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Status as of September 2026. Covers 3GPP Rel-17 to Rel-20 NR-NTN and IoT-NTN, and ETSI EN 302 307-1/-2 (DVB-S2/S2X), TS 102 606 (GSE) and EN 301 545-2 (DVB-RCS2).

DVB-S2X is a single-carrier broadcast/broadband forward link built to get close to Shannon through a saturated transponder. 5G NR-NTN is a bidirectional, closed-loop cellular air interface: the UE compensates for the satellite channel (GNSS plus ephemeris for timing and Doppler), so that standard OFDM/HARQ/RRC machinery can serve unmodified handsets. For a VSAT or broadcast forward link, S2X remains the more power- and spectrum-efficient PHY. NR-NTN is the better system wherever mobility, handhelds, uplink multiple access and core-network integration dominate the requirements.

TL;DR

• PHY: DVB-S2X (APSK/PSK single carrier, roll-off down to 0.05, 64800-bit LDPC+BCH, 90-symbol PLHEADER, ~2.4 % pilots, VL-SNR to about −10 dB Es/N0) typically runs 2–5 dB closer to HPA saturation than NR’s CP-OFDM and carries roughly 3–5 % L1 overhead, against ~20–30 % for NR. NR-NTN answers with DFT-s-OFDM/π/2-BPSK on the uplink, UE-side Doppler/TA pre-compensation (±0.1 ppm residual frequency error), and repetition/HARQ rather than very long codewords.
• MAC: DVB relies on a gateway scheduler (ACM/VCM on the forward link; MF-TDMA with a Terminal Burst Time Plan, CRDSA/slotted ALOHA and NCR/CMT sync on DVB-RCS2 return) and has no HARQ. NR-NTN keeps dynamic and configured-grant scheduling but stretches every timing relationship (K_offset up to 1023 slots, k_mac, RTT offsets on ra-ResponseWindow, contention resolution and DRX HARQ timers), extends HARQ to 32 processes with per-process feedback disabling, and adds satellite-aware mobility (time/location CHO, Earth-fixed tracking areas).
• Fit and direction: S2X/RCS2 remains the right choice for GEO/HTS broadband, broadcast, backhaul and trunking, and DVB-NIP makes it native-IP. NR-NTN wins direct-to-device and Ku/Ka VSAT integrated with a 5GC. Rel-18 added Ka-band (n510–n512); Rel-19 (completed December 2025) adds regenerative payloads, RedCap and uplink capacity, with Ku-band in progress; Rel-20 is working on GNSS-resilient NTN and NB-IoT voice over GEO. The two ecosystems are converging at the IP/service layer, not at the waveform.

Key findings

1. The two standards split the work differently. DVB-S2X puts the complexity in the receiver: blind acquisition of large frequency offsets, VL-SNR burst detection, equalisation, and 64800-bit LDPC decoding. NR-NTN puts it in UE-side prediction: GNSS position plus the SIB19 ephemeris gives a computed timing advance and Doppler pre-correction. That lets the gNB treat NTN UEs almost like terrestrial ones, and it also makes GNSS a single point of failure, which Rel-20 is now addressing.
2. Waveform efficiency favours S2X on nonlinear transponders. ITU-R S.1878 reports that DVB-S2 single-carrier transmission through a linearised TWTA at its optimum (about 0 dB input back-off) shows essentially no loss for PSK, negligible loss for 16APSK and noticeable loss only for 32APSK. The TR 38.821 satellite EIRP densities used for NR-NTN assume the satellite HPA runs at about 5 dB back-off. ETSI TR 103 297 finds OFDMA the most penalised because of its large PAPR, with SC-FDMA about 1 dB more power-efficient than TDMA in its study.
3. The operating SNR regimes barely overlap. An NR handheld on an S-band LEO works around 0–10 dB C/N with G/T about −31.6 dB/K and 23 dBm/0 dBi uplink EIRP. A DVB-S2X VSAT or DTH terminal works around 5–20 dB Es/N0, and a professional trunk up to 20+ dB, where 256APSK (about 5.9 b/sym) becomes usable.
4. Latency handling is the core of NR-NTN’s MAC changes. A GEO transparent RTT of 541.46 ms, against 25.77 ms for a 600 km LEO, drove K_offset (1..1023 slots of 15 kHz), 32 HARQ processes, HARQ feedback disabling, uplink HARQ mode B, and RTT-offset timers. DVB avoids the problem with no HARQ at all (strong FEC at QEF plus upper-layer ARQ/TCP acceleration) and a scheduler that works on superframe timescales.
5. Overhead: S2X with pilots plus GSE loses roughly 3–5 % to L1/L2 framing, plus the roll-off excess bandwidth (5–35 %). NR loses ~7 % to the CP, 7–14 % to DMRS, 7–21 % to PDCCH, a few percent to SSB/CSI-RS/TRS, and 5–8 % to guard bands. What NR gets for that overhead is per-slot (0.125–1 ms) multi-user scheduling, MIMO and HARQ.

1. Scope, architecture and releases

Item	5G NR-NTN	DVB-S2/S2X family
Core specs	TS 38.211/212/213/214 (PHY), 38.300 (§16.14 NTN), 38.321 (MAC), 38.331 (RRC), 38.101-5 (NTN UE RF), TR 38.811/38.821 (studies)	EN 302 307-1 (S2), EN 302 307-2 (S2X, incl. Annex E superframes and beam hopping), TS 102 606 (GSE), EN 301 545-2 (RCS2 lower layers), TS 101 545-1 (RCS2 system), TS 103 876 (DVB-NIP)
Payload	Rel-17/18: transparent (gNB on the ground). Rel-19: regenerative (gNB on board)	Transparent or regenerative; payload-agnostic
Orbits	GEO, LEO (600/1200 km reference), MEO	Any; historically GEO; S2X Annex E and VL-SNR target mobile/HTS
Duplex	FDD only in NTN bands	Forward: continuous TDM. Return: MF-TDMA (RCS2) or SCPC
Terminal classes	Handheld PC3 (23 dBm, 0 dBi), IoT (NB-IoT/eMTC), VSAT/ESIM (Rel-18 Ka), RedCap (Rel-19)	DTH receivers, VSAT/RCST, SNG, professional trunking, mobile (aero/maritime)

Release timeline

• Rel-17 (frozen 2022): first normative NTN release. Transparent payload, FDD FR1 bands n255 (L: UL 1626.5–1660.5 / DL 1525–1559 MHz) and n256 (S: UL 1980–2010 / DL 2170–2200 MHz), GNSS-capable UEs assumed, Earth-fixed tracking areas, and IoT-NTN in parallel.
• Rel-18 (June 2024): bands n254 (UL 1610–1626.5 / DL 2483.5–2500 MHz) and the Ka bands n510/n511/n512 (UL 27.5–30 GHz, DL 17.3–20.2 GHz) for VSAT/ESIM; a 30 MHz channel bandwidth in FR1-NTN; PUCCH repetition for Msg4 HARQ-ACK and PUSCH DMRS bundling; network-verified UE location; NTN–TN mobility enhancements.
• Rel-19 (completed December 2025): regenerative payload; DL coverage enhancements with new reference payload parameters (lower EIRP density per beam, beam power sharing); UL capacity via OCC-overlaid repetitions; RedCap in FR1-NTN; intended-service-area signalling for MBS broadcast; IoT-NTN store-and-forward on regenerative payloads, UL capacity and NB-IoT public warning; higher UE power classes and a 3 MHz channel bandwidth; a Ku-band workplan (13.75–14.5 GHz UL, 10.70–12.75 GHz DL).
• Rel-20 (in progress): GNSS-resilient NR-NTN; NB-IoT voice over GEO, including UE transmit power up to 37 dBm; connected-mode LTE-TN ↔ NR-NTN mobility; the 6G study with NTN as part of the unified design. Stage-3 is targeted for March 2027 and the ASN.1 freeze for June 2027.

2. Waveforms, PAPR and power amplifiers

NR-NTN. The downlink is CP-OFDM. The uplink is CP-OFDM or DFT-s-OFDM (transform precoding), optionally with π/2-BPSK. Rel-17 reused the terrestrial waveforms unchanged. Typical 10⁻⁴ CCDF PAPR is about 10–12 dB for CP-OFDM, about 7–8 dB for DFT-s-OFDM QPSK, and about 4–5 dB for π/2-BPSK DFT-s-OFDM (generic engineering values, not 3GPP-specified). A satellite HPA carrying an NR downlink therefore has to sit several dB below saturation; TR 38.821 assumes about 5 dB back-off. A handset uplink is limited by the 23 dBm PC3 cap and MPR/A-MPR, so DFT-s-OFDM with π/2-BPSK is the coverage-limited mode.

DVB-S2/S2X. Single-carrier, root-raised-cosine shaped (roll-off 0.35/0.25/0.20 in S2, plus 0.15/0.10/0.05 in S2X), with QPSK, 8PSK, 8/16/32/64/128/256APSK, and π/2-BPSK in the header and VL-SNR modes. APSK uses few concentric rings, which keeps PAPR low and makes predistortion simple. S2X also defines “-L” MODCODs optimised for quasi-linear, multi-carrier-per-HPA operation with phase noise, gaining up to ~1 dB in some cases. The DVB channel models A (ideal linearised hard limiter) and B (IMUX/OMUX, nonlinear TWTA with AM/AM and AM/PM, ACI) optimise output back-off per MODCOD.

Roll-off in practice. Per the DVB-S2X white paper, going from α = 0.20 to 0.05 under a (1+α) bandwidth rule raises symbol rate by about 14 %, but receiver noise rises about 0.6 dB, so the net spectral-efficiency gain is about 7 % (DTH) and 8–11 % in the professional SNR range. With free symbol-rate optimisation through a real transponder the gain is below 2 %, and with rising uplink ACI 20 % roll-off can even beat 5 % by 0.1–0.2 dB. NR’s equivalent is its guard band: 106 PRBs in 20 MHz at 15 kHz SCS is about 95.4 % occupancy.

Nonlinear predistortion. For S2X, per-ring DPD on the gateway uplink and on-board linearisers are standard practice, and equalisers in enhanced receivers recover 7–9 % spectral efficiency at high symbol rates. For NR through a transparent payload, satellite HPA nonlinearity lands inside the OFDM EVM budget and cannot be undone by UE-side equalisation, so operators back off, use CFR and DPD in the gateway chain, or apply them on board with regenerative payloads. A single-carrier NTN downlink option is being discussed for 6G but is not in any 5G release.

3. Numerology, frame structure and pilots

Parameter	NR-NTN	DVB-S2/S2X
Basic unit	OFDM symbol; slot = 14 symbols; 10 ms frame, 1 ms subframe	90-symbol SLOT; PLFRAME = PLHEADER (1 slot) + S slots of XFECFRAME
SCS / symbol rate	FR1-NTN: 15/30 kHz (60 kHz for some bandwidths); Ka: 60/120 kHz, SSB 120/240 kHz	Any symbol rate; common VSAT/DTH 1–70 Mbaud; wideband S2X to ~500 Mbaud
Channel BW	n255: 5–20 MHz; n256: 5–20 + 30 MHz; n254: 5–15 MHz; n510–512: 50/100/200/400 MHz	Rs(1+α), e.g. 36 MHz transponder → ~30–34 Mbaud
Slot duration	1 ms (15 kHz), 0.5 ms (30 kHz), 0.125 ms (120 kHz)	PLFRAME ≈ 8100–33 282 symbols (~1.1 ms at 30 Mbaud for 64800-bit 8PSK)
Header	No per-slot header; PDCCH/DCI carries allocation	PLHEADER: 26-symbol SOF + 64-symbol PLSCODE (π/2-BPSK)
Pilots	DMRS, PTRS, CSI-RS/TRS, SRS	Optional 36-symbol pilot block every 16 slots → ≈2.4 %
Superframe	None (SFN/hyperframe numbering only)	S2X Annex E: 612 540 symbols; SOSF 270 + SFFI 450 symbols; formats 0–5

PLHEADER robustness. The S2 header works reliably to slightly below Es/N0 = −2.5 dB. S2X added a separate 900-symbol VL-SNR header identifying 9 MODCODs plus a dummy frame, keeping the length of a standard PLFRAME so legacy receivers can skip it without losing lock.

Annex E superframes. Formats 0–4 are all 612 540 symbols. The SOSF uses one of 256 orthogonal Walsh-Hadamard sequences (a per-beam signature). Formats 0/1 give about 2.56 % pilot density. Formats 2/3 bundle constant-size, aligned PLFRAMEs across co-channel beams, enabling multi-user detection and gateway precoding; DVB cites 20–100 % capacity gains with full or two-colour reuse. Format 4 targets wideband and VL-SNR use. Format 5 (beam hopping) allows variable superframe length so dwell times line up with the Beam Hopping Time Plan.

NR reference signals. In NTN, DMRS density is the main knob against Doppler residuals, plus Rel-18 PUSCH DMRS bundling for coherent combining across slots. PTRS matters mainly at Ka (120 kHz SCS). CSI reporting works as usual but on GEO the CSI is about 0.54 s stale when used.

4. Modulation, coding and efficiency

NR. QC-LDPC for data (BG1: mother rate 1/3, max 8448-bit information block; BG2: 1/5, 3840 bits; lifting sizes up to Z = 384; IR-HARQ with four redundancy versions). Polar codes for DCI, UCI and PBCH. Modulation from π/2-BPSK (UL) to 256QAM (1024QAM DL in FR1). MCS tables run from QPSK 30/1024 (≈0.059 b/RE) to 256QAM 948/1024 (7.41 b/RE). Link adaptation targets about 10 % initial BLER and relies on HARQ.

DVB-S2/S2X. BCH outer plus LDPC inner, 64800-bit normal and 16200-bit short frames (S2X adds VL-SNR medium frames). S2 has 28 MODCODs, from QPSK 1/4 at about −2.35 dB Es/N0 to 32APSK 9/10 at 16.05 dB. S2X adds finer code rates, 64/128/256APSK and -L variants, shrinking MODCOD spacing from 1–1.5 dB to about 0.4–0.5 dB. 256APSK 3/4 carries 5.90 b/sym at an ideal linear-AWGN Es/N0 of 19.57 dB (roughly 24 dB in the nonlinear channel at about 4 dB OBO). VL-SNR adds nine MODCODs using π/2-BPSK (the two lowest spread ×2) and QPSK 2/9, operating quasi-error-free down to near −10 dB Es/N0.

Distance to Shannon. QPSK 1/2 at 1.0 dB is about 1 dB from capacity; 256APSK 3/4 is about 1.9 dB away because of shaping loss. NR at 10 % BLER with short codewords is about 1–2 dB from the bound per transmission, and HARQ recovers part of that at the cost of RTT — exactly what NTN latency makes expensive.

	NR-NTN	DVB-S2X
Lowest operating point	QPSK 30/1024 + repetition; IoT-NTN adds up to thousands of repetitions	π/2-BPSK 1/5 spread ×2, about −10 dB Es/N0
Highest	256QAM 948/1024 (7.41 b/RE), 1024QAM DL (FR1)	256APSK 3/4 (5.90 b/sym)
Codeword	≤8448 info bits per code block	64800 / 32400 / 16200 bits
Error target	10 % BLER + HARQ	QEF (no retransmission)
Link adaptation granularity	~1–2 dB MCS steps, per slot	0.4–0.5 dB MODCOD steps, per PLFRAME

5. Synchronisation and low-SNR acquisition

NR. The SSB is PSS and SSS (127 subcarriers each) plus PBCH in 4 symbols × 240 subcarriers. Initial LEO Doppler reaches 24 ppm: ±48 kHz at 2 GHz, ±480 kHz at 20 GHz, ±720 kHz at 30 GHz, so the UE must test several PSS frequency hypotheses on top of crystal error. Doppler rate reaches about −544 Hz/s at 2 GHz (TR 38.811), or 0.27 ppm/s at 600 km. After DL sync the UE computes the uplink Doppler from GNSS plus ephemeris and pre-compensates; TS 38.101-5 requires the UE carrier within ±0.1 ppm of the ideally pre-compensated reference. Timing follows T_TA = (N_TA + N_TA,offset + N_TA,adj common + N_TA,adj UE)·T_c.

DVB-S2/S2X. Blind acquisition via 26-symbol SOF correlation, PLSCODE decoding and pilot-aided tracking. Receivers typically handle coarse frequency offsets of the order of 20 % of the symbol rate (an implementation figure), which covers LNB drift and GEO Doppler easily. VL-SNR detection at −10 dB needs very narrow loop bandwidths (around 10⁻⁴ normalised), which lengthens acquisition and limits tracking of fast Doppler. On LEO a raw S2X receiver therefore needs ephemeris-driven NCO pre-correction, just as NR does — DVB simply never standardised that aiding.

DVB-RCS2 return link. Terminals derive time from the Network Clock Reference on the forward link, log on in dedicated or random logon slots (with support for large timing uncertainty), and receive burst frequency, timing and amplitude corrections via the Correction Message Table — the functional analogue of NR’s TA command plus TPC, but slower and aimed at GEO.

6. Doppler and delay: numbers side by side

Quantity (TR 38.821 / 38.811)	GEO	LEO 1200 km	LEO 600 km
Max RTT, transparent	541.46 ms	≈41 ms	25.77 ms
Max RTT, regenerative	270.73 ms	≈20.5 ms	≈12.9 ms
Max differential delay in cell	≈10.3 ms	—	≈3.12 ms
Max Doppler (Earth-fixed UE)	0.93 ppm	21 ppm	24 ppm

NTN-Config (SIB19) carries the ephemeris (state vectors or orbital elements with epoch time), ta-Common (up to about 270.73 ms full scale) and its drift terms, cellSpecificKoffset (1..1023 slots of 15 kHz, i.e. up to about 1.023 s, covering the GEO RTT), kmac (1..512 slots), and ntn-UlSyncValidityDuration (5 s to 900 s, driving timer T430). K_offset stretches every UL-after-DL relationship: DCI→PUSCH, RAR→Msg3, PDSCH→HARQ-ACK and MAC CE activation. DVB-S2X needs none of this on the forward link because nothing in it depends on round-trip timing.

7. Link budgets, terminals and bands

TR 38.821 Set-1 (per beam)	GEO S	LEO-600 S	GEO Ka	LEO-600 Ka
Satellite DL EIRP density	59 dBW/MHz	34 dBW/MHz	40 dBW/MHz	4 dBW/MHz
Tx gain / aperture	51 dBi / 22 m	30 dBi / 2 m	58.5 dBi / 5 m	38.5 dBi / 0.5 m
Beam diameter	250 km	50 km	110 km	20 km
Satellite UL G/T	19 dB/K	1.1 dB/K	28 dB/K	13 dB/K

• Handheld: 23 dBm and 0 dBi, linear polarisation, NF 7 dB, giving DL G/T about −31.6 dB/K, plus a 3 dB polarisation mismatch against a circularly polarised satellite.
• Ka VSAT: 60 cm equivalent aperture, 39.7 dBi Rx / 43.2 dBi Tx, NF 1.2 dB, giving DL G/T about 15.9 dB/K and UL EIRP 76.2 dBm.
• The gap: VSAT G/T is about 47.5 dB better than the handheld’s. That single figure explains why S2X-class high-order MODCODs make sense for VSATs and not for phones.
• DVB regimes: Ku/Ka DTH with 45–90 cm dishes (G/T around 10–18 dB/K) runs at 5–14 dB Es/N0; DSNG at 10–14 dB; trunking at 12–18 dB; VL-SNR mobile at −10 to −2 dB.

RF front-end implications. L/S NR handhelds have no antenna gain, so the system closes the link with satellite aperture (AST’s arrays are about 223 m²). Handset priorities are PA efficiency at 23 dBm with DFT-s-OFDM MPR, a low-NF LNA, and coexistence filtering (n256 overlaps terrestrial n65/n66; n255 overlaps n24/n99). Ka VSAT phased arrays for either standard need a few hundred to a few thousand elements; an NR VSAT must additionally track ±480 kHz (DL) and ±720 kHz (UL) Doppler and TA drift at LEO and support mobility RRM.

8. Multi-beam, beam hopping and MIMO

NR-NTN: typically one satellite beam per cell or per SSB beam; frequency reuse 1, 3 or 4 via carriers or BWPs; polarisation (RHCP/LHCP/linear) can be signalled so it serves as a reuse colour. Handhelds are 1T2R-class, so single-layer links are the rule; multi-satellite schemes remain research or 6G items.

DVB-S2X: beam hopping (Format 5) with a Beam Hopping Time Plan; co-channel interference handled with orthogonal SOSF/pilot codes and seven selectable Gold scrambling codes; precoding and MUD via formats 2/3; channel bonding of up to 2–3 transponders (CCM only) for statistical multiplexing.

9. Phase noise, interference and nonlinearity

• OFDM turns phase noise into CPE plus ICI, which argues for wider SCS at Ka plus PTRS. Its high PAPR produces in-band EVM and spectral regrowth that a single-tap equaliser cannot remove.
• High-order APSK is sensitive mainly to low-frequency phase noise on its outer rings; 256APSK needs integrated phase error well under 1° rms after the carrier loop. S2X supplies phase-noise masks (Annex H.8) for design.
• Interference: NR relies on beam isolation and frequency reuse with PCI-based scrambling. S2X has selectable Gold codes and orthogonal superframe sequences, and PL descrambling spreads a narrower co-channel interferer, reducing its effect.

10. MAC and upper layers

10.1 Resource allocation and scheduling

	NR-NTN	DVB-S2X forward / DVB-RCS2 return
Granularity	PRB × slot (0.125–1 ms), per UE, per HARQ process	Forward: BBFRAME/PLFRAME per MODCOD (ACM) or per stream (VCM). Return: MF-TDMA slot per superframe (tens of ms)
Grant signalling	DCI on PDCCH; configured grant type 1/2; SPS	Forward: implicit (receiver filters by ISI/label). Return: TBTP2 broadcast on the forward link
Capacity request	SR (PUCCH) + BSR MAC CE	CRA, RBDC, VBDC, FCA capacity categories
Delay impact	K_offset on all DL→UL timings; GEO SR→grant→PUSCH ≈ 2 RTT ≈ 1.1 s unless configured grant	GEO VBDC request→allocation ≈ 0.6–0.7 s; CRA/FCA and RA hide it

10.2 HARQ vs FEC-only

• NR-NTN (Rel-17): up to 32 HARQ processes in DL and UL; per-process downlink HARQ feedback disabling (reliability then falls back to RLC ARQ and a lower BLER target); uplink HARQ mode A/B per process; DRX HARQ RTT timers extended by the UE-gNB RTT. NB-IoT NTN has only 2 HARQ processes, so HARQ disabling (Rel-18) is essential there. Section 13 below walks through the mechanics in detail.
• DVB: no HARQ at all. S2X targets QEF with 64800-bit LDPC and relies on ACM margin, TCP acceleration/PEP and application FEC. On GEO that is rational: a HARQ retransmission costs about 0.55 s, a delay DVB systems would rather spend as margin.

10.3 Random access

• NR-NTN: 4-step and 2-step RACH with full TA and Doppler pre-compensation applied to PRACH. ra-ResponseWindow and msgB-ResponseWindow start after the UE-gNB RTT estimate; ra-ContentionResolutionTimer starts after Msg3 plus the RTT. Msg3 repetition and Msg4 PUCCH repetition (Rel-18) close the link for handsets.
• DVB-RCS2: slotted ALOHA for logon/control slots (throughput peaks at 0.36 packets/slot); CRDSA transmits multiple burst replicas and cancels interference, raising throughput several-fold at the same packet loss rate, with back-pressure control in the FAT.

10.4 Timers, link adaptation and feedback

Rel-17 extended value ranges across the NR stack (sr-ProhibitTimer, BSR retransmission, RLC t-Reassembly and t-StatusProhibit, PDCP discardTimer and t-Reordering, the RLF family, NAS timers for GEO). LEO geometry is predictable, allowing elevation-based open-loop link adaptation; at GEO the CQI is about 0.54 s old. In DVB-S2X ACM, terminals report forward-link SNR over the return channel and the gateway picks a MODCOD with hysteresis. With a GEO loop delay of 0.5–0.7 s and Ka rain fades evolving at 0.1–1 dB/s, ACM margin is typically 0.5–1 dB — which is why S2X’s fine MODCOD spacing matters.

10.5 Mobility, paging and tracking areas

NR-NTN has Earth-fixed tracking areas (no TAU storms as beams sweep), conditional handover with time and location triggers, location/time-based measurement triggering with neighbour-satellite ephemeris in SIB19, and feeder-link switchover for transparent LEO. Rel-18 improved NTN–TN mobility, Rel-19 adds mobility for regenerative payloads, and Rel-20 adds connected-mode LTE-TN↔NR-NTN. DVB’s model is largely static: a terminal is provisioned to a gateway and beam, and beam or satellite handover (maritime/aero) is vendor-specific, with no standardised equivalent of paging, tracking areas or CHO.

10.6 Encapsulation, framing and QoS

NR: SDAP (QoS flow→DRB), PDCP (ciphering/integrity, ROHC), RLC (UM/AM, segmentation) and MAC (multiplexing, MAC CEs) add roughly 6–10 bytes per IP packet before ROHC. 5QI QoS runs end to end with the 5GC, and NR(LEO)/NR(MEO)/NR(GEO) RAT types tell the core the access is satellite.

DVB: an 80-bit BBHEADER followed by a data field of up to ~7 kB. Input is MPEG-TS (IP via MPE/ULE, about 10 % overhead) or Generic Stream with GSE (minimum 2-byte header, labels, fragmentation, CRC-32 on the last fragment only), cutting overhead to about 2–3 % for 5–15 % throughput gain. Each ISI stream can carry a different QoS or MODCOD class. DVB-NIP (TS 103 876) replaces TS entirely with IP over GSE, with multicast via FLUTE/ROUTE and DVB-I service discovery.

10.7 Overhead as a share of capacity (indicative)

Component	NR-NTN DL (20 MHz, 15 kHz, SISO)	DVB-S2X forward (normal frames, pilots on)
Spectral occupancy	95.4 % (106 PRB)	1/(1+α): 95 % (α=0.05) … 74 % (α=0.35)
Cyclic prefix / header	≈6.7 % CP	PLHEADER: 0.3–1.1 %
Pilots / RS	DMRS 7–14 %, CSI-RS/TRS 1–3 %, SSB ~1–4 %	2.4 % (plus superframe ≈0.1–2.6 %)
Control	PDCCH 7–21 %	None in-band (tables, typically under 1–2 %)
L2	≈6–10 B per IP packet (~1–2 % at 600 B)	BBHEADER ≈0.1–0.5 %, GSE 2–3 %
Total (indicative)	≈25–35 % of the raw OFDM grid	≈3–6 % plus roll-off excess

These totals are engineering estimates from the frame structures, not figures from a standard.

10.8 Latency and throughput

GEO transparent one-way UE→gNB is about 270 ms plus processing; LEO-600 is about 13 ms one-way at worst, and regenerative payloads roughly halve that. S2X in a 36 MHz transponder delivers about 60–200 Mbit/s depending on MODCOD, and wideband carriers reach Gbit/s. NR-NTN handheld evaluations and commercial systems show single-digit to tens of Mbit/s per beam. AST SpaceMobile advertises peaks above 150 Mbps per coverage cell (vendor design targets), while a crowdsourced study estimates Starlink Direct-to-Cell at about 3.1 Mbit/s downlink per beam.

11. IoT-NTN in brief

NB-IoT and eMTC over NTN (Rel-17) use the same broadcast ephemeris and common-TA concept with GNSS-based pre-compensation. NB-IoT’s 2 HARQ processes and repetition-heavy operation make HARQ disabling and RLC ARQ central. Rel-18 added HARQ disabling, improved GNSS-measurement gaps and discontinuous-coverage support; Rel-19 adds store-and-forward on regenerative payloads; Rel-20 targets NB-IoT voice over GEO. DVB has no equivalent.

12. Where each excels, and convergence

Use case	Better fit	Why
DTH/broadcast, multicast CDN feed, DVB-NIP	DVB-S2X	Near-saturation single carrier, QEF, massive multicast efficiency, deployed ecosystem
GEO/HTS broadband VSAT	DVB-S2X + RCS2 (or S2X-based return)	Proven ACM, beam hopping and precoding hooks, ~3–5 % overhead
5G backhaul / trunking	DVB-S2X today; NR-NTN Ka VSAT emerging	256APSK at high SNR vs native 5GC integration
Direct-to-device smartphones	NR-NTN (and LTE-based D2D)	Unmodified handsets, standard chipsets, mobility, core integration
Massive IoT via satellite	IoT-NTN	PSM/eDRX, repetition, store-and-forward
Aero/maritime mobility	Both	NR has standard mobility; S2X has the better forward link

Convergence is happening at the IP and service layer: DVB-NIP makes S2X a native-IP multicast bearer compatible with 5G media delivery, DVB-I spans DVB, 5G Broadcast and unicast, and S2X is widely used for 5G backhaul. On the 3GPP side, Rel-19 adds broadcast service-area signalling and a Ku-band workplan, putting 3GPP directly into DVB’s traditional spectrum. 6G studies target a unified TN/NTN radio, GNSS-independent operation, and possibly a low-PAPR downlink option. Expect a multi-orbit mix: S2X for GEO broadband and broadcast, NR-NTN for D2D and IoT, integrated at the IP level.

13. HARQ transmission and the baseband chain to the DAC/ADC

HARQ is the single biggest structural difference between the two air interfaces, and it is easiest to understand by following a transport block through the whole baseband chain. This section explains how NR HARQ works, what NTN does to it, and then walks both transmit chains from input bits to the DAC (and the receive chains back from the ADC).

13.1 How NR HARQ works

• Parallel stop-and-wait processes. Each HARQ process sends one transport block and waits for its ACK/NACK; many processes run in parallel so the link stays busy during the wait. The scheduling DCI carries the HARQ process number (4 bits for 16 processes, 5 bits when 32 are configured in Rel-17), a new-data indicator (NDI, toggled for a new TB, unchanged for a retransmission) and a 2-bit redundancy version (RV).
• Incremental redundancy via a circular buffer. After LDPC encoding, the systematic and parity bits of each code block are written into a circular buffer. Each transmission reads E bits out of it, starting at one of four positions set by the RV. RV0 and RV3 start near the systematic bits and are close to self-decodable; RV2 and RV1 mostly add fresh parity. A common retransmission order is 0 → 2 → 3 → 1. Limited-buffer rate matching (LBRM) can cap the buffer to bound UE soft-buffer memory.
• Soft combining at the receiver. The receiver de-rate-matches each transmission’s LLRs back into their buffer positions and adds them to what it stored from earlier attempts, then runs LDPC decoding on the combined buffer. The TB and code-block CRCs decide ACK or NACK.
• Feedback. Downlink ACK/NACK goes back on PUCCH (or multiplexed on PUSCH) in slot n + K1, packed into a HARQ-ACK codebook: Type 1 (semi-static), Type 2 (dynamic, ordered by DAI) or Type 3 (one-shot report of all processes). With code-block-group (CBG) transmission, the TB is split into 2, 4, 6 or 8 CBGs and only the failed groups are resent.
• Uplink. NR uplink HARQ is asynchronous and adaptive: there is no PHICH, and the gNB triggers a retransmission simply by scheduling the same process number with NDI not toggled.

13.2 What NTN does to HARQ

To keep one UE continuously scheduled, the number of HARQ processes must cover the round trip: N_HARQ ≥ (RTT + processing time) / slot duration. With 1 ms slots (15 kHz SCS):

Scenario (transparent)	Max RTT	Processes needed (approx.)	Effect with 32 processes
Terrestrial	<1 ms	~8–16	Plenty
LEO 600 km	25.77 ms	~27–30	Just fits
LEO 1200 km	≈41 ms	~42+	Stalls without feedback disabling
GEO	541.46 ms	~542	With feedback on, one UE gets at most ~32/541 ≈ 6 % of slots

At 30 kHz SCS the slot halves and the required process counts double. The Rel-17/18 answers are:

• HARQ feedback disabling per downlink process. A disabled process can be reused immediately. Reliability then comes from a more conservative MCS (lower BLER target), blind repetition (pdsch-AggregationFactor n2/n4/n8, PUSCH repetition) and RLC ARQ above the MAC.
• Uplink HARQ mode B. The UE does not have to wait out the RTT before a mode-B process can carry new data.
• Stretched timing. PDSCH-to-HARQ-ACK timing becomes K1 + K_offset, and the DRX HARQ RTT timers add the UE-gNB RTT for feedback-enabled processes.
• Silicon cost. Going from 16 to 32 processes can double the worst-case HARQ soft-buffer storage in the UE modem unless LBRM or the UE’s declared capability limits it. That is a direct SRAM and area cost for the receiver IC.
• IoT-NTN. NB-IoT has only 2 HARQ processes, so feedback disabling (Rel-18) matters even more there.

13.3 The NR transmit chain, from bits to DAC

ShareTechnote’s 5G/NR PDSCH page has an excellent diagram of the 12-step PDSCH transport process, with the 3GPP clause for each step. As it points out, steps 1–6 (TS 38.212) work on bits and steps 7–12 (TS 38.211) work on symbols and resources, so knowing which half a problem is in narrows it down quickly. The table below follows the same steps and extends the chain past resource mapping to the DAC, marking where HARQ and NTN come in.

#	Step	Spec	What it does	HARQ / NTN relevance
1	TB CRC attachment	38.212 §7.2.1	24-bit CRC if TB size A > 3824, else 16-bit	TB CRC decides the final ACK/NACK
2	LDPC base graph selection	38.212 §7.2.2	BG2 if A ≤ 292, or A ≤ 3824 and R ≤ 0.67, or R ≤ 0.25; otherwise BG1	Fixed per TB, so identical on every retransmission
3	Code block segmentation + CB CRC	38.212 §7.2.3 (§5.2.2)	Split into code blocks of at most 8448 (BG1) or 3840 (BG2) bits, 24-bit CRC each	Code blocks are grouped into CBGs for partial retransmission
4	LDPC encoding	38.212 §7.2.4	QC-LDPC, lifting size up to Z = 384	Produces the mother codeword the circular buffer holds
5	Rate matching	38.212 §7.2.5	Circular buffer, bit selection from the RV start point, bit interleaving	This is where HARQ lives: the RV picks which bits go out
6	Code block concatenation	38.212 §7.2.6	Rate-matched blocks joined into one codeword	—
7	Scrambling	38.211 §7.3.1.1	Gold-sequence XOR, cinit from RNTI and scrambling ID	—
8	Modulation	38.211 §7.3.1.2	QPSK to 256QAM (1024QAM in FR1 DL)	MCS may change between retransmissions
9	Layer mapping	38.211 §7.3.1.3	Up to 4 layers per codeword, 8 in total	Single-layer is typical for NTN handhelds
10	Antenna port mapping	38.211 §7.3.1.4	Layers to DMRS antenna ports (precoding transparent to the UE)	—
11	Mapping to VRBs	38.211 §7.3.1.5	Fill REs, skipping DMRS, CSI-RS, PTRS and reserved REs	Extra DMRS against residual Doppler reduces data REs
12	VRB → PRB mapping	38.211 §7.3.1.6	Non-interleaved or interleaved (bundle size 2 or 4)	—
13	OFDM baseband signal generation	38.211 §5.3.1	IFFT and cyclic prefix insertion per numerology	—
14	Digital front end and DAC	Implementation (up-conversion in §5.4)	Windowing/filtering for the spectral mask, crest-factor reduction, digital up-conversion, DPD, DAC	NTN uplink: GNSS/ephemeris Doppler pre-compensation (NCO shift) and timing-advance adjustment are applied here

Receive side, ADC to ACK. ADC → digital down-conversion, decimation and AGC → (NTN) frequency and timing correction using ephemeris aiding → CP removal and FFT → DMRS channel estimation and PTRS phase tracking → equalisation / MIMO detection → soft demapping to LLRs → descrambling → de-rate-matching and HARQ soft combining with the stored buffer for that process → LDPC decoding → code-block and TB CRC checks → ACK/NACK.

13.4 The DVB-S2/S2X equivalent

DVB-S2 has a direct counterpart: Figure 1, “Functional block diagram of the DVB-S2 System”, in ETSI EN 302 307(-1), which draws the transmitter from input streams through to the RF signal. DVB-S2X (EN 302 307-2) reuses this chain and adds blocks to it. On the receiver side, the DVB-S2 implementation guidelines (DVB A171-1 / ETSI TR 102 376-1) include a matching receiver functional block diagram, and the ESA RC64 DVB-S2 SDR modem paper reproduces both transmitter and receiver chains.

Stage	Spec (EN 302 307-1)	Blocks	Notes
Mode adaptation	§5.1	Input interface, input stream synchronisation (optional), null-packet deletion (ACM with TS input), CRC-8 per user packet, merger/slicer for multiple streams, 80-bit BBHEADER insertion	Application-dependent; GSE input carries IP
Stream adaptation	§5.2	Padding to fill the BBFRAME to Kbch, BB scrambling	Frame size is fixed by the MODCOD, so padding (not rate matching) absorbs the mismatch
FEC encoding	§5.3	BCH outer code, LDPC inner code (64800 or 16200 bits), bit interleaving for 8PSK and higher orders	One fixed codeword per frame; no RVs, no retransmission
Bit mapping	§5.4	QPSK, 8PSK, 16/32APSK (S2X up to 256APSK, plus π/2-BPSK VL-SNR)	Ring ratios per code rate
PL framing	§5.5	Dummy PLFRAME insertion, PLHEADER (SOF + PLSCODE), optional pilot insertion, PL scrambling	The PLHEADER makes every frame self-describing
BB shaping and quadrature modulation	§5.6	Root-raised-cosine filter (α = 0.35/0.25/0.20; S2X adds 0.15/0.10/0.05), then to the DAC and RF	No IFFT; DPD per APSK ring at the gateway
S2X additions	EN 302 307-2	VL-SNR header, superframing (Annex E), beam hopping, channel bonding	Superframes wrap the PLFRAME stream

Receive side, ADC to stream. ADC → decimation and AGC → coarse frequency recovery → matched filtering and symbol timing recovery → SOF/PLHEADER detection and frame synchronisation → PL descrambling → pilot-aided fine frequency and phase recovery → optional equalisation → soft demapping to LLRs → deinterleaving → iterative LDPC decoding → BCH decoding → BB descrambling → BBHEADER parsing and mode adaptation removal → TS or GSE output.

13.5 The two chains side by side

Aspect	NR PDSCH	DVB-S2/S2X
Retransmission	HARQ with incremental redundancy (four RVs), soft combining	None; QEF target with one codeword per frame
Fitting data to resources	Rate matching from a circular buffer to any allocation	Fixed FECFRAME per MODCOD; padding fills the BBFRAME
Error detection	TB CRC + per-code-block CRC	BCH outer code, CRC-8 per user packet and on the BBHEADER
Scrambling	UE-specific (RNTI-based) Gold sequence	BB scrambler plus PL scrambling with selectable Gold codes
Format signalling	DCI on PDCCH, decoded before the data	PLHEADER on every frame (self-describing)
Waveform generation	IFFT + cyclic prefix	RRC pulse shaping of a single carrier
Receiver memory	Soft buffer per HARQ process held across the RTT (up to 32 processes in NTN)	Single-frame LDPC buffer; nothing held across frames

For receiver design this is the practical difference. An NR-NTN modem must decode control before data and keep HARQ state and soft buffers across hundreds of milliseconds. A DVB-S2X demodulator can lock blindly onto any frame and throw the soft data away as soon as the codeword is decoded.

Hardware and system design recommendations

1. ADC and dynamic range. Wideband S2X receivers (≥500 Mbaud, 256APSK) need about 7–8 ENOB at 1–2 GS/s; keep the jitter-limited SNR, −20·log10(2π·f_in·σ_j), at least 6–10 dB above the Es/N0 target. NR-NTN handsets need back-off headroom for OFDM crest factor (10–12 dB) and blockers from overlapping terrestrial bands, which pushes AGC range and filtering rather than sample rate.
2. PA linearity. Design NR handset PAs for DFT-s-OFDM/π/2-BPSK efficiency at 23 dBm and plan for higher power classes. Ka NR VSAT array SSPAs will run 5–8 dB back-off for CP-OFDM, so prefer DFT-s-OFDM on the uplink and consider array-level DPD. For S2X gateways, use per-ring APSK predistortion and linearised TWTAs, and -L MODCODs for multi-carrier HPAs.
3. Phase noise. For 256APSK, keep integrated phase error well below 1° rms post-loop, specify LO masks against Annex H.8, and run pilots on. For Ka NR at 120 kHz SCS with PTRS, reuse terrestrial FR2 synthesiser designs but control LO noise around 10–100 kHz offset.
4. Doppler compensation. NR-NTN terminals need GNSS (or a Rel-20 GNSS-resilient alternative), an ephemeris propagator, and a fine-resolution TX NCO and timing adjuster that holds ±0.1 ppm and follows up to ~0.27 ppm/s at 600 km. S2X receivers for LEO should add ephemeris-aided NCO pre-rotation, because narrow VL-SNR loops cannot follow LEO Doppler rates unaided.
5. Phased-array beam steering. LEO terminals need continuous electronic steering plus satellite handover within tens of ms; align NR array handover with CHO/RACH-less procedures and SIB19 neighbour ephemeris. Use true-time-delay or subarray TTD for 400 MHz Ka carriers to avoid beam squint at wide scan angles.
6. System choice. For greenfield GEO/HTS broadband or broadcast, stay with DVB-S2X (Annex E formats for beam hopping or precoding) plus DVB-RCS2. For D2D, IoT, or services that must appear as 5G access in an MNO core, build on NR-NTN or IoT-NTN, and track Rel-19 Ku-band, regenerative payloads and Rel-20 GNSS resilience before freezing silicon. A dual-mode modem (S2X forward demodulator plus NR-NTN baseband) is a credible architecture for multi-orbit VSATs.

Caveats

• Rel-19 ASN.1 and performance corrections continue; Rel-20 NTN items are still being specified (Stage-3 March 2027, ASN.1 freeze June 2027).
• RRC value ranges (cellSpecificKoffset, kmac, ta-Common and drift, ntn-UlSyncValidityDuration) were taken from secondary reproductions of TS 38.331, and sources disagree on the ta-CommonDrift range; check the spec version you target. The NTN timing-error table in TS 38.133 §7.1C could not be verified.
• PAPR values, overhead percentages, receiver acquisition ranges, ACM margins and phase-noise targets are typical engineering figures, not normative. HARQ process counts in section 13.2 are first-order estimates that ignore gNB/UE processing time beyond a few slots.
• AST SpaceMobile throughput figures are vendor design targets; Starlink D2C per-beam capacity is an external measurement estimate.

Sources

• 3GPP — Non-Terrestrial Networks overview
• 3GPP — Rel-19 summary (2026)
• 3GPP TR 38.821 — Solutions for NR to support NTN
• 3GPP TR 38.811 — Study on NR to support NTN
• ETSI TS 138 101-5 — NR NTN UE radio requirements
• ETSI TS 138 321 — NR MAC protocol
• ShareTechnote — 5G/NR PDSCH transport process (diagram)
• ShareTechnote — 5G/NR HARQ-ACK codebook
• 5G New Radio: Unveiling the Essentials of the Next Generation Wireless Access Technology (arXiv)
• ETSI EN 302 307 — DVB-S2 (Figure 1: functional block diagram)
• DVB A172 — DVB-S2X highlights white paper
• DVB A171-1 — DVB-S2 implementation guidelines
• ETSI TR 102 376-2 — DVB-S2X implementation guidelines
• ESA — DVB-S2 Software Defined Radio Modem on the RC64 Manycore DSP
• DVB — Beam hopping in DVB-S2X webinar
• ETSI EN 301 545-2 — DVB-RCS2 lower layers
• DVB A116-1 — Generic Stream Encapsulation protocol
• DVB — How IP-based broadcast meets 5G
• Ericsson Technology Review — 3GPP satellite communication
• 5G New Radio in Nonlinear Satellite Downlink: A PHY Comparison with DVB-S2X
• 5G NR Non-Terrestrial Networks: From Early Results to the Road Ahead (arXiv)
• Random Access in DVB-RCS2: Design and Dynamic Control (arXiv)
• ShareTechnote — NTN timing advance
• AST SpaceMobile — FAQ
• Starlink Direct-to-Cell measurement study, arXiv:2506.00283

Ben Nevis. The highest mountain in the British Isles. AllTrails says it’s a hard one. It reminds me of the scene in the show “Chernobyl” when they discovered that the maximum rating on Geiger counters of Diatlov and others who were onsite is 3.6 roentgens per hour but the actual reading was likely to be much much higher. The “Hard” rating for “Ben Nevis” in AllTrails is exactly that. It is more than hard, it is extremely hard. And Scottish weather does not help.

After you have managed to find parking (which was tricky), you can head for the climb.

The first part of the climb is steps. So many steps. The steps were extremely gruelling. 

After climbing for good part of two hours, you’d finally see the signs of the loch.

The hike until then was gruelling but the sight was worth it. And then you keep climbing. The steps disappear for a moment giving the much needed relief.

And then some more really steep climbing. By steep climbing I mean the kind where you want to give up and turn around. I should have done that.

And then you hit the first “checkpoint” on AllTrails: a kind of waterfall.

And then you keep climbing. But soon, it got cold. At this point, I realized everything is wet. Waterproof clothes weren’t as waterproof as I thought they were.

It becomes tough at this point. There is still almost half the climb left. Steps give way to stone paths. It’s not a scramble but it’s tiring.

As soon as we got up beyond the ice point, it started pouring down. Rain is ice at that point. 

My wife and I decided to turn around. The others wanted to finish the climb so they continued on.

On the way down, near the loch, my legs seized up. And it was painful enough that I just wanted to cry. I somehow made the climb down aided by my wife. It was tough.

But this video, even though it barely captures the awesomeness, is something that will make us want to do it again.

Milton Keynes is derided by many as city of roundabouts, a curious one, concrete cows’ grazing field etc. But the city offers a lot more than its roundabouts. It has some nice parks all around. And in many of the parks, many of which offer free parking (something not to be scoffed at!), one can find ancient ruins.

One such one can be found in Stantonbury. It’s the ruins of St. Peter’s Church. The church dates back to the 1100s and has a rather comical history.

People for a long time were getting married in the church but then, it was discovered that the church was not authorised for marriage ceremonies. What it meant was that all marriages held there were null and void!

It took an Act of Parliament to legalise all the marriages held there.

You can find more details here, including snippets of newspaper articles even in the US.

The world is way too random to plan anything long term. When insurance agents send me mails, exhorting me to think about long term plans, all I can do is smirk (and then delete the mails). If anything the year gone by has taught me, is that life is a chaotic process. I am well read on the topic of chaos, but to take a step back and see how it has played havoc with all of our lives, is enlightening at best and depressing at worst.

Jan 2020: Reports of a new virus making people ill start maing its way into western media

early Feb 2020: The virus has started making its way into other countries. Remember how media reported on the first few cases in every country? I can recollect the discussion around an infected woman who travelled to Dublin and then took a train to Belfast (or vice-versa). I remember the discussion around the son of a bureacrat who attended a party in London, got infected, travelled to Kolkata but failed to declare it to the West Bengal health authorities. Both the mother and son were villfied to no end in the media.

Late Feb 2020: We were asked to work from home and Ireland declared a lockdown. Remember the pitch fork battle fought over toilet paper in the aisles of Aldi?

March 2020: Every discussion was around Coronavirus. HR trying to uplift the spirit of all employees stuck at home through different virtual events. Piece of advice: Those events are fun when you do it among team members and not company wide. I don’t know who Elisa from Accounting is and I can’t be arsed to team up with her in a quiz with Amazon vouchers at stake.

April 2020: Reddit was filled with rants about how people were not following social distancing norms and how close to reaching the peak we were. If I recollect correctly, Ireland did not reach the peak until May. But more importantly, the radar project I was working, the project for which I moved countries, was cancelled and we were left in a limbo.

May 2020: More work from home, but now fatigue has started to creep in. I got allocated to a project in which I had no interest.

June 2020: Signs of unlocking

July 2020: Unlocking of Ireland started in phases. Finally I could get a haircut.

August 2020: Work from home continues.

September 2020: I needed a new job and started looking for one.

October 2020: Was busy with an internal conference at Analog Devices. Took my mind off the distressing state of affairs.

November 2020: Cases rising –> lets lock up people in their homes. Fuck civil liberties. We, the elite Government, completely mistrust the people and we have this inherent need to protect people from themselves.

December 2020: Accepted the job offer in England. Started going out with Ciara, probably the best thing to have happened to me in sometime.

Jan 2021: Started packing to leave Ireland. Meanwhile cases exploded exponentially.

Feb 2021: Left Ireland and came to England.

March 2021: Same work from home but in a different country.

April 2021: Unlocking of the new country, but what could I do with the new found freedom, besides getting a haircut? I am a loner deep down and changing countries frequently does not help.

May 2021: Got my first dose of vaccine. Ciara comes over.

June 2021: Back to being alone. Got my second dose of vaccine yesterday.

Could I have predicted any of it, or any of the insurance agents predicted it? I doubt.

But what has kept my sanity all these while? Amazon (not Amazon Video). I have bought so much of stuff over the last few months and it felt like the boxes from Amazon were the only thing I could really look forward to.

“Oh but your job is so interesting!”

“Boohoo. I have been working long enough to know it does not matter really.” I mean, sure, I love my job and cannot fathom doing anything else. But to be fair, my biggest motivation to keep getting better at my job is the moolah the experienced folks in my industry make. And the job security that comes with it. As easy it is to replace an experienced software engineer with a younger grad, it is hard to do that for an experienced circuit design engineer. Do you know why? Because industry does not share its knowledge with the academia (not that the academia is very interested either) and you cannot fire up an IDE to learn stuff on your own.

Its physically hard for me to type this out, but I am now a card bearing member of the great consumerism culture. Capitalism claims yet another victim.

Having money means I can overcome most of the problems life throws at me. But it also means I am forever beholden to a 9-5 job (Well its more like 8-6 for me with a half an hour lunchbreak). Sure I can risk starting my own business, and in the remotest possibility that I am successful, I can cash out and live the rest of my life out of that money. But then if you know me personally, I cannot live without a hustle, I thrive in high stress environments.

All that for Amazon delivery boxes to keep you company in your loneliest times.

“What about family? Family gives purpose to one’s life?”

Discussion (read: rant) for another day 🙂

People often envy the life I have lead; they have been fascinated by my story starting from my time in Bangalore to Belgium to Ireland and now to England. I like to think I am well liked, and as I have often mentioned countless times, things may not have always gone my way but I always have had the best people around me to help me out.

But the toll of such a life is tremendous and it is often lost on people who haven’t lead this life. And when the realisation dawns on me, it hits like a massive wave, and brings me to a borderline panic attack. Just to give you an insight, if I were to die right now, I don’t know if the news will reach my parents within 24 hours. If Jack, my housemate, is away on vacation, I doubt if someone will find me in a week. There is right now a restriction on passengers from India, so my parents cannot come. Even if the ban was not in place, they don’t have a visa. And the similar situation holds for my sister. The only hope for the repatriation of my dead body is probably Ciara.

Why such macabre thoughts, you may ask? I dunno; maybe it has its roots in the death of a few people close to my family in the ongoing COVID crisis in India. Recently I picked up a book on the IRA written by Kevin Toolis. The book was first published in 1995 and it is amazing how many top IRA members he managed to interview. The rebels were always aware that they could die the very next time they are on the streets, but they did not let that deter them. I am no revolutionary, but I think being surrounded by people who believe the same helped them get over the fear. I doubt how many of them would like to be lonely in their final moments.

Death can always be a moment’s notice away and once you are dead, do you really care what happens? Maybe not. But I don’t want to be alone in my final moments. Of course, I can be hit by a car and die on the road. Should I be just scared and not leave home?

The answer is no, you keep going. You sleep alone in your bed, staring into the ceiling. You ask Google to play soothing sounds but they don’t really fill the emptiness in your room, does it? It is particularly hard for people like me who are very picky of who we let into our lives. I live in a time zone that is (almost) midway between US and India. It’s early morning there and my friends are catching up on their last bit of REM sleep. It’s late evening in the states and my family is just returning from work or just about to prepare their dinners. Where do I fit in?

The COVID crisis has definitely not helped. Every major news outlet just pays lip service to the impact the lockdowns and restrictions have had on the mental health of the general population. But the effects of that are not immediate, it will take years for it surface. Somebody dying, well, it’s more immediate and does not bode well for a government seeking re-election. But then people refuse to take precautions on their own! It does not hurt to wear a mask, or to maintain safe distance. They need the government to impose strict lockdowns. I appreciate the model followed by Sweden, as controversial as that may sound. People have been empowered to make their own choices.

It’s not being easy away from family, acclimating to a new culture, to a new place. Every time I want to buy something huge, I would be like, “How long will I be in this place for? If I had to leave tomorrow, can I even afford to move all of this stuff back to India? Maybe it’s a problem unique to me who has changed three countries in as many years.

But then, as the night draws on, you decide that you have rambled enough. You try to get sleep in the few hours left before you need to start the drudgery to survive the capitalistic world. Nobody needs to know the story behind that smiling face.

This is my take on the entire CAA/NRC protests ongoing in India and what it means to a non-resident Indian in Ireland.

Its funny how people fail to realize that countries are imaginary institutions with borders which are blurred at best. The entire concept (and by that I refer to its boundaries) of today’s India is very different from the British Indian Empire. But lets focus on the current definition of India. What does it mean?

I have been called an anti-national by many Indians. But for me the definition of Indians is the quite simple: follow the spirit of the Indian constitution. But isn’t that arbitrary as well? Probably, but being in a pluralistic country, speaking a particular language and following certain cultural practices can hardly be the definition of being Indian. And one of the spirits of the constitution is secularism. The preamble to the Indian constitution says just as much:

WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC and to secure to all its citizens
JUSTICE, social, economic and political;
LIBERTY of thought, expression, belief, faith and worship;
EQUALITY of status and of opportunity; and to promote among them all
FRATERNITY assuring the dignity of the individual and the unity and integrity of the Nation;
IN OUR CONSTITUENT ASSEMBLY this 26th day of November 1949, do HEREBY ADOPT, ENACT AND GIVE TO OURSELVES THIS CONSTITUTION.

And secularism is a very important principle. It is what differentiates us from Pakistan which was formed on religious lines. We don’t discriminate on the basis of religion.

Sometimes people have asked me, “If your constitution is secular, why are some religions given the minority status?” It again comes back to the concept of “Justice”. We thrive on pluralism. If a particular way of life is threatened, and it does not impact the Liberty, Equality and Fraternity principles, we will try to protect it. In the 2006 Sachar committee, it was mentioned that the Muslims are worse off in socio-economic conditions than the Dalits. Of course, some people would then say, “Well its their fault that they have so many kids and that they don’t focus on education.” Just like it is the fault of the black people that they are still marginalized in the US and have a far lower socio-economic status than the other races.

What irks me the most about the Citizenship Amendment Bill of 2019 is that it violates the secularism principle of the Indian constitution. Secularism is a strong word which has formed the basis of this country. And the bill is an indirect attack on the Muslims in India. I strongly protest against this.

“But it does not impact the Muslims in India”. But it does. This is testing of waters by the BJP government to see how far they can get away with by attacking the Muslim community in India.

“But this bill is trying to protect the minorities in the neighboring countries!” First of all it is not. The amendment to the Citizenship Act will help approximately 30k people who entered India before December 2014 (as per the Intelligence Bureau). Second of all, if we are so concerned with protecting the rights of minorities in neighboring countries, why have the Act excluded the Rohingyas of Myanmar and Ahmedis of Pakistan.

“But you see the protests have become so violent.” Unfortunately, not every Indian is Gandhi. The Government rolled the dice first and a backlash was expected. If the Government did not see this coming, it was a big failure on part of the Government. Or maybe they did see this coming and wanted an excuse to paint all Muslims as evil. Amit Shah and Narendra Modi can be many things, but I don’t think they are so incompetent to not foresee the backlash from the Muslim community.

And then there is downright Islamophobia. Some friends have told me, “How can you not see the cancer of Islam spreading across Europe having studied in Belgium itself?”. Refugees fleeing war (which, by the way, could have been prevented had the liberals not stopped some of the Western European countries from intervening in the crisis in Syria and Yemen when it was in its nascent stages) does not really strike me as “cancer”. I have worked with people from many countries and nobody was as full of shit as people who make comments like these.

We need a new India or atleast an organization willing to work to build a new India. Without a new India, polarizing political parties will keep coming to power either at the state level or at federal level. And each time, they will wreak havoc. The new organization needs to focus on three things:

• Social change based on data and statistics: This is taking a leaf out of Bill Gates’ work on eradication of polio. Data can give insights on how a particular section of the population is doing. We need to reach out to those communities that are marginalized and need to yank them forward. I am always scared that data can be manipulated to fit any narrative but we need to be honest about it.
• Education: Modern education. Starting from bureaucrats to bank clerks to farmers, they need to be introduced to the latest in technology. This can be done through a PPP model. Focus on environment needs to be a key aspect as well.
• Health infrastructure and health education: A healthy population equals huge savings in healthcare costs in the future. People in all sections of the society needs to be sensitized to the impact of food that they are eating on their health.

So after a long break from studies and a lot of immigration woes later, I reached Limerick. Well, my immigration woes are still not over as they made a mistake with my GNIB card and I waiting for a new one.

One of the first things that hit me when I reached Ireland was how empty it seemed. Granted I did not fly into Dublin and my hotel was outside the city (in Raheen). But I think its way less densely populated than Leuven was.

The next culture shock was shops and supermarkets open on Sundays!! And the fact that supermarkets don’t close before 10pm on weekdays! I was absolutely delighted.

But this is not a travel blog. I don’t like travelling and hate it when people say their horizons are broadened when they travel. Fuck no. Its expensive (I am still middle class). And you see only the parts which the tourism department of the country wants you to see.

Every now and then I see a differently abled kid who gets into the bus from a stop on the O’Connell avenue. He seems like a good kid. I often feel for the parents of kids who are differently-abled. Its hard enough to manage a career with a normal kid and it is so much harder with a kid who has special needs. The constant worrying they have to go through every time their kids leave the home. A big shout out to them. The TV series called ‘Atypical’ captures brilliantly the struggle of a kid with autism and everyone around them as they go on about their daily life.

My return times vary quite a bit and unfortunately I have not captured a regularity in it. Also, I am typically on the phone with my parents or my girlfriend on my way back.

The frost covered mornings are often a beautiful sight. The weather varies quite a bit here. One day it can be freezing, the next day it can be rainy and 10 degrees Celsius. I always get down at a stop called Avonmore Road and walk to my office from there. The bus takes a diversion of 3kms just before my office. I find its better to just get down at Avonmore road and walk the rest of the path to my office.

And everyday, the same set of technicians who work nearby get down with me. And we have started to recognize each other and the usual nod or “How are you doing?” greeting.
(The Irish use “How are you doing” as a greeting. They don’t really expect an answer. Imagine that in Belgium! It will be paramount to a scandal to ask someone you don’t know in Belgium how they are doing.)

So Mr. Ramgopal Rao put up a long post in Facebook mentioning his reasons for supporting it. It can be found at: https://www.facebook.com/rao.ramgopal/posts/10218188716681820?hc_location=ufi
Lets go through it one by one.

1. Many top universities in the world have strong Bachelors programmes and strong Ph.D. programmes. The universities which are running large masters programmes abroad are looking at these as revenue earners and charge a huge fee. The streams have also been modified and made contemporary like Cyber security, AI etc. In all top universities abroad, while doing Ph.D., many students get a masters degree along the way. This is how masters programmes have changed all over the world in the last decade.

Yes they do. Some universities in California do it. TU Delft and UTwente in Netherlands do it. But it does not mean its a nice thing. However there is a difference. Netherlands does not charge the high tuition fees from its own citizens or citizens of other countries in EEA (it makes sense as well; the people of those countries pay tax into their own system and its fair that they get a share of it). As for American universities, most do not treat its students as cash cows.

2. Students who come to the M.Tech programmes in IITs are not coming to become academicians. Those who wish to become one, can directly register for a Ph.D. All IITs allow a direct admission into Ph.D (with a high stipend and almost zero tuition fee) without M.Tech as a requirement, including the PMRF. Eventually, Ph.D. students registered in IITs will be able to receive a masters degree once they complete certain credits. Even if it is not so today in some institutes, I am sure, it will indeed become a norm eventually to make the Ph.D. admissions attractive.

Being interested in a PhD does not work like that. I was interested in PhD before I went for MS and then I realized that I am not. I liked working in groups but in PhD, you are expected to do things solely on your own. Also PhDs does not always mean a career in academics. A lot of highly qualified PhDs are required in the industry as well. Look up two new startups in Belgium: Pharrowtech and TuskIC. Both of them are founded by people with PhD degrees.
The way it works is you start doing your Masters, and then during your thesis, you will know if you want to continue in research or go to the industry. By increasing the tuition fees and forcing students who cannot afford to go the PhD way, PhD programs will see more drop out.

3. Students who join the M. Tech programmes in IITs are joining these programmes to find a job, which is fine. IITs therefore need to align their M.Tech programmes to the market requirements. Because of government freely giving fellowships, many institutions are running outdated masters programmes in streams which are not even seen as current by the Industry. In the current scenario, there is no strong motivation for any one to change. Many students take admission into the M.Tech programmes and over 50% of them quit as soon as they find a job. Among the remaining, many prepare for other competitive examinations and have no interest in what they are pursuing. Country’s precious Resources (IIT seats and government funds) are wasted in such a scenario with no benefit to any one. Today, we have uninterested students studying in outdated programmes which are completely disconnected with the market demands. Over 50% dropouts in masters programmes today in IITs only means that, students value the jobs they get after their B.Tech more than the career they can build with their M.Techs. How can we spend tax payers money to offer free education to them, when they themselves see no value in such an education? This is an alarming situation we have gotten ourselves into and obviously, a bit of a reset was needed. I am happy that Ministry and Council took such a bold decision.

If outdated coursework is the problem, then how does increasing fees help? If students don’t understand the value of doing a Masters program, its a different problem altogether. It means that the country does not give a higher preference to people with a Masters degree. And that is symbolic of a lack of highly technical R&D jobs that require an advanced technical degree.

4. If students are willing to pay 20 lakhs for an MBA degree in an IIM, they can surely pay 4 lakhs for a masters degree in IITs. Nobody drops out of IIMs since they see a value in IIM-MBA programmes. On the other hand, we see over 50% dropouts in IIT- M.Tech programmes. After the Council decision, since IITs now need to attract high fee paying students, I am sure, institutions will also align themselves to market requirements and will have a serious relook at the masters streams they are offering. This will bring in accountability at all levels. In the long run, the masters programmes will become contemporary and will train students for the jobs which exist in the Industry.

Business courses are so expensive because they require not just highly educated faculty members but also people who have a good clout in the industry. And to draw the latter talent, you need to pay them high salaries. Are they willing to pay the professors in IITs those high salaries?

And what is this constant talk about market requirements? The main focus of a Masters program is to teach students the basics and how to use them in a real life use-cases and some exposure to industry grade tools. The latter part keeps changing.

Masters program are not meant to teach students how to use the Eclipse IDE but how to take advantage of multi-threading.

5. IITs will focus on B.Tech programmes and Ph.D. programmes like what all research intensive universities worldwide do. Masters programmes in IITs will train students for jobs and those who are interested in academics, will switch over to a Ph.D. The top GATE scorers will still be offered admissions into M.Tech programmes directly as Teaching Assistants and will be offered fee waivers and stipend. However, the fee waivers and stipend will be linked to their role as Teaching Assistants. Others will get into these programmes paying a fee by taking loans, if needed. Since the programmes will get aligned with market requirements, they will be guaranteed a job and can repay loans.

Good researcher ! = Good teaching assistant.
And I studied in KU Leuven. It has been consistently ranked in the top 50 universities. It has been ranked most innovative university in Europe for three years in a row. Its also 600 years old.
And the attitude there is never that Masters program is for jobs. I am pretty sure its not the case anywhere else in the world.

6. The Council resolution also says that all needy students will be given fee concessions and scholarships similar to the B.Tech students. No eligible student in the B.Tech programmes has ever been denied admission in IITs because of her/his poor financial background. There is no reason to believe that this will be any different for top GATE scorers seeking admission into the M.Tech programmes. This is our moral and social responsibility

No, it just makes life difficult for students. It also puts them at the mercy of the administration. Education should be a right and not a charity.

7. The freebies that we have been doling out with tax payers money, to students who are uninterested and into systems which have become unaccountable, needed to stop at some point. Let’s not look at this from an individual’s perspective but rather see it in the larger nation building perspective. IITs are now taking loans from HEFA for their infrastructure. IIT Delhi needs to repay some thing like Rs. 580 Crores to Canara Bank over the next 10 years. Same is the case with IIT Bombay and others. There is a great need to increase our internal revenues.

Which means that these universities are not able to draw funded projects from the industry, which means that the ecosystem of doing state of the art does not exist in India or the quality is not good enough to command the top dollars that foreign varsities charge, which means that the faculty is not good enough. But of course, lets put the burden on the students.

8. IITs need to produce a large number of high quality Ph.Ds who can go out and build top class institutions, get into entrepreneurship and build research culture in our industries. We need to attract top GATE scores into our Ph.D. programmes through full fellowships and scholarships. The limited funds we have need to be diverted into these Ph.D. programmes. M.Tech programmes for a large number of GATE qualifiers need to be self funded (with a guaranteed job at the end of the programme) or sponsored programmes by industries. IIT Delhi has been successfully running for some time one such M. Tech sponsored programme in VLSI. This VDTT programme is entirely funded by semiconductor industries. This M.Tech programme still attracts top GATE scores but with the fellowship paid by the industries.

Yes we need more of such programs but it does not mean that we make life difficult for all Masters students.

9. Industries need to take ownership of M.Tech programmes in IITs and not leave it to the government. It is in their direct interest. M.Techs have indeed played a significant role in building the nation by serving our public sector units and private industries such as TI, Samsung, IBM, Intel, GE, Micron and many many others. Time they start investing their funds in building these M.Tech programmes in IITs and also work with these institutions closely to make the M.Tech programmes relevant. The modified CSR rules also allow this now. We are more than eager to work with them. We can then use our limited resources for doing other things.

Educating people is in the interest of the country. A highly educated population means crime rates are lower, people tend to take better care of themselves etc.

And the reason these companies don’t invest in India is because they don’t yet see the value. Companies always do things that suits them. If investing in India means they will get the best, they would do it. If not, then they won’t.

I came across a nice article where they talked about using thermal cameras for detecting water leaks. It instantly reminded me of the project I did as part of a course called Multimedia Technology and Coding. I was given to write an paper on thermal camera and how to use it to detect faults in thermal insulation. There was another part as well where we had to decide on what standards to choose to store the images.

Anyway, this article published in Electronics for you talks about using thermal cameras to detect faults in a swimming pool plumbing system. Typically, they would have needed to dig the entire pavement around to find which pipe was leaking. But instead they used a thermal camera find faults in the water plumbing. The sun heated up the pavements but water having a higher specific heat capacity caused some parts of it to remain slightly cooler. Using the contrast they could find the faults.

Nice use of thermal cameras.

So I came across this article in Times of India today. https://m.timesofindia.com/business/india-business/edu-loans-in-india-shrink-25-in-4-yrs/articleshow/69490291.cms

The article is basically a summary of the non-performing assets in the education loan sector of India.

As per the article, the highest portion of NPA is in the sub-4 lakh loan. These are the loans that can be given without any collateral. There can be two reasons why the default rate is the highest in this sector

1. Because there is no collateral it can mean that the punishment for not repaying is not there and students don’t take it seriously enough.
2. There are not enough jobs.

I think the last one is more likely. I have both ancedotal evidence and some statistics.

The ancedotal evidence comes from my friends who are trying to set up factories in India. Whenever they start the construction, they get a lot of requests from local people for jobs (one of the condition for being allowed to set up a factory is that they employ the local people). But it’s not always possible. They then demand that they get all their raw materials from the local “syndicate” which is just another name for a shop supplying raw materials for construction. These are typically run by local youths who are not employed.

And the statistics comes from the rumors of a report that unemployment is at a 45 year high. Of course, the government never let the report come out to the public (but will they publish the report now?).

The students who take the small loans are typically for courses like B.Ed, nursing or the many courses in technical training institutes. There is a lot of automation happening at the factory level.. Some people can argue that AI is going to take over these jobs, but honestly that wave still hasn’t come and the data is from the last 4 years.

The default rate in the higher loan amount sector is much lower. These are the ones for things like MBA and engineering courses in one of the better institutes. MBA and engineering graduates can still find jobs although the quality of the jobs and the life satisfaction from it is dropping fast.

Not everyone gets into Google or Amazon or Goldman Sachs or Morgan Stanley OR Oracle or Samsung.. There is a sea of smaller IT companies which are trying to compete with the big fishes. The big fishes are going to become bigger because they have the capital resources to invest into things like AI, which helps them grow much more rapidly than the smaller companies. It’s a deadly positive feedback.

In short, the data presented by this article paints a bleak picture of the condition of the youth of our country. And it’s the beginning of a long list of problems that the new government will have to address. Else, our country will be submerged into chaos.