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What exactly is carrier aggregation?

tim.jtq

Super Pro Member
Hi Everyone

I think that I have been badly informed from various sources about carrier aggregation. The information on the Internet that I can find is not very clear about it.

I fully understand that carrier aggregation is basically about combining multiple channels in order to get wider bandwidth and therefore faster data transfer.

I would be very grateful indeed if someone could explain carrier aggregation to me in a way that enables me to know how it applies to 4G/5G routers, masts, cells and LTE bands.

Thank you very much.
 
I would be very grateful indeed if someone could explain carrier aggregation to me in a way that enables me to know how it applies to 4G/5G routers, masts, cells and LTE bands.
Can you narrow that down a bit?
 
A carrier is a select frequency broadcast by the network operator for the purpose of telecoms - including data.

A network operator buys licenses to use various frequencies in the spectrum - a lot of money. This means they can own the rights to use multiple carriers.

Each carrier has an allowable bandwidth the network operator can broadcast. E.g if the banding frequency was 1000 to 1040MHz then the bandwidth is 40MHz, the operator might have 10Mhz within that band for their carrier.

A cell tower (4G also known as eNodeB) is usually trying to cover the 360 degree area around it with cell signal. This is achieved by splitting it into 3 sectors. The antennas will be placed 120 degrees from each other to cover the area. Each antenna might broadcast more than one radio frequency as it'll likely be built using multiple different antenna elements within it's housing.

Each set of single carrier antenna elements and subsequent radio make up a uniquely identifiable cell for that area.

a cell tower operated by a network operator can broadcast more than 1 carrier. This means there may be multiple amounts of bandwidth available albeit broadcast on different frequencies.

the act of carrier aggregation is the ability to use these different frequency carriers, synchronise the data transfer between them based on signal quality for each one and effectively increase throughput.

just because the carriers are there, it doesn't always mean that they can be aggregated, this is determined by the hardware/software used on the tower and in some cases preferences for the area.

likewise, not all radios used in end user devices can aggregate all of the carrier frequencies - there are so many possible combinations and devices are typically designed for the part of the world they're going to.

for example, my own personal endeavour has been to make use of a node provided by Three that broadcasts band 3 1800Mhz at 15Mhz bandwidth, band 1 2100Mhz at 10Mhz bandwidth and band 32 1500Mhz at 20Mhz bandwidth that would effectively give me 45Mhz of bandwidth. However, it's been a struggle because there are so few routers and modems that can aggregate that combination mostly because B32 is a supplemental downlink only channel and not used many places in the world except the UK so hardware
is scarce. Also, manufacturers and retailers do not typically advertise possible aggregation combinations, only possible bands leading to a lot of confusion around capabilities.
 
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A carrier is a select frequency broadcast by the network operator for the purpose of telecoms - including data.

A network operator buys licenses to use various frequencies in the spectrum - a lot of money. This means they can own the rights to use multiple carriers.

Each carrier has an allowable bandwidth the network operator can broadcast. E.g if the banding frequency was 1000 to 1040MHz then the bandwidth is 40MHz, the operator might have 10Mhz within that band for their carrier.

A cell tower (4G also known as eNodeB) is usually trying to cover the 360 degree area around it with cell signal. This is achieved by splitting it into 3 sectors. The antennas will be placed 120 degrees from each other to cover the area. Each antenna might broadcast more than one radio frequency as it'll likely be built using multiple different antenna elements within it's housing.

Each set of single carrier antenna elements and subsequent radio make up a uniquely identifiable cell for that area.

a cell tower operated by a network operator can broadcast more than 1 carrier. This means there may be multiple amounts of bandwidth available albeit broadcast on different frequencies.

the act of carrier aggregation is the ability to use these different frequency carriers, synchronise the data transfer between them based on signal quality for each one and effectively increase throughput.

just because the carriers are there, it doesn't always mean that they can be aggregated, this is determined by the hardware/software used on the tower and in some cases preferences for the area.

likewise, not all radios used in end user devices can aggregate all of the carrier frequencies - there are so many possible combinations and devices are typically designed for the part of the world they're going to.

for example, my own personal endeavour has been to make use of a node provided by Three that broadcasts band 3 1800Mhz at 15Mhz bandwidth, band 1 2100Mhz at 10Mhz bandwidth and band 32 1500Mhz at 20Mhz bandwidth that would effectively give me 45Mhz of bandwidth. However, it's been a struggle because there are so few routers and modems that can aggregate that combination mostly because B32 is a supplemental downlink only channel and not used many places in the world except the UK so hardware
is scarce. Also, manufacturers and retailers do not typically advertise possible aggregation combinations, only possible bands leading to a lot of confusion around capabilities.
Thank you, Dazmatic, very much indeed for your very detailed and informative reply.

According to Cellmapper, my nearest Three tower uses Bands 1, 3 and 20. From what you say, it sounds like either the tower does not allow this particular combination to be aggregated and/or neither of the two CPE Pros can aggregate this particular combination. Could I be correct?
 
Thank you, Dazmatic, very much indeed for your very detailed and informative reply.

According to Cellmapper, my nearest Three tower uses Bands 1, 3 and 20. From what you say, it sounds like either the tower does not allow this particular combination to be aggregated and/or neither of the two CPE Pros can aggregate this particular combination. Could I be correct?
The tower might not allow it. The device seems to be capable :

 
The tower might not allow it. The device seems to be capable :

Thank you, Lucian, very much for your reply and link.

I have done some experimentation using GazzaSat's utility:


I have used this utility to restrict my CPE Pro 2 to using only Band 1 and then only Band 3 and then only Band 20. On each of these three tests, my download speed has averaged at approximately 150Mbps which is the same speed as when there is no band restriction. This tells me that something is preventing the bands from being aggregated.

I should add that I am using a Three SIM.

If Lucian is correct, then perhaps the tower is not allowing it. I wonder why.
 
Thank you, Lucian, very much for your reply and link.

I have done some experimentation using GazzaSat's utility:


I have used this utility to restrict my CPE Pro 2 to using only Band 1 and then only Band 3 and then only Band 20. On each of these three tests, my download speed has averaged at approximately 150Mbps which is the same speed as when there is no band restriction. This tells me that something is preventing the bands from being aggregated.

I should add that I am using a Three SIM.

If Lucian is correct, then perhaps the tower is not allowing it. I wonder why.
It might be special circumstances.

The B20 carrier 800MHz is of such a low frequency it can travel greater distances and penetrate through buildings, woodlands etc relatively easier than most.

It's also used on a very expansive basis to provide rural mobile covera because of this. However, it is only currently either 5 or 10MHz of bandwidth. Three and EE only have 5MHz and so they tend to not allow aggregation of B20 (and I'm speculating here somewhat) on certain masts to prevent locals sapping all of the B20 bandwidth (as their reception would be excellent) so that those further afield can still receive coverage.

There's also an element of band steering where your device is set to aggregate automatically, the tower can tell your device which band to use and which to aggregate. They can also tell how far away you are by the timing it takes for signals to pass back and forth so it wouldn't be unlikely they band steer using that information as well i.e. if you're close, don't use B20, if further away then use B20 etc but that once again is speculation - by no means an expert.

Also, you might find that the tower you're connecting to has B32 SDL. If memory serves, the Huawei routers don't show which bands your connecting to? Usually though, I've seen that where Three have B3, 1 and 20 on a mast, B32 is usually not far behind (but unusually it's enabled some time after it's gone live?) so that would probably explain why when using B20, you're still getting 150Mbps as most of the bandwidth would be coming from that.

FYI - B32 is not shown on cellmapper as it's SDL.

I'd suggest you disable B32 on the router and then try isolating the bands individually again.
 
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It might be special circumstances.

The B20 carrier 800MHz is of such a low frequency it can travel greater distances and penetrate through buildings, woodlands etc relatively easier than most.

It's also used on a very expansive basis to provide rural mobile covera because of this. However, it is only currently either 5 or 10MHz of bandwidth. Three and EE only have 5MHz and so they tend to not allow aggregation of B20 (and I'm speculating here somewhat) on certain masts to prevent locals sapping all of the B20 bandwidth (as their reception would be excellent) so that those further afield can still receive coverage.

There's also an element of band steering where your device is set to aggregate automatically, the tower can tell your device which band to use and which to aggregate. They can also tell how far away you are by the timing it takes for signals to pass back and forth so it wouldn't be unlikely they band steer using that information as well i.e. if you're close, don't use B20, if further away then use B20 etc but that once again is speculation - by no means an expert.

Also, you might find that the tower you're connecting to has B32 SDL. If memory serves, the Huawei routers don't show which bands your connecting to? Usually though, I've seen that where Three have B3, 1 and 20 on a mast, B32 is usually not far behind (but unusually it's enabled some time after it's gone live?) so that would probably explain why when using B20, you're still getting 150Mbps as most of the bandwidth would be coming from that.

FYI - B32 is not shown on cellmapper as it's SDL.

I'd suggest you disable B32 on the router and then try isolating the bands individually again.
Thank you,, Dazmatic, very much for your very informative reply.

When using GazzaSat's utility to restrict bands, the router should only connect to the bands you specify so I don't think it would have used B32 during my experiments. I think if you only specify one band to connect to then the utility completely overrides any band steering.

I have just done an experiment where I restricted the router to only B32 and my router stopped receiving any service whatsoever. It therefore looks as if there is no B32 in my area. I might be wrong though.

What is SDL?
 
I have just done an experiment where I restricted the router to only B32 and my router stopped receiving any service whatsoever. It therefore looks as if there is no B32 in my area. I might be wrong though.

What is SDL?
You can't use band 32 on its own, it has to be used along with another band.
(SDL explanation above) :)
 
You can't use band 32 on its own, it has to be used along with another band.
(SDL explanation above) :)
Thank you, The Wee Bear, very much indeed for this.

I am now guessing that perhaps GazzaSat's utility is not actually able to prevent B32 from being used. Does anyone know the answer to this?
 
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