UDP Cofdm Transceiver

COFDM Module Experiments

General Conditions
• Two (or three) COFDM modules.
• Bandwidth: 4 MHz wideband.
• Modulation settings:
• FEC: 5/6
• Modulation type: QPSK
• Guard interval: 1/4
• Traffic parameters:
• Protocol: UDP broadcast
• Packet size: 1024 KB
• Transmission rate: 100 packets per second
• Antennas are suitable for the frequency range and in good condition.
• Modules are verified to be functional.
• Multiple frequency configurations tested — the same problem occurs in all cases.
• Typical measured parameters during tests:
• SNR ≈ 25 дБ
• RSSI ≈ -25 дБм
• Issue appears only during bidirectional traffic (data sent in both directions simultaneously).
• No packet loss during unidirectional traffic.

Experiment 1

Тарам:
• Module 1:
• TX = 3180 МГц
• RX = 570 МГц
• Module 2:
• TX = 570 МГц
• RX = 180 МГц (via downconverter with 3000 MHz offset)

Result:
• Bidirectional traffic: packet loss observed.
• Unidirectional traffic: no packet loss.

Experiment 2

Тарам (same bandwidth, different frequencies):
• Module 1:
• TX = 800 МГц
• RX = 570 МГц
• Module 2:
• TX = 570 МГц
• RX = 800 МГц

Result:
• Identical to Experiment 1 — packet loss during bidirectional traffic.
• Unidirectional traffic: no packet loss.

Experiment 3

Тарам:
• Two modules from Experiment 1.
• An additional third module configured for RX only at 570 МГц.

Result:
• When the first two modules exchange data bidirectionally, the third RX-only module also experiences packet loss.
• When traffic is unidirectional between the first two modules, no packet loss is observed on any receiver.

Summary of Findings

1. Packet loss occurs only during simultaneous bidirectional transmissions.
2. Losses also affect independent RX-only receivers operating on the same frequency.
3. SNR and RSSI remain within normal ranges during the issue.
4. The problem is frequency-independent and occurs with and without frequency downconverters.

please check udp packet size, 1024kb is too long.

COFDM transceiver one-way transmission UDP Experiment 1

Setup:
● Module 1: RX = 740 МГц, TX = 850 МГц.
● FEC – 1/2
● QPSK
● Guard – 1/32
● Power attenuation – 0
● Bandwidth – 2 МГц
● Data rate = 100 packets/s, each packet 1024 KB.
Test description:
● unicast data was transferred in both directions at the same time
Result:
● When both modules transmitted in both directions at the same time,
packet loss occurred
● When data transfer was one-way only, no packet loss

Setup:
● Three COFDM modules were used
● FEC – 1/2
● QPSK
● Guard – 1/32
● Power attenuation – 0
● Bandwidth – 2 МГц
Test description:
● Module 1 transmitted unicast
● Module 2 transmitted broadcast at the same time as Module 1
● Module 3 only received the broadcast from Module 2
Result:
● With simultaneous unicast and broadcast transmission (Modules 1 жана 2
active), Module 3 experienced packet loss while receiving broadcast data
from Module 2
● When only broadcast transmission was active (without concurrent
unicast), Module 3 received data without packet loss

Setup:
● Four COFDM modules were used.
● Parameters consistent with previous experiments
Experiment description:
● Module 1 transmitted a broadcast to Module 2
● Module 4 transmitted a broadcast to Module 3
● Links were independent, and transmission was at the same time
Observation:
● Both receiving modules (2 жана 3) received their data streams without any
packet loss
RESUME: I think we have a hardware problem with the TX part of your
module. When we have TX and RX at the same time, the TX does not transmit
all packets, and we get a packet lost. The problem may be in the bus; you can
not read and write data to your TX and RX submodules at the same time