IACR: an interference-aware channel reservation for wireless sensor networks

In battery-based wireless sensor networks, energy-efficient operation is one of the most important factors. Especially, in order to improve energy efficiency in wireless sensor networks, various studies on low power operation have been actively conducted in the MAC layer. In recent years, mutual interference among various radio technologies using the same radio frequency band has become a serious problem. Wi-Fi, ZigBee, and Bluetooth use the same frequency band of 2.4GHz at the same time, which causes various signal interference problems. In this paper, we propose a novel channel reservation scheme, called IACR, to improve the energy efficiency of wireless sensor networks in an environment where interference occurs between various wireless technologies. The proposed scheme inserts a PN code into a long preamble for exchanging transmission status information between a transmitting node and a receiving node, thereby improving the transmission success probability while receiving less influence on transmission of other radio technologies. We performed an event-driven simulation and an experiment to measure the signal detection rate. As a result, it can be seen that the proposed technique reduces the packet drop rate by 15% and increases the discoverable distance of the control packet for channel reservation

이기종 무선 네트워크에서의 협대역 시스템 보호 기법

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 김종권.최근 다양한 무선 네트워크 기술들(와이파이, 블루투스, 지그비)이 2.4GHz 대역의 ISM 밴드에 공존함으로 인하여 이들 간의 상호공존이 큰 문제로 나타나고있다. 특히 지그비 네트워크는 현저히 높은 전송 파워로 통신하는 와이파이 네트워크가 동일한 주파수 대역에 존재할 때 통신이 불가능해 질 정도의 심각한 성능 저하를 겪게 된다. 본 논문에서는 지그비 네트워크의 통신을 와이파이 네트워크의 간섭으로 부터 보호할 수 있는 좁은 대역 보호 방법(Narrow Band Protection)을 제안한다. 자가 감지 보호자는 좁은 대역 보호 방법의 핵심 기술로 사전에 정의된 PN 시퀀스에 대해 상호 상관 기법을 이용하여 스스로 지그비 패킷을 발견할 수 있어 최소한의 오버헤드로 지그비 네트워크를 보호할 수 있다. 또한, 자가 감지 보호자는 신뢰성 있는 상호 상관 기법을 통해 기존 방법에서 발생하는 제어 패킷 손실로 인한 두 네트워크의 이용효율 감소를 대폭 줄일 수 있다. 마지막으로, 시맨틱이 부여된 PN 코드북을 통해 저전력 동작을 수행하는 지그비 네트워크의 다량 패킷 전송을 효율적으로 감지하여 지그비 네트워크의 높은 처리량을 지원해 줄 수 있는 장점이 있다. 제안하고 있는 자가 감지 보호자는 시맨틱이 부여된 PN 시퀀스를 지그비 패킷의 프리앰블(Preamble) 앞에 임베딩 하는 기법을 사용한다. 이는 해당 기법을 적용하지 않는 지그비 노드들의 동기화를 방해하지 않는다. 즉, 좁은 대역 보호 방법은 기존 지그비 네트워크와 하위 호환성(backward compatibility)을 유지하며 기존 방법에 비해 단일 패킷에 대해서 1.77배 가량 높은 처리량을 제공해 줄 수 있으며, 다량 패킷 전송 보호시 보호하는 패킷의 수가 증가함에 따라 선형으로 이득이 증가하게 된다. 또한, 실제 USRP/GNURadio 플랫폼에 핵심 기능을 구현하여 실효성을 입증하였으며, 수학적인 분석과 확장된 NS-2 시뮬레이션을 통해 다양한 시각에서 상호공존 문제를 해석하고 있어 향 후 관련 분야에 큰 기여를 할 연구이다.Recent deployment of various wireless technologies such as Wi-Fi, Bluetooth, and ZigBee in the 2.4GHz ISM band has led to the heterogeneous devices coexistence problem. The coexistence problem is particularly challenging since wireless technologies use different PHY/MAC specifications. This thesis deals with the ZigBee and Wi-Fi coexistence problem where a less capable ZigBee device may often experience unacceptably low throughput due to the interference from a powerful Wi-Fi device. We propose a novel time reservation scheme called Narrow Band Protection (NBP) that uses a protector to guard ongoing ZigBee transmissions. The NBP protector detects a ZigBee transmission by cross-correlating the ZigBee signals with pre-defined Pseudo-random Noise (PN) sequences. A cross-correlation, designed for apprehending certain patterns in signals, not only reduces the control overhead but also guarantees robustness against collisions. In addition, a ZigBee node can still encode its packet length as a PN sequence such that the protector guards a proper length of channel time. We show the feasibility of NBP by implementing it on the USRP/GNURadio platform. We also evaluate the performance of NBP through mathematical analysis and NS-2 simulations. The results show that NBP enhances the ZigBee throughput by up to 1.77x compared to an existing scheme.1 Introduction 1.1 Background 1.2 Goal and Contribution 1.3 Thesis Organization 2 Related Work 2.1 The Cross-technology Interference Problem 2.2 The Cross-technology Interference Solutions 2.3 Signal Correlation 3 Motivation 3.1 Overview of ZigBee and Wi-Fi 3.2 Collision between ZigBee and Wi-Fi packets 3.3 The Limitation of the Protector Approach 4 A Narrow Band Protection Technique 4.1 Overview 4.2 Cross-correlation with PN Codebook 4.3 Protection Coverage 4.4 Protecting Wireless Sensor Networks 4.5 Security Issues 4.6 Discussions 5 Mathematical Analysis 5.1 Assumptions and Notations 5.2 Collision Probability 5.3 Network Performance 5.4 Multiple Packet Transmissions 6 Performance Evaluation 6.1 USRP Experiments 6.2 NS-2 Simulations 7 Conclusion BibliographyDocto

JAG: Reliable and Predictable Wireless Agreement under External Radio Interference

Wireless low-power transceivers used in sensor networks typically operate in unlicensed frequency bands that are subject to external radio interference caused by devices transmitting at much higher power.communication protocols should therefore be designed to be robust against such interference. A critical building block of many protocols at all layers is agreement on a piece of information among a set of nodes. At the MAC layer, nodes may need to agree on a new time slot or frequency channel, at the application layer nodes may need to agree on handing over a leader role from one node to another. Message loss caused by interference may break agreement in two different ways: none of the nodes uses the new information (time slot, channel, leader) and sticks with the previous assignment, or-even worse-some nodes use the new information and some do not. This may lead to reduced performance or failures. In this paper, we investigate the problem of agreement under external radio interference and point out the limitations of traditional message-based approaches. We propose JAG, a novel protocol that uses jamming instead of message transmissions to make sure that two neighbouring nodes agree, and show that it outperforms message-based approaches in terms of agreement probability, energy consumption, and time-to-completion. We further show that JAG can be used to obtain performance guarantees and meet the requirements of applications with real-time constraints.CONETReSens

Wireless Sensor Networking in Challenging Environments

Recent years have witnessed growing interest in deploying wireless sensing applications in real-world environments. For example, home automation systems provide fine-grained metering and control of home appliances in residential settings. Similarly, assisted living applications employ wireless sensors to provide continuous health and wellness monitoring in homes. However, real deployments of Wireless Sensor Networks (WSNs) pose significant challenges due to their low-power radios and uncontrolled ambient environments. Our empirical study in over 15 real-world apartments shows that low-power WSNs based on the IEEE 802.15.4 standard are highly susceptible to external interference beyond user control, such as Wi-Fi access points, Bluetooth peripherals, cordless phones, and numerous other devices prevalent in residential environments that share the unlicensed 2.4 GHz ISM band with IEEE 802.15.4 radios. To address these real-world challenges, we developed two practical wireless network protocols including the Adaptive and Robust Channel Hopping (ARCH) protocol and the Adaptive Energy Detection Protocol (AEDP). ARCH enhances network reliability through opportunistically changing radio\u27s frequency to avoid interference and environmental noise and AEDP reduces false wakeups in noisy wireless environments by dynamically adjusting the wakeup threshold of low-power radios. Another major trend in WSNs is the convergence with smart phones. To deal with the dynamic wireless conditions and varying application requirements of mobile users, we developed the Self-Adapting MAC Layer (SAML) to support adaptive communication between smart phones and wireless sensors. SAML dynamically selects and switches Medium Access Control protocols to accommodate changes in ambient conditions and application requirements. Compared with the residential and personal wireless systems, industrial applications pose unique challenges due to their critical demands on reliability and real-time performance. We developed an experimental testbed by realizing key network mechanisms of industrial Wireless Sensor and Actuator Networks (WSANs) and conducted an empirical study that revealed the limitations and potential enhancements of those mechanisms. Our study shows that graph routing is more resilient to interference and its backup routes may be heavily used in noisy environments, which demonstrate the necessity of path diversity for reliable WSANs. Our study also suggests that combining channel diversity with retransmission may effectively reduce the burstiness of transmission failures and judicious allocation of multiple transmissions in a shared slot can effectively improve network capacity without significantly impacting reliability

Performance evaluation of directional antennas in ZigBee networks under NLOS propagation conditions

Many authors suggest directional antennas to enhance the transmission performance of ZigBee networks. For line-of-sight propagation, directional antennas can extend the transmission range or reduce the transmit power. Directional antennas may also reduce interference between networks operating in the same frequency channel. However, these antennas may not perform similarly under non-line-of-sight propagation conditions. This work presents a study with ZigBee modules comparing the performance of a directional antenna with an omnidirectional one. The measurements were conducted on a university campus for different propagation outdoor environ ments. A deconvolution technique was applied to estimate the received signal as a function of the azimuth angle. The results demonstrated that the received power followed the gain difference between antennas only for paths with low attenuation. Considering the same Effective Isotropic Radiated Power (EIRP), the system with directional antennas started to lose packets at the same distance as the omnidirectional antennas. The directional antenna did not allow the increase in the link range compared to the omnidirectional antenna. The power consumption was also measured for different transmit power levels of the ZigBee radio. The study showed that the control circuits of directional antennas typically consume more power than omnidirectional antennas operating at a higher transmit power level.info:eu-repo/semantics/publishedVersio

Embracing corruption burstiness: Fast error recovery for ZigBee under wi-Fi interference

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The ZigBee communication can be easily and severely interfered by Wi-Fi traffic. Error recovery, as an important means for ZigBee to survive Wi-Fi interference, has been extensively studied in recent years. The existing works add upfront redundancy to in-packet blocks for recovering a certain number of random corruptions. Therefore the bursty nature of ZigBee in-packet corruptions under Wi-Fi interference is often considered harmful, since some blocks are full of errors which cannot be recovered and some blocks have no errors but still requiring redundancy. As a result, they often use interleaving to reshape the bursty errors, before applying complex FEC codes to recover the re-shaped random distributed errors. In this paper, we take a different view that burstiness may be helpful. With burstiness, the in-packet corruptions are often consecutive and the requirement for error recovery is reduced as ”recovering any k consecutive errors” instead of ”recovering any random k errors”. This lowered requirement allows us to design far more efficient code than the existing FEC codes. Motivated by this implication, we exploit the corruption burstiness to design a simple yet effective error recovery code using XOR operations (called ZiXOR). ZiXOR uses XOR code and the delay is significantly reduced. More, ZiXOR uses RSSI-hinted approach to detect in packet corruptions without CRC, incurring almost no extra transmission overhead. The testbed evaluation results show that ZiXOR outperforms the state-of-the-art works in terms of the throughput (by 47%) and latency (by 22%)This work was supported by the National Natural Science Foundation of China (No. 61602095 and No. 61472360), the Fundamental Research Funds for the Central Universities (No. ZYGX2016KYQD098 and No. 2016FZA5010), National Key Technology R&D Program (Grant No. 2014BAK15B02), CCFIntel Young Faculty Researcher Program, CCF-Tencent Open Research Fund, China Ministry of Education—China Mobile Joint Project under Grant No. MCM20150401 and the EU FP7 CLIMBER project under Grant Agreement No. PIRSES-GA- 2012-318939. Wei Dong is the corresponding author

A Comprehensive Analysis of Literature Reported Mac and Phy Enhancements of Zigbee and its Alliances

Wireless communication is one of the most required technologies by the common man. The strength of this technology is rigorously progressing towards several novel directions in establishing personal wireless networks mounted over on low power consuming systems. The cutting-edge communication technologies like bluetooth, WIFI and ZigBee significantly play a prime role to cater the basic needs of any individual. ZigBee is one such evolutionary technology steadily getting its popularity in establishing personal wireless networks which is built on small and low-power digital radios. Zigbee defines the physical and MAC layers built on IEEE standard. This paper presents a comprehensive survey of literature reported MAC and PHY enhancements of ZigBee and its contemporary technologies with respect to performance, power consumption, scheduling, resource management and timing and address binding. The work also discusses on the areas of ZigBee MAC and PHY towards their design for specific applications

Interference mitigation strategy design and applications for wireless sensor networks

The Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard presents a very useful technology for implementing low-cost, low-power, wireless sensor networks. Its main focus, which is to applications requiring simple wireless connectivity with relaxed throughout and latency requirements, makes it suitable for connecting devices that have not been networked, such as industrial and control instrumentation equipments, agricultural equipments, vehicular equipments, and home appliances. Its usage of the license-free 2.4 GHz frequency band makes the technique successful for fast and worldwide market deployments. However, concerns about interference have arisen due to the presence of other wireless technologies using the same spectrum. Although the IEEE 802.15.4 standard has provided some mechanisms, to enhance capability to coexist with other wireless devices operating on the same frequency band, including Carrier Sensor Multiple Access (CSMA), Clear Channel Assessment (CCA), channel alignment, and low duty cycle, it is essential to design and implement adjustable mechanisms for an IEEE 802.15.4 based system integrated into a practical application to deal with interference which changes randomly over time. Among the potential interfering systems (Wi-Fi, Bluetooth, cordless phones, microwave ovens, wireless headsets, etc) which work on the same Industrial, Scientific, and Medical (ISM) frequency band, Wi-Fi systems (IEEE 802.11 technique) have attracted most concerns because of their high transmission power and large deployment in both residential and office environments. This thesis aims to propose a methodology for IEEE 802.15.4 wireless systems to adopt proper adjustment in order to mitigate the effect of interference caused by IEEE 802.11 systems through energy detection, channel agility and data recovery. The contribution of this thesis consists of five parts. Firstly, a strategy is proposed to enable IEEE 802.15.4 systems to maintain normal communications using the means of consecutive transmissions, when the system s default mechanism of retransmission is insufficient to ensure successful rate due to the occurrence of Wi-Fi interference. Secondly, a novel strategy is proposed to use a feasible way for IEEE 802.15.4 systems to estimate the interference pattern, and accordingly adjust system parameters for the purpose of achieving optimized communication effectiveness during time of interference without relying on hardware changes and IEEE 802.15.4 protocol modifications. Thirdly, a data recovery mechanism is proposed for transport control to be applied for recovering lost data by associating with the proposed strategies to ensure the data integrity when IEEE 802.15.4 systems are suffering from interference. Fourthly, a practical case is studied to discuss how to design a sustainable system for home automation application constructed on the basis of IEEE 802.15.4 technique. Finally, a comprehensive design is proposed to enable the implementation of an interference mitigation strategy for IEEE 802.15.4 based ad hoc WSNs within a structure of building fire safety monitoring system. The proposed strategies and system designs are demonstrated mainly through theoretical analysis and experimental tests. The results obtained from the experimental tests have verified that the interference caused by an IEEE 802.11 system on an IEEE 802.15.4 system can be effectively mitigated through adjusting IEEE 802.15.4 system s parameters cooperating with interference pattern estimation. The proposed methods are suitable to be integrated into a system-level solution for an IEEE 802.15.4 system to deal with interference, which is also applicable to those wireless systems facing similar interference issues to enable the development of efficient mitigation strategies