What is the difference between bandwidth, bit-rate and latency?

In the world of high-speed internet, terminologies like bandwidth, bit-rate, and ping are used frequently. In some cases, we even hear slightly more technical terms like latency, frequency, interference, throughput and possibly others. However, a normal internet user who mostly cares about speed may find it challenging to interpret these terminologies, especially when making a decision such as buying a broadband service. In this post, we aim to demystify some of these buzzwords to help you understand these concepts in plain English.

What is a wireless broadband signal?

As you may know, there are at least two fundamental types of wireless broadband services; fixed wireless broadband and mobile broadband. Fixed wireless is the most well-known option that requires a fibre or ADSL lin to your house or area and then a WiFi router inside the house to create wireless internet coverage. With the advent of 4G and 5G cellular technologies, the other option that is becoming popular is mobile broadband that requires a SIM card to be inserted inside a mobile WiFi router to create wireless internet coverage. So basically, irrespective of which wireless broadband option you go with, you are provided with a router (or modem or hub) to create wireless internet coverage through WiFi. The diagram below shows a simplified conceptual view of how fixed and mobile broadband signals reach our houses. For fixed broadband services, a cable runs to our house either directly or through the telephone line, which can then be connected to a router that generates WiFi coverage. Mobile broadband can also use a SIM-enabled router or even a mobile phone to create a WiFi hotspot. A mobile WiFi router is a preferred option because it is purpose-built and supports more advanced WiFi capabilities than a mobile phone.

Conceptual view of fixed and mobile broadband services reaching our houses - In both cases, there can be a WiFi router to convert the fibre or cellular connection into WiFi signals
Conceptual view of fixed and mobile broadband services reaching our houses – In both cases, there can be a WiFi router to convert the fibre or cellular connection into WiFi signals

The WiFi coverage basically means that your devices, such as laptops, smart TVs etc., can communicate with the router by sending and receiving wireless signals. These signals are sent at specific frequencies so that a single router can communicate with all your internet-capable devices at the same time without any interference. If the router were using the same frequency to communicate with all your devices, it would cause interference which would essentially make your broadband service unusable. You may have come across the 2.4 GHz and 5 GHz frequency bands that your router supports. A frequency band, e.g. the 5GHz band, basically means that the router can create multiple channels in the 5GHz frequency range o establish communication links with various devices. For example, the router may use a channel ranging from 5.170 GHz to 5.190 GHz to provide WiFi to a certain laptop. This range is called channel bandwidth which we will cover in the next section.

What exactly is bandwidth?

The bandwidth of a signal refers to the range of frequencies used for sending and receiving that signal. In the above example, the range starts from a lower frequency of 5.170 GHz and goes up to 5.190 GHz. The difference between these two frequencies, i.e. 0.020 GHz or 20 MHz, is the channel bandwidth. This bandwidth represents the available capacity to transmit wireless signals between the router and a specific device at any particular time. The router can switch channels when serving devices, and it is also possible to create bigger channels by combining multiple channels. The bigger the bandwidth of a channel, the more data it can accommodate. However, a higher frequency band, e.g. 10 GHz, does not necessarily mean that you will get higher data rates. The range of frequencies within that frequency band determines what data rate you are likely to achieve – the higher the range of frequencies (bandwidth), the higher the data rate can be.

Bandwidth is measured in Hertz (Hz) just like frequency because it is just a difference between two frequencies that define the range. The channel’s bandwidth determines how much capacity is available on that channel to send or receive information (data). The required capacity for a certain channel is dependent on the amount of data being transmitted (upload) or received (download). For example, if you are streaming a video on YouTube, you will consume a lot more data than updating a post on Facebook. As a result, the required capacity and bandwidth for streaming a video would be a lot higher than updating a Facebook post.

What is bit-rate?

The term bit rate refers to the quantity of data being transferred from one part of the network to the other in a certain amount of time. The data is measured in bits and the time, in this context, is measured in seconds. As a result, the unit of bit rate is bits per second. Since a lot of bits are required to transmit and receive data, the most common unit of bit rate at the point of writing (2021) is Mbps or Megabit per second which essentially means 1 million bits per second. Things may change when the 5G technology matures, and we may start measuring the bit rate in Gbps, but we will have to wait for some time to find that out. ‘Bit’ is closely related to another unit called ‘Byte’ and 1 ‘Byte’ has 8 ‘Bits’ in it. The data speeds are usually measured in bits per second e.g. 2 Mbps or 5 Mbps, but the size or volume of data is measured in bytes e.g. 2MB or 3GB. So to put this into perspective, the upload and download speeds that you get on your mobile network will be expressed in Mbps. On the other hand, your monthly data allowance will be expressed in MB or GB (e.g. 10GB).

The bit rate can be seen as a measure to compare technologies in terms of their capability to transfer data; for example, 4G LTE Advanced Pro offers a much higher bit rate than the regular LTE. But for internet users, the bit rate is seen mostly as the upload and download speeds they get when using the internet. In mobile communications two terminiologies uplink and downlink are used very frequently – uplink bit rate helps with the upload and downlink bit rate helps with the downloads.

What is latency, and is it different from bandwidth and bit-rate?

If you run a speed test for your broadband connection, you are likely to see latency or ping alongside the download and upload bit rates. Unlike download and upload bit rates where you want to see a bigger number, ping and latency are ‘delays’ so ideally, you want to see a lower number. If you do a lot of online gaming, then latency is an important consideration and can be the difference between winning and losing. Many broadband service providers offer data rates in the multiples of 100 Mbps but if the latency is high, the experience won’t be great. The bit rate is the amount of data that can be transferred in a second whereas the latency is how long it takes for a packet to reach from source to destination. For example, if someone sends you an email with a large video file and you click to download it:

  • The amount of data you download per second is the bit rate usually represented in Mbps or Gbps.
  • The allocated channel’s capacity, i.e. the maximum size of the data pipe allocated for download or upload, is the bandwidth. Usually, larger bandwidth equates to a higher bit rate.
  • The time it takes (in milliseconds) for your download request to trigger a response from the server is the network latency.
  • The time it takes for your download request to trigger a response and then for you to receive the first bit/packet of the response is the round trip time (RTT).
  • Ping, which is often used interchangeably with latency and round-trip time, is a utility that allows calculating round-trip time.

So to sum up…

The bandwidth determines how much capacity is available on a certain channel to send or receive data. The bit-rate is the amount of data (in bits) transferred in one second. Latency is the time it takes from when a user requests a response (e.g. click a link) to when the server triggers a response. The round-trip time is the sum of latencies in both directions, i.e. user to the server and then back.

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