Wireless Sensor Networks

The radio technology used in MEMSIC's wireless modules supports domestic and international frequency bands in the 433 MHz, 868-915 MHz, and 2.4 GHz bands. Multiple channels are available in each band under software control, resulting in a flexible solution for customer applications. Two modulation formats are available, two-tone Frequency-Shift-Keyed (FSK) at 433 and 868-915 MHz, and direct sequence spread spectrum (DSSS) at 2.4 GHz supporting the 802.15.4/ZigBee standard. All radios are bidirectional (half-duplex), and support a range of 30 to 1000 feet (10 to 100 meters) using XMesh with low-power protocol and battery-life time of 5 plus years in commercial applications. Transmit power levels are software controlled to enable end users to comply with local government regulations for frequency transmission.

The processor has full control of radio features, and can control parameters such as transmit/receive mode switching, channel selection, output power, and radio standby mode. Data packets routed through the radio are error correction encoded, with the ability to listen to the channel via RSSI measurement to determine if the channel is clear to send data. Depending on choice of radio and configuration, data rates of 19.2kbps to 240kbps are available. Both the radio and processor support deep sleep modes for maximum power savings. The motes are designed to support battery operation from 2.4V to 3.6V, with an integral battery voltage monitor.

Mesh Networking

XMesh is a full featured multi-hop, ad-hoc, mesh networking protocol developed for MEMSIC’s wireless sensor networks. XMesh is a software library, using the TinyOS operating system that runs on embedded devices called Motes. All wireless mesh networking systems share a set of common requirements. These include Low-power Consumption, Ease-of-Use, Scalability, Responsiveness and Range.

An XMesh network consists of nodes, Motes, that wirelessly communicate to each other and are capable of hopping radio messages to a base station where they are passed to a PC or other client. The hopping effectively extends radio communication range and reduces the power required to transmit messages, low-power (5+ years of battery-life).

By hopping data in this way, XMesh can provide two critical benefits, improved radio coverage and improved reliability, XMESH is self-forming and self-healing. Two nodes do not need to be within direct radio range of each other to communicate. A message can be delivered to one or more nodes in-between which will route the data. Likewise, if there is a bad radio link between two nodes, that obstacle can be overcome by rerouting around the area of bad service. Typically the nodes run in a low power mode, spending most of their time in a sleep state, in order to achieve multi-year battery -life.

XMesh Key Features:

• Reliable, Multi-hop Mesh Networking
• Self-forming and Self-healing Network
• Star, Hybrid-star- ZigBee and Mesh Topology for Entirely Battery Operated Networks
• Over-the-Air Programming, XOtap
• Fully Bi-Directional Communication with Fast Response Times
• 802.15.4, ZigBee Support
• Gateway Middleware

XServe is the layer that connects the wireless sensor network to enterprise or industrial networks through standard XML. Due to the low-power and memory footprint requirements in wireless sensor networks, communication is streamlined through message formats and network protocols. This differs from the IP protocols used in IT back-end systems or existing industrial networks. XServe effectively bridges these different worlds through the support of standard XML API's.

A local database allows XServe to store and process sensor and network information. Integration with back-end monitoring, control and management systems delivers the full value of wireless sensor networks to enterprises and makes the connection of the physical world with the internet a reality.

• Enterprise Connectivity
• Database for Sensor Data
• Bi-Directional XML API
• Network Management

Network Management

XOTAP delivers over-the-air-programming and updating of sensor nodes reliability over a low-data rate wireless network. With XOTAP, firmware and application upgrades can be delivered to wireless sensor networks and managed remotely over the Internet. Individual wireless sensors, a group of sensors or the whole network can be programmed, even in a fully battery-operated network.

Key Features:

• Reliable Node Reprogramming Over Low-data Rate Network
• User Interface to Manage Programming of Motes
• Peer-to-peer and Multicast Mote Programming
• Programming of Low-power, Battery-operated Networks

XJoin provides for auto-join of nodes in a network installation, eliminating the need for nodes to be programmed for a specific network during installation, greatly reducing the time required to install a wireless sensor networks. XJoin also provides authentication capabilities that allow the network installer and operator to easily decide which sensor nodes are allowed to join the network.

Key Features:

• Auto-join of Sensor Motes
• Auto-commissioning of Motes
• Authentication of Joining Motes
• WSN User Interface

WSN User Interface

The graphical user interface is designed and is a deployed network of wireless sensors. It is targeted to end-users as a complete end-to-end software suite to simplify deployment and monitoring.

• Sensor Data Visualization and Analysis
• Network Topology Mapping
• Alarm Services
• Configuration and Management Interface
• Network Analysis (XSniffer)

MoteView

MoteView is an interface ("client tier") between a user and a deployed network of wireless sensors. MoteView provides the tools to simplify deployment and monitoring. It also makes it easy to connect to a database, to analyze, to visualize the mesh and to graph sensor readings.

MoteConfig

MoteConfig provides an interface for configuring and downloading pre-compiled XMesh firmware applications onto Motes. MoteConfig allows the user to configure the Mote ID, Group ID, RF channel and RF power. The users can also use MoteConfig to program the XMesh nodes in the network remotely over-the-air.

XSniffer

XSniffer that allows users to monitor RF packet traffic and multi-hop communication over XMesh. XSniffer can be used to monitor and display all radio messages overhead within its radio range such as health/data packets, downstream radio communications, radio message retries, route update and time synchronization messages.