Aug 19, 2019
Qualcomm products mentioned within this post are offered by Qualcomm Technologies, Inc. and/or its subsidiaries.
5G is not only poised to be the fastest cellular transition ever but also the smoothest, thanks to innovations in the 5G standard that enable a phased evolution and tight interoperability with current 4G networks. Key 5G features that facilitate the transition from non-standalone (NSA) mode of operation include 4G/5G dual connectivity and Dynamic Spectrum Sharing (DSS). Let me explain how these features will work together to accelerate the transition to 5G standalone.
Phase 1: NSA mode and 4G/5G dual connectivity for early access to 5G enhanced capacity and speeds
The NSA mode of operation introduced in 3GPP Release 15 allows 5G deployments to utilize LTE core networks and base stations, while adding new 5G base stations. NSA allows mobile operators to introduce 5G and increase overall network capacity – thanks to the wider bandwidths in new bands in which 5G will be deployed, along with all the advanced radio techniques built into 5G – while relying on an anchor in the 4G radio access and core network.
All commercial 5G network rollouts this year are expected to use NSA mode with 5G New Radio (NR) deployed on either millimeter wave (mmWave) high bands or sub-6 GHz bands (2.5/2.6 GHz, 3.5/4.5 GHz or 600 MHz), while utilizing lower bands for the LTE anchor (<2.7 GHz). Instead of having to wait to launch 5G while an anchor 5G network is built, NSA allows 5G to be launched much sooner on top of a 4G anchor.
5G NSA mode utilizes dual connectivity with 4G and 5G radios, which allows devices to send and receive data using 4G and 5G simultaneously to independent sites as needed. In this scenario, the network is not just using a 4G anchor. It's carrying traffic over both 4G and 5G, each in its own spectrum, aggregating the content in the device. By using both 4G and 5G at once to carry data, users get much faster connectivity than if they were using only one or the other. In fact, results from real world deployments show that users are getting multi-gigabit speeds where this dual connectivity technique is deployed.
5G NSA with 4G/5G dual connectivity is supported in the Qualcomm Snapdragon 855 Mobile Platform, with the Snapdragon X50 5G modem and Qualcomm RF Front-End solutions, the platform of choice for virtually all the first wave of 5G smartphones and devices launching in 2019.
Phase 2: DSS and standalone mode for extensive 5G coverage and advanced services
A related issue in easing the transition to 5G is how to deploy 5G in spectrum currently used for 4G. In prior transitions from one G to another, this was done via “refarming.” If a spectrum band was used for 3G, before 4G could be deployed, the band had to be emptied of 3G users; it had to be refarmed. That process could take years, sometimes a decade or more — a very lengthy transition.
In 3GPP Release 15, a feature called 5G DSS, or Dynamic Spectrum Sharing, obviates the need for refarming, thereby greatly accelerating the 5G transition. DSS exploits the fact that both 4G LTE and 5G NR are based on OFDM technology and introduces techniques for the waveforms to operate together in a seamless manner using the same spectrum. In other words, DSS allows for the coexistence of both 4G LTE and 5G NR users in the same frequency band/channel at the same time, and lets an operators’s base stations and network divide the channel resources dynamically between 4G and 5G users at each cell site.
In effect, 5G DSS turns virtually any band used with 4G LTE today into a band in which 5G can also be deployed immediately. This feature will typically be deployed in low sub-6 GHz frequencies, providing much better 5G coverage — greater than can be achieved from higher new 5G bands. It also provides additional capacity for 5G, without the extensive delays, which would result from a much lengthier refarming process. While DSS adds additional overhead to support operation of 4G and 5G in the same band, the benefits of using DSS for a gradual spectrum transition largely outweigh the effect in capacity.
The coverage benefits of DSS are a stepping stone to the introduction of 5G standalone (SA) mode of operation, which implements 5G end-to-end from core network to radio access, without the usage of an anchor 4G network.
Extensive coverage for 5G SA mode, enabled by DSS, allows mobility and continuity for new services using unique 5G capabilities such as guaranteed quality of service and network slicing. These network capabilities are essential to support emerging new business models in areas such as Industrial IoT (IIoT) and enterprise-grade cloud services.
The bottom line is that 5G DSS helps provide broad coverage and enables SA mode to work well, allowing operators to deliver new 5G services to many consumers in a timely manner – without having to rely only on new spectrum bands or a time-consuming refarming process.
An important aspect of this phased approach to 5G deployment — NSA mode, dual connectivity, DSS, and ultimately SA mode – is support for legacy devices in the field. With DSS, mobile operators can architect their networks to simultaneously supports 4G LTE, 5G NSA, and 5G SA devices with broad coverage. This approach is also valuable for providing quality voice services using today’s highly-optimized voice-over-LTE techniques, while 5G NR voice specifications and technologies mature over time.
Support for DSS and SA mode is included in Qualcomm Technologies’ second-generation 5G solutions, including the Snapdragon X55 5G modem and 5G RF Front End, which are poised to power a second wave of 5G devices beginning in late 2019.
In summary, the following phased approach allows for a smooth 5G rollout:
- 1. Legacy 4G LTE network operating in existing low and mid bands.
- 2. 5G NSA is overlaid using mid band (e.g., 3.5 GHz) or high band (e.g., mmWave) with dual connectivity. The utilization of a 4G core network and radio control in 5G NSA facilitates rapid deployment, while Dual Connectivity aggregates 4G and 5G to support faster and consistent connectivity.
- 3. Dynamic Spectrum Sharing is deployed in existing low and mid 4G bands, enabling simultaneous operation of 5G and 4G in these bands as well as the introduction of 5G SA, along with related services (5G QoS, 5G security, slicing). Carrier aggregation can also help by enabling even faster data speeds and expanding high/mid band 5G coverage by moving all uplink to low band; 4G and 5G NSA devices using dual connectivity continue to be supported.