Trouble Shooting Guide

Axxcelera Broadband
Troubleshooting-Installing an RF link - 27 - Issue: 5.3.x
Rev 2
9.1.8 dup
The “dup” count represents cells that have been received with their sequence number to low, i.e. cells that
have been received multiple times (because they were re-transmitted over the RF link). There are two
mechanisms that cause duplicates; CELL errors and ACK errors. These are described below.
Duplicates caused by CELL errors
Up to 6 cells can be sent from any unit in a single burst. If the last cell is received in error, then only that
cell will be repeated in another frame. However, if the first cell is received in error, then all of the cells in
that burst will be repeated in another frame (i.e. six cells may be resent, even though the last five were
received correctly). This results in duplicates. If the errored cell is in the middle of the burst, then cells
from that one on will be retransmitted.
Duplicates caused by ACK errors
Another cause of duplicates is failure of the ACKs to be received at the other end of the RF link. All cells
may be received correctly, but if the ACKs sent as a result of receiving the cells are not received correctly
by the other unit then all the cells will be resent. This results in duplicates.
A high duplicate count but low CELL RxMissed and CELL RxBad counts indicates ACK problems at the
other end of the link (i.e. at one or more SU receivers). If the majority of SUs have high duplicate counts
then the problem may lie with the AP transmitter.
SU MAC Stats
The following MAC stats example is for an SU with a perfect RF link. In this example there is only
one SU (so the CELL RXOK and inseq counts are identical).
192.168.3.254 hmm> mac stats
RXOK RXMISSED RXBAD TX
FDHDR: 111296 0 0 0
RGR: 111296 0 0 3294
ACK: 3575 0 0 3564
CELL: 9732 0 0 9877
tx 9877, inseq 9732, miss 0, dup 0
ticks (20mS) since last: utopia tx 0, utopia rx 0, FDHDR RXOK 0
free list: head 921 tail 253 (delta 668)
Interpreting SU MAC Stats
9.1.9 FDHDR
FDHDR stands for Frame Description Header. These are only transmitted from an AP, and are received by
all SUs in the sector.
9.1.9.1 RX
This is the number of FDHDRs received since the MAC stats were last reset. The total of the FDHDR RX
counts should increase by about 10,000 per second, but it depends on the traffic loading and the type of