Aperto Packetwave Burst Error Rate (BER)

Burst error rate, BER, is cumulative ratio of burst errors (uncorrectable FEC errors + No Unique Word errors) to total number of received bursts in percentage format.

BER Includes:

- Uncorrectable FEC

Uncorrectable FEC (forward error correction) is a condition where valid burst was received and demodulated; however, there were more errors in the burst than could be corrected by the FEC.

High number of uncorrectable FEC caused by:

o low SNR (link is too long),

o multipath fading

o Interference

- No Unique Word

No Unique Word Count indicates that some energy was detected (above the minimum power threshold) during a scheduled time slot, however no Unique Word was detected.

The Unique Word is an identifier that is part of the preamble of every wireless burst and must be valid in order for a burst to be properly demodulated.

No UW on the BSU caused by interference or collisions during contention requests, and it will degrade the sector performance.

No UW on the SU caused by Interference or radio too close to base (signal should be less than –45dBm), resulting in overdriving of the SU radio.

- No Energy errors

No energy error is when scheduled packet did not arrive, or arrived with very low power level (below the minimum energy level threshold).

On the BSU: error count increases for each frame that does not have contention traffic. This is a normal condition.

On the SU: Numerous NO ENERGY errors usually indicate a VERY low signal level. SU should be pointed again

BSU in a good condition have an errors < 1-2%. BSU with errors < 5 % is still accepted.

Higher number may caused by problems such as interference and can degrade performance.

What should we do if we found that BER counter more than 5%?

1. Reset the BSU radio status counter.
2. Step up the Rx power of the BSU (up to -60 dBm).
3. Scan the frequency using the FSA tools that belong to the BSU.
4. Switch the frequency.
5. Replace the pigtail cable
6. Decrease channel width

89 – Code:1 Task SUSP tWCx

The “89 – Code:1 Task SUSP tWCx” is a minor error code and will not affect the system’s performance. This error code refers to a delay in execution of a task; however, once the delay or a single instance is triggered, the error code is reported continuously, regardless of whether the condition is there or not.

This error code is not related the SU’s / BSU’s ability to communicate with one another.

To stop the continuing reporting of this error, you can either schedule a reboot of the BSU by using telnet services or console the BSU.

Interference of Waves

As most commonly used, the term interference usually refers to the interaction of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
Wave interference is the phenomenon which occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape which results from the net effect of the two individual waves upon the particles of the medium.

Consider two waves that are in phase,with amplitudes A₁ and A₂. Their troughs and peaks line up and the resultant wave will have amplitude A = A₁ + A₂. This is known as constructive interference — a type of interference which occurs at any location along the medium where the two interfering waves have a displacement in the same direction.

If the two waves are pi radians, or 180°, out of phase, then one wave’s crests will coincide with another wave’s troughs and so will tend to cancel out. The resultant amplitude is A = | A₁ − A₂ | . If A₁ = A₂, the resultant amplitude will be zero. This is known as destructive interference — a type of interference which occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction.

When two sinusoidal waves superimpose, the resulting waveform depends on the frequency (or wavelength) amplitude and relative phase of the two waves. If the two waves have the same amplitude A and wavelength the resultant waveform will have an amplitude between 0 and 2A depending on whether the two waves are in phase or out of phase.
The task of determining the shape of the resultant demands that the principle of superposition is applied. The principle of superposition is sometimes stated as follows: When two waves interfere, the resulting displacement of the medium at any location is the algebraic sum of the displacements of the individual waves at that same location.

Aperto Packetwave Subscriber Unit (SU) Issues

SU Synchronization Issues

• Incorrect Frequency
• Incorrect Channel Width
• Incorrect BSU ID
• BSU wireless port is not operational
• SU Indoor Unit failed to detect the Outdoor Unit
• SU antenna is not pointed correctly
• The SU is out of range from the BSU and is not able to receive any signal from the BSU

SU DHCP Issues

• The DHCP Server may not have the correct reservation for the SU
• The DHCP Server may be not operational
• The SU DHCP Server entry on the BSU may not be configured correctly
• If multiple subnets are configured within the wireless port serving the SU, the DHCP Super-scope should be defined properly

SU Configuration File Issues

• The TFTP Server IP address specified in the DHCP response may be invalid
• The default gateway specified in the DHCP response may be incorrect
• Missing route on the TFTP Server
• TFTP server application is not running
• The SU may have established a two way link on the wrong sector
• Bad wireless link (Upstream)
• Even after a successful download of the configuration file, the SU might reject the file due to version incompatibility

SU Registration Problems

• The SU configuration file specifies Service Flows for which the BSU does not have any reserved bandwidth
• If the SU configuration file specifies a larger number of classifiers
• Registration would also fail if the number of service flows configured for the SU did not match with the service flows configure for the WSS
• If the number of SUs registering exceeds the number of supported SUs configure in the BSU

RF Signal Quality – No Energy Count (No Energy Error)

No energy error counters when scheduled packet did not arrive, or arrived with very low power level (below the minimum energy level threshold).

@ BSU: error count increases for each frame that does not have contention traffic. NORMAL

@ SU: Numerous NO ENERGY errors usually indicate a VERY low signal level. SU should be pointed again.

Troubleshooting should be performed via Web GUI

SOP Penggantian Base Station Radio (BSR) Aperto Packetwave

1.       Siapkan BSR pengganti yang telah dipastikan bagus (QC Passed), beserta alat dan komponen pendukung lainnya. Yakni:

-          Rubber tape

-          Coax seal

-          Silicon glue

-          Obeng kembang ( + )

-          Cutter

-          Tang pemotong

-          Konektor RJ-45 dan RG-6 (jika dibutuhkan)

-          Crimping RJ-45 dan RG-6 (jika dibutuhkan)

2.       Browse BSU yang akan diganti BSRnya.

3.       Kupas semua pelindung konektor kabel yang melekat di BSR

4.       Pada menu webGUI BSU, matikan WSS port yang akan diganti BSRnya dengan cara: klik Utility \ Device Controll \ Turn On/Off WSS

5.       Cabut kabel RG-6 yang terhubung ke BSU, diikuti dengan  mencabut kabel STP

6.       Cabut semua kabel yang terhubung ke BSR

7.       Ganti BSR lama dengan BSR yang baru

8.       Pasangkan kembali semua kabel ke BSR

9.       Pasangkan kabel RG-6, diikuti kabel STP ke BSU

10.   Nyalakan port BSU yang terhubung ke BSR yang terkait via webGUI dengan cara: Utility \ Device Controll \ Turn On/Off WSS

11.   Pastikan BSR terpasang dalam kondisi Operational; cek pada menu Status \ BSU Radio Status \ Port Status = Operational with Radio

12.   Berikan lapisan pelindung (rubber tape > coax seal > rubber tape > silicon glue) untuk semua konektor yang terhubung ke BSR.

13.   Selesai.