How is 5G different from 4G?

The simple answer to this question is that 5G enables new services (requiring significantly higher speeds and much lower latency) compared to those possible over 4G. But how, and why 4G isn't capable of driving such features? The purpose of this note is to explain the reasons. In the process, we will also discuss how operators can leverage such capabilities for generating new revenue streams - a must under the current dynamics, where voice and data has already been commoditized.

Multiple Beams

The 5G system is capable of driving the radio signals into narrow beams, each serving an individual customer. This is quite unlike the conventional system, where a single radio beam is designed to serve all the customers located in the sector of the base station. But why it is so important to break the radio signals into narrow beams? As doing so significantly enhances the capacity of the overall system compared to those running on single beams. This is due to the theoretical data carrying limit of the radio channel defined by the Shannon-Hartley equation as explained below.

C = B x Log(1+S/N), where C is channel capacity, B is bandwidth of the channel, and S/N is the signal to noise ratio of radio wave.

In simple language, the maximum rate at which we can transmit information in a radio channel without any error, is limited by the bandwidth, the signal level, and the noise level. Therefore, the capacity a radio channel cannot be raised indefinitely, as the above parameters are constrained by physical limitation of every system. But 5G has been able to overcome this barrier by driving multiple RF narrow beams within the same block of spectrum. Though each of these beams are limited by the "Shannon Limit", but since there are multiple of these, the capacity of the overall system is raised significantly compared to those running on a single beam. Therefore, average throughput (visible to the customer) in a 5G system is not limited by the peak speed and the number of users using the system simultaneously - typically the case in systems running on 4G.

But what is preventing 4G to leverage similar capability?

Frequency Bands

All 4G systems are deployed in the lower frequency bands. Though doing so has its advantages, as it reduces the number of sites (the radio waves riding in the lower spectrum bands travel much further). But there are some challenges too. It is difficult to implement MIMO (Multiple Input and Multiple Output) in the lower spectrum bands which is needed to enable these narrow beams. But why? This is due to the fact that size of the antenna of the MIMO system has to proportional to the wavelength of the radio wave. Why is this an issue? This is because the frequency and wavelength of the radio wave is linked by the following equation.

Velocity of the Radio Wave (Speed of Light) = Frequency x Wavelength

Since the left hand side of this equation is constant, therefore if the frequency of the radio wave is reduced, the wavelength increases proportionately, which in turn makes the MIMO antenna system quite bulky, thereby making it difficult for it to be managed and maintained. This is the reason why 4G system hasn't been able to unlock multiple narrow beams which a 5G system (running on very high frequencies) easily can - making the 5G system capable of packing a large number of antennas in a very small form factor (size of a WiFi router). But how does a 5G system deal with the poor propagation characteristics at these higher frequencies? Will it not significantly increase the number of sites required compared to a 4G system?

Pico & Femto Sites

A 5G system using very high frequencies (26, 28 GHz) does not use macro cell sites as the conventional systems running at lower frequencies do. These cells sites are much easier to deploy, maintain and also consumes less power (compared to marco). However, traffic aggregated at these sites needs to be back hauled using high capacity links (OFC, V, E bands). Hence, a 5G network will look quite different from a conventional network using lower spectrum bands. But how can we use 5G system for driving new revenue streams?

Stable Average Speeds

As explained above, the capacity of a 5G system is significantly higher, as it used multiple beams and large quantum of spectrum (20 to 80 times higher than 4G). Also, due to multiple narrow beams (specific to a user), its average throughput is not only held high but also is stable, and does not fall even with the increased user density within the sector - quite unlike the case what happens in a 4G system. This enables a wire line kind of experience (with similar uplink and downlink speeds) in a 5G wireless system which is unheard of till date. Therefore a 5G system can be effectively used to drive wireline capabilities at home where laying of OFC is a challenge. For India (with low OFC penetration) this is a great opportunity. This will enable the operators to cost-effectively drive DTH like content to homes and corporation, thereby enhancing their revenue streams. And with time opportunities for other services will open up as well.

Lower Latency

5G system enables much lower latency compared to a 4G system. But how? This due to the fact that the 5G system enables a flexibility to the user to read and aggregate signals at the symbol level, quite unlike the 4G system where the aggregation is possible only at the frame level. This means that in a 4G system the application has to wait for the whole frame to be received before it can respond back. However, in a 5G system the response is almost instantaneous - opening the possibility of new class of services which are impossible to be delivered via 4G.

Conclusion

It is clear that 5G system unlocks capabilities which are not possible in a 4G system. This open up opportunities for driving new applications and generating new revenue streams, thereby creating a win-win for all - customers, operators, and ecosystem players. In order to for the 5G system to leverage the capability (mentioned above) the millimeter band (26 & 28 GHz band) needs to be opened up and assigned quickly, as the current 3.5 GHz band recommended by TRAI will have all the constrains mentioned above (bigger antenna sizes etc), which the 4G system are currently facing in the lower spectrum bands.

(Views expressed are of my own and do not reflect that of my employer)

PS: Find the list of other relevant articles in the embedded link.