176552343-HSDPA-Description-2008-11-30

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Huawei Technologies Co., Ltd. provides customers with comprehensive technical support and service. Forany assistance, please contact our local office or company headquarters.

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Copyright © Huawei Technologies Co., Ltd

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HSDPA Description 1 HSDPA Change History

Issue 03 (2008-11-30) Huawei Proprietary and Confidential


1-1

1 HSDPA Change HistoryHSDPA Change History provides information on the changes between different document

versions.

Document and s

T p t versions

Product Version

able 1-1 Document and roduc

Document Version RAN Version RNC Version NodeB Version

03 (2008-11-30) 10.0 V200R010

V100R010

V200R010

02 (2008-07-30) 10.0 V200R010C01B061

V200R010C01B041

V100R010C01B050

01 (2008-05-30) 10.0 V200R010C01B051 V100R010C01B049

V200R010C01B040

Draft (2008-03-20) 10.0 V200R010C01B050 V100R010C01B045

Ther

Feature change: refers to the change in the HSDPA feature of a specific product version.

Editorial change: refers to changes in information that has already been included, or the

ion.

03 (2008-11-30

This is the document for the second commercial release of RAN10.0.

Compared with 01(2008-07-30) of RAN10.0, issue 03 (2008-11-30) of RAN10.0 incorporates

t ib following table.

e are two types of changes.

addition of information that was not provided in the previous vers

)

he changes descr ed in the

Change Type Change Description Parameter Change

Feature change None. None


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HSDPA Description

1-2 Huawei Proprietary and Confidential


Issue 03 (2008-11-30)


The description of CQI

adjustment algorithm is removed.

None.

Mapping of Service to HSDPA is Noneadded to 4.7 Other HSDPARelated Algorithm.

HS-DPCCH Preamble is added None

to 4.7 Other HSDPA RelatedAlgorithm.

Editorial change

er Iur is added to 4.7

Other HSDPA RelatedAlgorithm.

NoneHSDPA Ov

02 (2008-07-30)

release of RAN10.0.

C 1( issue 02 ( .0 incorporates

t ib .

This is the document for the first commercial

ompared with 0

he changes descr

2008-05-30) of RAN10.0,

ed in the following table

2008-07-30) of RAN10


Feature change None. nged toed as

hs Discard timer

Switch

re listed as

ntrol switch

fo

t

try timer is modified to HRetry Timer Length

The parameters that are cha be non-configurable are list

follows: MAC-

The added parameters are listed as

follows:

Hsdpa

The deleted parameters a

follows:

flow co

The parameters modified are listed as

llows:

SPI weight is modified to Weighof SPI

H Re

Editorial change A parameter list is added. Seechapter 5 HSDPA Parameters.

None.

01 (2008-05-30)

N10.0.This is the document for the first commercial release of RA


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3 HSDPA Principles

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HSDPA Description



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Figure 3-2 HSDPA protocol architecture with the MAC-c/sh

The differences between the HSDPA protocol architecture and the R99 protocol architectureare as follows:

RLC and MAC-d are unchanged.

The HS-DSCH FP is added to handles the data transport from SRNC to CRNC if the Iur

interface is involved and the data transport between CRNC and NodeB. In R99, it is theDCH FP that handles such data transport.

A new entity called MAC-hs is added at the MAC layer of both UE and NodeB. TheMAC-hs handles new functions, such as HARQ and HS-DSCH scheduling.

There are two types of MAC protocol configurations on the UTRAN side:

− Configuration with the MAC-c/sh: The MAC-c/sh implements flow control betweenMAC-d, MAC-c/sh, and MAC-hs.

− Configuration without MAC-c/sh: The MAC-hs and HS-DSCH FP implement flowcontrol between MAC-hs and MAC-d over Iub/Iur.

3.2 HSDPA Physical layer

At the physical layer of the UTRAN side, the data streams (transport block or transport blockset) from the MAC layer are channel coded and mapped onto physical channels. There are

three types of HSDPA physical channels, that is, High Speed Shared Control Channel

(HS-SCCH), High Speed Physical Downlink Shared Channel (HS-PDSCH), and High SpeedDedicated Physical Control Channel (HS-DPCCH).

Overview of HSDPA Physical Layer

HSDPA Physical Channels

Timing of HS-DSCH Related Physical Channels

3.2.1 Overview of HSDPA Physical Layer

The basic downlink channel configuration for a UE consists of one or several HS-PDSCHs,

one associated DPCH, and several HS-SCCHs. In any given TTI, a UE can use a maximum ofone HS-SCCH.


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Figure 3-7 Timing of the HS-SCCH and HS-PDSCH

Timing of the Uplink DPCCH, HS-DPCCH, and HS-PDSCH on the UE Side

Figure 3-8 shows the timing of the uplink Dedicated Physical Control Channel (DPCCH),

HS-PDSCH, and HS-DPCCH at the UE.

After receiving an HS-PDSCH subframe, the UE sends a feedback about 19,200 chips later.

Figure 3-8 Timing of the uplink DPCCH, HS-DPCCH, and HS-PDSCH at the UE

3.3 HSDPA MAC-hs Layer

This describes the following:

MAC-hs on the UTRAN Side

MAC-hs on the UE Side

HARQ Protocol


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3.3.1 MAC-hs on the UTRAN Side

The MAC-hs on the UTRAN side manages the physical resources allocated to HS-DSCH.

The MAC-hs consists of the following four different functional entities:

Flow control

Scheduling

TFRC selection: Transport Format and Resource Combination selection

HARQ: Hybrid Automatic Repeat reQuest

Figure 3-9 shows the MAC-hs architecture on the UTRAN side.

Figure 3-9 MAC-hs architecture on the UTRAN side

The flow control entity controls the HSDPA data flow between RNC and NodeB.

Purpose: to reduce the transmission time of HSDPA data on the UTRAN side and to

reduce the data discarded and retransmitted when the Iub interface or Uu interface iscongested.

The transmission capabilities of the Uu interface and Iub interface are taken into accountin a dynamic manner in the flow control. For details of flow control, refer to 4.2 HSDPAFlow Control in NodeB.

The scheduling entity handles the priority of the queues and schedules the priority queues or

NACK HARQ processes of the HS-DSCH UEs in a cell to be transmitted on the HS-DSCH

related physical channels in each TTI.


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The reordering entity reorders the received MAC-hs PDUs according to theirtransmission sequence number (TSN) and the TSN may be out of sequence because of parallel HARQ processes. For each queue ID, one reordering entity is configured on theUE.

The disassembly entity extracts the MAC-d PDUs from the MAC-hs PDUs and deliversthem to the higher layer.

3.3.3 HARQ Protocol

The HARQ protocol is based on the stop and wait ARQ scheme, and supports chasecombining and incremental redundancy combining.

Figure 3-11 shows the principle of HARQ protocol.

Figure 3-11 Principle of the HARQ protocol

The following topic describes the protocol by taking one UE as an example.

In a given TTI, the NodeB initiates data transmission of a new transport block (TB) tothe UE.

Before transmission over the Uu interface, the TB is channel coded at the physical layer,where systematic and parity bits are generated.

Because of errors in the Uu interface, the receiver UE cannot decode the TB successfully.

Therefore, it generates an HARQ-NACK message and sends it to the NodeB through the

uplink HS-DPCCH. The NodeB retransmits the TB after receiving the NACK from the UE.

The channel coding bits in original transmission and subsequent retransmissions are buffered on the UE and then are soft-combined to improve the probability ofsuccessfully decoding the TB.

The ARQ combining scheme is based on incremental redundancy. Different sets of channelcoding bits of the TB can be chosen in the retransmission. Chase combining is considered to

be a particular case of incremental redundancy, in which the same systematic and parity bitsas those used in the initial transmission are retransmitted.

Compared with retransmission at the RLC layer, HARQ has the following benefits:


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The round trip time at the physical layer is approximately 12 ms, much shorter than thatat the RLC layer. The round trip time at the RLC layer may reach hundreds ofmilliseconds.

Soft combining improves the efficiency of the physical layer resource.

The round trip time at the physical layer is 12 ms. Therefore, it is necessary for one UE tohave multiple parallel instances (HARQ processes) of the stop and wait HARQ protocol toincrease the Uu interface throughput.

One issue in the receiver caused by multiple HARQ processes is that, in a specific time

window, the TBs may arrive out of sequence. Therefore, it is necessary to have reorderingfunctionality on the receiver side.


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4.1.1 HSDPA-Related Algorithms Involved in a Call Process

Figure 4-1 HSDPA-Related Algorithms Involved in a Call Process

Step 1 When a cell is set up, the initial allocation of power and codes for HSDPA are allocated. Afterthat, the power and code resource available for HS-DSCHs in a HSDPA cell are dynamically

adjusted by the algorithms of 4.5 HSDPA Power Resource Management and 4.6 HSDPA

Code Resource Management. R99 and HSDPA can dynamically share the resource of the cell

in this way.

Step 2 When one user initiates a service at the beginning of RAB setup procedure, the channelmapping algorithm determines whether the RAB should be mapped onto the HS-DSCH orDCH depending on the service Qos attributes. QoS of the service is mapped to the parameters

of radio bearer, such as SPI, discard timer, and GBR for HS-DSCH bearer. For details ofradio bearers, refer to Mapping of Signaling and Traffic onto Transport Channels and

Mapping of Combined Services onto Transport Channels (in Radio Bearers).

RAB is set up after admission control (in Load control). Admission control determineswhether the system resources are enough to accept a new user's access request. Data transport

begins after the RAB is set up. Data transport of HS-DSCH bearer is controlled by thefunctions such as 0

Step 3 HSDPA Flow Control in NodeB, 4.3 HSDPA MAC-hs Scheduling, and 4.4 HSDPA TFRCSelection.

Step 4 During the HS-DSCH transport, the movement of the user will trigger the mobilitymanagement. For example, the best cell change occurring in the active set may triggerHS-DSCH serving cell change or channel switching between HS-DSCH and DCH. For details,


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refer to Intra-Frequency Handover, Inter-Frequency Handover, and Inter-RAT HandoverDescription.

Step 5 Load control also manages the overload situation besides admission control. Load controlneeds to reserve enough resource to ensure the QoS of the service. HS-DSCH scheduling

provides the measurement of GBP, PBR, and DL transmit power and takes it as the input toload control.

Step 6 After HSDPA is introduced, there is one more UE state, that is, CELL_DCH (HS-DSCH).Channel switching between HS-DSCH and DCH and channel switching between HS-DSCHand FACH are introduced. The channel switching may be triggered by mobility or change of

traffic volume. For details, refer to 4.7.6 HSDPA Channel Switching.

----End

4.1.2 QoS Management of Services Mapped on HSDPA

QoS Requirements of Different Services

Different services, such as SRB, IMS signaling, VoIP, streaming, interactive, and background

services, can be mapped on HSDPA.

The requirements for the QoS of different services are as follows:

IMS/SRB: Signaling has a high requirement for transmission delay. If the requirementcannot be met, the service may be affected. For example, an SRB delay may lead to a

handover delay. The average rate of signaling is lower than 20 kbit/s.

VoIP: The VoIP service is highly delay sensitive. The end-to-end delay of a voice frameshould be shorter than 250 ms. The tolerant frame error rate is about 1%. The average

rate of the VoIP service with the header compressed is about 20 kbit/s. Streaming: The streams at the receiver end should be continuous. Compared with VoIP,

the streaming service has a relatively low delay sensitivity, because a buffer that canavoid jitter for several seconds is configured at the receiver end. When the rate of the

streaming service is equal to or higher than the GBR, the QoS can be guaranteed.

BE (background and interactive): The data rate at the service source end can reach a highvalue, for example, several Mbit/s during a burst. The BE service has a low requirementfor transmission delay but has a high requirement for reliable transmission.

QoS Parameters Mapped onto the MAC-hs Layer of the NodeB MAC-hs Discard timer: An MAC-d PDU in an MAC-hs queue is discarded if the waiting

time exceeds the length of this discard timer. It is an optional IE on the Iub interface. Forthe VoIP service, the timer is set to 100 ms. For the BE and streaming services, the timer

may not be set. For an MAC-hs queue configured with the discard timer, the schedulershould send out the MAC-d PDUs before expiry of the timer.

Scheduling Priority Indicator (SPI): This parameter specifies the scheduling priority ofan MAC-hs queue. The priority is derived from the Traffic Class, Traffic Handling

Priority, and User Priority that are mapped onto this queue. For details, refer to Table

4-2.

The service-oriented control algorithms are configured on an SPI basis on the NodeB

side. For example, the QoS-oriented algorithms, such as the flow control algorithm,scheduling algorithm, CQI adjustment algorithm, and maximum number of HARQ process retransmissions, are all configured on an SPI basis on the NodeB side. Fordetails, refer to Table 4-3.


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User priority Error 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3

The traffic class, user priority, and THP determine only one SPI. The default mapping isdescribed in the following table, where user priority 1 corresponds to Gold, 2 corresponds toSilver, and 3 corresponds to Copper.

Table 4-2 Default mapping of traffic class, user priority, and THP to SPI

User Priority THP SPITraffic Class

SRB signaling No ARP None 15

IMS signaling No ARP None 14

1 None 13

2 None 13

Conversational (VoIP)

3 None 13

1 None 12

2 None 11

Streaming

3 None 11

1 1 10

1 2 9

1 3 to 15 8

2 1 7

2 2 6

2 3 to 15 5

3 1 4

3 2 3

Interactive

3 3 to 15 2

1 None 8

2 None 5

Background

3 None 2

SPI 0 and SPI 1 are not used.


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Figure 4-3 Structure of flow control algorithm

NodeB and RNC can provide flow control functions. In NodeB, there are two types of flow

control policies.

Flow control free

Dynamic flow control

Dynamic flow control has three methods.

No shaping

Shaping without adaptive Iub bandwidth.

Shaping with adaptive Iub bandwidth

4.2.2 Signaling of HSDPA Flow Control

The signaling of HSDPA flow control is implemented through capacity request and allocation.

The following figure shows the signaling procedure for HSDPA capacity request andallocation.

Figure 4-4 Signaling procedure for HSDPA capacity request and allocation

The signaling procedure is as follows:

The CRNC sends an HS-DSCH Capacity Request to the NodeB, when some RLC PDUs

are pending in the RLC entity and the credits (indicated in the latest HS-DSCH CapacityAllocation message) are used up. If there is no RLC PDU but the allocated capacity is

greater than zero, the RNC also sends a Capacity Request to the NodeB, indicating that

the NodeB can stop the capacity allocation.


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HS-DSCH Credits: number of MAC-d PDUs that a CRNC can transmit during anHS-DSCH Interval granted in the HS-DSCH CAPACITY ALLOCATION control frame.

Maximum MAC-d PDU Length: maximum PDU size among the MAC-d PDU sizesconfigured in the NBAP messages.

HS-DSCH repetition period: number of subsequent intervals during which the HS-DSCHCredits IE granted in the HS-DSCH CAPACITY ALLOCATION control frame can beused and the value 0 means that there is no limit to the repetition period.

4.2.3 Flow Control Policies

Generally, the NodeB allocating the capacity to a MAC-hs queue considers the output rate onthe Uu interface and Iub available bandwidth. For different QoS requirements, the NodeB

uses different flow control policies, namely, flow control free and dynamic flow control.

The flow control policies are based on SPI and are configured through the Flow ControlAlgorithm Switch parameter. For details of recommended policy of flow control based on

SPI, refer to 4.1.2 QoS Management of Services Mapped on HSDPA.

Flow Control Free Policy

After the HS-DSCH bearer is set up, the NodeB sends a capacity allocation message to the

RNC, indicating that the DL traffic of the new MAC-hs queue is not limited and the RNC

MAC-d can send data as much as required. The allocation keeps unchanged for the service.

The policy of no flow control policy is applied only to VoIP, IMS, and SRB, for these services

are delay sensitive and have a relative low rate.

Dynamic Flow Control Policy

Dynamic flow control is mainly applied to MAC-hs queues of BE service, for theses servicesare not delay sensitive, the rate varies in a wide range, and will reach a high rate during a

burst.

Dynamic flow control is also applied to MAC-hs queues of streaming service, for streaming

service has a relative high rate and may result in congestion on Uu.

This section mainly describes the method of shaping with adaptive Iub bandwidth of dynamicflow control policy. Other two methods are similar to shaping with adaptive Iub bandwidth,

except that the functions of shaping or Iub adaptive bandwidth is ignored.

Dynamic flow control process of Shaping with adaptive Iub bandwidth is as follows:

Step 1 The congestion status of the transport network is reflected to NodeB through DRT and FSN.The NodeB adaptively adjusts the Iub bandwidth available for HSDPA based on the

congestion detection.

Step 2 Depending on the available bandwidth and rate on air interface, the NodeB allocates bandwidth to HSDPA users and performs traffic shaping (Iub shaping) to avoid congestion

and packet loss over the Iub interface.

Step 3 The RNC limits the flow of HS-DSCH data frames for each MAC-hs queue according to theHS-DSCH capacity allocation.

----End


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Figure 4-7 Dynamic flow control algorithm structure

Dynamic flow control policy consists of the following modules:

Adaptive capacity allocation

NodeB adaptively allocates capacity to an MAC-hs queue based on its rate on air

interface.

Capacity means how much data RNC can send to NodeB in an interval.

Congestion control on Iub

The total flow of all the MAC-hs queues should not exceed the available Iub bandwidthto avoid congestion on Iub.

RNC provides the function of backpressure to avoid Iub congestion. For details, see

Transmission Resource Management Description.

NodeB provides the following functions to avoid Iub congestion:

− Adaptive adjustment of Iub bandwidth

NodeB periodically detects Iub congestion and adaptively adjusts the available Iub

bandwidth according to the Iub state.

− Iub shaping

Iub shaping is used to allocate Iub bandwidth to every MAC-hs queue based on the

available Iub bandwidth and ensure the total flow of the queues does not exceed theavailable Iub bandwidth. Thus, congestion control is achieved on the Iub interface,which increases the bandwidth usage and avoids overload.

Dynamic flow control policy is configured through the Hsdpa Switch.

If the switch is set to STATIC_BW_SHAPING, based on the configured Iub bandwidthand the bandwidth occupied by R99 users, traffic is allocated to HSDPA users when the physical bandwidth restriction is taken into account.


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If the resource on the Iub interface is the bottleneck, the bandwidth allocation is based onthe rate on the Uu interface and the available Iub bandwidth.

− The algorithm considers the following factors of the MAC-hs queues: the bit rateallocated by Adaptive Capacity Allocation Based on Uu Rate, NodeB buffer

occupancy, RNC buffer occupancy, and the bottleneck bandwidth available forHSDPA on the Iub interface from Adaptive Adjustment of Available HSDPABandwidth.

− First, Iub resource for GBR is allocated. That is, the algorithm first considers the

basic requirements for guaranteeing the user experience.

− Then, the algorithm considers the requirement for user differentiation. For all theusers in the cell, the scheduler intends to allocate the Iub resource in proportion totheir Weight of SPI, which is based on user priorities, eg. gold, silver and copper.

User priority differentiation is implemented when Iub is the bottleneck. The gold, silver, and

copper users obtain the resources in proportion to their priority weight factors (Weight of

SPI). In addition, the resources necessary for guaranteeing the GBR must be allocated first

before the resource allocation based on the proportion. For example, assume that Iub is the bottleneck, gold, silver and copper users are using

FTP service simultaneously. Then the Iub throughputs of gold, silver and copper usersare in proportion to the ratio of their SPI weights.

For another example, assume that the silver user is using HTTP service, the gold and thecopper user are using FTP service, and the silver user is reading the HTTP page. Then

the gold and copper users share the Iub resource and the Iub throughput of the gold andcopper users are in proportion to the ratio of their SPI weight.

4.2.6 Adaptive Adjustment of Available HSDPA Bandwidth

Because the NodeB dynamic bandwidth allocation is based on the service statistics, thedynamic bandwidth allocation does not reflects the real-time bandwidth occupancy and thetransport network quality. So it is necessary for NodeB to dynamically adjust the available

HSDPA bandwidth when the traffic throughput changes or the transport network quality

changes.

Adaptive adjustment of Iub bandwidth available for HSDPA is a part of the mechanism to

control the congestion on Iub. The algorithm detects the Iub congestion and adjusts the

available Iub bandwidth based on the detection result.

The adaptive adjustment of Iub bandwidth available for HSDPA takes effect only when the

parameter Hsdpa Switch is set to DYNAMIC_BW_SHAPING or is set to

BW_SHAPING_ONOFF_TOGGLE when congestion is detected.

The output of the algorithm is an input of HSDPA flow control algorithm.

Detection of Iub Congestion

The transmission delay is detected through DRT and frame loss is detected through FSN. FSNand DRT are taken from RNC to NodeB in HS-DSCH frame.

The algorithm periodically measures the congestion state based on transmission delay andframe loss.

Frame loss is calculated as follows:

Assume that for each MAC-d flow the HS-DSCH data frame must be delivered to the

MAC-hs layer in FSN sequence.


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If the frames are not in sequence, the frames are lost. Then the number of lost frames iscounted and the frame loss ratio at the Iub level in a specific time window is calculated.

Delay buildup is calculated as follows:

The HS-DSCH data frame transmission delay is the interval from the time when

HS-DSCH data frame is generated in the RNC (identified as DRT) to the time when theframe arrives at the NodeB MAC-hs layer, including the buffer time in Iub Transport Network Layer (TNL).

The delay buildup is the transmission delay increment comparing the sample delay withthe reference one obtained when Iub is free of congestion, as shown in Figure 4-8.

Figure 4-8 Calculating delay built-up

Periodically the Iub congestion state is differentiated into three levels.

Congestion due to delay buildup means that the delay buildup is larger than the Time

Delay.

Time Delay: is used to determine whether the Iub interface is congested because of

delay buildup. By default, this threshold is set to 20 ms. It can be adjusted on the basis ofthe delay jitter allowed on the transport network. Generally, the threshold is set to the

allowed delay jitter plus several milliseconds. If the threshold is too high, thetransmission on the Iub interface will be much delayed when the Iub interface is the

bottleneck. If the threshold is too low, the Iub interface will be regarded as congested bymistake. Thus, the transmission resource cannot be fully utilized.

Congestion due to frame loss that means the frame loss ratio is greater than the DiscardRate. Otherwise frame loss may be caused by an Iub bit error.

Discard Rate: is used to determine whether the Iub interface is congested because of

frame loss. Generally, frame losses due to bit error are less than those due to congestion.By default, the threshold is set to 5%. It can be adjusted on the basis of transport network

quality. The HS-DSCH frame error rate on the Iub interface within 300 ms can be areference. If the threshold is too high, the congestion on the Iub interface cannot be

alleviated in time. If the threshold is too low, the Iub interface will be regarded ascongested in the case of frame loss due to bit error. Thus, the Iub bandwidth cannot befully utilized.

Congestion released means that there is no congestion due to delay buildup and nocongestion due to frame loss.

The Time Delay and Discard Rate parameters can be set on NodeB LMT.


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Adjustment of Available Iub bandwidth

The algorithm actively adjusts the available Iub bandwidth based on the congestion detection.

If the Iub is in the congestion due to delay, the Iub bandwidth available for HSDPA is

decreased by a step in direct proportion to the delay buildup. If the Iub is in the congestion due to frame loss, the Iub bandwidth available for HSDPA

is decreased by a big step regardless of the delay buildup.

If the Iub is in the congestion released, the Iub bandwidth available for HSDPA is

increased by a smaller step, applying the strategy of increasing slowly, yet decreasingfast.

In a time window of tens of seconds, if consecutive "congestion released" is detected, theIub resource is identified as not the bottleneck. In this case, Iub bandwidth available for

HSDPA is equal to the bandwidth of Iub port minus the bandwidth of R99 services andflow control free services.

4.3 HSDPA MAC-hs Scheduling

One of the most important characters of HSDPA is that the HS-DSCH channel is a shared

channel among all HS-DSCH users in a cell. Each user is possible to be scheduled in every 2

ms TTI. The resource competition happens among the HSDPA users when the air interfaceresources available for HS-DSCH are limited. The MAC-hs scheduling algorithm isintroduced to select MAC-hs queues to be scheduled in each TTI to achieve considerable cell

throughput capability and to satisfy user experience.

MAX C/I, Round Robin (RR), and Proportional Fair (PF) are the most popular schedulingalgorithms in industry. The scheduling principles of these three algorithms are described in the

following table.

Table 4-4 HSDPA scheduling algorithms

Algorithm Factor Consideredin Algorithm

Scheduling Principle

MAX C/I CQI To select users according to the CQI value in

descending order. The radio channel quality is the

only factor considered in this algorithm and thereforethe fairness among users cannot be guaranteed.

RR Waiting time of data

buffered in theMAC-hs priorityqueue

To select users according to the waiting time of data

buffered in the MAC-hs priority queue in descendingorder. The waiting time is the only factor consideredin this algorithm and therefore the fairness among

users can be guaranteed but the cell capacitydegrades because the channel quality is not takeninto account.

PF CQI, To select users according to the value of R/r indescending order, where R is the maximum data rate

corresponding to the CQI, and r is the average datarate of the MAC-hs priority queue.

Average data rate of

the MAC-hs priorityqueue

The PF scheduler uses the variation in the radio

channel qualities of individual users (for example,


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Figure 4-10 TFRC selection process

The figure shows the process of TFRC selection.

1. Assuming that all the available Uu resources within the current Transmission TimeInterval (TTI) are allocated to the UE, calculate the maximum Transport Block Size(TBSmax) based on the CQI from the UE and the reception capability of the UE. The

calculation of TBSmax within the current TTI takes the following factors intoconsideration:

Available power of the HS-PDSCH

The HSDPA power allocated to the scheduled users within the current TTI and theHS-SCCH power allocated to the UE within the current TTI are excluded. In addition,

the total transmit power for one UE within a TTI cannot exceed the value of the MAXPOWER PER HS-USER parameter.

Available codes of the HS-PDSCH

CQI from the UE

For the purpose of CQI reporting, the UE assumes the total received HS-PDSCH power

as follows.

P HS-PDSCH = PCPICH + Γ +Δ

where,

− PCPICH is the power of the CPICH.


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− Δ is the reference power adjustment. For detailed information, see 3GPP TS 25.214.

− Γ = Max(-6, Min(13, P CellMAX - PCPICH - MPOconstant))

− PCell-MAX - PCPICH = maximum transmit power of the cell - CPICH transmit power

− MPOconstant represents HS-PDSCH MPO Constant and can be set on the RNC LMT.

UE capability

It denotes that the maximum number of HS-PDSCH code that the UE can use, the

maximum size of the transport block that the UE can receive, and whether the UEsupports 16QAM.

2. If there is sufficient amount of data cached in the MAC-hs queue (TBSmax < Queuelength), the data is scheduled for the UE as much as possible in the maximum format ofTFRC, that is, TBS = TBSmax.

3. If there is insufficient amount of data cached in the queue (TBSmax > Queue length), theUu resources necessary for the UE are allocated on the basis of the amount of data in thequeue.

Select the TFRC (power, code, and modulation mode) by searching the CQI-Max TBSmapping table and taking the amount of data cached in the queue into consideration. The

search is based on the priority defined by the Resource Allocate Method parameter, thatis, code preferable or power preferable.

Outdoor cells usually have sufficient code resources but limited power resources.Therefore, for outdoor cells, codes take precedence over power during TFRC selection,

so as to achieve resource efficiency in both code and power and to improve the cellthroughput. For indoor cells, the priorities of codes and power are just the opposite, that

is, power usually takes precedence over codes.

The following figure shows an example of TBSmax searching.


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Figure 4-11 Example of TFRC selection process and CQI-MaxTBS mapping

4. After TFRC is determined, the matched CQI of TBS in the CQI-MaxTBS mapping tableis determined. This CQI is expressed as CQIused. Then, the transmit power of theHS-PDSCHs is calculated as follows:

POWER HS-PDSCH = PCPICH + Γ – (CQI - CQIused).

Within one TTI, the HS-PDSCH power and HS-SCCH power allocated to one UE cannotexceed the value of the MAX POWER PER HS-USER parameter. The limitation on

the total transmit power of a single user is made for the following reason. In the initialdeployment, only a few HSDPA users are included in a cell without high cell load

expected. The function of HSDPA power limitation per user can limit the HSDPA cell

load in this case. The HSDPA cell load is limited by the The Offset of HSPA TotalPower parameter.

Setting the Resource Allocation Method

The Resource Allocate Method parameter is set for the reason that the outdoor cells usually

have sufficient code resources but limited power resources. Therefore, for outdoor cells, codestake precedence over power during TFRC selection, so as to achieve resource efficiency in

both code and power and to improve the cell throughput. For indoor cells, the priorities ofcodes and power are just the opposite, that is, power usually takes precedence over codes.


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Setting MPO

If the value of HS-PDSCH MPO Constant is set properly, the probability of CQI being

equal to 0 or 30 is very low, for example, 1% or lower. Otherwise, the parameter value should

be adjusted. This parameter is set for the purpose that the CQI reported is within the range of

1 to 30.

4.5 HSDPA Power Resource Management Overview of Power Resource Management

Dynamic Power Resource Allocation

4.5.1 Overview of Power Resource Management

The maximum cell transmit power is a constant. The DL power consists of the following

parts:

Power of DL HSPA physical channels, including the HS-PDSCH, HS-SCCH, E-AGCH,

E-RGCH, and E-HICH

The maximum available power can be set on the RNC LMT through parameter TheOffset of HSPA Total Power.

Power of common physical channels

This type of power is reserved.

Power of the DPCH

HSDPA power resource management addresses the following issues:

The dynamic power allocation between HS-DSCH and R99 channels when HS-DSCHand R99 channels are on the same carrier frequencies.

HS-DSCH power control: See HS-SCCH power control and HS-DPCCH power controlin Power Control.

HS-PDSCH power allocation: See 4.4.1 Overview of TFRC Selection.

4.5.2 Dynamic Power Resource Allocation

The cell power resources are allocated dynamically between the DPCH and the DL HSPA

physical channels, but the power resources are reserved for the common physical channels.

After power resources are allocated to the DPCH, E-HICH, E-AGCH, and E-RGCH, the

remaining resources are allocated to the HS-SCCH and HS-PDSCH. The power allocated toHSPA cannot exceed The Offset of HSPA Total Power.


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RNC-controlled static code allocation

In the static code allocation, the HS-PDSCH codes are configured on the RNC LMT, and

the allocated codes recorded on the RNC can be modified only through the AllocateCode Mode parameter.

RNC-controlled dynamic code allocationIt is is set through the Allocate Code Mode parameter on RNC LMT.

NodeB-controlled dynamic code allocation

It is set through the Dynamic Code Switch parameter.

In the RNC-controlled and NodeB-controlled dynamic code allocation, the HS-PDSCH code

range is configured on the LMT. The UTRAN can automatically adjust the number ofHS-PDSCH codes in real time based on the current cell codes used by R99 channels to

maximize the usage.

The HS-PDSCH codes received by the UE in a TTI must be continuous. Therefore, the

algorithm should try to reserve codes adjacent to the reserved HS-PDSCH codes during code

allocation to the DL dedicated channels of the cell. Thus, the HS-PDSCH can have as manyavailable codes as possible. When the state of the code resource used by R99 channels

changed, the algorithm rearranges the allocated R99 codes so that more continuous SF16codes are available for HSDPA.

NodeB-controlled dynamic allocation allows the NodeB to use the HS-PDSCH codes

allocated by the RNC and also can dynamically allocate the idle codes of the current cell tothe HS-PDSCH channel. It is more flexible to allocate the code for HS-PDSCH through the

NodeB-controlled dynamic allocation than the RNC-controlled dynamic allocation. NodeB-controlled dynamic allocation can save the signaling traffic resource for code

reconfiguration on the Iub interface, compared to the RNC-controlled dynamic allocation.

The following HS-PDSCH code allocation scheme is preferred:

The RNC uses the static code allocation. The fixed number of reserved HS-PDSCH

codes is specified by Code Number for HS-PDSCH. The NodeB uses the dynamic codeallocation so that the HS-PDSCH codes can be increased.

If the NodeB does not support the dynamic code allocation, you can enable the dynamiccode allocation on the RNC side through the parameters Code Max Number forHS-PDSCH and Code Min Number for HS-PDSCH.

The HS-PDSCH code allocation mode can be set through Allocate Code Mode.

4.6.2 RNC-Controlled Static Code Allocation

In static allocation, the RNC reserves codes for the HS-PDSCH. The DPCH, HS-SCCH, and

common channels use the remaining codes.

Figure 4-13 Static allocation


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After increasing the codes for the HS-DSCH, the SF of the remaining codes should beequal to or smaller than the value of Cell LDR SF reserved threshold.

Cell LDR SF reserved threshold is used to reserve code resources for new admission and

avoid code resource congestion. For details of Cell LDR SF reserved threshold, refer to

Basic Congestion Triggering in Load Control.

Reducing the Codes Reserved for the HS-PDSCH

The following figure shows the process of reducing the codes reserved for the HS-PDSCH.

The solid dots represent the occupied codes and the circles represent the idle codes.

Figure 4-16 Reducing the codes reserved for the HS-PDSCH

After DCH RL setup, RL addition, or RL reconfiguration (for example, SF is changed to asmaller one) is completed,, the RNC will reallocate one of the shared codes reserved for the

HS-PDSCH to the DPCH. After reallocating, the minimum SF of free codes should be lowerthan Cell LDR SF reserved threshold. The re-allocated code number should be the smallestone.

4.6.4 NodeB-Controlled Dynamic Code Allocation

NodeB-controlled dynamic allocation allows the NodeB to use the HS-PDSCH codes

allocated by the RNC. The NodeB can dynamically allocate the idle codes of the current cellto the HS-PDSCH.

Figure 4-17 NodeB controlled dynamic allocation of the HS-PDSCH codes

The NodeB detects the SF16 codes that are not for the HS-PDSCH every 2 ms. If the codes orsub-codes are allocated by the RNC to the DCH or common channels, they are regarded as

occupied. Otherwise, they are regarded as unoccupied. Therefore, the HS-PDSCH codesavailable for the HS-PDSCH include the codes allocated by the RNC and those unoccupied

consecutive SF16 codes that are adjacent to the reserved HS-DSCH codes.


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For example, in a cell HS-PDSCH, the RNC allocates SF16 codes numbered 11 to 15 toHS-PDSCH, SF16 codes numbered 0 to 5 to the DCH and common channels. Then, in thisTTI, the HS-PDSCH can use SF16 codes numbered 6 to 15.

If the DCH codes allocated by the RNC are temporarily occupied by the HS-PDSCH before

the setup of a radio link, the NBAP message is sent to the RNC, indicating that the radio linkis set up successfully. Then, the DCH occupies the codes. The HS-PDSCH cannot use these

codes until they are released by the DCH.

4.7 Other HSDPA Related Algorithms

4.7.1 Mapping of Service to HSDPA

SRB over HSDPA

This feature provides a higher signaling rate and reduces the call process delay. Comparedwith the scenario where the SRB is carried on the DCH, code resources are saved and cell

load is reduced when the SRB is carried on HSDPA.

The signaling over SRB is delay-sensitive and irregular. In some cases, the code may be

limited prior to power and the cell capacity is affected. Thus, it is more appropriate to set upSRB over HSDPA rather than the DCH. Moreover, while the SRB is over HSDPA, the

F-DPCH multiplexed by users is introduced, and thus saving code resources.

SRB over HSDPA can be applied during the RRC connection setup procedure or other procedures such as mobility management.

If the SRB is set up over the DCH, it can be reconfigured to the mapping on HSDPA in some

cases, for example, if the target cell of handover supports HSDPA while the source cell doesnot. Inversely, the SRB mapping on HSDPA can also be reconfigured to the mapping on DCH

if the target cell of handover does not support HSDPA.

SRB over HSDPA is configurable. For details, refer to Radio Bearers Description.

VoIP over HSPA

In the fixed network, Voice over IP (VoIP) has turned out to be an attractive and cost-effective

solution to support PS conversational services. The rapid growth of VoIP users urges thecellular operator to introduce this feature to make their network more profitable. Moreover,

from the evolution point view, it is also helpful to converge the operator’s network into one

all-IP network and decrease the total operational cost accordingly.

In WCDMA system, on the one hand, VoIP can provide lower cost voice service compared to

the traditional CS voice, and on the other hand, such service can make it simpler to supportrich services like real-time video sharing or messenger. The reason is that they are all carried

on the PS domain and the end user will also benefit from it.

VoIP service can be carried on DCH or HSPA. When it is set up on the DCH, the capacity isnot competitive due to more resource consumption. Therefore, VoIP over HSPA is a better

solution. And Robust Header Compression (RoHC) should also be supported to improve theoverhead efficiency. The following features are to provide VoIP over HSPA solution:

RAB Mapping, refer to Radio Bearers Description.


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Figure 4-18 HS-DPCCH preamble and postamble

4.7.3 HSDPA over Iur

HSDPA over Iur is the scenario where the HSDPA serving cell is carried at the DRNC. The

feature includes HSDPA service management over Iur, HSDPA mobility management over Iur,and so on.

HSDPA service management over IurHSDPA service management over Iur refers to HSDPA service setup, modification, release,

and state transition.

When the UE is in the CELL_DCH state and the DRNC cell is in the active set or the UE is in

the CELL_FACH state and camps in a DRNC cell, the HSDPA service can be setup, modified,and released over Iur.

The service over Iur can be reconfigured between HSDPA and R99 with UE state transition between CELL_DCH and CELL_FACH.

HSDPA mobility management over Iur

HSDPA mobility management over Iur includes hard handover, cell update (caused by radio

link failure), and serving cell change.

In this example (from TS25.931) the source Node B and the target Node B are controlled by

two different DRNCs, referred to as source DRNC and target DRNC, respectively. In this casethe HS-DSCH mobility procedure is performed in a single step.


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Figure 4-19 Inter-Node B (inter DRNC) synchronized serving HS-DSCH cell change at hardhandover

HSDPA static relocation

If the HSDPA service is over Iur and the radio links are provided only by the target RNC, the

static relocation can be triggered.

4.7.4 HSDPA Cell Load Control

The UE can access an HSDPA cell only after it passes all of the following admission

decisions:

Admission decision based on power resources

Admission decision based on Iub resources

Admission decision based on UE quantity

For detailed information, see Load Control.

4.7.5 HSDPA Mobility ManagementHSDPA Mobility Management is applied in the mobility scenarios in which the HSDPA

serving cell is involved.

For details, refer to Intra-Frequency Handover, Inter-Frequency Handover and Inter-RATHandover Description.

4.7.6 HSDPA Channel Switching

HSDPA channel switching consists of channel switching between HS-DSCH and FACH and

channel switching between HS-DSCH and DCH.

HSDPA channel switching refers to the following aspects:


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The UE is rejected by the admission control algorithm when it attempts to access anHSDPA cell. If the activity of the UE that performs data services increases and the RNCreceives an event 4A report, the RAN tries to hand over the UE from the DCH to theHS-DSCH.

Channel switching from DCH or FACH to HS-DSCH needs to implement the process ofHSDPA directed retry.

4.7.7 HSDPA TX Diversity

The TX diversity mode of the HS-PDSCH can be set through the Hspdsch priority Txdiversity mode parameter on the RNC LMT.


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5 HSDPA ParametersHSDPA Parameters provides information on the effective level and configuration of the

arameters related

Table 5-1 Parameters related to Inter-RAT Handover

p to the feature.

Parameter ID Effective Level Configurationon ...

Parameter Name

Allocate Code Mode AllocCodeMode Cell(ADD CELLHSDPA) RNC

Cell LDR SF reserved threshold CellLdrSfResThd Cell(ADD CELLLDR) RNC

Code Max Number forHsPdschMaxCodeNum Cell(ADD CELLHSDPA)

RNCHS-PDSCH

Code Min Number forHS-PDSCH

HsPdschMinCodeNum Cell(ADD CELLHSDPA)RNC

Code Number for HS-PDSCH HsPdschCodeNum Cell(ADD CELLHSDPA) RNC

Code Number for HS-SCCH HsScchCodeNum Cell(ADD CELLHSDPA) RNC

H Retry Timer Length HRetryTimerLen RNC(SET COIFTIMER) RNC

HS-PDSCH MPO Constant HsPdschMPOConstEnum Cell(ADD CELLHSDPA) RNC

Hspdsch priority Tx diversity schPrioTxDiversityMode

ELLSETUP) RNCHspd Cell(ADD CRNC(ADD NRNCCELL)mode

Scheduling Priority Indicator AP)

SPIRNC(SET SPIFACTOR)

RNC(SETSCHEDULEPRIOM

RNC

The Offset of HSPA Total Power werHspaPo Cell(ADD CELLHSDPA) RNC

Traffic Class TrafficClass RGBR)-(SET USE RNC

Traffic Handling PriorityTHP

EPRIOMAP)

RNCRNC(SET

SCHEDUL

User Priority USERPRIORITY

DEFAULTTRMMAP)

RNC(SET RNC


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