WiFi (IEEE 802.11)

WIRELESS SENSOR COMMUNICATON USING WiFi (IEEE 802.11) WITH WiWIZ1 AND uSIM

INTRODUCTION


WiFi (802.11) is a high performance wireless network which is primarily used as a connection to the internet by portable devices such as laptop computers, PDA (Personal Digital Assistants), smart cell phones, numerous other applications. In most of the present applications power consumption and size are not primary considerations. It would be very difficult to build battery powered sensor devices using present WiFi implementations.

 

WiHART Systems now can bring WiFi to the wireless sensor world by introducing an ultra low power power Wi-Fi module for the WiWIZ1 and the uSIM wireless sensor modules. The WiHART Systems Wi-Fi modules reduce the power consumption of the standard WiFi interfaces by a factor of 4-5X thus allowing for battery powered remote and portable systems.

 

The Wi-Fi wireless module can be utilized in several different modes.

 

WiFi with 802.15.4 wireless mesh

 

When the WiFi module is used on the WiWiz1 it can be used in conjunction with a IEEE 802.15.4 wireless mesh protocol(wireless HART, ISA100, Zigbee) . The wireless mesh is used to gather information from the sensors and the WiFi can be used in a gateway mode where the information from the mesh is transferred to the backbone WiFi access point. (See description below of the WiHART Systems backbone access point)



For example, in a Wireless HART network, the information from the remote Wireless HART sensors is transferred to the WiFi network using the application processor on the WiWIZ1. It is not necessary to have a separate design to act as a WiFi gateway. This functionality is added in a modular way to the basic wireless platform.



WiFi with Wi-Fi (802.11) Wireless Mesh

 

In most commercial applications of WiFi the topology is master and slave. All the client devices such as laptops, PDAs, cell phones, etc. are configured in a star topology with the access point acting as the master with a connection to the Internet usually using an Ethernet connection. This is the topology used in millions of WiFi deployments. WiFi can also be configured as an ad-hoc mesh network in a matter similar to mesh networks using IEEE 802.15.4. This each WiWIZ1 can be considered a mesh sensor node without any other wireless communication connectivity. Each WiFi mesh node acts as a wireless sensor node and operates in a peer to peer mesh sending information back to access point using standard TCP/IP and the information is placed on a server (also web server). It is possible to implement a wireless sensor network using WiFi because of the ultra low power consumption of the WiHART Systems WiFi implementation.

 

Wi-Fi has established world wide infrastructure and one can use this to establish a sensor network using presently available standard hardware and software. It also provides for a simple link to the Internet via standard access points.

 

As with all WiHART systems products the programmable microprocessor is attached to the WiFi module and specific application software can be written for the unique application.

 

 

Industrial WiFi Access Point

 

The WiHART Systems access point is a unique device especially designed for exterior applications in industrial wireless applications. See photo below.

 

 

 

Unlike most commercial access points the WiWIZ1 access point has two(2) radios that are compatible with the 802.11 standard. The normal configuration is for one radio to act as a standard access point or a node in an ad-hoc wireless mesh. In other words this unit could replace a standard WiFi access point in your house or office. If configured as a mesh network point it would join a WiFi network as discussed above with the sensor modules.

 

The second radio can be used as a bridge to a back bone network which is not connected to the mesh networks with the sensors. It technical terms it can be considered a bridge to the backbone 802.11 network which is a separate and distinct network from the wireless mesh with the sensors or the sensor node configured in a star topology. To avoid interference both the Access Point (AP) radio and the backbone radio can operate according to 802.11a which operates in the 5 Gigahertz band. The 5 Gigahertz band has less interference and will not interact with operation on the standard 2.4 gigahertz band.

 

The back bone network can be configured as a wireless mesh in the 5 gigahertz band while the AP radio can be operating in the 2.5 gigahertz band communicating with the sensor modules. Using a bridge (defined as layer 2 in the OSI model) the information is forwarded to the 5 gigahertz band.

 

The access point is housed in an aluminum enclosure rated IP67. It utilizes POE (Power Over Internet)

in the same manner as the WiWIZ1 which incorporates an Ethernet connection and web server.

WiVIB1 and WiFi

 

The WiVIB1 wireless vibration sensor module (uSIM) is the first in a product line of small wireless modules for single applications. The WiVIB1 uses nanotechnology to reduce the size and power consumption for wireless vibration measurement. At the present time it comes with a choice of radios.

 

A radio based on WiFi is an option. The WiVIB1 uses the same low power WiFi module that is available on the WiWIZ1 development platform. The module measures about 1 square inch and can communicate directly with the access point described above both in a standard master slave mode or in the ad hoc mesh mode. It is then possible to set up a sensor network based solely on 802.11.

 

 

 

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