technology from seed End-to-End Reliability in WSNs: Survey and Research Challenges Authors: Paulo Pereira, António Grilo, Francisco Rocha, Mário Serafim Nunes, Augusto Casaca (Inesc- ID, Protugal), Claude Chaudet (GET, France), Peter Almstrom and Mikael Johansson (KTH, Sweden). Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 1 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Summary technology from seed • Introduction • Routing Protocols • Transport Protocols • Conclusions and Further Work Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 2 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Summary technology from seed • Introduction • Routing Protocols • Transport Protocols • Conclusions and Further Work Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 3 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Wireless Sensor Networks (WSNs): technology from seed Basic concepts • WSNs constitute a particular class of ad-hoc nets. • WSN nodes are usually static, organized in a tree topology. • WSNs may comprise hundreds or thousands of nodes. • WSN nodes are designed to be low-cost. • WSN nodes have limited energy, memory and processing capacity. • WSN nodes usually have to sleep most of the time. • WSN communications: 433, 868/916, 310 MHz, 2.4 GHz (IEEE 802.15.4/ZigBee), acoustic Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 4 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Mobile Ad-hoc Networks (MANETs) vs technology from seed WSNs • Similarities: Self-organized, energy efficiency, wireless multi-hop. • Differences: – MANETs aim at user communication while WSNs aim at interactions with the environment. – MANETs have usually more resources than WSNs. – WSNs are more application specific. – WSN might comprise an higher number of nodes. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 5 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
End-to-End Reliability in WSNs technology from seed • Why do we need end-to-end reliability? – To make the system trusted and to support safety critical applications. • Intrusion and hazard detection. • Road Services: detection of obstacles on the roadway. – To support bulk data applications. • Imaging/sound sensors: data segmentation and reassembly. – To support reprogramming and network management operations. • For example, Dynamic Code Update (DCU) and sensor retasking. – Packet-driven reliability vs Event-driven reliability Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 6 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Summary technology from seed • Introduction • Routing Protocols • Transport Protocols • Conclusions and Further Work Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 7 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
MANETs Routing Protocols and WSNs technology from seed • The similarities between the two types of networks make us consider the application of MANETs routing protocols to WSNs. – Protocols like OLSR, AODV and DSDV. • Utilization is conditioned by WSNs resource constraints. • The protocols bandwidth, memory and energy requirements are usually too demanding for WSNs. • Solution: Design specific routing protocols for WSNs. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 8 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
WSNs routing protocols technology from seed • Data-centric protocols: – Gossiping, Sensor Protocol for Information via Negotiation (SPIN) and Directed Diffusion. • Hierarchical protocols: – Low-Energy Adaptive Clustering Hierarchy (LEACH). • Location based (geographic) protocols: – Greedy Perimeter Stateless Routing (GPSR). Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 9 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Summary technology from seed • Introduction • Routing Protocols • Transport Protocols • Conclusions and Further Work Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 10 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Traditional Transport Protocols and technology from seed WSNs • UDP and TCP can not be directly applied to WSNs. • UDP – Does not provides any reliability – No flow or congestion control • TCP – Overhead associated with TCP connection establishment. – Flow and congestion control mechanisms. – Degraded throughput under wireless systems espically with a high packet loss rate. – End-to-end congestion control. – End-to-end retransmission. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 11 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Distributed TCP Caching (DTC) (1) technology from seed • TCP enhancement to make it more efficient in WSNs. • Keep TCP/IP in WSNs to enable direct connection with external TCP/IP networks. • Best-effort UDP – event-driven applications; Reliable byte- stream TCP – packet-driven applications. • TCP header compression, caching at intermediate nodes and energy consumption fairness. • Uses TCP loss recovery mechanisms. • Flying start to find an initial estimate of the round-trip time (RTT). Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 12 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Distributed TCP Caching (DTC) (2) technology from seed • They keep the TCP connection set-up. – Energy consumption. • The transmission of ACKs is totally controlled by the receiver. – Excessive ACKs � Energy consumption. • No support for video and audio data. • If the SACK option is used the overhead is significant. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 13 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Reliable Multi-Segment Transport technology from seed (RMST) • Designed to work on top of Directed Diffusion. • It offers two services: data segmentation/reassembly and guaranteed delivery. • Can operate in two modes: end-to-end or store-and- forward. • Can use caching at intermediate nodes. � No full guarantee of delivery. � It only uses negative acknowledgements (NACKs). � It has no positive end-to-end ACK. � No congestion control mechanism. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 14 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Pump Slowly Fetch Quickly (PSFQ) (1) technology from seed • Designed to offer downstream multicast guaranteed delivery of dynamic code update (DCU). – Losses are not tolerable, delay not critical • Source pumps data into the network. – Using broadcast, large inter-packet gap time • Intermediate nodes store packets, forward if in-sequence. • Out-of-sequence: request missing packet(s) – fetch operation (negative acknowledgement). – Previous node resends missing packet - local recovery. – Assumption: packet is available - no congestion, only channel errors. • Pumping is slow, fetch is quick Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 15 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Pump Slowly Fetch Quickly (PSFQ) (2) technology from seed • Inter-packet gaps are big enough to accomodate several fetch operations. • The probability of an out-of-order event should be small. – When they happen, do not forward, fill the gap first by fetching, this avoids loss propagation. • Fetch requests are broadcast. • Nodes receiving NACK might not have all requested packets. • Use a slotted resend mechanism for requested packets. � No full guarantee of delivery like RMST. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 16 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
Distributed Transport for Sensor technology from seed Networks (DTSN) • It offers total reliability and differentiated reliability (under study). • Loss recovery mechanism – positive and negative acknowledgement and explicit acknowledgement request. • NACK uses a bitmap to indicate lost packets. • Soft-state session between source/destination, univocally identified by the tuple < source address, destination address, application identifier, session number>. • Acknowledgement Window (AW) to control the number of confirmation requests (Explicit Acknowledgement Request - EAR). • Caching and generation of ACKs at intermediate nodes. Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa 17 End-to-End Reliability in WSNs: Survey and Research Challenges 09-12-2007
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