DIFI Rate Calculator

Digital IF transport carries sampled I/Q spectrum, not decoded payload. Set the four waveform parameters to size the transport line rate, and read the three nested bandwidths straight off the pulse shape: symbol rate, occupied, and the wider sampled bandwidth.

Waveform

Roll-off α0.20

Sets the occupied bandwidth, F_occ = R_s(1+α).

Oversampling υ0.25

Fractional margin above the occupied band; widens F_s by (1+υ).

I/Q bit depth N12bits

Symbol rate R_s100MSymbols/s

Packet overhead editable

Ethernet + FCS B

IP header B · 20=v4, 40=v6

UDP header B

DIFI header B

IP MTU / payload B

Context packets /s

Signal payload P_s8,944 B

Packet efficiency η_p99.18%

Context rate R_C1.23 kbps

Occupied bandwidth F_occ

120.0MHz

R_s(1+α)

Sampled rate F_s

150.0MSamples/s

R_s(1+α)(1+υ)

Raw I/Q rate

3.600Gbps

2N · F_s

DIFI line rate R_D

3.630Gbps

R_IQ / η_p + R_C

Frequency domain

Pulse Shape Symbol rate R_s Occupied F_occ Sampled F_s

Three nested widths set the transport cost. The core is the symbol-rate (Nyquist) bandwidth R_s; roll-off α widens it to the occupied bandwidth F_occ; oversampling υ widens it again to the sampled bandwidth F_s. Only out to F_occ carries signal energy — the olive margin beyond it is sampled but empty, and every hertz of it still costs 2N bits per complex sample on the wire.

Model — DIFI Expansion Factor paper

(1)F_s = R_s(1+α)(1+υ)

(1a)F_occ = R_s(1+α)

(2)R_IQ = 2N · F_s

(3)η_p = P_s / (P_s + H_E + H_IP + H_UDP + H_D)

(4)R_D = R_IQ / η_p + R_C

Defaults follow the paper: α = 0.2, υ = 0.25, IPv4 jumbo frames (MTU 9000), one 27-word context packet per second. Packet overhead is small — about 0.83% — so the DIFI line rate sits just above the raw I/Q rate. The real expansion is structural: the network transports 2N bits per complex sample across the full sampled bandwidth, not demodulated payload.

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