AT&T looks to accelerate 5G testing

Monday 13 March 2017 | 13:12 CET | Background

AT&T wants to move quickly with 5G. The American giant is one of the companies already testing pre-commercial applications for 5G, in an effort to avoid any slowdown in development. Telecompaper talked at Mobile World Congress with Gordon Mansfield, AT&T's Vice President RAN & Device Design, on the company's work. 


AT&T started already in 2016 testing with Nokia equipment for the 28 GHz and 39 GHz bands. The aim is to offer households and businesses an alternative to fixed connections for fast broadband. 

On 01 March Mansfield signed on behalf of AT&T the 5G Test Statement. This brings together a number of industry players that have agreed to work together on testing and closely follow the standardisation process in order to come to an intermediary 5G standard. 

Besides AT&T, other signatories are China Mobile, NTT Docomo, Vodafone, Ericsson, Huawei, Intel, Keysight, MediaTek, Nokia, Qualcomm, Rohde & Schwarz, Datang and ZTE. The industry has decided to run the phases of standardisation, testing and production readiness in parallel, in order to accelerate the launch of 5G.

The testing should lead to definite standards sooner. On 9 March, the standardisation forum 3GPP approved the plans for an intermediary standard for 5G, which will support fixed-mobile wireless applications.

Fast broadband and fixed-mobile services

AT&T as well as its competitor Verizon want to use wireless for the fixed broadband market. Both still have DSL networks, which are being surpassed by cable, Google Fiber and other local fibre projects. While both of the major operators are rolling out fibre and upgrading their networks in selected areas, this is costly and slow. Fibre is also not an option for less densely populated areas. 

A great deal of capacity is available using mmWave spectrum. AT&T has developed the AirGig technology to transport signals along above-grond telecom lines. AT&T wants to place low-cost antennas that send the signal along (and not over) the lines. This allows it to use existing infrastructure and limit investment costs. 

Verizon has developed its own pre-commercial specification for 5G with partners in the Verizon 5G Test Forum (5GTF) and is working with companies such as Cisco and Nokia to develop compatible equipment. This is also aimed at delivering faster broadband over 5G, known as eMBB (enhanced Mobile broadband).

Tight shedule

AT&T wants to make an active contribution to developing and testing the radio equipment needed for 5G, in order to roll out quickly in the US. The timing is tight, Mansfield stressed. 

3GPP Release 15 – the first for 5G – is expected to be ready in mid-2018. It takes another three months before all the technical specifications are published. Only then can companies start work. Even if much is known in advance, as 3GPP works from data approved by its members, surprises cannot be ruled out entirely.

5G requires radio equipment, chipsets, a new radio (NR) air interface and the necessary software. All of this needs to be developed and tested for interoperability and stability. After the standardisation and testing, the equipment needs to be prepared for mass production. The whole process faces many tight deadlines which risk being missed.

A number of upcoming sporting events in Korea and Japan (Olympics) as well as Europe (footbal) have been adopted by industry as deadlines for launching 5G networks. Japanese broadcasters are already planning to cover many Olympic events in Tokyo in 8K video, after testing the technology at the London games. The US market does not have the same milestone dates, but is developing continuously in the face of tough competition in the broadband market, Mansfield said.

Parallel developments

The process has progressed to the point where the hardware ('boxes') can be developed at the same time as the software. Both in the development and the test phases swappable hardware is used on which the latest software releases are loaded as soon as they are ready. 

Any delay in the hardware is seen as a major setback in the industry. The sector wants to start locking down the lowest layers by December 2017, according to Mansfield. At that point the chipset makers can start producing pre-commercial and commercial equipment. Once the latest versions are tested and stable enough, operators can start the pre-commercial phase with customers.

At the higher layers, changes can still be expected. However, these are largely software adjustments. This is to be expected, as the highest network levels must be flexible enough to last the next 40 years of continuous development. 

There are risks to running development and production in parallel, as seen in other high-tech industries like aviation. Changes in the design can mean all the devices already produced must be adapted. However, the risks are less serious in the telecom sector, as adjustments are increasingly software based. End-users are also used to changing equipment regularly, especially in the first iterations of a new generation of network technology. 

AT&T: continuous evolution

AT&T has seen significant growth in its data traffic, and over half is already video. "We constantly have to find places to put that traffic," Mansfield said. 

While the operator is following the evolution of 4G, it's already busy developing 5G. The fastest way to start is the so-called 'Non-Standalone' (NSA) version of 5G. Developed to accelerate the start of 5G, NSA uses the 5G NR (New Radio) in new spectrum while signal traffic is still handled over the LTE network. 

Where to find the NR spectrum is still the subject of international debate. There are several major telecom regions around the world with different designations for spectrum bands. Some have common uses, such as 28 GHz, 37 GHz and 39 GHz. The 57-64 GHz and 64-71 GHz ranges offer licence-free blocks of spectrum, at least in the US, AT&T expects. Under 6 GHz, the 3.4-3.8 GHz range is seen as the most promising. 

Testing contributions

AT&T Labs is testing with multiple vendors at its 5G Technology Testbed, using both mmWave (over 30 GHZ) and sub-6 GHz frequencies. De tests are underway in Middletown, New Jersey and at two sites in Austin, Texas.

AT&T announced it's focusing on channel sounding and measurement, which analyses how a signal passes through the air. This is an important issue for complex antenna systems, such as massive MIMO.

The operator is also conducting friendly user tests in the 28 GHz band with Ericsson and Intel. The low-hanging fruit is seen as fixed-mobile broadband services for consumers and small businesses over a 28 GHz network. This is in line with Verizon's plans.

While AT&T and Verizon have similar plans for 5G, there is no direct cooperation between the two, Mansfield underlined. They are both active in international forums and provide input based on the demands of the American market. Direct coordination though is not possible due to competition rules. 


In addition to the eMMB already in development at AT&T and Verizon, 5G's other main elements are low latency and support for machine-type communication (MTC). Since 3GPP Release 13, a number of new opportunities for M2M or IoT services have been developed, but the most interesting applications depend on very low latency and high reliability - something that will only come with Release 15. The full development of New Radio will be seen in Release 16, or '5G+'. 

The core network and cloud services are evolving in pace with the rapid advances in the radio network, Mansfield said. AT&T has already been working on virtualisation for several years. Around 30-40 percent of its network functions are virtualised, and this will grow to 45 percent by the end of this year and 70 percent by 2020. Investments in the core network are focused on the transition from 4G to 5G. Following breakthroughs in virtualisation, "we spin up functions as we go along", Mansfield said.

The priority is supporting expected high-growth applications. At a certain point, legacy systems will be abandoned, although in a gradual process, Mansfield said. He said AT&T is ahead of other players in the US on this, as well as operators in the rest of the world.

5G chipsets

Qualcomm has developed the X50 modem to integrate in 5G smartphones, with support for 2G-3G-4G-5G all on one chip. The company said at MWC that it will support all the 5G bands, both sub-6 GHZ and mmWave. Qualcomm also supports the NSA (Non-Stand Alone) version of 5G NR, which uses LTE for signalling traffic.   

Mansfield said advances in LTE services can also be expected this year, thanks to Qualcomm's Snapdragon 855 chipset and X16 modem. High-end smartphones in the pipeline will support four-carrier aggregation, 256QAM, 4x4 MIMO and LAA (License Assisted Access, which uses licence-free spectrum for LTE). The chipsets are ready, and the smartphones will follow later this year. At the point, many of the pieces will start falling into place, Mansfield said. 

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