Assessing Coexistence of IEEE 802.15.4 Networks and IEEE 802.11b/g/n Networks - A Study of Interference Effects

The study of the coexistence capabilities of networks based on the IEEE 802.11 and IEEE 802.15.4 standards has long been of interest to researchers owing to the individual success of these two technologies in various applications of Internet of Things (IoT). Operating in the same Industrial-Scientific-Medical (ISM) band, their coexistence does not always yield satisfactory results. The performance of a network based on IEEE 802.15.4 standard has been shown to be significantly lowered in the presence of a strong IEEE 802.11 based network (Wireless LAN) to the extent that communication based on the IEEE 802.15.4 standard can be rendered impossible in certain scenarios. This work is an effort towards analyzing interference caused by the three non-overlapping channels 1, 6 and 11 of IEEE 802.11b/g/n on the usable 2.4GHz spectrum of IEEE 802.15.4 standard. Recommendations of plausible scenarios for successful coexistence of these two networking technologies have been made. Assessment of the performance of an IEEE 802.15.4 standard based network through the Packet Delivery Ratio (PDR) on various channels of operation has yielded valuable insights. The experiments carried out in real-world environment stand as datapoints in predicting and understanding the interference behavior in real-life applications

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

Enhancing ZigBee throughput under WiFi interference using real-time adaptive coding

33rd IEEE Conference on Computer Communications, IEEE INFOCOM 2014, Toronto, ON, 27 April-2 May 2014Co-existing in the unlicensed ISM band, ZigBee transmissions can be significantly interfered by WiFi. Although several approaches recently are proposed to enable ZigBee transmission under WiFi interference, the ZigBee throughput still decreases to zero when WiFi throughput (generated by D-ITG) is over 8Mbps. In this paper, we propose a real-time (< 5ms) adaptive transmission (RAT) scheme to efficiently adapt forward error-correction coding (FEC) on ZigBee devices in dynamic WiFi environment. We find that sizes of WiFi frames well follow the power law distribution model. With the model, corruption in ZigBee packets can be estimated to some extent, thus facilitating ZigBee device to choose a suitable FEC coding to maximize the throughput. Extensive experimental results show that, compared with existing works, RAT achieves significant performance improvement of ZigBee transmissions in WiFi environment with different traffic load. Particularly, the ZigBee throughput of RAT can be about 10kbps when the WiFi throughput is 8Mbps.Department of ComputingRefereed conference pape

간섭 환경에서 저전력 무선 센서 네트워킹에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2017. 2. 이용환.The demand for commercial deployment of large-scale wireless sensor networks (WSNs) has rapidly been increasing over the past decade. However, conventional WSN technologies may not be feasible for commercial deployment of large-scale WSNs because of their technical flaws, including limited network scalability, susceptibility to co-channel interference and large signaling overhead. In practice, low-power WSNs seriously suffer from interference generated by coexisting radio systems such as IEEE 802.11 wireless local area networks (WLANs). This interference problem seriously hampers commercial deployment of low-power WSNs. Few commercial WSN chips can provide secure and reliable networking performance in practical operation environments. In this dissertation, we consider performance improvement of low-power WSNs in the presence of co-channel interference. We first investigate the effect of co-channel interference on the transmission of low-power WSN signal, and then design a low-power WSN transceiver that can provide stable performance even in the presence of severe co-channel interference, while providing the backward compatibility with IEEE 802.15.4. We also consider the network connectivity in the presence of co-channel interference. The connectivity of low-power WSNs can be improved by transmitting synchronization signal and making channel hand-off in a channel-aware manner. A beacon signal for the network synchronization is repeatedly transmitted in consideration of channel condition and signaling overhead. Moreover, when the channel is severely interfered, all devices in a cluster network make communications by means of temporary channel hopping and then seamlessly make channel hand-off to the best one among the temporary hopping channels. The performance improvement is verified by computer simulation and experiment using IEEE 802.15.4 motes in real operation environments. Finally, we consider the signal transmission in the presence of co-channel interference. The throughput performance of low-power WSN transceivers can be improved by adjusting the transmission rate and the payload size according to the interference condition. We estimate the probability of transmission failure and the data throughput, and then determine the payload size to maximize the throughput performance. It is shown that the transmission time maximizing the normalized throughput is little affected by the transmission rate, but rather by the interference condition. The transmission rate and the transmission time can independently be adjusted in response to the change of channel and interference condition, respectively. The performance improvement is verified by computer simulation.Chapter 1 1 Chapter 2 11 2.1. ZigBee/IEEE 802.15.4-based cluster-tree networks 11 2.2. Performance of IEEE 802.15.4 transceiver 14 Chapter 3 17 3.1. System model 18 3.2. Previous works 21 3.3. Proposed interference management scheme 28 3.4. Performance evaluation 37 Chapter 4 51 4.1. System model 52 4.2. Transmission in the presence of interference 56 4.3. Proposed transmission scheme 60 4.4. Performance evaluation 65 Chapter 5 82 Appendix 85 A. Average synchronization time during frequency hopping 85 B. Derivation of (4.2) 86 References 88 Korean Abstract 97Docto