TELEPHONY IN ANDROID
ANDROID'S TELEPHONY SYSTEM
ARCHITECTURE
Applications
Framework
Libraries
PhoneApp
Telephony
CallTracker
manager
Data
ServiceStateInternal
Connection
Tracke Telephony
Tracker
Ril Daemon
Package
Vendor Specific
RIL(.so)
Linux Kernel
Baseband/Cellular protocol
RADIO INTERFACE LAYER(RIL)


It is the bridge between Android phone framework services
and the hardware.
The RIL consists of two primary components:
 RIL Daemon: The RIL daemon initializes the Vendor
RIL, processes all communication from Android
telephony services, and dispatches calls to the Vendor
RIL as solicited commands.
 Vendor RIL: The radio-specific Vendor RIL that
processes all communication with radio hardware and
dispatches calls to the RIL Daemon (rild) through
unsolicited commands.
The line 1 is replace with 2 in init.rc to specify the vendor RIL lib that will be
loaded in the main method of rild.c
1. Service ril-daemon /system/bin/rild
2. Service ril-daemon /system/bin/rild -l /system/lib/libreference-ril.so
COMMUNICATION BETWEEN VARIOUS TELEPHONY
COMPONENTS
Communication between RIL and rild is
via commands (messages) over sockets
Rild
Vendor RIL
SOCKET
RIL
com.android.internal.t
elephony.RIL
Communication between vendor RIL
and baseband is via RPC
Baseband
RIL INTERACTION

There are two forms of communication that the RIL
handles:
 Solicited commands: Solicited commands originated by
RIL lib, such as DIAL and HANGUP.
 Unsolicited responses: Unsolicited responses that
originate from the baseband, such as
CALL_STATE_CHANGED and NEW_SMS.
logs
CALL STATES EXPOSED THROUGH THE
PHONESTATELISTENER
1.
2.
3.
IDLE
RINGING
OFFHOOK
NOTE: These states can also be viewed as Phone’s current states with respect to Call/Telephony
VARIOUS CALL STATES IMPLEMENTED
INTERNALLY
1.
2.
3.
4.
5.
6.
ACTIVE
HOLDING
DIALING
ALERTING
INCOMING
WAITING
TELEPHONYINTENTS

It defines intents that the telephony framework
can produce, some of them are:





ACTION_SERVICE_STATE_CHANGED: the phone
service state has changed.
ACTION_SIGNAL_STRENGTH_CHANGED: the
phone's signal strength has changed.
ACTION_ANY_DATA_CONNECTION_STATE_CHA
NGED: the data connection state has changed for any
one of the phone's mobile data connections.
ACTION_DATA_CONNECTION_FAILED: an
attempt to establish a data connection has failed.
ACTION_SIM_STATE_CHANGED: the SIM card
state has changed.
SOME IMPORTANT METHODS IN THE PHONE & SIM INTERFACES
AS WELL AS THE CALL ABSTRACT CLASSES.

The Phone interface has methods that are used to place, accept or reject a call:
public interface Phone {
Connection dial(String dialString) throws CallStateException;
void acceptCall() throws CallStateException;
void rejectCall() throws CallStateException;
void setMute(boolean muted);
void startDtmf(char c);
void sendDtmf(char c);
void stopDtmf();
...
}

A Call object is created when you answer a call, and the Call class methods implement call-related functionality
allowing you to, among other things, hang up: public interface Phone {
public abstract class Call {
public abstract void hangup() throws CallStateException;
public boolean isRinging()
public abstract boolean isIncoming();
...
}

Finally, the SimCard interface provides an access to a SIM card via methods that allow users to supply a PIN
(Personal Identification Number) and a PUK (Personal Unblocking Key), which is used to unblock the PIN:
public interface SimCard {
void supplyPin(String pin, Message onComplete);
void supplyPuk(String puk, String newPin, Message onComplete);
void supplyPin2(String pin2, Message onComplete);
void supplyPuk2(String puk2, String newPin2, Message onComplete);
State getState();
...
}
& OPEN TELEPHONY WITH PHONEAPP AND
ANY 3RD PARTY APP
PhoneFactory
PhoneProxy
ITelephony
TelephonyManag
er
ITelephonyRegistry
TelephonyRegistry
GSM/CDMA Phone
mC
M
RIL.java
Broadcast
3rd Paty App
PhoneInterfaceManager
PhoneStateListener
PhoneApp
Socket
Ril-daemon
*Internal Telephony Package: com.android.internal.telephony
*Open Telephony Package: android.telephony
RELATION BETWEEN FEW IMPORTANT
CLASSES
Phone
CommandInterfac
e
PhoneBase
BaseCommands
GSMPhone
CDMAPhon
e
RIL
PhoneProxy