Mobile Phone Technology

In a 4G-LTE environment, the available bandwidth is divided into channels, also known as component carriers. These have standard sizes of 1.4, 3, 5, 10, 15 or 20 MHz. Operators split their available bandwidth into these component channels, and users have access to one of these channels. Therefore, 20 MHz is the maximum available. In order to make better use of the narrower channels or increase the available space, a method of combining these component carriers will be needed.

In order to increase the data rate for a given user, there are only two options: widen the channel or combine channels. The latter option is available in 4G+ and is called carrier aggregation. This allows various channels to be combined, up to a maximum of five channels. Therefore, the theoretical maximum channel size is 100 MHz. However, this is only theoretical, as MNOs only have 35 MHz blocks of bandwidth available for the 2.6 GHz 4G network.

• Intra-Band Contiguous Channel: allows the user to access the space on one side of their current allocation. For example, if a user has a 5 MHz channel, they can use one of the adjoining 5 MHz channels to create a single 10 MHz channel. There is also no requirement for space between the two channels, so effectively it is a single 10 MHz channel. This process is known as 'channel bonding'.
• Intra-band non-contiguous channel: add another channel within the same bandwidth for the user's data transfer. This effectively doubles the available space for that user. However, as these channels are not contiguous, there is some overhead in delivering the data this way. The mobile operator has to manage the data between the two separate blocks. Additionally, there will be some 'dead' space in each channel to provide separation between the different channels.
• Inter-band channel: it is also possible to link one channel in one band with another in a second band. This means the user will be using two different bands to send or receive data. To achieve this, two or more serving cells are required for data transmission. The data will take a different path. One of these cells is labelled the 'primary cell' and is used to manage data from the secondary cells. Although this may result in some overhead, it enables the mobile operator to share traffic across all their available bandwidth.

Note that different carrier aggregations can be implemented on the uplink and downlink in order to make the best use of the available bandwidth.

These basics allow for quite complex carrier aggregation to be used. For operators, a large, contiguous bandwidth makes channel aggregation easier and more efficient. Currently, the bandwidth allocated to 4G and 5G operators is small and spread over various bands, which makes carrier aggregation difficult but necessary. It is generally accepted that a contiguous allocation of 100 MHz of bandwidth would make data transmission more efficient. Within the 3.4–3.8 GHz 5G allocation, the bandwidth allocated to an operator was split between two areas due to Ofcom selling the spectrum in two auctions. Following the auctions, some bandwidth swapping took place in this area to give the different operators more contiguous space.

deepl.com [AI] has been used to improve the text in this description