arXiv subjects

Rohith Reddy Vennam

Publications and source records attributed to Rohith Reddy Vennam.

4 recordsLinked to original sources

arXiv2026

FSMA: Gateway-Controlled Access for Scalable LoRa Non-Terrestrial Networks

LoRa-based non-terrestrial networks are rapidly becoming infrastructure for global IoT, with LEO satellites delivering direct-to-device connectivity and drone-mounted gateways serving precision agriculture, emergency response, and environmental monitoring. Both settings share a fundamental MAC-layer bottleneck: large coverage footprints cause thousands of devices to collide on the same channel, while gateway mobility induces rapid link variations, making link-unaware transmissions a persistent source of wasted airtime. These challenges demand random-access solutions, yet ALOHA provides no collision coordination, CSMA sensing fails beyond ~15 km, and BSMA's continuous busy tone consumes 80-90% of the channel capacity. We propose Free Signal Multiple Access (FSMA), a synchronization-free, gateway-controlled MAC protocol. Like a traffic signal, FSMA uses a single LoRa upchirp (FreeChirp) to indicate channel availability. By transmitting it at a lower spreading factor than the node uplink, FSMA implicitly filters weak-link nodes through channel reciprocity, reducing the collision window by 6-200x without synchronization, handshakes, or hardware modifications. Hardware experiments with 25 COTS LoRa nodes and a drone-mounted gateway demonstrate 2x higher throughput, 2.5-5x better packet reception ratio, and up to 5x improved energy efficiency. Large-scale simulations with real TLE-based satellite trajectories confirm scalability to 5000+ devices per satellite pass.

cs.NI↗

arXiv2026

FlexLink: Decoupling Control and Data Beams for Next-Generation Wideband Networks

The next generation of 6G networks aims to utilize ultra-wideband spectrum and massive antenna arrays to serve multiple users with both control and data channels at low latency and high efficiency. However, phased arrays at mmWave and mid-bands are fundamentally constrained to a single beam or suffer sharp beamforming loss when split across directions, limiting simultaneous control-data support. In FlexLink, we introduce and prototype a novel delay-phased array architecture that overcomes this limitation by redistributing energy jointly across frequency and space, enabling multiple narrow beams without sacrificing per-beam gain or requiring additional power. We design and prototype FlexLink on a custom 4-7 GHz hardware testbed, demonstrating for the first time that control and data beams can be decoupled in practice, achieving nearly double spectral efficiency compared to conventional phased arrays.

eess.SP↗

arXiv2025

Satellites are closer than you think: A near field MIMO approach for Ground stations

The rapid growth of low Earth orbit (LEO) satellite constellations has revolutionized broadband access, earth observation, and direct-to-device connectivity. However, the expansion of ground station infrastructure has not kept pace, creating a critical bottleneck in satellite-to-ground backhaul capacity. Traditional parabolic dish antennas, though effective for geostationary (GEO) satellites, are ill-suited for dense, fastmoving LEO networks due to mechanical steering delays and their inability to track multiple satellites simultaneously. Phased array antennas offer electronically steerable beams and multisatellite support, but their integration into ground stations is limited by the high cost, hardware issues, and complexity of achieving sufficient antenna gain. We introduce ArrayLink, a distributed phased array architecture that coherently combines multiple small commercially available panels to achieve high-gain beamforming and unlock line-of-sight MIMO spatial multiplexing with minimal additional capital expenditure. By spacing 16 (32x32) panels across a kilometer-scale aperture, ArrayLink enters the radiative near-field, focusing energy in both angle and range while supporting up to four simultaneous spatial streams on a single feeder link. Through rigorous theoretical analysis, detailed 2D beam pattern simulations and real-world hardware experiments, we show that ArrayLink (i) achieves dish-class gain with in range 1-2 dB of 1.47 m reflector, (ii) maintains four parallel streams at ranges of hundreds of kilometers (falling to two beyond 2000 km), and (iii) exhibits tight agreement across theory, simulation, and experiment with minimal variance. These findings open a practical and scalable path to boosting LEO backhaul capacity.

eess.SP↗

arXiv2023

mmFlexible: Flexible Directional Frequency Multiplexing for Multi-user mmWave Networks

Modern mmWave systems have limited scalability due to inflexibility in performing frequency multiplexing. All the frequency components in the signal are beamformed to one direction via pencil beams and cannot be streamed to other user directions. We present a new flexible mmWave system called mmFlexible that enables flexible directional frequency multiplexing, where different frequency components of the mmWave signal are beamformed in multiple arbitrary directions with the same pencil beam. Our system makes two key contributions: (1) We propose a novel mmWave front-end architecture called a delay-phased array that uses a variable delay and variable phase element to create the desired frequency-direction response. (2) We propose a novel algorithm called FSDA (Frequency-space to delay-antenna) to estimate delay and phase values for the real-time operation of the delay-phased array. Through evaluations with mmWave channel traces, we show that mmFlexible provides a 60-150% reduction in worst-case latency compared to baselines

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