What is High Speed Packet Access (HSPA)?

Have you ever noticed the ‘H’ or ‘H+’ sign on your mobile phone screen when using mobile internet? That is HSPA or High-Speed Packet Access. When you see this sign on your mobile phone, you can expect decent mobile data speeds but keep in mind that HSPA is not 4G.

High-Speed Packet Access (HSPA) is an enhancement introduced in 3G UMTS mobile networks to enable high-speed internet through 3G SIM-enabled cellular devices. HSPA is a combination of HSDPA and HSUPA and can provide peak download speeds of up to 14.4 Mbps and peak upload speeds of up to 5.76 Mbps.

HSPA is a combination of HSDPA and HSUPA

The original 3G UMTS networks (Universal Mobile Telecommunications Systems) can provide peak downlink speeds of up to 2 Mbps and peak uplink speeds of up to 128 kbps. HSPA was introduced in the UMTS networks to increase the download and upload speeds. It is a combination of two inter-related technologies HSDPA (High-Speed Downlink Packet Access) and HSUPA (High-Speed Uplink Packet Access). The word ‘downlink’ in HSDPA suggests that high-speed data is only available in the downlink. As we know, the downlink is the link that allows a cellular base station to communicate with a mobile phone. So, high-speed in the downlink will allow users to be able to download data such as files, documents, videos, etc. much quicker.

Uplink, on the other hand, is what enables communications from the mobile phone back to the cellular base station. Therefore a high-speed connection in the uplink improves the upload speeds. This is where HSUPA comes in which is the counterpart of HSDPA in the uplink direction. HSDPA delivers peak downlink speeds of up to 14.4 Mbps to help with the downloads and HSUPA enables peak uplink speeds of up to 5.76 Mbps to improve the upload speeds. HSDPA and HSUPA collectively are known as High-Speed Packet Access or HSPA.

On your mobile phone screen, HSPA is shown as the ‘H’ symbol. There is also a more enhanced version of HSPA called Evolved High-Speed Packet Access or HSPA+. HSPA+ is a technology upgrade to HSPA and it can provide peak downlink speeds of up to 42 Mbps and peak uplink speeds of up to 11.5 Mbps. HSPA+ is shown on your mobile phone screen as ‘H+’.

In CDMA2000 networks, a technology called EVolution Data Optimized (EVDO) is used to enable high-speed internet services. EVDO is an equivalent of HSPA in the CDMA networks. Purely for comparison purposes, EVDO can offer peak downlink speeds of up to 14.7 Mbps and peak uplink speeds of up to 5.4 Mbps. More information on EVDO can be found in our post What is EVDO?

How HSDPA and HSUPA work

HSDPA and HSUPA use slightly different approaches to enable high-speed data services in the UMTS networks. HSDPA introduces a new high-speed downlink channel that can be shared among multiple mobile users. It uses a transmission duration of only 2 milliseconds as compared to over 10 milliseconds in UMTS (Release 99). With this approach, HSDPA can be really quick when it comes to switching users as it is a shared channel. This short transmission duration also allows HSDPA to respond quickly to the continuously changing radio network conditions. It also uses faster data traffic scheduling in order to allocate most of the available capacity to a single user so that they can receive high-speed data in a very short space of time. HSDPA also uses superior modulation and coding techniques as well as faster re-transmission of erroneous packets.

As a result, mobile users get to enjoy faster download speeds as compared to the original UMTS networks. Unlike HSDPA, HSUPA uses a dedicated channel to add a new radio interface for uplink communication. Just like HSDPA, HSUPA also uses a faster re-transmission technique to enable high-speed uploads.

Average data speeds with HSPA/HSPA+

Now you might be wondering why you don’t often get the above speeds when you are on HSPA networks? The above speeds are peak speeds and not the average ones. We don’t usually get peak speeds because the cell within the network serving us also serves many other mobile users simultaneously. The network coverage (signal quality) can also impact the data speeds. Below are some examples of randomly selected indoor locations in the UK (Reading) to give you an idea of what average speeds and latency you can expect from HSPA+ (H+). There is also a short video at the end of this article that summarises HSPA.

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 some extra support, especially when preparing for a new job, studying a new topic, or maybe just 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.

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