The term Gigabit LTE is often used in the context of 5G mobile networks, and it can be hard to differentiate it from 5G if you are not familiar with the cellular technologies that enable 4G and 5G. 5G stands for the fifth generation of mobile networks, whereas Gigabit LTE is linked to fourth-generation (4G) LTE networks.
Gigabit LTE or Gigabit Class LTE is a milestone that represents the ability of mobile cellular devices to deliver peak data rates of 1 Gbps when connected to 4G LTE Advanced and LTE Advanced Pro networks. 5G is enabled by New Radio (NR) which is superior to the LTE technology that Gigabit LTE uses.
How is Gigabit LTE linked to the 4G LTE technology?
All technological enhancements in the mobile communications industry for GSM, UMTS, LTE and NR network technologies are based on specifications from 3GPP or 3rd Generation Partnership Project. For any mobile cellular technology to work, it must be supported by both the network and the device.
The Gigabit LTE milestone is based on the premise that a mobile network can deliver peak data rates of up to 1 Gbps. In 4G LTE networks, the enhancements that allow a device to achieve peak data rates of at least 1 Gbps are LTE Advanced and LTE Advanced Pro. These cellular technologies employ a range of frequency and antenna related technologies to increase the achievable data rates. These techniques include carrier aggregation, QAM (Quadrature Amplitude Modulation) and MIMO (Multiple Input Multiple Output).
In simple terms, carrier aggregation is a technique that allows a mobile network to combine multiple channels (carrier frequencies or carriers) into one to increase the overall bandwidth and associated bit rates. QAM is a digital modulation technique used in modern mobile and Wi-Fi networks to efficiently extract higher bit rates from the available frequency channels. MIMO is an advanced antenna technology that uses multiple antennas to transmit and receive mobile signals to improve the bit rates and signal quality.
Carrier aggregation, QAM and MIMO have specific configurations that are directly proportional to the data rates a mobile device can expect to achieve. As a general rule, the higher the MIMO, carrier aggregation and QAM configurations, the better the likelihood of achieving higher data rates.
The table below summarises the carrier aggregation (CA), MIMO and QAM configurations for 4G LTE, LTE Advanced, and LTE Advanced Pro. LTE Advanced Pro is the latest enhancement with the highest configuration levels for CA, MIMO and QAM, which allows it to deliver the highest peak data rates.
| LTE | LTE Advanced | LTE Advanced Pro |
|---|---|---|
| Carrier Aggregation (CA): None | Carrier Aggregation (CA): Five (5) carriers | Carrier Aggregation (CA): 32 carriers |
| Digital Modulation: QPSK, 16 QAM and 64 QAM | Digital Modulation: 256 QAM | Digital Modulation: 256 QAM |
| MIMO: 4 x 4 in downlink (DL) and 2 x 2 in uplink (UL) | MIMO: 8 x 8 in downlink (DL) and 4 x 4 in uplink (UL) | MIMO: 8 x 8 in downlink (DL) and 4 x 4 in uplink (UL) |
However, the challenge is that achieving these data rates requires the devices also to support the same technologies and configurations. For example, if you have an old 4G LTE phone that only supports 4 x 4 MIMO configuration and no carrier aggregation, even if you stand right next to an LTE Advanced Pro cell tower, you will not get the LTE Advanced Pro speeds. This is where the Gigabit Class LTE milestone becomes relevant.
Qualcomm Technologies, in Oct 2016, announced the first Gigabit Class LTE device and network in partnership with a mobile network operator (Telstra), a mobile network vendor (Ericsson) and a device manufacturer (NETGEAR). The role Qualcomm Technologies played was to build an LTE modem (Snapdragon X16) that NETGEAR Mobile Router MR1100 used. This modem could deliver download data rates of up to 1 Gigabit per second or 1 Gbps by taking advantage of the LTE Advanced and LTE Advanced Pro networks. The LTE modem from Qualcomm had specific MIMO, carrier aggregation and QAM modulation configuration requirements to achieve the Gigabit LTE milestone.
What are the requirements for Gigabit LTE?
Gigabit Class LTE or Gigabit LTE requires a carrier aggregation of three carriers, 4 x 4 MIMO in the downlink and 256 QAM digital modulation to deliver peak download data rates of up to 1 Gbps. It utilises the network capabilities that are part of the 4G LTE Advanced and LTE Advanced Pro networks.
The LTE technology was initially introduced in 2009 as per the specifications in 3GPP Release 8. The subsequent 3GPP release, Release 9, added further updates to the LTE technology. However, a significant 4G LTE enhancement was the LTE Advanced technology introduced in 3GPP Release 10. LTE Advanced was followed by LTE Advanced Pro, which further improved LTE technology. While 3GPP documented the LTE technology and enhancements specifications, the term Gigabit LTE was not coined by them. However, based on the sources available to 3GPP in 2017, the requirements for Gigabit LTE on the 3GPP website are as follows:
- Tri-carrier aggregation (3 carriers)
- 256 QAM
- 4×4 MIMO
- Cloud RAN
- Licence Assisted Access technology
The key network capabilities required to deliver Gigabit Class LTE are already available in LTE Advanced and LTE Advanced Pro networks. The primary network-related technology requirements for Gigabit LTE include carrier aggregation of up to 3 carriers, 4 x 4 MIMO (Multiple Input Multiple Output) in the downlink and digital modulation with 256 QAM (Quadrature Amplitude Modulation). LTE Advanced networks (LTE-A) can deliver carrier aggregation of up to five (5) carriers which is already higher than what Gigabit LTE requires. LTE-A can also enable MIMO configuration of 8 x 8 in the downlink, which is higher than the 4 x 4 MIMO required by Gigabit LTE. The 256 QAM modulation in LTE Advanced is the same as what Gigabit LTE needs. The only limitation in LTE Advanced is that it does not support unlicensed frequencies, which is a requirement for Gigabit LTE. However, LTE Advanced Pro addresses this requirement, as shown below.
How is Gigabit LTE different from 5G NR?
Gigabit LTE is a milestone that targets peak download speed of up to 1 Gbps using the fourth-generation (4G) LTE technologies, LTE Advanced and LTE Advanced Pro; 5G is the fifth generation of mobile networks that enables peak download speeds of 10 Gbps to 20 Gbps using the New Radio (NR) technology.
5G mobile networks use a new air interface powered by the New Radio (NR) technology to deliver peak download speeds of 10 Gbps to 20 Gbps. While Gigabit LTE utilises the existing network capabilities of 4G LTE networks, 5G requires new cellular technology, NR, which is superior to LTE.
5G networks also use the OFDM (Orthogonal Frequency Division Multiplexing) transmission scheme, but the maximum carrier bandwidth in 5G NR, with carrier aggregation, is 6400 MHz or 6.4 GHz, which is ten times higher than what 4G can offer. 4G LTE Advanced Pro can achieve a maximum carrier bandwidth of 640 MHz through carrier aggregation (32 carriers) to deliver peak download speeds of up to 3 Gbps.
A mobile phone must support the New Radio (NR) technology to access the 5G network. Therefore, if you have a 4G LTE mobile phone or a mobile broadband router, it will not support the 5G NR technology. However, the backwards compatibility of 5G technology allows any 5G phone or broadband routers to support the 4G LTE technology and enhancements also, including LTE Advanced and LTE Advanced Pro.
5G networks are expected to co-exist with 4G LTE networks for a very long time to deliver a wide range of customer use cases. 5G mobile networks are designed to allow them to utilise the existing 4G LTE infrastructure for initial deployments. The non-standalone deployment model for 5G, NSA, uses the 4G LTE mobile core network, Evolved Packet Core (EPC), to support the early launches of 5G services. It is an option for mobile operators to get a better return on their existing 4G LTE network investments by launching 5G mobile broadband service, Enhanced Mobile Broadband services (eMBB). The other deployment model, standalone 5G or SA, uses a 5G radio network alongside a 5G mobile core network (5G cloud-native 5G core network – 5GCN). Standalone 5G is an end-to-end 5G network that enables futuristic use cases around IoT and other machine type services that require ultra-low latency.
The earlier deployments of 5G are likely to be non-standalone, allowing mobile operators to enter the market early without investing heavily in an end-to-end 5G network. I have written a dedicated post on standalone and non-standalone 5G networks, which dives into the details of these deployment models.
Understanding Carrier Aggregation (CA), MIMO, QAM and LAA
Carrier Aggregation combines multiple carriers into one
Carrier Aggregation (CA) is a technique that allows a mobile network to combine or “aggregate” multiple frequency carriers into one. It enables a mobile network to assign a larger aggregated frequency carrier to an individual user to increase the overall channel bandwidth and associated data rates.
As per the 3GPP release 8 specification, the original LTE networks support flexible bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. Carrier Aggregation was introduced in 3GPP Release 10 as part of the LTE Advanced update. It allows these flexible bandwidths to be combined together to create a big overall channel for a single user. LTE-Advanced allows carrier aggregation of up to five (5) carriers, and LTE Advanced Pro supports carrier aggregation of up to thirty-two (32) carriers. So, for example, a mobile operator can use 5 channels of 20 MHz each to create a total bandwidth of 20MHz X 5 = 100 MHz. I have written a dedicated post on Carrier Aggregation that provides all the necessary details you need to know about.
QAM modulation efficiently uses the bandwidth in LTE
While increased bandwidth is achieved in LTE-Advanced and later versions through carrier aggregation, the available bandwidth efficiency is improved by updating the signal transmission technologies. LTE uses two different multiple-access techniques for its air interface. It employs Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink. The underlying multiplexing technique is Orthogonal Frequency Division Multiplexing (OFDM) which allows multicarrier modulation.
With OFDM, the available carrier bandwidth in LTE, e.g. a 20 MHz channel, is divided into a large number of sub-carriers of 15 kHz bandwidth each. The 15 kHz sub-carriers are digitally modulated individually with the information signal through Quadrature Amplitude Modulation or QAM.
QAM is a highly efficient technique that maximises the number of bits extracted from the available bandwidth through multicarrier modulation. Carrier aggregation increases the available bandwidth by combining multiple carriers, and QAM makes efficient use of the bandwidth to deliver high bit rates. Have a look at my dedicated post on OFDM and OFDMA in LTE networks.
MIMO uses multiple antennas to transmit and receive signals
In addition to carrier aggregation and QAM that collectively increase the carrier size and efficiency, spatial multiplexing ensures that the information signal is sent in a reliable way. The Multiple Input Multiple Output (MIMO) antenna technology in LTE enables spatial multiplexing, diversity and beamforming to increase the signal reliability and data rates.
Spatial multiplexing is one of the key reasons for using MIMO technology in LTE. It is a technique that allows a mobile network to send a large amount of data to a mobile phone in multiple streams, each carrying smaller chunks of data. For this to happen successfully, both the mobile network and the mobile phone must be able to send and receive in this way. This requires technology updates to the base station as well as the mobile phone. Without getting too much into the theory, if you look up ‘Shannon’s capacity theorem’, you will find that the network capacity is a function of bandwidth and the number of antennas. In real life, carrier aggregation (higher bandwidth) and spatial multiplexing (more antennas) directly impact the overall capacity.
The original LTE, 3GPP release 8, adopted a 2 x 2 MIMO configuration, which means two (2) antennas at the transmitter (base station) and two (2) at the receiver (mobile phone). LTE-Advanced, release 10, increased this to 8×8 in downlink and 4×4 in the uplink. LTE-Advanced also introduced new categories of devices; categories 6, 7 and 8, where UE category 8 supports the maximum number of component carriers and 8×8 MIMO.
License Assisted Access for licensed and unlicensed spectrum
License Assisted Access, or LAA for short, allows mobile operators to use their typical licensed frequency spectrum in conjunction with unlicensed frequency bands to boost the achievable data rates for end-users.
LAA is potentially a desirable feature for mobile operators because the frequency spectrum is one of the most precious resources for a mobile operator. In markets like the UK, which have several tier-1 mobile network operators, getting hold of larger portions of the licensed spectrum can be challenging. Unlicensed spectrum can therefore open up new opportunities for mobile operators to beef up their network capacity. This capability was introduced in LTE-Advanced Pro and is also one of the requirements for Gigabit LTE. License Assisted Access is also part of the specifications for 5G New Radio (NR) networks.
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.
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