Goodbye, ALOHA!

©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.Peer ReviewedPostprint (author's final draft

TSCH 네트워크에서 충돌을 완화하기 위한 Timeslot 내 적응적 랜덤 Back-Off 전송

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2020. 8. 박세웅.Recently, as the market of Internet of Things (IoT) has been rapidly extending and developing, the research focusing on low-power wireless sensor networks has been actively ongoing. In particular, for the satisfaction of IoT requirements, many studies have been conducted using IEEE 802.15.4 TSCH (Time-Slotted Channel Hopping) based networks with characteristics of high reliability and low-power. Transmitter and receiver using TSCH can exchange the data through time-synchronized communication using timeslot. However, if multiple users transmit the packets on the same timeslot and channel in the TSCH network, severe data collisions may occur. In this paper, we propose Random Back-Off TSCH (RBO-TSCH) which helps to mitigate the collisions by proceeding a random back-off in the timeslot before transmission. In addition, to reduce the energy consumption of RBO-TSCH, we propose receiver-triggered RBO-TSCH which can adaptively control the number of a random back-off set at the receiver side. To verify this, we conduct extensive experiments and evaluate the RBOTSCH and receiver-triggered RBO-TSCH. Compared to TSCH, we demonstrate that RBO-TSCH and receiver-triggered RBO-TSCH demonstrate achieve up to 3.8 times higher reliability and have higher stability against collision in both link layer and routing layer.최근 사물 인터넷(Internet of Things) 시장의 발전이 급성장함에 따라 저 전력, 무선 센서 네트워크에 초점을 맞춘 연구가 활발히 진행되고 있다. 특히, IoT의 요구조건을 만족하기 위해 높은 신뢰도와 저 전력의 특징을 가지는 IEEE 802.15.4 TSCH (Time-Slotted Channel Hopping) 기반의 네트워크를 사용한 연구가 많이 이루어 지고 있다. TSCH를 사용하는 송신자와 수신자는 timeslot을 이용한 시간 동기화된 통신을 통하여 데이터를 교환한다. 그러나 TSCH 네트워크의 같은 timeslot과 채널에서 다자 간 전송이 일어나게 될 경우, 심각한 데이터 충돌이 발생하게 된다. 이에 따라, 본 논문에서는 timeslot 내에서 랜덤하게 back-off를 진행 후 전송하게 함으로써 충돌을 회피할 수 있게 하는 Random Back-Off TSCH (RBO-TSCH)를 제안하였다. 더하여, RBO-TSCH의 에너지 소비를 줄이기 위해 송신자가 랜덤 back-off set의 개수를 적응적으로 제어하는 receiver-triggered RBO-TSCH를 제안하였다. 이를 검증하기 위해, 여러 실험들을 수행하였으며, RBO-TSCH와 receiver-triggered RBO-TSCH를 평가하였다. TSCH와 비교하여, 두 기법이 최대 3.8배 높은 신뢰성을 가지며, 링크 계층과 라우팅 계층에서 모두 충돌에 대하여 더 높은 안정성을 가진다는 것을 증명하였다.1 Introduction 1 2 Backgrond 4 2.1 Time-Slotted Channel Hopping (TSCH) 4 2.2 Problem Statement 5 3 Random Back-Off TSCH (RBO-TSCH) 8 3.1 Design of RBO-TSCH 8 3.2 Consideration of RBO-TSCH 9 3.2.1 RBO SET 9 3.2.2 Clock Drift Correction 10 3.3 Weakness of RBO-TSCH 10 4 Receiver-triggered RBO-TSCH 12 4.1 Design of Receiver-Triggered RBO-TSCH 12 4.1.1 Operation of Increasing RBO SET 13 4.1.2 Operation of Decreasing RBO SET 14 5 Performance Evaluation 16 5.1 Experimental Setting 16 5.2 Communication Reliability 17 5.3 Radio Duty Cycle 18 5.4 Network Stability 19 6 Conclusion 22 6.1 Conclusion 22 Abstract (In Korean) 26Maste

LPDQ: a self-scheduled TDMA MAC protocol for one-hop dynamic lowpower wireless networks

Current Medium Access Control (MAC) protocols for data collection scenarios with a large number of nodes that generate bursty traffic are based on Low-Power Listening (LPL) for network synchronization and Frame Slotted ALOHA (FSA) as the channel access mechanism. However, FSA has an efficiency bounded to 36.8% due to contention effects, which reduces packet throughput and increases energy consumption. In this paper, we target such scenarios by presenting Low-Power Distributed Queuing (LPDQ), a highly efficient and low-power MAC protocol. LPDQ is able to self-schedule data transmissions, acting as a FSA MAC under light traffic and seamlessly converging to a Time Division Multiple Access (TDMA) MAC under congestion. The paper presents the design principles and the implementation details of LPDQ using low-power commercial radio transceivers. Experiments demonstrate an efficiency close to 99% that is independent of the number of nodes and is fair in terms of resource allocation.Peer ReviewedPostprint (author’s final draft

Towards efficient coexistence of IEEE 802.15.4e TSCH and IEEE 802.11

A major challenge in wide deployment of smart wireless devices, using different technologies and sharing the same 2.4 GHz spectrum, is to achieve coexistence across multiple technologies. The IEEE~802.11 (WLAN) and the IEEE 802.15.4e TSCH (WSN) where designed with different goals in mind and both play important roles for respective applications. However, they cause mutual interference and degraded performance while operating in the same space. To improve this situation we propose an approach to enable a cooperative control which type of network is transmitting at given time, frequency and place. We recognize that TSCH based sensor network is expected to occupy only small share of time, and that the nodes are by design tightly synchronized. We develop mechanism enabling over-the-air synchronization of the Wi-Fi network to the TSCH based sensor network. Finally, we show that Wi-Fi network can avoid transmitting in the "collision periods". We provide full design and show prototype implementation based on the Commercial off-the-shelf (COTS) devices. Our solution does not require changes in any of the standards.Comment: 8 page

A Case for Time Slotted Channel Hopping for ICN in the IoT

Recent proposals to simplify the operation of the IoT include the use of Information Centric Networking (ICN) paradigms. While this is promising, several challenges remain. In this paper, our core contributions (a) leverage ICN communication patterns to dynamically optimize the use of TSCH (Time Slotted Channel Hopping), a wireless link layer technology increasingly popular in the IoT, and (b) make IoT-style routing adaptive to names, resources, and traffic patterns throughout the network--both without cross-layering. Through a series of experiments on the FIT IoT-LAB interconnecting typical IoT hardware, we find that our approach is fully robust against wireless interference, and almost halves the energy consumed for transmission when compared to CSMA. Most importantly, our adaptive scheduling prevents the time-slotted MAC layer from sacrificing throughput and delay

Efficiency enhancement using optimized static scheduling technique in TSCH networks

In recent times, the reliable and real-time data transmission becomes a mandatory requirement for various industries and organizations due to the large utilization of Internet of Things (IoT) devices. However, the IoT devices need high reliability, precise data exchange and low power utilization which cannot be achieved by the conventional Medium Access Control (MAC) protocols due to link failures and high interferences in the network. Therefore, the Time-Slotted Channel Hopping (TSCH) networks can be used for link scheduling under the IEEE 802.15.4e standard. In this paper, we propose an Optimized Static Scheduling Technique (OSST) for the link scheduling in IEEE 802.15.4e based TSCH networks. In OSST the link schedule is optimized by considering the packet latency information during transmission by checking the status of the transmitted packets as well as keeping track of the lost data packets from source to destination nodes. We evaluate the proposed OSST model using 6TiSCH Simulator and compare the different performance metrics with Simple distributed TSCH Scheduling

QF-MAC: Adaptive, Local Channel Hopping for Interference Avoidance in Wireless Meshes

The throughput efficiency of a wireless mesh network with potentially malicious external or internal interference can be significantly improved by equipping routers with multi-radio access over multiple channels. For reliably mitigating the effect of interference, frequency diversity (e.g., channel hopping) and time diversity (e.g., carrier sense multiple access) are conventionally leveraged to schedule communication channels. However, multi-radio scheduling over a limited set of channels to minimize the effect of interference and maximize network performance in the presence of concurrent network flows remains a challenging problem. The state-of-the-practice in channel scheduling of multi-radios reveals not only gaps in achieving network capacity but also significant communication overhead. This paper proposes an adaptive channel hopping algorithm for multi-radio communication, QuickFire MAC (QF-MAC), that assigns per-node, per-flow ``local'' channel hopping sequences, using only one-hop neighborhood coordination. QF-MAC achieves a substantial enhancement of throughput and latency with low control overhead. QF-MAC also achieves robustness against network dynamics, i.e., mobility and external interference, and selective jamming attacker where a global channel hopping sequence (e.g., TSCH) fails to sustain the communication performance. Our simulation results quantify the performance gains of QF-MAC in terms of goodput, latency, reliability, communication overhead, and jamming tolerance, both in the presence and absence of mobility, across diverse configurations of network densities, sizes, and concurrent flows

Statistical Delay Bound for WirelessHART Networks

In this paper we provide a performance analysis framework for wireless industrial networks by deriving a service curve and a bound on the delay violation probability. For this purpose we use the (min,x) stochastic network calculus as well as a recently presented recursive formula for an end-to-end delay bound of wireless heterogeneous networks. The derived results are mapped to WirelessHART networks used in process automation and were validated via simulations. In addition to WirelessHART, our results can be applied to any wireless network whose physical layer conforms the IEEE 802.15.4 standard, while its MAC protocol incorporates TDMA and channel hopping, like e.g. ISA100.11a or TSCH-based networks. The provided delay analysis is especially useful during the network design phase, offering further research potential towards optimal routing and power management in QoS-constrained wireless industrial networks.Comment: Accepted at PE-WASUN 201

Performance Evaluation of Impluse Radio Ultra Wide Band Wireless Sensor Networks

This paper presents a performance evaluation of Wireless Sensor Networks (WSN) based on Impulse Radio Ultra Wideband (IR-UWB) over a new simulation platform developed for this purpose. The simulation platform is built on an existing network simulator: Global Mobile Information System Simulator (GloMoSim). It mainly focuses on the accurately modeling of IR-UWB PHYsical (PHY) and Medium Access Control (MAC) layer. Pulse collision is modeled according to the used time hopping sequence (THS) and the pulse propagation delay in order to increase the simulation fidelity. It also includes a detection and identification application based on a new sensing channel and new sensor device models. The proposed architecture is generic so it can be reused for any simulation platform. The performance evaluation is based on one of the typical WSN applications: local area protection, where sensor nodes are densely scattered in an access regulated area in order to detect, identify and report non authorized accesses to a base station for analysis. Two networks topologies using different protocol stacks are investigated. Their performance evaluation is presented in terms of reliability and latency