Self-stabilizing TDMA Algorithms for Wireless Ad-Hoc Networks without External Reference

Abstract

Time division multiple access (TDMA) is a method for sharing communication media. In wireless communications, TDMA algorithms often divide the radio time into timeslots of uniform size, ξ, and then combine them into frames of uniform size, τ . We consider TDMA algorithms that allocate at least one timeslot in every frame to every node. Given a maximal node degree, δ, and no access to external references for collision detection, time or position, we consider the problem of collision-free self-stabilizing TDMA algorithms that use constant frame size.We demonstrate that this problem has no solution when the frame size is τ < max{2δ, χ2}, where χ2 is the chromatic number for distance-2 vertex coloring. As a complement to this lower bound, we focus on proving the existence of collision-free self-stabilizing TDMA algorithms that use constant frame size of τ . We consider basic settings (no hardware support for collision detection and no prior clock synchronization), and the collision of concurrent transmissions from transmitters that are at most two hops apart. In the context of self-stabilizing systems that have no external reference, we are the first to study this problem (to the best of our knowledge), and use simulations to show convergence even with computation time uncertainties.

A kernel-based architecture for safe cooperative vehicular functions

“…Vehicles exchange their localization information, and use that for discovering the location of all nearby nodes. We control the access of these radio units using protocols that appears in [12]- [15], [19]. The position database contains position estimation for all vehicles from which sensor data has been received.…”

DecTDMA: A Decentralized-TDMA

“…DecTDMA extends this, by utilizing an LQE technique for masking sporadic packet loss. Thus, DecTDMA considers fewer occurrences of sporadic packet loss as transient faults than the TDMA algorithm by Petig et al [2]. As a result, DecTDMA avoids unnecessary recovery periods.…”

“…For example, they can reduce the packet reception ratio (PRR) [1]. DecTDMA uses a self-stabilizing algorithm [2] for time division multiple access (TDMA) that significantly reduces the occurrence of concurrent transmissions. In addition, we show that DecTDMA deals well with other causes of WSN dynamics, such as mote or link failure and wireless links of intermediate quality, i.e., links with a PRR between 10% and 90%.…”

“…Transient faults can also represent temporary violations of the assumptions according to which the communication links and the entire dynamic networks behaves during normal operation. In order to provide DecTDMA with properties of self-organization and self-recovery, we base the implementation of DecTDMA on an existing selfstabilizing TDMA algorithm [2]. This algorithm helps DecTDMA to significantly reduce the occurrence of concurrent transmissions.…”

“…This algorithm helps DecTDMA to significantly reduce the occurrence of concurrent transmissions. We note that the design of the TDMA algorithm in [2] focuses on packet loss due to concurrent transmissions and models all other kinds of packet loss as transient faults (after which a brief recovery period is needed). DecTDMA extends this, by utilizing an LQE technique for masking sporadic packet loss.…”