What is LTE-Advanced Pro?

LTE Advanced Pro

LTE-Advanced Pro is the new official ‘marker’ approved by the 3GPP in October 2015 to denote the next stage in development towards 5G, following LTE-Advanced (LTE-A) and LTE before it.

LTE-Advanced Pro (LTE-A Pro) will be used for specifications defined under 3GPP’s Release 13 (R13) and Release 14 (R14). LTE-A Pro will build on previous iterations to further improve the LTE platform as well as address new use cases. Release 15 (R15), work on which was outlined in detail in June 2016 and is set to be completed in June 2018, will be the first 3GPP release to include specifications for 5G technology

 

What is LTE?

Before we consider LTE-A Pro, let’s take a step back to understand LTE and LTE-A. Specifications for the Long Term Evolution (LTE) access network were agreed in late 2008. In legacy 3G networks, the radio network controller (RNC) controlled the NodeB 3G base stations. In an LTE network, a series of evolved NodeB (eNB) base stations have control functionality embedded, so there is no need for a RNC. This flatter, simpler network architecture allows quicker response times.

Just like LTE sought to provide higher mobile data transfer rates than legacy 3G, LTE-A aimed to improve on LTE, as well as to fulfil the requirement set by the ITU for 4G. LTE-A Pro will do the same and prepare for 5G.

Essentially, we can think of LTE as 3.5G or pre-4G, LTE-A as 4G, and LTE-A Pro as 4.5G or pre-5G.

 

What are R13 and R14?

3GPP (3rd Generation Partnership Project) is the global organisation that consolidates and defines specifications for mobile technology standards, and has become the focal point for mobile networks beyond 3G. Its progress in revising specifications is measured in ‘Releases’, and new features are ‘frozen’ and ready for implementation when a Release is completed. 3GPP works on a number of Releases in tandem and aims to make all systems both backwards and forwards compatible.

R13 and R14 add to the LTE-A technology path. R13 was begun in September 2012 and was frozen (completed) in March 2016 with some 170 high level features and studies. Standardisation of NB-IOT, the new narrowband radio technology developed for the IoT, was completed in June 2016 and concluded a major effort in R13 to address the IoT market. R14, building on many of the projects and features of R13, began in September 2014 and the work is slated for completion by June 2017. By the end of 2015 more than 50 projects had been defined for R14.

 

What will LTE-A Pro do?

LTE Advanced

LTE-A Pro aims to significantly increase the data speeds and bandwidth available for mobile communications. It will also bring a much wider range of connected devices and platforms under a single standard.

LTE-A Pro seeks to improve and optimise the capacity, performance, functionality and efficiency of LTE-A, as well as to further reduce latency, to provide a better user experience. It will also enhance the LTE platform for the delivery of new services to new markets as we move towards IoT with 5G.

The key attributes that will define LTE-Advanced Pro are:

  • Data speeds in excess of 3Gbps (LTE-A: 1Gbps)
  • 640MHz of carrier bandwidth (LTE-A: 100MHz)
  • Latency: 2ms (LTE-A: 10ms)

 

How will it do it?

LTE-A Pro will incorporate a number of different technologies, many of which will be more advanced forms of features already present in LTE-A and even LTE.

Carrier Aggregation enables faster data speeds by increasing the bandwidth available to devices by using more than one carrier (channel). It was a key feature of LTE-A specifications, supporting aggregation across FDD and TDD (frequency division duplex and time division duplex) spectrum types. Advanced carrier aggregation in LTE-A Pro will increase the number of different carriers that can be simultaneously supported from five (under LTE-A) to 32.

This will be achieved through Licensed Assisted Access (LAA), which was introduced by the 3GPP in 2015; the first over-the-air trial was conducted by Qualcomm in Germany in November 2015. Spectrum availability is an issue with LTE but there is significant unlicensed 5GHz frequency available that is currently used by WiFi networks. LAA allows the simultaneous use of licensed and unlicensed spectrum bands to make the most efficient use of all available spectrum, while LTE WiFi (Link) Aggregation (LWA) enables aggregation between LTE and WiFi.

Enhanced LAA (eLAA) is a project within R14 that will allow licensed and unlicensed spectrum aggregation in the uplink, in addition to the downlink streams supported by LAA.

Small cells are ideal for use in unlicensed spectrum and are typically deployed as hotspots within macro cell coverage. They are increasingly being used to meet growing data transfer demands. Aggregation between small and macro cells through dual connectivity will significantly improve per-user throughput and mobility robustness, and LTE-A Pro will continue work already begun in this area.

New for LTE-A Pro, dynamic uplink and downlink aggregation will allow operators to dynamically adjust to varying traffic needs by (a) changing the uplink/downlink configuration based on traffic and (b) enabling downlink traffic offloading. The new FDD/TDD design will reduce latency more than tenfold.

Beamforming and MIMO (multiple-input multiple-output) have been identified as key technologies to address future capacity demand. Prior to LTE-A, beamforming focused on the azimuth dimension, essentially at ground level. LTE-A began investigations into elevation beamforming, where antenna arrays target taller buildings. LTE-A Pro will exploit full dimension MIMO (FD-MIMO), which simultaneously supports both elevation and azimuth beamforming to significantly boost capacity and coverage.

At the same time, the use of many more antennas will evolve towards Massive MIMO, a key enabler for 5G. R13 saw support for eight, 12 and 16-antenna elements; R14 will go beyond with up to 64 antenna ports at the eNB.

 

What will it enable?

LTE-A Pro will pave the way for IoT by introducing new devices and new services to serve new industries than is possible in current 4G networks.

Work on new devices is focused on increasing the battery life, reducing the cost of the device and its deployment, and extending coverage.

A new category of low cost and low throughput devices is needed for many IoT applications. LTE-A Pro encompasses NB-IOT and LTE-M technologies that will provide lower speed narrowband access for low power devices. LTE-M is a variant of LTE that has been developed for machine-to-machine (M2M) communications. High bandwidth networking will be reserved for more powerful devices needing high throughput and low latency.

The LTE Direct protocol was borne out of work done by Qualcomm. The device-to-device (D2D) technology enables the discovery of thousands of devices within a proximity of around 500m to facilitate proximity services. Work on proximity services focused on public safety applications began in LTE-A projects, and continues into R13. Future work will also look at social applications.

R13 further aimed to allow operators to multiplex reduced bandwidth machine-type communications (MTC) devices and regular devices in existing LTE networks.

A specific area of focus in R14 will be D2D and device-to-network relays for IoT and wearables, considering how remote MTC devices like wearables connect to other devices, which in turn connect to the access network. Specifically, R14 aims to define a generic device-to-network relay architecture.

The use of LTE for emergency services and public safety was an important aspect of R13, culminating in the first set of specifications covering mission-critical services, notably the mission-critical Push-To-Talk (MC-PTT) protocol. This work will continue into R14 with mission-critical video and data services.

A key project within R14 is vehicle-to-anything (V2X) communications, which will ultimately support vehicles connected with infrastructure, people and networks to enable autonomous (self-driving) cars.

 

Who’s Doing it?

According to the Global mobile Suppliers Association (GSA), as of June 2016 47 operators globally had trialled, deployed or commercially launched LTE-A Pro technologies. At that time commercial services were available in Australia (Telstra), South Korea (SK Telecom), Thailand (AIS, True) and Turkey (Turkcell, Turk Telecom, Vodafone).

All the main equipment manufacturers are working on LTE-A Pro.

 

When will it be available?

Despite the progress made in 4.5G specifications, none of the commercial operations have yet achieved (or come close to achieving) the 3Gbps data speeds that have been defined for LTE-A Pro. GSA data shows that Telstra and Turk Telecom both offer services at 600Mbps, and the latter has demonstrated speeds up to 1.2Gbps, but that’s still only just ahead of LTE-A capability.

And there are as yet no 3Gbps phones on the market. LG, Samsung and Sony all have 600Mbps capable phones, but the next to come to market will only support 1Gbps. In February 2016 Qualcomm announced what it claims was the first Category 16 LTE modem chipset. The Snapdragon X16 supports download speeds of up to 1Gbps and LAA, again significantly off what is needed for LTE-A Pro.

Clearly, full commercial LTE-A Pro services are still some time off.

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