Note: between Sharetechnote and other online resources, this page is mostly repetitive/summaries of those pages. I hope to add and organize the Links/Sources section at the end so it’s easier to read from the source material.
When you turn on data on your phone, it connects to the nearest cell tower for communication, if one is available. A region with service is split into a bunch of cells, each serviced by 1 tower. Adjacent towers must use slightly different frequencies, otherwise they will interfere with each other. When you move from one cell to another, your current tower initiates a handover to the new tower in order to continue service with no interruption.
When you make a call between further distances, your call is transmitted wirelessly to the closest station, then (via fiber optic) between stations, then transmitted wirelessly to the recipient. Of course, in real life we have to deal with unidealities such as
Furthermore, because 5G uses such high frequencies, the gain-bandwidth tradeoff (signal attenuation is ~proportional to frequency) means that 5G signals travel especially short distances, with speeds often falling off rapidly when a phone is not in direct line of sight of a tower. In fact, for the “FR2” or mmWave-band (24-52 GHz), frequencies are so high that NO cable can transmit signals intact, and they must be sent over the air. Thus, new methods and standards are developed to combat this, described in the “Ways to increase throughput” section below.
The association that defines 5G standards is the 3GPP.
| eMBB | URLLC | mMTC | |
|---|---|---|---|
| Full name | enhanced mobile broadband | ultra-reliable low-latency comms | massive machine-type comms |
| Summary | High data rates | Mission critical | Low power wide area |
| Peak data rate | DL 20 Gbps, UL 10 Gbps | ||
| (peak spectral effy DL 30bps/Hz, UL 15bps/Hz) | 50 kbps - 10 Mbps | 1-100 kbps | |
| Latency | 4ms | 0.5ms (<1ms) | |
| Frequency range | med ~ high | med ~ high | low |
| Coverage | wide area coverage | ultra high availability | wide area coverage |
| Connection density | med | high | very high, 1 million/km^2 |
It would be wasteful to have to change our entire cell tower infrastructure every time we upgrade to 3G, 4G, or 5G, but 5G requires different hardware because (1) of the new frequency bands, and (2) increased path loss at higher frequencies. Therefore there are 2 ways a new 5G cell tower is deployed: