4.1 Scope:  In accordance with the solicitation, the scope encompasses:

a) A full characterization of “atmospheric propagation physics at 71 – 76 GHz and 81 – 86 GHz to support systems engineering, assessment and design of future operational military satellite communication architectures and systems.”

b) “Develop and validate communication link models over the 71 – 76 GHz and 81 – 86 GHz frequency bandwidths.”

 

Phase I will:

a) Specify the necessary physical infrastructure to achieve the above.

b) Catalogue, characterize and integrate models necessary for Phases 2 – 5.

c) Build a simulation environment for characterizing the physical channel and validating the communication link.  The components of this simulation environment are outlined in paragraph 4.3 below.

d) Publish a System Design Document that integrates the physical infrastructure and simulation environment into an overall architecture.  A notional architecture is outlined in paragraph 4.3 below.

e) Publish an Experiment Plan that includes a variety of experiments to be conducted within the system outlined by the System Design Document.  The experiments to characterize the physical channel will be informed by details outlined in paragraphs 3.1 and 3.2 above.  The communications and link model experiments will be informed by paragraphs 3.6 – 3.8 above.

f) Publish Risk Assessment, Interface Definition and Environment Definition to ensure the feasibility of system deployment.



NOTE:  This proposal considers only the atmospheric propagation physics outlined in paragraph 3.0 above.  Other environments of interest to the military (e.g. W/V-band propagation through sand storms) can be added.
Also, only stationary ground units are proposed.  Issues of on-the-move command and control can also be considered for inclusion.

 

Technology Area: Atmospheric physics, meteorology, EHF propagation, satellite communications, steerable beam antennas, signal processing, modeling and simulation.



Objectives / Goals:  At the end of Phase 1 all documents listed below will be published; and a complete modeling and simulation environment for the conduct of Phases 2 – 5 will be in place.  The System Design Document will define the architecture of WSCE in sufficient detail to allow for its rapid execution.

 

Major Milestones:  See section 4.4.

4.2 Applicable Documents:  See section 3.0.

4.3 Requirements:  As stated in the solicitation, the key Phase 1 objective is to perform: “Modeling and simulation to demonstrate that the proposed concept is feasible and will meet mission requirements (propagation channel, link, RF systems, size, weight, power requirements).”



4.3.1 Outline of effort:  An extensive modeling and simulation regimen is proposed, to include:

a) Physical Propagation Models: an extensive review and cataloging of existing and proposed models.  A careful analysis of how they can be combined to address all aspects of propagation through the troposphere.  This will be critical when exercising fade mitigation techniques (FMT) in the communications part of WSCE.
 

b) Channel Models: a review of the existing literature.  The purpose is to clarify what first and second order statistics are necessary; and to guide the follow-on data collection effort in the propagation characterization part of WSCE.  As a mathematical characterization of the physical channel evolves, this will be incorporated into the communications part of WSCE.
 

c) Antenna Models:  Antennas are critical because: that is where the experiment touches the physical channel being characterized; and they are an integral part of the FMT portion of the communications experiment.  Detailed specifications for all ground and flight antennas will be prepared.  Furthermore, a set of antennas models will be maintained throughout all five phases of WSCE.  This will not only facilitate analysis of the data sets; it will allow seamless normalization of the data if upgrades are made to the ground antennas as better technology becomes available.
 

d) Hardware Models:  As the WSCE hardware specification is refined simulations will be run to ensure interoperability of components, robustness in the face of errors and achievement of overall system metrics.
 

e) Error Coding, Modulation and FMT:  The communication portion of the Experiment Plan will outline a full portfolio of schemes for exercising these capabilities in a wide variety of physical environments.  Each scheme will model error coding, modulation and FMT; and will use the model results of paragraphs a.) – d.) above as a basis.

 

4.3.2 Notional system architecture:

A central control facility located in Atlanta will coordinate all experiments.  With full access to National Weather Service data and imagery, a series of communication and propagation experiments can be planned that exploit unique weather events.  Full use will be made of weather forecasting for experiment planning; and now-casting for FMT.  These experiments will augment the long-term data collection efforts planned for a variety of locations across the United States.  This central control facility will have Internet access to all semi-permanent facilities, but not necessarily to all deployable stations.

A number of semi-permanent stations will be situated for data collection over a four-year period.  Sites will be chosen based on climate, weather, look angle, environmental factors and Internet access.  These will provide long-term physical propagation statistics that will be incorporated into the modeling and simulation environment.  They will also contribute significantly to the communications experiments.

A separate fleet of deployable stations will be placed as opportunities arise.  They can be a valuable assist to FMT studies; as well as providing spatial diversity to the semi-permanent stations in specific meteorological conditions.

This type of flexible architecture is enabled by the use of steerable beam antennas on the satellite.  Dedicated spot beams on the central control facility and semi-permanent stations can vary signal strength and polarity as needed.  Steerable beams can do the same for the deployable stations.  This will significantly enhance the regimen for FMT studies.  It may also provide valuable data towards constructing system availability curves.

All stations will have a separate channel (either Ku or Ka) for uplink power control and frequency diversity within the FMT experiment regimen.

The data collected will be shared with the ESA and used to refine the models within the WSCE modelling and simulation environment.  This should allow rapid detection of anomalous tropospheric behavior that needs further investigation.
The on-board flight hardware will allow ready changes to the modulation and error coding schemes in use during given atmospheric conditions.  This in conjunction with the steerable beam antennas will allow rapid development of BER profiles.



4.3.3 Work Breakdown Structure:  The anticipated WBS is: