Chinese University of Hong Kong

Displaying 1-40 of 133 results

  • White Papers // Apr 2014

    Degraded-First Scheduling for MapReduce in Erasure-Coded Storage Clusters

    The authors have witnessed an increasing adoption of erasure coding in modern clustered storage systems to reduce the storage overhead of traditional 3-way replication. However, it remains an open issue of how to customize the data analytics paradigm for erasure-coded storage, especially when the storage system operates in failure mode....

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2014

    Experiences Building Network-Coding-Based Distributed Storage Systems

    Large-scale distributed storage systems are prone to node failures. To provide fault tolerance, data is often encoded to maintain data redundancy over multiple storage nodes. If a node fails, it can be repaired by downloading data from surviving nodes and regenerating the lost data in a new node. Network coding...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2014

    Continuous Constraint Query Evaluation For Spatiotemporal Streams

    In this paper, the authors study the evaluation of Continuous Constraint Queries (CCQs) for spatiotemporal streams. A CCQ triggers an alert whenever a configuration of constraints between streaming events in space and time are satisfied. Consider, for instance, a server that receives updates from GPS-enabled agents that report their positions...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2014

    FPGA-Based SIMD Processor

    Although Field Programmable Gate Arrays (FPGAs) can have high performance gains over equivalent microprocessor based systems, they have the disadvantage that the design time is much higher than for an equivalent software based system. A massively parallel Single Instruction Multiple Data stream (SIMD) processor designed specifically for cryptographic key search...

    Provided By Chinese University of Hong Kong

  • White Papers // Sep 2013

    On the Speedup of Recovery in Large-Scale Erasure-Coded Storage Systems

    Modern storage systems stripe redundant data across multiple nodes to provide availability guarantees against node failures. One form of data redundancy is based on XOR-based erasure codes, which use only XOR operations for encoding and decoding. In addition to tolerating failures, a storage system must also provide fast failure recovery...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2013

    Top-K Nearest Keyword Search on Large Graphs

    k-NK is not only useful as a stand-alone query but also as a building block for tackling complex graph pattern matching problems. The key to an accurate k-NK result is precise shortest distance estimation in a graph. Based on the latest distance oracle technique, the authors build a shortest path...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2013

    NCCloud: A Network-Coding-Based Storage System in a Cloud-of-Clouds

    To provide fault tolerance for cloud storage, recent studies propose to stripe data across multiple cloud vendors. However, if a cloud suffers from a permanent failure and loses all its data, the authors need to repair the lost data with the help of the other surviving clouds to preserve data...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2013

    RevDedup: A Reverse Deduplication Storage System Optimized for Reads to Latest Backups

    De-duplication is known to effectively eliminate duplicates, yet it introduces fragmentation that degrades read performance. The authors propose RevDedup, a de-duplication system that optimizes reads to the latest backups of Virtual Machine (VM) images using reverse de-duplication. In contrast with conventional de-duplication that removes duplicates from new data, RevDedup removes...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2013

    Enabling Data Integrity Protection in Regenerating-Coding-Based Cloud Storage: Theory and Implementation

    To protect outsourced data in cloud storage against corruptions, adding fault tolerance to cloud storage, along with efficient data integrity checking and recovery procedures, becomes critical. Regenerating codes provide fault tolerance by striping data across multiple servers, while using less repair traffic than traditional erasure codes during failure recovery. Therefore,...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2013

    Limits of Provable Security for Homomorphic Encryption

    In this paper the authors revisit the question of basing cryptography on NP-hardness. If P equals NP then computationally secure encryption is impossible. Is the converse true? Despite considerable e orts, there is no candidate encryption scheme whose security can be plausibly reduced to the worst-case hardness of some NP-complete...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2013

    BASIC Regenerating Code: Binary Addition and Shift for Exact Repair

    Regenerating code is a class of storage codes that achieve the optimal trade-off between storage capacity and repair bandwidth, which are two important performance metrics in data storage systems. However, existing constructions of regenerating codes rely on expensive computational operations such as finite field multiplication. The high coding and repair...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2013

    Physical-Layer Multicasting by Stochastic Transmit Beamforming and Alamouti Space-Time Coding

    Consider transceiver designs in a multiuser Multi-Input Single-Output (MISO) downlink channel, where the users are to receive the same data stream simultaneously. This problem, known as physical-layer multicasting, has drawn much interest. Presently, a popularized approach is transmit beamforming, in which the beamforming optimization is handled by a rank-one approximation...

    Provided By Chinese University of Hong Kong

  • White Papers // Apr 2013

    Transmission Sequence Design and Allocation for Wide Area Ad Hoc Networks

    In this paper, the authors examine the question of designing and allocating transmission sequences to users in a mobile ad hoc network that has no spatial boundary. A basic tenet of the transmission sequence approach for addressing the media access control problem is that under normal operation conditions, there is...

    Provided By Chinese University of Hong Kong

  • White Papers // Mar 2013

    Multi-Group Multicast Beamforming in Cognitive Radio Networks Via Rank-Two Transmit Beamformed Alamouti Space-Time Coding

    In this paper, the authors consider transmit design in Multiple-Input Single-Output (MISO) Multi-group Multicast (MM) Cognitive Radio (CR) systems. Previously, Semi-Definite Relaxation (SDR)-based transmit beamforming has been very successful in transmit design. However, recent research shows that further performance gain is possible by suitably modifying the transmit structure. Here, they...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    A Cooperative Game Based Allocation for Sharing Data Center Networks

    In current IaaS datacenters, tenants are suffering unfairness since the network bandwidth is shared in a best-effort manner. To achieve predictable network performance for rented Virtual Machines (VMs), cloud providers should guarantee minimum bandwidth for VMs or allocate the network bandwidth in a fairness fashion at VM-level. At the same...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    An Experimental Study of Cascading Performance Interference in a Virtualized Environment

    In a consolidated virtualized environment, multiple Virtual Machines (VMs) are hosted atop a shared physical substrate. They share the underlying hardware resources as well as the software virtualization components. Thus, one VM can generate performance interference to another co-resident VM. This paper explores the adverse impact of performance interference from...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    Moving Big Data to the Cloud

    Cloud computing, rapidly emerging as a new computation paradigm, provides agile and scalable resource access in a utility-like fashion, especially for the processing of big data. An important open issue here is how to efficiently move the data, from different geographical locations over time, into a cloud for effective processing....

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    Coding for Linear Operator Channels Over Finite Fields

    Linear Operator Channels (LOCs) are motivated by the communications through networks employing Random Linear Network Coding (RLNC). Following the recent information theoretic results about LOCs, the authors propose two coding schemes for LOCs and evaluate their performance. These schemes can be used in networks employing RLNC without constraints on the...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    Construction of Linear Network Codes That Achieve a Rened Singleton Bound

    The network error correction problem study is to extend classical error correction coding theory to a general network setting. In Cai and Yeung, network generalizations of the Hamming bound, the Singleton bound, and the Gilbert-Varshamov bound in classical algebraic coding theory were obtained. In particular, the tightness of the Singleton...

    Provided By Chinese University of Hong Kong

  • White Papers // Dec 2012

    Upper Bounds on the Capacity of Binary Channels With Causal Adversaries

    Alice wishes to transmit a message u to Bob over a binary-input binary-output channel. To do so, she encodes u into a length-n binary vector x and transmits it over the channel. However, the channel is controlled by a malicious adversary Calvin who may observe the transmissions, and attempts to...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2012

    Single Disk Failure Recovery for X-code-based Parallel Storage Systems

    In modern parallel storage systems (e.g., cloud storage and data centers), it is important to provide data availability guarantees against disk (or storage node) failures via redundancy coding schemes. One coding scheme is X-code, which is double-fault tolerant while achieving the optimal update complexity. When a disk/node fails, recovery must...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2012

    Spectrum Broker by Geo-Location Database

    Geo-location database driven white space network is a very promising approach for improving secondary spectrum utilization. In this paper, the authors consider the business modeling for geo-location database driven white space network. In their proposed model, the database acts as a spectrum broker buying (reserving) bandwidth from spectrum licensees in...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2012

    Blind Known Interference Cancellation With Parallel Real Valued Belief Propagation Algorithm

    This paper investigates interference-cancellation schemes at the receiver, in which the original data of the interference is known a priori. Such a priori knowledge is common in wireless relay networks. Directly removing the known interference requires accurate estimate of the interference channel, which may be difficult in many situations. The...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    Simple and E Ective Dynamic Provisioning for Power-Proportional Data Centers

    Energy consumption represents a significant cost in data center operation. A large fraction of the energy, however, is used to power idle servers when the workload is low. Dynamic provisioning techniques aim at saving this portion of the energy, by turning o unnecessary servers. In this paper, the authors explore...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    Analysis and Construction of Functional Regenerating Codes With Uncoded Repair for Distributed Storage Systems

    Modern distributed storage systems apply redundancy coding techniques to stored data. One form of redundancy is based on regenerating codes, which can minimize the repair bandwidth, i.e., the amount of data transferred when repairing a failed storage node. Existing regenerating codes mainly require surviving storage nodes encode data during repair....

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    A Scalable Algorithm for Maximizing Range Sum in Spatial Databases

    This paper investigates the MaxRS problem in spatial databases. Given a set O of weighted points and a rectangular region r of a given size, the goal of the MaxRS problem is to find a location of r such that the sum of the weights of all the points covered...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2012

    Utility Maximization in Peer-to-Peer Systems with Applications to Video Conferencing

    In this paper, the authors study the problem of utility maximization in P2P systems, in which aggregate application specific utilities are maximized by running distributed algorithms on P2P nodes, which are constrained by their uplink capacities. For certain P2P topologies, they show that routing along a linear number of trees...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2012

    Analog Network Coding in General SNR Regime: Performance of Network Simplification

    A communication scenario where a source communicates with a destination over a directed layered relay network is considered. Each relay performs analog network coding where it scales and forwards the signals received at its input. In this scenario, the authors address the question: What portion of the maximum end-to-end achievable...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Secure Overlay Cloud Storage With Access Control and Assured Deletion

    The authors can now outsource data backups off-site to third-party cloud storage services so as to reduce data management costs. However, they must provide security guarantees for the outsourced data, which is now maintained by third parties. They design and implement FADE, a secure overlay cloud storage system that achieves...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Optical Physical-Layer Network Coding

    Physical-layer Network Coding (PNC) has been an active research area in both information theory and wireless communications in the past few years. However, its application in optical communications has not yet been explored. This paper proposes and demonstrates a practical optical PNC prototype for multicast protection in optical flow/burst/packet switching...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Functional-Repair-by-Transfer Regenerating Codes

    In a distributed storage system, a data file is distributed to several storage nodes, such that the original file can be decoded from any subset of the storage nodes of size larger than or equal to a certain threshold. Upon the failure of a storage node, the authors would like...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Congestion Games on Weighted Directed Graphs, With Applications to Spectrum Sharing

    With the advance of complex large-scale networks, it is becoming increasingly important to understand how selfish and spatially distributed individuals will share network resources without centralized co-ordinations. In this paper, the authors introduce the Graphical Congestion Game with Weighted Edges (GCGWE) as a general theoretical model to study this problem....

    Provided By Chinese University of Hong Kong

  • White Papers // May 2012

    Mitigating Power Law Delays: the Use of Polynomial Backoff in IEEE 802.11 DCF

    The IEEE 802:11 Wireless Local Area Network (WLAN) standard was originally designed for best-effort services, targeting at providing high throughput and throughput fairness. However, high system throughput does not necessarily translate to good delay performance. Recent studies show that exponential backoff, the key collision avoidance mechanism in Distributed Coordination Function...

    Provided By Chinese University of Hong Kong

  • White Papers // Apr 2012

    A Game Theoretic Analysis on Incentive Mechanisms for Wireless Ad Hoc VoD Systems

    Wireless ad hoc networks enable the wireless devices to directly communicate with each other. An emerging application in such systems is video-on-demand service that can greatly reduce the content server's workload by utilizing the nodes' resources. Such an application relies on the cooperation of all participating nodes. However, the nodes...

    Provided By Chinese University of Hong Kong

  • White Papers // Feb 2012

    Implementation of Physical-Layer Network Coding

    This paper presents the first implementation of a two-way relay network based on the principle of physical layer network coding. To date, only a simplified version of Physical-layer Network Coding (PNC), called Analog Network Coding (ANC), has been successfully implemented. The advantage of ANC is that it is simple to...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    A Unification of Network Coding and Routing

    For a linear network code, the encoding profile is specified by, for every output channel of a node, the set of input channels whose symbols upon which the symbol on the output channel depends. For a given single-source network coding problem, it is of fundamental interest to characterize all feasible...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    NCCloud: Applying Network Coding for the Storage Repair in a Cloud-of-Clouds

    To provide fault tolerance for cloud storage, recent studies propose to stripe data across multiple cloud vendors. However, if a cloud suffers from a permanent failure and loses all its data, then the authors need to repair the lost data from other surviving clouds to preserve data redundancy. They present...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    Rank-Two Transmit Beamformed Alamouti Space-Time Coding for Physical-Layer Multicasting

    In physical-layer multicasting over a multiuser MISO downlink channel, transmit beamforming using Semi-Definite Relaxation (SDR) has been a popular approach. In this paper, the authors propose a rank-2 transmit beamformed Alamouti space-time code scheme, which may be seen as a generalization of the previous SDR-based beamforming framework. The beamforming problem...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    Incentive Mechanisms for Smartphone Collaboration in Data Acquisition and Distributed Computing

    This paper analyzes and compares different incentive mechanisms for a client to motivate the collaboration of smartphone users on both data acquisition and distributed computing applications. Data acquisition from a large number of users is essential to build a rich database and support emerging location-based services. The authors propose a...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    Spectrum Mobility Games

    Cognitive radio gives users the ability to switch channels and make use of dynamic spectrum opportunities. However, switching channels takes time, and may affect the quality of a user's transmission. When a cognitive radio user's channel becomes unavailable, sometimes it may be better waiting until its current channel becomes available...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    Spectrum Mobility Games

    Cognitive radio gives users the ability to switch channels and make use of dynamic spectrum opportunities. However, switching channels takes time, and may affect the quality of a user's transmission. When a cognitive radio user's channel becomes unavailable, sometimes it may be better waiting until its current channel becomes available...

    Provided By Chinese University of Hong Kong

  • White Papers // Feb 2011

    P2P Streaming Capacity

    Peer-To-Peer (P2P) systems provide a scalable way to stream content to multiple receivers over the Internet. The maximum rate achievable by all receivers is the capacity of a P2P streaming session. The authors provide a taxonomy of sixteen problem formulations, depending on whether there is a single P2P session or...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2011

    Amplify-and-Forward in Wireless Relay Networks

    A general class of wireless relay networks with a single source-destination pair is considered. Intermediate nodes in the network employ an amplify-and-forward scheme to relay their input signals. In this case the overall input-output channel from the source via the relays to the destination effectively behaves as an inter-symbol interference...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2011

    Distributed Optimization for Combinatorial Coding Subgraph Selection Problems

    Many network design cases with network coding can be formulated as combinatorial optimization problems, which are NP-hard and hard to approximate even in a centralized manner. In this paper, guided by Markov approximation framework, the authors provide a unified distributed solution for one important subcategory of combinatorial network coding problems:...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2011

    On the Role of Network Coding in Uncoordinated Multihop Content Distribution Over Ad Hoc Networks

    The authors consider the problem of multi-hop communication in ad hoc networks. This work was originally motivated by vehicular networks, and has application in numerous fields. The key constraint in such systems is the infeasibility of coordination. Because no single node has global knowledge of the network topology, centralized scheduling...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2011

    Celerity: A Low-Delay Multi-Party Conferencing Solution

    In this paper, the authors attempt to revisit the problem of multi-party conferencing from a practical perspective, and to rethink the design space involved in this problem. They believe that an emphasis on low end-to-end delays between any two parties in the conference is a must, and the source sending...

    Provided By Chinese University of Hong Kong

  • White Papers // Sep 2010

    Optimal Distributed P2P Streaming Under Node Degree Bounds

    The authors study the problem of maximizing the broadcast rate in Peer-To-Peer (P2P) systems under node degree bounds, i.e., the number of neighbors a node can simultaneously connect to is upper-bounded. The problem is critical for supporting high-quality video streaming in P2P systems, and is challenging due to its combinatorial...

    Provided By Chinese University of Hong Kong

  • White Papers // Apr 2009

    Queuing Models for Peer-to-Peer Systems

    Recent development of Peer-To-Peer (P2P) services (e.g. streaming, file sharing, and storage) systems introduces a new type of queue systems not studied before. In these new systems, both job and server arrive and depart randomly. The server dynamics may or may not correlate to the job dynamics. Motivated by these...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2010

    On Resource Management for Cloud Users: A Generalized Kelly Mechanism Approach

    Cloud computing provides network software companies with a platform to develop Software as a Service (SaaS) applications. The pay-as-you-go pricing model unties these SaaS providers from large capital outlays in hardware deployment and maintenance. Depending on the level of virtualization and service abstraction, cloud vendors provide different functionalities to the...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2011

    Secure Compressed Reading in Smart Grids

    Smart Grids measure energy usage in real-time and tailor supply and delivery accordingly, in order to improve power transmission and distribution. For the grids to operate effectively, it is critical to collect readings from massively installed smart meters to control centers in an efficient and secure manner. In this paper,...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2011

    Homomorphic Encryption From Codes

    The authors propose a new homomorphic encryption scheme based on the hardness of decoding under independent random noise from certain affine families of codes. Unlike in previous lattice-based homomorphic encryption schemes, where the message is hidden in the noisy part of the ciphertext, their scheme carries the message in the...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    NCCloud: Applying Network Coding for the Storage Repair in a Cloud-of-Clouds

    To provide fault tolerance for cloud storage, recent studies propose to stripe data across multiple cloud vendors. However, if a cloud suffers from a permanent failure and loses all its data, then the authors need to repair the lost data from other surviving clouds to preserve data redundancy. They present...

    Provided By Chinese University of Hong Kong

  • White Papers // Apr 2012

    A Game Theoretic Analysis on Incentive Mechanisms for Wireless Ad Hoc VoD Systems

    Wireless ad hoc networks enable the wireless devices to directly communicate with each other. An emerging application in such systems is video-on-demand service that can greatly reduce the content server's workload by utilizing the nodes' resources. Such an application relies on the cooperation of all participating nodes. However, the nodes...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Secure Overlay Cloud Storage With Access Control and Assured Deletion

    The authors can now outsource data backups off-site to third-party cloud storage services so as to reduce data management costs. However, they must provide security guarantees for the outsourced data, which is now maintained by third parties. They design and implement FADE, a secure overlay cloud storage system that achieves...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Congestion Games on Weighted Directed Graphs, With Applications to Spectrum Sharing

    With the advance of complex large-scale networks, it is becoming increasingly important to understand how selfish and spatially distributed individuals will share network resources without centralized co-ordinations. In this paper, the authors introduce the Graphical Congestion Game with Weighted Edges (GCGWE) as a general theoretical model to study this problem....

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2012

    Utility Maximization in Peer-to-Peer Systems with Applications to Video Conferencing

    In this paper, the authors study the problem of utility maximization in P2P systems, in which aggregate application specific utilities are maximized by running distributed algorithms on P2P nodes, which are constrained by their uplink capacities. For certain P2P topologies, they show that routing along a linear number of trees...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2008

    Design and Analysis of ISP-Friendly File Distribution Protocols

    In recent years, BitTorrent-like file-swarming applications are becoming so popular that they contribute to a large percentage of the current Internet traffic. Internet Service Providers (ISPs) not only need to cope with this traffic engineering problem, e.g., when and how to increase their network capacity, but more importantly, these P2P...

    Provided By Chinese University of Hong Kong

  • White Papers // Feb 2012

    Implementation of Physical-Layer Network Coding

    This paper presents the first implementation of a two-way relay network based on the principle of physical layer network coding. To date, only a simplified version of Physical-layer Network Coding (PNC), called Analog Network Coding (ANC), has been successfully implemented. The advantage of ANC is that it is simple to...

    Provided By Chinese University of Hong Kong

  • White Papers // Jun 2012

    Optical Physical-Layer Network Coding

    Physical-layer Network Coding (PNC) has been an active research area in both information theory and wireless communications in the past few years. However, its application in optical communications has not yet been explored. This paper proposes and demonstrates a practical optical PNC prototype for multicast protection in optical flow/burst/packet switching...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2011

    Binary Error Correcting Network Codes

    The authors consider network coding for networks experiencing worst-case bit-flip errors, and argue that this is a reasonable model for highly dynamic wireless network transmissions. They demonstrate that in this setup prior network error-correcting schemes can be arbitrarily far from achieving the optimal network throughput. They propose a new metric...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2011

    Low-Complexity Near-Optimal Codes for Gaussian Relay Networks

    The authors consider the problem of information flow over Gaussian relay networks. Similar to the recent work by Avestimehr et al., they propose network codes that achieve up to a constant gap from the capacity of such networks. However, their proposed codes are also computationally tractable. Their main technique is...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2010

    Concatenated Polar Codes

    Polar codes have attracted much recent attention as the first codes with low computational complexity that provably achieve optimal rate-regions for a large class of information-theoretic problems. One significant drawback, however, is that for current constructions the probability of error decays sub-exponentially in the block-length (more detailed designs improve the...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2012

    Mitigating Power Law Delays: the Use of Polynomial Backoff in IEEE 802.11 DCF

    The IEEE 802:11 Wireless Local Area Network (WLAN) standard was originally designed for best-effort services, targeting at providing high throughput and throughput fairness. However, high system throughput does not necessarily translate to good delay performance. Recent studies show that exponential backoff, the key collision avoidance mechanism in Distributed Coordination Function...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    A Scalable Algorithm for Maximizing Range Sum in Spatial Databases

    This paper investigates the MaxRS problem in spatial databases. Given a set O of weighted points and a rectangular region r of a given size, the goal of the MaxRS problem is to find a location of r such that the sum of the weights of all the points covered...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    Analysis and Construction of Functional Regenerating Codes With Uncoded Repair for Distributed Storage Systems

    Modern distributed storage systems apply redundancy coding techniques to stored data. One form of redundancy is based on regenerating codes, which can minimize the repair bandwidth, i.e., the amount of data transferred when repairing a failed storage node. Existing regenerating codes mainly require surviving storage nodes encode data during repair....

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    Moving Big Data to the Cloud

    Cloud computing, rapidly emerging as a new computation paradigm, provides agile and scalable resource access in a utility-like fashion, especially for the processing of big data. An important open issue here is how to efficiently move the data, from different geographical locations over time, into a cloud for effective processing....

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2012

    Spectrum Broker by Geo-Location Database

    Geo-location database driven white space network is a very promising approach for improving secondary spectrum utilization. In this paper, the authors consider the business modeling for geo-location database driven white space network. In their proposed model, the database acts as a spectrum broker buying (reserving) bandwidth from spectrum licensees in...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2012

    Blind Known Interference Cancellation With Parallel Real Valued Belief Propagation Algorithm

    This paper investigates interference-cancellation schemes at the receiver, in which the original data of the interference is known a priori. Such a priori knowledge is common in wireless relay networks. Directly removing the known interference requires accurate estimate of the interference channel, which may be difficult in many situations. The...

    Provided By Chinese University of Hong Kong

  • White Papers // Apr 2013

    Transmission Sequence Design and Allocation for Wide Area Ad Hoc Networks

    In this paper, the authors examine the question of designing and allocating transmission sequences to users in a mobile ad hoc network that has no spatial boundary. A basic tenet of the transmission sequence approach for addressing the media access control problem is that under normal operation conditions, there is...

    Provided By Chinese University of Hong Kong

  • White Papers // Aug 2012

    Simple and E Ective Dynamic Provisioning for Power-Proportional Data Centers

    Energy consumption represents a significant cost in data center operation. A large fraction of the energy, however, is used to power idle servers when the workload is low. Dynamic provisioning techniques aim at saving this portion of the energy, by turning o unnecessary servers. In this paper, the authors explore...

    Provided By Chinese University of Hong Kong

  • White Papers // Jul 2012

    Analog Network Coding in General SNR Regime: Performance of Network Simplification

    A communication scenario where a source communicates with a destination over a directed layered relay network is considered. Each relay performs analog network coding where it scales and forwards the signals received at its input. In this scenario, the authors address the question: What portion of the maximum end-to-end achievable...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2013

    Physical-Layer Multicasting by Stochastic Transmit Beamforming and Alamouti Space-Time Coding

    Consider transceiver designs in a multiuser Multi-Input Single-Output (MISO) downlink channel, where the users are to receive the same data stream simultaneously. This problem, known as physical-layer multicasting, has drawn much interest. Presently, a popularized approach is transmit beamforming, in which the beamforming optimization is handled by a rank-one approximation...

    Provided By Chinese University of Hong Kong

  • White Papers // Mar 2013

    Multi-Group Multicast Beamforming in Cognitive Radio Networks Via Rank-Two Transmit Beamformed Alamouti Space-Time Coding

    In this paper, the authors consider transmit design in Multiple-Input Single-Output (MISO) Multi-group Multicast (MM) Cognitive Radio (CR) systems. Previously, Semi-Definite Relaxation (SDR)-based transmit beamforming has been very successful in transmit design. However, recent research shows that further performance gain is possible by suitably modifying the transmit structure. Here, they...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2012

    Rank-Two Transmit Beamformed Alamouti Space-Time Coding for Physical-Layer Multicasting

    In physical-layer multicasting over a multiuser MISO downlink channel, transmit beamforming using Semi-Definite Relaxation (SDR) has been a popular approach. In this paper, the authors propose a rank-2 transmit beamformed Alamouti space-time code scheme, which may be seen as a generalization of the previous SDR-based beamforming framework. The beamforming problem...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2011

    Safe Convex Approximation to Outage-Based MISO Secrecy Rate Optimization Under Imperfect CSI and With Artificial Noise

    Consider a scenario in which an MISO channel is overheard by multiple single-antenna eavesdroppers. The transmitter has perfect Channel State Information (CSI) with the legitimate channel, but has imperfect CSI with the eavesdroppers' channels. The CSI uncertainties are assumed stochastic. The authors formulate an Artificial-Noise (AN)- aided secrecy-rate maximization problem...

    Provided By Chinese University of Hong Kong

  • White Papers // Feb 2011

    Cheap Semidefinite Relaxation MIMO Detection Using Row-by-Rowblock Coordinate Descent

    This paper considers the problem of low complexity implementation of high-performance Semi-Definite Relaxation (SDR) MIMO detection methods. Currently, most SDR MIMO detectors are implemented using interior-point methods. Although, such implementations have worst-case polynomial complexity (approximately cubic in the problem size), they can be quite computationally costly in practice. Here, the...

    Provided By Chinese University of Hong Kong

  • White Papers // Oct 2009

    Probabilistic Analysis of the Semidefinite Relaxation Detector in Digital Communications

    A fundamental problem in modern digital communication is that of the joint detection of several information carrying symbols that are being transmitted over a Multiple-Input Multiple-Output (MIMO) communication channel. Such a problem arises in many contexts. For instance, consider a wireless communication setting, where there are multiple antennae at both...

    Provided By Chinese University of Hong Kong

  • White Papers // May 2011

    On the Security and Efficiency of Content Distribution via Network Coding

    Content distribution via network coding has received a lot of attention lately. However, direct application of network coding may be insecure. In particular, attackers can inject "Bogus" data to corrupt the content distribution process so as to hinder the information dispersal or even deplete the network resource. Therefore, content verification...

    Provided By Chinese University of Hong Kong

  • White Papers // Jan 2013

    A Cooperative Game Based Allocation for Sharing Data Center Networks

    In current IaaS datacenters, tenants are suffering unfairness since the network bandwidth is shared in a best-effort manner. To achieve predictable network performance for rented Virtual Machines (VMs), cloud providers should guarantee minimum bandwidth for VMs or allocate the network bandwidth in a fairness fashion at VM-level. At the same...

    Provided By Chinese University of Hong Kong

  • White Papers // Nov 2011

    On Detecting Malicious Behaviors in Interactive Networks: Algorithms and Analysis

    Interactive networks are vulnerable to various attacks due to the existence of malicious nodes which do not comply with the network protocol so as to achieve their own purposes. For example, in a Peer-To-Peer (P2P) streaming system, since each peer needs to participate in uploading data to other peers, malicious...

    Provided By Chinese University of Hong Kong