T-Mobile Launches Voice Over 5G NR using 5G SA Core Network

T-Mobile has deployed commercial Voice over 5G (VoNR, or Voice Over (5G) New Radio) service in limited areas of Portland, Oregon and Salt Lake City, Utah. The Un-carrier plans to expand VoNR to many more areas this year.  Now that Standalone 5G (5G SA) is beginning to carry voice traffic with the launch of VoNR, other real 5G services, such as network slicing and security are likely to be deployed.  T-Mobile customers with Samsung Galaxy S21 5G smartphones  can take advantage of VoNR today in select areas.

“We don’t just have the leading 5G network in the country. T-Mobile is setting the pace for providers around the globe as we push the industry forward – now starting to roll out another critical service over 5G,” said Neville Ray, President of Technology at T-Mobile. “5G is already driving new levels of engagement, transforming how our customers use their smartphones and bringing unprecedented connectivity to areas that desperately need it. And it’s just going to get better thanks to the incredible T-Mobile team and our partners who are tirelessly innovating and advancing the capabilities of 5G every day.”

Standalone 5G removes the need for an underlying 4G LTE network and 4G core, so 5G can reach its true potential. In other words, it’s “pure 5G”, and T-Mobile was the first in the world to deliver it nationwide nearly two years ago.

The addition of VoNR takes T-Mobile’s standalone 5G network to the next level by enabling it to carry voice calls, keeping customers seamlessly connected to 5G. In the near-term, customers connected to VoNR will notice slightly faster call set-up times, meaning less delay between the time they dial a number and when the phone starts ringing. But VoNR is not just about a better calling experience. Most importantly, VoNR brings T-Mobile one step closer to truly unleashing its standalone 5G network because it enables advanced capabilities like network slicing that rely on a continuous connection to a 5G core.

“VoNR represents the next step in the 5G maturity journey-an application that exists and operates in a complete end-to-end 5G environment,” says Jason Leigh, research manager, 5G & Mobility at IDC. “Migrating to VoNR will be a key factor in developing new immersive app experiences that need to tap into the full bandwidth, latency and density benefits offered by a 5G standalone network.”

“The commercial launch of the VoNR service is another important step in T-Mobile’s successful 5G deployment,” said Fredrik Jejdling, Executive Vice President and Head of Business Area Networks at Ericsson. “It demonstrates how we as partners can introduce 5G voice based on the Ericsson solution.”

“We are proud of our partnership with T-Mobile to bring the full capabilities of 5G to customers in the United States,” said Tommi Uitto, President, Nokia Mobile Networks. “Nokia’s radio and core solutions power T-Mobile’s 5G standalone network – and this VoNR deployment is a critical step forward for the new 5G voice ecosystem.”

“At Samsung, we want to give our users the best possible 5G experience on every device – and today’s announcement represents a big step forward,” said Jude Buckley, Executive Vice President, Mobile eXperience at Samsung Electronics America. “By supporting extensive integration and testing, and working alongside an industry leader like T-Mobile, we’re bringing to life all the benefits of 5G technology with the help of our Samsung Galaxy devices.”

VoNR is available for customers in parts of Portland, Ore. and Salt Lake City with the Samsung Galaxy S21 5G and is expected to expand to more areas and more 5G smartphones this year including the Galaxy S22.

T-Mobile is the U.S. leader in 5G with the country’s largest, fastest and most reliable 5G network. The Un-carrier’s Extended Range 5G covers nearly everyone in the country – 315 million people across 1.8 million square miles. 225 million people nationwide are covered with super-fast Ultra Capacity 5G, and T-Mobile expects to cover 260 million in 2022 and 300 million next year.


Voice Over NR Network Architecture:

Voice Over NR network Architecture is consist of 5G RAN, 5G Core and IMS network. A high level architecture is shown below. (Only major network functions are included). This network architecture supports Service based interface using HTPP protocol.


VoNR Key Pointers:

  • VoNR rely upon IP Multimedia Subsystem (IMS) to manage the setup, maintenance and release or voice call connections.
  • UE PDCP should support RTP and RTCP, RoHC compression and MAC layer should support DRX
  • SIP is used for signaling procedures between the UE and IMS.
  • VoNR uses a QoS Flow with 5QI= 5  for SIP signaling messages and QoS Flow with 5QI= 1
    • QoS Flows with 5QI= 5 is non-GBR but should be treated with high priority to ensure that SIP signaling procedures are completed with minimal latency and high reliability.
    •  QoS Flow with 5QI= 1 is GBR. This QoS Flow is used to transfer the speech packets after connection establishment
  • gNB uses RLC-AM mode DRB for SIP signaling and RLC-UM mode for Voice Traffic (RTP) DRBs
  • 3GPP has recommended  ‘Enhanced Voice Services’ (EVS) codecs  for 5G
    • EVS codec supports a range of sampling frequencies to capture a range of audio bandwidths.
    • These sampling frequencies are categorized as Narrowband, Wideband, Super Wideband and Full band.
  • VoNR UE provides capability information during the NAS: Registration procedure with IE ‘ UE’s Usage Setting’ indicates that the higher layers of the UE support the IMS Voice service.
  • The AMF can use the UE Capability Request to get UE’s support for IMS Voice services. gNB can get UE Capability with RRC: UE Capability Enquiry and UE Capability response to the UE.  The UE indicates its support for IMS voice service with following IEs
      • ims-VoiceOverNR-FR1-r15: This field indicates whether the UE supports IMS voice over NR FR1
      • ims-VoiceOverNR-FR2-r15: This field indicates whether the UE supports IMS voice over NR FR2
      • within feature set support IE ims-Parameters: ims-ParametersFRX-Diff voiceOverNR : supported




GSM: VoNR progresses, but requires 5G SA core network

Samsung’s Voice over 5G NR (VoNR) Now Available on M1’s 5G SA Network



2 thoughts on “T-Mobile Launches Voice Over 5G NR using 5G SA Core Network

  1. T-Mobile joins Dish Network in launching VoNR. However, Dish doesn’t operate a 4G network.

    Dish officials said in February that the company has struggled to implement VoNR, partly due to the complexities involved in supporting emergency services like 911.

    However, in a recent conversation with Light Reading, Dish’s Sidd Chenumolu, VP of technology development, said that the company has rolled out VoNR onto its 5G network. Chenumolu explained that the operator views VoNR as another data service running on top of the network. He added that it would be relatively easy for Dish to introduce other voice calling protocols, such as Microsoft Teams, on top of its network, if customers want such services.


  2. T-Mobile spent $304 million in FCC auction 108, and it won 90% of all the licenses sold or 7,156 of the 7,872 total licenses that received winning bids. The auction offered up a total of 8,017 licenses in mostly rural locations around the country, but not all of those licenses received winning bids.

    “With most of the available spectrum in the 2.5GHz band located in rural areas, this auction provides vital spectrum resources to support wireless services in rural communities,” according to the FCC.

    T-Mobile was widely expected to bid heavily in the auction, considering it is the only big wireless network operator that uses the 2.5GHz spectrum band. Moreover, other operators like Verizon, AT&T and Dish Network have spent heavily in other FCC spectrum auctions, leaving them with little financial firepower to chase 2.5GHz spectrum.

    However, the FCC’s 2.5GHz auction generated far less interest among bidders than most analysts had expected. Before the auction started in late July, estimates ranged from $1 billion to $5 billion in total bids. But when the auction ended earlier this week, it generated just $428 million in total bids. Thus, T-Mobile accounted for roughly 71% of all spending in the auction.

    Other big spenders in the auction include PTI Pacifica ($18 million); TeleGuam Holding ($17 million); and Evergy Kansas Central ($13 million).

    T-Mobile will undoubtedly use its auction winnings to expand the rural growth strategy it laid out in recent years.

    This is just the latest batch of spectrum licenses T-Mobile has purchased in recent years for its 5G network. Aside from the vast 2.5GHz holdings it acquired via its $26 billion purchase of Sprint in 2020, T-Mobile also spent around $10 billion in the FCC’s recent C-band auction, $3 billion in the FCC’s 3.45GHz auction earlier this year and $3.5 billion for 600MHz spectrum licenses from Columbia Capital in a deal announced last month.


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