28 research outputs found
Socio-economic aware data forwarding in mobile sensing networks and systems
The vision for smart sustainable cities is one whereby urban sensing is core to optimising city
operation which in turn improves citizen contentment. Wireless Sensor Networks are envisioned
to become pervasive form of data collection and analysis for smart cities but deployment of
millions of inter-connected sensors in a city can be cost-prohibitive. Given the ubiquity and
ever-increasing capabilities of sensor-rich mobile devices, Wireless Sensor Networks with Mobile
Phones (WSN-MP) provide a highly flexible and ready-made wireless infrastructure for future
smart cities. In a WSN-MP, mobile phones not only generate the sensing data but also relay the
data using cellular communication or short range opportunistic communication. The largest
challenge here is the efficient transmission of potentially huge volumes of sensor data over
sometimes meagre or faulty communications networks in a cost-effective way.
This thesis investigates distributed data forwarding schemes in three types of WSN-MP: WSN
with mobile sinks (WSN-MS), WSN with mobile relays (WSN-HR) and Mobile Phone Sensing
Systems (MPSS). For these dynamic WSN-MP, realistic models are established and distributed
algorithms are developed for efficient network performance including data routing and forwarding,
sensing rate control and and pricing. This thesis also considered realistic urban sensing
issues such as economic incentivisation and demonstrates how social network and mobility
awareness improves data transmission. Through simulations and real testbed experiments, it
is shown that proposed algorithms perform better than state-of-the-art schemes.Open Acces
Minimum Energy Broadcast in Duty Cycled Wireless Sensor Networks
We study the problem of finding a minimum energy broadcast tree in duty cycled wireless sensor networks. In such networks, every node has a wakeup schedule and is awake and ready to receive packets or transmit in certain time slots during the schedule and asleep during the rest of the schedule. We assume that a forwarding node needs to stay awake to forward a packet to the next hop neighbor until the neighbor is awake. The minimum energy broadcast tree minimizes the number of additional time units that nodes have to stay awake in order to accomplish broadcast. We show that finding the minimum energy broadcast tree is NP-hard. We give two algorithms for finding energy-efficient broadcast trees in such networks. We performed extensive simulations to study the performance of these algorithms and compare them with previously proposed algorithms. Our results show that our algorithms exhibit the best performance in terms of average number of additional time units a node needs to be awake, as well as in terms of the smallest number of highly loaded nodes, while being competitive with previous algorithms in terms of the total number of transmissions and delay
Energy Efficient Downstream Communication in Wireless Sensor Networks
This dissertation studies the problem of energy efficient downstream communication in Wireless Sensor Networks (WSNs). First, we present the Opportunistic Source Routing (OSR), a scalable, reliable, and energy-efficient downward routing protocol for individual node actuation in data collection WSNs. OSR introduces opportunistic routing into traditional source routing based on the parent set of a node’s upward routing in data collection, significantly addressing the drastic link dynamics in low-power and lossy WSNs. We devise a novel adaptive Bloom filter mechanism to effectively and efficiently encode a downward source-route in OSR, which enables a significant reduction of the length of source-route field in the packet header. OSR is scalable to very large-size WSN deployments, since each resource-constrained node in the network stores only the set of its direct children. The probabilistic nature of the Bloom filter passively explores opportunistic routing. Upon a delivery failure at any hop along the downward path, OSR actively performs opportunistic routing to bypass the obsolete/bad link. The evaluations in both simulations and real-world testbed experiments demonstrate that OSR significantly outperforms the existing approaches in scalability, reliability, and energy efficiency. Secondly, we propose a mobile code dissemination tool for heterogeneous WSN deployments operating on low power links. The evaluation in lab experiment and a real world WSN testbed shows how our tool reduces the laborious work to reprogram nodes for updating the application. Finally, we present an empirical study of the network dynamics of an out-door heterogeneous WSN deployment and devise a benchmark data suite. The network dynamics analysis includes link level characteristics, topological characteristics, and temporal characteristics. The unique features of the benchmark data suite include the full path information and our approach to fill the missing paths based on the principle of the routing protocol
Millimeter Wave Cellular Networks: A MAC Layer Perspective
The millimeter wave (mmWave) frequency band is seen as a key enabler of
multi-gigabit wireless access in future cellular networks. In order to overcome
the propagation challenges, mmWave systems use a large number of antenna
elements both at the base station and at the user equipment, which lead to high
directivity gains, fully-directional communications, and possible noise-limited
operations. The fundamental differences between mmWave networks and traditional
ones challenge the classical design constraints, objectives, and available
degrees of freedom. This paper addresses the implications that highly
directional communication has on the design of an efficient medium access
control (MAC) layer. The paper discusses key MAC layer issues, such as
synchronization, random access, handover, channelization, interference
management, scheduling, and association. The paper provides an integrated view
on MAC layer issues for cellular networks, identifies new challenges and
tradeoffs, and provides novel insights and solution approaches.Comment: 21 pages, 9 figures, 2 tables, to appear in IEEE Transactions on
Communication