I was watching something on my phone and turned off my WiFi so that cellular data could load it instead (which was quicker at the time). But if it can use both separately then why can’t my phone do both at once and load things faster?
In: Technology
It might actually take longer. Cellular data and WiFi data transmit data differently….so it’s not just 1 tube for data is now 2 tubes.
It would be picture a contains 10 lines. Line 1-5 go through steps a-h. And at the same time lines 6-10 go through stems m-t…..then combine those two sets of lines.
This is slower than: connection type 1 is faster; decode 10 lines through steps a-h
It would be difficult to get it faster because the different networks have different speeds and response times. So maybe you try half and half but the WiFi packets finish before the cellular packets even start to arrive and so you just have to wait.
Also almost no one will want to use up all their cell plan data if they have a perfectly good WiFi connection on hand so almost no one would use this feature.
The short answer is that it can, but it doesn’t. In much of the world, cellular data isn’t unlimited, so to help consumers (really to prevent angry customers) out of the box phones use a single connection at a time for internet. It also has a CPU cost to re-assemble the data, so it does kill your battery quickly.
On the other hand, if you plug an Ethernet cable into your laptop while remaining on WiFi, it absolutely will use both connections when appropriate. You usually can’t tell because the wired connection is typically faster than anything on the internet, but if you transfer large files to something local, you can see it performing faster than either connection individually. Because of the cellular internet cost, however, a laptop with a cellular modem will only connect via it when no other connection is available or reliable.
Edit: there is at least a few cell phones that actually could be set to use both cellular and WiFi simultaneously, some of the last Nokia Lumia and the HP Elite x3, the last of the Windows Phone.
In theory, they could.
There are already hardware devices called a dual-WAN router that do exactly what you want, for your home network.
Now, not every connection could share both. If you have a connection between your phone and some server that stays running, like while streaming a video, for example, there isn’t really a way to send half of the data across a different path.
But, there are many cases where some traffic could be sent over cellular and some over wifi.
So why isn’t it done?
I don’t know for sure, but here are some thoughts:
1. It’d add complication, and one more way for things to go wrong. Is it really worth it?
2. The vast majority of the time, one of the two is clearly better. Almost always, wifi is much faster and lower latency if available. So it wouldn’t be worth it.
Routing.
If you have both an active WiFi connection and an active cellular data connection then your phone had two functional and valid interfaces each with its own gateway (a default route for data that can’t be sent to a local IP address) by which it can send data to the internet.
One, or both of these interfaces likely to have a layer of Network Address Translation sitting between it and the public internet. One or both may have both IPv4 and IPv6.
Most network software uses one of two transport protocols, TCP or UDP.
TCP is stateful and most of the heavy lifting is handled by the operating system. The transmitting party sends a stream of characters and the receiving party receives the stream of characters in the exact order that it is sent. TCP had no concept of message boundaries, it’s simply a stream of symbols from a sender to a receiver.
UDP is stateless. The transmitting party simply sends a message of some size and it either arrives at the receiver intact or it doesn’t.
The sender and receiver are identified by a combination of IP Address and Port, which when used together, form what’s called a *socket*. Communication occurs between sockets, not between physical devices.
A cellular device could in theory use both a socket on a WiFi interface and a socket on a cellular interface to communicate with an application server of some sort but taking advantage of the multiple network paths would require both the client and server software to be aware of the fact that multiple paths exist and that they can be used for improved data transfer.
This is certainly possible, but it puts a lot of heavy lifting on the application developer without providing a lot of benefits.
It’s just not worth it.
Cellular data and the internet are totally separate systems as far as your phone is concerned.
Let’s assume we only want to improve download speed (ignoring upload speed because that’s usually slower anyway and not as much traffic passes that way)
So our phone sent out a request. The server receives it, and then it sends the requested packets back. Already, we hit the first complication. The packets need to be split up, so half come from cellular data, and the other half need to come through wifi. That means that we need to plan out two separate routes, so all the packets likely get sent to the same local server. Half then need to go to the cellular tower and half to your home and then they are transmitted through the air to your phone, and both groups of packets need to be accepted at the same time and reorganized.
And then, if one finishes, you still need to wait for the other to finish unless you can predict how much faster one will be than the other, which is basically impossible to do accurately. Why bother with the complications of using two systems at the same time when each system already works fine on its own?
They could, but it would be incredibly complicated. It would require special resources in the network, and the benefit is not nearly as big as you might think. LTE is good for tens to hundreds of megabits per second, 5G even more. Most webpages are not limited by that speed
Wifi is usually even faster, and definitely is not a bottleneck, unless something is wrong (and, in that case most phones will flip over to cellular if the wifi is broken and not usable in some way)
Latest Answers