By James Kimery, Director, Marketing, RF Research/SDR, NI
The evolution of the wireless space has been an important factor in the consequent disruption of a majority of industry sectors. 2019 is all set to see 5G technology become an essential catalyst for growth, with service operators around the world having already begun the deployment of 5G services. While the early 5G sub 6 GHz rollouts are a milestone, it is mmWave deployment that truly represents the pathway to the transformational impact needed for the 5G ecosystem.
Wireless researchers and 5G ecosystem suppliers have long expressed consistent interest in the mmWave spectrum due to its availability for mobile access in both the licensed and unlicensed bands. In fact, the mmWave spectrum for 5G dwarfs the spectrum available for prior generation cellular, WiFI and Bluetooth combined. With larger spectrum availability comes higher data rates and the ability to accommodate more users assuming similar spectral efficiencies. Currently, mmWave deployments have been targeted to fixed wireless access, or in other words fiber to the home (FTTP) replacements.
Most 5G deployments today target sub 6 GHz spectrum and the Non-StandAlone (NSA) architecture which uses LTE as the anchor for the control plane, with the user plane flowing directly to the EPC (4G) or NGC (5G) depending on the specific NSA architecture. While 5G mmWave will likely follow the same route, the necessary increase in bandwidth may not be as forthcoming as in the case of Sub 6 GHz 5G. With 5G mmWave deployments relying heavily on NSA architecture, the question arises, “Does 5G standalone (SA) make sense?”
Despite the earmarking of large portions of the spectrum for 5G mobile access in the mmWave bands, the propagation of waveforms at these frequencies is much shorter than the sub 6 GHz implementations. In addition, the directional nature of mmWave waveforms must also be contended with, along with their propensity to be blocked, causing disruptions to the link. While the 3GPP has devoted a good portion of the specification to the concepts of beam management and beam recovery to address these scenarios, they remain merely theoretical in nature, with little guarantee of practical applicability at optimal efficiency.
It is necessary now to consider the NSA or SA for 5G mmWave. SA is advantageous for all 5G deployment as it reduces latency and lowers cost due as it does not rely on 4G/LTE for the control information. However, NSA also has a case for 5G mmWave as LTE deployments are available and are robust. In the SA 5G mmWave scenario, the control channels utilize the same 5G mmWave spectrum as the data. For NSA 5G mmWave, LTE provides the anchor and the control information is transmitted over that link.
For example, when a 5G mmWave UE is connected to a gNodeB where both the control and user planes utilize a mmWave band, the control information is subjected to the same interference and blocking challenges as the data plane and thus the beam management and recovery will be engaged to maintain the link but these procedures take time and the likelihood of link disruption is quite high. NSA provides a more stable link for the control plane and may prove critical in terms of gNodeB handoff and cell selection for the mobility case. Handoff is very important because the rate of handover will be much higher in a mmWave network due to the greater density of base station deployments.
As the industry moves toward closer to a 5G reality, mmWave continues to be an important technology for mobile access to realize the goals and objectives of 5G. Architectural choices such as the tradeoffs between NSA and SA become more poignant and perhaps difficult. Service providers today are in the process of evaluating the feasibility of deploying 5G SA mmWave technologies, however mmWave deployments will remain dominated by NSA for the short-term.
5G NR for wireless communications, with new bands, wider bandwidth, and new beamforming technology, presents significant design and test challenges that require powerful tools to accelerate innovation. The focus for industry players, thus, must be to provide these tools in an effective manner so as to ensure the continued progress of the ecosystem.
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