Signal Deformation Proposal R. Eric Phelts, Gabriel Wong, Todd Walter, Per Enge Stanford University IWG 26 February 5-7, 2014

Potential L1/L5 Tracking Constraints Current constraints allow early minus late (E-L) and double delta (DD) receivers – each have three regions describing receiver filter bandwidth, group-delay variation across the passband, and correlator spacing –SBAS GEOs have two regions Propose removing double delta altogether and shrinking allowed region –Also align SBAS & GPS tracking regions –BOC regions still being investigated 2

3 Current Allowed L1 Receiver Constraints Nominal SD Range Error Contours for WAAS Users User Receiver Correlator Spacing (chips) User Receiver Bandwidth (MHz) User Receiver Correlator Spacing (chips) User Receiver Bandwidth (MHz) New Reference Current Reference New Reference

4 Different code modulations have similar structures at chip transitions. Nominal Signal Deformations on L1 and L5 Slide Courtesy: Gabriel Wong

5 New Proposed Allowed DF Receiver Constraints (L1, L5) Nominal SD Range Error Contours for WAAS Users User Receiver Correlator Spacing (chips) User Receiver Bandwidth (MHz) User Receiver Correlator Spacing (chips) User Receiver Bandwidth (MHz) L5 L1

Proposal for BPSK Signals Only allow early minus late L1 C/A –Bandwidth between 12 and 24 MHz –Correlator spacing between 0.08 and 0.12 –Group delay < 150 nsec (including antenna) L5/E5A –Bandwidth = tight region around 24 MHz –Correlator spacing = tight region around 1 chip Exact region TBD –Group delay < 150 nsec (including antenna) 6

Proposal for SBAS Satellites Wide bandwidth SBAS satellites shall be treated identically to the BPSK requirements for GPS Narrow bandwidth SBAS satellites require one of the following actions: –Narrow bandwidth SBAS satellites not allowed –Bandwidth is indicated in message Tracked differently, may not be used for vertical –Still tracked with narrow correlator, but UDRE indicates it cannot be used for vertical 7

8 Example: Digital Signal Deformation Fault on CBOC(1,1) or TMBOC(1,1) Code Offset (chips) Some modernized code correlation peaks are relatively complex

Proposal for BOC Signals EUROCAE WG-62 proposed not using BOC(6,1) component –Agree to only track BOC(1,1) Same filter region as for L1 BPSK – Bandwidth between 16 and 24 MHz –Group delay < 150 nsec (including antenna) –Correlator spacing still under evaluation Early minus late only 9

Backup Slides 10

11 User Receiver Correlator Spacing (chips) User Receiver Bandwidth (MHz) Propose removal Nominal L1 SD Range Errors for Allowed User Receiver Configurations

L5 Nominal Deformation Errors (Updated) Correlator Spacing (chips) Bandwidth (MHz)