This presentation discusses about the WCDMA air Interface used in 3G i.e. UMTS. This Radio Interface has great capability on which Third Generation of Mobile Communication is built, with backward compatibility.

3.  Lowest layer in this interface is physical layer,
(PHY).
 The physical layer has interface to both MAC
and RRC sub-layer.

4. Layer 2 Consists of
 Medium Access Control (MAC)
 Radio Link Control (RLC)
 The Broadcast Multicast Control (BMC)
 Packet Data Convergence Protocol (PDCP)

5. Layer 3 consists of:
 RRC
 Mobility Management (MM)
 GPRS Mobility Management (GMM)
 Call control (CC)
 Supplementary services (SS)
 Short Message Service (SMS)
 Session Management (SM)
 GPRS Short Message Service support(GSMS)

8.  FEC encoding/decoding of transport channels
 Radio measurements and indications to
higher layers
 Macro diversity distribution/combining and
SHO execution
 Error detection on transport channels
 Multiplexing of transport channels and de
multiplexing of coded composite transport
channels (CCTrCHs)

9.  Rate matching
 Mapping of CCTrCHs on physical channels
 Modulation, spreading/demodulation, and
de-spreading of physical channels
 Frequency and time synchronization
 Closed-loop power control
 Power weighting and combining of physical
channels
 RF processing

10.  FEC scheme aims to reduce transmission
error
 UTRAN employs two FEC schemes
(i) Convolution codes
(ii) turbo codes

11.  Radio measurements is to be carried by
physical layer and result is to be reported to
higher layers.
 These measurements can be specific to either
UE or Node B

12. Possible measurement types of UE :
 Received Signal Code Power (RSCP)
 Received signal strength indicator (RSSI)
 Block error rate (BLER)
 UE transmitted power
 CFN-SFN observed time difference
 UE Rx-Tx time difference
 Observed time difference to GSM cell

13. Possible measurement types for UTRAN
 Received total wide band power
 Signal to interference ratio (SIR)
 SIR error
 Transmitted carrier power
 Transmitted code power
 Bit error rate (BER)
 Round trip time
 SFN-SFN observed time difference

14.  Macro diversity (SHO) is a situation in which a
receiver receives the same signal from
different sources.
 This macro diversity should be combined,
Without combining interference level would
increase and capacity decreased by
considerable amount.
 This combining is done at physical layer using
RAKE receiver

15. RAKE receiver

16.  The purpose of error detection is to find out
whether a received block of data was
recovered correctly.
 CRC is used for this.
 There are five CRC polynomial lengths in use
(0, 8, 12, 16, and 24 bits)

17.  Each UE can have several transport channels
in use simultaneously.
 Every 10 ms, one radio frame from each
transport channel is multiplexed into a
(CCTrCH), serially.
 For uplink, FDD mode has 1 CCTrCH
TDD mode has multipleCCTrCHs
 For downlink, both FDD andTDD modes have
multipleCCTrCHs

18.  The number of bits on a transport channel
can vary with every transmission time
interval. However, the physical channel radio
frames must be completely filled.
 To match bit rate after transport channel with
total physical channel bit rate either
repeating or puncturing bits techniques is
used.

19.  If there is more than one physical channel in
use, then the bits in the CCTrCH must be
divided among them.This is done by
segmenting the input bits evenly for each
physical channel.
 Since rate matching is already done in an
earlier phase, so the bits should fit nicely into
physical channels.

20. 

21.  In the scrambling procedure, the I- and Q-
phases are further (after channelization)
multiplied by a scrambling code.
 These scrambling codes have good
autocorrelation properties.
 The modulation scheme in the UTRAN is
quadrature phase shift keying(QPSK).
 Modulation rate = 3.84 Mcps

22.  This procedure takes place when the power is
turned on in the UE, starts with downlink SCH
synchronization.
 The UE knows the SCH primary
synchronization code, which is common to all
cells.
 P-SCH and S-SCH both are sent over first 256
chips of each slot (of 2560 chips).
 There are 15 such slots in each radio frame.

23. Structure of synchronization channel

24.  In UTRAN two forms of power control : open
loop & closed loop.
 Closed loop power control is further divided
into : inner loop & outer loop power control.
 Outer loop power control sets the Signal to
Interference Ratio (SIRtarget) and Inner loop
power control adjusts the peer entity
transmit power so that measured SIR fulfills
the SIRtarget requirement.

25. In Uplink

26.  In the uplink, one UE can transmit
simultaneously one DPCCH and up to six
DPDCHs.
 The control channel (DPCCH) will be sent in
the Q-plane, and the data channels (DPDCH)
in both planes.
 The channelization codes are orthogonal
codes, and the scrambling code is a pseudo-
random sequence.

27. In downlink

28.  All channels have their own power weight
factor G.
 All physical channels (except the SCH) are
processed in the same way as a DPDCH.
 All channels (except the SCH) are scrambled
with the same scrambling code.

29.  Four UE Power Classes

30.  Frequency bands

31.  RF specification

32.  There are three separate channel concepts in
the UTRAN: logical, transport and physical
channels.

33.  Logical channels define what type of data is
transferred.
 It can be divided into control channel and
traffic channel.
 Control channels transfer Control plane (C-
plane) information and traffic channels User
plane (U-plane) information.
 A control channel can either be common or
dedicated.

34.  A common channel is a point-to-multipoint channel;
i.e. common to all users in a cell.
 A dedicated channel is a point-to-point channel; i.e.
used by only one user.
 The defined logical control channels are:
Broadcast control channel (BCCH)
Paging control channel (PCCH)
Dedicated control channel (DCCH)
Common control channel (CCCH)
Shared channel control channel (SHCCH)
 The used logical traffic channels are:
Dedicated traffic channel (DTCH)
Common traffic channel (CTCH)

35.  The transport channels define how and with
which type of characteristics the data is
transferred by the physical layer.
 Transport channels are divided into common
channels and dedicated channels.
 All these channels are unidirectional.

36.  Common transport channels include:
Broadcast channel (BCH)
Paging channel (PCH)
Random access channel (RACH)
Common packet channel (CPCH)
Forward access channel (FACH)
Downlink shared channel (DSCH)
High-speed downlink shared channel (HS-DSCH)
Uplink shared channel (USCH)
 The only dedicated transport channel type is:
Dedicated channel (DCH)

37.  Physical channels define the exact physical
characteristics of the radio channels.
 In frequency-division duplex (FDD)
mode, both the uplink and downlink bands
have their own frequency channels.
 In time-division duplex (TDD) mode, there is
only one frequency channel, which is then
dynamically time-divided for both uplink and
downlink slots.

38.  Downlink
Synchronization channel (SCH)
Common pilot channel (CPICH)
Primary common control physical channel (P-CCPCH)
Secondary common control physical channel (S-CCPCH)
Physical downlink shared channel (PDSCH)
Paging indicator channel (PICH)
Acquisition indicator channel (AICH)
 Downlink and Uplink
Dedicated physical data channel (DPDCH)
Dedicated physical control channel (DPCCH)
 Uplink
Physical random access channel (PRACH)
Physical common packet channel (PCPCH)
Uplink dedicated control channel for HS-DSCH (HS-DPCCH)

39.  Downlink
Primary common control physical channel (P-CCPCH)
Secondary common control physical channel (S-CCPCH)
Synchronization channel (SCH)
Paging indicator channel (PICH)
Physical downlink shared channel (PDSCH)
Physical Node B synchronization channel (PNBSCH)
High speed physical downlink shared channel (HS-PDSCH)
Shared control channel for HS-DSCH (HS-SCCH)
 Downlink and Uplink
Dedicated physical channel (DPCH)
 Uplink
Physical random access channel (PRACH)
Physical uplink shared channel (PUSCH)
Shared information channel for HS-DSCH (HS-SICH)

40.  The spreading process actually consists of
two phases, spreading and scrambling, and
both of them use different types of codes
with different characteristics.

41.  Spreading increases the bandwidth of the
signal.
 Spreading codes used are orthogonal
 Scrambling shuffles the bit using a code
called scrambling code.
 Scrambling is done after the spreading in the
transmitter
 Scrambling codes are pseudo-random
sequence of bits.

42.  A signal can be subjected to time diversity,
multipath diversity, and antenna diversity.

43.  Time diversity means that the signal is spread
in the time domain.
 Time diversity spreads the faulty bits over a
longer period of time, and thus makes it
easier to reconstruct the original data.

44.  Multipath diversity is a phenomenon that
happens when a signal arrives at the receiver
via different paths.

45.  In aWCDMA system the receiver is typically
able to track and receive several multipath
components and combine them into a
composite signal.
 The receiver is of the RAKE variety.
RAKE receiver

46.  In a CDMA system the same signal can be
transmitted over the air interface, on the
same frequency, from several base stations
separated by considerable distances.This
scheme is called the soft handover (SHO).
 In a SHO all the participating base stations
use the same frequency, and the result is a
macro diversity situation.

47.  A typical SHO situation

49.  Radio interface protocols can be divided in
two ways: horizontal layers and vertical
planes.

50.  The UTRAN MAC can even contain different
functionalities depending on whether it
supports FDD,TDD, or both modes.
 The MAC is not a symmetric protocol; the
entities in the UE and in the UTRAN are
different.

51. The services MAC provides to the upper layers
include the following:
 Data transfer;
 Reallocation of radio resources and MAC
parameters;
 Reporting of measurements to RRC.

52.  Mapping between logical channels and
transport channels;
 Priority handling between data flows of one
UE;
 Priority handling between UEs by means of
dynamic scheduling;
 Identification of UEs on common transport
channels;
 Traffic-volume monitoring;

53.  Transport-channel type switching;
 Ciphering for transparent RLC;
 Selection of the appropriate transport format
for each transport channel depending on the
instantaneous source rate;

54.  RLC layer is in charge of the actual data
packet transmission over the air interface.
 The RLC task maintains a retransmission
buffer, performs ciphering, and routes the
incoming data packets to the right
destination task (RRC, BMC, PDCP, or voice
codec).

56.  Transparent DataTransfer Service
Segmentation and reassembly;
Transfer of user data;
SDU discard.
 Unacknowledged DataTransfer Service
Segmentation and reassembly;
Concatenation;
Padding;
Transfer of user data;
Ciphering;
Sequence number check;
SDU discard.

57.  Acknowledged DataTransfer Service
Concatenation;
Padding;
Transfer of user data;
Error correction;
In-sequence delivery of higher-layer PDUs;
Duplicate detection;
Flow control;
Protocol error detection and recovery;
Ciphering;
SDU discard.

58.  Segmentation and reassembly of higher-
layer PDUs into/from smaller RLC payload
units;
 Concatenation (RLC SDUs may be
concatenated so that they will fill
 the RLC PUs);
 Padding;
 Transfer of user data;
 Error correction;

59.  In-sequence delivery of higher-layer PDUs;
 Duplicate detection;
 Flow control;
 Sequence number check (in unacknowledged
data transfer mode);
 Protocol error-detection and recovery;
 Ciphering (in UM and AM modes);
 Suspend/resume function.

60.  The RRC controls the configuration of the
lower layers in the protocol stack, and it has
control interfaces to each of the lower layers
(PDCP, BMC, RLC, MAC, and layer 1).

61.  General control
 Notification
 Dedicated control

62.  Initial cell selection and cell reselection
 Broadcast of information reception of paging
messages;
 Establishment, maintenance, and release of
RRC connection;
 Establishment, reconfiguration, and release
of radio bearers;

63.  Handovers (HOs);
 Measurement control;
 Outer-loop power control;
 Security mode control;
 Control of requested QoS;
 Contention resolution in theTDD mode;
 Timing advance in theTDD mode;

64.  Mobility Management (MM)
Main function of the MM is location management.
MM procedures can be divided into three groups:
 MM common procedures;
 MM specific procedures;
 MM connection-management procedures.

65.  GPRS Mobility Management (GMM)
The GPRS mobility management (GMM) sub layer
provides services to the session management (SM) entity
and to the SMS support entity for message transfer.
GMM procedures can be of two types:
▪ GMM common procedures;
▪ GMM-specific procedures.

66.  CallControl (CC)
A CC entity supports the following elementary procedures:
▪ Call-establishment procedures;
▪ Call-clearing procedures;
▪ Call-information-phase procedures;
▪ Miscellaneous procedures.

67.  Supplementary Services (SS)
Supplementary services (SS) are value-added services that
may or may not be provided by the network operator.
 Short Message Service (SMS)
The purpose of the SMS is to provide a means to transfer
short text messages between a UE and a short message
service center (SMSC).These messages are sent using the
control signaling resources, and their maximum length can
be only 160 characters.

68.  Session Management (SM)
The main function of the SM protocol is to support packet
data protocol (PDP) context handling of the user terminal.
there is no “connection” concept in a (IP) packet-switched
system.
 GPRS Short Message Service Support (GSMS)
The GPRS Short Message Service (GSMS) protocol task
handles the SMS service while the UE is attached to the
GPRS system.This protocol is an extension of the circuit-
switched SMS protocol.

69.  MAC and RLC are in both the planes.
 PDCP and BMC exist only in user plane.
 The U-plane is responsible for the transfer of
user data, such as voice or application
data, whereas the C-plane handles the
control signaling and the overall resource
management

70.  The functions the PDCP perform following:
 Header compression and decompression of IP
data streams;
 Transfer of user data;
 Maintenance of PDCP sequence numbering;
 It uses the service provided by a lower layer
called Radio Link Control (RLC).

71.  Broadcast/multicast control is a layer 2 sub-
layer that exists only in the U-plane.
 This layer handles only downlink
broadcast/multicast transmission.
 The functions of BMC are:
▪ Storage of cell broadcast messages;
▪ Traffic-volume-monitoring and radio resource requests
forCBS;
▪ Scheduling of BMC messages;
▪ Transmission of BMC messages to UEs;
▪ Delivery of cell broadcast messages to the upper layer

72. Queries