An Enhanced Cross-Layer Protocol An Enhanced Cross-Layer Protocol for Energy Efficiency in Wireless for Energy Efficiency in Wireless

Sensor NetworksSensor Networks

Jaehyun Kim, Dept. of Electrical & Electronic Eng., Yonsei University; Seoul, KoreaJaehyun Kim, Dept. of Electrical & Electronic Eng., Yonsei University; Seoul, KoreaJaiyong Lee, Dept. of Electrical & Electronic Eng., Yonsei University; Seoul, KoreaJaiyong Lee, Dept. of Electrical & Electronic Eng., Yonsei University; Seoul, Korea

Seoggyu Kim, Dept. Information & Computer Eng., Andong National University; Andong, Seoggyu Kim, Dept. Information & Computer Eng., Andong National University; Andong, KoreaKorea

Presented by: Jordan TempletonPresented by: Jordan TempletonEEL 6935GEEL 6935GFall 2011Fall 2011

IntroductionIntroduction

Wireless sensor networks are severely Wireless sensor networks are severely limited in system resources.limited in system resources.

Bandwidth requirements are generally Bandwidth requirements are generally very low compared to traditional networks.very low compared to traditional networks.

These factors require significantly different These factors require significantly different network management techniques.network management techniques.

ObjectivesObjectives

Most important goal is to maximize the Most important goal is to maximize the lifetime of the network.lifetime of the network.

Integrity of transmitted data is a priority.Integrity of transmitted data is a priority.

Throughput is not as critical as latency Throughput is not as critical as latency due to low bandwidth requirements.due to low bandwidth requirements.

Influential WorkInfluential Work

S-MACS-MAC T-MACT-MAC AODVAODV DSRDSR AD-MACAD-MAC

Enhanced Cross-Layer Enhanced Cross-Layer ProtocolProtocol

Tree-based routing algorithmTree-based routing algorithm Improves upon S-MAC and T-MACImproves upon S-MAC and T-MAC Major difference is the addition of the Major difference is the addition of the

SYNCSYNCreplyreply packet packet SYNCSYNCreplyreply packet is used to convey packet is used to convey

information about energy cost for a information about energy cost for a given link.given link.

SYNC packetSYNC packet

Exclusively for synchronization in S-MAC Exclusively for synchronization in S-MAC and T-MAC.and T-MAC.

ECLP also uses for routing management.ECLP also uses for routing management.

ECLP adds SYNCECLP adds SYNCreplyreply for network for network configuration.configuration.

SYNC packetSYNC packet Used primarily to configure routing tree.Used primarily to configure routing tree. Similar to implementation in S-MAC and T-MAC.Similar to implementation in S-MAC and T-MAC. Five additional fields for ECLP.Five additional fields for ECLP. r_lth: routing length.r_lth: routing length. r_cost: routing cost in terms of energy.r_cost: routing cost in terms of energy. thresholds: relative to remaining energy.thresholds: relative to remaining energy. parents: parent nodes in branch tree.parents: parent nodes in branch tree. status: intermediate, leaf, danger, or status: intermediate, leaf, danger, or

emergency.emergency.

SYNCSYNCreplyreply packet packet

Unique to ECLP.Unique to ECLP. Modified from SYNC packet .Modified from SYNC packet . Two packets are replaced, r_lth and Two packets are replaced, r_lth and

parent.parent. r_lthr_lthtotaltotal: used to track hop count.: used to track hop count. sink: identification of root node in sink: identification of root node in

branch.branch.

Establishing Routing TreeEstablishing Routing Tree

Initial setup starts at the sink node.Initial setup starts at the sink node. The SYNC packet is transmitted from the sink node to The SYNC packet is transmitted from the sink node to

its neighbors, then to their neighbors, and so on.its neighbors, then to their neighbors, and so on. Initially, r_lth and r_cost for all sensor nodes are set to Initially, r_lth and r_cost for all sensor nodes are set to

maximum value of 255; single byte parameter.maximum value of 255; single byte parameter. Initially for sink node, r_lth=0 and r_cost=255.Initially for sink node, r_lth=0 and r_cost=255. r_lth is incremented by 1 at each stage and r_cost is r_lth is incremented by 1 at each stage and r_cost is

calculated locally by each node.calculated locally by each node. Each node chooses parent nodes based on lowest Each node chooses parent nodes based on lowest

received r_lth and r_cost values and creates a list of received r_lth and r_cost values and creates a list of neighbors.neighbors.

SYNCSYNCreplyreply packet is used as a confirmation and to return packet is used as a confirmation and to return r_lthr_lthtotaltotal value for determining a hop count. value for determining a hop count.

Link Failure Detection Link Failure Detection MethodMethod

WSNs are susceptible to interruptions.WSNs are susceptible to interruptions.

ECLP incorporates a method to reestablish a ECLP incorporates a method to reestablish a communication link between nodes in the event of a communication link between nodes in the event of a failure.failure.

Link failures must first be detected; ECLP uses RTS and Link failures must first be detected; ECLP uses RTS and CTS messages.CTS messages.

Data transmission is preceded by an RTS message and Data transmission is preceded by an RTS message and a failure is assumed if no CTS message is received after a failure is assumed if no CTS message is received after sending 3 RTS messages.sending 3 RTS messages.

Link Failure Recovery Link Failure Recovery MethodMethod

The first step is for a node to check its neighbor The first step is for a node to check its neighbor list for an alternate parent node.list for an alternate parent node.

The r_lth value is set to 255 for the original The r_lth value is set to 255 for the original parent node to signify that the node is disabled.parent node to signify that the node is disabled.

The PERR (Path ERRor) packet is used when no The PERR (Path ERRor) packet is used when no alternate parent node was part of the neighbor alternate parent node was part of the neighbor list.list.

This packet is similar to the SYNC packet but This packet is similar to the SYNC packet but contains an identification field to indicate that contains an identification field to indicate that its sender needs a new parent node.its sender needs a new parent node.

Adaptive Duty Cycling for Energy Adaptive Duty Cycling for Energy EfficiencyEfficiency

Allows nodes to utilize sleep mode in Allows nodes to utilize sleep mode in order to avoid energy waste from order to avoid energy waste from overhearing.overhearing.

Variable time-out period to initiate sleep Variable time-out period to initiate sleep period if no communication is necessary.period if no communication is necessary.

RRTS (Reservation Ready-to-Send) RRTS (Reservation Ready-to-Send) packet used to limit overhearing by packet used to limit overhearing by allowing unintended nodes to sleep.allowing unintended nodes to sleep.

Evaluation Method and Evaluation Method and ParametersParameters

ECLP was compared to IEEE 802.11 with ECLP was compared to IEEE 802.11 with AODV and with DSR, and to S-MAC with AODV and with DSR, and to S-MAC with AODV and with DSR.AODV and with DSR.

The evaluation was performed via ns-2 The evaluation was performed via ns-2 which is a network simulation tool.which is a network simulation tool.

The simulations were configured with 20 The simulations were configured with 20 and 50 nodes.and 50 nodes.

Each simulation randomly chose one node Each simulation randomly chose one node to move away from its original location.to move away from its original location.

Average Energy Consumption (20 Average Energy Consumption (20 nodes)nodes)

E802_11 = Etrans + Erecv + Eidle

ESMAC/ECLP = Etrans + Erecv + Eidle + Esleep

Average Energy Consumption (50 Average Energy Consumption (50 nodes)nodes)

E802_11 = Etrans + Erecv + Eidle

ESMAC/ECLP = Etrans + Erecv + Eidle + Esleep

Average End-to-End Delay (20 nodes)Average End-to-End Delay (20 nodes)

Average End-to-End Delay (50 nodes)Average End-to-End Delay (50 nodes)

Control OverheadControl Overhead Simulation only performed Simulation only performed

with 20 nodeswith 20 nodes

ConclusionConclusion Average energy consumption appears to be primarily Average energy consumption appears to be primarily

dependent upon node quantity and relatively constant relative dependent upon node quantity and relatively constant relative to data rate.to data rate.

ECLP had the lowest average energy consumption while IEEE ECLP had the lowest average energy consumption while IEEE 802.11 was highest. The differences between DSR and AODV 802.11 was highest. The differences between DSR and AODV were negligible.were negligible.

Average end-to-end delay was lowest for IEEE 802.11 and was Average end-to-end delay was lowest for IEEE 802.11 and was relatively unaffected whether DSR or AODV were chosen. The relatively unaffected whether DSR or AODV were chosen. The highest delay occurred with S-MAC and, again, was relatively highest delay occurred with S-MAC and, again, was relatively unaffected by the choice of AODV or DSR. ECLP was unaffected by the choice of AODV or DSR. ECLP was consistently in the mid range. Average delay scaled with node consistently in the mid range. Average delay scaled with node quantity and had very little dependence on actual data rate.quantity and had very little dependence on actual data rate.

Energy consumption from network control was much more Energy consumption from network control was much more significant at for all of the protocols. ECLP had much lower significant at for all of the protocols. ECLP had much lower control related energy consumption compared to IEEE 802.11. control related energy consumption compared to IEEE 802.11. Again, the difference between AODV and DSR was negligible. Again, the difference between AODV and DSR was negligible.

ReferencesReferences

Jaehyun Kim; Jaiyong Lee; Seoggyu Kim; , "An Enhanced Cross-Layer Protocol for Jaehyun Kim; Jaiyong Lee; Seoggyu Kim; , "An Enhanced Cross-Layer Protocol for Energy Efficiency in Wireless Sensor Networks," Energy Efficiency in Wireless Sensor Networks," Sensor Technologies and Sensor Technologies and Applications, 2009. SENSORCOMM '09. Third International Conference onApplications, 2009. SENSORCOMM '09. Third International Conference on , vol., no., , vol., no., pp.657-664, 18-23 June 2009pp.657-664, 18-23 June 2009