Glossary

In a similar fashion as changing your speed while driving as the road and weather conditions change, radios equipped with adaptive modulation can change their speed (modulation rate) as radio propagation conditions change causing interference. Building adaptive modulation into a radio allows each radio in a network to act independently. Only the radio(s) experiencing interference will decrease their modulation rate (e.g. from QAM256 down to QAM64 or QAM16) while the other radios in the system will continue to operate at the highest possible modulation rate. Decreasing the modulation rate slows down the transmission rate of the data and therefore increases the probability that the transmission will be received successfully. The overall benefit of Adaptive Modulation therefore, is that it creates higher reliability across the network due to the fact each radio maintains its independence.

Full duplex communication is where the uplink transmissions (from the field device to the base station) and downlink transmissions (from the base station to the field device) can be active simultaneously and operate independently of one another. Simply put, full duplex communications enables a radio to transmit information AND receive information at the same time. Half duplex radios can either transmit information OR receive information at one time. A commonplace example of full duplex communications is a telephone call where both parties can communicate at the same time.  Half duplex, by comparison, would be a walkie-talkie conversation where the two parties take turns in speaking.

Simply put, latency is the time it takes for a bit of data to go from one endpoint to another in a network. In radio systems, latency is measured in fractions of a second - typically in milli-seconds (one one-thousandths of a second). Each radio must process the data it transmits and receives, so latency is inherent in all radios. For certain applications, the latency of your system needs to be very low as delays could impact your business quite significantly. Having low latency in a radio system offers tremendous benefits in that one radio system can support a wider variety of applications in an organization including those with low and high latency needs. Also, having lower latency radios means the system has more time for sending data, resulting in a greater system capacity.

MIMO (Multiple Input, Multiple Output), is an advanced radio technology which increases the capacity of a system without requiring more spectrum. Each MIMO radio has multiple transmitters and receivers and is capable of transmitting and receiving multiple signals on the same frequency at the same time. This is compared with traditional SISO technology where only one signal is sent. A MIMO radio with 2 transmitters and 2 receivers would therefore offer up to two times the capacity of a SISO based radio since it would be able to transmit and receive twice the amount of information at one time.

MIMO antennas are commonly used in certain areas of wireless communications, including the cellular markets. In the narrowband space where critical infrastructure industries operate, however, MIMO and MIMO antennas are not very well understood. A MIMO antenna is fairly similar to a SISO antenna but instead of having one input and one set of elements the MIMO antenna has multiple inputs and multiple elements. The use of a MIMO antenna requires a second transmission line but this is offset by the significant benefits achieved when using MIMO-based technology - namely an incredible performance boost, greater link reliability and tremendous cost savings to an organization.

The modulation rate a radio uses simply defines how many bits per symbol per transmission it can achieve. The amount of data that a radio can transmit at one time is measured in “bits per second”. Radios, however, do not transmit a long stream of bits (0s and 1s), but rather they transmit a symbol that represents a bit or a group of bits. Early modulation techniques only allowed each symbol to represent one bit but, as technology improved, newer modulation techniques were developed that allowed each symbol to represent 2, 4, 6 or even 8 bits of information. The more bits that can be represented by a signal, the more data can be transmitted. Mimomax supports QAM256 modulation which provides 8 bits per symbol – a 30% increase over QAM64. This increases the capacity which can be achieved, thereby maximizing ROI on your investment in spectrum and hardware.

The Output Power of a radio can be a difficult aspect to compare accurately. It is therefore important to determine first how each radio manufacture has presented their values. Key elements to be aware of are: 1) That peak power vs average power may differ significantly. Presenting a peak power figure can be misleading as the radio will generally not be operating at peak levels. 2) As higher modulation rates are used, the power must be turned down to limit the radio interfering with adjacent channels. Therefore, to make an accurate comparison, you must ensure the figures quoted relate to the same modulation rate being used. 3) Full duplex radios have built-in duplexers and quoted output power figures will account for loss from the duplexer. Half duplex radios with after-market duplexers may have their output power rates quoted without the loss from the duplexer, cabling and connectors being calculated.

Radios have long used just a single transmitter and receiver in each radio to communicate data from one device to another. These traditional single transmitter & single receiver radio systems are referred to as SISO (Single Input, Single Output) systems. Since each radio only has one transmitter, these traditional systems are only able to transmit one stream of data at a time.

Spectral efficiency simply means to efficiently use the spectrum you have by pushing more data through the channel. Compare it to a pipeline taking oil from point A to point B – the more oil you can get through the pipe, the more efficiently you are using your pipeline resource, thereby increasing your return on investment in installing the pipe. When talking about radio communications, many advancements have been made in technology which enable more data to be pushed “through the pipe”. Such technology advancements include MIMO, QAM Modulation and full duplex communications.