Jianlin Guo

Load balanced routing for low power and lossy networks

The RPL routing protocol published in RFC 6550 was designed for efficient and reliable data collection in low-power and lossy networks. Specifically, it constructs a Destination Oriented Directed Acyclic Graph (DODAG) for data forwarding. However, due to the uneven deployment of sensor nodes in large areas, and the heterogeneous traffic patterns in the network, some sensor nodes may have much heavier workload in terms of packets forwarded than others. Such unbalanced workload distribution will result in these sensor nodes quickly exhausting their energy, and therefore shorten the overall network lifetime. In this paper, we propose a load balanced routing protocol based on the RPL protocol, named LB-RPL, to achieve balanced workload distribution in the network. Targeted at the low-power and lossy network environments, LB-RPL detects workload imbalance in a distributed and non-intrusive fashion. In addition, it optimizes the data forwarding path by jointly considering both workload distribution and link-layer communication qualities. We demonstrate the performance superiority of our LB-RPL protocol over original RPL through extensive simulations.

Prioritized Broadcast Contention Control in VANET

Reliable and timely multi-hop propagation of messages among vehicles is essential for a safer and greener transportation system. Various broadcast-based forwarding strategies are envisioned for infrastructure-less vehicle-to-vehicle (v2v) communications. This paper proposes a prioritized broadcast contention control (PBCC) module/layer that provides reliable and low latency multi-hop connection. The PBCC forwarding algorithm optimizes the back-off distribution to improve the probability of successful broadcast and prioritizes forwarders based on location information. This module can be implemented in WAVE devices with minimum system modification. We integrate simple vehicular mobility models into ns-2 and implement a WAVE/802.11p communication protocol stack. Extensive simulations demonstrate PBCCs superiority in multi-hop delay.

Reliable routing in large scale wireless sensor networks

Wireless sensor networks have a wide range of applications including target detection and tracking, environment monitoring, industrial process monitoring, hospital monitoring, and public utility service. A sensor network consists of a large number of sensor nodes and a few sink nodes to collect data from sensor nodes. Sensor nodes and sink nodes form a large scale wireless mesh network in which packets are typically delivered between sensor nodes and sink nodes in a multi-hop manner. Reliable packet routing in wireless sensor networks is crucial, especially when network size is large. This paper presents a reliable routing protocol (RRP) to maximize the reliability of data collection and control command delivery in large scale wireless sensor networks. RRP aims to discover multiple bidirectional routes between a sensor node and a sink node. Sink node initiates route construction with an imaginary node as the destination to guarantee complete routing topology buildup. RRP achieves load balance by sending data packets via the route with lighter workload. RRP can be optimized for lightweight routing. Simulation results show that the proposed RRP routing protocol can realize 100% of packet delivery rate and outperforms existing routing protocols in terms of packet delivery rate, routing packet overhead, and end-to-end packet delay.

Stability metric based routing protocol for low-power and lossy networks

To design a routing protocol for applications over low-power and lossy networks (LLNs), the IETF ROLL Working Group standardized the IPv6 Routing Protocol for LLNs (RPL), which organizes nodes in a LLN into a tree-like topology called Destination Oriented Directed Acyclic Graph (DODAG). RPL shows good scalability and fast network setup. However, it may suffer from severe unreliability due to the selection of suboptimal routes with low quality links. To optimize the reliability of RPL routes, this paper proposes a stability metric based routing protocol named sRPL for reliable routing and data collection in LLNs. We introduce a new routing metric for RPL called stability index (SI), which exploits stability characteristics of RPL nodes to select more stable routes. In addition, we present a passive and lightweight network layer technique to measure the bi-directional expected transmission count (ETX) for wireless links in LLNs. As a use case of SI, we combine SI metric with ETX metric to make routing decisions. Simulation results show that sRPL can improve packet delivery rate of RPL routing protocol by 20%.

Battery Energy Management in Heterogeneous Wireless Machine-to-Machine Networks

The IETF standardized the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) to meet routing requirements of the emerging applications. RPL is a distributed routing protocol and shows good scalability and fast network setup. However, RPL does not support sleep operation well. To provide efficient energy management and enhance RPL for sleep operation support, this paper presents battery energy management solutions for heterogeneous wireless machine-to-machine networks containing both battery powered nodes and mains powered nodes. We introduce a distributed sleep model for battery powered nodes to manage their own sleep schedules based on their internal parameters and observed network conditions. We propose two broadcast message delivery methods for battery operated networks that use distributed sleep control. Two battery node aware routing metrics are introduced to discover more battery energy efficient routes. We also present a battery energy efficient routing protocol called B-RPL to leverage distributed sleep model and introduced routing metrics. A battery energy efficient data packet transmission and forwarding method is provided to select the most battery energy efficient route among multiple active routes to transmit and forward data packets. Simulation results show that compared with standard RPL, the proposed B-RPL can extend network lifetime by two times and improve data packet delivery rate by 75%.

Resource Aware Routing Protocol in Heterogeneous Wireless Machine-to-Machine Networks

Routing algorithm can significantly impact network performance. Routing in a network containing heterogeneous nodes differs from routing in a network with homogeneous nodes. If the routing algorithm is designed to fit less powerful nodes, the resources of more powerful nodes are wasted and network performance can be degraded. If the routing algorithm is developed to suit more powerful nodes, less powerful nodes may not have sufficient resources to run the algorithm and network may break down. Routing algorithms developed for homogeneous networks do not work well for heterogeneous networks. The IETF designed the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) by taking into account resource heterogeneity and defined four modes of operation. However, RPL only allows one mode of operation for all routers in a network. This paper proposes a resource-aware adaptive mode RPL (RAM-RPL) to achieve adaptive mode of operation in heterogeneous wireless machine-to-machine (M2M) networks. RAM-RPL not only allows routers to have mixed modes of operation in a network but also allows routers to adaptively adjust their modes of operation during network operation. Acting parent and acting root techniques are introduced to realize adaptive mode of operation and route compression. RAM-RPL exploits resource heterogeneity and shifts routing workload from less powerful nodes to more powerful nodes. Simulation results show that RAM-RPL can improve data packet delivery rate by 26% and reduce control message overhead by 53% while maintaining similar packet latency.

Self-transmission control in IoT over heterogeneous wireless networks

With the increasing development of the IoT applications, heterogeneous wireless networks may coexist. IEEE 802.11ah and IEEE 802.15.4g are two wireless technologies designed for IoT applications. 802.11ah is primarily developed for outdoor applications such as smart city and 802.15.4g is principally developed for large scale outdoor process control applications such as smart utility network. Both technologies have communication range up to 1000 meters. Therefore, 802.11ah network and 802.15.4g network are likely to coexist. Our simulation results show that 802.11ah network can severely interfere with 802.15.4g network since 802.11ah devices are more aggressive than 802.15.4g devices in wireless medium access contention. This capability heterogeneity can lead to significant packet loss in 802.15.4g network. Due to asymmetrical features such as modulation scheme and packet structure, devices in different networks can not understand each other. Thus, the self-transmission control mechanism is needed for more aggressive 802.11ah devices. This paper proposes a learning based self-transmission control method for 802.11ah devices to improve their coexistence with 802.15.4g devices. Using the proposed self-transmission control technique, 802.11ah devices predict the packet transmission of 802.15.4g devices and postpone their transmissions to avoid interference.

Distributed sleep management for heterogeneous wireless machine-to-machine networks

Wireless machine-to-machine (M2M) communications are widely considered as part of the Internet of Things (IoT) infrastructure. Resource management is crucial for heterogeneous M2M networks. In this paper, we present new distributed sleep management techniques to prolong network lifetime for multi-hop heterogeneous wireless M2M networks, which consist of battery-powered nodes and mains-powered nodes. We also propose two novel battery energy aware routing metrics to efficiently select routes that satisfy performance guarantees. Finally, we present an extensive performance evaluation of our sleep management techniques and routing metrics. Simulation results show that our schemes achieve high packet delivery rate, long network lifetime and low energy consumption even in very low percentage of mains-powered nodes.

Resource aware hierarchical routing in heterogeneous wireless IoT networks

Routing algorithm consumes the resources of the network nodes. Different routing algorithms require different amount of the resources. Nodes at different positions of the network topology require different amount of the resources. Routing algorithm must adapt to both available resources and required resources of the nodes. The IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) considers memory and defines four modes of operation (MOPs). However, RPL allows only one MOP for all routers in a network. This paper presents a resource aware hierarchical RPL (H-RPL) to realize the mixed MOPs and the resource adaptation in heterogeneous wireless IoT networks. Taking routing preferences of the nodes into account, H-RPL also applies heterogeneous routing metrics and objective functions in hierarchical network topology construction. A new MOP is introduced to indicate the critical resource condition of the node. The required routing memory and the expected routing lifetime are proposed to determine the MOP of the node. The MOP downgrade and the MOP upgrade are introduced to address traffic congestion caused by the isolated higher resource node and to exploit the renewed resources and the resource requirement relaxation, respectively. The queue utilization based data transmission distributes data packets for load balance and network performance improvement. Simulation results show that H-RPL can improve upward data packet delivery rate by 7%, downward data packet delivery rate by 25% and extend network lifetime by 78%.