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LTE - end-to-end data flow UE

LTE - end-to-end data flow UE [Under LTE]
» E-UTRA and E-UTRAN overall description - 36.300, Rel 8 «
» E-UTRAN access - 23.401, Rel 8 «

Below diagram describe protocols involved in end-to-end data flow, starting at UE application till PGW:

Application
TCP/UDP/IP
Adaptor
PDCP
RLC
MAC
PHY
Relay
PDCP GTP-U
RLC UDP/IP
MAC L2
PHY L1
Relay
GTP-U
UDP/IP
L2
L1

Relay
  IP  
GTP-U
UDP/IP
L2 L2
L1 L1


  IP  

L2
L1
UE DRBs
(RRC DRB identity,
MAC LCID)
eNB S1 bearers
(E-RAB ID,
GTP TEID)
SGW S5/S8 bearers
(EPS bearer ID,
GTP TEID)
PGW PDN transport
(PDN address)
PDN

Below diagram shows how data flows at UE:

 UE App stack 
Application (HTTP, FTP, RTP, SIP, IMAP, RPC etc.)
Protocol specific operations

Application data 

  .  .  . 

Ports/Sockets
TCP/UDP
TCP: IETF rfc793, segmentation, sequence numbering, checksum, UDP: IETF rfc768

TCP/UDP header  Application data (segments) 

  .  .  . 


IP
v4 IETF rfc791, v6 IETF rfc2460, fragmentation & reassembly, addressing

IP header  Data (fragments) 

  .  .  . 

Data pipes
Data plane stack adaptor
Implementation specific (mainly buffering), UL TFT based IP packet filtering

Data 

  .  .  . 

Data radio bearers
 UE Wireless stack 
PDCP
3GPP TS 36.323, TCP/UDP/IP header compression/decompression, sequence numbering, ciphering/deciphering

PDCP header  SDU 

  .  .  . 


RLC
3GPP TS 36.322, buffering, segmentation, concatenation, reassembly, ARQ

RLC header  SDU 

  .  .  . 

Logical channels (DTCH)
MAC
3GPP TS 36.321, channel mapping, multiplexing, channel prioritisation, HARQ

MAC header  MAC control elements  SDU 

  .  .  . 

Transport channels (SCH)
PHY
3GPP TS 36.201, modulation, coding, power control, cell search, measurements and other phy specific procedures

Transport block  CRC 

  .  .  . 

Physical channels (DL-PDSCH, UL-PUSCH)

Between UE and eNB, data flow are managed with Data Radio Bearers, identified with DRB Identity, mapped to MAC Logical Channel Identity. DRB identities range from 1 to 11. MAC LCIDs for DTCHs range from 3 to 11.

In next article, we will look at data flow at eNode B.

References: 3G Evolution: HSPA and LTE by Dahlman, Parkvall, Sköld, and Beming, LTE - From Theory to Practice, Edited by Sesia, Toufik, and Baker, and SAE and the Evolved Packet Core: Driving the Mobile Broadband Revolution by Olsson, Sultana, Rommer, Frid, and Mulligan.

Copyright © Samir Amberkar 2010-11§

LTE - dedicated bearer setup « LTE Index » LTE - end-to-end data flow eNB