diff --git a/gnss/1.1/IGnssMeasurementCallback.hal b/gnss/1.1/IGnssMeasurementCallback.hal
index 36841ee..f94c67a 100644
--- a/gnss/1.1/IGnssMeasurementCallback.hal
+++ b/gnss/1.1/IGnssMeasurementCallback.hal
@@ -24,13 +24,38 @@
      * Flags indicating the Accumulated Delta Range's states.
      *
      * See the table below for a detailed interpretation of each state. This is
-     * a continuation of the table from 1.1/IGnssMeasurementCallback.hal.
+     * a continuation of the table from 1.0/IGnssMeasurementCallback.hal.
      *
      * +---------------------+-------------------+-----------------------------+
      * | ADR_STATE           | Time of relevance | Interpretation              |
      * +---------------------+-------------------+-----------------------------+
      * | HALF_CYCLE_RESOLVED | ADR(t)            | Half cycle ambiguity is     |
      * |                     |                   | resolved at time t.         |
+     * |                     |                   |                             |
+     * |                     |                   | For signals that have       |
+     * |                     |                   | databits, the carrier phase |
+     * |                     |                   | tracking loops typically    |
+     * |                     |                   | use a costas loop           |
+     * |                     |                   | discriminator. This type of |
+     * |                     |                   | tracking loop introduces a  |
+     * |                     |                   | half-cycle ambiguity that   |
+     * |                     |                   | is resolved by searching    |
+     * |                     |                   | through the received data   |
+     * |                     |                   | for known patterns of       |
+     * |                     |                   | databits (e.g. GPS uses the |
+     * |                     |                   | TLM word) which then        |
+     * |                     |                   | determines the polarity of  |
+     * |                     |                   | the incoming data and       |
+     * |                     |                   | resolves the half-cycle     |
+     * |                     |                   | ambiguity.                  |
+     * |                     |                   |                             |
+     * |                     |                   | Before the half-cycle       |
+     * |                     |                   | ambiguity has been resolved |
+     * |                     |                   | it is possible that the     |
+     * |                     |                   | ADR_STATE_VALID flag is     |
+     * |                     |                   | set, but the ADR_STATE_     |
+     * |                     |                   | HALF_CYCLE_RESOLVED flag is |
+     * |                     |                   | not set.                    |
      * +---------------------+-------------------+-----------------------------+
      */
     enum GnssAccumulatedDeltaRangeState
diff --git a/gnss/aidl/android/hardware/gnss/GnssMeasurement.aidl b/gnss/aidl/android/hardware/gnss/GnssMeasurement.aidl
index 58f29c5..efecddd 100644
--- a/gnss/aidl/android/hardware/gnss/GnssMeasurement.aidl
+++ b/gnss/aidl/android/hardware/gnss/GnssMeasurement.aidl
@@ -438,6 +438,31 @@
      * +---------------------+-------------------+-----------------------------+
      * | HALF_CYCLE_RESOLVED | ADR(t)            | Half cycle ambiguity is     |
      * |                     |                   | resolved at time t.         |
+     * |                     |                   |                             |
+     * |                     |                   | For signals that have       |
+     * |                     |                   | databits, the carrier phase |
+     * |                     |                   | tracking loops typically    |
+     * |                     |                   | use a costas loop           |
+     * |                     |                   | discriminator. This type of |
+     * |                     |                   | tracking loop introduces a  |
+     * |                     |                   | half-cycle ambiguity that   |
+     * |                     |                   | is resolved by searching    |
+     * |                     |                   | through the received data   |
+     * |                     |                   | for known patterns of       |
+     * |                     |                   | databits (e.g. GPS uses the |
+     * |                     |                   | TLM word) which then        |
+     * |                     |                   | determines the polarity of  |
+     * |                     |                   | the incoming data and       |
+     * |                     |                   | resolves the half-cycle     |
+     * |                     |                   | ambiguity.                  |
+     * |                     |                   |                             |
+     * |                     |                   | Before the half-cycle       |
+     * |                     |                   | ambiguity has been resolved |
+     * |                     |                   | it is possible that the     |
+     * |                     |                   | ADR_STATE_VALID flag is     |
+     * |                     |                   | set, but the ADR_STATE_     |
+     * |                     |                   | HALF_CYCLE_RESOLVED flag is |
+     * |                     |                   | not set.                    |
      * +---------------------+-------------------+-----------------------------+
      */
     const int ADR_STATE_UNKNOWN = 0;