What is Reddit's opinion of Introduction to Coding Theory (Graduate Texts in Mathematics, 86)?

From 3.5 billion Reddit comments

> Do they use all these bands at a time or any one of these bands?

They use two channels within a single band at any given time: one channel within the uplink frequency range of the band, and one within the downlink range. The channels can have different bandwidth.

> If such a wide-band is used for receival in a single phone, the available spectrum would get used up very quickly by very few phones itself. Wouldn't it?

Yes.

> What are the different 5G standards or future 5G standards? Is it decided yet?

6G is in development.

> Will there be Vo5GNR or VoNR standard in the future ? Are current 5G phones available in the market like iPhone-13 capable of VoNR and high-band 5G?

I don't know if that'll be used in the future. NR is mostly for high-bandwidth data, 5G is a superset of LTE so VoLTE can provide voice on 5G networks. There may not be much reason to change this, and I haven't checked.

> Is the antenna used for Bluetooth file transfer, WiFI and 4G connection the same?

No, WiFi & Bluetooth usually share an antenna (or a few antennas) separate from the cellular antennas. NFC will have yet another antenna, and wireless charging also needs its own. GPS also has a receive-only antenna.

> If a phone has Multi-User MIMO antenna system, does it mean it can transfer files at a time to like 5 users (multiple users) for example with "ShareIt" app in the case of android? Can a multi-user MIMO phone stream music to 5 different wireless earphones so that 5 people can listen to a song streamed from a single phone ?

No. Multi-user MIMO is a thing for the cellular system, not for Bluetooth.

> What are the different methods/ways of increasing the bandwidth?

https://www.amazon.com/Introduction-Coding-Theory-Graduate-Mathematics/dp/3540641335

> What is the maximum theoretically possible bandwidth? Are we reaching an upper limit for maximum possible bandwidth? Will we ever reach an upper limit?

The Shannon-Hartely theorm sets the maximum possible bitrate for a channel of a given (radio) bandwidth. The upper limit on the radio bandwidth is set by a variety of factors. The physical size of the antennas, absorption of the EM energy by the atmosphere & intervening objects, the number of simultaneous users, etc. So you might have some unused bandwidth in ITU band 12 at 300-3000GHz (1-0.1mm), but it's useless for phones, since air attenuates it entirely within a few meters. Visible light & UV doesn't go through walls, so while the 300THz-30PHz ranges are useful for fiber-optic communications it's useless for cell phones. So you can't indefinitely increase frequency and still have it be useful for communications. And since channel capacity is limited by the frequency band you're using, you can't increase it forever.