Bandwidth, bit rate and latency are interrelated concepts in telecommunications that are important to understand. In mobile communications, especially 4G and 5G networks, these concepts can help you know how fast a particular technology is compared to the other.
Bandwidth is the available channel capacity for sending or receiving data, the bit rate is the amount of data transferred in one second and latency is the time it takes for a user to get a server response. Bandwidth is expressed in Hertz (Hz), bit rate in Mbps or Gbps and latency in milliseconds (ms).
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 an important decision such as buying a broadband service. In this post, we aim to demystify some of these buzzwords to help you understand internet speed-related concepts in plain English.
What is bandwidth?
The bandwidth of a frequency channel is the range of frequencies used for sending and receiving data. For example, if a Wi-Fi router uses a frequency channel ranging from 5.170 GHz to 5.190 GHz, the channel bandwidth will be 0.020 GHz or 20 MHz, which is the difference between the two frequencies.
In the above example, the channel bandwidth represents the available capacity for transmitting 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. In mobile communications, the technology that allows the 4G and 5G networks to combine multiple channels is called Carrier Aggregation, which is a key component of LTE and NR networks. 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 (bandwidth) determines what data rate you are likely to achieve. The higher the bandwidth, the higher the potential data rate.
How is the bandwidth of a channel measured?
The bandwidth of a frequency channel is measured in Hertz (Hz) or MHz, which is the unit of frequency. Bandwidth is essentially the difference between two frequencies in a given range which is why it has the same unit as frequency.
The bandwidth of a channel determines how much capacity it has 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 is measured in seconds. Therefore, the bit rate is measured in bits per second (bps).
Since a lot of bits are required to transmit and receive data, the most common unit for 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 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 terminologies, 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 how is it different from ping?
Latency is the time it takes for your download request to trigger a response from the server (e.g. YouTube); ping measures the round trip time, which is the time your download request takes to trigger a response from the server plus the time it takes for you to receive your first bit (data packet).
Latency and ping are inter-related concepts that you encounter when running speed tests for your internet. For example, if you run a speed test for your home 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 smaller number. If you do a lot of online gaming, latency is an important consideration and can be the difference between winning or losing. Many broadband service providers offer data rates in multiples of 100 Mbps, but the experience won’t be great if the latency is high. 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.
All wireless networks use bandwidth, bit rate and latency
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 line 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, another option that is becoming popular is mobile broadband, which 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 Wi-Fi hotspot. A mobile WiFi router is the preferred option because it is purpose-built and supports more advanced Wi-Fi capabilities than a mobile phone.
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 to 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 connectivity to a certain laptop. This range is called channel bandwidth which we will cover in the next section.
An example for bit rate, bandwidth, latency, RTT and ping
Let’s use an example to understand the difference between bit rate, bandwidth, latency, round trip time (RTT) and ping. Suppose someone sends you an email with a large video file, and you click to download it. The bit rate, bandwidth, latency, round trip time and ping will be:
|Mbps or Gbps
|Bit rate is the amount of data you download in one second. The higher, the better.
|MHz or GHz
|Bandwidth is the size or capacity of the frequency channel allocated to you for downloading and uploading. It is the data pipe available to you to download or upload. The higher, the better.
|Latency is the time it takes (in milliseconds) for your download request to trigger a response from the server. The lower, the better.
|Round trip time (RTT)
|RTT is 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. The lower, the better.
|Ping is a utility that calculates the round trip time and is always higher than the latency. The lower, the better.
Bandwidth, bit rate, latency and ping are relevant concepts for mobile and fixed internet speeds. The more advanced broadband technologies are expected to have higher bandwidth and bit rates, and lower latencies and ping. The bandwidth determines how much capacity is available on a certain channel to send or receive data and is expressed in Hertz (Hz). In real-life, the bandwidth is measured in Megahertz (MHz) or Gigahertz (GHz). The bit rate is the amount of data transferred in one second and is expressed in bits per second (bps, kbps, Mbps, Gbps). Latency is the time it takes from when a user requests a response (e.g. when a user clicks 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. Latency, round-trip time and ping are measured in milliseconds.
Here are some helpful downloads
Thank you for reading this post. I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need extra support, especially when preparing for a new job, studying a new topic, or buying a new phone. Whatever you are trying to do, here are some downloads that can help you:
Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.
Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.