This paper proposes using mobile agents to manage application logs for recovery in mobile wireless environments. Mobile agents can reduce communication overhead and minimize recovery time by carrying both code and application state between nodes. The paper presents a reference architecture for a mobile database system with mobile units, base stations, and database servers. When handoffs occur between base stations, mobile agents work to transfer application logs for recovery. Two schemes are proposed - a forward log unification scheme to periodically unify logs across base stations, and a forward notification scheme to reduce recovery time by informing other base stations when failures occur. The use of mobile agents allows for more efficient application recovery in mobile wireless systems.
Transparent Caching of Virtual Stubs for Improved Performance in Ubiquitous E...ijujournal
Context-awareness is an essential requirement for pervasive computing applications, which enables them to adapt and perform tasks based on context. One of the adaptive features of context-awareness is contextual reconfiguration. Contextual reconfiguration involves discovering remote service(s) based on
context and binding them to the application components to realize new behaviors, which may be needed to satisfy user needs or to enrich user experience. One of the steps in the reconfiguration process involves a remote lookup to discover the service(s) based on context. This remote lookup process provides the largest contribution to reconfiguration time and this is due to fact that the remote calls are much slower than local
calls. Consequently, it affects system performance. In pervasive computing applications, this may turn out to be undesirable in terms of user experience. Moreover, other distributed applications using the network may be affected as every remote method call decreases the amount of bandwidth available on the network. Various systems provide reconfiguration support and offer high-level reconfiguration directives to develop
adaptive context-aware applications, but do not address this performance bottleneck. We address this issue
and implement seamless caching of virtual stubs within our PCRA1 for improved performance. In this paper we present and describe our transparent caching support and also provide its performance evaluation.
New Fault Tolerance Approach using Antecedence Graphs in Multi Agent SystemsIDES Editor
Mobile agents are distributed programs which can
move autonomously in a network, to perform tasks on behalf
of user. They are susceptible to failures due to faults in
communication channels, processors or malicious programs.
In order to gain solid foundation at the heart of today’s esociety,
the mobile agent technology must address the issue of
fault tolerance. Checkpointing has been widely used technique
for providing fault tolerance in mobile agent systems. But the
traditional message passing based checkpointing and rollback
algorithms suffer from problems of excess bandwidth
consumption and large overheads. This paper proposes use of
antecedence graphs and message logs for maintaining fault
tolerance information of agents. For checkpointing, dependent
agents are marked out using antecedence graphs; and only
these agents are involved in process of taking checkpoints. In
case of failures, the antecedence graphs and message logs are
regenerated for recovery and then normal operation
continued. The proposed scheme reports less overheads,
speedy execution and reduced recovery times as compared to
existing graph based schemes.
The advancement in mobile technology and wireless network increase the using of mobile device in database
driven application, these application require high reliability and availability due to nature inheritance of
mobile environment, transaction is the center component in database systems, In this paper we present
useful work done in mobile transaction, we show the mobile database environment and overview a lot of
proposed model of mobile transaction and show many techniques used to enhance transaction execution.
Transparent Caching of Virtual Stubs for Improved Performance in Ubiquitous E...ijujournal
Context-awareness is an essential requirement for pervasive computing applications, which enables them to adapt and perform tasks based on context. One of the adaptive features of context-awareness is contextual reconfiguration. Contextual reconfiguration involves discovering remote service(s) based on
context and binding them to the application components to realize new behaviors, which may be needed to satisfy user needs or to enrich user experience. One of the steps in the reconfiguration process involves a remote lookup to discover the service(s) based on context. This remote lookup process provides the largest contribution to reconfiguration time and this is due to fact that the remote calls are much slower than local
calls. Consequently, it affects system performance. In pervasive computing applications, this may turn out to be undesirable in terms of user experience. Moreover, other distributed applications using the network may be affected as every remote method call decreases the amount of bandwidth available on the network. Various systems provide reconfiguration support and offer high-level reconfiguration directives to develop
adaptive context-aware applications, but do not address this performance bottleneck. We address this issue
and implement seamless caching of virtual stubs within our PCRA1 for improved performance. In this paper we present and describe our transparent caching support and also provide its performance evaluation.
New Fault Tolerance Approach using Antecedence Graphs in Multi Agent SystemsIDES Editor
Mobile agents are distributed programs which can
move autonomously in a network, to perform tasks on behalf
of user. They are susceptible to failures due to faults in
communication channels, processors or malicious programs.
In order to gain solid foundation at the heart of today’s esociety,
the mobile agent technology must address the issue of
fault tolerance. Checkpointing has been widely used technique
for providing fault tolerance in mobile agent systems. But the
traditional message passing based checkpointing and rollback
algorithms suffer from problems of excess bandwidth
consumption and large overheads. This paper proposes use of
antecedence graphs and message logs for maintaining fault
tolerance information of agents. For checkpointing, dependent
agents are marked out using antecedence graphs; and only
these agents are involved in process of taking checkpoints. In
case of failures, the antecedence graphs and message logs are
regenerated for recovery and then normal operation
continued. The proposed scheme reports less overheads,
speedy execution and reduced recovery times as compared to
existing graph based schemes.
The advancement in mobile technology and wireless network increase the using of mobile device in database
driven application, these application require high reliability and availability due to nature inheritance of
mobile environment, transaction is the center component in database systems, In this paper we present
useful work done in mobile transaction, we show the mobile database environment and overview a lot of
proposed model of mobile transaction and show many techniques used to enhance transaction execution.
A COMPREHENSIVE STUDY AND PERFORMANCE COMPARISON OF M-ARY MODULATION SCHEMES ...IJCSEA Journal
Wireless communications has become one of the fastest growing areas in our modern life and creates enormous impact on nearly every feature of our daily life. In this paper, the performance of M-ary modulations schemes (MPSK, MQAM, MFSK) based wireless communication system on audio signal transmission over Additive Gaussian Noise (AWGN) channel are analyzed in terms of bit error probability as a function of SNR. Based on the results obtained in the present study, MPSK and MQAM are showing better performance for lower modulation order whereas these are inferior with higher M. The BER value is smaller in MFSK for higher M, but it is worse due to the distortion in the reproduce signal at the receiver end. The lossless reproduction of recorded voice signal can be achieved at the receiver end with a lower modulation order.
Domain partitioned element management systems employing mobile agents for dis...IJCNCJournal
Network management systems based on mobile agents a
re efficiently a better alternative than typical
client/server based architectures. Centralized mana
gement models like SNMP or CMIP based management
models suffer from scalability and flexibility issu
es which are addressed to great extent by flat bed
or static
mid-level manager models based on mobile agents, ye
t the use of mobile agents to distribute and delega
te
management tasks for above stated agent-based manag
ement frameworks like initial flat bed models and
static mid-level managers cannot efficiently meet t
he demands of current networks which are growing in
size and complexity. In view of the above mentioned
limitations, we proposed a domain partitioned netw
ork
management model based-on mobile agent & Element Ma
nagement Systems in order to minimize
management data flow to a centralized server. Intel
ligent agent allocated to specific EMS performs loc
al
network management and reports the results to the s
uperior manager and finally the global manager
performs global network management using those subm
itted management results. Experimental results of
various scenarios of the proposed model have been p
resented to support the arguments given in favor of
the
prototype system based on mobile agents.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
A bandwidth allocation model provisioning framework with autonomic characteri...IJCNCJournal
The Bandwidth Allocation Models (MAM, RDM, G-RDM and AllocTC-Sharing) are management
alternatives currently available which propose different resource (bandwidth) allocation strategies in
multiservice networks. The BAM adoption by a network is typically a management choice and
configuration task executed by the network operations and management system setup in a static or nearly
static way. This paper proposes and explores the alternative of allowing BAM definition and configuration
on a more dynamic way. In effect, one of the basic motivations towards BAM dynamic allocation is the fact
that multiservice networks characteristics (traffic load) may change considerably in daily network
operation and, as such, some dynamics in BAM allocation should be introduced in order to improve
performance. A framework is presented supporting BAM dynamic allocation. The framework adopts an
OpenFlow-based software-defined networking (SDN) implementation approach in order to support
scalability issues with a centralized controller and management network view. The framework architecture
also supports the implementation of some autonomic characteristics which, in brief, look for improving and
facilitating the decision-making process involved with BAM provisioning in a multiservice network. A
proof of concept is presented evaluating different BAM performance under different traffic loads in order to
demonstrate the framework strategy adopted.
A Quality of Service Strategy to Optimize Bandwidth Utilization in Mobile Net...IDES Editor
The mobile network that supports network mobility
is an emerging technology. It is also referred as NEMO
(NEtwork MObility). It is more appropriate for mobile
platforms such as car, bus, train, air plane, etc. It is a great
challenge to provide Quality of Service (QoS) in NEMO. QoS
is a set of service requirements to be met by the network.
There are various parameters by which QoS is provided. This
paper concentrates on providing optimum bandwidth for data
traffic. The objective of this paper is to propose a strategy to
use Virtual Circuit (VC) approach in NEMO. It helps to
utilize the bandwidth effectively, to consume minimum time to
transfer the data and also to reduce overload of the mobile
router due to the minimum size of the header. Ultimately, it
gives better results to enhance the QoS in mobile networks.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Performance of the MIMO-MC-CDMA System with MMSE EqualizationTamilarasan N
Multipath fading and spectral crowding are the
major challenges in dealing higher data rate in future
broadband wireless communication system. Multi-carrier
Modulation like Multicarrier code division multiple access
(MC-CDMA) can tackle the problem and provide higher data
rate for future wireless communication system. However,
through a frequency selective fading channel, the subcarriers
in MC-CDMA signal have different amplitude levels and phase
shifts which result in loss of the orthogonality among users
and generates Multiple access interference (MAI). To combat
the MAI, various amplitude and phase equalizing techniques
such as Maximum Ratio Combining (MRC), Equal Gain
Combining (EGC), Orthogonal Restoring Combining (ORC),
Threshold Orthogonal Restoring Combining or Minimum
Mean Square Error (MMSE) may be used. Out of these MMSE
offers better performance since the MMSE criterion is applied
independently on each subcarrier. Further improvement in
performance is possible through space–time block coding,
which offers maximum diversity gain and multiplexing gain.
This paper combines MC-CDMA with MMSE equalization
and space–time block coding which proves to be a powerful
physical layer solution in combating delay spread and inter
symbol interference (ISI).
A COMPREHENSIVE STUDY AND PERFORMANCE COMPARISON OF M-ARY MODULATION SCHEMES ...IJCSEA Journal
Wireless communications has become one of the fastest growing areas in our modern life and creates enormous impact on nearly every feature of our daily life. In this paper, the performance of M-ary modulations schemes (MPSK, MQAM, MFSK) based wireless communication system on audio signal transmission over Additive Gaussian Noise (AWGN) channel are analyzed in terms of bit error probability as a function of SNR. Based on the results obtained in the present study, MPSK and MQAM are showing better performance for lower modulation order whereas these are inferior with higher M. The BER value is smaller in MFSK for higher M, but it is worse due to the distortion in the reproduce signal at the receiver end. The lossless reproduction of recorded voice signal can be achieved at the receiver end with a lower modulation order.
Domain partitioned element management systems employing mobile agents for dis...IJCNCJournal
Network management systems based on mobile agents a
re efficiently a better alternative than typical
client/server based architectures. Centralized mana
gement models like SNMP or CMIP based management
models suffer from scalability and flexibility issu
es which are addressed to great extent by flat bed
or static
mid-level manager models based on mobile agents, ye
t the use of mobile agents to distribute and delega
te
management tasks for above stated agent-based manag
ement frameworks like initial flat bed models and
static mid-level managers cannot efficiently meet t
he demands of current networks which are growing in
size and complexity. In view of the above mentioned
limitations, we proposed a domain partitioned netw
ork
management model based-on mobile agent & Element Ma
nagement Systems in order to minimize
management data flow to a centralized server. Intel
ligent agent allocated to specific EMS performs loc
al
network management and reports the results to the s
uperior manager and finally the global manager
performs global network management using those subm
itted management results. Experimental results of
various scenarios of the proposed model have been p
resented to support the arguments given in favor of
the
prototype system based on mobile agents.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
A bandwidth allocation model provisioning framework with autonomic characteri...IJCNCJournal
The Bandwidth Allocation Models (MAM, RDM, G-RDM and AllocTC-Sharing) are management
alternatives currently available which propose different resource (bandwidth) allocation strategies in
multiservice networks. The BAM adoption by a network is typically a management choice and
configuration task executed by the network operations and management system setup in a static or nearly
static way. This paper proposes and explores the alternative of allowing BAM definition and configuration
on a more dynamic way. In effect, one of the basic motivations towards BAM dynamic allocation is the fact
that multiservice networks characteristics (traffic load) may change considerably in daily network
operation and, as such, some dynamics in BAM allocation should be introduced in order to improve
performance. A framework is presented supporting BAM dynamic allocation. The framework adopts an
OpenFlow-based software-defined networking (SDN) implementation approach in order to support
scalability issues with a centralized controller and management network view. The framework architecture
also supports the implementation of some autonomic characteristics which, in brief, look for improving and
facilitating the decision-making process involved with BAM provisioning in a multiservice network. A
proof of concept is presented evaluating different BAM performance under different traffic loads in order to
demonstrate the framework strategy adopted.
A Quality of Service Strategy to Optimize Bandwidth Utilization in Mobile Net...IDES Editor
The mobile network that supports network mobility
is an emerging technology. It is also referred as NEMO
(NEtwork MObility). It is more appropriate for mobile
platforms such as car, bus, train, air plane, etc. It is a great
challenge to provide Quality of Service (QoS) in NEMO. QoS
is a set of service requirements to be met by the network.
There are various parameters by which QoS is provided. This
paper concentrates on providing optimum bandwidth for data
traffic. The objective of this paper is to propose a strategy to
use Virtual Circuit (VC) approach in NEMO. It helps to
utilize the bandwidth effectively, to consume minimum time to
transfer the data and also to reduce overload of the mobile
router due to the minimum size of the header. Ultimately, it
gives better results to enhance the QoS in mobile networks.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Performance of the MIMO-MC-CDMA System with MMSE EqualizationTamilarasan N
Multipath fading and spectral crowding are the
major challenges in dealing higher data rate in future
broadband wireless communication system. Multi-carrier
Modulation like Multicarrier code division multiple access
(MC-CDMA) can tackle the problem and provide higher data
rate for future wireless communication system. However,
through a frequency selective fading channel, the subcarriers
in MC-CDMA signal have different amplitude levels and phase
shifts which result in loss of the orthogonality among users
and generates Multiple access interference (MAI). To combat
the MAI, various amplitude and phase equalizing techniques
such as Maximum Ratio Combining (MRC), Equal Gain
Combining (EGC), Orthogonal Restoring Combining (ORC),
Threshold Orthogonal Restoring Combining or Minimum
Mean Square Error (MMSE) may be used. Out of these MMSE
offers better performance since the MMSE criterion is applied
independently on each subcarrier. Further improvement in
performance is possible through space–time block coding,
which offers maximum diversity gain and multiplexing gain.
This paper combines MC-CDMA with MMSE equalization
and space–time block coding which proves to be a powerful
physical layer solution in combating delay spread and inter
symbol interference (ISI).
AN ACCOMPLISHED MINIMUM-OPERATION DEPENDABLE RECOVERY LINE COMPILATION SCHEME...IAEME Publication
While dealing with mobile distributed frameworks, we come across some issues like: mobility, low bandwidth of wireless channels and lack of stable storage on mobile nodes, disconnections, limited battery power and high failure rate of mobile nodes. These issues make traditional Dependable Recovery Line Compilation (DRLcompilation) techniques designed for Distributed frameworks unsuitable for Mobile environments. In this paper, we design a minimum operation algorithm for Mobile Distributed frameworks, where no useless retrieval-marks are taken and an effort has been made to optimize the filibustering of operations. We propose to delay the processing of selective reckoning-communications at the receiver end only during the DRL-compilation period. A Process is allowed to perform its normal reckonings and send reckoning-communications during its filibustering period. In this way, we try to keep filibustering of operations to bare minimum. In order to keep the filibustering time minimum, we collect the dependency vectors and compute the exact minimum set in the beginning of the algorithm. The number of operations that take retrieval-marks is minimized to 1) avoid awakening of Mob_Nodes in doze mode of operation, 2) minimize thrashing of Mob_Nodes with DRL-compilation activity, 3) save limited battery life of Mob_Nodes and low bandwidth of wireless channels. In coordinated DRL-compilation, if a single operation fails to take its retrieval-mark; all the DRL-compilation effort goes waste, because, each operation has to abort its partially-committed retrieval-mark. In order to take its partially-committed retrieval-mark, an Mob_Node needs to transfer large retrieval-mark data to its local Mob_Supp_St over wireless channels. The DRLcompilation effort may be exceedingly high due to frequent aborts especially in mobile frameworks. We try to minimize the loss of DRL-compilation effort when any operation fails to take its retrieval-mark in coordination with others.
Performance evaluation of transaction processing in mobile data base systemsijdms
Specific characteristics of mobile environments make traditional transaction management techniques no
longer appropriate. This is due the fact that the ACID properties of transactions are not simply followed, in
particular the consistency property. Thus, transaction management models adopting weaker form of
consistency are needed and these models can now tolerate a limited amount of consistency. In this paper
we evaluate our execution framework on different mobile computation modes using different execution
strategies. Moreover, the effects of the fixed host transaction are identified and included in the evaluation
The integration between wired and wireless environments confirms that the execution strategy is critical for
the performance of a system. Neither MHS nor FHS are optimal in all situations and the performance
penalties and wasted wireless resources can be substantial. A combined strategy CHS over MCA-FSA
computation model matches the best performance of the FHS and MHS and shows better performance than
both in many cases.
A Survey of Cyber foraging systems: Open Issues, Research ChallengesEswar Publications
This paper presents a survey on current applications which practice the pervasive mechanism of cyber foraging. The applications include the LOCUSTS framework, Slingshot, Pupetter. This applications advocated the operating principle of task sharing among resource deficient mobile devices. These applications face some design issues for providing efficient performance like task distribution and task migration apart from the security aspect. The general operating mechanism of the cyber foraging technique are also discussed upon and the design options to leverage the throughput of the inherent mechanism is also represented in a suitable way.
starts with an introduction to mobile cloud computing with a definition, architecture, and advantages/disadvantages. At the next sections, continues with the applications of MCC, detailed challenges in mobile environment and solutions. Lastly the document concludes the main issues about the mobile cloud computing with the conclusion part.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
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Implementing database lookup method in mobile wimax for location management a...ijdpsjournal
The mobile WiMAX plays a vital role in accessing the delay sensitive audio, video streaming and mobi
le
IPTV. To minimize the handover delay, a Location
Management Area (LMA) based Multicast and
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e MBS
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IJCER (www.ijceronline.com) International Journal of computational Engineerin...ijceronline
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Similar to A STUDY OF RECOVERY OF APPLICATION IN MOBILE WIRELESS ENVIRONMENT USING MOBILE AGENTS.doc (20)
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A STUDY OF RECOVERY OF APPLICATION IN MOBILE WIRELESS ENVIRONMENT USING MOBILE AGENTS.doc
1. A STUDY OF RECOVERY OF APPLICATION IN MOBILE
WIRELESS ENVIRONMENT USING MOBILE AGENTS
Miss.T.Priya1, Mrs.R.Renuka M.E.2
1. II year M.E. (computer science and Engineering)
{tpriya_vlb@rediffmail.com, haripriya_vlb@yahoomail.com}
2. Lecturer, Department of CSE, KSRCT
Abstract-The geographical mobility of the mobile devices makes the application recovery
complex which needs to store application log for the recovery of the application.
This paper focuses the application log management using the mobile agents.
Index Terms-MDS, mobile agents, PCS, coordinators, log unification, application recovery
1 INTRODUCTION
Wireless communication through PCS transaction to nodes, transaction
execution, and updation of results from
(Personal Communication Systems) or
clients to server. The recovery recreates
GSM (Global System for mobile
the module to the prior failure execution
Communications) has become the
state of the application.
essentials of day-to-day life. Today all
Application recovery is complex than
telecommunication companies improve
the database recovery due to the
the communication quality, availability,
following reasons:
reliability, security to add the data
1. Presence of multiple application
management capabilities in the MDS
states
(Mobile Database Systems).MDS is a
2. Absence of last consistent state.
database system which reach the data
3. Large no of application required to
location and perform the processing and
manage database processing.
deliver the results since each mobile units
This becomes more complex in MDS
will have high work load so these MDS
due to
will be a useful resource to perform
1. Processing demands of mobile units.
transactions.
2. Existence of random handoffs.
To perform the system-level functions
3. Presence of operations connected,
MDS may require different transaction
disconnected, intermittent connected
management techniques (concurrency
modes.
control, database recovery, query
In this logging scheme we store,
processing), different caching schemes
retrieve, unify fragments of application
etc.
log for recovery with in the constraints of
Application recovery includes number
the MDS.
activities like transaction arrival,
fragmentation and distribution of
2. 2 REFERENCE ARCHITECTURE OF Fig. 1 shows the reference architecture of
MOBILE DATABASE SYSTEM AND MDS which is based on PCS or GSM.
TRANSACTION EXECUTION
Fig. 1 shows the reference architecture of The mobile transaction model is
MDS which is based on PCS or GSM. referred to as “mobilaction”. Mobil
action is defined as Ti= {e1, e2.., en}
where a transaction Ti is requested at MU
is called as H-MU (home MU) and is
fragmented and are execute at MU. In the
When the H-MU suffers handoff means
the CO also changes this increases the
time to commit. So the CO module can
be housed either in BS, MU, DBS, and
MSC. But selection of MU is not a good
choice due to the following limitations:
1. Limited storage.
2. Limited power supply.
3. Unpredictable handoffs.
4. Limited availability.
3 RECOVERY PROBLEM
SPECIFICATION
MDS recovery is complex due to the
following reasons:
1. MU’s stability: The MU may
Fig. 1 Reference architecture of MDS encounter some of the following
failures limited battery power, run
A set of general purpose computers are out of disk space, user physically
categorized as fixed hosts and BS (Base drop the MU. So any of these
Station).one or more BS are connected to events may affect the MU
the BSC (Base Station Controller).BSC functionality and recovery
coordinates operations commanded by algorithm must take all these in to
the MSC (Mobile Switching Center). consideration.
The size of the cell depends on the 2. Limited wireless bandwidth:
power of the BS and also the bandwidth During the recovery MU have to
of wireless communication channels.. A communicate with the BS or with
DBS provides full database services it other MU so in that time if there are
communicates with MU through the BS no free channels it affects the
and it is installed in either BS or FH.A communication quality.
MU cannot provide a reliable storage so 3. Random Handoff: This affects the
for recovery it relies on either BS or FH. recovery since the location of the
But to support these activities BS has to MU is not available immediately
be entirely modified so we create DBS as for the communication.
separate nodes in wired network that 3.1 Application Log Management
could be reached by any BS at any time. An efficient recovery scheme should
consume minimized resources and
3. recreate the execution environment as have registered with it. When the
soon as possible after MU reboots. agents are started they read the
Messages that change the contents of log information created and act
the log are called write events. The H- accordingly.
MU records the events like • Base Agent (BaAg): This agent
1. The arrival of Ti decides which logging scheme to
2. Fragmentation of Ti be used for the current
3. Assignment of CO to a Ti environment. The BA creates an
4. Mobility history of H-MU. instance of an agent to handle
5. Dispatch of the updates to the DBS. recovery of mobilactions for each
The objective of using mobile agents MU.
with the MDS is to • Home Agent (HoAg): This agent
1. Reduce communication overhead. handles Mobilactions for each H-
2. Recovery time should be minimal. MU. It is responsible for
3. Easy implementation of recovery maintaining log and recovery of
schemes. H-MU.
4 A MOBILE AGENT-BASED LOG • Coordinator Agent (CoAg):
MANAGEMENT SCHEME This is a coordinator residing in
A Mobile agent is an autonomous BS.
program that suspend the execution at • Event Agent (EvAg): There are
any point and resume execution from various events taking place like
where is stopped in the new machine. An registration of a MU, failure of
agent carries both code and the MU, handoff of MU etc. When
application state. Some of the advantages any MU suffers from handoff it
of the mobile agents are: can be known by the HoAg
1. Protocol Encapsulation: Mobile through this EvAg only to take
agents contain own protocols in their necessary action.
code itself. • Driver Agent (DrAg): During
2. Robustness and Fault Tolerance: the migration of the mobile agents
When failures are detected host we need to transfer the code and
system can easily dispatch the agents actual data this increases the
to the other hosts for the recovery. overhead to manage this we use
3. Asynchronous and Autonomous driver agent (DrAg).
Execution: Once agents are 4.1 Action of Agents When Handoff
dispatched they can make the Occurs
decisions independently. The HoAg moves along with the MU to the
These agents do have disadvantages new BS instead of sending all its code we
where high migration leads to machine send driver agent when handoff occurs. The
overhead. So this must be minimized. DrAg checks whether the code for the HoAg
In this architecture we have the following is present in new BS or not .If code is present
agents and their logical functions: it requests the BaAg in new BS to create an
instance of HoAg for this MU. If it is not
• Bootstrap Agent (BsAg): This
present DrAg sends request to previous BS’s
agent addresses a BS failure. BaAg to take clone of HoAg and send the
When a BS fails it registers in copy to the new BS to continue its operation.
bootstrap agent. Once loaded this
agent starts all the agents that
4. When MU moves out the BS its unification of the log. This is called as
information are not deleted automatically Estimated Log Unification Time (ELUT)
until it is notified by the agents of the MU. Max{BSi-LogSize/network link
speed+propagation Delay}
5 FORWARD STRATEGY It also depends on the factors like
The time duration between the MU whether BS is located in the same or
failing and rebooting is called as different VLR.
Expected Failure Time (EFT). When a 5.2 Forward Notification Scheme
MU suffers from a handoff the This calculates the time spent in getting
communication with the last BS is BS information from the HLR. Each
disconnected only after the connection VLR stores MU’s status information
with the new BS so this allows the MDS (normal, failed, forwarded).when a MU
to detect the failure of the MU. MU is fails the BS informs the VLR.VLR
monitored by the BS and any change in changes the status of the MU in database
the situation of the MU is registered in from normal to failed. The VLR sends
EvAg this makes the EFT value the information to all adjacent VLR they
appropriate. When the new BS does not store the message until they receive the
know the location of old Bs it is obtained denotify messages.
from the HLR. If the HLR is far away it Case 1: The MU reboots in the same BS
is obtained from the VLR if both BS fall where it failed.
same under the control of VLR.If VLR issues denotify message to
different VLR then HLR should be all VLRs.
queried. If a MU crashes then the Case 2: The MU reboots in a different BS
recovery of different BS needs the new but in same VLR.
BS to wait until the log unification in the MU register in Bs and notified to
old BS finishes. VLR.
In this we provide two schemes to Case 3: The MU reboots in a different BS
and a Different VLR.
reduce the recovery time by unifying the
log information periodically when the The MU requests for the
number handoffs occurred crosses a registration then the VLR returns the
predefined handoff threshold .when a identity of the previous BS and the
handoff occurs the trace is transferred identity of the VLR to the HoAg of the
from old BS to new B. The trace contains MU in recovered BS. The BS perform
BS_ID of the new BS and log size. The log unification from the previous BS and
log size updated when MU presents a new VLR sends recovery message to
information. previous VLR and registration message
The another scheme is to store the EFT of the MU in the new location to the old
value in a variable when a MU fails it HLR. After receiving recovered message
intimates the agent framework through VLR sends denotify message to all
the event agent interface which starts adjacent VLRs except the MU recovered
EFT clock and stopped to get recovery and removes its registration.
time.
5.1 Forward Log Unification Scheme
When a MU fails the trace information 6 CONCLUSION
contains the log size stored in different In this paper we present the application
BS’s. The HoAg based on the log size it recovery using mobile agents. Forward
calculates the time needed for the
5. strategy reduces the recovery time with
consistent behavior in all parameters.
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6. A STUDY OF RECOVERY OF APPLICATION IN MOBILE
WIRELESS ENVIRONMENT USING MOBILE AGENTS
Paper Submitted By
T.Priya B.Tech
II year M.E. (Computer Science and Engineering)
K.S.Rangasamy College of Technology,
Tiruchengode,
TamilNadu
Guided By
Mrs.R.Renuka M.E.
Lecturer, KSRCT,
Tiruchengode,
TamilNadu