This paper discusses some of the solutions to the issue of data congestion in Nano-satellite missions. The complexity of Nano-satellite missions has increased over the years, generating more data than ever and this paradigm shift has in-turn resulted in the need for larger downlink bandwidth requirements. The larger bandwidth's necessity and limited availability of frequency spectrum in lower frequencies spectrum has resulted in the problem of data congestion and invoked the need to investigate the use of mmWave frequency bands for Nano-satellite missions. In this paper, three use cases are discussed to demonstrate the need for using frequency bands higher than X-band and the communication strategy discussed in the use-cases are not restricted to the specific application mentioned in the use-cases but can be extended to similar applications. Irrespective of the frequency bands, there is a need to adapt standards such as DVB.S2 and DVB.S2X (Satellite digital broadcasting standard) that provide spectral efficient modulation schemes. Although these well-established standards are already used in satellite communications, this work proposes further optimization on the modulation schemes that helps improve efficiency of the transmitter front-end. A comparison between 16/32-QAM, 16/32-APSK, 16/32-oAPSK and the proposed 16/32-pAPSK (Polar-filtered Amplitude Phase Shift Keying) modulation schemes are discussed. Some of the practical challenges in using mmWave communications for nano-satellite missions are addressed in this paper with a study on the state-of-the-art mmWave semiconductor technology that are suitable for SSPA (Solid State Power Amplifier) design specifically for nano-satellite missions.

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The inter-satellite link (ISL) in swarm and constellation missions is a key enabler in the autonomy of the mission. OLFAR (Orbiting Low Frequency Array for Radio astronomy) is one such mission where 10 to 50+ nanosatellites are placed in the Lunar orbit and perform astronomical observations from the far-side of the moon. Each of the nanosatellite in the swarm would carry a receiver that performs observations between 0.3 - 30 MHz, which are the least explored frequency bands in radio astronomy, thus attracting a large scientific interest.
Observations in this frequency bands from Earth are highly challenging as the ionosphere is opaque to these frequency bands. Furthermore, RFI (Radio Frequency Interferences) generated on Earth makes it highly challenging to perform astronomical observations below 30MHz band. The impediments faced by Earth-based or near-Earth-based radio astronomy for these frequency bands is the motivation to perform measurements from the far-side of the moon.
The purpose of using a swarm of nanosatellites to perform low frequency observations is to enable the realization of long observation baselines and additionally, the effective aperture of observation increases with the number of satellites. For the swarm of nanosatellites to operate as a single aperture, it is very important to cross-correlate the information collected by each satellite and this is where the ISL becomes very crucial. Apart from exchanging data collected by the payload, other information such as attitude and timing information needs to be exchanged.
This work derived mission level requirements which would be used to define a suitable communication architecture for space-based radio astronomy missions such as OLFAR. The approach chosen for communication system for such a swarm mission will comprise of two types of ISL: High data-rate directional link that will be used to exchange payload date and low data-rate omni-directional link that will be used to exchange attitude, timing information and be used for localization, positioning and ranging of the nanosatellites in the swarm. This work will present link budgets to show the feasibility of the proposed communication architecture and derive the specs to further design the transceivers.@en

Nano-satellite IoT/M2M missions are gaining popularity in recent time. Various companies have launched their pilot missions last year in 2018 and all these companies intend to place a constellation in (V)LEO that can communicate with low power sensors on the ground (sometimes remote locations) and relay it back to the end-user who is monitoring these sensors. This paper discusses two possible architectures of using nano-satellites for low latency IoT/M2M, by presenting information such as, number of satellites needed, number of orbital planes needed and communication strategy. The first proposed architecture will comprise of a self-sustaining network of nano-satellites that communicate with low power, low data-rate sensors on the ground and relay the data to rest of the nano-satellites in the network using inter-satellite links, which is downlinked by a nano-satellite that is in the view of a ground station that is connected to IMT. The second proposed architecture will use nano-satellites to communicate with low power, low data-rate sensors on the ground and relay it to satellites that intend to provide internet from space (Mega-constellation). The internet constellations considered in this study for the second architecture are: Telesat’s constellation, SpaceX’s Starlink, OneWeb’s constellation, Astrome’s SpaceNet constellation and Audacy’s constellation. Using both these architectures, it can be seen that the latency can be reduced considerably. @en

A fully integrated RFDAC based phase modulator in 40nm bulk CMOS is presented. To boost in-band linearity and the frequency range of operation, a harmonic rejection RFDAC architecture that suppresses the 3^rd and 5^th harmonics is proposed. The achieved frequency agility of the phase modulator is verified over a 0.6-2.5GHz range yielding EVM of -34.5dB and -36dB for an 18Mb/s and 75Mb/s GMSK signals, respectively. The power consumption of the proposed phase modulator is 33 mW at 2.4GHz.

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The 5G network has a goal to significantly increase its energy efficiency with respect to the energy draw of the LTE network. The decision to use OFDM-based modulation for 5G-NR forces a low-valued ceiling on achievable energy efficiency from any linear power amplifier. This ceiling is lowest for amplifiers operating at frequencies near and above 30 GHz: the millimeter-wave bands. Transistors behave differently at these high frequencies, and the modulation used must change to match to these different characteristics. Ring oriented constellations with polar filtering meet these changed conditions.

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