The concepts of wireless networks and related forms of communication have been seen as a great innovation ever since they were developed in the 1990s, and a remarkable leap forward in the field of technologies, which is precisely why most specialists in gadgets and devices consider them to be the main reason behind the current revolution in the world of industrial communication. And what do you think stood at the forefront of this revolution? The answer is none other than the amazing modems and similar devices. Regardless if you want to know more about the use, way of functioning or applications of a radio modem on SRD bands or any other similar technology, there are some basic facts and main characteristics shared by these products which can be seen in each and every particular device. Stick with us as we are about to show you in full detail what radio modems are and how they have brought change to our surrounding environment.
A digital radio modem, also referred as radio transceiver, is used to transmit data over short distances without a physical wire or connection, but rather basing the transmission of information on wireless systems sending the data to another device of the same type in a multipoint or a point-to-point link. Their range differs greatly according to the transmission power, environment, antenna gain and could be affected by radiofrequency pollution (other systems transmissions) or multipath fading in close environments. If it is used hundreds to thousands Watts emitting radio modems, the maximum range of 100 kilometres can be achieved, as long as the environment is favourable (curvature of Earth at certain distances should be kept into account). However, much broader regions are usually covered by implementing radio modem repeaters.
For Building Automation or Industrial applications, the same considerations of the open-fields radio transmissions are applicable, but other tricky phenomena should be faced. Even if the ranges to be covered are shorter, from tens to hundreds meters, two main interactions with the buildings and the objects inside its environment affect the radio transmissions decreasing the level of the signal at the receiver device side and making the radio links less reliable
1. Obstacles (walls, doors, furniture, floors, ceilings, people, household appliances) absorption;
2. Obstacles multipath, that is a multiple reflection of the same signal that arrive in different copies to the receiver at the same time. This multiple reception of different un-phased copies of the same signal could decrease greatly the signal strength.
The last phenomena is particularly insidious because the changing of the radiofrequency patterns, that could be caused simply by people or furniture movements, could drop down a radio link, that seemed to be robust enough, losing the control of a remote wireless device. Just very recently some high performant SRD radio modems offered antenna diversity that can mitigate or even transform into advantages the indoor multipath phenomena. In fact, statistically, the multipath phenomena at the reception side creates areas on which the signal is stronger and other on which the signal is weaker; these contiguous and alternate areas distance is more or less equal to 10-30 cm at SRD band frequencies. Antenna diversity technology allows the receiver to receive from two antennas at the same time the initial part of a data packet and choose from which of the two is more convenient to receive all of it. If the antenna are conveniently placed at 10-30cm distance each other at least the signal will be strong enough from one of them. This increase the level of the signal from 10dB to 15dB in average and could make a big difference: a wireless device not lost means that we can still control a radiator, have measures from a thermostat or from a portable biomedical device applied to patients in a hospital.
For Building Automation and Industrial or Medical application some of the characteristics that should be properly evaluated are here listed:
– Maximum data rate
– Maximum data packet length (bytes)
– Possibility to modulate the RF power
– Possibility to change frequency(channel
– Possibility to change bandwidth
– Possibility to skip buffering at transmitter and receiver side avoiding decreasing of real data rate performances
– Receiver sensibility
– Antenna diversity
The possibility to change the bandwidth consequently with the data rate is very important to not waste on occupancy of radio frequency. In fact, if the radio modem allows at changing the bandwidth, it is possible to decrease it when lower data rates are used gaining increasing the number of independent radio channels.
There are many other interesting facts and information that should be known about the world of wireless transmissions, regardless of their working frequency and power. These facts include the details about private wireless modems such as normative considerations (use unlicensed or licensed frequency bands) or the internal different stages of the communication, which are, at high level perspective, data encoding first, data transmission secondly and, lastly, data reception. Furthermore, these communication devices are subsystem of a higher level hosting device and need to communicate with this. External radio modem, generally radio working at high power, include RS422, RS485, RS232 or USB; while for SRD bands application, whose modems are small as a stamp and are generally welded on the hosting device PCB, UART or SPI interfaces are used.
Other applications of these communication technologies include, but do not stop at: video security, mining, city bus fleets monitoring and the oil and gas industry or even long distance sports and many more activities which require the participants to have a constant line of communication opened between them.
Being at the front edge of the modern revolution in technologies, wireless and radio systems are an amazing discovery which has tremendously influenced the world we live in. the modern day industrial radio modems are used to encode the data, after which it is transmitted and finally decoded. Their technology is based on the use of radio waves as a means to transmit the information, which has brought a large improvement in comparison to the formerly used types of wired data. As a final point, the applications of these technologies are so vast that they have been called unlimited by experts in the field, meaning that the user’s creativity is the only thing standing in his way.