugu Yasui1
TL;DR: Test results in terms of brain wave state show that the pattern while driving is changed by specific activity such as when talking on a mobile phone, which can be used to distinguish levels of alertness so as to prevent or avoid hazardous situations.
Abstract: A technique for measuring the psychophysiological status of the human and associated applications based on normal brain signals are examined and evaluated. A small single-point dry electrode developed for mobile use can capture brainwave activity from among dense external and internal electrical noise, and subsequently extract targeted frequency components. Continuous measurements during day and night provide a brainwave profile including wake and sleep states that can consistently explain states of human awareness. Statistical evaluation provides psychophysiological state change patterns which can be used to distinguish levels of alertness so as to prevent or avoid hazardous situations. We have taken a typical daily activity, namely, driving a car, to examine the applicability of our proposed method. Test results in terms of brain wave state show that the pattern while driving is changed by specific activity such as when talking on a mobile phone.

Journal ArticleDOI
H. Okamoto1, K. Kitao1, S. Ichitsubo1
TL;DR: This paper measured and analyzed the building penetration loss at higher frequencies that are appropriate for the next-generation system and proposed a penetration loss prediction formula that is derived based on measurement results.
Abstract: In mobile communication systems, it is important to clarify the outdoor-to-indoor propagation loss (building penetration loss) characteristics to improve the quality of communication within buildings. This paper proposes a penetration loss prediction formula that is derived based on measurement results. We measured and analyzed the building penetration loss at higher frequencies that are appropriate for the next-generation system. We measured the propagation loss on 71 floors in 17 buildings in an urban area using four frequencies in the 800-MHz to 8-GHz band. The measurement results showed that the attenuation based on the penetration distance is 0.6 dB/m, the floor height gain is 0.6 dB/m, the constant value for the penetration loss is 10 dB, and there is no frequency dependence of the penetration loss in the frequency range from 0.8 to 8 GHz.

Proceedings ArticleDOI
30 Nov 2009
TL;DR: The approach dynamically adapts to non-stationary real world signals through the online estimation of their correlation properties in space and time and can be readily applied to other types of network infrastructures that require the online approximation of large and distributed data sets.
Abstract: In this paper we look at the problem of accurately reconstructing distributed signals through the collection of a small number of samples at a data gathering point. The techniques that we exploit to do so are Compressive Sensing (CS) and Principal Component Analysis (PCA). PCA is used to find transformations that sparsify the signal, which are required for CS to retrieve, with good approximation, the original signal from a small number of samples. Our approach dynamically adapts to non-stationary real world signals through the online estimation of their correlation properties in space and time; these are then exploited by PCA to derive the transformations for CS. The approach is tunable and robust, independent of the specific routing protocol in use and able to substantially outperform standard data collection schemes. The effectiveness of our recovery algorithm, in terms of number of transmissions in the network vs reconstruction error, is demonstrated for synthetic as well as for real world signals which we gathered from an actual wireless sensor network (WSN) deployment. We stress that our solution is not limited to WSNs, but can be readily applied to other types of network infrastructures that require the online approximation of large and distributed data sets.

Patent
06 Nov 2009
TL;DR: In this article, a mobile station according to the present invention includes: a dedicated signaling reception unit (12) configured to receive a dedicated signal including a priority for a frequency or a group of frequencies of each radio access network; and a camp-on processing unit (13) configurable to select a campon cell based on the priority or a radio quality in each cell, wherein when a predetermined flag is set to the dedicated signaling received by the dedicated signal reception unit, the camp-ON processing unit(13) is configured to select the camp on cell based upon the radio
Abstract: A mobile station according to the present invention includes: a dedicated signaling reception unit ( 12 ) configured to receive a dedicated signaling including a priority for a frequency or a group of frequencies of each radio access network; and a camp-on processing unit ( 13 ) configured to select a camp-on cell based on the priority or a radio quality in each cell, wherein when a predetermined flag is set to the dedicated signaling received by the dedicated signaling reception unit ( 12 ), the camp-on processing unit ( 13 ) is configured to select the camp-on cell based on the radio quality in each cell, from a plurality of cells that use a different frequency but reside within an identical radio access network, and to select the camp-on cell based on the priority included in the dedicated signaling, from a plurality of cells within a different radio access network.

Journal ArticleDOI
TL;DR: In this paper, a broadband planar reflectarray with parasitic dipoles is presented for wireless communication applications, which can effectively extend the reflection phase range beyond 360°, which overcomes the problem of an inadequate phase range when using thicker substrates for a wider operational bandwidth.
Abstract: A novel broadband planar reflectarray with parasitic dipoles is presented for wireless communication applications. A unit cell of the microstrip reflectarray consists of a printed main dipole with a pair of parasitic dipoles. The introduction of parasitic dipoles can effectively extend the reflection phase range beyond 360°, which overcomes the problem of an inadequate phase range when using thicker substrates for a wider operational bandwidth. The parasitic dipole reflectarrray (PDR) is applied to a wideband CDMA (WCDMA) system to eliminate blind spots in communication between the base station and mobile users. A practical link budget analysis demonstrates the effectiveness of the proposed planar reflectarray.

Proceedings ArticleDOI
26 Apr 2009
TL;DR: A femtocell architecture for LTE and investigates different handover scenarios are presented and two mobility management schemes at radio network layer (RNL) are proposed and their signaling cost, complexity, standard impact and application scenarios are discussed.
Abstract: Femtocell, a small cellular base station in home and small business environment, is an attractive solution for operators to improve indoor coverage and network capacity in 3G networks. However, there are technical problems due to its mass deployment. The paper presents a femtocell architecture for LTE and investigates different handover scenarios. Two mobility management schemes at radio network layer (RNL) are proposed and their signaling cost, complexity, standard impact and application scenarios are also discussed.

Patent
26 Jun 2009
TL;DR: In this paper, a distributed certificate authority includes a CA and a number of Sub-CAs (2610), each of which has secret certificate validation data, but different data are provided to different Sub-CA for each certificate.
Abstract: Different targets (c0, N1) of a digital certificate are mapped into a 'super-target' using methods allowing a certificate validity verifier (110) to compute the super-target. The certificate includes the super-target instead of the targets. Also, a certificate with multiple targets can be signed with a redactable signature by the certification authority (CA 120). When the certificate's owner provides the certificate to a verifier together with a validity proof, the owner redacts the certificate to delete unnecessary targets. A single validity proof (ci(F)) may be provided to certificate owners for a set (F) of the certificates via a multicast transmission if a multicasting group (2010) is formed to correspond to the set. A verifier (110) may decide to cache the validity proof for a set provide the cached proof to other parties. The caching decision is based on the caching priority of the set F. The priority may depend on the number of certificates in the set F, the sum of the remaining validity periods for the certificates in the set, and other factors. In the setup phase, the CA generates validation proof data structures for greater time than the maximum validity period of any certificate. Therefore, new certificates can be added to the existing data structures after the setup phase. A distributed certificate authority includes a CA and a number of Sub-CAs (2610). The Sub-CAs have secret certificate validation data, but different data are provided to different Sub-CAs for each certificate. If a Sub-CA is compromised, the Sub-CA validity proof will be withheld by the CA to alert the verifiers not to use the data from this Sub-CA. Also, the secret data are encrypted when distributed to the Sub-CAs. A decryption key (DK.j.k) for each 'partition' of time is distributed to each Sub-CA at or shortly before the start of the partition. A compromised Sub-CA can be reactivated at the end of the partition because the adversary does not get the decryption keys for the future partitions.

Proceedings ArticleDOI
13 Apr 2009
TL;DR: This paper introduces a primitive called sensor ranking to enable efficient search for sensors that have a certain output state at the time of the query and shows that sensor ranking can significantly improve the efficiency of content-based sensor search.
Abstract: The increasing penetration of the real world with embedded and globally networked sensors enables the formation of a Web of Things (WoT), where high-level state information derived from sensors is embedded into Web representations of real-world entities (e.g. places, objects). A key service for the WoT is searching for entities which exhibit a certain dynamic state at the time of the query, which is a challenging problem due to the dynamic nature of the sought state information and due to the potentially huge scale of the WoT. In this paper we introduce a primitive called sensor ranking to enable efficient search for sensors that have a certain output state at the time of the query. The key idea is to efficiently compute for each sensor an estimate of the probability that it matches the query and process sensors in the order of decreasing probability, such that effort is first spent on sensors that are very likely to actually match the query. Using real data sets, we show that sensor ranking can significantly improve the efficiency of content-based sensor search.

Proceedings ArticleDOI
Yong Bai1, Juejia Zhou1, Lan Chen1
30 Nov 2009
TL;DR: This paper investigates flexible spectrum usages for LTE network that consists of overlaying macrocell and femtocell and proposes hybrid spectrum usage to take advantage of their merits.
Abstract: This paper investigates flexible spectrum usages for LTE network that consists of overlaying macrocell and femtocell. In such a networking environment, shared spectrum usage and partitioned spectrum usage are two options to be employed between two radio tiers. After recognizing the pros and cons of these two usages, we propose hybrid spectrum usage to take advantage of their merits. In our proposal, the femtocells embedded in macrocell are differentiated to inner and outer femtocells, which operate in partitioned spectrum usage and shared spectrum usage, respectively. Analysis and performance evaluation are given to illustrate and justify our proposed method on improving spectrum utilization for wireless overlay network.

Patent
18 Jun 2009
TL;DR: In this paper, a femto base station according to the present invention includes: a downlink perch channel signal transmission power controller unit configured to change a transmission power of a DPN channel signal when a first condition is satisfied.
Abstract: A femto base station according to the present invention includes: a downlink perch channel signal transmission power controller unit configured to change a transmission power of a downlink perch channel signal when a first condition is satisfied; and an uplink reception sensitivity controller unit configured to change an uplink reception sensitivity when a second condition is satisfied after the first condition is satisfied.

Proceedings ArticleDOI
01 Sep 2009
TL;DR: This study investigates interference vs. bandwidth tradeoffs in different types of femtocell network deployments through the help of channel capacity formulations to compare the capacities of different deployment modes and the impact of key system parameters.
Abstract: Femtocell networks have the potential of significantly improving the capacity of next-generation cellular systems. However, interference to/from the macrocell network is a critical problem affecting the capacity. Co-channel operation with closed-subscriber group (CSG) access offers a large bandwidth to be shared by the users of the femtocell network; however, it also introduces significant interference to/from the macrocell network. On the other hand, femtocell networks using dedicated spectrum assignment and open access mode have insignificant interference concerns, with the trade-off of available spectrum limitations. In this study, we investigate interference vs. bandwidth tradeoffs in different types of femtocell network deployments through the help of channel capacity formulations. Related downlink simulation results are provided to compare the capacities of different deployment modes and the impact of key system parameters.

Proceedings ArticleDOI
01 Sep 2009
TL;DR: It is shown, despite prevailing views, that cellular architectures, using coordinated colocated antennas, can be quite attractive compared to Network MIMO.
Abstract: Cooperative base-station (BS) signaling using MU-MIMO (Network MIMO) has received a great deal of attention given its ability to reduce inter-cell interference (ICI) and improve the system spectral efficiency. Indeed for a given number of antennas per BS, cooperative systems can have significant benefits over conventional cellular architectures. However cooperative signaling requires and uses more channel state information (CSI). This increases CSI signaling overhead, and can have a non-negligible effect on the system throughput. In fact once systems are compared while taking into account CSI overhead, the question of what system architecture is best becomes interesting and non-trivial. We provide one such alternative look at cooperative architectures. We show, despite prevailing views, that cellular architectures, using coordinated colocated antennas, can be quite attractive compared to Network MIMO.

Journal ArticleDOI
TL;DR: The EPC specifications that use a network-based mobility mechanism based on Proxy Mobile IPv6 to enable mobility between access networks and an overview of the "off-path" QoS model to supplement PMIPv6 is provided.
Abstract: A key aspect of the 3GPP system architecture evolution is the specification of an evolved packet core that supports multiple access networks The EPC enables operators to deploy and operate one common packet core network for 3GPP radio accesses (E-UTRAN, UTRAN, and GERAN), as well as other wireless and wireline access networks (eg, eHRPD, WLAN, WIMAX, and DSL/Cable), providing the operator with a common set of services and capabilities across the networks A key requirement of the EPC is to provide seamless mobility at the IP layer as the user moves within and between accesses This article provides an overview of the EPC specifications that use a network-based mobility mechanism based on Proxy Mobile IPv6 to enable mobility between access networks An important facet of providing seamless mobility for a user's sessions across technologies is to ensure that quality of service is maintained as the user moves between accesses An overview of the "off-path" QoS model to supplement PMIPv6 is also provided

Proceedings ArticleDOI
02 Mar 2009
TL;DR: ProtoPeer is a peer-to-peer systems prototyping toolkit that allows for switching between the event-driven simulation and live network deployment without changing any of the application code.
Abstract: Simulators are a commonly used tool in peer-to-peer systems research. However, they may not be able to capture all the details of a system operating in a live network. Transitioning from the simulation to the actual system implementation is a non-trivial and time-consuming task. We present ProtoPeer, a peer-to-peer systems prototyping toolkit that allows for switching between the event-driven simulation and live network deployment without changing any of the application code. ProtoPeer defines a set of APIs for message passing, message queuing, timer operations as well as overlay routing and managing the overlay neighbors. Users can plug in their own custom implementations of most of the parts of ProtoPeer including custom network models for simulation and custom message passing over different network stacks. ProtoPeer is not only a framework for building systems but also for evaluating them. It has a unified system-wide infrastructure for event injection, measurement logging, measurement aggregation and managing evaluation scenarios. The simulator scales to tens of thousands of peers and gives accurate predictions closely matching the live network measurements.

Patent
Hiroyuki Ishii1, Anil Umesh1
01 May 2009
TL;DR: In this article, a radio base station includes a measurement unit which measures a resource use amount in each time frame within a predetermined period; a downlink persistent allocation signal transmission unit which transmits to a mobile station, a persistent assignment signal indicating a down-link radio resource allocation start moment; and downlink communication unit which transmit downlink data using downlink radio resources starting at the downlink Radio Resource Allocation start moment.
Abstract: A radio base station includes: a measurement unit which measures a resource use amount in each time frame within predetermined period; a downlink persistent allocation signal transmission unit which transmits to a mobile station, a persistent allocation signal indicating a downlink radio resource allocation start moment; and a downlink communication unit which transmit downlink data using downlink radio resource starting at the downlink radio resource allocation start moment. The downlink persistent allocation signal transmission unit decides the downlink radio resource allocation start moment in accordance with a resource use amount in each time frame.

Proceedings ArticleDOI
05 Jul 2009
TL;DR: This paper describes the SVEF, the first open-source framework for experimental assessment of H.264 Scalable Video coding streaming Evaluation Framework, and provides the experimental performance evaluation of an SVC cross-layer in-network scheduler in a Wireless LAN hot spot scenario.
Abstract: This paper describes the H.264 Scalable Video coding streaming Evaluation Framework (SVEF). This is the first open-source framework for experimental assessment of H.264 Scalable Video Coding (SVC) delivery over real networks. Effectively adapting of the transport of an H.264 SVC stream to time-varying, bandwidth constrained, and loss prone networks is an important research area. However, very little experimental work has been performed due to the unavailability of real-time H.264 SVC players, the limitations of existing decoding software libraries when challenged with network-imparied received SVC streams (e.g., affected by random loss of Network Abstraction Layer Units - NALUs), and the lack of solutions for SVC streaming support. SVEF overcomes these issues by developing missing components and by integrating them in a hybrid online/offline experimental framework. We believe SVEF will be of significant help to the research community interested in experimentally benchmarking their own proposed SVC adaptation approaches and delivery mechanisms. As a proof-of-concept of SVEF, we provide the experimental performance evaluation of an SVC cross-layer in-network scheduler in a Wireless LAN hot spot scenario.

Proceedings ArticleDOI
01 Nov 2009
TL;DR: In this article, the authors investigated the effect of channel state information (CSI) estimation overheads on the performance of cooperative multi-user MIMO systems and showed that CSI estimation does take physical layer resources from data and thus should be accounted for in assessing the net benefits of any cooperative signaling strategy.
Abstract: Cooperative Multi-User MIMO signaling across cells, also known as Network MIMO, has recently received a great deal of attention as a potential physical layer technique for future high-throughput wireless systems. Indeed, cooperative signaling is able to reduce inter-cell interference within groups of coordinated cells thereby improving system throughput. Such benefits, however, are often assessed ignoring inherent overheads such as those required to obtain channel state information (CSI) to enable downlink signaling by MU-MIMO. In fact CSI estimation does take physical layer resources from data and thus should be accounted for in assessing the net benefits of any cooperative signalling strategy. The paper characterizes some elements of this overhead and its effect on CSI estimation error and MU-MIMO efficiency. The results show that, when CSI overheads are taken into account, conventional cellular architectures, with no coordination across cells, can be quite attractive relative to Network MIMO.

Proceedings ArticleDOI
28 Dec 2009
TL;DR: The impact of femto-cell underlay deployment that share radio frequency resources with urban macro-cells is studied to mitigate destructive femto to macro-cell interference.
Abstract: This paper studies the impact of femto-cell underlay deployment that share radio frequency resources with urban macro-cells. Femto-cells promise substantial gains in spectral efficiency due to an enhanced reuse of radio resources. However, owing to their random and uncoordinated deployment, femtocells potentially cause destructive interference to macro-cells and vice versa. In order to maintain reliable service of macro-cells, it is most important to mitigate destructive femto to macro-cell interference. In the downlink, this can be achieved by dynamic resource partitioning, in the way that femto base stations (BS) are denied access to resources that are assigned to close by macro mobile stations (MS). By doing so, interference to the macro-cells is effectively controlled, at the expense of a modest degradation in femto-cell capacity. The necessary signalling is conveyed through the wired backbone, using a high interference indicator (HII).