Beacon Slot Research Articles

A Beacon and GTS Scheduling Scheme for IEEE 802.15.4 DSME Networks

The IEEE 802.15.4 standard is one of the widely adopted networking specification for realizing different applications of Internet of Things (IoT). It defines several physical layer options and Medium Access Control (MAC) sub-layer protocols for low-power devices supporting low-data rates. One such MAC protocol is the Deterministic and Synchronous Multi-channel Extension (DSME), which addresses the limitation on maximum number of Guaranteed Time Slots (GTSs) in 802.15.4-2011 MAC, and provides channel diversity to increase network robustness. However, beacon scheduling in peer-to-peer networks suffers from beacon slot-collisions when two or more coordinators simultaneously compete for the same vacant beacon slot. In addition, the standard does not explore DSME-GTS scheduling across multiple channels. This paper addresses the beacon slot collision problem by proposing a non-conflicting beacon scheduling mechanism using association order. Further, a distributed multi-channel DSME-GTS schedule is proposed that optimally assigns DSME-GTSs across different channels. The objective is to minimize the number of times-lots used while maximizing the usage of available channels. Through simulations, the proposed mechanisms’ performance is analyzed in terms of energy efficiency, transmission overhead, scheduling efficiency, throughput, and latency and is shown to out-perform the other existing schemes.

A Contention Delay Minimization Scheme in WiMedia Networks

Ultra wideband (UWB) technology has emerged as a solution for the wireless interface between medical sensors and a personal server in future telemedicine systems. The WiMedia Alliance has specified a distributed medium access control protocol based on UWB for high-rate WPANs. Because WiMedia devices transmit data frames using CSMA/CA in PCA duration, waste of time slot interval occurs by collision, and data transmission and the overall throughput is decreased. Therefore, we propose medium access scheme to improve conflict and channel waste and to minimize contention by using own beacon slot number and neighbor's beacon slot number. Simulation results have shown that the proposed scheme has excellent performance in terms of throughput, delay, jitter, and fairness.

Automatic Beacon Period Contraction for Energy Efficient WiMedia MAC

The basic timing structure for data exchange in WiMedia UWB MAC is a superframe composed of beacon period and data transfer period. When a new device joins the WiMedia UWB based network, the device has to send a beacon in a randomly selected beacon slot in the beacon period. Accordingly, when devices join or leave the WiMedia based network, they may result in idle beacon slots in the beacon period. The idle beacon slots should be removed to spare more time resources to the data transfer period, since no data exchange is permitted during the beacon period. This paper proposes an automatic beacon period contraction scheme which has objective of minimizing the waste of wireless resource in WiMedia UWB based home networks. The proposed method compresses the beacon period in a simpler and faster way than the conventional beacon period contraction algorithm defined in WiMedia MAC standard. Performance evaluation by computer simulation shows that the proposed scheme improves wireless channel utilization efficiency. The results of this paper can be applied to design and implementation of WiMedia MAC with small overhead for UWB applications.

An Urn Occupancy Approach for Modeling the Energy Consumption of Distributed Beaconing

In past years, ultrawideband technology has attracted great attention from academia and industry for wireless personal area networks and wireless sensor networks. Maintenance of connectivity and exchange of data require an efficient way to manage the devices. Distributed beaconing defined by ECMA-368 is used to manage the network in fully distributed fashion. All the devices must acquire a unique beacon slot, with the beacon period accessed using a slotted Aloha scheme. In this paper, we study the efficiency of distributed beaconing in the presence of $k$ newcomer devices forming a closed system. Efficiency is measured in terms of energy consumption and network setup delay. ECMA-368 defines two distinct phases: extension and contraction. Both phases are analyzed with particular emphasis on the extension phase by means of an absorbing Markov chain model. The main contributions of this paper are: 1) a systematic approach to model distributed beaconing by formulating two equivalent urn occupancy problems of the extension and contraction phases; 2) the use of exponential generating functions to obtain closed-form expressions of the transition probabilities of the absorbing Markov chain; and 3) comparison to computer simulations based on Opnet modeling and with the preexisting literature.

Risk-Aware Distributed Beacon Scheduling for Tree-Based ZigBee Wireless Networks

In a tree-based ZigBee network, ZigBee routers (ZRs) must schedule their beacon transmission time to avoid beacon collisions. The beacon schedule determines packet delivery latency from the end devices to the ZigBee coordinator at the root of the tree. Traditionally, beacon schedules are chosen such that a ZR does not reuse the beacon slots already claimed by its neighbors, or the neighbors of its neighbors. We observe, however, that beacon slots can be reused judiciously, especially when the risk of beacon collision caused by such reuse is low. The advantage of such reuse is that packet delivery latency can be reduced. We formalize our observation by proposing a node-pair classification scheme. Based on this scheme, we can easily assess the risk of slot reuse by a node pair. If the risk is high, slot reuse is disallowed; otherwise, slot reuse is allowed. This forms the essence of our ZigBee-compatible, distributed, risk-aware, probabilistic beacon scheduling algorithm. Simulation results show that on average the proposed algorithm produces a latency only 24 percent of that with conventional method, at the cost of 12 percent reduction in the fraction of associated nodes.