Power Management for Throughput Enhancement in Wireless Ad-Hoc
Networks using Clusters
Power Management for Throughput Enhancement in Wireless Ad-Hoc
Networks using Clusters
Abstract
Mobile Adhoc network is an autonomous network of mobile nodes
where the mobiles uses the services of other mobiles for routing
and packet transmission.
In this project we introduce the notion of power management
within the context of wireless ad-hoc networks. More specifically ,
we investigate the effects of using different transmit powers on
the average power consumption and end-to-end network throughput in
a wireless ad-hoc environment. This power management approach would
help in reducing the system power consumption and hence pro-longing
the battery life of mobile nodes. Furthermore, it improves the
end-to-end network throughput as compared to other ad-hoc networks
in which all mobile nodes use the same transmit power. Further the
work is extended to cluster based routing where the data is routed
through higher energy nodes called clusters with dynamic cluster
management.The improvement is due to the achievement of a tradeoff
between minimizing interference ranges, reduction in the average
number of hops to reach a destination, the probability of having
isolated clusters, and the average number of transmissions
(including retransmis-sions due to collisions). The protocols would
first dynamically determine an optimal connectivity range wherein
they adapt their transmit powers so as to only reach a subset of
the nodes in the network. The connectivity range would then be
dynamically changed in a distributed manner so as to achieve the
near optimal throughput. Minimal power routing is used to further
enhance performance. Simulation studies are carried out in order to
investigate these design approaches using Omnet++ event driven
simulator. It is seen a network with such a power managed scheme
would achieve a better throughput performance and lower transmit
power than a network without such a scheme.
Chapter 1: Preamble1.1 Statement of the Problem The fundamental
problem with Adhoc network are mainly twofold:1) No control over
the sessions due to decentralized topology2) No power control
technique due to non centralized architecture.Various techniques
are being proposed to solve the problem, mainly by using Backbone
routing, cluster based routing and so on. Various power control
algorithms are also implemented for enhancing the energy
utilization of the network. In this work we combine the power
control and cluster based routing features to derive a new routing
and transmission protocol for manet to improve the performance of
the system.1.2 Objective of the StudyVarious routing algorithms
have been proposed for wire-less ad-hoc networks in the literature.
Those algorithms are mainly focused on establishing routes, and
maintain-ing these routes under frequent and unpredictable
connectivity changes. The implicit assumption in most of the
earlier work is that nodes' transmitted powers are fix ed. To the
best of our knowledge, there is no prior known work that proposes
the concept of mobile ad-hoc nodes using different transmit powers.
It is evident that this approach is restricted to ad-hoc networks
of relatively low mobility patterns. If the nodes are highly
mobile, the power management algorithm might fail to cope with the
fast and sudden changes due to fading and interference
conditions.therefore the objective is to investigates the benefits,
and possibly the tradeoffs, of deploying different transmit powers
in the wireless ad-hoc environment. We propose a power management
scheme with cluster based topology control which can be used in
conjunction with traditional table-driven routing protocols, with
possibly minor modifications. The performance measures are taken to
be the end-to-end network throughput and the average power
consumption.1.3 Scope of the Study The work can be used as a
benchmark for practical Adhoc networks like office network which
forms clusters of mobile nodes with laptops as cluster heads or
domain controllers. The system can be used to enhance the lifetime
of the nodes by suitable power management. The system produces
better performance in terms of higher packet delivery ratio and
throughput. The load is distributed through cluster heads which are
essentially more energy efficient nodes. The system can also be
used for transmission of multimedia traffic or VBR traffic where
more stability is needed for the topology for data transmission.1.4
Introduction to Mobile Adhoc Network[Yourself]
1.5 Limitation of the Study Even though the system produces
better performance than conventional AODV based techniques, the
protocol applies higher load on cluster nodes. If the cluster nodes
are considered to be normal mobiles and not Laptops or other power
enabled nodes, then the system drains the node's energy thick and
fast. Further the power management process introduces higher
latency to the system.
Chapter 2
Related Work
[Yourself]
Chapter 3Power Management in MANETWhen the power management
scheme is implemented, each node transmits at a minimum power level
such that only a fix ed number of neighboring nodes can hear the
transmission. For example, a node might transmit with a power such
that only its three closest neighbors can hear its
transmission.Thus, in Figure 1 below, node A transmits with a power
P1 such that only it's three nearest neighbors i.e., nodes B, C and
D can hear it. Similarly, node D would transmit with a different
power, say P2 such that only it's three nearest neighbors i.e.,
nodes A, C and E can hear it.
In order to set up the framework to investigate the effect of
transmit powers on the end-to-end network throughput, we make the
following assumptions and introduce some appropriate notations:
1. The wireless ad-hoc network consists of n nodes; each node
has a unique ID, denoted by Node ID.
2. The mobile nodes are assumed to have low mobility patterns,
that is, they are typical pedestrians. This, in turn, implies that
the network topology changes slowly and the class of shortest-path
routing algorithms is applicable. 3. Each mobile node has direct
connectivity to its N clos-est neighbors only, where N is to be
adapted dynamically.
4. Assume connectionless (datagrams) type of traffic, i.e.
routing decisions are made on a packet-by-packet-basis.
The transmit power of any mobile node is upper bounded by a
maximum power level denoted as Pmax The limited size and weight of
the mobile terminal dictate this constraint.
The transmit power of any mobile node is lower bounded by a
minimum power level Pmin. This constraint is essential to avoid
partitioning the network into isolated islands. 1.1GeneralThe
section describes the procedures for the support of the
service-level interworking for the Short Message Service as defined
in [C.S0015] and Instant Messaging service as defined in
[OMASIMPLE]. NOTE:In the procedures in the following subclauses,
the ICSCF, PCSCF and ASs such as IM AS are not shown in the
figures.1.2SMS-GW IMS 3rd Party Registration call flowThis call
flow shall be according to the procedures described in
[X.S0048].1.3Interaction between transport-level and service-level
interworking with interworking in the originating
side1.3.1GeneralThe interaction between transport-level
interworking (between SMS over CS and SMS over IMS) and
service-level interworking (between Instant Messaging and SMS)
depends on the user subscription and authorisation, on the UE
capabilities, and on operator policy.If a user is only subscribed
to either transport-level interworking or service-level
interworking, only procedures defined for the subscribed
interworking type may be performed.If a user is subscribed to both
transport-level interworking and service-level interworking, but
the user is only authorized for one of the interworking types when
the message is processed, only the authorized interworking may be
performed.If a user is subscribed to both transport-level
interworking and service-level interworking, and the user is
authorized for both types, the behavior of the SMS-GW depends on
the specific scenario, on the registered capabilities of the UE,
and finally is defined by operator policy and user preferences.For
a user subscribed to service-level interworking, two Application
Servers in the network are normally called upon to handle an
Instant Message:-the IM AS, defined in [OMASIMPLE]; -the SMS-GW.The
following sections describe the different interaction
scenarios.1.3.2IMS OriginatingIn the originating network, a UE
sends a SIP MESSAGE (Encapsulated Short Message or Instant
Message). The originating SCSCF forwards the SIP MESSAGE to the
SMS-GW based on the iFC. If there is no subscription for the
interworking service, the SMS-GW is not included in the iFC and the
SCSCF continues with the subsequent iFC check. After all the
originating iFC triggers have been handled, the SCSCF attempts to
route the SIP MESSAGE to the terminating IMS network. If it fails,
an error is returned to the sender.NOTE1:If an IM AS is present in
the network, Instant Messages are routed to it before going to the
SMS-GW.NOTE2:An encapsulated Short Message uses the PSI of the
Message Center as the Request-URI. If the user is not subscribed to
transport-level interworking and the SMS-GW is not invoked, the
ENUM query fails, and an error is returned to the sender. How the
UE is provided with the PSI of the Message Center is outside the
scope of this document.When the SMS-GW receives the SIP MESSAGE, it
shall decide which interworking is performed based on the content
of the received SIP MESSAGE, as the SMS-GW can distinguish between
an encapsulated Short Message and an Instant Message. If an
encapsulated Short Message is received and if the subscriber is
authorized for the transport-level interworking, the SMS-GW maps
the encapsulated Short Message to a Short Message. Similarly, when
an Instant Message is received, the SMS-GW determines whether the
Instant Message is routable in IMS. If the Instant Message is not
routable in IMS and the service level interworking is authorized,
the SMS-GW shall perform the service-level interworking. Figure 1
Figure 6.3.2: Performing interworking service on originating
side1.3.3IMS TerminatingWhen the SMS-GW receives a Short Message
from the legacy network on the terminating side, it performs the
domain selection to determine the preferred domain to transfer the
Short Message. If the selected network is IMS, the SMS-GW will
determine whether the transport level interworking or the service
level interworking is to be preformed based on the users'
subscription and authorization, and on the UE capability as
indicated during IMS registration. If the user has subscribed to
both services, is authorized for both and the UE has indicated its
capability to receive both encapsulated Short Messages and Instant
Messages, the priority between the transport-level interworking and
the service-level interworking is based on operator policy and user
preferences.
NOTE:If the incoming Short Message is interworked to an Instant
Message, the resulting Instant Message could be routed to the IM AS
before being sent to the UE. Figure 2 Figure 6.3.3: Performing
interworking service on terminating side for an incoming Short
Message1.4IM capable UE sends an Instant Message to an SMS user
with interworking in the originating side Figure 3 Figure 6.4:
Successful IM origination to SMS procedure1)The UE registers to
S-CSCF according the IMS registration procedure.2)UE submits the
Instant Message to the S-CSCF using an appropriate SIP method. The
UE may request to hide its Public User Identity from the recipient
within the Instant Message, as described in [OMASIMPLE].3)S-CSCF
forwards the Instant Message toSMS-GW based on stored iFC.NOTE
1:Subscribers with no subscription for service level interworking
will not be provided with the relevant iFCs.4)The SMS-GW shall
decide whether to perform service-level interworking depending on
SIP request header field (e.g. Request-URI), operator policy, when
the Instant Message is not routable in the IMS. If the
service-level interworking is authorized, the originating UE's
SMS-GW delivers the SMS message to the terminating SMS-GW in a MAP
SMDPP message. The terminating SMS-GW is not shown for brevity.
5)The terminating SMS-GW responds by sending a MAP smdpp message
back to the sender of the MAP SMDPP message. 6)If service
authorization is successful, the SMS-GW acknowledges the Instant
Message.7)Instant Message acknowledgement is forwarded by S-CSCF to
UE.NOTE2:Steps 6 and 7 can occur anytime after the subscriber
authorization check has been performed by the SMSGW.8)The
terminating SMS-GW acknowledges message delivery to the MS by
sending MAP: SMDPP (Delivery Report).9)The originating SMS-GW
responds by sending a MAP smdpp message back to the sender of the
MAP SMDPP message. 10)SMS-GW translates the received Delivery
report to an appropriate Instant Message, and forwards it to the
SCSCF. If the SMSGW sent concatenated Short Messages to terminating
SMS-GW in step4, the SMSGW should wait for the last Delivery
Report, and translate the last Delivery Report to an appropriate
Instant Message, and forward it to the SCSCF.11)S-CSCF sends the
translated Instant Message to the UE.12)UE acknowledges the
translated Instant Message.13)Acknowledgement of the translated
Instant Message is forwarded by S-CSCF to SMS-GW.1.5IM capable UE
sends an Instant Message to an SMS user with interworking in the
terminating sideThis procedure describes the delivery of an Instant
Message to a registered IMS subscriber that is presently being
served by a 1xRTT network. Figure 4 Figure 6.5: Successful IM
terminating to SMS procedure with interworking in the Terminating
Side1)UE submits an Instant Message, destined to another IM user in
another IMS domain, using an appropriate SIP method. The UE may
request to hide its Public User Identity from the recipient within
the Instant Message, as described in [OMASIMPLE].2)The S-CSCF
resolves the destination domain and routes the message towards the
S-CSCF in the terminating network ("Terminating S-CSCF").3)The
terminating S-CSCF forwards the Instant Message to the IM AS
("Terminating IM AS") based on stored iFC.NOTE:Depending on iFC
configuration, it is possible that the IM AS is not triggered for
the unregistered subscribers.4)The terminating IM AS invokes
terminating IM services as applicable for the destination IM user.
5)The IM AS can forward the Instant Message back to the terminating
S-CSCF, e.g. when the terminating IM user is offline.6)The
terminating S-CSCF forwards the Instant Message to the SMS-GW, e.g.
based on stored iFC.7-11)The SMS-GW sends Accepted towards the IM
capable UE to indicate that the Instant Message has been accepted
for further processing.12)The SMS-GW performs service level
interworking of the received instant message (step 11). After the
service level interworking, the SMS-GW sends a MAP SMDPP Invoke
message to the Serving MSC and starts timer SMT. The MAP SMDPP
Invoke message containing the SMS Delivery message [C.S0015] in the
SMS_BearData Parameter.13)The MSC sends an ADDS Page message
[A.S0014] to the BS. The ADDS Page message contains the SMS
Delivery message in the ADDS User Part information element.If the
MSC requires an acknowledgment, it includes the Tag information
element in the ADDS Page message and starts timer T3113.14)The BS
sends the SMS Delivery Message to the MS on the Paging Channel or
the Forward Common Control Channel. Before sending the short
message, the BS may perform vendor specific procedures such as
paging the MS to determine the cell in which the MS is
located.15)If a Layer 2 Ack was solicited in the Data Burst Message
(Step 14), the MS acknowledges the receipt of the message by a
Layer 2 Ack.16)If the MSC requested an acknowledgment by including
the Tag information element in the ADDS Page message (step 13), the
BS replies with an ADDS Page Ack message including the Tag
information element set identical to the value sent by the MSC
(step 13). If timer T3113 was previously started, it is now
stopped.17)The MSC acknowledges the MAP SMDPP invoke message (step
12) by sends a SMDPP return result to the SMS-GW. Upon receiving
the MAP SMDPP return result message the SMS-GW stops timer
SMT.18)If a Reply Option subparameter received in an SMS Deliver
Message (step 14) indicates that User Acknowledgment is requested,
the mobile station should indicate the request to the user. When
the user acknowledges the message, the mobile station sends an SMS
User Acknowledgement Message in response to the SMS Deliver
Message.19)If a Layer 2 Ack was solicited in the Data Burst Message
(Step 18), the BS acknowledges the receipt of the message by a
Layer 2 Ack.20)The BS sends the MSC an ADDS Transfer message. The
ADDS Transfer message contains the SMS User Acknowledgment Message
in its ADDS User Part information element.21)The MSC sends the
SMS-GW a MAP SMDPP Invoke message and starts timer SMT. The MAP
SMDPP Invoke message contains the SMS User Acknowledgment Message
in the SMS_BearData Parameter.22)The SMS-GW acknowledges the MAP
SMDPP invoke message (step 21) by sending an SMDPP return result to
the MSC. Upon receiving the MAP SMDPP return result message the MSC
stops timer SMT.23)SMS-GW translates the received SMS User
Acknowledgment Message to an appropriate Instant Message, and
forwards it to the terminating SCSCF.24-27) The terminating S-CSCF
sends that Instant Message containing the delivery status of the
message towards the IM capable UE.28-32) The IM capable UE sends OK
response the SMS-GW.1.6IM user receives Short Message from an SMS
userAn IMS registered user with SIMPLE IM service receives a Short
Message formatted via service-level interworking to an Instant
Message. We deploy the classical shortest-path routing algorithm
with a slight modification where routing is performed through
cluster heads. The cluster heads are selected absed on the degree
of neighborhood and energy consideration. The link costs are chosen
to be the transmitted powers. Therefore, the objective is to route
the packet from the source to the destination through the minimum
power path.
12.The received power at any mobile node has to be greater than
a minimum power level, denoted by Min-RecvPower. This is crucial in
order to guarantee reliable communication between the transmitter
and the receiver. This value helps determine the power level at
which a mo-bile has to transmit in order to directly reach a
neighboring node.
13.It is expected that unidirectional links will be formed when
transmit powers are thus manipulated, i.e. we might have a cluster
of nodes that can communicate with each other but no packets can
either enter or leave this cluster. Modifications to the the
protocol to eliminate this effect
are being investigated. However, it should be noted that this
does not change the routing methodology1 since the signaling
channel is bidirectional. 14.The Signaling Packet format is shown
in Figure 2 below,
Node IDNeighbor IDTransmit Power Level Figure 2: Signaling
Packet Format
where,
Node ID: Identifier for the node broadcasting the signaling
packet.
Neighbor ID: Identifier for a direct neighbor to which the node
is broadcasting the signaling packet.
Transmit Power Level: Minimum power level needed to reach that
neighbor.
15. The Data Packet format is shown in Figure 3.
Source IDDestination IDCurrent Node ID Next Node
IDRe-TransmissionsPayload
Figure 3: Data Packet Format
where,
Source ID: Identifier of the node that generated the packet.
Destination ID: Identifier of the packet's destination node.
Current Node ID: Identifier of the relay node at which the packet
is currently stored on its path to the destination.
Next Node ID: Identifier of the next relay node to which the
packet is to be transmitted on its path to the destina-tion.
Re-Transmissions: Total number of retransmission at-tempts
performed on that packet. (retransmission will be17. Node
Throughput is defined as percentage of success-ful transmission
attempts.
End-to-End Network Throughput is defined as per-centage of
packets that reach their destinations success-fully
The power model is given by
where Pr is the received power, and Pt is the transmission power
and is the interference ratio.The Minimum Power Routing (MPR)
algorithm proposedis a hop-by-hop shortest path routing mechanism
where the link costs are the transmitted power levels.The routing
algorithm then goes through the followingsteps:1. Based on the
routing table constructed, the mobile nodecreates the set of all
possible routes from the source to destination.2. The routing
algorithm employed falls within the general class of shortest path
routing. It searches, within the created route set, for the minimum
cost route from sourceto destination.3. Determine the next relay
node on the minimum power route.
4. Modify the Next Node ID field in the data packet being
routed.
5. Copy the packet to the retransmission buffer until its
successful reception at the next node is indicated via an ACK
message.
6. The packet is sent to the MAC module for transmission to the
next relay node.
Connectivity ProblemConsidering various conditions of
connectivity and power management, it is straightforward to point
out the follow-ing issues:Consider a wireless ad-hoc network with
all mobile nodes using the maximum power level (i.e. no power
man-agement). Accordingly, any mobile node can reach a large number
of nodes in just one hop. The advantage of this ap-proach is
reaching a large number of nodes in a single hop and almost all of
the nodes in the network in two hops. The price paid is however
twofold, namely high power con-sumption and higher interference,
which results in a large number of collisions. If the link cost is
taken to be the transmitted power, it is straightforward to notice
that the Cost of the Links are equal to Pmax
Each mobile node has a direct link to the closest N out of (n-1)
mobile nodes. We call these N nodes a cluster. Given N, the mobile
node adjusts its power to reach at most the farthest node within
its cluster. However, we assume that there is no power adaptation
within the cluster. The advantages of this approach are lower power
consumption and possibly, a node's transmission will cause lower
interference to other simultaneous transmissions, when com-pared to
the previous case. The drawbacks are a higher number of hops might
have to be traversed in order to reach a destination, and there
exists the possibility of having iso-lated clusters. Note that link
costs (transmitted powers), in this context, are generally
different depending on the ra-dius of each cluster. Accordingly,
incorporating the minimum power routing algorithm is crucial to
limit power consumption.
Power Measurement
This procedure emulates the operation of mobile node j capturing
the beacon signal transmitted by node i during node i's allocated
signaling slot, where and i!=j. The received signal strength
depends solely on the transmitted power level (which is assumed to
be Pmax during this phase), the current positions of nodes i and j,
and the effect of the log-normal shadowing. Thus, the received
power level is computed by using the following formula:
As pointed out earlier, we rely on average power measurements
rather than instantaneous power measurements. This is due to the
fact that instantaneous measurements could be inaccurate in
reflecting the slowly varying channel conditions in the presence of
fast multipath fading. Therefore, a moving average is computed by
each node to average out the fast fading over a pre-specified
number of most recent instantaneous power measurements.
Power Management
There are two suggested approaches for power manage-ment in
mobile ad-hoc networks:
No power adjustment within a cluster. Power adjustment within a
cluster.
The basic difference between the two schemes is that in the
former scheme, the power needed to communicate with the farthest
node in the cluster is also used to communi-cate with any closer
node in the cluster. On the other hand, the latter scheme suggests
communicating with each node using the minimum power it needs for
reliable communi-cation. This introduces less interference to
simultaneous transmissions of other nodes.
The objective of defining a cluster is to reduce
colli-sions/interference and thereby improve the end-to-end
net-work throughput. As mentioned earlier, we assume a minimum
required level of received power, denoted Min-RecvPower, that is
necessary to guarantee a maximum ac-cteptable bit error rate. The
minimum power level to be transmitted by node i such that at least
the MinRecvPower level is achieved at node j for a given network
configura-tion is given by:
Chapter System DesignData Flow Diagram of the Technique
Forward if Current Node is CHControl Power based on BERPower
Measure
Sequence Diagram
Chapter Implementation. Cluster formation using a. degree b.
energyn handleHello method whenever a helloPacket Comes Energy will
be retrived from physical layer, Cluster Head CalculationDegree of
Neighborhood should be high,m Entropy, Low, Mobility low
evnumHost;cModule* sm = (cModule*)
simulation.module(parentModule()->id());aodv*s1=(aodv*)sm->submodule("route");int
cnt=0;/*for( cQueue::Iterator iter(s1->routeTab,1) ;
!iter.end(); iter++){cnt++;}ev