Time-Driven Access and Forwarding for Industrial Wireless Multihop Networks

Abstract

The deployment of wireless technologies in industrial networks is very promising mainly due to their inherent flexibility. However, current wireless solutions lack the capability to provide the deterministic, low delay service required by many industrial applications. Moreover, the high level of interference generated by industrial equipment limits the coverage that ensures acceptable performance. Multi-hop solutions, when combining frame forwarding with higher node density, have the potential to provide the needed coverage while keeping radio communication range short. However, in multi-hop solutions the medium access time at each of the nodes traversed additively contributes to the end-to-end delay and the forwarding delay (i.e., the time required for packets to be processed, switched, and queued) at each node is to be added as well. This paper describes Time-driven Access and Forwarding (TAF), a solution for guaranteeing deterministic delay, at both the access and forwarding level, in wireless multi-hop networks, analyzes its properties, and assesses its performance in industrial scenarios.

Prototyping of time-division unbalanced carrier sense multiple access and first experiments

“…As a result of TDuCSMA operating principles, a node i is very likely to gain access to the channel and maintain it for the full period T i H . It worth noting that this happens due to CSMA/CA operations and the values of the access parameters in EDCA H and not because of a predefined channel access as in TDMA based solutions 1 .…”

“…In TDMA based networks, nodes access the network at well defined instants, thus avoiding contentions and collisions. This approach is successfully adopted in [1], [2] where the limitation due to a centralized coordination function is also overcome and reservation is managed in a distributed fashion. However such solutions still suffer from the intrinsic stiffness of a reservation mechanism which hardly copes with rapidly changing traffic profiles; additionally they require extensions to the standardized MAC layer that are very likely to increase time-to-market and make a wide deployment difficult.…”

Minimum delay switch for Synchronous TDMA network

“…A similar approach has been proposed and implemented for wireless network. Time-driven access and forwarding (TAF) [14] is based on the concept of PF [15]. TAF can guarantee deterministic endto-end delay in industrial wireless multihop networks.…”

Scheduling for Source Relaying With Packet Aggregation in Industrial Wireless Networks

“…In this paper we show that packet aggregation, when combined with source-based relaying, can furthermore help to save time slots that otherwise would be required for retransmissions. As with any other packet forwarding technique, a specific scheduling scheme ensuring deterministic end-to-end delay is required to allocate the time slots [18]. Since every node is allowed to do packet aggregation, it is important for the overall performance of the system that most nodes actually are able to use the opportunity to aggregate.…”