4G v 4G+

4G v 4G+ : The concept of carrier aggregation

All of us or at least most of us are using 4G mobile phones or say phones with 4G network connection (BSNL is still on 3G). Thanks to Jio, the internet prices dropped and the internet usage increased in India. Plus, more people got access to 4G network; again thanks to Jio for providing call and data services for absolutely free in its initial days. 4G connection is shown as '4G' on all the phones' top right corner which you all might have seen. Some people may also have seen small + after 4G(4G+). What is that? Before going into 4G+ or carrier aggregation, let us understand what is this 4G?

    The G in 4G stands for generation. The generation here means the same way that we use in our house hold ('Generation gap'). Yes, the generation refers to the different periods which saw the introduction of different technologies, advancements from time to time. As written in the previous article, the introduction of wireless communication revolutionized the whole communication sector. It introduced the mobility over the fixed place landline phones. Any new invention or discovery will be initially primitive and continues to grow. The gist of wireless communication was transferring over electromagnetic waves like Radio waves, microwaves etc. It is not simple at all. It involves various steps. One may have heard of modulation, sampling and other terms. These are all involved in the communication both wired and wireless. Let us take modulation technique for example. In syllabus, we start from analog modulation schemes like AM, FM etc to digital modulation schemes like PSK, ASK , BPSK, QAM and many more. This shows the development that happened just in terms of modulation. The wireless communication has also developed on the same lines. The developments however is not only restricted to modulation schemes but also has happened at different stages of wireless communication. These developments are grouped together in a time frame and collectively called as a Generation. 

    It started with 1G which used AM (Amplitude modulation) and supporting only calls. Then the evolution of technology saw the arrival of 2G, 2.5G, 3G, 3.5G and now widely used 4G and the latest 5G. It doesn't stop there though. The research work on 6G has already started. The article on Why 6G? can be seen here. 

    The fourth generation or 4G is termed as LTE that is Long Term Evolution. 4G has a lot of  improvements over previous generations. (More details on that may be in another article). The one change which everyone can understand is the speed of the network or data rate. The download and upload speeds of 4G is at least 10 times more than that of 3G. The next development over 4G is 4.5G or popularly known as 4G+. The one technology that enabled 4G+ from 4G is carrier aggregation.(CA). 

Before knowing about CA, let us know what a carrier is and how it works. 

    Whenever you call or send text or do whatever on your phone connecting to the network are all considered as data. Let us say you are engaged in a call. Whatever you speak must be heard by the other person on the phone call. In other words, your words/ speech should be delivered to that person's phone. In case of wireless communication, the EM waves do that job and hence we call them as carriers. However, the EM waves span over wide range of frequency. So, are we allowed send at any frequency? The answer is No. This is where the telecom operators come in. They have permission to use certain range of frequencies which is called as band. There are different frequency bands n 4G which are called as Band-1(B1), Band-3(B3), etc (as per the 3GPP standards) (PS- they are called as 'band' only in 4G). The bands are differentiated by their center frequency or frequency range. Click here for reference,  The telecom operators divide the whole band into multiple blocks of frequency (based on standards) and allocate a block of the band to a user (in this case, you are the user, also the other person on the call) and packs his data into it and transmits it over the air to the other user, of course through cell phone towers.  The pictorial depiction is shown below.

Carrier component allocation to user

Referring to the picture above, out of allowed frequency range (spectrum) , there will be two divisions, one for transmission (uplink) and the other for reception (downlink). Say now if you make a call, a small part of frequency will be allocated from both uplink and downlink range for a user for transmission and reception in the same band. To make it simpler, let us consider both tx and rx allocation together and call it as a 'component carrier'. Now, a user is allocated one component carrier in the band whenever he uses the network. As said before, there are many 4G bands (B1/3/5/8/40...). A user is allocated a single component carrier in a single band in case of 4G. The band selected depends on the area, the cellular tower and many other things. This is how 4G works.

    4G+ or 4.5G is similar to 4G. It is technically called LTE-A or LTE-Advanced or LTE+. That means it has the same bands that are supported in 4G and rest of the things work pretty much same. But the difference is, it uses carrier aggregation. In simple terms, a user may be allocated multiple component carriers / frequency blocks compared to only one in 4G. This is helpful to achieve higher speeds on 4G+ compared to 4G. 

    There are two types in carrier aggregation : Intra band carrier aggregation and inter band carrier aggregation. In Intra band carrier aggregation, there are 2 types : Contiguous component carrier aggregation and non contiguous component carrier aggregation). To understand the same, here is a Wikipedia picture

Carrier aggregation
Source: Wikipedia

Intra band aggregation involves two or more component carriers from the same band (frequency range). If the two consecutive component carriers are allocated to the same user, then it is said to be contagious. If two distant component carriers of the same band are allocated to the same user, then it is said to be non contagious. If a user gets two or more component carrier from two or more different bands (for ex. one can be from B1 , other can be from B3) then it is called as inter band carrier aggregation.

    What does this translates in the real life user experience? Having more component carriers allocated means having more space to send or receive data. This means improved download and upload speeds. Theoretically the typical speeds in 4G is 150Mbps whereas theoretical speeds of 4G+ is around 300-450 Mbps. This indicates 4G+ is at least twice as fast as 4G. It depends on number of carrier components aggregated. More the aggregation, higher the speed.  You can reach upto the speed of 1Gbps in 4G+ (theoretically). The other advantage would be reliable network. If the phone has support for 4G+, then it would be using many component carriers. This means that even if the quality drops on one carrier, it can still use the other carrier. Thirdly, the efficient use of spectrum since unused carriers can  be allocated. 

    

    In present day, not all the 4G phones support carrier aggregation since most of them are built for 4G. The phones which support 5G will definitely support 4G+ and you can experience 4G+ on some 4G phones too. 

Hope you had a good read :))...