Najath Akram
Signal Processing Engineer / Houston, Texas
I build the part of a radio you never see.
These days that means multiband O-RAN radio units, some early 6G, and AI agents that have to prove their work like everyone else.
The physical layer: where information becomes electromagnetic waves and, with a bit of luck, becomes information again on the other end.
Who is writing
Hello. I'm Najath. Ten years in radio, the last six shipping O-RAN radio units. A PhD at Florida International University first, then four years that took me from senior engineer to lead to principal, and I have stayed close to the same seam since.
The work lives somewhere between math and hardware. Most of my days are spent in MATLAB, in front of a spectrum analyzer, or in a document describing why a particular combination of frequencies decided to interfere with itself.
A fair amount of what I build now has AI agents in the loop, which changed how much I write and not one thing about what I trust. The verification came first and the agents arrived later: independent decoders that re-read every exported byte off disk, and mutation tests that plant faults to prove the checks can actually see them.
What I work on
Signal processing
Digital beamforming, phased arrays, and the quiet art of doing more with fewer ADCs. A good portion of my PhD went into trading converters for mathematics: one ADC per four antennas at 28 GHz, and half the count again for 2D arrays, using multidimensional signal processing and approximate FFTs.
O-RAN radio units
Digital front ends, crest factor reduction, EVM, PIM, and the fronthaul that carries it all: split 7.2x, eAxC, the WG4 CUS-plane. I spend most of my days here. If something about a waveform looks wrong on a spectrum analyzer, it usually becomes my afternoon.
Recent work
- Modeling
The bit-accurate models firmware is verified against
Bit-accurate models of the downlink, uplink, low-PHY, and PRACH chains of multiband O-RAN radio units, and the source of the RTL golden vectors firmware is signed off against. NR and LTE test models run through IFFT and FFT, CFR, the same channel-filter and mixer IP C-models the FPGA uses, and O-RAN BFP compression at 8, 9, 10, 12, and 14 bits, so firmware verification can compare RTL output stage by stage and treat any difference as a defect rather than a question of tolerance. Every intermediate stage is exported, so when a test team hits something unexpected on the bench the problem can be narrowed to the stage that first disagrees. The models also carry the architectural work, evaluating filter and gain structures before a configuration is committed to hardware. Carriers from 3 to 100 MHz, FDD and TDD, including combined-band carriers such as B28 with B20, packaged as versioned executables so running them needs no MATLAB license.
- Verification
A PRACH receive chain covering every configuration
PRACH is the first thing a radio hears from a phone, and it is the most configuration-dependent chain in the receiver. The model runs the whole receive chain bit-accurately, from the PRACH DDC and decimation through cyclic prefix removal, FFT, subcarrier extraction, BFP and U-plane packing, and detection, and covers LTE formats 0 to 3 and full NR FR1, long and short preambles, and all 256 configuration indices in both FDD and TDD. What makes it harder than the rest of the receive path is that very little is fixed. Preamble format, subcarrier spacing, and the occasion pattern together decide where in time and frequency a preamble is even allowed to appear, so the search window has to be derived per configuration rather than written down once. Timing has to be right to the sample, cyclic prefix and guard handling change with format, and the root sequence and cyclic shift have to be recovered without being told which ones were sent. Getting a single configuration right proves very little, which is why the model is exercised across the whole index space instead of a representative few.
- Tooling
Predicting where intermodulation will land
Passive intermodulation is far cheaper to design around than to find later. Once a radio is built, a product falling in its own uplink band presents as a sensitivity problem that looks like several other faults, and tracing it back to the mixing that caused it is slow work. This enumerates third, fifth, and seventh order products across a 46-band catalog and flags any that land in an uplink band, for the mixing topologies of single, dual, and tri-band radios. It uses corner-evaluation interval arithmetic, so the reported hit ranges are exact across the band edges rather than sampled at a few frequencies and assumed representative. The use is band-combination planning: combinations can be ruled in or out before anyone commits to a filter plan. Products are ranked in dBc, and the power figures are relative rather than calibrated, which the tool states plainly. The catalog was checked by hand against a B71, B29, and B14 stack before anyone trusted it.
- Tooling
Uplink EVM without an instrument license
The radio unit does not do channel estimation or equalization, so measuring uplink quality means demodulating the fronthaul capture somewhere else. That is normally a Keysight 89600 vector signal analyzer, and the licenses cost enough that there are only ever a few seats to share. Most of the people waiting for one need to open a PCAP, find the uplink data going from the O-RU to the O-DU, demodulate it, and read an EVM. This does that as a standalone executable with no license attached: PUSCH and PRACH demodulated straight from 7.2x U-plane captures, uncompressed or block-floating-point compressed, with result views aligned to the VSA so the two can be read side by side. It also settles a recurring interop argument. An RU to DU full-scale alignment check emulates the DU's fixed-point ingest (shift, container width, wrap or saturate) against the per-PRB BFP exponents in the capture and returns a pass or fail that separates a radio misconfiguration from a DU ingest error. The instrument seats stay free for the work that needs them.
Papers
IEEE Access, vol. 9
IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 68
IEEE Access, vol. 8
If you have a question about anything here, O-RAN fronthaul, PRACH, or one of the photographs, email reaches me directly. I read everything.
Most of the work here sits between signal processing and the radios that have to carry it.