Mobile Communication Overview for beginners.


What is Mobile Communication ?

Differences of LTE Networks vs 3G Vs 2G Cellular Network:

Features                LTE Network    3G Network          2G Network

Handset                              UE                            UE                             MS
Redio Elements                eNode B             Node B+ RNC           BTS_BSC
Core Elements                    NIL                 MSS & MGW          MSC or MSS & MGW
Packet Core Elements     MME+S-GW     SGSN_GGSN       SGSN_GGSN
 Database of N/W             HSS                    HLR & VLR or HSS      HLR+VLR

UE:-User Equipment
MS:-Mobile Station
mobile communication and LTE Architecture
LTE-Architecture

Role of Evolved Node B(eNB)

1.Radio Resource Management Function(RRM).

  • Radio Bearer Control.
  • Radio Admission Control.
  • Connection Mobility Control.
  • Dynamic Resource Allocation. UL & DL.

2.IP Header Compression and Encryption of user data

  • Selection of MME at UE attachment.
  • Measurement  for Mobility.

3.Scheduling and Transmission of Paging and Broadcast.

Role of X2 Interface

1.Newly introduced E-UTRAN interface.

  • Inter eNB interface.

X2 Interface Main Function:-

  • Provisioning of inter eNB direct connection.
  • Handover(HO) coordination without EPC involvement.
  • By reducing delay and packet loss ratio we improved HO performance.
  • Load balancing
  • Exchange of Load indicator(LI) messages between eNB to adjust RRM parameters and /or manage inter cell interface cancellation.

Role of LTE UE(User Equipment)

LTE User Equipment is used by an end-user to communicate with the LTE network.It can be a hand-held mobile,a USB dongle or any Other devices to connect to the nearest eNB is called Uu.

UE is mainly responsible for following Function.

  • Mobility Management.
  • Call Control.
  • Session Management.
  • Identity Management.

Role of S6-a Interface

Main Function of S6-a Interface

  • Communication of Authentication data.
  • Deletion and Updation of Subscriber data.

Role of S1-MME Interface

Support control between S1 and MME

Role of MME(Mobility Management Entity):

Control plane network element in EPC.
Used For
  • Authentication
  • Integrity Protection
  • Tracking area updates.
  • Subscriber attach and detach.
  • Signaling coordination for SAE Bearer setup or release
  • Radio security control.
  • The distribution of Paging message to eNB.
  • Roaming control node signaling.
  • Inter-cn node signaling allows efficient inter-MME tracking area updates and attaches.

Role of S11 Interface

Main Function of S11 Interface
  • Transfer bearer level quality of service(QoS) parameter values to MME.There values are gradually passed over to E-UTRAN Transparently.

Role of S1-U Interface

  • SAE bearer user plane funneling.
  • Supports inter eNodeB path switching during Handover.

Role of S-GW (Serving SAE Gateway)

  • In case of Handover Local mobility anchor point of Switching the user plane path to a new eNB. 
  • Mobility anchoring for inter-3GPP anchor function.
  • In Idle case packet buffering and notification to MME.
  • Packet routing /forwarding between eNB P-GW and SGSN.
  • Lawful interception support.

Role of S5/S8 Interface

  • This interface is used by S5/S8 bearer to transport the Packet of EPS bearer  between a P-GW and S-GW.

Role of P-GW(Packet data network SAEGateway)

  • Mobility ticker for mobility between 3GPP ingress systems and non-3GPP reach system.This is formerly indicated to as the SAE anchor function.
    • policy Enforcement(PCEF).
  • Per user based Packet filtering.
  • Charging and lawful interception support.
  • IP address Allocation for UE.

Role of SGi Interface

  • Provides connectivity between PDN Gateway and IMS.
  • IMS(Internet Protocol Multimedia Subsystem) is an architecture framwork designed for delivering IP multimedia  services like voice and video via UMTS ,LTE network.

Role of Gx Inteface

This inteface provides connectivity between PDN gateway and PCRF.

Role of PCRF(Policy and Charging Role Function)

  • Policy and charging role function provides flow based policy and charging control decisions.
  • Policy and charging Enforcement functio  enforce geting and QoS control on behalf of the PCRF.
  • Bearer binding  and event reporting function binds flows to IP bearer and reports events.
  • Subscriber profile respository  stores subscriber profiles.
  • Application function represent applications that requie dynamic policy and QoS control.

Role of Rx Interface

This Interface connects PCRF to IMS

Role of HSS(Home Subscriber Server)

  • Permanent and central subscriber database.
  • Store mobility and service data for every Subscriber.
  • Contains the Authentication center.
e-UMTRAN:-Enhanced-Universal Mobile Terrestrial Radio Access Network.
PDN:-Public Data Network.

Question related to LTE Network:-

  1. Base Station in LTE   is Called as.  eNodeB
  2. IP assignment is done by which NE?  P-GW
  3. Which interface connects UE with eNodeB? Uu
  4. The interface between eNB and eNB is. X2

Summary:-

  • Basic differnece in terms of network architecture between LTE,UMTS and 2G system.
  • Known about All the Network and Interfaces of LTE Network architecture.

Mobile Communication GSM Network

2G/3G Call Flow From Subscriber A to Subscrier B

Mobile communication Architecture Call Setup
2G 3G Network Architecture for Call Flow

Call Setup Process:-


  1. Subscriber A dail the MSISDN of Subscriber B(35860220002).
  2. The Signalling Connection is established upto MSC-1.
  3. MSC-1 receives the dailled number and perform a pre-analysis in order to find out the type of the call (digital analysis,HLR enquiry).
  4. HLR Enquiry The IMSI and VLR address of the Subscriber B are found from the HLR data base. (MS ISDN, IMSI ,VLR address).
  5. The HLR request a roaming number from the MSC-2(MSRN request from IMSI)
  6. The MSC-2 reserve a roaming number from the roaming number pool(MSNR Pool,MSRN,IMSI).
  7. The MSC-2 gives the reserved MSRN to HLR which forwards it to the MSC-1 the roaming number identifies the location of the Subscriber B.
  8. MSC-2 receives the MSRN from the MSC-1.The roaming number identifies its source(MSC-2)so this is the end point of the routing process now the MSC-2 check for which IMSI the roaming number was reserved.
  9. Now the MSC-2 checks the location are and the TMSI of the subscriber B from the VLR.
  10. When the Subscriber B TMSI and LAC are found the MSC-2 start Paging.(VLR data base,MSISDN ,IMSI,LAC,TMSI).
  11. Here is a call for TIMSI xxxxxxx(Call setup is completed) after the MS-B answer speech connection is established and MS-B start ringing.





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