How to enable Samsung Galaxy S5/S4 for QXDM

Enable Developers option for USB debugging:
Go to Settings ->More->About Device and tap on the build number 3-5 times. It will notify that developer option is enabled.
Go back to Developers options and settings and Select USB debugging

Enables Modem Option on the Samsung Galaxy S5/S4:
Go to  Samsung Galaxy S5/S4 dialer and dial *#0808#. The USB Settings will opened.
Go to AP USB settings select the "RNDIS + DM + MODEM" and Click OK.

Connect the Samsung Galaxy S4/S5 to laptop and check the device manager. There must be a com port appear for your laptop. make note of the comm port and use it QPST and QXDM.

SRVCC - Subscribers VoLTE call will drop if out of VoLTE coverage?

SRVCC - Single Radio Voice Call Continuity

    Does the VoLTE call drop when out of VoLTE enabled cell coverage? Answer is Yes and a No. Potential solution is supporting SRVCC for call continuity with inter-RAT systems. SRVCC is adapted as standard but not something developed for VoLTE. SRVCC was designed to facilitate IMS Achored voice call continuity between LTE/HSPA network and GSM/UMTS/CDMA Networks.  This not as simple solution, since the voice call continuity is between Packet switch network and Circuit switched networks.

    Attach procedure is used to exchange the information about letting each other know SRVCC capability of UE and MME.  MSC-S, MME and UE needs to support SRVCC for the voice call continuity. Series of handover procedures carried out to move the voice leg from one RAT to another.

VoLTE - Voice over LTE - Must Know!

How will UE know that VoLTE is supported by the EPC network?

    During the NAS Attach procedure or NAS TAU procedure, in the Attach Accept and/or RAU Accept message, additional IE called "EPS Network Feature" will be included indicating "IMS Over PS session" is available. This triggers the UE to register with IMS network.

VoLTE Call Procedures - Call flow:

  In VoLTE call establishment procedure is achieved using a application server called Telephony Application Server(TAS).
Procedure includes:

• Establishment of Default EPS Bearer with  QCI = 5
• SIP Call Establishment Procedures
• Establishment of Dedicated EPS Bearer to support Media Bearer
• SIP Call Termination Procedures
• Termination of Dedicated EPS Bearer