Technology
Dynamic Spectrum Sharing Between 4G and 5G Networks
Quick fact
Dynamic spectrum sharing allows a single 5G radio wave to carry 4G and 5G signals simultaneously, and the split can change every millisecond.
Why this is interesting
Your phone just switched from 4G to 5G, but the tower hasn't changed and the antenna looks the same. How can the same slice of air carry both signals at once, without them interfering?
Read the full explanation
Understanding Dynamic Spectrum Sharing Between 4G and 5G Networks
Imagine a multi-lane highway where the number of lanes for cars (4G) and trucks (5G) can change every second. Traditional spectrum sharing would permanently paint some lanes for trucks and some for cars. Dynamic spectrum sharing (DSS) repaints the lanes in real time. In wireless networks, a base station transmits signals across a band of radio frequencies. In DSS, the base station schedules transmission resources (time and frequency) for 4G and 5G dynamically, based on current demand. The phone doesn't need to know in advance; it simply listens for its assigned resources.
A deeper explanation
The mechanism relies on the fact that both 4G (LTE) and 5G (NR) use the same underlying waveform technology—OFDM—where the spectrum is divided into small resource blocks. DSS lets the base station decide, for every transmission slot, which blocks go to 4G and which to 5G. It can even use the same block for both signals by layering them (like transmitting a 4G signal on one layer and a 5G signal on another). This requires advanced scheduling algorithms and tight coordination at the base station. The benefit is monumental: operators can roll out 5G coverage using existing 4G spectrum and equipment, avoiding the cost of new spectrum licenses and tower upgrades. It also makes the transition smoother for users, as phones automatically switch between 4G and 5G without dropped connections. However, DSS has a trade-off: because the scheduling overhead reduces efficiency, peak data rates are lower than using dedicated 5G spectrum. Understanding DSS is essential to grasping how 5G is being deployed globally, and why some 5G networks are faster than others.