An introduction to wireless technologies in health

The number of times the radio wave cycles in one second. In general, the more times the signal cycles in a second, the faster it can transmit data.  A very crude but effective analogy is to imagine you are on a trampoline; each jump up and down you do back to your starting point is called one cycle. The number of cycles (jumps) you can do in one second is measured and called Hertz, abbreviated to Hz. This is what we refer to as the frequency. So, a frequency of 5Hz means you are cycling (jumping) five times in one second. Now, imagine you want to give some instructions to someone, but you can only spell out each letter of each word one at a time.  You can say one letter when you are at the very top or bottom of each jump up.  The more jumps you can do in one second means you can spell out the words faster. Hence, the higher the frequency the faster the data rate.  For wireless radio, frequency is generally in the Mega Hz, MHz (million times a second) or the Giga Hz, GHz (billion times a second). 

As a general rule, the higher the frequency, the harder it is for the signal to pass through objects such as walls. This is especially relevant for the GHz ranges.

When you send a radio signal it needs some power in order for it to transmit.  The higher the power the further the distance it can travel. In the trampoline example above, the power would be how loud you shout the letters out. If you are whispering, similar to having low power, then only people very near you will hear you but you use less energy.  If you shout, like high power, then people at the back of the room will also hear but you will run out of energy sooner.

The allocation of frequencies and their associated power outputs are governed by each country’s government. In the UK it is Ofcom, in Europe it is ETSI and the USA is FCC.  These bodies grant licenses to organisations so only they can use a given frequency in an area along with a maximum power output. These are called the licenced bands and prevent organisations using the same frequency.  There are also frequencies that are unlicensed that can be used by anyone.   However, as they are open to anyone, there can be a lot of congestion resulting in low connectivity.  Power limits are also set for both licensed and unlicensed bands.

Competing wireless technology can sometimes use the same frequencies resulting in radio congestion.  This is more common in the unlicensed 2.4GHz range as it has been available for use for many years.  Not only do wireless radio systems compete for this range, it’s also susceptible to interference from other electronic devices such as microwave ovens. To help alleviate this, newer unlicensed bands have been opened in the 5 and 6GHz ranges.  However, as these are higher frequencies they cannot travel as far or penetrate walls as much as 2.4GHz so careful planning is needed.

This is a measure of how quickly information can be sent. It’s measured in “bits” which has a very specific meaning in the electronics arena, but for the purpose of this document just think of it as a single piece of information.

In the trampoline example above, for each jump you do you are sending out two pieces of information, a letter at the top and the bottom of the jump. If you are doing five jumps a second, then you are transmitting 10 pieces of information. 

This would give you a throughput 10 Bits per second,10bps In the electronics world there are various methods where each cycle (jump) can carry many bits of data, 64 bits per cycle is possible and throughput is usually measured in Mega (million) bits per second (Mbps) or Giga (billion) bits per second (Gbps). Also worth noting is that not all of the information sent is your actual data, there is a lot of information also sent that control the data signal.

This is short for Local Area Network and generally refers to the network within a building, commonly the network your device connects to.

This is short for Wide Area Network and generally refers to the network that links multiple buildings together. User devices don’t generally connect directly to a WAN device.