Description of the deliverable content and purpose
The goal of WP3 is to combine highly optimised, energy efficient physical layer technologies with cross-layer optimised and designed protocols from the physical to the transport layer.
We have first developed methodologies for optimising existing physical layer technologies for use in wireless sensor networks in T3.1. Advanced RF sensing techniques have been designed to support context and situation awareness e.g. to estimate nodes relative distance and for monitoring and measuring the quality of available radio links. Hardware validation of these physical layer techniques is being performed to illustrate the advancements in terms of energy efficiency.
In order to seek for system efficiency, our approach relies on cross-layer design to build an energy-efficient, integrated and cross layer optimised protocol stack made of protocol elements studied in T3.2. Cross-layer information related to the radio channel conditions, node mobility, relative position and relative time synchronisation of the nodes (an issue addressed by WP4) are extensively used to optimise the performance of the different layers of the protocols stack. Our objective is to build highly efficient communication profiles for air interfaces and to provide a low energy consuming, reliable communication service to the applications considered in e-SENSE and elsewhere.
This deliverable summarizes the results of the activities on cross-layer design performed in the first five quarters of the e-SENSE project. The structure of this deliverable, tailored to the structure of the e-SENSE architecture as proposed in WP2 D2.2.1 is as follows. After an introduction given in Section 2 - , Section 3 - is related to the connectivity subsystem and consists of three subsections (PHY/MAC, MAC/Routing, MAC/Transport). Section 4 - is related to the management subsystem and has two subsections (Self-organisation and topology control, Mobility management). Finally, Section 5 - draws conclusions on the activities performed, outlining the major issues that will be considered in the second half of the project.
In the following we briefly discuss the major contributions reported in each of the deliverable technical subsections.
Section 3.1
Section 3.1 deals with PHY/MAC layer codesign. It includes models to capture the packet error rate performance of two possible implementations of the IEEE 802.15.4. Also detailed energy models for these two transceivers are provided, together with a list of link quality metrics that can be exposed to the upper layers and used for sake of cross-layer design.
It also comprises two studies on short range UWB transceivers: one sticking to the IEEE 802.15.4a standard and giving useful performances for two kinds of receivers in typical short range applications, the other being more tailored to BSN applications and giving performances for such a propagation channel. A synchronization approach suited to ultralow-power UWB-IR transceivers, targeting a minimal preamble length and low-complexity devices has been developed. An analytical framework for modelling UWB PHYs in the presence of interferers is also given and is useful for further PHY-MAC codesign as initiated already in T3.2 and deliverable D3.2.1.
The work reported in Section 3.1 poses the basis for cross-layer design spanning the whole protocol stack. The provided models will be included in the e-SENSE simulation framework and will be used to achieve an accurate evaluation of the performance of the developed protocol stack. They will also be used, together with the information on PHY layer metrics that can be exposed at the upper layers, for PHY/MAC-and higher- cross layer design.
Section 3.2
In Section 3.2, First cross-layer solutions for converge casting packets from the sensor nodes to the sink are presented. Such schemes include awake-asleep schedule, energyefficient MAC, routing, as well as mechanisms to enable reliable communications or to deal with network congestion. Three complete protocol stacks have already been designed and are under evaluation: ALBA (a geographic routing based cross-layer design which include a pioneering solution to solve the dead end problem), IRIS (which integrates converge-casting and interest dissemination, providing a solution which comprises MAC and routing layers for both) and RoCoDiLe (which exploits cooperative relaying, MAC and routing design to provide a reliable and efficient solution for converge casting in WSN). In addition to these protocol stacks, work has been performed on energy-efficient schemes for sink to sensors communications. This is indeed an important topic both for sake of interest dissemination and for being able to program/reprogram the sensor nodes (which requires primitives for bulk data dissemination to the sensor nodes). Most of these protocol stacks are adapted to ESN.
Section 3.3
Section 3.3 is instead related to MAC/transport layer optimization. A link adaptive transport protocol (LATP) based on MAC and network layer feedback information is proposed. MAC and network layer feedback is exploited to determine the end-to-end rate for application at the transport. The proposed solution is based on a cross layer approach and especially focuses on optimising end-to-end delay and jitter for A/V streaming applications in outdoor ESN.
Section 4.1
Section 4.1 describes topology-control and self-organization methods which are among the key requirements of wireless sensor networks. In the e-SENSE context, whenever it is invoked, self-organization is realized by organizing a sensor network into clusters where a connected dominant set (CDS) is formed by the cluster-heads. These techniques benefit the applications where a large number of sensor nodes may be deployed, such as smart farm, smart storage and smart factory introduced in D1.3.1.
Section 4.2
Section 4.2 focuses on how to support mobility in wireless sensor networks and especially on the mobile gateway in e-SENSE scenarios and in the e-SENSE architecture. The objective of the mobile gateway scenario is to investigate the impact of mobility information in the gateway for cross layer optimisation. It introduces a mobility information model which is part of the shared information base. In addition a mobility manager is introduced to handle mobility in conjunction with the information model. Then the information model is exploited in the design of the sleep schedule of sensors and in the routing algorithms.
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