Browse through industry literature or conference proceedings and trade shows, and you’ll be inundated with talk about 5G. On the other hand little is to be found on “4.5G”, or technically speaking, LTE Release 12 and 13 branded as LTE-Advanced Pro [which incidentally I find to be a bad choice of terms that I prefer to use 4.5G even as I don’t like the nomenclature!]. Why is there little to discuss on 4.5 G and much to talk about on 5G? What does this tells us about 4.5G and 5G? And, is there something between the lines that we can read?
A quick review of what 4.5G brings echoes notions of 5G requirements:
- Target 1 Gbps and high-definition CD-quality voice and video.
- Allow operators deploy services faster and cheaper through virtualization.
- Greater carrier aggregation capabilities – 4 or more with capability up to 32 carriers and total aggregated bandwidth of 60 GHz at minimum.
- Aggregation of unlicensed band carriers with primary licensed band spectrum to opportunistically boost data rate (License-Assisted Access – LAA).
- High-order MIMO with 4 antennas in FDD (4T4R) and 8 antennas in TDD (8T8R), or more.
- 256QAM DL / 64 QAM UL modulation.
- EVS codec.
- Indoor positioning enhancements.
- Antenna systems enhancements such as elevation beamforming.
- Superposition coding for enhancement for downlink multiuser transmission.
- Enhancements for device communication including new low complexity devices based on NB-IoT or LTE Cat-m1.
- Mission-critical push-to-talk.
- Multi-connectivity user devices to that replace today’s multi-mode devices which are active on one mode at a time.
So what is the difference between 4.5G and 5G?
Fundamentally, 5G targets achieving higher scalability – for example combining milli-meter wave spectrum to ultimately achieve 10 Gbps throughput. In other words, 4.5G will look like 5G expect for the ‘scalability’ factor: 4.5G is based on the LTE architecture and inherits all of its disadvantages which results in lower scalability that a 5G network designed from the start to scale.
4.5G is a natural evolution of 4G networks that does not demand as big an investment as a brand-new technology as 5G promises to be (a new physical layer requires equipment rip-and-replace). Operators will deploy 4.5G as some have announced. The roadmap is clear as is the investment. The benefits are quantifiable. The same vendors will provide the upgrade to their deployed equipment – i.e. the market is already locked from outside entrants. The same cannot be said about 5G where the dice rolls again and everybody gets to play again. In short, 4.5G is ‘boring’ and 5G is ‘sexy’. For this reason 4.5G gets little attention. But it is also for this reason that 4.5G is a sure bet whereas 5G is risky.
This begs another question: if 4.5G and 5G look alike with the difference being in scalability, should carriers rush to deploy it?!