mac protocols and security in ad hoc and sensor networks
Post on 13-Jan-2016
16 Views
Preview:
DESCRIPTION
TRANSCRIPT
MAC Protocols and Security in Ad hoc and Sensor Networks
– A power control MAC A power control MAC protocol allows nodes to vary transmit power level on a protocol allows nodes to vary transmit power level on a
per-packet basisper-packet basis
– Earlier work has used different power levels for RTS-CTS and DATA-ACK, Earlier work has used different power levels for RTS-CTS and DATA-ACK,
specifically, maximum transmit power is used for RTS-CTS and minimum specifically, maximum transmit power is used for RTS-CTS and minimum
required transmit power is used for DATA-ACK transmissionsrequired transmit power is used for DATA-ACK transmissions
– These protocols may increase collisions, degrade network throughput and result These protocols may increase collisions, degrade network throughput and result
in higher energy consumption than when using IEEE 802.11 without power in higher energy consumption than when using IEEE 802.11 without power
controlcontrol
– Power saving mechanismsPower saving mechanisms allow nodes to enter a allow nodes to enter a doze statedoze state by powering off its by powering off its
wireless network interface whenever possiblewireless network interface whenever possible
– Power control schemesPower control schemes vary transmit power to reduce energy consumption vary transmit power to reduce energy consumption
A Power Control MAC (PCM) Protocol for Ad hoc Networks[Jung+ 2002]
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
– Specifies two MAC protocols:Specifies two MAC protocols:
Point Coordination Function (PCF) Point Coordination Function (PCF) centralized centralized
Distributed Coordination Function (DCF) Distributed Coordination Function (DCF) distributeddistributed
Transmission range:Transmission range:
When a node is in transmission range of a sender node, it can receive andWhen a node is in transmission range of a sender node, it can receive andcorrectly decode packets from sender node.correctly decode packets from sender node.
Carrier Sensing Range:Carrier Sensing Range:
Nodes in carrier sensing range can sense the sender’s transmission. It is generally Nodes in carrier sensing range can sense the sender’s transmission. It is generally
larger than transmission range. Both carrier sensing range and transmission rangelarger than transmission range. Both carrier sensing range and transmission range
Depends on the transmit power level.Depends on the transmit power level.
Power Control MAC (PCM)
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
Carrier Sensing Zone:Carrier Sensing Zone:
Nodes can sense the signal, but cannot decode it correctly. The carrier sensing zone Nodes can sense the signal, but cannot decode it correctly. The carrier sensing zone
does not include transmission rangedoes not include transmission range
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
– DCF in IEEE 802.11 is based on CSMA/CS (Carrier Sense Multiple Access with DCF in IEEE 802.11 is based on CSMA/CS (Carrier Sense Multiple Access with
Collision Avoidance)Collision Avoidance)
– Each node in IEEE 802.11 maintains a NAV (Network Allocation Vector) that Each node in IEEE 802.11 maintains a NAV (Network Allocation Vector) that
indicates the remaining time of the on-going transmission sessionsindicates the remaining time of the on-going transmission sessions
– Carrier sensing is performed using physical carrier sensing (by air interface) and Carrier sensing is performed using physical carrier sensing (by air interface) and
virtual carrier sensing (uses the duration of the packet transmission that is virtual carrier sensing (uses the duration of the packet transmission that is
included in the header of RTS, CTS and DATA frames)included in the header of RTS, CTS and DATA frames)
– Using the duration information in RTS, CTS and DATA packets, nodes update Using the duration information in RTS, CTS and DATA packets, nodes update
their NAVs whenever they receive a packettheir NAVs whenever they receive a packet
– The channel is considered busy if either physical or virtual carrier sensing The channel is considered busy if either physical or virtual carrier sensing
indicates that channel is busyindicates that channel is busy
– Figure 2 shows how nodes in transmission range and the carrier sensing zone Figure 2 shows how nodes in transmission range and the carrier sensing zone
adjust their NAVs during RTS-CTS-DATA-ACK transmission adjust their NAVs during RTS-CTS-DATA-ACK transmission
Power Control MAC (PCM)
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
– IFS is the time interval between frames and IEEE 802.11 defines four IFSs which IFS is the time interval between frames and IEEE 802.11 defines four IFSs which
provide priority levels for accessing the channel provide priority levels for accessing the channel
SIFS (short interframe space)SIFS (short interframe space)
PIFS (Point Coordination Function interframe space)PIFS (Point Coordination Function interframe space)
DIFS (Distributed Coordination Function interframe space)DIFS (Distributed Coordination Function interframe space)
EIFS (extended interframe space)EIFS (extended interframe space)
– SIFS is the shortest and is used after RTS, CTS, and DATA frames to give the SIFS is the shortest and is used after RTS, CTS, and DATA frames to give the
highest priority to CTS, DATA and ACK respectivelyhighest priority to CTS, DATA and ACK respectively
– In DCF, when the channel is idle, a node waits for DIFS duration before transmittingIn DCF, when the channel is idle, a node waits for DIFS duration before transmitting
– Nodes in the transmission range correctly set their NAVs when receiving RTS/CTSNodes in the transmission range correctly set their NAVs when receiving RTS/CTS
– Since nodes in carrier sensing zone cannot decode the packet, they do not know Since nodes in carrier sensing zone cannot decode the packet, they do not know
the duration of the packet transmission. So, they set their NAVs for the EIFS the duration of the packet transmission. So, they set their NAVs for the EIFS
duration to avoid collision with the ACK reception at the source nodeduration to avoid collision with the ACK reception at the source node
Power Control MAC (PCM)
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
– The intuition behind EIFS is to provide enough time for a source node to receive the The intuition behind EIFS is to provide enough time for a source node to receive the
ACK frame, meaning that duration of EIFS is longer than that of ACK transmissionACK frame, meaning that duration of EIFS is longer than that of ACK transmission
– In PCM, nodes in the carrier sensing zone use EIFS whenever they can sense the In PCM, nodes in the carrier sensing zone use EIFS whenever they can sense the
signal but cannot decode itsignal but cannot decode it
– IEEE 802.11 does not completely prevent collisions due to the IEEE 802.11 does not completely prevent collisions due to the hidden terminalhidden terminal
problem (nodes in the receiver’s carrier sensing zone, but not in the sender’s carrier problem (nodes in the receiver’s carrier sensing zone, but not in the sender’s carrier
sensing zone or transmission range, can cause a collision with the reception of a sensing zone or transmission range, can cause a collision with the reception of a
DATA packet at the receiverDATA packet at the receiver
– In Figure 3, suppose node C transmits packet to node DIn Figure 3, suppose node C transmits packet to node D
– When C and D transmit an RTS and CTS respectively, A and F set their NAVs for When C and D transmit an RTS and CTS respectively, A and F set their NAVs for
EIFS durationEIFS duration
– During C’s data transmission, A defers its transmission due to sensing C’s During C’s data transmission, A defers its transmission due to sensing C’s
transmission. However, since node F does not sense any signal during C’s transmission. However, since node F does not sense any signal during C’s
transmission, it considers channel to be idle (F is in D’s carrier sensing zone, but not transmission, it considers channel to be idle (F is in D’s carrier sensing zone, but not
in D’s)in D’s)
Power Control MAC (PCM)
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
D’s carrier sensing rangeC’s carrier sensing range
IEEE 802.11 MAC ProtocolIEEE 802.11 MAC Protocol
– When F starts a new transmission, it can cause a collision with the reception of When F starts a new transmission, it can cause a collision with the reception of
DATA at DDATA at D
– Since F is outside of D’s transmission range, D may be outside of F’s transmission Since F is outside of D’s transmission range, D may be outside of F’s transmission
range; however, since F is in D’s carrier sensing zone, F can provide interference at range; however, since F is in D’s carrier sensing zone, F can provide interference at
node D to cause collision with DATA being received at Dnode D to cause collision with DATA being received at D
Power Control MAC (PCM)
BASIC Power Control ProtocolBASIC Power Control Protocol
– Power control can reduce energy consumptionPower control can reduce energy consumption
– Power control may bring different transmit power levels at different hosts, creating Power control may bring different transmit power levels at different hosts, creating
an asymmetric scenarios where a node A can reach node B, but node B cannot an asymmetric scenarios where a node A can reach node B, but node B cannot
reach node A and collisions may also increase a resultreach node A and collisions may also increase a result
– In Figure 4, suppose nodes A and B use lower power level than nodes C and DIn Figure 4, suppose nodes A and B use lower power level than nodes C and D
– When A is transmitting to B, C and D may not sense the transmissionWhen A is transmitting to B, C and D may not sense the transmission
– When C and D transmit to each other using higher power, their transmission may When C and D transmit to each other using higher power, their transmission may
collide with the on-going transmission from A to Bcollide with the on-going transmission from A to B
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
BASIC Power Control ProtocolBASIC Power Control Protocol
– As a solution to this problem, RTS-CTS are transmitted at the highest possible As a solution to this problem, RTS-CTS are transmitted at the highest possible
power level but DATA and ACK at the minimum power level necessary to power level but DATA and ACK at the minimum power level necessary to
communicatecommunicate
– In Figure 5, nodes A and B send RTS and CTS respectively with highest power In Figure 5, nodes A and B send RTS and CTS respectively with highest power
level such that node C receives the CTS and defers its transmissionlevel such that node C receives the CTS and defers its transmission
– By using a lower power level for DATA and ACK packets, nodes can save energyBy using a lower power level for DATA and ACK packets, nodes can save energy
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
BASIC Power Control ProtocolBASIC Power Control Protocol
– In the BASIC scheme, RTS-CTS handshake is used to decide the transmission In the BASIC scheme, RTS-CTS handshake is used to decide the transmission
power for subsequent DATA and ACK packets which can be achieved in two power for subsequent DATA and ACK packets which can be achieved in two
different waysdifferent ways
Suppose node A wants to send a packet to node B. Node A transmit RTS at Suppose node A wants to send a packet to node B. Node A transmit RTS at
power level power level ppmaxmax (maximum possible). When B receives the RTS from A with (maximum possible). When B receives the RTS from A with
signal level signal level ppr,r, B calculates the minimum necessary transmission power level, B calculates the minimum necessary transmission power level,
ppdesireddesired. For the DATA packet based on received power level, . For the DATA packet based on received power level, pprr, transmitted , transmitted
power level, power level, ppmaxmax, and noise level at the receiver B. Node B specifies , and noise level at the receiver B. Node B specifies ppdesired desired in in
its CTS to node A. After receiving CTS, node A sends DATA using power level its CTS to node A. After receiving CTS, node A sends DATA using power level
ppdesired.desired.
When a destination node receives an RTS, it responds by sending a CTS (at When a destination node receives an RTS, it responds by sending a CTS (at
power level power level ppmaxmax). When source node receives CTS, it calculates ). When source node receives CTS, it calculates ppdesireddesired based based
on received power level, on received power level, pprr, and transmitted power level (, and transmitted power level (ppmaxmax) as) as
PPdesired desired = = (p(pmaxmax / / pprr) x Rx) x Rxthreshthresh x c x c
where where RxRxthreshthresh is minimum necessary received signal strength and c is constant is minimum necessary received signal strength and c is constant
Power Control MAC (PCM)
BASIC Power Control ProtocolBASIC Power Control Protocol
– The second alternative makes two assumptions:The second alternative makes two assumptions:
Signal attenuation between source and destination nodes is assumed to be the Signal attenuation between source and destination nodes is assumed to be the
same in both directionssame in both directions
Noise level at the receiver is assumed to be below some predefined threshold Noise level at the receiver is assumed to be below some predefined threshold
Deficiency of the BASIC ProtocolDeficiency of the BASIC Protocol
– In Figure 6, suppose node D wants to transmit to node EIn Figure 6, suppose node D wants to transmit to node E
– When nodes D and E transmits RTS and CTS respectively, B and C receives RTS When nodes D and E transmits RTS and CTS respectively, B and C receives RTS
and F and G receives CTS, therefore, these nodes defer their transmissionsand F and G receives CTS, therefore, these nodes defer their transmissions
– Since node A is in carrier sensing zone of node D, it sets its NAV for EIFS durationSince node A is in carrier sensing zone of node D, it sets its NAV for EIFS duration
– Similarly node H sets its NAV for EIFS duration when it senses transmission from ESimilarly node H sets its NAV for EIFS duration when it senses transmission from E
– When source and destination decide to reduce the transmit power for DATA-ACK, When source and destination decide to reduce the transmit power for DATA-ACK,
not only transmission range for DATA-ACK but also carrier sensing zone is also not only transmission range for DATA-ACK but also carrier sensing zone is also
smaller than RTS-CTS smaller than RTS-CTS
Power Control MAC (PCM)
Deficiency of the BASIC ProtocolDeficiency of the BASIC Protocol
– Thus, only C and F correctly Thus, only C and F correctly
receives DATA and ACK packetsreceives DATA and ACK packets
– Since nodes A and H cannot Since nodes A and H cannot
sense the transmissions, they sense the transmissions, they
consider channel is idle and start consider channel is idle and start
transmitting at high power level transmitting at high power level
which will cause collision with the which will cause collision with the
ACK packet at D and DATA packet ACK packet at D and DATA packet
at Eat E
– This results in throughput This results in throughput
degradation and higher energy degradation and higher energy
consumption (due to consumption (due to
retransmissions)retransmissions)
Power Control MAC (PCM)
[Figure adapted from Jung+ 2002]
Proposed Power Control MAC ProtocolProposed Power Control MAC Protocol
– Proposed Power Control MAC (PCM) is similar to BASIC scheme such that it uses Proposed Power Control MAC (PCM) is similar to BASIC scheme such that it uses
power level, power level, ppmaxmax, for RTS-CTS and the minimum necessary transmit power for , for RTS-CTS and the minimum necessary transmit power for
DATA-ACK transmissionsDATA-ACK transmissions
– Procedure of PCM is as follows:Procedure of PCM is as follows:
1.1. Source and destination nodes transmit the RTS and CTS using Source and destination nodes transmit the RTS and CTS using ppmax.max. Nodes in Nodes in
the carrier sensing zone set their NAVs for EIFS durationthe carrier sensing zone set their NAVs for EIFS duration
2.2. The source may transmit DATA using a lower power level The source may transmit DATA using a lower power level
3.3. Source transmits DATA at level of Source transmits DATA at level of ppmaxmax, periodically, for enough time so that , periodically, for enough time so that
nodes in the carrier sensing zone can sense it and this would avoid collision nodes in the carrier sensing zone can sense it and this would avoid collision
with the ACK packetswith the ACK packets
4.4. The destination node transmits an ACK using the minimum required power to The destination node transmits an ACK using the minimum required power to
reach the source nodereach the source node
– Figure 7 presents how the transmit power level changes during the sequence of Figure 7 presents how the transmit power level changes during the sequence of
RTS-CTS-DATA-ACK transmission RTS-CTS-DATA-ACK transmission
Power Control MAC (PCM)
Power Control MAC (PCM)
Proposed Power Control MAC ProtocolProposed Power Control MAC Protocol
– The difference between PCM and BASIC scheme is that PCM periodically increases The difference between PCM and BASIC scheme is that PCM periodically increases
the transmit power to the transmit power to ppmaxmax during the DATA packet transmission. Nodes that can during the DATA packet transmission. Nodes that can
interfere with the reception of ACK at the sender will periodically sense the channel interfere with the reception of ACK at the sender will periodically sense the channel
is busy and defer their own transmission. Since nodes reside in the carrier sensing is busy and defer their own transmission. Since nodes reside in the carrier sensing
zone defer for EIFS duration, the transmit power for DATA is increased once every zone defer for EIFS duration, the transmit power for DATA is increased once every
EIFS durationEIFS duration
– PCM solves the problem posed with BASIC scheme and can achieve throughput PCM solves the problem posed with BASIC scheme and can achieve throughput
comparable to 802.11 by using less energycomparable to 802.11 by using less energy
– PCM, like 802.11, does not prevent collisions completelyPCM, like 802.11, does not prevent collisions completely
[Figure adapted from Jung+ 2002]
– S- MAC S- MAC protocol designed specifically for sensor networks to reduce energy protocol designed specifically for sensor networks to reduce energy
consumption while achieving good scalability and collision avoidance by utilizing consumption while achieving good scalability and collision avoidance by utilizing
a combined scheduling and contention schemea combined scheduling and contention scheme
– The major sources of energy waste are:The major sources of energy waste are:
1.1. collisioncollision
2.2. overhearingoverhearing
3.3. control packet overheadcontrol packet overhead
4.4. idle listeningidle listening
– S-MAC reduce the waste of energy from all the sources mentioned in exchange S-MAC reduce the waste of energy from all the sources mentioned in exchange
of some reduction in both per-hop fairness and latencyof some reduction in both per-hop fairness and latency
An Energy-Efficient MAC Protocol for Wireless Sensor Networks (S-MAC)[Ye+ 2002]
– S- MAC S- MAC protocol consist of three major components:protocol consist of three major components:
1.1. periodic listen and sleepperiodic listen and sleep
2.2. collision and overhearing avoidancecollision and overhearing avoidance
3.3. Message passingMessage passing
– Contributions of S-MAC are:Contributions of S-MAC are:
The scheme of periodic listen and sleep helps in reducing energy The scheme of periodic listen and sleep helps in reducing energy
consumption by avoiding idle listening. The use of synchronization to consumption by avoiding idle listening. The use of synchronization to
form virtual clusters of nodes on the same sleep scheduleform virtual clusters of nodes on the same sleep schedule
In-channel signaling puts each node to sleep when its neighbor is In-channel signaling puts each node to sleep when its neighbor is
transmitting to another node (solves the overhearing problem and transmitting to another node (solves the overhearing problem and
does not require additional channel)does not require additional channel)
Message passing technique to reduce application-perceived latency Message passing technique to reduce application-perceived latency
and control overhead (per-node fragment level fairness is reduced)and control overhead (per-node fragment level fairness is reduced)
Evaluating an implementation of S-MAC over sensor-net specific Evaluating an implementation of S-MAC over sensor-net specific
hardwarehardware
S-MAC
– Security in wireless ad hoc networks is difficult for many reasons:Security in wireless ad hoc networks is difficult for many reasons:
Vulnerability of channelsVulnerability of channels
Vulnerability of nodesVulnerability of nodes
Absence of infrastructureAbsence of infrastructure
Dynamically changing topologyDynamically changing topology
– The problem is broad and there is no general solutionThe problem is broad and there is no general solution
– Different applications will have different security requirementsDifferent applications will have different security requirements
– Security aspects can be categorized into four groups:Security aspects can be categorized into four groups:
1.1. Trust and key managementTrust and key management
2.2. Secure routing and intrusion detectionSecure routing and intrusion detection
3.3. AvailabilityAvailability
4.4. Cryptographic protocolsCryptographic protocols
Security in Wireless Ad hoc Networks[Buttyan+ 2002]
References [Jung+ 2002] E.-S. Jung and N.H. Vaidya, A Power Control MAC Protocol for Ad hoc Networks,
Proceedings of ACM MOBICOM 2002, Atlanta, Georgia, September 23-28, 2002.
[Ye+ 2002] W. Yei, J. Heidemann and D. Estrin, Energy-Efficient MAC Protocol for Wireless Sensor Networks, Proceedings of the Twenty First International Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM 2002), New York, NY, USA, June 23-27 2002.
[Buttyan+ 2002] L. Buttyan and J.-P. Hubaux, Report on a Working Session on Security in Wireless Ad Hoc Networks, Mobile Computing and Communications Review, Volume 6, Number 4.
top related