A Differential Evolution Clustering algorithm with weighted validity function is presented in this paper, five validity
functions are selected to form the fitness function with weights, and in selection of Differential Evolution, individuals
not being selected are put into secondary population. During evolution, individuals in secondary population replace those
in main population if their fitness values are less than those in main population. We have carried out experiments on 3
datasets from UCI machine learning repository and compared validity results to those from K-Means and classical
Differential Evolution, experimental results show that our approach can improve clustering performance.
An important goal in P2P networks is that all peers provide resources. However, free riding and tragedy of common are real issues in P2P networks. To resolve these problems, most of the existing work is concerning probabilistic estimation to evaluate the trustworthiness or mechanism design to provide incentive. Instead of design a protocol to solve free riding, we build a micro-payment architecture for these existing protocols using virtual currency which can be more precisely measured and easily be replaced by reputation or other tokens. Our system can avoid from long-term trust learning interactions and high cost of collecting and analyzing reputation information. It can also provide peers incentive to truly report their connection type and security to malicious attacks.
Efficient organization of the nodes in decentralized peer-to-peer (P2P) networks is a challenging problem, especially in
the absence of a global schema. Node clustering is an available way to optimize infrastructure and decrease traffic cost in
P2P networks. This paper proposes a Density-based Distributed Node Clustering (DDNC) approach to discovering
clusters in P2P networks. This approach is completely distributed, in which each node only depends on the knowledge of
its neighbors for node clustering. Unlike other graph based algorithms, the DDNC approach utilizes density of node's
neighbor for discovering clusters. For a given node, the DDNC determines its neighbor density by computing the link
time with its neighbors, which not only considers the node connectivity but also connection quality. The DDNC scheme
can also dynamically adapt its clusters according to the participation and departure of nodes. Experimental results have
shown ours scheme's feasibility and efficiency.
Today, the main traffic in peer-to-peer (P2P) network is still multimedia files including large numbers of music files. The study of Music Information Retrieval (MIR) brings out many encouraging achievements in music search area. Nevertheless, the research of music search based on MIR in P2P network is still insufficient. Query by Humming (QBH) is one MIR technology studied for years. In this paper, we present a server based P2P music sharing system which is based on QBH and integrated with a Hierarchical Index Structure (HIS) to enhance the relation between surface data and potential information. HIS automatically evolving depends on the music related items carried by each peer such as midi files, lyrics and so forth. Instead of adding large amount of redundancy, the system generates a bit of index for multiple search input which improves the traditional keyword-based text search mode largely. When network bandwidth, speed, etc. are no longer a bottleneck of internet serve, the accessibility and accuracy of information provided by internet are being more concerned by end users.
The scheme of dynamic coordination rules in peer-to-peer database uses rule caching and forwarding to successfully solve the dependence tree break problem in the situation that peers can join and leave freely. But there are still problems that weaken the performance of query processing in this scheme. Coordination rules in cache are merged in run time when bypassing break points. If dependence trees can be optimized into a form robust against peer absence beforehand, the query process will be more efficient. This paper proposes such mechanism by doing coordination rule combinations when new peer joins the dependence tree and new forwarded coordination rule arrives in cache. When some peers leave, queries take one existing bypass rule for reformulation, instead of concatenating cached ones from scratch. In effect, this mechanism optimizes dependence tree into a more robust topology whenever new peer joins. Even when there is no peer absence, bypass rules can make query processing more efficient without following through many mediating peers, especially when data are updated frequently and frequent queries are needed. At the same time, the original dependence tree are maintained for data cache query when the target peer is absent. Since dynamic coordination rules are expressed in XSLT, we try to find a way to form one XSLT whose function is equal to a chain of XSLTs, similar to the XML reasoning. The protocol also needs to be improved to inform to launch topology optimization when new peer join or rule changes.
Chord which used in structured P2P network is a successful routing algorithm based on DHT (Distributed Hash Table).
In Chord nodes locate along the Chord ring by being assigned the node identifiers and data store in corresponding nodes
with key identifier. Finger table is built in each node and is maintained when nodes join and depart. The problems in
Chord are unidirectional clockwise routing along ring and information redundancy in routing table. An improved method
is presented which is bidirectional routing table. Routing can perform along clockwise and anticlockwise according to
the locations of the current node and destination node. The next hop direction is optimization that the next node is the
nearest one apart from the destination node. This strategy limits the search area in half-ring, reduces the average hops
and enhances the search efficiency. The redundancy routing information is deleted in order to decrease the added storage
space in bidirectional routing table, thus the items share the routing information.
Building a semantic search system on top of peer-to-peer (P2P) networks is becoming an attractive and promising
alternative scheme for the reason of scalability, Data freshness and search cost. In this paper, we present a Suffix Arrays
based algorithm for Semantic Search (SASS) in P2P systems, which generates a distributed Semantic Overlay Network
(SONs) construction for full-text search in P2P networks. For each node through the P2P network, SASS distributes
document indices based on a set of suffix arrays, by which clusters are created depending on words or phrases shared
between documents, therefore, the search cost for a given query is decreased by only scanning semantically related
documents. In contrast to recently announced SONs scheme designed by using metadata or predefined-class, SASS is an
unsupervised approach for decentralized generation of SONs. SASS is also an incremental, linear time algorithm, which
efficiently handle the problem of nodes update in P2P networks. Our simulation results demonstrate that SASS yields
high search efficiency in dynamic environments.
Peer-to-Peer (P2P) systems are currently receiving considerable interest. However, as experience with P2P networks shows, the selfish behaviors of peers may lead to serious problems of P2P network, such as free-riding and white-washing. In order to solve these problems, there are increasing considerations on reputation system
design in the study of P2P networks. Most of the existing works is concerning probabilistic estimation or social
networks to evaluate the trustworthiness for a peer to others. However, these models can not be efficient all the
time. In this paper, our aim is to provide a general mechanism that can maximize P2P networks social welfare in
a way of Vickrey-Clarke-Groves family, while assuming every peer in P2P networks is rational and selfish, which
means they only concern about their own outcome. This mechanism has some desirable properties using an <i>O</i>(<i>n</i>)
algorithm: (1) incentive compatibility, every peer truly report its connection type; (2) individually rationality;
and (3) fully decentralized, we design a multiple-principal multiple-agent model, concerning about the service
provider and service requester individually.
DHT (Distributed Hash Table) is the key technology in structured P2P. DHT sets up logic topology with certain structure
among the nodes and builds relations between nodes and data resources according to some rules. Routing table structure
based on B<sup>+</sup> tree for DHT is presented which builds up the balanced multilevel ordered tree-indexes to the routing tables
so as to form levels indexes and ordered link between nodes. In term of this method, key search performs along the
ordered indexes in B<sup>+</sup> tree and the problem of resources location which is the core problem in DHT network is resolved
efficiently. This Routing table structure is of advantaged to manage numerous routing information in network and makes
the ruleless information well-regulated. It not only enhances the lookup efficiency and achieves the range search but also
can control the lookup length in the height of B<sup>+</sup> tree. When nodes join and depart, index structure can make the
maintained routing information few in each node by updating linked message only. At the same time, for linked
information of successor node being mainly stored in every node, the storage cost is decreased. It is effective and
scalable routing table structure.
P2P systems are usually used for information exchange between peers in recent years. However, the open and anonymous nature of a P2P network makes it an ideal medium for malicious peers. There is a lack of efficient mechanism for existing P2P systems to avoid from free riding, whitewashing, collusion and malicious attackers. In this paper, we describe a novel role-base trust model for P2P file sharing system. First, we give object criteria to track each peer's contribution to the system. Second, according to their contribution we divide all the peers into 2 parts: super peers and normal peers. Each of the 2 roles is bonded with different rights and obligations. Third, we show how to carry out the computation and storage at local and global. Finally, we discuss how our trust model allows peer to revoke relationships with distrusted peers. We present a concrete method to validate the proposed trust model and report sets of simulation-based experiments, showing the feasibility and robustness of this model.
HASN is a hierarchical routing protocol for heterogeneous sensor networks, optimized via cross-layer designs to save sensor's power and improve reliability. There are two kinds of nodes in heterogeneous sensor networks: normal sensor and header node that has more powerful battery and higher performance antenna. A header and sensors in its radio transmitting range compose a cluster. The header takes charge of data collection and data aggregation in its cluster. In a cluster, the communication is unsymmetrical. From the header to sensors is directly reachable, but from sensors to their header needs multi-hop. In this paper, a new dynamic address assignment method is introduced for large number of sensors automatically. A mathematics model of energy optimum relay tree is designed, which can guarantee the minimum energy cost forwarding and relay load balance. We give an approximation algorithm to resolve the model. A centralized scheduling management is proposed to avoid collisions completely in a cluster. We also introduce a mechanism to depress data redundancy.
In existing peer-to-peer database framework designs, coordination rules are assumed already present and never changed
during the whole course of operation. This paper investigates how coordination rules are created and changed, hence
helping ease the procedure. Local database can be on and off dynamically, but this feature of P2P database is
inconsistent with fixed coordination rules, for dependency path will be broken when an intermediate peer is absent. A
restoration mechanism is designed in this scenario to realize dynamic coordination rule. To achieve this, coordination
rules on the same dependency path have to be available after the path is broken, and combined together to form a new
dependency path and bypass the absent peer. To backup rules before host is down they can be published as resource
advertisement to remote peers by underlying P2P platform facility. Actually since coordination rules are no longer
bounded with their host, they can be viewed independent from the database system to form a coordination rule P2P
network, with some peers having no database and purely as rule cache. The protocols about rule cache, combination and
new rule creation request in such network are discussed. Rules float along dependency paths across network and
combine to form a new rule where necessary. A peer wanting to create new coordination rules can publish query and if
there is a rule on another peer which can be combined with the existing one, a new rule is created and send back. This
dependency path discovery process can be similar to route discovery process.