umts theory - zte rf multan

UMTS Theory

Difference Between 2G and 3G SIM Cards

A regular SIM come with the 32KB of SIM memory that sufficient to handle data on 2G network.

3G network use more channels and very much faster than 2G thus it required more memory on SIM card to handle 3G network data follow to process high speed data just like cache memory so 3G SIM has memory of 128 KB.

That is the main difference otherwise there is not other differences.

http://www.techorient.com/2013/08/difference-between-2g-and-3g-sim-cards.html

Network Architecture

GSM900/1800: 3G (W CDM A):

Single Frequency Network

Channel Element in UMTS Network

• CE resources are a type of NodeB hardware resource.

• The number of CEs supported by single NodeB indicates the capacity resource of the NodeB.

• Services at different rates require different numbers of CEs to ensure proper CEs are classified into uplink (UL) CEs and downlink (DL) CEs.

Freq. 1

Freq. 1

Code A

Code B

Code

C

BS1

BS2

Code D

Code E

CDMA Application

Users are distinguished by scrambling codes and OVSF codes Self-interference system CDMA system is restricted to interference (GSM system is restricted to

frequency resources)

NarrowbandSystem

Fading

Transmit Signal Received Signalff

P(f) P(f)

Fading

Transmit Signal Received Signalff

P(f) P(f)

BroadbandSystem

Countering Fading

Function of OVSF Code

OC1, OC2OC3, OC4

OC5, OC6, OC7

OC1 , OC2, OC3OC1, OC2

OC1, OC2, OC3, OC4

Uplink: distinguish different radio channels from the same UE.

Downlink: distinguish different radio channels from the same NodeB.

Function of Scrambling code

Downlink: distinguish different Cells Uplink: distinguish different UEs

PN3 PN4

PN5 PN6

PN1 PN1

Cell Site “1” transmits using PN code 1

PN2 PN2

Cell Site “2” transmits using PN code 2

Concept of orthogonal code

Orthogonal—the result of multiplying and sum is 0

Code1 +1 -1 +1 +1 -1 +1 -1 -1

Code2 -1 +1 +1 -1 -1 +1 +1 -1

Mul -1 -1 +1 -1 +1 +1 -1 +1

Sum 0Orthogonal

Code1 +1 -1 +1 -1 -1 +1 -1 -1Code2 +1 +1 -1 +1 -1 -1 +1 -

1Mul +1 -1 -1 -1 +1 -1 -1 +1Sum -2

Non-orthogonal

Why CDMA system is a self interference system?

Since all the users use orthogonal code, where does the self interference come from?

Comes from the code error during the transfer. If there are some code error on one user’s information,

it misses some orthogonal to others. Then interference comes.

Additional Slide :: Data rates w.r.t SF

Air Interface

2chc

3chc

1chc

scramblingc Modulation

Spreading code & scrambling code

Code channel： spread code Relative to service rate， extended to 3.84Mchips/s A kind of orthogonal code

Code scrambling： scrambling code Have no effect on signal bandwidth Downlink for identifier cell， uplink identifier terminal A pseudo-random sequence

Modulation Methods in UMTS

BPSK (Binary Phase Shift Keying) in Uplink channles QPSK (Quadrature Phase Shift Keying) in Downlink channels 16QAM (16-state Quadrature Amplitude Modulation) in HSDPA

Coverage/capacity VS Data Rate

Higher data rate needs higher power High data rate transmission is only available nearby the station

>12.2 kbps

>64 kbps

>384 kbps

>144 kbps

Coverage decrease

Subscriber num increase

Cell breathing is one of the means for load control

The purpose of cell breathing is to share the load of hot-spot cell with the light loaded neighbor cells, therefore to improve the utilization of system capacity.

Cell Breathing Effect

Example for load control

Cell Breathing Effect With the increase of activated

terminals and the increase of high speed services, interference will increase.

The cell coverage area will shrink. Coverage blind spot occurs Drop of call will happen at the edge

of cell

Coverage and

capacity are

interrelated

Active Set:The set of radio links simultaneously involved in the communication between a UE and a NodeB is called ActiveSet. Up to three radio links can be included in the active set. In addition to measuring and evaluating the radio links (or cells) in the active set, the UE also continuously monitors and evaluates the signals from other surrounding cells.

The Monitored Set are together with the active set the cells that the WCDMA RAN explicitly orders the UE to measure on, which normally are the defined neighbors to the cells in the active set

The Detected Set contains all cells that the UE detects that are not part of the active or monitored sets

Radio Measurements

Radio Measurements

Channels in UMTS

• UMTS• WCDMA – FDD (Widely Used)• Frequency-division duplexing (FDD) means that the

transmitter and receiver operate at different carrier frequencies.

WCDMA – TDDTime-division duplexing (TDD) is the application of time-division multiplexing to separate outward and return signals. A single Band 5MHz is used for both uplink and downlink transmission.

Channels Characteristics

Logical Channels

Transport Channels

Physical Channels

Downlink Physical Channels

Uplink Physical Channels

Dr. A. Chockalingam Dept of ECE, IISc, Bangalore 69

Transport Formats / Configurations Transport Block (TB)

» Basic unit of data exchanged between L1 & MAC for L1 processing

Transport Block Size: Number of bits in a TB. Transport Block Set (TBS)

» A set of TBs exchanged between L1 and MAC at the same time instant using the same transport channel

Transport Block Set Size: Number of bits in a TBS Transmission Time Interval (TTI)

» Periodicity at which a TBS is transferred by the physical layer on to the radio interface - {10, 20, 40, 80 ms}

» MAC delivers one TBS to the physical layer every TTI


Transport Formats / Configurations Transport Format (TF)

– Format offered by L1 to MAC (and vice versa) for the delivery of a TBS during a TTI on a given transport channel (TrCH)– Dynamic part (TB size, TBS size)– Semi-static part (TTI, type/rate of coding,size of CRC)– TB size, TBS size, TTI define the TrCH bit rate before L1 processing

» e.g., TB size = 336 bits (320 bit payload + 16 bits RLC header)» TBS size = 2 TBs per TTI, TTI = 10 ms» DCH Bit rate (with RLC header) = 336*2/10 = 67.2 Kbps» User Bit rate (without RLC header) = 320*2/10 = 64 Kbps

– Variable bit rate can be achieved by changing (between TTIs) either the TBS size only, or both the TB size and TBS Size

Transport Format Set (TFS)– a set of TFs associated with a TrCH– semi-static part of all TFs in a TFS is the same


Transport Formats / Configurations Transport Format Combination (TFC)

» Multiple TrCHs each having a TF» Authorized combination of the currently valid TFs that can be

submitted to L1 on a CCTrCH, containing one TF from each TrCH Transport Format Combination Set (TFCS)

» A set of TFCs on a CCTrCH. Produced by RNC» TFCS is given to MAC by L3 for control» MAC chooses between the different TFCs specified in the TFCS» MAC has control over only the dynamic part of the TFs. Semi-static part

relates to QoS (e.g., quality) and is controlled by RNC admission control» Bit rate can be changed quickly by MAC with no need to L3 signaling

Transport Format Indicator (TFI)» A label for a specific TF within a TFS. Used between MAC and L1

Transport Format Combination Indicator (TFCI)» Used to inform the receiving side of the currently valid TFC


Transport Formats / Configurations

TTI TTI TTI

TTI TTI TTI

TBDCH1

DCH2

TB TB

TB TB TB

TB

Transport Block Set(TBS)

TB

TB

Transport Format (TF)Transport Format

Set (TFS)

Transport FormatCombination (TFC)

Transport FormatCombination Set

(TFCS)


TFI and TFCI (Transmitter)

Transport Chl 1 Transport Chl 2 Transport

BlockTransport

Block

Transport Block

Transport BlockTFI TFI

TFCICoding and Multiplexing

Physical Layer

Higher Layer

DPCCH (Q-Chl) DPDCH (I-Chl)

Physical Control Chl

Physical Data Chl

E.g: Two transport channels mapped to a single physical channel

This dotted linerepresents the Iur interface in case of NW side


TFI and TFCI (Receiver)

Transport Chl 1 Transport Chl 2

Transport Block & EI



Transport Block & EITFI TFI

TFCIDecode

Decoding and Demultiplexing

Physical Layer

Higher Layer

DPCCH (Q-Chl) DPDCH (I-Chl)

EI: Error Indication

Physical Control Chl

Physical Data Chl


TFI and TFCI

Each transport channel is accompanied by a TFI at each time event at which data is expected to arrive from HL

Physical layer combines the TFI info from different transport channels to the TFCI

TFCI is sent on the DPCCH to inform the receiver about the instantaneous transport format combination of the transport channels mapped to the U/L DPDCH transmitted simultaneously

DPCCH has 10 bits in Timeslot so fixed rate of 15kbps on 256 spreading factor.

DPCH is time multiplex of DPCCH and DPDCH

Channel Synchronisation acquired Note

PrimarySCH

Chip, Slot, SymbolSynchronisation

256 chipsThe same in all cells

Secondary SCH Frame Synchronisation,Code Group (one of 64)

15-code sequence of secondary synchronisation codes.There are 16 secondary synchronisation codes.There are 64 S-SCH sequences corresponding to the 64 scrambling code groups256 chips, different for different cells and slot intervals

Common Pilot CH Scrambling code(one of 8)

To find the primary scrambling code from common pilot CH

PCCPCH *)Super Frame Synchronisation,BCCH info

Fixed 30 kbps channel27 kbps ratespreading factor 256

SCCPCH **)Carries FACH and PCH channelsVariable bit rate

http://www.umtsworld.com/technology/frequencies.htm

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umts theory - zte rf multan

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