# Presentation: 186717

## L1 Modernization Project (L1C)

**Dr. Ken Hudnut, USGS**
**Capt. Amanda Jones, GPS Joint Program Office**
**1Lt. Sean Lenahan, GPS Joint Program Office**
**Tom Stansell, L1C Project Coordinator**

*CGSIC 45**th** Meeting**Long Beach, California;  **September 12, 2005*

## Background (1 of 3)

**The Interagency GPS Executive Board (IGEB) funded an L1C Signal Definition Project**
**Co-chaired by the U.S. Geological Survey (USGS) and the GPS Joint Program Office (JPO)**
**First phase of the project was completed in 2004**
**Report posted on two WEB sites ****www.pnt.gov ****and www.navcen.uscg.gov/gps/modernization/**
**Thanks to those who participated in the first L1C survey**
**Your contributions were very important and moved us closer to the final L1C definition**

## Slide 3

## Background (2 of 3)

**Last year at this meeting Dr. Hudnut reviewed conclusions of the Phase I report**
**You may recall the debate which ensued **
**The specific issue was not a problem after all**
**The first survey results recommended:**
**Implementing L1C in addition to the C/A signal**
**The BOC(1,1) waveform**
**A more robust data channel**
**We also were guided toward more use of alternate communication means**

## Background (3 of 3)

**A second phase of the L1C Project was approved in 2005**
**Intended to complete the definition of L1C**
**The IGEB has been replaced by the National Space-Based Positioning, Navigation, and Timing Executive Committee (the EXCOM) **
**Final L1C report will be submitted to the EXCOM**
**New JPO participants**

## L1C Team Leadership

**L1C Team Leadership**

**1Lt. Sean Lenahan****GPS JPO**

**Tom Stansell****Coordinator**

**Capt. Amanda Jones****Co-Chair, GPS JPO**

**Dr. Ken Hudnut****Co-Chair, USGS**

## And An Experienced Technical Team

**The following members of the L1C Technical Team have made important contributions to the signal definition and this presentation:**

**Lt. Col. Jon Anderson, USAF**
**Dr. John Betz, MITRE**
**Dr. Charles Cahn, Consultant**
**Dr. Phil Dafesh, Aerospace**
**Dr. Chris Hegarty, MITRE**

**Mr. Rich Keegan, Consultant**
**Mr. Karl Kovach, ARINC**
**Dr. Howard Ma, MITRE**
**Dr. Joe Rushanan, MITRE**
**Mr. Soon Yi, ARINC**

## Introduction to New L1C Questionnaire

**We request your advice on the L1C design by choosing from five signal options**
**We want to know why and to what extent you favor one option over the others**
**This presentation provides the information needed to make informed choices**

## Looking Into the Future

**GPS + Galileo provides better geometry**
**UWB and other sources raise the noise floor**
**Moore’s law continues to apply**
**> 10 times digital improvement before L1C launch**
**Improved technology will allow better performance**
**Proliferation of GPS communication sources**
**Cell phones, wireless internet, SBAS, GBAS, etc.**
**Alternate GPS message sources will provide**
**Long-lasting clock and ephemeris for all satellites**
**Integrity and differential correction messages**
**User alerts, e.g., software updates, system status, etc.**

## L1C Shares L2C & L5 Improvements

**L1C builds on improved characteristics of other modernized GPS signals:**
**Signal power split between data & data-less parts**
**Data-less part is a pilot carrier**
**Better tracking threshold **
**Eliminates 1⁄2 cycle phase ambiguities **
**Forward error correction (FEC) improves (lowers) message demodulation threshold**
**Longer spreading codes **
**Reduce susceptibility to narrowband and cross-satellite interference**
**Resolve data timing ambiguity (no bit sync required)**

## Additional L1C Improvements (1 of 2)

**After the 1****st****  L1C report, we found a way: **
**To increase the data rate for faster time to first fix **
**While being able to demodulate the vital message data at the lowest tracking threshold**
**This message structure is (herein) called CNAV-2**
**L2C and L5 messages are called CNAV**
**Other L1C message improvements**
**More powerful FEC further improves demodulation**
**Interleaving minimizes effect of short fades**
**e.g., driving past trees or other obstructions**

## L1C Improvements Defined (1 of 2)

## L1C Improvements Defined (2 of 2)

## Carrier and Data Power Allocations

**Fastest****TTFF & Variable Messages**

**Best Code & Carrier Track****Threshold**

**Most Robust Variable****Messages**

**With 50 or 75 bps?**

## Questionnaire Choices

**Questionnaire Choices**

## Page 1 of the Questionnaire

**Page 1 of the Questionnaire**

## Page 2 of the Questionnaire

**Page 2 of the Questionnaire**

## Participants in an initial briefing in Tokyo on 8 Sept. 2005

**Participants in an initial briefing in Tokyo on ****8 Sept. 2005**

## Please Participate

**Please participate in the new L1C Survey**
**Sign up on the list, or**
**Give us your card marked with a request**
**Surveys can be conducted almost **_**anywhere**_** (even simultaneously at multiple locations) using telephone and an Internet connection **
**Windows only**

## End of Presentation

- The L1C Project was initiated and funded by the Interagency GPS Executive Board (IGEB) with substantial support also provided by the U.S. Air Force GPS Joint Program Office (JPO) and the Federal Aviation Administration (FAA)