Development of UHF Satcom Frequency reuse planning tool

Junghoon Lee*1, Anthony Vescio*1, Tony Puzio*1, George Elmasry*1,

Richard Ardolino*2, and Austin Mroczek*3

*1. XPRT Solutions, Inc., Eatontown, NJ
*2. Space and Naval Warfare Systems Command, San Diego, CA
*3. SBG Technology Solutions, Inc., Stafford, VA

ABSTRACT

U.S. Navy’s UHF SATCOM operation needs a tool to automate the frequency planning process, maximizing the efficiency of the spectrum use. This paper presents a UHF SATCOM frequency reuse planning tool developed for the operational needs. The design concept of the Tool is explained in consideration of the technical analyses needs and usability of the software for the UHF SATCOM operation. The multi-tier architecture of the software application is described. The analytical functions are programmed using MATLAB for ease of the software development. The major capabilities and features of the Tool are described with its benefits to the SATCOM operation.

Analyses results with reference to an illustrative operational scenario demonstrate that the Tool can provide technical analyses needed for the UHF SATCOM operation. Having reviewed by UHF SATCOM community including GSSC, the Tool has shown the applicability to the operation.

I. INTRODUCTION

Frequency planning for UHF SATCOM is an increasingly complex and important issue for the Navy’s operation, as the demand for the communications capacity has continuously been growing while the spectrum resources are limited. In particular, the SATCOM operation needs to reuse (in fact, has been reusing in some cases) the UHF frequency channels to accommodate the communications demand. Currently, such a UHF SATCOM channel frequency planning has been manually performed by SATCOM engineers. This paper[1] presents a UHF SATCOM Frequency Reuse Planning Tool (UFPT), which can automate the frequency planning process, maximizing the efficiency of the spectrum use.

While the concept of maximizing the spectrum efficiency is not new, the planning process for the UHF SATCOM not only takes a lot of time and effort but also requires technical expertise, if the tasks are manually performed by engineers. In some circumstances, the operation may have to be content with a suboptimum solution due to a constraint on time and engineering cost. UFPT has been developed to provide technical analyses required for the UHF SATCOM frequency planning, thus saving the time, effort, and cost.

One of the primary objectives of developing UFPT is to support SATCOM operation for Global SATCOM Support Center (GSSC). Currently, processing Satellite Access Request (SAR), which asks for a SATCOM channel, GSSC personnel often look into a large amount of satellite configuration data typically given in spreadsheets. Searching the SATCOM channel, they must take into account variety of information such as the user’s location or operational area, required carrier bandwidth or data rate, priority, existing channel allocation, etc., to identify the most appropriate channel to satisfy the request. The planner must also analyze link margins for potential channels. They even have to consider if a channel frequency is reused at adjacent satellites. This is a very tedious and time-consuming task. The purpose of developing UFPT is to help automate the frequency planning process by providing the technical analyses for searching and identifying a channel, which satisfies the operational needs.

Section II explains the design concept of the Tool. The software architecture of the Tool is described in section III. Section IV presents the capabilities and features of the Tool and discusses on how it supports the SATCOM operation.

II. Design concept of the tool

This section discusses technical analyses needed to support the SATCOM planning and usability of the Tool for the operation. The major analytical capabilities of the Tool are explained as follows:

Satellite Beam Coverage and Overlap: In searching a channel for an access request, the SATCOM operation needs to investigate if a particular UHF channel can cover the user’s operational area. That is, the satellite beam coverage area should be analyzed. In practice, searching for reusable frequencies, the operation also needs to analyze what and how much portion of the operational area is overlapped with an adjacent satellite beam coverage area, in consideration of interference when a UHF channel is reused between a pair of adjacent satellites.

Link Analysis: Link performance or link margin needs to be analyzed for each and every potential UHF channel to be allocated. The link analysis should take into account any possible interference from adjacent satellites for the case that a same channel is used among the satellites. Also the Tool needs to support link analysis for hypothetical operational parameter variations as the operation wants to answer what-if cases for the planning purposes.

Searching and Identifying Reusable Channels The Tool should be capable of finding a channel, which not only satisfies the communications user’s needs but also uses the SATCOM spectrum resource most efficiently.

Establishing and Evaluating Hypothetical Scenarios: The Tool should enable the operation to establish and evaluate potential SATCOM operations scenarios, representing various satellite channel configurations.

The following is a list of the Tool features considering the usability for the SATCOM operation:

Internet-based Access: Internet-based application allows users to access the Tool anywhere, retrieving common operational data and scenarios. The server-client architecture allows the operation to easily maintain and upgrade the Tool software.

Modular Structure: The Tool would need modification and enhancement as the operational requirements evolve and new functionalities are demanded. The Tool should be based on modular architecture so that the future modifications can be made without affecting the reliability and integrity of the Tool.

Default Scenario Management: The Tool maintains current channel configuration and allocation for the users to retrieve and investigate. The default scenario will be managed users with privileged access to the Tool.

Other Utilities will include: validating input data, forced logging-out on user inactivity for security, and printer-friendly pages for downloading and reporting the results.

III. Software architecture of the tool

The software of the Tool (or the “Application”) is based on a standard multi-tier architecture. The objective of this architecture is to clearly separate the user presentation, the application processing, and the data manipulation and storage. This multi-tier design provides a flexible and reusable application, and is intended to allow any of the tiers to be upgraded independently as the requirements or technologies change. Each Application tier, or layer, is comprised of components and services specific to that layer, as shown in Figure 1.

[pic]

Figure 1: Software Architecture of the Tool

The MATLAB Layer is comprised of components developed with the MATLAB® software product [3]. The components contain MATLAB functions (m-Files) and MATLAB data storage (mat-files). They represent the Application’s analytical and computational engine and storage repository, respectively. The MATLAB functions are compiled into a deployable component using the MATLAB Builder JA® software product [4]. The Builder creates a ‘wrapper’ class that can be integrated into the Server Layer’s JAVA programs. The MATLAB functions provide analytical and computational services for the Application. For example, the Application software includes MATLAB functions to calculate link margins and generate the link margin contour maps. The Application uses MATLAB data files, i.e. ‘mat-files’, as the Application’s central repository. The data includes scenarios, which consist of satellites and the channel configurations, as well as the analysis results to be presented.

Use of MATLAB® facilitates the overall Tool development. With MATLAB®, technical analyses formulas and processes are easily programmed, reviewed, and validated. The programs are compiled and used in the production software without any modification or adaptation. The Builder JA® also enables the MATLAB programs to be integrated with software written in JAVA, which is a popular programming language for this kind of Tool development.

The Server Layer, or business services layer, provides the interface between the Presentation Layer and the MATLAB Layer. When the Presentation Layer requests data or calculation, the Server Layer packages the request in a format that is required by the MATLAB functions in the MATLAB Layer. The Server Layer is also responsible for converting results that are in MATLAB-specific data types to standard JAVA data types or classes that the Presentation Layer can interpret.

The Server Layer is comprised of JAVA Beans, JAVA Servlets, and Web Services. The JAVA Bean components provide the core of the business services for the Application. The JAVA Beans provide logging services using the Apache log4j software. The utility class implements log4j to provide the Application with the facility to record user activity and system messages to text files on the Server. A rollingfileappender mechanism manages the log file size and log file count (currently set by 2 MB and 10 files maximum, respectively for the Tool). The log file parameters are configurable in the log4j.properties file. The JAVA Beans also handle Application security with a Login Manager Bean component. A List Factory component provides data to populate selection lists in the Presentation Layer.

For security purposes, the Application has a session timeout set by 10 minutes. This means that if a web page is not accessed during that time period, the Application will require the user to re-login. The session timeout period is configurable in the Application’s web.xml file. The Application also provides the user with the ability to produce printer-friendly documents of any web page that displays information. This service is handled by JAVA Servlets that are resident in the Server Layer.

The Application utilizes AJAX (Asynchronous JavaScript and XML) technologies and Web Services to enhance the user-experience and perform partial-screen updates on web pages. Web Services, for example, provide the list of satellites for searching channel. The Web Services are accessed via asynchronous XMLHHTPRequest calls from the web pages.

The Presentation Layer is comprised of the JAVA Server Pages (JSP), which the user can access from a standard desktop browser. The Application has been designed to support the Microsoft Internet Explorer v6.0+, Mozilla Firefox 3.0+ and Safari 4.0+ web browsers. The JSP pages implement common blocks of code in the form of include pages, such as page header/footer logic and application menu logic. This approach eliminates redundant code, improves maintainability, and provides a consistent look-and-feel throughout the application. The JSP pages contain JavaScript code to provide client-side validation of user-input and to provide information to the user, such as requests to confirm the deletion of any data in the application. The JavaScript code also supports the AJAX calls to reduce round-trip time for requests to web server.

IV. capabilities and features of the tool

This section describes major capabilities of UFPT and how the Tool benefits the operational planner by promptly providing data necessary to complete their operational analyses for a SAR. With just a few clicks, the web-based Tool enables the SATCOM planner to enter, browse, and modify the parameters associated with a given operational scenario. Then, the Tool generates and shows on-screen reports for the analysis results. It allows planners to analyze channel availability, and search and identify available satellite channels in accordance with the given SAR. Following the instructions given by the Tool, user can modify, save, and search parameters. The Tool enables to manage hypothetical operational scenarios representing satellite location and channel configuration. The analysis methodologies and the related formulas are given in [5].

Satellite Channel Availability

The satellite channel availability function allows the operational planner to analyze satellite beam coverage and overlap with adjacent satellite channels to investigate the impact of interference. For each channel of every satellite, the user can analyze whether the channel has interference from adjacent satellites, and if there is coverage overlap, the percentage of overlapped area. Figure 2 illustrates the Tool’s analysis results for Channel 2 of FSC-8, with reference to a scenario given for demonstrating the feasibility of the Tool. The Tool analyzes link margin for every location within the coverage area and shows the link margin contour in colors of gradual shades, on a world map. In this case, it identifies the interfering satellite channels (UFO-5 Channel 2 and FCS-8 Channel 2) and provides the percentage of coverage overlap (37% and 16%, respectively).

The Tool also provides satellite channel availability for an operation area given by user. It autonomously identifies which satellite channels are available for the area and which channels from adjacent channels create interference to the area. Using the demonstration scenario, Figure 3 illustrates the Tool’s analysis results for the area bounded by 114.5° West, 57.3° West, 41.2° North, and 22.5° South. For the case, user has selected UFO-5 channel 7 among the list of channels covering the area, given by the Tool. The Tool analyzes link margin for every location within the operational area and shows the link margin contour. It also calculates the percentage of overlap for the operational area as 49%.

[pic]

Figure 2: Illustrative Results on Satellite Channel
Analysis (FSC-8, Channel 2)

[pic]

Figure 3: Illustrative Results on Satellite Channel
Analysis (UFO-5 Channel 7)

Customized Link Analysis

This capability is developed for the operation to answer “what-if” cases, for example, what will be the link margin if directional antennas are used. For such a purpose, the Tool provides parametrical link analysis. That is, the Tool can provide link performances for the operational parameter variations from the baseline link analysis. The Tool allows user to modify: terminal type, antenna type (for communicator and interfering terminals), terminal platform (including ship, shore, submairne, and aircraft), and carrier characteristics including modulation, symbol rate, and Forward Error Correction (FEC) rate. Figure 4 illustrates the link margin contour for the case that directional antennas with 10 dB gain are used for the receiver and two interfering terminals accessing UFO-5 and FSC-7, respectively.

[pic]

Figure 4: Illustrative Results on Satellite Channel
Analysis (Use of 10 dB gain antennas)

Channel Search

The Tool allows user to specify a set of search parameters describing the attributes of communications channel required to support a SAR. The channel search input is illustrated in Figure 5. User can limit the search by specifying the Service Support Center managing the channel, coverage region (ATLANTIC, INDIAN, PACIFIC, or CONUS), user priority; channel bandwidth, access type (Dedicated, DAMA, or IW), and the satellite. User also can select “Any” to search for any applicable channels, except the coverage region, which must be specified if the operational area is not configured. When the operational area is entered, the Tool investigates and automatically fills the menu items by the list of available satellites, which can cover the area in accordance with the percentage of minimum coverage given.

The search algorithm first identifies all suitable channels, i.e., ones that meet the specified criteria. For each suitable channel, the Tool identifies same frequency channels on other satellites that can cause interference due to the coverage overlap. For each interfering channel, the percent of area overlap is computed. Then the degree of suitability of each channel is assessed in part by the sum of the percent overlapping areas for all interfering channels. Another factor in the suitability is priority. If the priority of the channel’s current service is lower than the priority of the requested, the channel can be preempted to support the new request. The Tool defines four classes of suitability:

• Available, which means that the channel is not in use • Preemptible, which means the channel can be preempted while the total overlap is less than 50% • Overlapped, which means that the channel can be preempted but the total overlap more than 50% • Not Preemptible, which means that the channel cannot be preempted

For the Available class, the channels are ranked in increasing order of the percentage of the total overlap area. For all other classes, channels are ranked in decreasing order of priority. Table 1 illustrates a channel search results (showing selected channels among the 115 applicable channels) for the input parameters given in Figure 5, with reference to the demonstration scenario.

[pic]

Figure 5: Channel Search Parameter Input

Table 1: Illustration of Channel Search Results
(for the area bounded by 65° West, 0° East, 60° North, and 60° South)

|# |
|24 |
|96 |

114 |ATLANTIC FSC-8 15.5W |7/C |25 |306.55 |265.55 |Dedicated |1A |On |GSSC |52 |Overlapped | |115 |ATLANTIC FSC-8 15.5W |7/C |25 |306.55 |265.55 |Dedicated |1A |On |GSSC |1 |Overlapped | |
The Tool also provides another channel search algorithm, which is based on the magnitude of link margin rather than the total coverage overlap, as described in [5].

Management of Operational Scenario

UFPT is designed based on a web-based architecture. This allows SATCOM planners from anywhere in the world to gain access with only an internet connection and a browser. When a planner signs into the tool, an initial scenario is created from the master default scenario file that holds the latest satellite configuration. This allows planners the ability to investigate current operational parameters including satellite location and channel configuration. Planners can create “what-if” scenarios representing hypothetical satellite and channel configuration, and then save them on the Tool’s bulletin board for other users to access, or save as a private scenario for the creator only to view. The Tool allows a “Privileged User” to manage confidential data and manage default scenarios, i.e., create, archive, delete, or reinstate past default scenarios as needed. The Tool has the capability to delete, modify, or add new satellites configurations with just a few clicks of a button. This gives flexibility to anyone who wants to make changes to channel pairs and instantly view the changed frequency overlap interference contour plots. For example, if the planner wants to create a scenario where UFO-2 is no longer available and they need to move adjacent satellites to cover the gap, the planner just needs to delete the UFO-2 satellite and move the adjacent satellites to new longitude coordinates, modify any channel frequency pairs, and finally save the scenario to the bulletin board. The operational planner can now quickly view the operational circumstances channel by channel based on the modification.

Applications Software Features

The following is a list of additional software features of the Tool:

• Input data validation: Checking user’s input for the parameter’s range, the Tool alerts the user to correct if the value is not valid. For some parameters, the Tool automatically corrects or enters associated values. For example, uplink and downlink frequencies of a channel is automatically entered or corrected in accordance with the channel number and frequency plan given, with reference to the associated military standard. • Forced logging-out on inactivity: To prevent access from unauthorized user, the Tool forcibly logs out a user as described in section III. • Printer-friendly page: For the results generated, the Tool provides printer-friendly html pages for downloading and reporting the results. The contents can easily be cut and pasted to a Microsoft Word® document.

V. Summary and discussion

This paper presents considerations and benefits of UFPT, developed to automate the UHF SATCOM frequency planning processes. The design concept of the Tool is explained in consideration of the technical analyses needs and usability of the software for the UHF SATCOM operation. The multi-tier architecture of the software application is described. The analytical functions are programmed using MATLAB for ease of the software development. The major capabilities and features of the Tool are described with the benefits to the SATCOM operation.

Analyses results with reference to the illustrative operational scenario demonstrate that the Tool can provide technical analyses needed for the UHF SATCOM operation. Having reviewed by UHF SATCOM community including GSSC, the Tool has shown the applicability to the operation.

VII. REFERENCES

1] “Ultra High Frequency (UHF) Reuse Planning Tool for Increasing Capacity in Geo-Synchronous Satellite Communications (SATCOM) Systems”, SBIR N07-192 Phase I Final Report, XPRT Solutions, November, 2008. 2] “Ultra High Frequency (UHF) Reuse Planning Tool for Increasing Capacity in Geo-Synchronous Satellite Communications (SATCOM) Systems”, SBIR N07-192 Phase II Final Report, XPRT Solutions, March, 2011. 3] http://www.mathworks.com/products/matlab/ 4] http://www.mathworks.com/products/javabuilder/ 5] J. Lee, et al, “A Study on UHF SATCOM Frequency Reuse”, to be submitted in IEEE MILCOM 2011, October 2011.

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[1] This paper is based on a research conducted under SBIR titled “Ultra High Frequency (UHF) Reuse Planning Tool for Increasing Capacity in Geo-Synchronous Satellite Communications (SATCOM) Systems” [1][2], sponsored by Space and Naval Warfare Systems Command (SPAWAR).

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AJAX

JavaScript

JAVA Server Pages (JSP)

Web Services

JAVA Servlets

JAVA Beans

MATLAB Data Storage

MATLAB Functions

Server Layer

MATLAB Layer

Presentation Layer

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