If telco executives get their way, 6G will be a software upgrade that does not require replacement of 5G network elements such as radios. In some ways, that will be challenging.
"We believe that a software-only upgrade to 6G is the best way to meet the increasing demands of mobile users and businesses,” said Niklas Heuveldop, Vodafone CTO.
"A software-only upgrade to 6G is essential for us,” said Hannes Ametsreiter, Deutsche Telekom CTO.
Perhaps surprisingly, even Rajeev Suri, Nokia CEO, has said "a software-only upgrade to 6G is the only way to meet the ambitious goals of the 6G roadmap.” It will be challenging.
It is not clear whether the in-place radios are frequency-agile enough to handle huge new blocks of millimeter wave or teraHertz frequencies. So it is not clear whether virtualized or software-defined radios can be used with the existing 5G infrastructure to allow the 6G upgrades without major upgrades or replacement of existing radio infrastructure.
Then there is the issue of whether the existing 5G network radio sites are compatible with the signal propagation characteristics of new millimeter or teraHertz spectrum that might be added, or how much new radios or new small cell sites will be required.
Easier to implement are new modulation techniques, for which there are a number of possible alternatives to the 5G orthogonal frequency-division multiplexing standard.
What might make adaptive modulation possible--the ability to use different modulation methods depending on local conditions, is the 5G ability to support 5G networks can also use adaptive modulation, which allows the modulation scheme to be changed dynamically, depending on the channel conditions.
That feature should support dynamic modulation that is more robust in areas where signal propagation is more challenging (though supporting less bandwidth); but supporting maximum throughput in other areas with favorable signal propagation characteristics.
6G is expected to use higher-order modulation schemes than 5G, such as 256QAM and 1024QAM. This will allow for more bits to be transmitted per symbol, increasing the spectral efficiency of the network.
But there also are a number of potential modulation approaches.
Index modulation: Index modulation is a technique that uses the indices of active transmit antennas, subcarriers, or time slots to transmit additional information. This can be used to further increase the spectral efficiency of the network.
Non-orthogonal multiple access (NOMA): NOMA is a technique that allows multiple users to share the same spectrum resources at the same time, without causing interference. This can be used to improve the network capacity and support more connected devices.
Machine learning (ML)-based modulation: ML can be used to develop new modulation schemes that are more efficient and robust to interference.
Hybrid modulation schemes: Hybrid modulation schemes combine elements of different modulation schemes to achieve the best possible performance in different operating conditions.
Polar modulation: Polar modulation is a new type of modulation that is more efficient and robust than conventional modulation schemes. Polar modulation is expected to be used in 6G to achieve higher data rates and improve reliability.
MIMO modulation: MIMO modulation uses multiple antennas to transmit and receive data simultaneously. This can significantly increase data rates and improve reliability. 6G is expected to use MIMO modulation with a larger number of antennas than previous generations of cellular technology.
MIMO-OFDM: MIMO-OFDM is a multiplexing technique that uses multiple antennas at the transmitter and receiver to transmit and receive multiple data streams simultaneously. MIMO-OFDM is already used in 5G networks.
In addition to OFDM, 5G networks can also use other modulation techniques, such as filter bank multicarrier (FBMC) and universal filtered multicarrier (UFMC). However, OFDM is the most widely used modulation technique in 5G networks today.
It is the existing 5G network’s ability to use adaptive modulation, supporting modulation schemes that can be changed dynamically depending on the channel conditions, which will support 6G.
It remains to be seen how much such approaches can support a software-only upgrade of 5G to support 6G. Many will guess that hardware upgrades will still be necessary, though on a perhaps-reduced level compared to earlier mobile network upgrades.
That there is growing buyer resistance to the traditional hardware-based platform updates is obvious. Just as obviously, there are possible new opportunities for non-traditional suppliers, such as the hyperscale cloud computing providers.
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