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Code Division Multiple Access (CDMA) Radio Development for Small Satellites

Description:

TECHNOLOGY AREA(S): Space Platforms 

OBJECTIVE: Demonstrate a bi-directional Code Division Multiple Access (CDMA) radio in a ~(1Ux1Ux0.5U) CubeSat form factor for low & high data rates. 

DESCRIPTION: Code Division Multiple Access (CDMA) radios allow multiple spacecraft to communicate simultaneously within the same ground station beam, helping to minimize the programmatic and ground station complexities of individual frequencies for missions such as formation flying or constellations. Additionally, as requests for frequency allocations increase, having a means to use the same spectrum for multiple users provides added relief to the congested spectrum beyond spatial and temporal coordination. The Small Satellite Community would benefit from this capability designed for the small satellite form factor, with the inherent constraints on size and power. The purpose of this research is to develop a CDMA radio in an approximately 1Ux1Ux0.5U CubeSat form factor for low & high data rates. Phase 1 emphasizes CDMA development with real-time acquisition on a spacecraft downlink using the nominal Size, Weight and Power (SWaP) available for a 3U satellite communications system. Phase 2 advances the research, design and demonstration to include bi-directional CDMA capability, bi-directional data-rate throttling and bi-direction automatic request queries. 

PHASE I: (1) Design & deliver micro-processor & Intermediate Frequency (IF) chain card & software featuring a CDMA high-data-rate downlink implementation. Combined w/ anticipated spacecraft RF front-end components, form factor should be ~ 1Ux1Ux0.5U. (2) Demo CDMA downlink capability & parallel processing of multiple signals acquired by ground station (may be laboratory setting using spacecraft hardware). 

PHASE II: Design, deliver and demonstrate: (1) Prototype micro-processor & IF card with the following capabilities: CDMA uplink/downlink, bi-directional data-rate throttling at low & high data rates, bi-directional automatic request queries, (2) Prototype of spacecraft uplink and downlink RF front-end card, (3) Prototype of ground segment. Items (1) and (2) together should have approximately (1Ux1Ux0.5U) SWaP or less. 

PHASE III: Improvements in communication systems have benefits for all small satellite applications: military, commercial and civil. Demonstrate using a prototype system the broad set of applications for which this subsystem may support. 

REFERENCES: 

1: Vazquez Castro, M.A et al. (2007). Multiuser Satellite Communications. In G. E. Corazza (Ed.), Digital Satellite Communications (pp. 367-415). New York, NY: Springer.

2: Babuscia, A., Divsalar, D., Cheung, K.M., & Lee, C. (2016). CDMA communication system performance for a constellation of CubeSats around the Moon. 2016 IEEE Aerospace Conference, AERO 2016, 5-12 March, Big Sky, MT, IEEE Computer Society, 2016.

KEYWORDS: Small Satellite Communications System, Code Division Multiple Access (CDMA), CubeSat Communications 

CONTACT(S): 

Kyle Kemble (AFRL/RVEP) 

(505) 853-2545 

kyle.kemble.2@us.af.mil 

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