what is MIMO in PTP820?

There are numerous advanced microwave technologies that already enable operators to satisfy the growing demand for capacity.

- XPIC, which boost the spectral efficiency by 100%

- High Modulation, up to 1024 and 2048 QAM

- Multi-carrier link aggregation

- Header Compression

We are upon the next great leap in microwave technology that will improve spectral efficiency by another 100%: Line-of-Sight (LoS) MIMO (Multiple Input Multiple Output)

MIMO.png

A 2X2 MIMO microwave link comprises two transmitters and receivers connected to two antennas on each side.

A 4X4 MIMO is also achievable in this setup by using four transmitters and receivers in both H and V polarization.

Allen

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Spatial separation is required in a MIMO configuration.

few quesitons people ask most are:

  • Does antennas have be vertical seperation?

Answer: The separation can be either Vertical or Horizontal.

  • How far the two antennas need to be separated?

Answer: 

Spatial separation between antennas is denoted h1 and h2 respectively (in meters). To achieve the optimal perfomrance, the h1 and h2 shall meet following formula:

Picture1.png

where D - overall link distance in meters

c - speed of light (300,000,000 meter/sec)

f - link frequency in Hz

  • Do we need have same antenna separation in both side of the link?

Answer: From the formula, we know it is not necessary. Customer can have different antenna separateion on each side.

  • What if the optical antenna seperation can not be achieved, how it impacts the MIMO perfomrance?

Answer: Following chart shows how sub-optimal antenna separation affects the capacity relative to an optimal installation.

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A LoS 4X4 MIMO link can be set up by installing only two PTP820C units on each side of the link. Each unit is mounted directly onto an antenna with OMT kit, and the two units share and synchronize MIMO data.

I believe we already covered most of the topic here for MIMO. Another thing i like to address here is what if customer has to choose different antenna due to some contrains, such as tower load, etc.

So the question is:

  • Since we will need four antennas in a MIMO setup, can we have different antenna size?

Answer: Yes, you can. let's talk a look on different scenario here:

Case 1: The two antenna on same tower are same, but they are different compare to other end.

it is suppoted and nothing need to change.

Case 2: The two atenna on same tower are different, one is bigger and the other is smaller.

In this case, customer shall reduce the Tx power of the PTP820C attached with bigger antenna. The idea is to make EIRP of both antenna has same output. The reason is to acheive the optimal performance from MIMO, the RSL of both main and side path shall be similiar.

Regards

Allen

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Here is a summary of Beneift for MIMO:

  1. 4 times more capacity than a single 1+0 link, and 2 time more capacity than 2+0 XPIC
  2. Maximum Spectrum efficiency
  3. Immunity to dispersive fading with spatial antenna on MIMO
  4. Improved System gain, 3dB gain because of combined receive signal

LoS MIMO indeed revolutionizes microwave communication in terms of capacity and spectral efficiency. With LoS MIMO, network operators can enjoy all the benefits of microwave while adding significant capacity to their networks, and for very little cost.

Allen

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Hello Allenyu
 
What abouth path profiling and link budget calculations, 
what are the setup if I want to create such MIMO link in any microwave software to see what the path profiing and to analyze the link budget calaculations

adopting Mimo conifugrations it is possible to keep all the oher performance?

i mean ...uper modulations as 2048QAM can be used during MIMO operations?

thxs

Simon


@simo wrote:

adopting Mimo conifugrations it is possible to keep all the oher performance?

i mean ...uper modulations as 2048QAM can be used during MIMO operations?

thxs

Simon


Assuming you have good enough SnR, yes, 2048QAM should be possible during MIMO operations.

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The highest modulation mode can be supported under MIMO is 1024 QAM.

Depends on

  1. frequency
  2. range of the link
  3. antenna seperate on site 1 and site 2

We will be able to tell what is the MSE improvement and what is the maximum modulation the link can support.

it is still not a function yet on LINKPlanner, if you need specific figures on link planning, please contact your local RTM.


Regards

Allen

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put "X" the throughput of 1+0 2048QAM

in percentage

what can i expect to have using MIMO

take in account of:

- typical aggregation overhead to LAG XPIC and/or MIMO streams

- typical installation imperfections (sub optimum separation)

- 1024QAM limit

i would like to evaluate total cost-benefit

thx

we need following info to provide a guidance on MIMO setup

- Frequency

- Link distance

- Antenna seperation on site 1

- Antenna seperation on site 2

then we can tell what is the highest modulation the link can support.

There is no overhead for physical link aggregation. it is a proprietory for date package distribution through two RF links.

Regards

Allen


@simo wrote:

put "X" the throughput of 1+0 2048QAM

in percentage

what can i expect to have using MIMO

take in account of:

- typical aggregation overhead to LAG XPIC and/or MIMO streams

- typical installation imperfections (sub optimum separation)

- 1024QAM limit

i would like to evaluate total cost-benefit

thx



@simo wrote:

put "X" the throughput of 1+0 2048QAM

in percentage

what can i expect to have using MIMO

take in account of:

- typical aggregation overhead to LAG XPIC and/or MIMO streams

- typical installation imperfections (sub optimum separation)

- 1024QAM limit

i would like to evaluate total cost-benefit

thx




May I have a 2x2 MIMO configuration with a single dual polarized antenna at each end?

If yes, then which is the difference with an XPIC configuration?

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This is an excellent question!

XPIC

XPIC requires one dual polarity antenna at each end of the link.

An XPIC link operates on two polarities (V and H) and a single frequency pair. (The intentional cross polarization isolation at each end of the link allows the receivers to diferentiate between the two differently polarized signals. Note also that the receivers are interconnected.)

PTP 820's MIMO

PTP 820C's MIMO is Line Of Sight (LoS) MIMO. It requires LoS. PTP 820C's MIMO does not support near-LoS (nLoS) or Non-LoS (NLoS).

PTP 820C's 2x2 MIMO requires two antennas at each end of the link.

A PTP 820C 2x2 MIMO link operates on a single polarity (V or H) and a single frequency pair. (The intentional antenna spacing at each end of the link allows the receivers to differentiate between the two transmitted signals. Note also that the receivers are interconnected.)

PTP 820C's Space Diversity

PTP 820C's 1+0 Space Diversity uses 2x2 MIMO.

PTP 820C's 2+0 and 2+2 Space Diversity uses 4x4 MIMO.

SUMMARY

To summarize, an XPIC link requires two dual polarity antennas and one frequency pair (both polarities, V and H). Fewer antennas, more polarities.

A 2x2 LoS MIMO link requires four single polarity antennas (intentionally placed) and one frequency pair and one polarity. More antennas, fewer polarities.

Does this help?

Dave

Hi,

your answer is crystal clear. 

One last thing I would like to ask is that in the case of 4x4 MIMO (2 dual polarized antennas and 2 PTP 820C at each side of the link) each PTP 820C internally utilizes XPIC in order to handle the H and V polarizations. Also, the 2xPTP 820C at each side of the link are interconnected using the MIMO ports.

Correct?

Excellent!

We strive for crystal clarity!

Indeed, PTP 820's 4x4 LoS MIMO uses cross-polarization interference cancellation (XPIC) to differentiate between the V and H signals. It is not the same XPIC as a "regular" 2+0 XPIC link, though, since the receivers also have to differentiate between the upper transmitter and lower transmitter--their signals are shifted in time and arrive out of phase. (That's the part that LoS MIMO solves!)

Two PTP 820C units at the end of a 4x4 LoS MIMO link are interconnected via source sharing cable, MIMO cable, and protection cable, among other things.

A 2x2 LoS MIMO link uses both radios inside of a single PTP 820C unit--the radios are already internally connected! (The single PTP 820C unit is attached to a mediation device that connects one port to the upper antenna and the other port to the lower antenna.)

Copacetic?

Dave


@David Hensley wrote:

XPIC

XPIC requires one dual polarity antenna at each end of the link.

An XPIC link operates on two polarities (V and H) and a single frequency pair. (The intentional cross polarization isolation at each end of the link allows the receivers to diferentiate between the two differently polarized signals. Note also that the receivers are interconnected.)


Hii David,

You said XPIC requires one dual polarity antenna at each end of the link

While i create link planner like this

It's only give option like this:

What i'm trying to achive? I want to make some kind redundancy link with only 2X PTP820C and 2 Antennas, for commercial view

Yes, that looks confusing!

The "Single Pol" antennas can be converted to support two polarities with an OMT.

When you install these antennas, you remove a rectangular adaptor and replace it with a circular adaptor. This allows the antenna to carry both V and H polarities simultaneously.

(Please see the PTP 820C Radio Quick Installation Instructions for more information, including pictures of the circular adaptor.)

I hope this helps!

Dave

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