4- Owa320010 Hspa & Hspa+ Introduction Issue 1.00

7/30/2019 4- Owa320010 Hspa & Hspa+ Introduction Issue 1.00

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HSPA & HSPA+ Introduction

Confidential Information of Huawei. No Spreading WithoutPermission

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HSPA & HSPA+ Introduction P-1



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Mobile network data rate evolution

WCDMA data transmission evolved from GSM/GPRS, inheriting much of theupper layer functionality directly from those systems. The first commercial

deployments of WCDMA are based on a version of the standards called

Release 99, with HSDPA introduced in Release 5 to offer higher speed

Downlink data services.

Enhanced Data rates for GSM Evolution (EDGE) is another system in the

GSM/GPRS family that some operators have deployed as an intermediate

step before deploying WCDMA.

Release 6 introduces the High Speed Uplink Packet Access (HSUPA) toprovide faster data services for the Uplink.

For HSUPA (Uplink) the theoretical maximum achievable peak data rate is

5.76 Mbps, while for HSDPA (Downlink) it is 14.4 Mbps.

Release 7 introduces HSPA+ to increase data rate and system capacity.

Some new features are used such as MIMO, DL 64QAM, CELL_FACH

operation and etc.

Release 8 introduces more new features to HSPA+ such as DL

MIMO+64QAM, DC-HSDPA (Dual Carrier-HSDPA), UL 16QAM and etc. TheDL/UL peak data rate can reach 42Mbps/11.5Mbps.




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Data Services and High Speed Downlink Packet Access (HSDPA)

Data Services are expected to grow significantly within the next few years.Current 2.5G and 3G operators are already reporting that a significant

proportion of usage is now due to data, implying an increasing demand for

high-data-rate, content-rich multimedia services. Although current Release

99 WCDMA systems offer a maximum practical data rate of 384 kbps, the

3rd Generation Partnership Project (3GPP) have included in Release 5 of

the specifications a new high-speed, low-delay feature referred to as High

Speed Downlink Packet Access (HSDPA).

HSDPA provides significant enhancements to the Downlink compared to

WCDMA Release 99 in terms of peak data rate, cell throughput, and round

trip delay. This is achieved through the implementation of a fast channel

control and allocation mechanism that employs such features as Adaptive

Modulation and Coding and fast Hybrid Automatic Repeat Request (HARQ).

Shorter Physical Layer frames are also employed.




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Release 99 Downlink Packet Data

There are different techniques defined in the Release 99 specification toenable Downlink packet data. Most commonly, data transmission is

supported using either the Dedicated Channel (DCH) or the Forward Access

Channel (FACH).

The DCH is the primary means of supporting packet data services. Each

user is assigned a unique Orthogonal Variable Spreading Factor (OVSF)

code dependent on the required data rate. Fast closed loop Power Control

is employed to ensure that a target Signal to Interference Ratio (SIR) is

maintained in order to control the block error rate (BLER). Macro Diversity

is supported using soft handover.

Data transfer can also be supported on the FACH. This common channel

employs a fixed OVSF code. As it needs to be received by all UEs, higher

data rates are generally not supported. Macro Diversity is also not

supported and the channel operates with a fixed (or slow changing) power

allocation. Each data block contains a unique UE identifier that allows a

given UE to keep itsown data and discard that belonging to other UEs.




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Although WCDMA Release 99 standard allows for maximum data rates of up to

2.0 Mbps, it has only been widely implemented with a maximum data rate of 384

kbps. This data rate is achieved by allocating a dedicated channel to each user.

The use of dedicated resources can be a limitation, especially for data applications

with bursty characteristics. Each dedicated channel uses an OVSF code. Shorter

codes are used for higher data rates and longer codes for lower data rates. When

an OVSF of a particular length is used, all longer OVSF codes derived from that

code become unavailable. This limits the number of simultaneous high speed data

users in a given cell. The Release 99 standards provide support for a Secondary

Scrambling Code, which eases this limitation, but it has not been widely

implemented in commercial systems and will likely be removed from future

versions of the specification. The data rate of a dedicated channel can be adjusted

to accommodate varying requirements of a data service application, but the

procedure for doing so is slow and thus inefficient. Capacity is controlled both by

the maximum amount of PA power that is available and by the power

requirement of each data service. In dedicated mode, fast power control is used

so that a target Eb/No is achieved on the Downlink. However, the required Eb/No

set point changes at a much slower rate. This can result in wasted resources

whereby a better than required Eb/No is achieved for the required BLER.




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In HSDPA, the NodeB allocates a set of high speed channels. These channels are

assigned to a user using a fast scheduling algorithm that allocates the channels

every 2 ms. All or part of the channels may be assigned to a given user during any

2 ms period.

The rapid scheduling of HSDPA is well-suited to the bursty nature of packet data.

During periods of high activity, a given user may get a larger percentage of the

channel bandwidth, while it gets little or no bandwidth during periods of low

activity.




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In HSDPA a common channel without closed loop power control is employed for

data transfer. Users are separated in both the time and code domains. A fixed

spreading factor is employed but multi codes operation is possible for increased

data rates.

Adaptive Modulation and Coding (AMC) replaces the role of power control so that

the modulation and coding rate are changed depending on the channel condition.

This is accomplished by locating the scheduling algorithm for channel allocation at

the NodeB instead of the RNC in Release 99.




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Comparison Summary

DCH and FACH are the two Release 99 channels typically used for packetswitched data in practice. The advantages and disadvantages of each

approach are apparent. Whereas DCH is suited for medium high data rates

(with a maximum rate of 384 kbps), rate switching is slow, making it

unsuitable and inefficient for bursty data such as a Web browsing

application. By contrast, FACH provides good support for bursty data but is

a common channel without power control or other mechanism to account

for channel conditions. This makes it unsuitable for higher data rates.

Switching from DCH to FACH is slow and inefficient, due in part to the

typical timer values used to detect inactivity

HSDPA is suitable to high date rates for a bursty application, though we

will see that the absence of soft handover makes it more suitable for

stationary or low-mobility users than for highly mobile users. HSDPA

typically operates at a fixed power, but feedback from the UE can instruct

the NodeB to use lower power when the UE is in good channel conditions.

Link adaptation is used to adjust data rate, coding, and modulation to

quickly respond to changing channel conditions.




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Data Services are expected to grow significantly within the next few years.

Current 2.5G and 3G operators are already reporting that a significant proportion

of usage is now devoted to data, implying an increasing demand for high-data-

rate, content-rich multimedia services. Although current Release 99 WCDMA

systems offer a maximum practical data rate in Uplink of 384 kbps, the 3rd

Generation Partnership Project (3GPP) has included in Release 6 of the

specifications a new high-speed, low-delay feature called High Speed Uplink

Packet Access (HSUPA).

HSUPA provides significant enhancements to the Uplink compared to WCDMA

Release 99 in terms of peak data rate, cell throughput, and latency. This is

achieved through the implementation of a fast resource control and allocation

mechanism that employs such features as Adaptive Coding, fast Hybrid Automatic

Repeat Request (HARQ) and Shorter Physical Layer frames. With the addition of

HSUPA, a better balance between Downlink HSDPA and Uplink traffic

performance is also achieved.

The High Speed Uplink Packet Access (HSUPA) is a 3GPP Release 6 feature, also

called Enhanced Uplink (EUL) or Enhanced DCH (E-DCH).




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Release 99 Uplink Packet Data

There are two different techniques defined in the Release 99 specificationto enable Uplink packet data. Most commonly, data transmission is

supported using either the Dedicated Channel (DCH) or the Random Access

Channel (RACH).

The DCH is the primary means of supporting packet data services. Each UE

uses an Orthogonal Variable Spreading Factor (OVSF) code, dependent on

the required data rate. Fast closed loop Power Control is employed to

ensure that a target Signal-to-Interference Ratio (SIR) is maintained in

order to control the block error rate (BLER). Macro Diversity is supported

using soft handover.

Data transfer can also be supported on the RACH. This common channel

employs an OVSF code, with a spreading factor between 32 and 256, as

negotiated with UTRAN during the Access procedure. Because it needs to

be shared among all UEs, higher data rates are generally not supported.

Macro Diversity is also not supported and the channel operates with a

fixed (or slow changing) power allocation.




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Release 99 Uplink Limitations

Among the available options for Uplink data transmissions in Release 99,the Common Channel (RACH) only allows for a small amount of data and a

limited duration of the transmission. Thus, from a practical point of view,

the Dedicated Channel (DCH) is the way to accommodate packet services in

a Release 99 network. However, significant limitations must also be faced

when using the Uplink DCH:

Large Scheduling Delay: In Release 99, the scheduling of resources is done

in the serving RNC and involves Layer 3 signaling messages to and from the

UE, which causes the mechanism to be relatively slow in assigning or

reconfiguring the resources assigned to a particular UE.

Large Latency: The transmission time interval can vary from 80 ms down to

10 ms as best case, posing an intrinsic boundary to the latency values. In

addition to that, the only available mechanism for retransmissions of

erroneous packets is located in RNC, thus significantly contributing to the

latency figures

Limited Uplink Data Rate: Though the standard allows for high data rate

on the Release 99 Uplink, typical values of maximum data rate observed in

deployed networks range from 64 kbps up to 384 kbps, while using aspreading factor of 4. In order to achieve higher peak data rates, lower

coding rates and multi-code transmission shaould be used, but these are

not available in R99 systems.




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HSUPA is realized by introducing the Enhanced Dedicated Channel (E-DCH)

In HSUPA, the Node B allows several UEs to transmit at a certain power level atthe same time. These grants are assigned to users by using a fast scheduling

algorithm that allocates the resources on a short-term basis (every 10ms or 2ms).

The rapid scheduling of HSUPA is well suited to the burst feature of packet

service. During periods of high activity, a given user may get a larger percentage

of the available resources, while getting little or no bandwidth during periods of

low activity.




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Enhancement methods in HSUPA

To overcome the Release 99 limitations previously mentioned, HSUPA hasbeen introduced in Release 6

The use of shorter TTI, fast resource scheduling, and fast retransmissions

at the physical layer improves uplink data services, while addressing the

release 99 limitations in terms of latency, peak data rate, coverage, and

capacity. Additionally, improved quality of service support helps to

optimize resource utilization and guarantee the promised quality




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The CQI table consists of 30 entries, where each entry indicates a different TFRC.

Transport Format Resource Combination (TFRC) points to the combination of

number of HS-PDSCH channelization codes, modulation scheme, and the HS-DSCH

transport block size. The 5-bit CQI reported by a UE is an index into this table

containing all possible TFRC combinations for that UE category. The TFRC

combinations are different for UEs with different HS-DSCH UE categories because

of the differences in the UE capabilities. Along with TFRC, CQI may also indicate a

power offset relative to the current HS-PDSCH power. The CQI table shown in the

slide is for UE categories supporting up to 15 HS-PDSCH codes (HSDPA terminal

category 10).




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HSDPA is advertised with data rates up to 14 Mbps. However, the actual HS-DSCH

peak data rate depends on the UEs HS-DSCH category. As shown in the table,

only a category 10 UE can achieve the maximum HSDPA throughput of 14 Mbps

when using all 15 HS-PDSCHs simultaneously.

Factors that decide the UEs HS-DSCH category are:

HS-PDSCH codes Determines the number of simultaneous HS-PDSCH channels

that can be decoded by a UE.

Inter-TTI interval Determines the minimum interval (in terms of HS-DSCH TTI)

between two successive HS-PDSCH assignments. The more HARQ processes a UE

supports, the shorter the inter-TTI interval. A minimum inter-TTI of 1 requires atleast 6 simultaneous HARQ processes.

Transport Block size Determines the maximum size of transport block that can

be sent on HS-DSCH in a TTI. It is dependent on the number of HS-PDSCH codes

and the modulation scheme.

IR buffer size Determines the maximum number of soft bits that can be buffered

by a UE across all simultaneously running HARQ processes.




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Example for Chase Combining ( CC ) Scheme

Example for Incremental Redundancy ( IR ) Scheme




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To support consecutive assignments, HSDPA defines a Hybrid Automatic Repeat

Request (HARQ) protocol. This protocol is implemented in both the NodeB and the

UE, and consists of procedures implemented in both the MAC-hs sublayer and the

Physical Layer. When the NodeB assigns an HSDPA subframe to a UE, it also

assigns a HARQ process to handle the data transfer. The UE HARQ process is

responsible for

Decoding the initial transmission

Sending an ACK or NACK

Soft-combining retransmissions of the data packet until it is successfully

decoded or until NodeB aborts the packet The maximum number of HARQ processes that a UE supports is a function of its

HSDPA category. The minimum number of HARQ processes supported by any UE

is 2, which corresponds to a UE that uses an inter-TTI interval of 3.




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Example of Code Allocation for a HSDPA cell:




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Shared channel transmission implies that a certain amount of radio resource of a cell

(code and power) is seem as a common resource that is dynamically shared between

users.

The NodeB transmit power allocation algorithm is not specified by the standard.




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There can be multiple (up to 15) HS-PDSCHs in a serving cell, which enables use of

both time division and code division multiple access methods.




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WCDMA R99 uses QPSK modulation scheme for downlink transmission. To

support higher data rate, 16QAM is introduced in HSDPA.

NodeB decides to use QPSK or 16QAM based on the CQI feedback from UE.




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The basic idea of fast scheduling is to transmit at the fading peaks of the channel

in order to increase the throughput and to use resource more efficiently. But this

might lead to large variations in data rate of the users. The trade-off is between

the cell throughput and fairness against users.

There are a number of scheduling algorithms that take into consideration the

trade-off between throughput and fairness:

Round Robin (RR): radio resource are allocated to communication links on a

sequential basis, not taking into account the instantaneous radio channel

conditions experienced by each link.

Max C/I: for maximum cell throughput ,the radio resource should be asmuch as possible be allocated to communication links with the best

instantaneous channel condition.

Proportional Fair (PF): allocates the channel to the user with relatively best

channel quality.

Enhanced Proportional Fair (EPF): allocates the channel to the user

according to relatively best channel quality, fairness, guarantee bit rate

requirement.




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Three new channels are introduced for HSDPA:

HS-PDSCH (High Speed Physical Downlink Shared Channel): This is adownlink shared channel. It is used to carry higher layer signaling or traffic

data.

HS-SCCH (High Speed Shared Control Channel): This is a downlink shared

channel. It is used to carry some physical indication which is used by the UE

to decode the higher layer data in HS-PDSCH. The following are some of

the information carried by HS-SCCH:

UE ID: Indicating which UE is scheduled in HS-PDSCH

Channelization Code Set: Indicating which codes allocated to the UEif it is scheduled

Modulation Scheme: Indicating the modulation scheme of HS-

PDSCH (QPSK or 16QAM)

Some other information

HS-DPCCH: This is a uplink dedicated channel. It is used to feedback CQI

and HARQ ACK/NACK by UE.




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DCCH and DTCH can be mapped to HS-DSCH.

A UE using HSDPA can also have additional Release 99 DCH. The HS-SCCH and HS-DPCCH are physical layer (control) channels. They carry no

upper layer information, and therefore have no logical or transport channel

mapping.




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5 OVSF code for HS-PDSCH

14.4Mbps / 3 = 4.8Mbps QPSK

4.8Mbps / 2 = 2.4Mbps

Turbo code rate =1/3

2.4Mbps / 3 = 0.8Mbps

Retransmission

0.8Mbps 0.8 = 640 kbps



1 2 3 4 5

Decoded on 1st transmit Decoded on 2nd transmit


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Compared to R99 UL DCH, the enhance DCH specified for HSUPA in Release 6

offers the following features:

Shorter TTI of 2ms: which can reduce the latency and can be scheduled

faster

Lower SF: which can increase physical channel symbol rate , higher peak

data rate is available

Uplink L1 HARQ throughput: improve physical layer performance with fast

retransmissions

New transport and physical channels

Fast resource control: with new MAC entities in NodeB, radio resource canbe scheduled faster to optimize the total throughput




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This slide lists some important aspects for comparing HSDPA and HSUPA to help

understand HSUPA principles and operation.

The HSDPA concept is based on high speed shared channels with fast L1 HARQ

retransmission and rate and modulation adaptation to adjust to channel

conditions. The fast scheduler is located in the Node B and assigns the available

resources (power and codes) to several users. This enables cell power to be

directed to a single user (or to a small group of users) for a short period of time,

during which other users do not get any data. In this way, one Node B transmitter

can be shared among many UE receivers.

For HSUPA, the channel remains a dedicated channel, but with enhanced

capabilities such as fast scheduling and L1 HARQ retransmissions. Power control

and soft handover are still used to adapt to radio channel conditions. Because

each UE has an independent transmitter with its own power and code availability,

the HSUPA scheduler can accommodate many users to be received by the same

Node B, where the Rise-over-Thermal Noise level indicates the uplink loading of

the system.




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The Rise-over-Thermal noise level is a measure of the uplink load at the NodeB

receiver.

By increasing the number of UEs transmitting on the uplink and their

transmit power, the overall level of interference in the uplink band also

increases.

The NodeB receiver perceives this level as noise, and it directly affects the

decoding performance of uplink data transmissions.

The NodeB controls the interference level by adjusting the UE grant

assignments according to the current interference level.

When the UE receives a new grant, it uses it in combination with availableUE transmit power and amount of data in the buffer to determine the data

rate and the corresponding transmit power.




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Similar to HSDPA, HSUPA implements fast resource allocation and control with a

scheduler in the NodeB. While the HSDPA scheduler accommodates a common

resource to several users, the HSUPA scheduler has a different task: it coordinates

the reception of data transmitted from several UEs to a single NodeB. This can be

regarded as a very fast resource allocation of a dedicated channel (E-DCH), rather

than a sharing of a common channel (HS-DSCH).

On one side, each UE will tend to transmit as much as possible based on channel

conditions, the amount of data in the buffer, and the power available. On the

other side, the scheduler will try to satisfy each connected UE while preventing

overloading and maximizing resource utilization and cell throughput.




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This slide illustrates HSUPA operation :

1. The UE asks the NodeB for a grant to transmit data on uplink. 2. If the Node B allows the UE to send data, it indicates the grant in terms

of Traffic-to-Pilot (T/P) ratio. The grant is valid until a new grant is

provided.

3. After receiving the grant, the UE can transmit data starting at any TTI

and may include further requests. Data are transmitted according to the

selected transport format, which is also signaled to the NodeB.

4. After the Node B decodes the data, it sends an ACK or NAK back to the

UE. If the NodeB sends a NAK, the UE may send the data again with aretransmission.




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This slide illustrates a data transmission request from the UE through scheduling

information (SI), by which the UE asks the Node B for a grant to transmit data on

Uplink E-DCH.

UE power availability and UE buffer status are combined to determine the

scheduling information.




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This slide illustrates an HSUPA absolute grant assignment upon request from the

UE. The grant is determined based on uplink interference situation (Rise-over-

Thermal noise) at the NodeB receiver and on the UE transmission requests and

level of satisfaction.

The Node B indicates the Traffic-to-Pilot (T/P) grant by downlink grant channel.

The grant is valid until a new grant is given or modified.

SI is scheduling information. It includes the UL power usage and the buffer status

of UE. UE uses SI to request resource from NodeB.




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This slide illustrates an HSUPA Data Transmission for scheduled grants.

After receiving the grant, the UE can transmit data starting at any TTI and mayinclude additional scheduling information. The transport format is first selected

based on the received grant, on the available power and on the data in the buffer.

Data are transmitted on a set of E-DPDCH channels, and transport format

Information is signaled to the Node B on the corresponding E-DPCCH. The Happy

Bit (Happy Bit indicates the UEs level of satisfaction. ) is also included.




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This slide illustrates the acknowledgment of data at the NodeB and HARQ

retransmission.

After the NodeB attempts to decode the data, it sends an ACK or NACK to the UE.

If the NodeB sends a NACK, the UE may send the data again with a fast

retransmission.




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The main introduction in Release 6 is the new data channel, Enhanced Dedicated

Channel or E-DCH, which carries the uplink high speed data. New physical

channels are introduced to support E-DCH.

On the uplink, two new physical channels are introduced: E-DPDCH (Dedicated

Physical Data Channel for E-DCH) and E-DPCCH (Dedicated Physical Control

Channel for E-DCH). The E-DCH can be mapped to one to four uplink E-DPDCHs

(Dedicated Physical Data Channels for E-DCH), with improved coding and

modulation design. The physical layer control information, E-TFCI etc., is carried

on one E-DPCCH (Dedicated Physical Control Channel for E-DCH).

On the Downlink, three new physical channels are introduced to support E-DCH.

The downlink physical channels E-HICH (HARQ Indicator Channel for E-DCH) and

E-RGCH (Relative Grant Channel for E-DCH) are dedicated channels and they share

a single channelization code assigned by the higher layer to the UE. The UE

increases or decreases its E-DCH data rate based on the relative grant indicator on

E-RGCH. The downlink channel E-AGCH (Absolute Grant Channel for E-DCH) is a

common channel shared by all the users in the cell. The addressing on E-AGCH is

realized by masking CRC bits with E-RNTI (RNTI for E-DCH).




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DCCH and DTCH can be mapped to E-DCH.

A UE using HSUPA can also have additional Release 99 DCH and/or HSDPAchannels, although the standard specifies restrictions for the possible

combinations. Because power control and soft handover are supported for E-DCH,

the channel can be seen as an extension of the Release 99 DCH.

The E-DPCCH, E-HICH, E-AGCH, and E-RGCH are physical layer (control) channels.

They carry no upper layer information, and therefore have no logical or transport

channel mapping.




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Hybrid ARQ The hybrid ARQ for HSUPA consists of an N-Channels stop-and-wait

protocol. The number of HARQ processes is 4 for a 10 ms TTI and 8 for a 2 ms TTI

configuration. The retransmission is synchronous, with separate feedback

provided for each radio link. After requesting and receiving a grant for data

transmissions:

The UE transmits the data of the corresponding HARQ process to all

NodeBs for which a radio link exists.

Each Node B connected to the UE sends ACK/NAK back to the UE.

The transmission is successfully completed if an acknowledge (ACK) is

received.




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The E-DCH Active Set is limited to 4 cells, one of which is the E-DCH serving cell.

The radio links that are in softer handover with the E-DCH serving cell (i.e.,connected to the same NodeB) constitute the Serving E-DCH Radio Link Set (RLS).

All other links in the E-DCH active set, which are connected to other NodeBs, are

non-serving radio links.




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The following assumptions are needed to achieve the theoretical maximum data

rate of 5.76 Mbps:

Lower channel coding gain Using an effective code rate of 1 increases the

data rate, but the channel conditions must be very good for the NodeB to

correctly decode every data block on the first transmission.

Lower spreading factor UE must use SF 2.

Multi-code transmission Four codes (2 codes with SF2 and 2 codes with

SF4) are used by E-DPDCH.

Shorter TTI 2ms TTI is needed. Because the maximum transport block

size is 20000 bits with 10ms TTI, the maximum data rate for 10ms TTI is2Mbps.

In a practical scenario, the practical maximum data rate will be less than 5.76

Mbps, due to less than ideal channel conditions, the need for retransmission, and

the need to share the UE power with other channels.




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The examples presented so far have assumed a turbo code rate of 1/3 and BPSK

modulation. If we assume a single E-DPDCH and a transport block containing 640

data bits, rate 1/3 turbo coding produces 1920 symbols. BPSK modulation maps

one symbol onto one modulation symbol, which is then spread by the OVSF of

length 4. This results in 7680 chips sent every 2ms, corresponding to the

fundamental WCDMA chip rate of 3.84 Mcps.

If the transport block is not exactly 640 data bits, the rate matching step adjusts

the number of symbols after turbo coding to produce 1920 symbols.

By increasing the coding rate, more data bits can be transmitted in a 2 ms TTI,

thus increasing the data rate. Using a coding rate of 1, the data rate becomes 960

kbps, because 1920 bits can be transmitted in 1920 modulation symbols. This

corresponds to puncturing all the parity bits and transmitting only the systematic

bits.




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By changing the spreading factor from 4 to 2, the number of bits that can be

transmitted in a single TTI doubles from 640 to 1280, because now 7680/2 =

3840 symbols can be mapped onto 7680 chips. Again, a coding rate of 1 is

assumed.




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What determines the maximum data rate supported by different categories of UE?

It is a combination of the maximum number of E-DPDCH channels, the spreading

factor, and maximum bits in one TTI.

For 10 ms TTI, a maximum of 2 Mbps peak data rate can be achieved,

corresponding to a maximum transport block size of 20000 bits. To achieve

higher rates, a TTI of 2 ms shall be used.

With a single E-DPDCH channel, a spreading factor from 256 to 4 is allowed. For

multi-code transmissions, only SF4 and SF2 are allowed, in the following

combinations: (2 x SF4) or (2 x SF2) or (2 x SF4 + 2 x SF2). Note that SF=2 is not

permitted on a single code transmission.




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Downlink Enhanced L2: Downlink enhanced L2 allows flexible PDU sizes at the RLC layer

and segmentation at the MAC layer on the Uu interface. The feature prevents L2 from

becoming the bottleneck of Uu rate increasing by multiple-input multiple-output (MIMO)

and 64QAM.

Downlink MIMO: Downlink MIMO increases transmission rates through spatial

multiplexing and improves channel qualities through space diversity. The network side

can dynamically select single- or dual-stream transmission based on channel conditions.

The peak rate at the MAC layer can reach 28Mbps.

Downlink 64QAM: Downlink 64QAM allows the use of 64QAM in HSDPA to increase the

number of bits per symbol and thus to obtain higher transmission rates. The peak rate at

the MAC layer can reach 21Mbps.

Downlink Enhanced CELL_FACH Operation: Downlink Enhanced CELL_FACH Operation

allows the use of HSDPA technologies for the UEs in CELL_FACH, CELL_PCH, and

URA_PCH states (RAN11 only supports HSDPA reception in CELL_FACH state.). The

purpose is to increase the peak rates in these states, reduce the signaling transmission

delay during service setup or state transition, and improve user experience.

CPC: Continuous packet connectivity (CPC) allows uplink and downlink transmissions at

regular intervals. CPC reduces the transmit power and thus prolongs the UE battery life

because the UE does not have to monitor and transmit overhead channels in each TTl.

The reduction in the transmit power also helps to increase the uplink capacity by

decreasing the total interference. This improvement is significant when users such as VoIP

users transmit data discontinuously.

The CPC feature consists of DTX-DTX, and HS-SCCH Less Operation.




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Uplink 16QAM: 16QAM modulation can be used for HSUPA to improve uplink

peak date rate to around 11Mbps.

Uplink Enhanced L2: Some modifications are introduced in Uu interface layer 2 in

uplink direction to support higher data rate and improve uplink transmission

efficiency.

Downlink MIMO + 64QAM: Before RAN12 MIMO and 64QAM can not be used by

one UE simultaneously. In RAN12 downlink MIMO and 64QAM can be used

simultaneously by one UE to receive HSDPA data. With this technology, the

theoretical downlink peak rate can reach 42Mbps.

DC-HSDPA (Dual-cell HSDPA): DC-HSDPA allows a UE to set up HSDPAconnections with two inter-frequency time-synchronous cells that have the same

coverage. Theoretically, DC-HSDPA with 64QAM can provide a peak rate of

42Mbps in the downlink.




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HSPA+ can support three modulation modes: QPSK, 16QAM and 64QAM. Which

mode is used is stilled based on the channel condition of UE.

The AMC feature introduced with HSDPA enables adaptation of modulation and

coding to varying radio conditions. To improve the advantages of AMC even

further, a new modulation scheme, 64 QAM, is introduced with HSPA+.

Theoretically 64QAM can provide a peak rate of 21 Mbit/s to a single UE. It

enables the user with good channel conditions to download data at higher rates,

improves user experience.




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In wireless communications, MIMO refers to a wireless channel with multiple

inputs and multiple outputs.

In a MIMO system, there are N*M signal paths from the transmit antennas and the

receive antennas, and the signals on these paths are not identical.

3GPP Release 7 supports only 22 MIMO system.




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For HSDPA, the peak physical layer throughput is14.4Mbps. To achieve 14.4 Mbps

peak rate, all available SF-16 OVSF codes will be used.

With MIMO system, the multiplexing gain is obtained with independent data

streams on different antennas. The 2*2 MIMO system defined by 3GPP Release 7

can be 28Mbps.




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RAN 11.0 supports HSDPA in only the CELL_FACH state.




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DL DRX is discontinous downlink reception.

UL DTX is discontinousuplink transmission.




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All such UEs must support DL Enhanced L2. These categories do not indicate

whether CPC and Enhanced CELL_FACH operation are supported.

During the connection setup procedure or the service setup procedure, the UE

notifies the network of its capability to support these features.




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The MIMO and 64QAM features are introduced by 3GPP in R7. These two

features can be used respectively. In R7 restricted by the capabilities of UEs,

however, a single user cannot be configured with 64QAM and MIMO at the same

time.

In R8, 64QAM+MIMO can be used by one UE simultaneously to achieve a higher

throughput and better QoS, greatly improving user experience.




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Due to the rapid development of data services, the UMTS needs to improve the

spectrum resource utilization continuously to improve the downlink air interface

capabilities and enrich the service experience of users. The new DC-HSDPA

technology introduced in R8 aims to improve the user throughput through larger

spectrum bandwidth.

Dual-cell HSDPA (DC-HSDPA) enables users to receive the HSDPA data sent from

two inter-frequency downlink cells under the same coverage at the same time.

The network side can dynamically select between two carriers for HSDPA

transmission.




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DC-HSDPA users belong to both anchor and supplementary carrier cells. The DC-

HSDPA users can be scheduled in each cell. Compared with a single cell, the

number of users who can be scheduled is doubled, users with high-quality

channels can be selected through DL scheduling, and the system throughput is

increased. In addition, the channel attenuation of DC-HSDPA users is different in

the two cells, and the probability of high-quality channels is higher than that of

SC-HSDPA users (frequency-selective gain). Therefore, the throughput of users is

increased, and the service delay is reduced.




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Compared with the traditional HSPA technology, DC-HSDPA brings the following

gains:

Improving the peak throughput of users. When the DC-HSDPA and 64QAM

features are used together, the peak throughput can reach 42Mbps.

Compared with SC-HSDPA, DC-HSDPA features frequency-selective

scheduling and dynamic multi-carrier gain equalization, thus increasing the

system capacity. The gain is more obvious particularly when the load on

the two carriers is unequal.

Greatly reducing the burst service and HTTP service delay. As the user peak

rate is increased, the HTTP service response delay can be greatly reduced,and user service experience can be improved.

Improving the user experience of cell edge users and enhancing the DL

coverage.




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In implementation of RAN11.0 and earlier versions, a UL RLC works only in fixed

PDU mode, that is, the PDU size is fixed. Fixed-size PDUs cannot support high-

speed services effectively. When the window size is fixed, small PDUs cannot

support high-speed services. Large PDUs can support high-speed services, but the

power on the cell edge may be restricted. In addition, fixed-size PDUs may

introduce some extra headers and fill bits, which affects the transmission

efficiency. For example, when a UE moves from the cell center to the cell edge,

the transmit power of the UE is restricted when it reaches a certain distance. In

this case, the throughput drops rapidly, and data transmission may be easily

interrupted.

3GPP introduces uplink L2 enhancement in R8. The UL RLC (in UM or AM mode)

can support flexible PDUs and fixed PDUs. When working in flexible PDU mode,

the RLC can receive PDUs with different sizes flexibly to reduce the uplink PDU

size, and improve the throughput under the restricted uplink transmit power.




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Before RAN12, the modulation mode for HSUPA is QPSK. In RAN12, 16QAM for

HSUPA is introduced to improve the peak data.




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Documents

4- Owa320010 Hspa & Hspa+ Introduction Issue 1.00