Mobility with mm-waves
5G specifications are extending the reach of mobile communication by supporting frequency bands up to 100 GHz. As we move to high frequencies, the wavelength of the signal moves into the millimeter range.
Available mm-Wave frequency bands
The main advantage of moving to mm-Waves is the uncommitted spectrum that can be used for 5G. The frequency bands under consideration are listed below:
mm-Waves promise a lot of spectrum, but many bring a lot of challenges:
- Wave lengths in millimeter range are obstructed by millimeter size objects. Thus, these bands work best with line of sight links. Designing a mobile network under these condition is a challenge as even the phone itself might block line of sight communication. Urban environments would experience severe path loss (refer to the following path loss map).
- Water and oxygen absorption bands result in severe attenuation in some of the frequency bands (refer to the following graph).
mm-Wave mobility in indoor and outdoor environments
The following video from Qualcomm demonstrates mm-Wave mobility in indoor and outdoor environments. A few interesting observations from the demo are:
- mm-Wave mobility requires a rethinking of the cell boundary. In many cases, a nearby gNodeB might be blocked by an obstruction and a faraway gNodeB with direct line of sight might provide the best signal quality.
- Attenuation through foliage would cause seasonal variations. A drive test carried out in the winter months may not be applicable after spring when the trees get back their leaves.
- It appears walls and partitions within offices as homes may not pose a big challenge for mm-Waves. The experiments show that US style dry wall do not cause more than a couple of dB of attenuation. This may not apply to many other countries where concrete walls are used.
The following presentation from Qualcomm details the challenges and opportunities of mm-Waves.