openDSME: Reliable Time-Slotted Multi-Hop Communication for IEEE 802.15.4
Using wireless sensor and actuator networks in industrial applications promises timely and fine-grained feedback and control of plants. However, these applications call for very high reliability that cannot be fulfilled with contention-based medium access
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openDSME: Reliable Time-Slotted Multi-Hop Communication for IEEE 802.15.4 Florian Kauer, Maximilian Köstler, and Volker Turau
15.1 Medium Access in Wireless Multi-Hop Networks Industrial applications of wireless networks call for high reliability, even under the influence of high traffic load or external interference. This requirement is hard to fulfill with conventional radio technology like IEEE 802.15.4 [7] which is primarily used to build energy-efficient multi-hop networks to connect sensors and actuators. One of the main causes is the use of contention-based medium access such as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). With CSMA/CA, the medium is sensed for an ongoing transmission and a transmission only takes place when no concurrent transmission is detected. Carrier sensing is, however, unreliable in multi-hop networks, especially in hidden node situations as depicted in Fig. 15.1 where a disturbing transmission cannot be sensed by another transmitter. This leads to collision of transmissions and thereby to packet loss. Several mechanisms, such as random backoff and retransmissions, are available to lower the probability of packet loss, but they cannot solve the fundamental problem. Also, slotted CSMA/CA is suggested to minimize overlapping transmissions, but the expectations have not been met [18]. The influence of the hidden node problem on the performance is analyzed, for instance, in [15]. A more in-depth analytical analysis that also takes the simultaneous retransmission problem into account is available in [14]. A different approach for medium access is Time Division Multiple Access (TDMA). For this, the time domain is divided into slots and it is negotiated beforehand which node shall be allowed to transmit when. If this is done correctly, no
F. Kauer () · M. Köstler · V. Turau Institute of Telematics, Hamburg University of Technology, Hamburg, Germany e-mail: [email protected]; [email protected]; [email protected] © Springer Nature Switzerland AG 2019 A. Virdis, M. Kirsche (eds.), Recent Advances in Network Simulation, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-12842-5_15
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Fig. 15.1 Hidden node problem
collisions between node transmissions are possible in the network. However, even if a properly constructed TDMA approach is safe against packet collisions within the same network, transmissions by other transmitters, e.g., IEEE 802.11 access points, could disturb the network. Therefore, it is also advised to utilize multiple frequency channels to sidestep external interferences, which are called Frequency Division Multiple Access (FDMA). Both approaches are the basis for two amendments of the IEEE 802.15.4 standard described in [6], namely, Time-Slotted Channel Hopping (TSCH) and the Deterministic and Synchronous Multi-Channel Extension (DSME), which were later integrated into the 2015 revision of the standard [7]. Starting from the 2011 standard edition [5], time synchronizat
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