# Confused about the definition of point to point ,this point means single antenna or single device?

What is the definition of point to point ? does the "point" mean single device or single antenna? I mean,can one transmitter with multiple antennas and one receiver with multiple antennas be called point to point ?or we should only call it MIMO?

If there are 2 transmitters,t1 & t2,and 2 receivers,r1 & r2,and t1 will send the message to r1,but r2 will also receive the RF of t1 ;t2 will send the message to r2,but r1 will also receive the RF of t2.So in this situation,is this system also point to point? or point to multi-point

If a receiver with multiple antennas ,and there are K energy harvesters, 4 antenna for each energy harvester,and 1 receiver with single antennas.What system can we call it?MISO?or MIMO?

Point to point typically refers to single devices transmitting to each other, regardless of how many antennas they have. The important thing is that in point to point systems, there is no interference from other transmissions, you only have signal and noise.

If transmitter and receiver have multiple antennas, you would typically call it MIMO, to specify even further, the terms single user MIMO (SU-MIMO) or point to point MIMO (P2P-MIMO) are not uncommon.

If only one antenna is used for data and the others for harvesting energy, it depends on your viewpoint. If it makes sense to treat these antennas separately, i.e., ignoring the energy harvesting antennas when designing the communication link, there might be a point to call it MISO. I would assume that one also optimizes the energy transfer so that all antennas are looked at jointly. This would advocate for calling it MIMO.

*edit: Regarding the scenario you edited in later: As Blackmath correctly said, this is a classical interference channel. So it's not a point to point setup. It's also not Point to Multipoint, in which the same information is broadcast to several users. Not so in your setup as you have different intended pieces of information for your two receivers. This is an interference channel.

• so in your opinion.If a receiver with multiple antennas ,and there are K energy harvesters, 4 antenna for each energy harvester,and 1 receiver with single antennas.you will call it MIMO? – XM551 Jul 2 at 7:11
• As I said, it depends on the viewpoint. If we look at the single antenna receiver separately, it's MISO. If we look at all antennas jointly it's MIMO. Depends on what kind of optimization we're after. – Florian Jul 2 at 7:27
• If there are 2 transmitters,t1 & t2,and 2 receivers,r1 & r2,and t1 will send the message to r1,but r2 will also receive the RF of t1 ;t2 will send the message to r2,but r1 will also receive the RF of t2.So in this situation,is this system also point to point? or point to multi-point? – XM551 Jul 3 at 0:42

Point-to-point means direct (there is no intermediate node) communication between a transmitter and receiver. The transmitter and/or receiver can be equipped with multiple-antennas, and use either STBC or spatial multiplexing.

In your presented scenario, the channel is called interference channel, if the message of $$t_i$$ is intended only to $$r_i$$, but $$r_j$$ (for $$j\neq i)$$ receives the signal because of the broadcast nature of wireless channels, and that $$r_j$$ receives on the same frequency as $$r_i$$.

• so if that,it is not point to point or point to multi-point?so what is it? – XM551 Jul 3 at 1:37
• r2 is not between the r1 and t1,but near the r1 – XM551 Jul 3 at 1:38
• I know. It is called interference channel communication. Why the name is important to you? – BlackMath Jul 3 at 5:04
• because i want to know my thinking is wrong or right,that's why i want to know it can be called point to point or no!it is interference channel communication,not point to point – XM551 Jul 3 at 6:02
• When you have a transmitter and receiver communicating directly (there is no relay in between) over an orthogonal channel (no interference from other users), regardless of whether either/both is/are equipped with multiple antennas, it is point-to-point. Otherwise, it's not. – BlackMath Jul 3 at 6:30