MMAC: A Mobility- Adaptive, Collision-Free MAC Protocol for Wireless Sensor Networks Muneeb Ali, Tashfeen Suleman, and Zartash Afzal Uzmi IEEE Performance, Computing, and Communications Conference (IPCCC), 2005

Outline Introduction Introduction Concept Concept MMAC (Mobility-Adaptive, Collision- Free MAC) MMAC (Mobility-Adaptive, Collision- Free MAC) Simulation results Simulation results Conclusions Conclusions

Introduction(1) Traditional MAC protocols for wireless networks were designed to Traditional MAC protocols for wireless networks were designed to –Maximize channel utilization –Promote fair usage of channel –Reduce latency

Introduction(2) MAC protocols for sensor networks sometimes assume MAC protocols for sensor networks sometimes assume –Static sensor nodes –Energy efficiency

Introduction(3) In mobile environments, the fixed frame time of current MAC protocols cause performance degradation In mobile environments, the fixed frame time of current MAC protocols cause performance degradation 1.Joining of Mobile nodes have to wait for a long time 2.Packets collisions in contention-based MAC protocols 3.2-hop information in schedule-based MAC protocols is inconsistent

Goal of MMAC To introduce a mobility-adaptive frame time to dynamically adapt to changes in mobility patterns To introduce a mobility-adaptive frame time to dynamically adapt to changes in mobility patterns

Concept(1)

Concept(2)

Mobility in Sensor Networks Weak mobility Weak mobility –A node fails –A node joins Strong mobility Strong mobility –Concurrent nodes joins/failures –Nodes physical move from their location –Nodes have motion in the medium

Problem Definition(1)

Problem Definition(2) If a node β is expected to leave N 2 (α) during F i, then β N 2 (α) from the START of F i If a node β is expected to leave N 2 (α) during F i, then β N 2 (α) from the START of F i from the START of F i from the START of F i

Mobility Estimation(1)

Mobility Estimation(2) The mobile node ’ s state is defined by a column vector The mobile node ’ s state is defined by a column vector –S t is the mobility state –(x t, y t ) specify position – specify velocity – specify acceleration –‘ specifies the matrix transpose operator

Mobility-Adaptive Algorithm(1) 1. For all nodes, calculate optimal predicted states where max = frame time, t = starting time of F i To estimate the mobility state info and to calculate the position of α in F i Logical meaning:

Mobility-Adaptive Algorithm(2) To calculate nodes who will join or part from β ’ s 2-hop neighbors Logical meaning:

Mobility-Adaptive Algorithm(3) If the number of nodes who will join and part from β greater than λ max, decrease the frame time Logical meaning: If the number of nodes who will join and part from β less than λ max, increase the frame time Logical meaning:

Protocol Issues Mobility Information Mobility Information –Mobility information could not be known by all 2-hop neighbors Synchronization Synchronization –Nodes could independently calculate frame times different from each other

Solution to Protocol Issues A variation of the cluster head selection and rotation mechanism of LEACH is applied A variation of the cluster head selection and rotation mechanism of LEACH is applied –Use cluster heads to collect and disseminate the mobility information within a cluster –Use cluster heads to let all nodes within a cluster have the same frame length

Simulation Parameters Simulation is based on ns2 Simulation is based on ns2 Transmission range: 100m Transmission range: 100m Deploy area: 500m X 500m Deploy area: 500m X 500m All sinks are corner-sinks All sinks are corner-sinks Nodes forward packets to the node closer to the sink Nodes forward packets to the node closer to the sink

Average Packet Delay vs. Packet Generation rate

Average Packet Delay vs. Mobility Speed

Packet Received % vs. Packet Generation rate

Packet Received % vs. Mobility Speed

Avg. Energy Used vs. Load

Avg. Energy Used vs. Mobility Speed

Conclusions This paper presents a new scheduled- based MAC protocol (MMAC) for WSN This paper presents a new scheduled- based MAC protocol (MMAC) for WSN According to mobility, MMAC adapts According to mobility, MMAC adapts –Frame time –Transmission slots –Random-access slots

Thank you!!

Cluster Head Selection P: the cluster-head probability r : the number of current rounds G: set of nodes have not been cluster-heads in the last 1/P rounds E: energy

Node α Receives 2 Different Frame Lengths α keeps silent during this overlap period