3g complete knowledge

3G Complete

Knowledge

WCDMA Fundamentals• Separate users through different codes

• Large bandwidth

• Continuous transmission and reception

• Code planning - Frequency reuse is 1

• No frequency planning

• Scrambling code planning

• 5 MHz carrier separation

• Fast Power Control

• Soft/Softer Handover

• Admission Control

• Congestion Control

time

frequency

Code-Division Multiple Access

codeCDMA

3GPP : 3rd Generation Partnership Project http://www.3gpp.org

UTRAN Architecture

OSS

(Universal Terrestrial Radio Access)

RN Interfaces

• Iu– Iu PS

• Connection to the packet switched core network domain– SGSN/GGSN

– Iu CS• Connection to the circuit switched core network domain

– MSC

– Protocol RANAP• Iur

– RNC interconnection [eg: for SHO support ]

– Protocol RNSAP• Iub

– Connection for the RBS to the RNC– Protocol NBAP

• Uu– Air Interface to the UE– Protocol RRC, RLC, MAC

Core Network

RNC

RNC

Iu

Iur

Iub

UuRBS RBS

RBS

UE

Basics of 3G

Basics of 3G• WCDMA Bandwidth• FDD – 5 MHZ of Paired• TDD – 5 MHZ Only

• SF and Data rate• SF is lower when data rate is higher

• SF and Power Relation• When lower the SF then more power required

• SF and Coverage relation• SF is high then coverage will be high

• CPICH Power -:• It takes about 8 to 10% of the total NodeB Power .For a 20W (43dBm) NodeB, CPICH is around 2W

(33dBm).• In urban areas where in-building coverage is taken care of by in-building installations, the CPICH may

sometimes go as low as 5% because:• The coverage area is small since users are close to the site, and• More power can be allocated to traffic channels.

Basics of 3G• RSCP –• Stand for Received Signal Code Power, the energy per Chip in CPICH averaged over 512 chip.

• RSSI – • The desired total signal of UTRA carrier frequency.• Received energy of all cells in particular location.

• RSCP = RSSI/Ec/No

Basics of 3G• TCP-• During the Power Control, transmit power control command is used to power up and Power Down

based on SIR Target in the step of 0.5 dB.

• Active Set –• It Consist group of cells that takes part in soft & softer HO and measured by UE. Typically Active set size

is 3 or 4.• HO Window size is 4 to 6 dB

• Pilot Pollution –• When number of strong cell added in Active set size there is pilot pollution.

• Compressed Mode –• Compressed mode is physical layer function that allowed to UE to temporally tune to another

frequency , and measured the RF environment of another UMTS Frequency.

• Cell Breathing –• The cell coverage shrink as the loading increase in called cell breathing.

• TTI –• After every TTI resource can be redistributed among the user, resources uses is more efficient.

Basics of 3G• TMA-• It reduce the system noise, Improve the UL sensitivity and leads to longer UE Battery life• TMA Gain – 12 dB• Sensitivity is the minimum input power needed to get a suitable signal-to-noise ratio (SNR) at the output of the

receiver. It is determined by receiver noise figure, thermo noise power and required SNR. Thermo noise power is determined by bandwidth and temperature, SNR is determined by modulation technique, therefore the only variable is noise figure.

• The cascading noise figure can be calculated by Friis equation (Herald Friis):• NFt = NF1 + (NF2-1)/G1 + (NF3-1)/(G1*G2) + ... + (NFi-1)/(G1*G2*...*Gi)• As the equation shows, the first block imposes the minimum and the most prominent noise figure on the

system, and the following blocks imposes less and less impact to the system provided the gains are positive. Linear passive devices have noise figure equal to their loss. A TMA typically has a gain of 12dB.

• There are typically top jumper, main feeder and a bottom jumper between antenna and BTS. A TMA placed near antenna with a short jumper from antenna provides the best noise figure improvement – the noise figure will be restricted to the top jumper loss (NF1) and TMA ((NF2-1)/G1), and the remaining blocks (main feeder and bottom jumper) have little effect.

• To summarize, a TMA has a gain that’s close to feeder loss.

• Why TMA are installed at the top near the antenna and not the bottom near the NodeB?

• Based on Friis Equation, having a TMA near the BTS will have the top jumper and main feeder losses (noise figures) cascaded in and a TMA will not be able to help suppress the losses.

Basics of 3G• Processing gain –• Processing gain is the ratio of chip rate over data bit rate, usually represented in decibel (dB) scale. For

example, with 3.84MHz chip rate and 12.2k data rate, the processing gain is:• PG12.2k = 10 * log (3,840,000 / 12,200) = 25dB

• calculate maximum number of users on a cell-- • To calculate the maximum number of users (M) on a cell, we need to know:

• W: chip rate (for UMTS 3,840,000 chips per second)

• EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

• i: other-cell to in-cell interference ratio (assuming 60%)

• R: user data rate (assuming 12,200 kbps for CS-12.2k)

• η: loading factor (assuming 50%)

• Take 12.2kbps as example:

• M = W / (EnNo * (1 + i) * R) * η = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8

• The number of users could also be hard-limited by OVSF code space. Take CS12.2k for example:

• A CS-12.2k bearer needs 1 SF128 code.

• Total available codes for CS-12.2k = 128 – 2 (1 SF64) – 2 (4 SF256) = 124.

• Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.

Basics of 3G• Cell Selection Criteria –• Qmean = the average SIR target cell• Qmin = minimum SIR required• Pcomponsation = a correction value for different UE classes

• S = Qmean – Qmin – Compensation • If S>0 then the cell is valid candidate.• A UE camp on the cell with higher S

• DRX Cycle –• The UE listen to the PICH only at certain predefined times, reducing the power consumption. The periodically

of these search is set by the system and the time interval is called Discontinues Reception.• Different DRX cycle are used for CS and PS service in Ideal mode. A separate DRX cycle is also used to page

connected mode UEs in state URA_CPH.

• Near Far Effect –• All users use the same bandwidth at the same time and therefore users interface with one another. Due to

the propagation path loss, the signal received by the base station from UE close to the base station will be stronger the signal received from another terminal located at the boundary. Hence the distant user will be dominated by the close user. This is called near - far – effect.

• Solution of this problem is power control, which attempt to achieve the same mean received power for each user.

Basics of 3G• Noise Rise –• For every new user added to the service addition noise is added to the network. This is each new user causes

a “noise rise” . In theory the “noise rise” is defined as the ratio of total received wideband power to the noise power.

• Higher “nose rise” value implies more users are allowed on the network, and each user has to transmit the higher power to over come the higher noise level. This means smaller path loss can be tolerate and the cell radius is reduced.

• AT what circumstances can a Node B reach its max capacity? What are the Capacity Limitations?

• NodeB reaches its max transmit power, runs out of its channel element, uplink noise rise reaches its design target.

• Resource Management for Capacity Management –• DL Power• Received Total Wideband Power• OVSF Codes• RBS Channel Element

• Three Sets in HO –• Active Set• Monitor Set• Detected Set

Basics of 3G• Measure Difference between GSM and UMTS HO decision –• GSM:• Time based mobile measure of Rx Lev and Rx Qual – mobile sends measurement report every SACH period

(480ms)• BSC instruct to mobile to HO based on these reports.

• UMTS:• Event triggered reporting - UE send a measurement report only on certain event “triggered “.• UE plays more part in the HO decision.

• Direct Retry –• When there is a co – existing GSM RAN, Excess traffic in a WCDMA cell may be offloaded to GSM.• In a call is chosen for Direct Retry to GSM, the request for the speech RAB will be rejected with cause “Direct

Retry” and then a request is made to the core n/w to relocate the UE to a specific GSM cell, using the Inter – RAT HO procedure. This HO is blind one since the target cell is chosen not based on UE measurements. Therefore, the target cell must be co – located with the WCDMA cell.

• CO – Located GSM cells are assumed to have similar coverage and accessibility as their respective WCDMA cells.

• Default Value -85

Basics of 3GEVENTS –• e1a - a primary CPICH enters the reporting range, i.e. add a cell to active set.• e1b - a primary CPICH leaves the reporting range, i.e. removed a cell from active set.• e1c - a non active primary CPICH becomes better than an active Primary CPICH, i.e. replace a cell.• e1d - Change the best cell• e1e - a Primary CPICH becomes better than an absolute threshold.• e1f - a Primary CPICH becomes worse that an absolute threshold. • e2a - for inter frequency HO measurement. Change the best frequency.• e2d - for inter frequency HO measurement. The estimate quality of the currently used frequency is below a

certain threshold.• E2b – the estimate quality of the currently used frequency is below a certain threshold and the estimate

quality of non – used frequency is above a certain threshold.• E2c - The estimate quality of a non – used frequency is above certain threshold.• E2e- The estimate quality of non – used frequency is below a certain threshold.• E2f – The estimate quality of the currently used frequency is above a certain threshold.• e3a - for IRAT HO measurement. • e3d - for IRAT HO measurement. There was a change in the order of best GSM cell list.• E3b – the GSM cell quality has moved below threshold • E3c – the GSM cell quality has moved above a threshold

• Inter – frequency HO evaluation is based its decision on P – CPICH quality measure on the currently used frequency and on one or more non – used frequency. If the evaluation result is positive, one cell on a non – used frequency is proposed to Inter – Frequency HO execution.

• Inter – Frequency Ho is hard HO where the UE is ordered by the n/w to tune to another frequency . Means that there will be a small interruption in data flow to and from the UE

RABs supported in RAN P2.1

Conversational Speech 12.2 kbps Circuit switched

Conversational CS Data 64 kbps Circuit switched

Streaming 57.7 kbps Circuit switched

InteractiveVariable rate Packet Switched

RACH/FACH, 64/64, 64/128, 64/384

Combination of Conversational Speech and Interactive 64/64 Multi-RAB

Radio Access Bearer (RAB) A radio access bearer (RAB) connection via UTRAN is realised by two concatenated

segments, the Iu bearer connection and the radio bearer connection

UMTS Radio Access Protocol structureUser Plane and Control Plane

MAC

RLCRLC

RLCRLC

RLCRLC

RLCRLC

RRC

Physical Layer

Co

ntr

ol

Co

ntr

ol

Mea

sure

men

ts

Transport channels

Logical channels

User planeControl plane

Layer 1

Layer 2 MAC

Layer 2 RLC

Layer 3

Radio bearers

Signaling channels

Signaling Radio Bearer (SRB)

Radio Bearer for User Data (RB)

RAB and RAB realizations

• RAB (Radio Access Bearer)– “Owned” by the core network (CN)– CN determines, traffic class, QoS etc

• RB (Radio Bearer)– “Owned” by the Radio Network– One RAB can be mapped to several Radio Bearers

• E.g., different bit classes for AMR– RB is how Radio Network realizes a RAB

• SRB (Signaling Radio Bearers)– Needed for signaling of, e.g., connection setups, measurements, RN procedures

etc.• Logical Channels

– An RB is mapped to a Logical Channel– All user data mapped to DTCH

Radio Access Bearers (RABs)

• CS -- – Speech AMR 12.2 kbps– Data (Video) 64 kbps

• PS I/B (UL/DL)– 64/64 kbps– 64/128 kbps– 64/384 kbps– 128/128 kbps (P5)

• HSDPA– 64/HSDPA interactive– 384/HSDPA interactive

• Multi-RAB– Speech AMR 12.2 kbps + 64/HSDPA (P5)– Speech AMR 12.2 kbps + 384/HSDPA (P5)

Radio Bearers

• No guaranteed performances for an interactive/background RAB

• Dedicated 64/64, 128/64, 384/64 kbps RAB

• Streaming 128/128 kbps RAB

UTRANUTRAN

UMTS/GPRSUMTS/GPRSBackboneBackbone

SGSN GGSN

RBS RNC

RAB

Radio bearer

• Interactive/background RAB forms the bases for normal PS best effort data

UMTS/CSUMTS/CS

BackboneBackbone

MSC

Mapping of UMTS Services to RABs

Basics of 3G• Processing gain –• Processing gain is the ratio of chip rate over data bit rate, usually represented in decibel (dB) scale. For

example, with 3.84MHz chip rate and 12.2k data rate, the processing gain is:• PG12.2k = 10 * log (3,840,000 / 12,200) = 25dB

• calculate maximum number of users on a cell-- • To calculate the maximum number of users (M) on a cell, we need to know:

• W: chip rate (for UMTS 3,840,000 chips per second)

• EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

• i: other-cell to in-cell interference ratio (assuming 60%)

• R: user data rate (assuming 12,200 kbps for CS-12.2k)

• η: loading factor (assuming 50%)

• Take 12.2kbps as example:

• M = W / (EnNo * (1 + i) * R) * η = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8

• The number of users could also be hard-limited by OVSF code space. Take CS12.2k for example:

• A CS-12.2k bearer needs 1 SF128 code.

• Total available codes for CS-12.2k = 128 – 2 (1 SF64) – 2 (4 SF256) = 124.

• Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.

Eb/No

• Eb/No• By definition Eb/No is energy bit over noise density, i.e. is the ratio of the energy per information bit to the

power spectral density (of interference and noise) after dispreading.• Eb/No = Processing Gain + SIR• For example, if Eb/No is 5dB and processing gain is 25dB then the SIR should be -20dB or better.

The Eb/No targets are dependent on the service:On the uplink, typically CS is 5 to 6dB and PS is 3 to 4dB – PS is about 2dB lower.On the downlink, typically CS has 6 to 7dB and PS is 5 to 6dB – PS is about 1dB

lower.

Eb/No requirement lower for PS than for CSPS has a better error correction capability and can utilize retransmission, therefore it can afford to a lower

Eb/No. CS is real-time and cannot tolerate delay so it needs a higher Eb/No to maintain a stronger RF link.

Eb/No

Io = own cell interference + surrounding cell interference + noise densityNo = surrounding cell interference + noise density

Ec/Io

• Ec/Io is the ratio of the energy per chip in CPICH to the total received power density (including CPICH itself).

Ec/No

• CPICH Ec/No

• The CPICH Ec/No is used to determine the „quality“ of the received signal. It gives the received energy per received chip divided by the band‘s power density. The „quality“ is the primary CPICH‘s signal strength in relation to the cell noise. (Please note, that transport channel quality is determined by BLER, BER, etc. )

• If the UE supports GSM, then it must be capable to make measurements in the GSM bands, too. The measurements are based on the

SF Channelization operation: Transforms data symbols into chips. Thus

increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor （ SF ） .The operation is done through multiplication with OVSF code.

Scrambling operation is applied to the spreading signal.• Separates users through different codes• Codes are used for two purposes:

– Differentiate channels/users– Spreading the data over the entire bandwidth

Data bit

OVSF code

Scrambling code

Chips after spreading

Spreading principleSpreading code = Scrambling code + Channelization code

Scrambling codes (Repeat period 10 ms=38400 chips)– Separates different mobiles (in uplink)– Separates different cells (in downlink)

Channelization codes– Separates different channels that are transmitted on the same scrambling code– Orthogonal Variable Spreading Factor (OVSF) codes– Period depends on data rate

Spreading principle User information bits are spread into a number of chips by multiplying them

with a spreading code

The chip rate for the system is 3.84 Mchip/s and the signal is spread in 5 MHz

The Spreading Factor (SF) is the ratio between the chip rate and the symbol rate

The same code is used for de/spreading the information after it is sent over the air interface

Information signal

Spreading signal

Transmission signal

Spread Spectrum gain

Chanilization Code

• OVSF code is used as channelization code• It is used to spread the signal and channel separation from the cell.• Channelization Codes have different length depending on the bit rate• In the Downlink, Channelization Codes are used to distinguish between data (and control)

channels coming from the same RBS

In the Uplink, Channelization Codes are used to distinguish between data (and control) channels from the same UE

DL – 4 to 512 UL – 4 to 256

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

Scrambling Code• Scrambling code ： GOLD sequence.• Scrambling code period : 10ms ,or 38400 chips.• The code used for scrambling of uplink DPCCH/DPDCH may be of either

long or short type, There are 224 long and 224 short uplink scrambling codes. Uplink scrambling codes are assigned by higher layers.

• For downlink physical channels, a total of 218-1 = 262,143 scrambling codes can be generated. Only scrambling codes k = 0, 1, …, 8191 are used.

• SC used to separate the cells in N/W• In UL it is used to differentiate the terminals. After the Channelization Codes, the data stream is multiplied by a special

code to distinguish between different transmitters. • Scrambling codes are not orthogonal so they do not need to be

synchronized• The separation of scrambling codes is proportional to the code length –

longer codes, better separation (but not 100%)• Scrambling codes are 38400 chips long

Scrambling Codes

SC3 SC4

SC5 SC6

SC1 SC1

Cell “1” transmits using SC1

SC2 SC2

Cell “2” transmits using SC2

In the Downlink, the Scrambling Codes are used to distinguish each cell (assigned by operator – SC planning)

In the Uplink, the Scrambling Codes are used to distinguish each UE (assigned by network)

Scrambling Code planning

0 8 16 ... ... 5041 9 17 ... ... 5052 10 18 ... ... 5063 11 19 ... ... 5074 12 20 ... 500 5085 13 21 ... 501 5096 14 22 ... 502 5107 15 23 ... 503 511

64 Code Groups

SC are organized in Code Groups. The first SC in each Code Group differs from the first SC in the subsequent Code Group by a multiple of 8

Power Control

36

Power Control• Open Loop• Fast closed Loop• Outer Loop

• Open Loop• Controlled by UE• Determined in UL that how much power UE is uses• n/w inform to UE of current n/w status CPPICH Power, UL interference• UE use these parameter to calculate initial power of PRACH• Concept : Power is a common resource in WCDMA

• Goal : Ensure sufficient received energy per information bit for all communication links

• When UE is switch on, UE start to send the power to NodeB, first it will send minimum power then increase the power level till it gets Aquired in that perticuler network(Information get through AICH).

37

Power Control• Fast Closed Loop (Inner Loop)• Located in NodeB and UE• Controlled the power of dedicated physical channel• PC changes can occur every slots 1500 times/sec• NodeB and UE continuously compare SIR with SIR target and inform each other to

either increase of decrease its power

• Outer Loop • Located in RNC• Adjust the SIR for every user based on BLER• Keep the quality of communication at required level (BLER, SIR, BER) by setting SIR

target for fast power control

– compensates for fading channels

– needs dedicated control channel for power control commands

Handover

40

Hanover• Soft/Softer Hand Over• Inter Frequency hand Over• Inter RAT Handover• Core Network Hard Handover• Service Based Handover to GSM• HSDPA Mobility

• Soft/Softer Hand Over

UE connected to two or more RBSs at the same time

Explain Soft and Softer handover?• In Soft Handover, the UE connection consists of at least two radio

links established with cells belonging to different RBSs.

• In Softer handover, the UE connection consists of at least two radio links established with cells belonging to the same RBS.

• It acts as macro diversity since UE is connected to more than one radio link at any given point, adds redundancy and reduces interference. However there is a tradeoff between soft/softer handover & system capacity.

• A UE involved in Soft/Softer Handover uses several radio links, more DL channelization codes, and more DL power than a single-link connection.

• Consequently, if all the UEs connected to a particular RNC are considered, more resources are needed in the RBSs, more resources over the Iub and Iur interfaces, and more resources in the RNC. For this reason, the number of radio links involved in the Soft/Softer handover must be limited

Inter Frequency Handover?

• UE handover between different frequencies or between WCDMA

Inter RAT Handover

• Inter frequency handover between WCDMA and GSM

• GSM to WCDMA or Hard HO

HSPA• HSDPA represents an evolution of the WCDMA radio interface, which uses very

similar methods to those employed by EDGE (Enhanced Data Rates for GSM Evolution) technology for the GSM radio interface. The fundamental characteristics which enable the increase in the data throughput and capacity with reduced latency are summarized below:

• Time and code multiplexing of the users • Multi-Code transmission • Fixed Spreading Factor (SF = 16) • Shorter TTI = 2ms • No DTX (Discontinuous transmission) for the data channel • Adaptive modulation and coding (AMC) supporting higher order modulation • Node B scheduling and link adaptation • Node B retransmissions (H-ARQ – Hybrid Automatic Repeat-Request) • No power control • No soft handover

– The subscribers request higher speed and better quality data access– Competition challenge from CDMA EV/DO, WiMAX– Up to now, the throughput request for downlink is much more higher than

that of uplink– The channel configuration of R99 lead a very low efficiency on the downlink

capacity

HSPA Calculation• Chip rate in KBPS = 3840• Spreading Factor = 16• Speed =3840/16 = 240

• Modulation = 4 (N)• Coding Scheme = 15(M)• Total Speed for 16 QAM = Speed * Modulation Type (N)*Coding Scheme (M)• = 240 * 4* 15 = 14.4 MBPS

• Important Facts – • 2^n formula use for modulation scheme• QPSK 16 QAM 64 QAM• 2^1, N=1 2^4, N= 4 2^6, N= 6

• Code Used – • QPSK 16 QAM 64 QAM• 5 10 15 dynamic code will use for more then 64QAM

• Total Speed for 64 QAM = 240*6*15 =21.6

HSDPA Characteristics

HSDPA is the solution of WCDMA offering higher speed downlink data services.

Peak data rate in DL: 14.4Mbps (physical layer) Shorter delay Higher efficiency using downlink code and power and

bigger downlink capacity Flexible cell resource allocation More high speed user access

UMTS R99

GSM

HSDPA

Fast Scheduling Basic

If a little part of received 10ms frame (15 slots - R99) can’t be decoded correctly, whole frame will be retransmit 10ms later.

An HSDPA frame is only 2ms(3 slots). If a 2ms frame can’t be decoded correctly, just this 2ms frame need be retransmitted. Other 2ms(up to 6) HARQ process may continue transmitting data, thus radio resource could be used more effectively.

Physical Layer Basic

Fast SchedulingFast Scheduling

Scheduling Principle: based on channel condition in short period; based on balance between throughout and proportional fair for all users in long period.

Scheduling Principle: based on channel condition in short period; based on balance between throughout and proportional fair for all users in long period.

• Some basic scheduler– Round Robin (RR)

– Maximum C/I (MAXC/I)

– Proportional Fair (PF)

• Some basic scheduler– Round Robin (RR)

– Maximum C/I (MAXC/I)

– Proportional Fair (PF)

By fast scheduling, HSDPA cell can allocate the available HSDPA power resource and code resource among users effectively, to improves the throughout.

• Scheduler may works

based on CDM and/or TDM– Channel condition

– Amount of data waiting in the queue

(delay)

– Fairness

– Cell throughout, etc

• Scheduler may works

based on CDM and/or TDM– Channel condition

– Amount of data waiting in the queue

(delay)

– Fairness

– Cell throughout, etc

Share and Scheduling of Shared Channel

The following fig describes scheduling processing for 4 users.

All codes reserved for HSDPA transmission

2ms

Max C/I Scheduling AlgorithmMax C/I Scheduling Algorithm

Features:1) Allocates channel to the user with max C/I in one TTI.

2) Provides the highest cell throughout, because channel is allocated to the user in the best radio condition .

3) It is not fair for the users located in areas of poor coverage. By max C/I algorithm, the system hardly allocate channel for users under pool signal condition.

Adaptive Modulation and Coding (AMC)Adaptive Modulation and Coding (AMC)

• AMC is based on channel quality

– Adjust data rate

• Good channel condition – higher rate

• Poor channel condition – lower rate

– Adjust code rate

• Good channel condition – higher rate (e.g. 3/4

code)

• Poor channel condition – lower rate (e.g. 2/4

code)

– Adjust modulation scheme

• Good channel condition – 16QAM

• Poor channel condition – QPSK

• Channel Quality Feedback (CQI)

– UE measures channel quality (SNR) and reports to

Node B every 2ms or longer time.

– Node-B chooses modulation scheme, Transport Block

size and data rate based on CQI.

• AMC is based on channel quality

– Adjust data rate

• Good channel condition – higher rate

• Poor channel condition – lower rate

– Adjust code rate

• Good channel condition – higher rate (e.g. 3/4

code)

• Poor channel condition – lower rate (e.g. 2/4

code)

– Adjust modulation scheme

• Good channel condition – 16QAM

• Poor channel condition – QPSK

• Channel Quality Feedback (CQI)

– UE measures channel quality (SNR) and reports to

Node B every 2ms or longer time.

– Node-B chooses modulation scheme, Transport Block

size and data rate based on CQI.

Throughput ~ SIR RelationshipThroughput ~ SIR Relationship

AMC could improve radio bandwidth and fit for high speed radio transmission.

HSDPA ModulationQPSK16QAM

Modulation SchemeModulation Scheme

AMC Processing Flow

UE measure CPICH strengthUE reports the signal quality by CQI

(channel quality indicator)Node B may filter and rectify CQI report to

obtain actual CQIDetermine the channel number, transmit

power and modulation scheme, etc, based on CQI, transmit data volume, available power and code.

Hybrid Automatic Repeat Request (HARQ)Hybrid Automatic Repeat Request (HARQ)

Tranditional ARQ–decode received transport block

–detect if there is CRC error in decoded transport bolck

–If there is CRC error

•discard error block

•Request retransmission

Tranditional ARQ–decode received transport block

–detect if there is CRC error in decoded transport bolck


•discard error block


Hybrid ARQ–decode received transport block

–Detect if there is CRC error in decoded transport bolck


•Store error block(no discard)


•Combine the currently received retranmission with the previous failed decodes.

Hybrid ARQ–decode received transport block

–Detect if there is CRC error in decoded transport bolck


•Store error block(no discard)


•Combine the currently received retranmission with the previous failed decodes.

Soft Combine

Increment redundancy

HARQ helps minimize retransmission time and increase cell throughout.

Combined HARQ

Block1

Block1

Block1?

Block1

Block1

Block2

HARQ Concept• HARQ is a technique that transmitter sends new set of

check bits if the previous transmission failed (NACK) while receiver buffers the failed decodes for soft combining with future retransmissions.

• The RV parameter indicates different code bit transmit in IR buffer. Different RV parameter configuration supports:

– CC (Chase Combining): retransmit the same coded data

– PIR (Partial Incremental Redundancy): transmit systematic bits first

– FIR (Full Incremental Redundancy): transmit parity bits first

HARQ Gain

One retransmission gain for different retransmission scheme

Code Rate 1/3 1/2 2/3 3/4

CC Gain (dB) 3.0 3.0 3.0 3.0

PIR Gain (dB)

3.1 3.3 3.6 6.5

FIR Gain (dB)

3.1 3.5 4.3 8.4

FIR scheme will transmit the check bits first, it has effective average coded bits after retransmission. Especially for high code rate, the HARQ gain is very evidence.

Channel ConceptDown Link

WCDMA Downlink (FDD) – Rel.’99

BCCHBroadcast Control Ch.

PCCHPaging Control Ch.

CCCHCommon Control Ch.

DCCHDedicated Control Ch.

DTCHDedicated Traffic Ch. N

BCHBroadcast Ch.

PCHPaging Ch.

FACHForward Access Ch.

DCHDedicated Ch.

P-CCPCH(*)Primary Common Control Physical Ch.

S-CCPCHSecondary Common Control

Physical Ch.

DPDCH (one or more per UE) Dedicated Physical Data Ch.

DPCCH (one per UE)Dedicated Physical Control Ch.Pilot, TPC, TFCI bits

SSCi

Logical Channels(Layers 3+)

Transport Channels(Layer 2)

Physical Channels(Layer 1)

DownlinkRF Out

DPCH (Dedicated Physical Channel)One per UE

DSCHDownlink Shared Ch.

CTCHCommon Traffic Ch.

CPICHCommon Pilot Channel

Null Data

Data Encoding

Data Encoding

Data Encoding

Data Encoding

Data Encoding

PDSCHPhysical Downlink Shared Channel

AICH (Acquisition Indicator Channel)

PICH (Paging Indicator Channel )

Access Indication data

Paging Indication bits

AP-AICH(Access Preamble Indicator Channel )

Access Preamble Indication bits

CSICH (CPCH Status Indicator Channel )

CPCH Status Indication bits

CD/CA-ICH (Collision Detection/Channel

Assignment )

CPCH Status Indication bits

S/P

S/P

Cch

S/P

S/P

S/P

S/P

S/P

S/P

S/P

S/P

Cell-specificScrambling

Code

I+jQI/Q

Modulator

Q

I

Cch

Cch

Cch

Cch

Cch

Cch

Cch

Cch 256,1

Cch 256,0

GS

PSC

GP

Sync Codes(*)

* Note regarding P-CCPCH and SCH

Sync Codes are transmitted only in bits 0-255 of each timeslot;P-CCPCH transmits only during the remaining bits of each timeslot

Filter

Filter

Gain

Gain

Gain

Gain

Gain

Gain

Gain

Gain

Gain

Gain

SCH (Sync Channel)

DTCHDedicated Traffic Ch. 1

DCHDedicated Ch.

Data Encoding

MUX

MUX

CCTrCH

DCHDedicated Ch.

Data Encoding

60

Downlink Logical Channels (L3)• Control Logical Channels

• BCCH (Broadcast Control Channel)

– Broadcasts cell site and system information to all UE

• PCCH (Paging Control Channel)

– Transmits paging information to a UE when the UEs location is unknown

• CCCH (Common Control Channel)

– Transmits control information to a UE when there is no RRC Connection

• DCCH (Dedicated Control Channel)

– Transmits control information to a UE when there is a RRC Connection

• Traffic Logical Channels• CTCH (Common Traffic Channel)

– Traffic channel for sending traffic to a group of UEs.

• DTCH (Dedicated Traffic Channel)

– Traffic channel dedicated to one UE

61

Downlink Transport Channels (L2)• Common Transport Channels

• BCH (Broadcast Channel)– Continuous transmission of system and cell information

• PCH (Paging Channel)– Carries control information to UE when location is unknown– Pending activity indicated by the PICH (paging indication channel)

• FACH (Forward Access Channel)– Used for transmission of idle-mode control information to a UE– Also used for some user data

• Dedicated Transport Channels

• DCH (Dedicated Channel)– Carries dedicated traffic and control data to one UE– Used for BLER measurements

62

Downlink Physical Channels (L1)• Common Physical Channels

– P-CCPCH Common Control Physical Channel (Primary)• Broadcasts cell site information

• Timing reference for all DL

– SCH Synchronization Channel• Fast Synch. codes 1 and 2; time-multiplexed with P-CCPCH

– S-CCPCH Common Control Physical Channel (Secondary)

• Transmits idle-mode signaling and control information to UEs

– CPICH Common Pilot Channel

• Dedicated Physical Channels

– DPDCHDedicated Downlink Physical Data Channel– DPCCHDedicated Downlink Physical Control Channel

• Transmits connection-mode signaling and control to UEs

63

Downlink Physical Channels…• Indicator Physical Channels

– AICH (Acquisition Indicator Channel)• Acknowledges that BS has acquired a UE Random Access

attempt• (Echoes the UEs Random Access signature)

– PICH (Page Indicator Channel)• Informs a UE to monitor the next paging frame

DPCCH: 15 kb/sec data rate, 10 total bits per DPCCH slot

PILOT: Fixed patterns (3, 4, 5, 6, 7, or 8 bits per DPCCH slot)

TFCI: Transmit Format Combination Indicator (0, 2, 3, or 4 bits)

FBI: Feedback Information (0, 1, or 2 bits)

TPC: Transmit Power Control bits (1 or 2 bits); power adjustment in steps of 1, 2, or 3 dB

Channel ConceptUP Link

WCDMA Uplink (FDD) – Rel ’99

Logical Channels(Layers 3+)

Transport Channels(Layer 2)

Physical Channels(Layer 1)

UplinkRF Out

UEScrambling

Code

I+jQ I/QMod.

Q

I

Chc

I

Filter

Filter

CCCHCommon Control Ch.

DTCH (packet mode)Dedicated Traffic Ch.

RACHRandom Access Ch.

PRACHPhysical Random Access Ch.

DPDCH #1Dedicated Physical Data Ch.

CPCHCommon Packet Ch.

PCPCHPhysical Common Packet Ch.

Data Coding

Data Coding

DPDCH #3 (optional)Dedicated Physical Data Ch.

DPDCH #5 (optional) Dedicated Physical Data Ch.




Q

DPCCHDedicated Physical Control Ch.

Pilot, TPC, TFCI bits

Chd

Gc

Gd

j

Chd,1 Gd

Chd,3 Gd

Chd,5 Gd

Chd,2 Gd

Chd,4 Gd

Chd,6 Gd

Chc Gd

Chc

Chd

Gc

Gd

j

RACH Control Part

PCPCH Control Part

j

DCCHDedicated Control Ch.

DTCHDedicated Traffic Ch. N

DCHDedicated Ch.

Data Encoding

DTCHDedicated Traffic Ch. 1

DCHDedicated Ch.

Data Encoding M

UX

CCTrCH

DCHDedicated Ch.

Data Encoding

66

Uplink Logical Channels (L3)

• Control Logical Channels

• CCCH (Common Control Channel)

– Transmits control information to a UE when there is no RRC Connection

• DCCH (Dedicated Control Channel)

– Transmits control information from a UE when there is a RRC Connection

• Traffic Logical Channels

• CTCH (Common Traffic Channel)

– Traffic channel for sending traffic to a group of UEs

• DTCH (Dedicated Traffic Channel)

– Traffic channel dedicated from one UE

67

Uplink Transport Channels (L2)

• Common Transport Channels

• RACH - Random Access Channel– Carries access requests, control information, short data

» Uses only open-loop power control

» Subject to random access collisions

• Dedicated Transport Channels

• DCH - Dedicated Channel– Carries dedicated traffic and control data from one UE

– Used for BLER measurements

68

Uplink Physical Channels (L1)• Common Physical Channels

– PRACHPhysical Random Access Channel• Used by UE to initiate access to BS

• Dedicated Physical Channels

– DPDCHDedicated Uplink Physical Data Channel – DPCCHDedicated Uplink Physical Control Channel

• Transmits connection-mode signaling and control to BS

69

WCDMA Physical Channels

BaseStation

(BS)

UserEquipment

(UE)

P-CCPCH- Primary Common Control Physical ChannelSCH - Synchronization Channel

CPICH - Common Pilot Channel

Channels broadcast to all UE in the cell

DPDCH - Dedicated Physical Data Channel

DPCCH - Dedicated Physical Control Channel

Dedicated Connection Channels

PICH - Page Indicator Channel

Paging Channels

S-CCPCH - Secondary Common Control Physical Channel

AP-AICH - Acquisition Preamble Indicator Channel

CD/CA-AICH - Collision Detection Indicator Channel

CSICH - CPCH Status Indicator Channel

PRACH - Physical Random Access Channel

AICH - Acquisition Indicator Channel

Random Access and Packet Access Channels

Channel ConceptHSDPA

HSDPA Relevant Physical Channel

Three new HSDPA Physical Channel

For each HS-DPCCH, SF=256

Each H has one HS-DPCCH.

For each HS-SCCH, SF=128

Each cell is assigned up to 4 HS-SCCH (limited by UE capability)

For each HS-PDSCH, SF=16

HSDPA Channel Mapping

Associated Channel - DPCH

There is another dedicated physical channel named DPCH for each HSDPA user. DPCH is also called associated channel in HSDPA. It is used for signaling transport and power control.

Normally DPCH doesn’t carry service data, only sometimes carry real time services such as AMR (the user setup multiple RAB: CS+PS).

Node B

UE

HS-PDSCH HS-SCCH DPCH HS-DPCCH

“Associated”? Or “Concomitant”?

HSDPA Physical Channel (HS-SCCH)

HS-SCCH and HS-PDSCH are downlink shared channel shared by all users. How can users

know when and on which channel my data is

transported?

HS-SCCH and HS-PDSCH are downlink shared channel shared by all users. How can users

know when and on which channel my data is

transported?

HS-SCCH is like soldiers holding flags at the first row of queue. UE keeps on monitoring the HS-SCCH channels to identify any HS-PDSCH subframes addressed to it on the sets of HS-PDSCH channels. Upon receiving an HS-PDSCH subframe for the UE, the UE physical layer will demodulates the subframe, otherwise do nothing.

HS-SCCH is like soldiers holding flags at the first row of queue. UE keeps on monitoring the HS-SCCH channels to identify any HS-PDSCH subframes addressed to it on the sets of HS-PDSCH channels. Upon receiving an HS-PDSCH subframe for the UE, the UE physical layer will demodulates the subframe, otherwise do nothing.

Physical Channel Slot Format (HS-SCCH)

• HS-SCCH Slot Format Features– 3 slots in one TTI (2ms)

– SF=128, QPSK modulation

– Maps user’s seven data attributes, including Xue, Xccs, Xms, Xrv, Xtbs, Xhap and Xnd;

– UE demodulates HS-SCCH and find out the received data addressed to the UE. Then UE demodulates the HS-PDSCH.

– In theory, one cell can configure up to 15 HS-SCCH. But now commercial UE can only monitor up to 4 HS-SCCH channels simultaneously. So one cell only configure up to 4 HS-SCCH channels.

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, 40 bits

DataN data 1 bits

HS-SCCH subframe: T = 2 ms

Physical Channel Slot Format (HS-PDSCH)

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, M*10*2 k bits (k=4)

Data N data 1 bits

1 subframe: T f = 2 ms

HS-PDSCH Slot Format Attributes:3 slots in one TTI (2ms)

Fixed spreading factor SF16

QPSK or 16QAM modulation

Only carry user data

UE may be assigned multi channelization codes to support multi-code transport depending on UE capability.

Physical Channel Slot Format (HS-DPCCH)

• Uplink HS-DPCCH– TTI 2ms (3 slots), SF 256, Fixed rate of 15Kbps,carry 2 types of HSDPA uplink physical layer

signaling: ACK/NACK and CQI.

– ACK and NACK notifies the NodeB if UE has received correct downlink data or not. The field defines like this:1-Nack, 0-Ack

– CQI is a metric that reflects physical channel quality indicator based on CPICH, and reported by period ranging from 0, 2ms…. to 160ms (0 means no transmission). Usually the period is 2ms (one TTI).

– ACK/NAK and CQI having different function may be controlled independently by different parameters .

– ACK/NACK/CQI could be configured to repeat up to 4 times to improve TSTD gain.

Subframe #0 Subframe # Subframe #4

HARQ-ACK CQI

One radio frame T f = 10 ms

One HS-DPCCH subframe (2 ms)

2 T slot = 5120 chips T slot = 2560 chips

Physical Channel Timing

• Start of HS-SCCH is aligned with the start of P-CCPCH, HS-PDSCH subframe is transmitted two slots after the associated HS-SCCH subframe. UE demodulates HS-PDSCH subframe according to HS-SCCH.

• HS-SCCH and PDSCH are common channels, so there are not timing between HS-SCCH/PDSCH and DPCH.

HS-SCCH

HS-PDSCH

3 slots = 2 ms

DPCH

DPCH

Radio frame with (SFN modulo 2) = 0 P-CCPCH

2 slots

3 slots = 2 ms

Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot

15 slots = 10 ms

Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4

Radio frame with (SFN modulo 2)=1

10 ms

Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4

HS-DPCCH

3 slots = 2 ms

~7.5 slots

UE Capacity Category( for reference)

HSDPA Physical Channel Transmit Power

• PHSDPA(HSDPA total transmit power) ＝ PHS-PDSCH + PHS-SCCH

• The HS-PDSCH transmit power is adjusted by Node B

according to the following factors:– CQI

– Amount of data to be transmitted

– Available power for HS-PDSCH

– Available code resource for HS-PDSCH

• HS-SCCH transmit power may use:– Fixed power transmission (outdoor 5%, indoor 3% of the total power)

– A fixed power offset between HS-SCCH and DL associated channel (PDCH).

HS-PDSCH transmit power is usually bigger than the PDCH channel to keep a

proper transmit power.

• HS-DPCCH transmit power has a power offset based on UL

DPCH.– Slot carrying HARQ-ACK/NACK or CQI may be set different power offset.

HSDPA – Channel MappingWhen RAB is mapped onto HS-DSCH, DPCH is needed to transport UL RLC AM information and possible UL data, no matter there is UL data to transport.

The following figure describes that DL TRB is carried on HS-DSCH SRB and SRB or UL service is carried on DCH. In soft handover, there may be one or more DCH, but only one HS-DSCH.

Channel Switching

Capability• Optimizes the utilization of radio resources, by switching UE’s to the

most suitable transport channel based on traffic volume (throughput), radio resources availability, radio conditions and mobility

Impacting features• Admission Control

• Congestion Control

• Soft Handover

Channel type switching

Release dedicated channel

Random-AccessRequest

Random-Access Channel

Packet Packet Packet

Dedicated Channel

TTime-out

Switch to common

Switch todedicated

Random-AccessRequest

User 1 User 2

Channel rate switching

Distancefrom RBS

orLoad in the cell

Down-switche.g. 384 128 64 Kbps

Up-switche.g. 64 128 384 Kbps Bit rate

Distancefrom RBS

orLoad in the cell

Overview of trigger mechanisms

Down-switch from dedicated to common channel to resolve congestion

Admission Control

Down-switch from one dedicated channel to another, e.g. from 64/384 to 64/128 to free up radio resources

Channel SwitchingAlgorithms

Congestion Control

Soft Handover

Down-switch from 64/384 or 64/128 to 64/64 if Admission Control denies adding a radio link to the Active Set

ChannelSwitching

Down/up switch based on coverage and user activity

Single RAB State Transitions

Idle Mode

RACH/FACH(max. 32 kbps)

Common Channel (Cell_FACH)

Cell_DCH 64/64 kbps UL/DL



Dedicated Channel (Cell_DCH)

Connected Mode1. Common to Dedicated

1

2. Dedicated to dedicatedSingle RAB

2

2 2

2

3. Dedicated to common

3

4. Common to Idle Mode

4

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