Powerline Home Network Diagram

This diagram illustrates use of HomePlug equipment to build a powerline home network. See below for a detailed description of this layout.

Powerline Home Network Diagram Featuring Powerline Router

Key Considerations - Powerline networks utilize the ordinary electrical circuity of a residence to carry home network communications. Available powerline equipment includes network routers, network bridges and other adapters. To connect to a powerline network, one end of the adapter plugs into a standard electric wall outlet while the other connects to a device's network port (usually Ethernet or USB). All connected devices share the same communication circuit.
The HomePlug Powerline Alliance develops technology standards supported by compatible powerline equipment.
Optional Components - Not all devices on the home network must be connected to a powerline router; hybrid networks with Ethernet or Wi-Fi devices can be joined with the powerline network. For example, a Wi-Fi powerline bridge can optionally be plugged into a wall outlet, enabling wireless devices to connect to it and in turn to the rest of the powerline network.
Limitations - HomePlug phoneline networking remains much less popular than Wi-Fi or Ethernet alternatives. Powerline networking products will generally be more difficult to find with fewer choices of models for this reason.
Powerline networks generally do not work as reliably if devices plug into power strips or extensions cords. Connect directly to the wall outlets for best results. In homes with multiple circuits installed, all devices must connect to the same one circuit to communicate with each other.
The maximum bandwidth of a HomePlug (version 1.0) powerline network is 14 Mbps, while the newer HomePlug AV standard supports more than 100 Mbps. Poor quality electrical wiring as found in older homes can degrade the performance of a powerline network.

Phoneline Home Network Diagram

This diagram illustrates use of Home Phoneline Networking Alliance equipment to build a home network. See below for a detailed description of this layout.

Phoneline Home Network Diagram Featuring HPNA Gateway / Router

Key Considerations - Phoneline networks utilize the ordinary telephone wiring of a residence to carry home network communications. As with Ethernet or Wi-Fi networks, phoneline networks require each device to have a compatible phoneline network adapter installed. These adapters are connected by ordinary phone wires (or sometimes CAT5 Ethernet cable) to telephone wall outlets. When connecting multiple computers with phoneline networking, one central computer "gateway" must be established. The gateway represents the network's primary device for connecting to the Internet. A few models of home network routers (sometimes called "residential gateways") support phoneline networking today. Otherwise, you must designate one computer as the gateway and install two network adapters on this computer to enable it for gateway functions. Depending on the type of primary device chosen, hybrid networks with a combination of phoneline, Ethernet or Wi-Fi devices can be created.
The Home Phoneline Networking Alliance (HomePNA) develops technology standards that compatible phoneline equipment must support.
Optional Components - As mentioned above, a network router is optional when building a phoneline home network. Phoneline networking also works regardless of whether the residence is subscribed either to basic local telephone service or to DSL Internet service.
Limitations - HomePNA phoneline networking has proven much less popular than Wi-Fi or Ethernet alternatives. Phoneline networking products will generally be more difficult to find, and there will be fewer choices of models for this reason.
All phoneline network equipment must be connected to the same electrical circuit within the residence. Specifically, residences that have two phone lines installed, must choose one or the other line to connect all devices.
The range of an HomePNA (version 2.0) phoneline network is about 1000 feet (300 m). The maximum bandwidth of an HomePNA 2.0 network is 10 Mbps, while an HomePNA 3.0 network supports more than 100 Mbps. The speed of phoneline networking can suffer depending on the quality of phone cables installed in the residence.

Ethernet Hub/Switch Network Diagram

This diagram illustrates use of an Ethernet hub or switch on a home network. See below for a detailed description of this layout.

Wired Home Network Diagram Featuring Ethernet Hub or Switch

Key Considerations - Ethernet hubs and switches allow multiple wired computers to network with each other. Most (but not all) Ethernet hubs and switches support up to four connections. Optional Components - Networking of Internet access, printers, or game consoles and other entertainment devices is not required for the rest of this home network layout to function. Simply omit any of these components shown that do not exist in your design.
Additional hubs and switches can be incorporated to the basic layout shown. Connecting hubs and/or switches to each other expands the total number of computers the network can support up to several dozen.
Limitations - All computers connecting to a hub or switch must possess a working Ethernet network adapter.
As shown, unlike a network router, Ethernet hubs and switches cannot interface directly to an Internet connection. Instead, one computer must be designated as controlling the Internet connection and all other computers access the Internet through it. Internet connection sharing software can be installed on each computer for this purpose.

Ad Hoc Wireless Network Diagram

Common layout for WiFi-based home networks

This diagram illustrates use of a so-called ad hoc wireless setup in a home network. See below for a detailed description of this layout.

Wireless Home Network Diagram Featuring Ad Hoc Wi-Fi Connections

Key Considerations - Using ad hoc Wi-Fi mode eliminates the need for a network router or access point in a wireless home network. With ad hoc wireless, you can network computers together as needed without needing to be in reach of one central location. Most people use ad hoc Wi-Fi only in temporary situations to avoid potential security issues. Optional Components - Networking an ad hoc layout for Internet access, printers, or game consoles and other entertainment devices is not required for the rest of the home network to function. Simply omit any of these components shown that do not exist in your layout.
Limitations - All devices connecting via ad hoc wireless must possess a working Wi-Fi network adapter. These adapters must be configured for "ad hoc" mode instead of the more typical "infrastructure" mode.
Because of their more flexible design, ad hoc Wi-Fi networks are also more difficult to keep secure than those using central wireless routers / access points.
Ad hoc Wi-Fi networks support a maximum of 11 Mbps bandwidth, while other Wi-Fi networks may support 54 Mbps or higher.

Direct Connection Network Diagram

Common layout for simple Ethernet home networks

This diagram illustrates direct connection without a router or other central device on the home network. See below for a detailed description of this layout.

Wired Home Network Diagram Featuring Direct Connection

wired home network diagram direct connection

Key Considerations - Direct connection can be achieved with several different types of cabling. Ethernet cabling is the most common, but even simpler (slower) alternatives exist including RS-232 serial cable, and parallel cable. Direct Connection is common for game consoles to support two-player network gaming (e.g., Xbox System Link).
Optional Components - Connecting to the Internet requires that one computer possess two network adapters - one to support the Internet connection and one to support the second computer. Additionally, Internet connection sharing software must be installed to allow the second computer Internet access. If Internet connectivity is not necessary, these things can be omitted from this layout.
Limitations - Direct connection works only for a single pair of computers / devices. Additional devices cannot join such a network, although other pairs can be connected separately as shown above.

Hybrid Ethernet Router / Wireless Access Point Network Diagram

This diagram illustrates use of a hybrid wired network router / wireless access point home network. See below for a detailed description of this layout.

Hybrid Home Network Diagram Featuring Wired Router and Wireless Access Point

Key Considerations - Most (but not all) wired network routers allow up to four devices to be connected via Ethernet cable. A wireless access point consumes one of these available ports, but it then enables many (dozens of) WiFi devices to join the network. Nearly any home network wireless access point will have no issue managing to support the number of wireless devices there. However, if all WiFi computers attempt to use the network at the same time, performance slowdowns can result.
All devices connecting to an Ethernet router must possess a working Ethernet network adapter. All devices connecting a wireless access point must possess a working WiFi network adapter.
Optional Components - Networking of Internet access, printers, game consoles and other entertainment devices is not required for either the router or access point to function. Simply omit any of these components shown that do not exist in your layout.
You can choose which devices to connect to the router and which to the wireless access point. Additional network adapters may be needed to convert some Ethernet devices, particularly printers and game consoles, to work wirelessly.
Limitations - The WiFi portion of the network will function only to the limit of the wireless access point's range. The range of WiFi equipment varies depending on many factors including layout of the home and any radio interference that may be present.
If the wireless router does not support enough Ethernet connections, add a secondary device like a network switch to expand the wired portion of the layout.

Ethernet Router Network Diagram

This diagram illustrates use of a wired network router as the central device of a home network. See below for a detailed description of this layout.

Wired Home Network Diagram Featuring Ethernet Router

Key Considerations - Many (but not all) wired network routers allow up to four devices to be connected via Ethernet cable. All devices connecting to an Ethernet router must possess a working Ethernet network adapter.
Optional Components - Networking the router for Internet access, printers, game consoles and other entertainment devices is not required for the rest of the home network to function. Simply omit any of these components shown that do not exist in your layout.
Limitations - If the Ethernet router does not support enough Ethernet connections, add a secondary device like a network switch to expand the layout.

Wireless Router Network Diagram

This diagram illustrates use of a Wi-Fi wireless network router as the central device of a home network. See below for a detailed description of this layout.

Wireless Home Network Diagram Featuring Wi-Fi Router

.Key Considerations -

All devices connecting to a wireless router must possess a working network adapter. As illustrated in the diagram, connecting to the router a broadband modem (that has one or more built-in adapters) enables sharing of a high-speed Internet connection.

Wireless routers technically allow dozens of computers to connect over WiFi links. Nearly any residential wireless router will have no trouble supporting the number of wireless devices found in typical homes. However, if all WiFi computers attempt to use the network at the same time, slowdowns in performance should be expected.

Many (but not all) wireless network routers also allow up to four wired devices to be connected via Ethernet cable. When first installing this kind of home network, one computer should be cabled to the wireless router temporarily to allow initial configuration of the wireless features. Employing Ethernet connections after that is optional. Using permanent Ethernet connections make sense when the computer, printer or other device lacks WiFi capability or cannot receive an adequate wireless radio signal from the router.

Optional Components - Networking the router for Internet access, printers, game consoles and other entertainment devices is not required for the rest of the home network to function. Simply omit any of these components shown that do not exist in your layout.

Limitations - The WiFi portion of the network will function only to the limit of the wireless router's range. The range of WiFi equipment varies depending on many factors including layout of the home and any radio interference that may be present.

If the wireless router does not support enough Ethernet connections for you needs, add a secondary device like a network switch to expand the wired portion of the layout.

Wireless Range Extender

Wireless Range Extender

Linksys WRE54G Wireless Range Expander

Linksys WRE54G Wireless Range Expander

A wireless range extender increases the distance over which a WLAN signal can spread, overcoming obstacles and enhancing overall network signal quality. Several different forms of wireless range extenders are available. These products are sometimes called "range expanders" or "signal boosters." The Linksys WRE54G (compare prices) 802.11g Wireless Range Expander is shown above. A wireless range extender works as a relay or network repeater, picking up and reflecting WiFi signals from a network's base router or access point. The network performance of devices connected through a range extender will generally be lower than if they were connected directly to the primary base station.
A wireless range extender connects wirelessly to a WiFi router or access point. However, due to the nature of this technology, most wireless range extenders work only with a limited set of other equipment. Check the manufacturer's specifications carefully for compatiblity information.

Wireless Internet Video Cameras

Wireless Internet Video Cameras

Linksys WVC54G Wireless Internet Video Camera

linksys.com

A wireless Internet video camera allows video (and sometimes audio) data to be captured and transmitted across a WiFi computer network. Wireless Internet video cameras are available in both 802.11b and 802.11g varieties. The Linksys WVC54G (compare prices) 802.11g wireless camera is shown above. Wireless Internet video cameras work by serving up data streams to any computer that connects to them. Cameras like the one above contain a built in Web server. Computers connect to the camera using either a standard Web browser or through a special client user interface provided on CD-ROM with the product. With proper security information, video streams from these cameras can also be viewed across the Internet from authorized computers.
Wi-Fi Internet video cameras can be connected to a wireless router using either an Ethernet cable or wirelessly. These products include setup software on a CD-ROM that must be installed on one computer to complete initial Wi-Fi configuration of the device.
Features that distinguish different wireless Internet video cameras from each other include:

• resolution of the captured video images (for example, 320x240 pixel, 640x480 pixel, and other image sizes)
• motion sensors, and the ability to send email alerts when new activity is detected and captured
• ability to timestamp images
• built-in microphones and/or jacks for external microphones, for audio support
• types of WiFi security supported, such as WEP or WAP

Wireless Game Adapters

Wireless Game Adapters

Linksys WGA54G Wireless Game Adapter

linksys.com

A wireless game adapter connects a video game console to a Wi-Fi home network to enable Internet or head-to-head LAN gaming. Wireless game adapters for home networks are available in both 802.11b and 802.11g varieties. An example of an 802.11g wireless game adapter appears above, the Linksys WGA54G (compare prices). Wireless game adapters can be connected either to a wireless router using an Ethernet cable (for best reliability and performance) or over Wi-Fi (for greater reach and convenience). Wireless game adapter products include setup software on a CD-ROM that must be installed on one computer to complete initial configuration of the device. As with generic network adapters, wireless game adapters must be configured with the correct network name (SSID) and encryption settings.

Wireless Print Servers

Wireless Print Servers

Linksys WPS54G Wireless Print Server

linksys.com

A wireless print server allows one or two printers to be conveniently shared across a WiFi network. Wireless print servers for home networks generally are available in both 802.11b and 802.11g varieties. Wireless print servers offer the following advantages:

• Allows printers to be conveniently located anywhere within wireless network range, not tied to the location of computers
• Does not require a computer be always turned on in order to print
• Does not require a computer to manage all print jobs, that can bog down its performance
• Allows administrators to change computer names and other settings without having to re-configure the network printing settings.

A wireless print server must be connected to printers by a network cable, normally USB 1.1 or USB 2.0. The print server itself can connect to a wireless router over WiFi, or it can be joined using an Ethernet cable.
Most print server products include setup software on a CD-ROM that must be installed on one computer to complete the initial configuration of the device. As with network adapters, wireless print servers must be configured with the correct network name (SSID) and encryption settings. Additionally, a wireless print server requires client software be installed on each computer needing to use a printer.
The Linksys WPS54G (compare prices) 802.11g USB wireless print server is shown. Print servers are very compact devices that include a built-in wireless antenna and LED lights to indicate status.

Wireless Network Adapters

Wireless Network Adapters

Linksys WPC54G Wireless Network Adapter

linksys.com

A wireless network adapter allows a computing device to join a wireless LAN. Wireless network adapters contain a built-in radio transmitter and receiver. Each adapter supports one or more of the 802.11a, 802.11b, or 802.11g Wi-Fi standards. Wireless network adapters also exist in several different form factors. Traditional PCI wireless adapters are add-in cards designed for installation inside a desktop computer having a PCI bus. USB wireless adapters connect to the external USB port of a computer. Finally, so-called PC Card or PCMCIA wireless adapters insert into a narrow open bay on a notebook computer.
One example of a PC Card wireless adapter, the Linksys WPC54G (compare prices) is shown above. Each type of wireless network adapter is small, generally less than 6 inches (0.15 m) long. Each provides equivalent wireless capability according to the Wi-Fi standard it supports.
Some notebook computers are now manufactured with bulit-in wireless networking. Small chips inside the computer provide the equivalent functions of a network adapter. These computers obviously do not require separate installation of a separate wireless network adapter.

Wireless Access Points

Wireless Access Points

Linksys WAP54G Wireless Access Point

linksys.com

A wireless access point (sometimes called an "AP" or "WAP") serves to join or "bridge" wireless clients to a wired Ethernet network. Access points centralize all WiFi clients on a local network in so-called "infrastructure" mode. An access point in turn may connect to another access point, or to a wired Ethernet router. Wireless access points are commonly used in large office buildings to create one wireless local area network (WLAN) that spans a large area. Each access point typically supports up to 255 client computers. By connecting access points to each other, local networks having thousands of access points can be created. Client computers may move or "roam" between each of these access points as needed.
In home networking, wireless access points can be used to extend an existing home network based on a wired broadband router. The access point connects to the broadband router, allowing wireless clients to join the home network without needing to rewire or re-configure the Ethernet connections.
As illustrated by the Linksys WAP54G (compare prices) shown above, wireless access points appear physically similar to wireless routers. Wireless routers actually contain a wireless access point as part of their overall package. Like wireless routers, access points are available with support for 802.11a, 802.11b, 802.11g or combinations.

Wireless Routers

The centerpiece product of many home computer networks is a wireless router. These routers support all home computers configured with wireless network adapters (see below). They also contain a network switch to allow some computers to be connected with Ethernet cables.

Wireless routers allow cable modem and DSL Internet connections to be shared. Additionally, many wireless router products include a built-in firewall that protects the home network from intruders.

Illustrated above is the Linksys WRT54G (compare prices). This is a popular wireless router product based on the 802.11g Wi-Fi network standard. Wireless routers are small box-like devices generally less than 12 inches (0.3 m) in length, with LED lights on the front and with connection ports on the sides or back. Some wireless routers like the WRT54G feature external antennas that protrude from the top of the device; others contain built-in antennas.

Wireless router products differ in the network protocols they support (802.11g, 802.11a, 802.11b or a combination), in the number of wired device connections they support, in the security options they support, and in many other smaller ways. Generally only one wireless router is required to network an entire household.

What Is a Wireless Sensor Network?

Introduction

A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices that use sensors to monitor physical or environmental conditions. These autonomous devices, or nodes, combine with routers and a gateway to create a typical WSN system. The distributed measurement nodes communicate wirelessly to a central gateway, which provides a connection to the wired world where you can collect, process, analyze, and present your measurement data. To extend distance and reliability in a wireless sensor network, you can use routers to gain an additional communication link between end nodes and the gateway.

National Instruments Wireless Sensor Networks offer reliable, low-power measurement nodes that operate for up to three years on 4 AA batteries and can be deployed for long-term, remote operation. The NI WSN protocol based on IEEE 802.15.4 and ZigBee technology provides a low-power communication standard that offers mesh routing capabilities to extend network distance and reliability. The wireless protocol you select for your network depends on your application requirements. To learn more about other wireless technologies for your application, read the “Selecting the Right Wireless Technology” white paper.

WSN Applications

Embedded monitoring covers a large range of application areas, including those in which power or infrastructure limitations make a wired solution costly, challenging, or even impossible. You can position wireless sensor networks alongside wired systems to create a complete wired and wireless measurement and control system.

Figure 1. WSN Application Areas

A WSN system is ideal for an application like environmental monitoring in which the requirements mandate a long-term deployed solution to acquire water, soil, or climate measurements. For utilities such as the electricity grid, streetlights, and water municipals, wireless sensors offer a lower-cost method for collecting system health data to reduce energy usage and better manage resources. In structural health monitoring, you can use wireless sensors to effectively monitor highways, bridges, and tunnels. You also can deploy these systems to continually monitor office buildings, hospitals, airports, factories, power plants, or production facilities.

WSN System Architecture

In a common WSN architecture, the measurement nodes are deployed to acquire measurements such as temperature, voltage, or even dissolved oxygen. The nodes are part of a wireless network administered by the gateway, which governs network aspects such as client authentication and data security. The gateway collects the measurement data from each node and sends it over a wired connection, typically Ethernet, to a host controller. There, software such as the NI LabVIEW graphical development environment can perform advanced processing and analysis and present your data in a fashion that meets your needs.

Figure 2. Common Wireless Sensor Network Architecture

Measurement Speeds and Wireless Throughput

1. Measurement Speeds and Wireless Throughput

Wi-Fi offers higher bandwidth and as the IEEE 802.11 wireless protocol can support much higher sample rates than IEEE 802.15.4 based protocols.  Measurement type, number of measurement channels, and measurement speed will determine the throughput requirements.

For high-speed measurements, Wi-Fi offers additional bandwidth. For instance, 24-bit high-speed acceleration data is sent in 32-bit packets and for 4 channels at 51.2 kS/s the required throughput is 6.6 Mbit/s.  There is some additional overhead for Wi-Fi packets, but clearly the sample rate of 51.2 kS/s requires the bandwidth of Wi-Fi.

 NI WSN is well suited for higher channel count applications.  As an example an NI WSN application with 8 nodes and 4 analog and 4 digital channels per node at 1 second sample interval requires 5.2 kbit/s. The 82 Bytes per sample packet includes packet header information, 4 analog input channels, 4 DIO channels, and channel information such as link quality and battery voltage.

For larger topologies such as a network with four routers and 32 end nodes the total throughput is 44.6 kbit/s.  An important note is that in this topology the 32 end nodes communicate through one of the four routers so the network traffic is doubled from these end nodes.  To calculate throughput in this extended topology multiply the number of nodes in this case, connected directly to the gateway by 1 hop and the number of end nodes connected to a router and then gateway by two hops and add the results.

2. Distance Requirements

Next you need to determine the distance from your measurement to your network access. If the distance is greater than 30 m line of sight, then you need repeaters for Wi-Fi. Even if distances are less than 100 m, RF interference sources including trees or buildings can reduce the achievable distance. To ensure a reliable system, a site survey is recommended for all wireless installations. If required distances exceed 100 m, then IEEE 802.15.4 offers an option with a maximum distance of 300 m line of sight, and with routers the total distances can be extended.

3. Network Topology

Then you need to select the right network topology. To address this, consider the location of access points or gateways and the maximum distance from the network infrastructure to an end node or device. One topology option is a simple star network where a central access point has several end devices connected; this is an ideal configuration for Wi-Fi as long as the distances from access points to devices are less than 30 m. If you need additional distance, a tree topology for which you can use either Wi-Fi repeaters or IEEE 802.15.4 routers helps extend your distance. If network reliability is important, then with an IEEE 802.15.4 mesh network an end node can route packets through multiple routers to a gateway. This provides network reliability in case a router fails.

4. Power Availability

The final consideration when deciding between wireless technologies is power availability. For two- to three-year battery deployments at lower bandwidths, IEEE 802.15.4 is ideal. The central gateway and embedded PC require either 9 to 30 VDC power or solar power; however, end nodes function for several years on standard AA batteries. In Wi-Fi, an access point generally requires power while the end devices are typically powered by DC or solar power for extended operation.

After answering these four questions, you can more easily select the wireless technology that is right for your application. Addressing your application requirements is the first step. For any wireless installation, you should analyze the RF performance at the deployment site. Site surveys conducted by professionals ensure adequate coverage, network performance, and the ability to scale as you add more sensors.

Applications for Wi-Fi-based Wireless Data Acquisition

The higher bandwidth of Wi-Fi at 54 Mbit/s enables wireless data acquisition systems to address high speed waveform measurements such as strain and acceleration.  The trade-off for higher bandwidth is power.  An example wireless data acquisition application is short term strain and stress tests for products in the design or early deployment phases.  This might include a new machine like an agricultural harvester.  Power is available from the engine, and the wireless communication enables faster deployment and flexibility for measurement installations.  Measuring the strain on different components for the harvesting machine allows engineers to verify the design and validate the wear and performance calculations performed during the early design phases.

Applications for IEEE-802.15.4 based WSNs

The low power and longer distance available with IEEE 802.15.4-based networks fits well for longer-term remote measurement applications.  One example is environmental monitoring.  The ability to easily distribute several nodes up to 300 m from a gateway and further extend this distance through mesh routers, makes WSN ideal for monitoring the environmental conditions for a corporate effluent treatment pond.  The system can easily measure the pH, dissolved oxygen concentrations, and water level of the pond.  The battery operated end nodes are easily installed close to the water’s edge without the requirement of local power or communication wiring.  Then data is sent wireless to a gateway with a real-time PC for storage and connectivity to IT infrastructure.

NI Wireless DAQ and Wireless Sensor Networks

If wireless meets your application requirements, you then need to decide between two wireless technologies: Wi-Fi or IEEE 802.15.4-based networks. The trade-off between wireless protocols typically comes down to bandwidth, distance, and power. Wi-Fi has the bandwidth advantage while IEEE 802.15.4 based networks perform better in applications that require longer-distance coverage and lower power. IEEE 802.15.4-based protocols often deliver additional network flexibility with a mesh network topology, which routes packets from end nodes to the gateway through the shortest path available. National Instruments offers measurement devices for Wi-Fi with NI Wi-Fi data acquisition (DAQ) hardware and for IEEE 802.15.4-based wireless sensor networks (WSNs) with the NI WSN product family.

Bandwidth, Range, and Power Requirements

Bandwidth, Range, and Power Requirements

There are three key factors to consider when evaluating wireless technologies: bandwidth, range, and power requirements. When you compare wireless protocols based on IEEE 802.11 and IEEE 802.15.4, Wi-Fi has the advantage in bandwidth with a maximum bit rate of 54 Mbit/s, while 802.15.4 has the advantage in distance and power requirements. This is a typical trade-off made in wireless protocols. Wi-Fi offers significantly higher data rates, which require additional encoding; extra data requires additional radio traffic resulting in increased power consumption by the radio. This bandwidth and power trade-off is obvious in systems such as laptops or smart phones with integrated Wi-Fi that typically operate for a matter of days between recharging and provide high-speed data transfer, compared to a wireless sensor network based on IEEE 802.15.4  technology that might operate for years on standard AA batteries and transfer reduced data between sleep states.

For technologies based on IEEE 802.15.4, this trade-off in bandwidth also results in up to a 10X improvement in distance. At a maximum distance of  300 m and a bandwidth trade-off from 54 Mbit/s to 250 kbit/s, protocols based on IEEE 802.15.4 are ideal for low-speed, long-distance remote monitoring applications, while Wi-Fi is ideal for shorter-distance, higher-power, and higher-bandwidth applications.

Network Topology

In addition to total distance, protocols based on IEEE 802.15.4 offer a couple of options for network topologies. A Wi-Fi system is typically configured in a star topology with a center access point and clients up to 30 m from the access point. While standard Wi-Fi installations support repeaters or routers to extend distance and can be configured in a cluster or tree, they do not support meshing, which is the ability for a node or device to route packets back to the gateway. Many 802.15.4-based wireless sensor networks (WSNs) support star, cluster tree, and mesh networking topologies

Figure . A Star, cluster tree, and mesh networking topologies.

Top Four Questions to Ask When Selecting a Wireless Technology

1.      Which measurements do I need to address my application?
2.      What are the distances from my measurements to my data center or enterprise connection?
3.      Which network topology do I need?
4.      What is the system power source?

Selecting the Right Wireless Technology

Selecting the Right Wireless Technology

Understanding technology capabilities and application requirements is important when selecting a wireless technology for your application. The reasons to choose wireless include reduced installation costs, installation and deployment flexibility, and the ability to address new applications. Before selecting wireless, you first need to ensure the bandwidth available with wireless meets your application requirements. 

Choosing the Right Technology - Wired or Wireless

 

Although the ability to eliminate cabling costs with wireless installations presents potential cost savings, wireless technology must address the application requirements. Two of the main reasons to select a wired protocol are bandwidth and reliability. Standard wired 100BASE-TX Ethernet is faster than both wireless IEEE 802.11g, or Wi-Fi, and IEEE 802.15.4, which provides the basis for ZigBee. When gigabit Ethernet at 1 Gbit/s is included, the bandwidth advantage for Ethernet is clear. If you do not require a bandwidth above 100 Mbit/s, then the cost savings combined with installation flexibility make wireless an effective option.

Eliminate the Wires, Simplify Installations

Eliminating wiring makes it easier and, in some cases, possible to address a broad range of embedded monitoring applications such as environmental monitoring, power monitoring, structural health monitoring, and machine condition monitoring. For National Instruments customers such as the Center for Embedded Networked Sensing (CENS), which needed to collect environmental data from the rain forest, eliminating wire not only reduced costs but also simplified installation challenges. Instead of running power lines and then hauling wire, networking infrastructure, and measurement systems deep into the rain forest, CENS scientists installed a wireless sensor node, batteries, solar panels, and a cellular modem to collect data over the Internet.  They use Google Maps to map node location and document deployment locations.

The University of Texas Ferguson Structural Engineering Laboratory is addressing the problem of monitoring and assessing the condition of bridges. In the case of bridge monitoring, the ability to deploy a wireless system without the overhead of wiring installation allows researchers to reuse hardware from bridge to bridge, which reduces the total hardware costs for measuring bridges that taxpayers fund. The removal of wires also addresses the challenge of vandalism where wires are intentionally cut.

New Technologies, New Applications

Wireless technology works well for many new applications from product design to embedded monitoring. National Instruments wireless sensor networks (WSNs) enable new applications and can improve existing ones. Some possible application examples include distributed measurements along a windmill where the rotating blades and scale of the structures make wiring prohibitive. In another application example, airplane design, the weight of the wiring becomes a significant factor in changing the airplane dynamics and response.

In the area of industrial monitoring, wireless technology presents a new opportunity. What if every piece of critical equipment in a plant provided health data over a wireless network to a central database and then algorithms calculated the time to failure and alerted operators via e-mail or SMS messages? The potential impact on plant uptime and equipment reliability could change the market for equipment manufacturers. If the database were standardized, equipment manufacturers could install the wireless sensor hardware and provide algorithms for time-to-failure analysis, thereby reducing maintenance costs for their customers and increasing the value of their products.

Figure . Application Areas for Embedded Wireless Monitoring

The third generation of wireless adoption currently under way will deliver new technologies that engineers and scientists can use to address new applications and improve existing solutions. To compare the different wireless technologies you can choose from today, read the selecting right wireless Technology white paper about Wi-Fi and ZigBee.

Cut the Wires, Cut the Cost

Cut the Wires, Cut the Cost

It is easy to understand why a wireless approach to remote monitoring costs less in an industry such as nuclear power, where installation costs are estimated to be as high as $2,000 USD per foot. Fortunately, not all applications have such high installation costs. What about other applications such as remote monitoring, structural health monitoring, or asset protection? How do the costs of wireless and wired compare? The answer depends on the application, but you can conduct a baseline analysis if you assume the following:

•         Software investments are equal

•         The costs of line, solar, or battery power are not included

•         The networking infrastructure to enterprise is the same for wired or wireless implementations

The cost remaining is the actual cost of Ethernet with copper or fiber cables and repeaters compared to the cost of a wireless installation. A review of cable suppliers on the Web shows standard CAT 5 Ethernet cable ranges from $260 to $430 USD for a 1,000 m bulk roll. The specified distance for 100BASE-TX Ethernet is 100 m, so reaching 1,000 m requires 10 repeaters at a cost of $30 USD for each nonindustrial unmanaged repeater. Therefore, a 1,000 m run of copper CAT 5 cable costs about $580 USD. With multimode fiber, 100BASE-FX specifies a distance of up to 400 m at 100 Mbit/s, and a 1,000 m stretch of fiber cable costs about $1,300 USD. Three fiber repeaters are necessary at $150 USD each. In total, 1,000 m of fiber-optic cabling costs $1,800 USD. Figure 1 shows quoted cabling costs and repeaters from various vendors. Cabling costs increase for outdoor CAT 5 cable and weatherproof repeaters.

An overview of the cabling costs in Table 1 shows a range from $580 USD for copper Ethernet cable to $1,800 USD for fiber cabling per 1,000 m. This cost does not include measurement devices or PC or embedded control hardware. Eliminating wires with wireless systems provides a clear cost savings in Ethernet cabling.

The Benefits of Wireless Technology

Some of the first applications of wireless technology, developed more than 30 years ago, were led by Wal-Mart for inventory management purposes in the 1980s. The company needed to integrate stocking-level information from hundreds of stores into its business enterprise. This marked the beginning of the wireless scanner, bar-code reader, and, more recently, RFID tag industry. The next wave of wireless adoption was driven by consumers who wanted to take the PC off the desktop. Integrating wireless into laptops drove broad adoption and standardization, and removing wires from the PC allowed PC vendors to attract new customers and address a whole new range of applications. Today, in the third wave of wireless adoption, removing the wires on distributed devices like cell phones and measurement systems offers new levels of mobility. For engineers and scientists, wireless measurement and monitoring systems provide an opportunity to reduce installation and system costs, simplify system deployments, and address a new set of applications that were previously challenging or impossible with wires.

Multiple benefits

Lower device costs

Green Hills royalty-free licensing model is ideal for any wireless devices, eliminating the per unit cost to include this valuable software technology in your embedded devices. Whether you ship 10,000 or 1,000,000 units, you never pay a royalty.

Fast time-to-market

With all of the required software pre-integrated and working together, you don’t need to spend valuable time integrating components. Instead, you can focus on adding the unique features and capabilities that will differentiate your product in the market.

Security and reliability
Both security and reliability are critical when connecting devices over a wireless network. With the Green Hills Platform for Wireless Devices your device can take advantage of the proven security and reliability inherent to the INTEGRITY RTOS. INTEGRITY has an unmatched pedigree for security and reliability that includes multiple certifications by the FAA for flight critical electronics as well as formal methods analysis and NSA penetration testing performed on the security aspects of the OS.

INTEGRITY’s separation kernel architecture provides isolation, protection, and controlled access to system resources like network services, devices and even system memory and CPU cycles. Without these protection mechanisms devices are susceptible to infiltration, loss of critical data, and denial of service attacks. The ability to partition resources such as the drivers, network stacks, and applications makes INTEGRITY the clear choice for building secure and reliable systems.

For protecting data in transit, Green Hills has partnered with Devicescape to bring the gold standard in wireless security together with INTEGRITY. The Devicescape supplicant agent satisfies the supplicant requirements of both WPA and WPA2 standards. It supports both Personal and Enterprise modes and all the EAP methods mandated by the Wi-Fi Alliance for WPA2 compliance.

 

 WPA and WPA2

 

In 2003, the Wi-Fi Alliance introduced WPA to rectify the shortcomings of the original Wi-Fi security mechanism, WEP (Wireless Encryption Protocol). WPA2, introduced in 2004, implements all mandatory elements of IEEE’s security standard, 802.11i. WPA2 is backwards compatible with WPA, which includes a smaller subset of the 802.11i requirements. WPA and WPA2 can be enabled in two modes – Enterprise and Personal. Both modes provide user authentication and encryption of data traffic (see table below).

For user authentication, WPA and WPA2 use Pre-Shared Keys (PSK) in Personal Mode and 802.1x/Extensible Authentication Protocol (EAP) in Enterprise Mode. For encryption, WPA uses the Temporal Key Integrity Protocol (TKIP) whereas WPA2 uses the stronger Advanced Encryption Standard (AES). AES satisfies the Federal Information Processing Standard (FIPS) 140-2 specification, a security requirement of many government agencies.

Choose your wireless devices

Selecting the Right Wireless Technology

Understanding technology capabilities and application requirements is important when selecting a wireless technology for your application. The reasons to choose wireless include reduced installation costs, installation and deployment flexibility, and the ability to address new applications. Before selecting wireless, you first need to ensure the bandwidth available with wireless meets your application requirements.

Exposure difference to mobile phones

Exposure difference to mobile phones 

Mobile phone radiation and health

While users of wireless devices are typically exposed for much longer periods than for mobile phones, the range of wireless devices (and hence their strength) is significantly less. As well, the devices are located significantly farther away from users' heads, resulting in far less exposure overall: The Health Protection Agency claims that if a person spends one year in a Wi-Fi hotspot, they will receive the same dose of radio waves as if they had made a 20-minute call on a mobile phone.

Wireless LAN

EMF levels for WiFi devices are much lower than mobile phones, and there is less public concern about any suggested health issues for wireless LAN devices. Most wireless LAN equipment is designed to work within predefined standards. Wireless access points are also often in close proximity to humans, but the drop off in the already low power over distance is fast, following the inverse-square law. WiFi has been anecdotally linked to electromagnetic hypersensitivity, but no studies have researched this association to date.

The HPA's position is that “...radio frequency (RF) exposures from WiFi are likely to be lower than those from mobile phones.” It also saw “...no reason why schools and others should not use WiFi equipment.”In October 2007, the HPA launched a new “systematic” study into the effects of WiFi networks on behalf of the UK government, in order to calm fears that had appeared in the media in a recent period up to that time". Dr Michael Clark, of the HPA, says published research on mobile phones and masts does not add up to an indictment of WiFi.

Bluetooth

Bluetooth also uses the microwave frequency spectrum in the range of 2.4 GHz to 2.4835 GHz. The radiated output power of Bluetooth devices varies between 1 and 100 mW, and can operate continuously or sporadically (on demand), so total exposure to EMF radiation is quite variable. Bluetooth devices have not been linked with any health issues.

Other devices

Radio frequency in the microwave and radio spectrum is used in a number of practical devices for professional and home use, such as:

• DECT and other cordless phones operating at a wide range of frequencies
• Remote control devices for opening gates, etc.
• Portable two-way radio communication devices, such as walkie-talkies
• Wireless security (alarm) systems
• Wireless security video cameras
• Radio links between buildings for data communication
• Baby monitors

In addition, electrical and electronic devices of all kinds emit EM fields around their working circuits, generated by oscillating currents. Humans are in daily contact with computers, video display monitors, TV screens, microwave ovens, fluorescent lamps, electric motors of several kinds (such as washing machines, kitchen appliances [like electric can openers, blenders, and mixers], water pumps, etc.) and many others. The typical background power of electromagnetic fields in the home can vary from zero to 5 milliwatts per meter squared. Long-time effects of these electromagnetic fields on human and animal health are still unknown, and most of the studies available have shown no effect. However, the powerful fields produced by radio (and then TV) transmitters have been present for more than 100 years now with no established effects on people's health.

Health Research Programs
Extensive research has been conducted into possible health effects of exposure to many types of radio signals.
The consensus of scientific reviews to date is that there are no established adverse health effects from exposures to radio signals at levels below the 1998 guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). When weighing the evidence for potential health effects, scientists consider different aspects before drawing their conclusions:

• Have the effects been reported in the scientific peer reviewed literature?
• Have the reported effects been independently replicated?
• Is there a credible mechanism of action for the reported effects?
• Do the reported effects have any health significance?
• What is the strength of the reported effect?
• Do the reported effects exhibit a dose-response relationship?
• Is the study 'hypothesis testing' or 'hypothesis generating'?
• Have the statistical analyses of the results been conducted properly?
• Are there more obvious explanations for the reported outcomes?
• How does this study fit into the total existing research body?
  
  

The World Health Organization (WHO) has identified areas for continuing research to support future health risk assessments. Many research programmes have been guided by the WHO research recommendations for electromagnetic fields and the WHO estimates that since 1997 over US$200million of funding has been allocated to such programmes.

Wireless electronic devices and health

The World Health Organization has acknowledged that electromagnetic fields (EMFs) are influencing the environment (but not people), and that some people are worried about possible effects.[1] In response to public concern, the World Health Organization established the International EMF Project in 1996 to assess the scientific evidence of possible health effects of EMF in the frequency range from 0 to 300 GHz. They have stated that although extensive research has been conducted into possible health effects of exposure to many parts of the frequency spectrum, all reviews conducted so far have indicated that exposures are below the limits recommended in the ICNIRP (1998) EMF guidelines, covering the full frequency range from 0-300 GHz, and do not produce any known adverse health effect.

International guidelines on exposure levels to microwave frequency EMFs such as ICNIRP limit the power levels of wireless devices and it is uncommon for wireless devices to exceed the guidelines. These guidelines only take into account thermal effects, as nonthermal effects have not been conclusively demonstrated.[2] The official stance of the Health Protection Agency is that “[T]here is no consistent evidence to date that WiFi and WLANs adversely affect the health of the general population.” And also that “...it is a sensible precautionary approach...to keep the situation under ongoing review

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