Hello dears, what is the difference between 4G and the 5G reference signal?
To increase efficiency, and to keep transmissions contained within a slot or beam without having to depend on other slots and beams, NR introduces the following four main reference signals as compared to LTE.
What’s new in NR compare to LTE
In NR, there is not Cell-specific Reference Signal (C-RS)
New Reference Signal PTRS has been introduced for Time/Frequency tracking DMRS has been introduced for both downlink and uplink channels
In NR, reference signals are transmitted only when it is necessary whereas in LTE constantly exchanging reference signals to manage the link.
What is reference signal:
Most of the channels (e.g, PDSCH, PDCCH, PBCH etc) is for carrying special information (a sequence of bits) and they have some higher layer channel connected to them, but Reference Signal is a special signal that exists only at PHY layer. This is not for delivering any specific information. The purpose of this Reference Signal is to deliver the reference point for the downlink power.
This is the new concept introduced for the first time in 5G.
All previous technologies are always on technologies.
To increase protocol efficiency, and to keep transmissions contained within a slot or beam without having to depend on other slots and beams, NR introduces the following four main reference signals.
- Demodulation Reference Signal (DMRS)
- Phase Tracking Reference Signal (PTRS)
- Sounding Reference Signal (SRS)
- Channel State Information Reference Signal (CSI-RS)
Read following post for detailed information.
The Reference Signals in 5G NR are also different from LTE. In LTE, there are cell specific reference signals which are always enabled and cause most of the down link interference. In 5G NR, such reference signals are removed and RS are only used when the UE has data allocation. Basically, they are more like UE specific RS and act like DMRS. There are other types of RS as well like phase tracking reference signals which are used to counter phase noise at higher frequencies. This kind of structure will reduce the downlink interference and consequently improve the channel quality resulting in better spectral efficiency and capacity.
Note: LTE have Broadcasting Technique That why Cell Specif RS.
5G have Beam-farming so called UE Specific RS.
For link budget which Reference signal we need to consider and how to calculate its power taking in account total power, number of antenna ports and bandwidth?