Understanding Link Dynamics in Wireless Sensor Networks with Dynamically Steerable Directional Antennas

Abstract

Abstract. By radiating the power in the direction of choice, electronicallyswitched directional (ESD) antennas can reduce network contention and avoid packet loss. There exists some ESD antennas for wireless sensor networks, but so far researchers have mainly evaluated their directionality. There are no studies regarding the link dynamics of ESD antennas, in particular not for indoor deployments and other scenarios where nodes are not necessarily in line of sight. Our long-term experiments confirm that previous findings that have demonstrated the dependence of angleof-arrival on channel frequency also hold for directional transmissions with ESD antennas. This is important for the design of protocols for wireless sensor networks with ESD antennas: the best antenna direction, i.e., the direction that leads to the highest packet reception rate and signal strength at the receiver, is not stable but varies over time and with the selected IEEE 802.15.4 channel. As this requires protocols to incorporate some form of adaptation, we present an intentionally simple and yet efficient mechanism for selecting the best antenna direction at run-time with an energy overhead below 2% compared to standard omni-directional transmissions.

Review on directional antenna for wireless sensor network applications

“…To avoid the loss of packets and to minimise the contention of the network, electronically switched directional (ESD) antennas are proposed by Voigt et al [46] by radiating in the direction of choice. For WSNs, already there are some ESD antennas; but in this research, the authors have estimated the directionality, link dynamics.…”

Enabling space time division multiple access in IETF 6TiSCH protocol

“…proposed an efficient mechanism that selects the best antenna for communication with the neighbor node based on the received signal strength indicator (RSSI) value of the received packets for each antenna [13]. While using RSSI for selecting the correct antenna direction can create a high performance solution in a wireless network with line of sight communication paths, this observation may not hold when the propagation medium is not line of sight as discussed in [14].…”

Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks

“…Using CC2420 radios, Tc is found to be around 3 dB for single transmissions, which equals the co-channel interference tolerance level of the radio chip [6]. However, RSSI values may vary over time also with directional antennas [45]. Setting Tc exactly to 3 dB when computing the conflict graph-which must remain valid for the duration of the bulk transfer-might lead to packet corruption, as the RSSI values of concurrent transmissions may temporarily fall below the radio's co-channel interference tolerance level.…”