SimTX API v24/Packets/IqBlock

IqBlock

Packet ID	2(0x02)
Direction	Server → client
Session	Receiver
Body size	8 + chunkSamples × 4 bytes (INT16)
Permission	None
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Answers

IqBlock carries one block of received complex baseband samples. A receiver session with role 1 receives a continuous stream of them after the IqStreamDescriptor, at the rate of the simulation. Role 6 receives TimedIqBlock instead.

Layout

Field	Type	Description
packetId	u8	Always 2.
payloadLength	i32	Length of the payload in bytes. At most 1 MiB.
blockScale	f32	First 4 bytes of the payload. Scale factor for this block.
samples	chunkSamples × (I, Q)	Remainder of the payload. Interleaved I and Q integers: i16 each for INT16, i8 each for INT8.

Decoding

I = i_raw × blockScale / 32767        (INT16; use 127 for INT8)
Q = q_raw × blockScale / 32767

• A client should check that payloadLength equals 4 + chunkSamples × 2 × bytesPerComponent and treat anything else as a protocol error.
• blockScale is the block's peak component magnitude, at least 10⁻⁹. The server quantises each component as round(x × 32767 / blockScale).
• A magnitude of 1.0 corresponds to −12 dBm at the receiver input. Components are clipped at ±1.0 before quantisation, so strong signals overload the receiver.

Delivery

• Blocks are sent in real time. The server queues at most 8 blocks per connection and drops the oldest when the queue is full. Missing blocks are not marked; a client that needs to detect gaps should use role 6 and its timestamps.
• A client that does not read for 5 seconds is disconnected.

See also

• Decoding samples