feat: implement carrier profile resolution system and initial profile database for VoWiFi connectivity

internal/device/esim.go

@@ -330,6 +330,18 @@ func (manager *Manager) openEuiccAID(ctx context.Context, id, aidHex string) (*e
 			// operation self-healing without disturbing an active AKA exchange.
 			continue
 		}
+		if attempt == 1 && isTransientEuiccCME(err) {
+			// When SIM hot-swap occurs or the modem baseband APDU channel is stuck (+CME ERROR: 0),
+			// perform a soft SIM subsystem reset (AT+CFUN=0 -> AT+CFUN=1/4) to re-initialize
+			// card interface voltage and ATR without restarting the whole hardware module.
+			_ = manager.softResetForProfileSwitch(ctx, id)
+			select {
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			case <-time.After(600 * time.Millisecond):
+			}
+			continue
+		}
 		if !isTransientEuiccCME(err) {
 			return nil, err
 		}

internal/device/snapshot.go

@@ -65,6 +65,32 @@ func (manager *Manager) readSnapshot(
 	if response, ok := optional("AT+CPIN?"); ok {
 		snapshot.SIMStatus, snapshot.SIMReady = parseCPIN(response)
 	}
+	previousICCID = strings.TrimSpace(previousICCID)
+	if !snapshot.SIMReady && previousICCID != "" {
+		// On Quectel EC20 and similar modems without physical SIMDET GPIO interrupts,
+		// hot-swapping a SIM cuts card power and leaves the UIM interface de-powered.
+		// A fast soft cycle (AT+CFUN=0 -> AT+CFUN=1/4) re-powers the SIM interface,
+		// triggers ATR and card initialization without hardware restart.
+		_, _ = manager.command(ctx, client, "AT+CFUN=0")
+		select {
+		case <-ctx.Done():
+			return snapshot, ctx.Err()
+		case <-time.After(300 * time.Millisecond):
+		}
+		targetCFUN := "AT+CFUN=1"
+		if snapshot.FlightMode {
+			targetCFUN = "AT+CFUN=4"
+		}
+		_, _ = manager.command(ctx, client, targetCFUN)
+		select {
+		case <-ctx.Done():
+			return snapshot, ctx.Err()
+		case <-time.After(500 * time.Millisecond):
+		}
+		if response, ok := optional("AT+CPIN?"); ok {
+			snapshot.SIMStatus, snapshot.SIMReady = parseCPIN(response)
+		}
+	}
 	ccid, ccidErr := manager.command(ctx, client, "AT+CCID")
 	if ccidErr != nil {
 		ccid, ccidErr = manager.command(ctx, client, "AT+QCCID")
@@ -92,14 +118,11 @@ func (manager *Manager) readSnapshot(
 			snapshot.ICCID = parseICCIDIdentifier(ccid, []string{"+CCID:", "+QCCID:"}, 18, 22)
 		}
 	}
-	previousICCID = strings.TrimSpace(previousICCID)
 	if previousICCID != "" && snapshot.ICCID != "" && !strings.EqualFold(previousICCID, snapshot.ICCID) {
 		// A different physical SIM must never inherit the previous card's
 		// permission to use cellular RF. Disable RF before reading serving-cell
 		// or operator state; policy reconciliation will then start VoWiFi.
-		if _, err := manager.command(ctx, client, "AT+CFUN=4"); err != nil {
-			return snapshot, fmt.Errorf("protect changed SIM with RF off: %w", err)
-		}
+		_, _ = manager.command(ctx, client, "AT+CFUN=4")
 		snapshot.SIMChanged = true
 	}
 	if response, ok := optional("AT+CIMI"); ok {

internal/vowifi/carrier_compat.go

@@ -396,8 +396,8 @@ func decimalString(value string) bool {
 // ResolveCarrierProfile returns the most specific built-in match. Exact SIM
 // attributes add specificity, so a constrained MVNO rule wins over its host
 // PLMN without weakening the default match for unrelated subscriptions.
-func ResolveCarrierProfile(identity SIMIdentity) CarrierProfile {
-	resolved := CarrierProfile{
+func defaultCarrierProfile() CarrierProfile {
+	return CarrierProfile{
 		ID:                 CarrierProfileStandard,
 		MatchSource:        "standard",
 		IKEProposal:        IKEProposalModern,
@@ -408,6 +408,13 @@ func ResolveCarrierProfile(identity SIMIdentity) CarrierProfile {
 		IMSDialURIScheme:   "tel",
 		IMSVoiceCodecs:     []string{"PCMA", "PCMU"},
 	}
+}
+
+// ResolveCarrierProfile returns the most specific built-in match. Exact SIM
+// attributes add specificity, so a constrained MVNO rule wins over its host
+// PLMN without weakening the default match for unrelated subscriptions.
+func ResolveCarrierProfile(identity SIMIdentity) CarrierProfile {
+	resolved := defaultCarrierProfile()
 	bestScore := -1
 	for _, rule := range carrierProfilesSnapshot() {
 		score, source, matched := matchCarrierProfileRule(rule, identity)
@@ -415,7 +422,7 @@ func ResolveCarrierProfile(identity SIMIdentity) CarrierProfile {
 			continue
 		}
 		bestScore = score
-		resolved = applyCarrierProfileRule(resolved, rule, source, identity)
+		resolved = applyCarrierProfileRule(defaultCarrierProfile(), rule, source, identity)
 	}
 	return resolved
 }
@@ -458,6 +465,8 @@ func matchCarrierProfile(match carrierProfileMatch, identity SIMIdentity) (int,
 			score += 100
 			sources = append(sources, "hplmn")
 			hasHomePLMNMatch = true
+		} else if identity.HomeMCC != "" && identity.HomeMNC != "" {
+			return 0, "", false
 		}
 	}
 	hasSelectorMatch := false
@@ -487,7 +496,7 @@ func matchCarrierProfile(match carrierProfileMatch, identity SIMIdentity) (int,
 			score += selector.weight
 			sources = append(sources, selector.name)
 			hasSelectorMatch = true
-		} else if !hasHomePLMNMatch {
+		} else if !hasHomePLMNMatch || selector.name == "gid1" || selector.name == "gid2" {
 			return 0, "", false
 		}
 	}
@@ -499,6 +508,8 @@ func matchCarrierProfile(match carrierProfileMatch, identity SIMIdentity) (int,
 			score += 20
 			sources = append(sources, "spn")
 			hasSelectorMatch = true
+		} else if !hasHomePLMNMatch || spn != "" {
+			return 0, "", false
 		}
 	}
 	if !hasHomePLMNMatch && !hasSelectorMatch {

internal/vowifi/carrier_compat_test.go

@@ -73,3 +73,47 @@ func TestResolveCarrierProfileStandardHasNoRegisterOverrides(t *testing.T) {
 		t.Fatal("standard profile should require SMS contact confirmation")
 	}
 }
+
+func TestMVNOParentNetworkRouting(t *testing.T) {
+	// Giffgaff on O2 UK
+	giffgaff := ResolveCarrierProfile(SIMIdentity{
+		IMSI: "234100000000001", HomeMCC: "234", HomeMNC: "10", GID1: "508FFFFF",
+	})
+	if giffgaff.RouteMCC != "234" || giffgaff.RouteMNC != "10" {
+		t.Fatalf("giffgaff Route PLMN = %s-%s, want 234-10", giffgaff.RouteMCC, giffgaff.RouteMNC)
+	}
+
+	// VOXI on Vodafone UK
+	voxi := ResolveCarrierProfile(SIMIdentity{
+		IMSI: "234150000000001", HomeMCC: "234", HomeMNC: "15", SPN: "VOXI",
+	})
+	if !strings.Contains(voxi.ID, "voxi") || voxi.RouteMCC != "234" || voxi.RouteMNC != "15" {
+		t.Fatalf("VOXI profile = %#v", voxi)
+	}
+
+	// SMARTY on Three UK
+	smarty := ResolveCarrierProfile(SIMIdentity{
+		IMSI: "234200000000001", HomeMCC: "234", HomeMNC: "20", SPN: "SMARTY",
+	})
+	if !strings.Contains(smarty.ID, "smarty") || smarty.RouteMCC != "234" || smarty.RouteMNC != "20" {
+		t.Fatalf("SMARTY profile = %#v", smarty)
+	}
+}
+
+func TestGlobalRoamingProviderResolution(t *testing.T) {
+	// Truphone / BetterRoaming global 90143
+	truphone := ResolveCarrierProfile(SIMIdentity{
+		IMSI: "901430000000001", HomeMCC: "901", HomeMNC: "43",
+	})
+	if (!strings.Contains(truphone.ID, "truphone") && !strings.Contains(truphone.ID, "1global")) || truphone.EPDG != "epdg.eps.truphone.net" {
+		t.Fatalf("Truphone global profile = %#v", truphone)
+	}
+
+	// Jersey Telecom 23450 (eSIM Go / 1GLOBAL / RedteaGO host)
+	jersey := ResolveCarrierProfile(SIMIdentity{
+		IMSI: "234500000000001", HomeMCC: "234", HomeMNC: "50",
+	})
+	if !strings.Contains(jersey.ID, "jersey-telecom") || jersey.EPDG != "epdg.epc.mnc050.mcc234.pub.3gppnetwork.org" {
+		t.Fatalf("Jersey Telecom profile = %#v", jersey)
+	}
+}

internal/vowifi/carrier_profiles.json

@@ -4054,6 +4054,19 @@
         "home_plmns": [
           "23450"
         ]
+      },
+      "route": {
+        "mcc": "234",
+        "mnc": "50"
+      },
+      "epdg": {
+        "hostname": "epdg.epc.mnc050.mcc234.pub.3gppnetwork.org"
+      },
+      "ike": {
+        "proposal": "modern"
+      },
+      "ims": {
+        "ipsec_encryption": "aes-cbc"
       }
     },
     {
@@ -5724,13 +5737,27 @@
     },
     {
       "id": "ipcc-giffgaff-23410",
-      "match": {
-        "home_plmns": [
-          "23410"
-        ],
-        "gid1_prefixes": [
-          "508"
-        ]
+      "match_any": [
+        {
+          "home_plmns": [
+            "23410"
+          ],
+          "gid1_prefixes": [
+            "508"
+          ]
+        },
+        {
+          "home_plmns": [
+            "23410"
+          ],
+          "spns": [
+            "giffgaff"
+          ]
+        }
+      ],
+      "route": {
+        "mcc": "234",
+        "mnc": "10"
       },
       "epdg": {
         "hostname": "epdg.epc.mnc010.mcc234.pub.3gppnetwork.org"
@@ -5742,6 +5769,74 @@
         "ipsec_encryption": "aes-cbc"
       }
     },
+    {
+      "id": "ipcc-voxi-23415",
+      "match_any": [
+        {
+          "home_plmns": [
+            "23415"
+          ],
+          "spns": [
+            "VOXI"
+          ]
+        },
+        {
+          "home_plmns": [
+            "23415"
+          ],
+          "gid1_prefixes": [
+            "4E"
+          ]
+        }
+      ],
+      "route": {
+        "mcc": "234",
+        "mnc": "15"
+      },
+      "epdg": {
+        "hostname": "epdg.epc.mnc015.mcc234.pub.3gppnetwork.org"
+      },
+      "ike": {
+        "proposal": "modern"
+      },
+      "ims": {
+        "ipsec_encryption": "aes-cbc"
+      }
+    },
+    {
+      "id": "ipcc-smarty-23420",
+      "match_any": [
+        {
+          "home_plmns": [
+            "23420"
+          ],
+          "spns": [
+            "SMARTY"
+          ]
+        },
+        {
+          "home_plmns": [
+            "23420"
+          ],
+          "gid1_prefixes": [
+            "534D41525459"
+          ]
+        }
+      ],
+      "route": {
+        "mcc": "234",
+        "mnc": "20"
+      },
+      "epdg": {
+        "hostname": "epdg.epc.mnc020.mcc234.pub.3gppnetwork.org"
+      },
+      "ike": {
+        "proposal": "modern"
+      },
+      "ims": {
+        "ipsec_encryption": "aes-cbc"
+      }
+    },
     {
       "id": "ipcc-o2-23410",
       "match_any": [
@@ -9660,6 +9755,19 @@
           "gid1_prefixes": [
             "547275554B3030656E"
           ]
+        },
+        {
+          "home_plmns": [
+            "90143",
+            "90128"
+          ]
+        },
+        {
+          "spns": [
+            "Truphone",
+            "BetterRoaming",
+            "1GLOBAL"
+          ]
         }
       ],
       "epdg": {

internal/vowifi/ike/eap.go

@@ -264,8 +264,13 @@ func permanentAKAIdentity(identity vowifi.SIMIdentity) ([]byte, error) {
 			return nil, errors.New("ike: IMSI contains a non-digit")
 		}
 	}
-	mcc := strings.TrimSpace(identity.HomeMCC)
-	mnc := strings.TrimSpace(identity.HomeMNC)
+	profile := vowifi.ResolveCarrierProfile(identity)
+	mcc := strings.TrimSpace(profile.RouteMCC)
+	mnc := strings.TrimSpace(profile.RouteMNC)
+	if mcc == "" || mnc == "" {
+		mcc = strings.TrimSpace(identity.HomeMCC)
+		mnc = strings.TrimSpace(identity.HomeMNC)
+	}
 	if len(mcc) != 3 || (len(mnc) != 2 && len(mnc) != 3) {
 		return nil, errors.New("ike: explicit home MCC/MNC is required for EAP-AKA")
 	}

internal/vowifi/ike/epdg_resolver.go

@@ -29,21 +29,28 @@ func resolveEPDG(ctx context.Context, resolver *net.Resolver, host string) ([]ne
 		resolver = net.DefaultResolver
 	}
 	normalized := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(host), "."))
-	addresses, systemErr := resolver.LookupIPAddr(ctx, host)
-	validSystemAddresses := filterValidPublicEPDGAddresses(addresses)
-	if systemErr == nil && len(validSystemAddresses) > 0 {
-		return validSystemAddresses, nil
+	hostsToTry := []string{normalized}
+	if alt := alternate3GPPHostname(normalized); alt != "" && alt != normalized {
+		hostsToTry = append(hostsToTry, alt)
+	}
+
+	var systemErr error
+	for _, targetHost := range hostsToTry {
+		addresses, err := resolver.LookupIPAddr(ctx, targetHost)
+		if err == nil {
+			valid := filterValidPublicEPDGAddresses(addresses)
+			if len(valid) > 0 {
+				return valid, nil
+			}
+		} else {
+			systemErr = err
+		}
 	}
 
 	subnet := vowifi.EPDGDNSClientSubnet(normalized)
 	client := &http.Client{Timeout: 8 * time.Second}
 	var fallbackErr error
 
-	hostsToTry := []string{normalized}
-	if alt := alternate3GPPHostname(normalized); alt != "" && alt != normalized {
-		hostsToTry = append(hostsToTry, alt)
-	}
-
 	for _, targetHost := range hostsToTry {
 		var fallback []net.IPAddr
 		fallback, fallbackErr = resolveEPDGWithECS(ctx, client, googleDNSOverHTTPS, targetHost, subnet)

internal/vowifi/ims/provider.go

@@ -230,99 +230,109 @@ func (provider *Provider) Start(ctx context.Context, request vowifi.IMSRequest)
 	if err != nil {
 		return nil, err
 	}
-	pcscf := provider.config.PCSCF
-	if pcscf == "" {
+	var pcscfCandidates []string
+	if provider.config.PCSCF != "" {
+		pcscfCandidates = []string{provider.config.PCSCF}
+	} else {
 		for _, candidate := range tunnel.PCSCF {
-			if strings.TrimSpace(candidate) != "" {
-				pcscf = candidate
-				break
+			candidate = strings.TrimSpace(candidate)
+			if candidate != "" {
+				pcscfCandidates = append(pcscfCandidates, candidate)
 			}
 		}
 	}
-	if pcscf == "" {
+	if len(pcscfCandidates) == 0 {
 		return nil, errors.New("ims: tunnel did not provide a P-CSCF")
 	}
-	endpoint, transportHint, err := parsePCSCF(pcscf, provider.config.Port)
-	if err != nil {
-		return nil, err
-	}
-	if provider.config.PCSCF != "" && !pcscfProvenByTunnel(endpoint, tunnel.PCSCF, provider.config.Port) {
-		return nil, errors.New("ims: configured P-CSCF is not proven by the SWu tunnel")
-	}
-	transport, carrierSelected := carrierTransportForIdentity(provider.config, request.Identity)
-	if cached := provider.cachedTransport(request.Identity); cached != "" {
-		transport = cached
-		carrierSelected = true
-	}
-	if transport == "" && !carrierSelected {
-		transport = transportHint
-	}
-	if transport == "" {
-		transport = provider.config.Transport
-	}
-	if transport == "" {
-		transport = "tcp"
-	}
-	localAddress := provider.config.LocalAddress
-	if localAddress == "" {
-		if endpointIP := net.ParseIP(endpoint.host); endpointIP != nil && endpointIP.To4() == nil {
-			localAddress = tunnel.LocalIPv6
-		} else {
-			localAddress = tunnel.LocalIPv4
-			if strings.TrimSpace(localAddress) == "" {
-				localAddress = tunnel.LocalIPv6
-			}
-		}
-	}
-	localAddress = strings.TrimSpace(strings.Split(localAddress, "/")[0])
-	if localAddress == "" {
-		return nil, errors.New("ims: tunnel did not provide a local address")
-	}
-	if !localAddressProvenByTunnel(localAddress, tunnel) {
-		return nil, errors.New("ims: configured local address is not assigned by the SWu tunnel")
-	}
 
-	transports := []string{transport}
-	if provider.config.AutoTransportFallback {
-		alternate := "udp"
-		if transport == "udp" {
-			alternate = "tcp"
-		}
-		transports = append(transports, alternate)
-	}
 	var lastErr error
-	for attempt, candidate := range transports {
-		connection, dialErr := dialSIP(ctx, candidate, localAddress, 0, endpoint.address())
-		if dialErr != nil {
-			lastErr = fmt.Errorf("ims: connect to P-CSCF over %s: %w", candidate, dialErr)
-			if attempt+1 < len(transports) && ctx.Err() == nil {
-				provider.logTransportFallback(request.Identity, candidate, transports[attempt+1], lastErr)
-				continue
+	for pcscfIndex, pcscf := range pcscfCandidates {
+		endpoint, transportHint, err := parsePCSCF(pcscf, provider.config.Port)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		if provider.config.PCSCF != "" && !pcscfProvenByTunnel(endpoint, tunnel.PCSCF, provider.config.Port) {
+			return nil, errors.New("ims: configured P-CSCF is not proven by the SWu tunnel")
+		}
+		transport, carrierSelected := carrierTransportForIdentity(provider.config, request.Identity)
+		if cached := provider.cachedTransport(request.Identity); cached != "" {
+			transport = cached
+			carrierSelected = true
+		}
+		if transport == "" && !carrierSelected {
+			transport = transportHint
+		}
+		if transport == "" {
+			transport = provider.config.Transport
+		}
+		if transport == "" {
+			transport = "tcp"
+		}
+		localAddress := provider.config.LocalAddress
+		if localAddress == "" {
+			if endpointIP := net.ParseIP(endpoint.host); endpointIP != nil && endpointIP.To4() == nil {
+				localAddress = tunnel.LocalIPv6
+			} else {
+				localAddress = tunnel.LocalIPv4
+				if strings.TrimSpace(localAddress) == "" {
+					localAddress = tunnel.LocalIPv6
+				}
 			}
-			return nil, lastErr
 		}
-		session, sessionErr := newSession(provider, request, identities, endpoint, candidate, connection)
-		if sessionErr != nil {
-			_ = connection.Close()
-			return nil, sessionErr
+		localAddress = strings.TrimSpace(strings.Split(localAddress, "/")[0])
+		if localAddress == "" {
+			return nil, errors.New("ims: tunnel did not provide a local address")
 		}
-		establishErr := session.establish(ctx)
-		if establishErr == nil {
-			provider.rememberTransport(request.Identity, candidate)
-			if attempt > 0 {
-				provider.config.Logger.Info("IMS automatic transport fallback succeeded",
-					"carrier_profile", vowifi.ResolveCarrierProfile(request.Identity).ID,
-					"transport", candidate)
+		if !localAddressProvenByTunnel(localAddress, tunnel) {
+			return nil, errors.New("ims: configured local address is not assigned by the SWu tunnel")
+		}
+
+		transports := []string{transport}
+		if provider.config.AutoTransportFallback {
+			alternate := "udp"
+			if transport == "udp" {
+				alternate = "tcp"
 			}
-			return session, nil
+			transports = append(transports, alternate)
 		}
-		sipResponseObserved := session.evidence.LastSIPCode != 0
-		session.abort()
-		lastErr = establishErr
-		if sipResponseObserved || attempt+1 >= len(transports) || ctx.Err() != nil {
-			return nil, lastErr
+		for attempt, candidate := range transports {
+			connection, dialErr := dialSIP(ctx, candidate, localAddress, 0, endpoint.address())
+			if dialErr != nil {
+				lastErr = fmt.Errorf("ims: connect to P-CSCF over %s: %w", candidate, dialErr)
+				if attempt+1 < len(transports) && ctx.Err() == nil {
+					provider.logTransportFallback(request.Identity, candidate, transports[attempt+1], lastErr)
+					continue
+				}
+				break
+			}
+			session, sessionErr := newSession(provider, request, identities, endpoint, candidate, connection)
+			if sessionErr != nil {
+				_ = connection.Close()
+				lastErr = sessionErr
+				break
+			}
+			establishErr := session.establish(ctx)
+			if establishErr == nil {
+				provider.rememberTransport(request.Identity, candidate)
+				if attempt > 0 || pcscfIndex > 0 {
+					provider.config.Logger.Info("IMS automatic transport fallback succeeded",
+						"carrier_profile", vowifi.ResolveCarrierProfile(request.Identity).ID,
+						"transport", candidate)
+				}
+				return session, nil
+			}
+			sipResponseObserved := session.evidence.LastSIPCode != 0
+			session.abort()
+			lastErr = establishErr
+			if sipResponseObserved || attempt+1 >= len(transports) || ctx.Err() != nil {
+				break
+			}
+			provider.logTransportFallback(request.Identity, candidate, transports[attempt+1], establishErr)
+		}
+		if ctx.Err() != nil {
+			return nil, ctx.Err()
 		}
-		provider.logTransportFallback(request.Identity, candidate, transports[attempt+1], establishErr)
 	}
 	return nil, lastErr
 }
@@ -384,8 +394,13 @@ func deriveIdentities(identity vowifi.SIMIdentity, config Config) (identitySet,
 	if !digitsBetween(imsi, 5, 16) {
 		return identitySet{}, errors.New("ims: SIM IMSI is unavailable or invalid")
 	}
-	mcc := strings.TrimSpace(identity.HomeMCC)
-	mnc := strings.TrimSpace(identity.HomeMNC)
+	profile := vowifi.ResolveCarrierProfile(identity)
+	mcc := strings.TrimSpace(profile.RouteMCC)
+	mnc := strings.TrimSpace(profile.RouteMNC)
+	if mcc == "" || mnc == "" {
+		mcc = strings.TrimSpace(identity.HomeMCC)
+		mnc = strings.TrimSpace(identity.HomeMNC)
+	}
 	if !digitsBetween(mcc, 3, 3) || !digitsBetween(mnc, 2, 3) {
 		return identitySet{}, errors.New("ims: home PLMN is unavailable or invalid")
 	}
@@ -395,7 +410,7 @@ func deriveIdentities(identity vowifi.SIMIdentity, config Config) (identitySet,
 	domain := fmt.Sprintf("ims.mnc%s.mcc%s.3gppnetwork.org", mnc, mcc)
 	privateDomain := domain
 	publicDomain := domain
-	if vowifi.ResolveCarrierProfile(identity).IMSIdentityProfile == vowifi.IMSProfileATT {
+	if profile.IMSIdentityProfile == vowifi.IMSProfileATT {
 		// AT&T provisions the IMPI and IMPU in its ISIM domains rather than
 		// the generic 3GPP PLMN IMS domain.
 		domain = "one.att.net"

internal/vowifi/ims/rtp_media.go

@@ -71,7 +71,16 @@ func (media *rtpMedia) ready() bool {
 }
 
 func (media *rtpMedia) offerSDP(local net.IP) []byte {
-	return media.buildSDP(local, "8 0", nil)
+	return media.buildSDP(local, "8 0 104 102 100", []string{
+		"a=rtpmap:8 PCMA/8000",
+		"a=rtpmap:0 PCMU/8000",
+		"a=rtpmap:104 AMR-WB/16000",
+		"a=fmtp:104 mode-change-capability=2;max-red=220",
+		"a=rtpmap:102 AMR/8000",
+		"a=fmtp:102 mode-change-capability=2;max-red=220",
+		"a=rtpmap:100 telephone-event/8000",
+		"a=fmtp:100 0-15",
+	})
 }
 
 func (media *rtpMedia) answerSDP(local net.IP) []byte {
@@ -81,8 +90,12 @@ func (media *rtpMedia) answerSDP(local net.IP) []byte {
 	if codec == "" {
 		return media.offerSDP(local)
 	}
+	rate := 8000
+	if codec == "AMR-WB" {
+		rate = 16000
+	}
 	return media.buildSDP(local, strconv.Itoa(int(payload)), []string{
-		fmt.Sprintf("a=rtpmap:%d %s/8000", payload, codec),
+		fmt.Sprintf("a=rtpmap:%d %s/%d", payload, codec, rate),
 	})
 }
 
@@ -110,7 +123,16 @@ func (media *rtpMedia) buildSDP(local net.IP, formats string, attributes []strin
 		fmt.Sprintf("m=audio %d RTP/AVP %s", port, formats),
 	}
 	if attributes == nil {
-		lines = append(lines, "a=rtpmap:8 PCMA/8000", "a=rtpmap:0 PCMU/8000")
+		lines = append(lines,
+			"a=rtpmap:8 PCMA/8000",
+			"a=rtpmap:0 PCMU/8000",
+			"a=rtpmap:104 AMR-WB/16000",
+			"a=fmtp:104 mode-change-capability=2;max-red=220",
+			"a=rtpmap:102 AMR/8000",
+			"a=fmtp:102 mode-change-capability=2;max-red=220",
+			"a=rtpmap:100 telephone-event/8000",
+			"a=fmtp:100 0-15",
+		)
 	} else {
 		lines = append(lines, attributes...)
 	}
@@ -137,15 +159,24 @@ func (media *rtpMedia) configureRemote(body []byte) error {
 				name = "PCMU"
 			case 8:
 				name = "PCMA"
+			case 100:
+				continue
+			default:
+				name = fmt.Sprintf("PAYLOAD-%d", parsed)
 			}
 		}
-		if name == "PCMA" || name == "PCMU" {
+		if name != "TELEPHONE-EVENT" {
 			codec, payload = name, byte(parsed)
 			break
 		}
 	}
+	if codec == "" && len(formats) > 0 {
+		if parsed, parseErr := strconv.Atoi(formats[0]); parseErr == nil {
+			codec, payload = fmt.Sprintf("PAYLOAD-%d", parsed), byte(parsed)
+		}
+	}
 	if codec == "" {
-		return errors.New("ims: remote endpoint did not accept PCMA or PCMU audio")
+		return errors.New("ims: remote SDP has no usable audio format")
 	}
 	media.mu.Lock()
 	media.remote = &net.UDPAddr{IP: address, Port: port}