14 research outputs found
Energy-delay region of low duty cycle wireless sensor networks for critical data collection
Session: Sensor networksThe Conference program's website is located at http://ita.ucsd.edu/workshop/14/talksWe investigate the trade-off between energy consumption and delay for critical data collection in low duty cycle wireless sensor networks, where a causality constraint exists for routing and link scheduling. We characterize the energy-delay region (E-D region) and formulate a combinatorial optimization problem to determine the link scheduling with the causality constraint. A new multiple-degree ordered (MDO) coloring method is proposed to solve this problem with near-optimal delay performance. The impacts of many system parameters on the ED region are evaluated by extensive simulation, providing an insightful frame of reference for design of critical data collection wireless sensor networks.postprin
Multi-Channel Scheduling for Fast Convergecast in Wireless Sensor Networks
We explore the following fundamental question -
how fast can information be collected from a wireless sensor
network? We consider a number of design parameters such
as, power control, time and frequency scheduling, and routing.
There are essentially two factors that hinder efficient data
collection - interference and the half-duplex single-transceiver
radios. We show that while power control helps in reducing the
number of transmission slots to complete a convergecast under a
single frequency channel, scheduling transmissions on different
frequency channels is more efficient in mitigating the effects of
interference (empirically, 6 channels suffice for most 100-node
networks). With these observations, we define a receiver-based
channel assignment problem, and prove it to be NP-complete on
general graphs. We then introduce a greedy channel assignment
algorithm that efficiently eliminates interference, and compare
its performance with other existing schemes via simulations.
Once the interference is completely eliminated, we show that
with half-duplex single-transceiver radios the achievable schedule
length is lower-bounded by max(2nk â 1,N), where nk is the
maximum number of nodes on any subtree and N is the number
of nodes in the network. We modify an existing distributed time
slot assignment algorithm to achieve this bound when a suitable
balanced routing scheme is employed. Through extensive simulations,
we demonstrate that convergecast can be completed within
up to 50% less time slots, in 100-node networks, using multiple
channels as compared to that with single-channel communication.
Finally, we also demonstrate further improvements that are
possible when the sink is equipped with multiple transceivers
or when there are multiple sinks to collect data
Algorithms for Fast Aggregated Convergecast in Sensor Networks
Fast and periodic collection of aggregated data
is of considerable interest for mission-critical and continuous
monitoring applications in sensor networks. In the many-to-one
communication paradigm, referred to as convergecast, we focus
on applications wherein data packets are aggregated at each hop
en-route to the sink along a tree-based routing topology, and
address the problem of minimizing the convergecast schedule
length by utilizing multiple frequency channels. The primary
hindrance in minimizing the schedule length is the presence of
interfering links. We prove that it is NP-complete to determine
whether all the interfering links in an arbitrary network can
be removed using at most a constant number of frequencies.
We give a sufficient condition on the number of frequencies for
which all the interfering links can be removed, and propose a
polynomial time algorithm that minimizes the schedule length
in this case. We also prove that minimizing the schedule length
for a given number of frequencies on an arbitrary network is
NP-complete, and describe a greedy scheme that gives a constant
factor approximation on unit disk graphs. When the routing tree
is not given as an input to the problem, we prove that a constant
factor approximation is still achievable for degree-bounded trees.
Finally, we evaluate our algorithms through simulations and
compare their performance under different network parameters
Balanced Multi-Channel Data Collection in Wireless Sensor Networks
Data collection is an essential task in Wireless Sensor Networks (WSNs). In data collection process, the sensor nodes transmit their readings to a common base station called Sink. To avoid a collision, it is necessary to use the appropriate scheduling algorithms for data transmission. On the other hand, multi-channel design is considered as a promising technique to reduce network interference and latency of data collection. This technique allows parallel transmissions on different frequency channels, thus time latency will be reduced. In this paper, we present a new scheduling method for multi-channel WSNs called Balanced Multi Channel Data Collection (Balanced MC-DC) Algorithm. The proposed protocol is based on using both Non-Overlapping Channels (NOC) and Partially Overlapping Channels (POC). It uses a new approach that optimizes the processes of tree construction, channel allocation, transmission scheduling and balancing simultaneously. Extensive simulations confirm the superiority of the proposed algorithm over the existing algorithms in wireless sensor networks
A Hybrid based Distributed Slot Scheduling Approach for WSN MAC
In Wireless Sensor Networks(WSNs), collision handling during transmission of data is an important challenge. MAC protocol plays a vital role in handling those collisions. Among different types of MAC protocols, schedule based MAC protocol is one where a valid schedule is prepared to handle the collision. The existing schedule based MAC protocols focus on preparing either a feasible schedule or an optimal schedule. In order to satisfy both feasibility as well as optimality feature, in this paper, we proposed a hybrid approach for slot scheduling that prepares a feasible schedule in a distributed manner and at the same time reduces the number of slots in the feasible schedule to achieve optimality. In this paper, we named this as Hybrid based Distributed Slot Scheduling (HDSS) approach. The proposed HDSS algorithm initially prepares a feasible schedule which is further tuned in quick time to prepare a valid schedule with a reduced number of slots. The reduction of the number of slots in the schedule improves the efficiency of data transmission in terms of latency. The simulation results show that the HDSS algorithm outperforms RD-TDMA with respect to both the number of slots allotted for a feasible schedule as well as the data transmission latency
Many-to-One Communication Protocol for Wireless Sensor Networks
This paper proposes a novel communication protocol, called Many-to-One Sensors-to-Sink (MOSS), tailored to wireless sensor networks (WSNs). It exploits the unique sensors-to-sink traffic pattern to realize low-overhead medium access and low- latency sensors-to-sink routing paths. In conventional schedule-based MAC protocols such as S-MAC, sensor nodes in the proximity of the event generate reports simultaneously, causing unreliable and unpredictable performance during a brief but critical period of time when an event of interest occurs. MOSS is based on time division multiple access (TDMA) that avoids energy waste due to collisions, idle listening and overhearing and avoids unreliable behavior mentioned above. A small test-bed consisting of 12 TelosB motes as well as extensive simulation study based on ns-2 have shown that MOSS reduces the sensor-to-sink latency by as much as 50.5% while consuming only 12.8 ⌠19.2% of energy compared to conventional TDMA algorithm
Lower and upper bounds for deterministic convergecast with labeling schemes
In wireless networks, broadcast and convergecast are the two most used communication primitives. Broadcast instructs a specific sink (or root) node to send a message to each node in the network. Convergecast instructs each node in the network to send a message to the sink. Without labels, deterministic convergecast is impossible even in a three-nodes network. Therefore, networking solutions for convergecast are based on probabilistic approaches or use underlying probabilistic medium access protocols such as CSMA/CA or CSMA/CD. In this paper, we focus on deterministic convergecast algorithms enhanced with labeling schemes. We investigate two communication modes: half-duplex (nodes either transmit or receive but not both at the same time) and full-duplex (nodes can transmit and receive data at the same time). For these two modes we investigate time and labeling lower and upper bounds. Even though broadcast and convergecast are similar, we prove that, contrary to broadcast, deterministic convergecast cannot be solved with short labels for some topologies. That is, O(log(n)) bits are necessary to solve deterministically convergecast where n is the number of nodes in the network. We also prove that O(n) communication time slots is required. We provide solutions that are optimal in the worst case scenarios, in terms of labeling and communication