A used Huawei RRU is ready for deployment only when it has passed four checks: a physical and label inspection, a power-on test on a known-good BBU, a clean CPRI link with no active alarms, and an RF check into a proper load. This guide walks through each step for common Huawei remote radio units such as the RRU3971, RRU5904 and RRU5909, so your team can accept or reject used units before they reach a tower.
Why used RRUs need their own test routine
Remote radio units spend their working life outdoors, exposed to heat, rain, lightning surges and vibration. Most units removed during swaps or network modernisation are still healthy, but problems such as water in connectors, damaged RF ports or a faulty power amplifier branch only show up under test. Because one model name often covers several frequency bands, a unit can also be fully working and still be the wrong part for your site. A short, repeatable routine catches both kinds of problem.
Step 1: Visual and label inspection
Start before power is applied. Check the housing, heat sink fins and mounting points for cracks, corrosion or impact damage. Look at the cabling cavity and the bottom panel, where Huawei RRUs keep their external ports.
- RF antenna ports: threads clean and undamaged, centre pins straight, no burn marks or signs of water.
- CPRI optical ports: clean SFP cages with no bent contacts; keep dust caps on until testing.
- Power connector: no corrosion or heat discolouration on the DC terminals.
- Seals and covers: the cabling cavity cover and its gasket should close properly, because this is what keeps water out on site.
Then read the label. Note the model, the frequency band variant, the BOM code and the barcode/serial number, and compare them with your purchase order. An RRU3971 for 1800 MHz and an RRU3971 for 2100 MHz share a model name but are not interchangeable. A seller should be able to show the original label and serial number on every unit.
Step 2: Prepare a known-good test bench
A meaningful test needs a reference system that you trust, so any fault you see belongs to the RRU and not to the bench.
| Bench item | Purpose | Notes |
|---|---|---|
| Huawei BBU (e.g. BBU3910 or BBU5900) with main control and baseband boards | Brings the RRU into service | Software release must support the RRU model and band |
| DC power supply | Feeds the RRU | Huawei DC RRUs run on -48 V DC; check polarity before switching on |
| Optical fibre and matching SFP modules | CPRI link between BBU and RRU | Use SFPs whose rate matches the CPRI configuration |
| RF dummy loads or attenuators | Terminate every TX port | Rated for the full output power of each branch |
| Power meter or spectrum analyzer | Measure output per branch | Use an attenuator in front of the instrument |
| Cable and antenna analyzer | Return loss / VSWR of ports and jumpers | Useful to separate RRU faults from jumper faults |
For board-level details of the BBU side, see our guide to Huawei BBU5900 board compatibility, which covers which UMPT and UBBP boards work in BBU3900, BBU3910 and BBU5900.
Step 3: Power-on and status indicators
Connect all RF ports to loads first, then apply power. Never let an RRU transmit into an open port: it can damage the power amplifier and gives misleading VSWR alarms.
Huawei RRUs have a row of status LEDs covering the running state, alarms, RF activity, VSWR and the CPRI links. After the boot sequence, a healthy unit shows the running indicator blinking at the normal rate and no steady alarm indicator. LED names and patterns vary between models, so check them against the hardware description for that specific RRU rather than assuming they match another model.
If the unit shows no power indication at all, recheck the supply voltage, polarity and connector before judging the RRU faulty.
Step 4: CPRI link and BBU recognition
Connect the fibre from the BBU baseband board to the RRU CPRI port. Most Huawei RRUs have two CPRI optical ports so units can be chained or connected in a ring; test both ports, not only the first one.
- The CPRI indicator should show a locked link. A link that stays out of lock usually points to an SFP mismatch, dirty fibre or a faulty port.
- In the BBU maintenance software (LMT/MML), confirm the RRU is detected, its model and band are read correctly, and the manufacturing information (BOM code and serial number) matches the label.
- The RRU software is managed from the BBU. If the RRU version differs from the BBU release, allow the software to load and the unit to restart, then confirm it comes up cleanly.
Step 5: Alarm review
With the RRU in service, read the active alarm list. A unit you accept should show no hardware alarms, no temperature alarms and no VSWR alarms with the bench loads connected. Note any alarm that is cleared and then returns after a few minutes; intermittent faults are a common reason for units to be taken out of service in the first place.
Step 6: RF output and VSWR on every branch
Set up a test cell on the correct band and measure each transmit branch. For a 4T4R unit such as the Huawei RRU 3971-1800 or the Huawei RRU 5904-2100, that means four TX branches; a 2T2R unit such as the Huawei RRU 5909-900 has two.
- Output power on each branch should match the configured power and be consistent between branches. One weak branch is a reject, even if the others are perfect.
- Check that the carrier sits on the expected frequency and the spectrum looks clean, without unexpected spurs.
- Confirm the unit reports no VSWR alarm with good loads, then check return loss on the antenna ports with a cable and antenna analyzer if a port looks suspicious.
- If the RRU will drive remote electrical tilt antennas, check the RET/AISG function as well.
Step 7: Burn-in and final checks
Leave the RRU transmitting into loads for a burn-in period and watch for temperature alarms, output drift or link drops. After the test, refit the dust caps, close the cabling cavity cover, and record the serial number, test date and results. A simple test record per serial number makes warranty handling and later fault analysis much easier.
Quick pass/fail checklist
| Check | Pass | Reject or investigate |
|---|---|---|
| Label and band | Model, band, BOM code and SN match the order | Wrong band variant, missing or altered label |
| Housing and ports | No cracks, corrosion or damaged connectors | Water marks, burnt RF port, broken seals |
| Power-on | Normal boot, running indicator normal | No boot, steady alarm indication |
| CPRI | Both ports lock with the BBU | Link out of lock on a known-good fibre and SFP |
| Alarms | No active hardware, temperature or VSWR alarms | Any persistent or recurring hardware alarm |
| RF output | All branches at configured power | Any weak, dead or unstable branch |
FAQ
Can I test a Huawei RRU without a BBU?
You can do the visual, label and power checks without one, but the RRU will not carry traffic or report its full status without a BBU on the other end of the CPRI link. A complete test needs a BBU running a software release that supports the RRU.
Is an RRU3971 for 1800 MHz the same as one for 2100 MHz?
No. They share a model family but are built for different bands. Always confirm the band variant on the label and in the BBU before deployment.
Why does a used RRU show a VSWR alarm on the bench?
The most common causes are an open or poorly matched RF port, a damaged jumper or a wrong load. Check the bench setup first; if the alarm stays on one port with known-good loads and jumpers, the RRU port is suspect.
Does the RRU software need to be upgraded before installation?
The RRU software is handled from the BBU, so what matters is that your BBU release supports the RRU model. Let the software load during bench testing so the unit is already aligned before it goes up the tower.
Source tested Huawei RRUs and BBUs
We stock used and refurbished Huawei radio units, BBUs and boards, including the Huawei BBU 5900. Browse the full range in our Huawei category. All units are tested before shipment and covered by a 90-day warranty, and we ship worldwide in secure packaging. Contact us on WhatsApp at +86 187 3329 4669 or +86 139 3088 8705, email jack@telecombts.com, or use the form at https://telecombts.com/contact-us/.