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High Speed Downlink Packet Access

(HSDPA) FAQ

By Zahid Ghadialy ([email protected])

Last Updated: 07/02/2010

QUESTIONS What does HSDPA stand for?

So what exactly is HSDPA? Interesting! Is HSDPA part of 3G or will it be part of 4G?

Why not similarly have HSUPA where U stands for uplink?

Are HSDPA networks rolled out and can i buy HSDPA capable phones?

Can existing 3G Networks be upgraded to support HSDPA with new Software release? What could be the possible uses of HSDPA? How did 3GPP manage to increase the speed of DL to over 10Mbps?

Is HSDPA applicable for CS and PS RABs both? Is HSDPA applicable in CELL_FACH or CELL_DCH or both the UE states.

Can you give comparison of HSDPA in FDD & TDD Mode?

Where can i find basic tutorial on HSDPA?

I would like to follow all HSDPA related News, which is the best place to look for? I am a researcher and i would like some references to read more on HSDPA.

What does HSDPA stand for?

HSDPA stands for High Speed Downlink Packet Access

So what exactly is HSDPA?

HSDPA is an enhancement to the 3G technology through which you can increase the DL datarates from 384Kbps (theoretically 2Mbps) to 10Mbps (theoretically 14Mbps). Here Kbps stands

for Kilo bits per second and Mbps stands for Mega bits per second. HSDPA delivers higher capacity through improved spectral effeciancy, which provides higher data rates, shorter

response times and better Qos (Quality of Service).

Interesting! Is HSDPA part of 3G or will it be part of 4G?

HSDPA is part of 3G but people also refer to it as 3.5G. More details here.

Why not similarly have HSUPA where U stands for uplink?

There is already a HSUPA. More details available in HSUPA FAQ here.



Are HSDPA networks rolled out and can i buy HSDPA capable phones?

In most of the countries, HSDPA networks have already been rolled out and HSDPA phones are

already available. You can find the latest status of HSDPA capable networks in differentcountries on the GSMA website here.

Can existing 3G Networks be upgraded to support HSDPA with new Software release?

In theory they can be but it might not always be the case. According to The Register HSDPA isa power-hungry technology, and many of the base stations out there aren¶t up to the job. The

key piece of technology is the power amplifier, which has to be a full power, 45-watt model, tohandle the extra data output. Having said that, most of the new newly designed RNC and Node

B's are now capable of handling not just an upgrade from 3H to HSDPA and HSPA+ but also toLTE.

What could be the possible uses of HSDPA?

The same use as that of Broadband connections at home. It would be possible to watchextremely good quality real time Videos, download complete song tracks in less than a minute.

Do real time video conferencing with more than one user using very high quality video.Eventually the wireless operators plan that instead of having wired broadband at home, people

will move to wireless broadband. The list is non exhaustive.

How did 3GPP manage to increase the speed of DL speed to over 10Mbps?

To increase the data rates a new channel called HS-DSCH (High speed downlink shared

channel) was defined. This was somewhat similar to the DSCH defined in the release 99 specs.

This channel maps to HS-PDSCH (high speed physical downlink shared channel). To supportthis data channel a control channel HS-SCCH (High speed shared control channels). The HS-DSCH is transmitted over the entire cell or over only part of the cell using e.g. beam-forming

antennas.

The increased data rates are supported through the introduction of Fast and Complex channel-control mechanisms based on a short fixed packet TTI (transmission time interval), AMC

(adaptive modulation and coding) and L1 HARQ (layer1 hybrid automatic repeat request).

Is HSDPA applicable for CS and PS RABs both?

In release 5 HSDPA is only applicable for PS streaming/interactive/background RABs. Inrelease 6, HSDPA will be used for Signalling Radio Bearers as well.

Is HSDPA applicable in CELL_FACH or CELL_DCH or both the UE states.

HSDPA is only applicable to CELL_DCH state.



Can you give comparison of HSDPA in FDD & TDD Mode?

With respect to TDD FDD

Uplink Uses HS-SICH (SharedInformation Channel ) to

send Ack/Nack & CQ I to Node-B

Uses an associated uplink dedicatedcontrol channel (DPCCH-HS) to send

Ack/Nack, CQI to Node-B.

DownLink It consists of associated Dedicated

Physical Channels and sharedControl Channels(HS-SCCHs)

It consists of one or several HS-

PDSCHs along with associatedDPCH combined with several shared

Physicl control Channels(HS-SCCHs)

Spreading Factor HS-DSCH uses fixed SF =16. HS-DSCH uses fixed SF=16 e or SF=1

Terminal Complexity Uses Joint Detection Uses RAKE reciever

Transmit Time

Interval

It uses 10 ms It uses 2ms

TimingReleationships

It needs minimum 5 slots betweenHS- SCCH and start of

Corresponding HS-DSCH TTI

It needs 2 slots between HS- SCCHand start of Corresponding HS-DSCH

TTI

Closed Loop Power Calculates Closed loop Power

Control on HS-SCCH byestimating BLER using HCSN

(HS-SCCH Cyclic Sequence Number)

Not Applicable

Measurement

Report of CQI

It is associated with each HS-

SCCH transmission

It is configured by higher layer

signallingInformation OnDownlink

TFRI carries Resource Allocation

(21- Bit), Modualtion (1- Bit) and

Transport block size(9- Bit)

TFRI carries ChannelisastionCodes(7- Bit), Modulation Scheme(1-

Bit) and Transport block size(6-Bit)

Where can i find basic tutorial on HSDPA?

Please see the following Tutorial.

I would like to follow all HSDPA related News, which is the best place to look for?

The best option is to follow 3G4G blog HSDPA or HSPA tag.

I am a researcher and i would like some references to read more on HSDPA.

References as follows:



[1] 3GPP TR 25.855 - HSDPA; Overall UTRAN Description; Release 5

[2] 3GPP TR 25.858 - HSDPA; Physical Layer Aspects; Release 5

[3] 3GPP TR 29.950 - UTRA High Speed Downlink Packet Access; Release 4

[4] UMTS Evolution to High Speed Downlink Packet Access - Douglas McCarthy

[5] UMTS - High Speed Downlink Packet Access - Rohde & Schwarz

[6] 3GPP TR 25.877 - HSDPA: Iub/Iur Protocol Aspects

[7] 3GPP TR 25.899 - HSDPA Enhancements; Release 5

[8] Nokia: HSDPA Solution White Paper

[9] 3GPP TS 25.211 - Physical Channels and mappin of Transport Channels onto PhysicalChannels; Release 5

[10] Motorola: Fast Cell Selection and Handovers in HSDPA

[11] 3GPP TS 25.308 - HSDPA Overall Description, Stage 2

[12] 3GPP TR 25.890 - HSDPA; UE Radio Transmission and Reception (FDD)

[13] 3GPP TR 25.848 - Physical layer aspects of UTRA High Speed Downlink Packet Access

[14] 3GPP TR 25.876 - Multiple-Input Multiple Output in UTRA

[15] 3G TR 25.835 - Report on Hybrid ARQ Type II/III

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