21/07/2022
For many years, we have taken the market leading position, when it comes to delivering small-scale hybrid DAS and repeater solutions.
Typically, these smaller systems consist of a BDA with either a passive distributed antenna system or active distributed system over IP. Regardless of the system, they all share similar configurations at the front end, relying on a PTP link via a donor antenna to a donor site.
Considering these systems utilise an amplifier and a donor link, the choice of antenna can have a large impact on system performance, as it is the critical piece of infrastructure providing the communication link. All communications in and out must pass the antenna.
Other things to consider are Donor site, site capacity, and noise (broadband, PIM etc); these will all have a direct effect on system performance for the customer.
Noise is becoming increasingly problematic, leading to the development of a specific antenna solution that offers a low PIM rating and narrower beamwidths across the full cellular bands. This solution improves the donor link by reducing noise (increasing SINR1) while increasing signal strength, with successful improvement in overall system performance.
1 SINR is a measurement that gives the ratio of the total noise in the system compared to the signal; so, the stuff you do want competes with the stuff you don't and we want this value to be as high as possible.
The problem
A Nextivity Quatra installation at a site in Parkville, Melbourne, Australia was installed using a MIMO link consisting of 2x LPDA’s pointed at the local donor site
.This is considered the standard link solution for these systems, and in many cases performs well, particularly due to the additional system performance achieved having implemented a MIMO configuration for the donor link.
The following results are a screenshot taken from the Quatra Install. The measurements are taken straight from the system in real-time.
In the testing below we can see that the existing system setup is suffering from poor system performance due to the low SINR.
The SINR becomes an important measurement to us in these installs, as it indicates the quality of the network and its environment. Further to this, it can also be common to see in poor-performing systems that even though the signal strength is high, performance is degraded due to low SINR as the system struggles with the donor site. So we need a solution that considers many cases to improve performance.
The Solution
RFI worked closely with customers to design and develop the GM06-0738 mesh parabolic grid antenna. The solution needed to be all-inclusive, delivering full cellular band coverage while being lightweight, easy to install, and of high-quality construction. These attributes go a long way in providing a solution that reduces noise by being more focused on the donor site with Low PIM characteristics.
By replacing the 2 LPDA’s in a +/- 45° MIMO configuration with 2 new GM06-0738’s in a H/H* MIMO configuration, the SINR improved significantly.
| Radio | Band | Tech | SINR | SINR GM06-0738 | Eclo LPDA | Eclo GM06-0738 |
| A | 7 - 2600Mhz | 4G | 2dB | 15dB | ||
| B | 3 - 1800Mhz | 4G | -3dB | 9dB | ||
| C | 7 - 2600Mhz | 4G | 0dB | 9dB | ||
| D | 5 - 850Mhz | 3G | -16dB | -10dB |
*It should be noted that to achieve a MIMO setup, the antennas need to be installed in such a way that enough isolation occurs between the 2. In panel antennas for instance this is commonly achieved through polarisation. In our installation here, we have used spatial isolation through vertical separation. Having orthogonally opposed antennas in this vertically spaced setup will (and did) have little impact, however, due to signal multi-pathing, it is suggested that each system be optimised by trying different polarisations and isolating techniques to achieve the best result.
The full results are indicated below.
Further to improving SINR, we can also consider improvements gained in other key metrics specifically RSRP and RSRQ. When user equipment is establishing a link, it bases its connection on these 2 metrics.
RSRP, the Reference Signal Receive Power; determines the best site to connect to; the higher the number the better the better the site, and our aim to get >-80dBm.
And RSRQ, or Reference Signal Received Quality, which indicates the quality of the signal when comparing the power and noise similar to SINR. Again the best site to connect to is based in highest RSRQ and our aim here is to get >-10dB.
The following table is a summary of the improvement seen by using the GM06-0738 when compared to the preferred LPDA solution.
| Radio | Band | Tech | RSRP LPDA | RSRP GM06-0738 | RSRQ LPDA | RSRQ GM06-0738 | RSSI LPDA | RSSI GM06-0738 |
| A | 7 - 2600Mhz | 4G | -109dBm | -93dBm | -10dB | -7dB | -88dBm | -68dBm |
| B | 3 - 1800Mhz | 4G | -98dBm | -84dBm | -15dB | -9dB | -61dBm | -57dBm |
| C | 7 - 2600Mhz | 4G | -115dBm | -96dBm | -12dB | -10dB | -86dBm | -60dBm |
| D | 5 - 850Mhz | 3G | -69dBm | -57dBm |
Conclusion
By utilising the key antenna characteristics of the GM06-0738 we can improve not only system noise, but also improve other key metrics used to determine cellular connections. In doing so, we improve the performance of the system and the stability of the connection which in turn maximises performance for the customer, which is our ultimate goal.
