feat: add NR NTN access detection

Detect Non-Terrestrial Network access by checking for the
NRNTN-TAI-Information protocol extension (ID 287 per 3GPP
TS 38.413) in UserLocationInformationNR received via NGAP,
and track the result in a new NtnAccessInfo struct on AmfUe
and RanUe.

This is detection-only groundwork. No protocol behavior
changes: nothing reads the flag yet. Future patches can
extend NtnAccessInfo with satellite backhaul category,
GEO satellite ID, and NTN TAI list as those fields become
available in omec-project/openapi and omec-project/ngap.

Signed-off-by: Vinod Patmanathan <vinod.patmanathan@forsway.com>

Author: Vinod Patmanathan

context/amf_ue.go

@@ -101,6 +101,7 @@ type AmfUe struct {
 	EventSubscriptionsInfo map[string]*AmfUeEventSubscription `json:"eventSubscriptionInfo,omitempty"`
 	/* User Location*/
 	RatType                  models.RatType      `json:"ratType,omitempty"`
+	NtnAccess                *NtnAccessInfo      `json:"ntnAccess,omitempty"`
 	Location                 models.UserLocation `json:"location,omitempty"`
 	Tai                      models.Tai          `json:"tai,omitempty"`
 	LocationChanged          bool                `json:"locationChanged,omitempty"`

context/ntn.go

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: 2026 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package context
+
+// NtnAccessInfo captures Non-Terrestrial Network access properties for a
+// UE, as derived from NGAP signaling. Only NTN-access presence is tracked
+// today; future 3GPP-defined fields (satelliteBackhaulCategory,
+// geoSatelliteId, NTN TAI list) can be added without reshaping AmfUe or
+// RanUe.
+type NtnAccessInfo struct {
+	// Detected reflects whether the most recent NR UserLocationInformation
+	// for this UE carried the NRNTN-TAI-Information extension. It is set
+	// and cleared on every NR location update.
+	Detected bool `json:"detected"`
+}
+
+// IsNtn reports whether the UE is currently being served over NTN access,
+// based on the most recent NR location update.
+func (ue *AmfUe) IsNtn() bool {
+	return ue.NtnAccess != nil && ue.NtnAccess.Detected
+}
+
+// updateNtnAccess records the current NTN-detection state on this RanUe.
+// It allocates the NtnAccessInfo container on first use and logs at Debug
+// only when the state actually transitions, to keep the per-update path
+// quiet for steady-state UEs.
+func (ranUe *RanUe) updateNtnAccess(detected bool) {
+	if ranUe.NtnAccess == nil {
+		ranUe.NtnAccess = &NtnAccessInfo{}
+	}
+	if ranUe.NtnAccess.Detected == detected {
+		return
+	}
+	ranUe.NtnAccess.Detected = detected
+	if detected {
+		ranUe.Log.Debugf("NR NTN access detected (NRNTN-TAI-Information extension present)")
+	} else {
+		ranUe.Log.Debugf("NR NTN access cleared (no NRNTN-TAI-Information extension)")
+	}
+}

context/ran_ue.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/mohae/deepcopy"
 	"github.com/omec-project/amf/logger"
+	"github.com/omec-project/ngap"
 	"github.com/omec-project/ngap/ngapConvert"
 	"github.com/omec-project/ngap/ngapType"
 	"github.com/omec-project/openapi/models"
@@ -46,8 +47,9 @@ type RanUe struct {
 	TargetUe            *RanUe  `json:"-"`
 
 	/* UserLocation*/
-	Tai      models.Tai
-	Location models.UserLocation
+	Tai       models.Tai
+	Location  models.UserLocation
+	NtnAccess *NtnAccessInfo `json:"-"`
 	/* context about udm */
 	SupportVoPSn3gpp  bool       `json:"-"`
 	SupportVoPS       bool       `json:"-"`
@@ -212,6 +214,8 @@ func (ranUe *RanUe) UpdateLocation(userLocationInformation *ngapType.UserLocatio
 			ranUe.Location.NrLocation = new(models.NrLocation)
 		}
 
+		ranUe.updateNtnAccess(ngap.HasUserLocationInformationNRExtension(locationInfoNR, ngapType.ProtocolIEIDNRNTNTAIInformation))
+
 		tAI := locationInfoNR.TAI
 		plmnID, err := ngapConvert.PlmnIdToModels(tAI.PLMNIdentity)
 		if err != nil {
@@ -250,6 +254,7 @@ func (ranUe *RanUe) UpdateLocation(userLocationInformation *ngapType.UserLocatio
 			}
 			ranUe.AmfUe.Location = deepcopy.Copy(ranUe.Location).(models.UserLocation)
 			ranUe.AmfUe.Tai = deepcopy.Copy(*ranUe.AmfUe.Location.NrLocation.Tai).(models.Tai)
+			ranUe.AmfUe.NtnAccess = deepcopy.Copy(ranUe.NtnAccess).(*NtnAccessInfo)
 		}
 	case ngapType.UserLocationInformationPresentUserLocationInformationN3IWF:
 		locationInfoN3IWF := userLocationInformation.UserLocationInformationN3IWF

context/ran_ue_test.go

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: 2026 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package context
+
+import (
+	"testing"
+
+	"go.uber.org/zap"
+)
+
+func TestRanUeUpdateNtnAccess(t *testing.T) {
+	tests := []struct {
+		name         string
+		initial      *NtnAccessInfo
+		detected     bool
+		wantDetected bool
+	}{
+		{name: "nil → not-detected allocates false", initial: nil, detected: false, wantDetected: false},
+		{name: "nil → detected allocates true", initial: nil, detected: true, wantDetected: true},
+		{name: "detected → detected stays true", initial: &NtnAccessInfo{Detected: true}, detected: true, wantDetected: true},
+		{name: "detected → not-detected clears", initial: &NtnAccessInfo{Detected: true}, detected: false, wantDetected: false},
+		{name: "not-detected → detected sets true", initial: &NtnAccessInfo{Detected: false}, detected: true, wantDetected: true},
+		{name: "not-detected → not-detected stays false", initial: &NtnAccessInfo{Detected: false}, detected: false, wantDetected: false},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ranUe := &RanUe{
+				NtnAccess: tc.initial,
+				Log:       zap.NewNop().Sugar(),
+			}
+			ranUe.updateNtnAccess(tc.detected)
+			if ranUe.NtnAccess == nil {
+				t.Fatalf("NtnAccess should always be non-nil after updateNtnAccess; got nil")
+			}
+			if ranUe.NtnAccess.Detected != tc.wantDetected {
+				t.Errorf("Detected = %v, want %v", ranUe.NtnAccess.Detected, tc.wantDetected)
+			}
+		})
+	}
+}