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Remote Connection Options

 

QUESTION

I want to connect to a vbOnline device at a remote site. What connection options do I have?

ANSWER

There are currently several options for remote monitoring of vbOnline devices with more under development. The option you choose will depend on several factors:

  • The number and type of vbOnline devices being installed
  • The distance between the operator PC and the vbOnline devices
  • The existing infrastructure, such as Ethernet cabling, WAN access etc


1. Short Range WiFi (up to a few hundred meters)

WiFi technology can be used to create short-haul, high-bandwidth wireless links (generally up to a few hundred meters or so, depending on the equipment used and any obstacles in the path of the link). This is useful in situations where there is no existing Ethernet cabling, or the vbOnline device is in a mobile installation. The WiFi link can be an 'ad-hoc' connection between a vbOnline device and a single PC with a wireless network interface, or an existing LAN can be given WiFi connectivity with the addition of a WiFi router. A vbOnline device may also be given WiFi connectivity with the addition of a WiFi router; however, Commtest Instruments have a vbOnline variant with WiFi built-in, the vbOnline-Wifi.



2. Long Range WiFi (up to several kilometers)

A WiFi link can be extended considerably with the use of readily available high-gain directional antennas. This is ideal for installations that have several isolated vbOnline devices scattered over a wide area. The range will depend on antenna gains and elevation; however, distances of several kilometers are feasible. Each vbOnline-WiFi device would be equipped with a directional 2.4GHz antenna, aligned with an omnidirectional antenna connected to a WiFi router at the operator PC end of the link.



3. Point-to-Point RF Modem

If a simple point-to-point wireless link with a single vbOnline is all that is required, an excellent option is a pair of RF modems. One of the pair is connected to a serial port on the operator PC, and the other is connected to the serial port of the vbOnline device. The important factors in the choice of RF modem are as follows:

  • Range: the modems must be capable of transmission and reception over the distance required.
  • RF Link integrity: modems that communicate via digital or 'packetized' protocols employ sophisticated error correction techniques to ensure data integrity is preserved 'over the air'.
  • Automatic connection: the modems should be able to be configured to auto-connect on detection of serial port activity, without operator intervention.


An example of a good choice for this type of application is the Aerocomm ConnexLink CL4424-100.



4. WAN Connection with Static Gateway

If your company has a dedicated WAN with a static IP addressing scheme that spans the operator and remote sites this may be used to link the operator PC with the vbOnline devices. A dedicated WAN will typically use media such as Frame Relay, ISDN or a permanent satellite circuit. Care should be taken to ensure each vbOnline device is configured with a valid IP address and the correct subnet for the network.



5. WAN Connection via the Internet

(dynamic gateway, single vbOnline device)

If the vbOnline device communicates with the operator PC through the Internet, the IP address of the gateway through which the data must pass will almost certainly be dynamically assigned and therefore will be subject to change without warning. Since the operator PC must have an address to talk to the vbOnline device the device LAN gateway must make use of a Dynamic DNS service (such as NoIP or EasyDNS). This in turn means that such a gateway needs to be either a PC configured as a router running a DDNS client, or a DDNS-capable router such as the D-Link DI-604. The operator will then have a fixed, fully qualified domain name to use to communicate with the vbOnline device.

Note: This configuration makes use of port forwarding, a technique whereby traffic delivered to the router WAN interface on a particular port is forwarded to an internal IP address (in this case the vbOnline device). This functionality is built into the router but can only provide service for a single online device.



6. WAN Connection via the Internet

(dynamic gateway, multiple vbOnline devices)

If there are multiple vbOnline devices at the remote site, a Virtual Private Network (VPN) must be used. A VPN server provides a secure traffic 'tunnel' from the Ascent PC to the internal router network, effectively making the Ascent PC part of the internal network. This allows the vbOnline devices to be addressed by their internal IP addresses, which are normally 'hidden' by the router. The router must support VPN Pass through to allow the VPN traffic to reach the VPN server.



7. WAN Connection via Cellular Network

Recent developments in merging cellular and Ethernet network technology have resulted in the cellular router, a device with both an Ethernet interface and data connectivity to GSM or CDMA cellular networks. A cellular router offers a way of setting up a long distance link to your vbOnline device(s) in areas where there is no existing internet infrastructure, or no desire to go to the hassle and cost of setting up a permanent internet link. A hub may be required if multiple vbOnline devices are at the remote end, and your router has only a single Ethernet interface.

Care should be taken to select a cellular router compatible with the cellular networks available where it will be located. Some vendors offer similar models for both GSM and CDMA, for example the Airlink Raven E.

Sending data over cellular networks is generally charged for by volume rather than transmission time. It would be a good idea to estimate your traffic volume (set x frequency) and then get corresponding cost information from your provider. Below is a list of typical measurements and their sizes in bytes (values for other measurements can be extrapolated from this information):

  • 400 line spectrum ~1k
  • 800 line spectrum ~2k
  • 1024 sample waveform ~2k


The traffic volume figure will be approximate due to network and protocol overhead, but will be good enough for you to make an informed cost estimate.



8. Fiber Networks

Fiber optic networks are used in applications that require high-bandwidth network connections over long distances, or electrical isolation for safety reasons. A vbOnline device can be readily connected to this type of network by employing a media converter. This is an external device that has both an RJ-45 ethernet interface, and a fiber optic interface (typically 100BaseFX). The media converter transfers packets between the two interfaces.

Fiber to ethernet media converters are available in DIN rail-mountable form factors, and can generally be powered from the same DC supply that powers the vbOnline device. A typical example is the EIR102-MT from B&B Electronics. Media converters are also available from Black Box.

Future Developments

We encourage customers to indicate their interest in alternative connection technologies. Additional connection options, such as GPRS and CDMA modems, will be supported based on customer demand.