High Speed Downlink Packet Access FAQ

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High Speed Downlink Packet Access (HSDPA) FAQ

By Zahid Ghadialy ([email protected])

Last Updated: 01/10/2005

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 data rates 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).

I nteresting! I s HSDPA part of 3G or wil l i t be part of 4G?

HSDPA is part of 3G but people have started referring it as 3.5G. Some other group has started referring to

HSDPA as 'Super-3G' but they have proposed more enhancements (details below).

Why not similarl y have HSUPA where U stands for upli nk?

3GPP is working towards HSUPA as well but there are no clear details yet. Theoretically HSUPA is suppose

to boost the uplink speed to 3.5Mbps. And it dosent stop here. There are further plans to introduce HSOPA

where O stands for OFDM (orthogonal frequency division multiplexing). This will increase the download

capacity to 40Mbps.

Are any major Network Providers or Service Providers working on HSDPA?

In the 3GSM exhibition in Cannes this year all major operators were demonstrating HSDPA in their networks.

Orange and Nortel Networks have demonstrated it on live spectrum and Orange plans to launch 3G with

HSDPA in Q2, 2006. NTT DoCoMo also plans to launch it by Q2, 2006. O2 is planning HSDPA network in

Isle of Man around September 2005. O2 claims its HSDPA enabled network will ultimately support data

speeds of up to 14.4Mbps. Ericsson has been conducting HSDPA trials in Stockholm, Sweden, for more than a

year, but this system is only capable of delivery data rates of around 5Mbps.

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 toThe RegisterHSDPA is a power-

hungry technology, and many of the base stations out there arent up to the job. The key piece of technology is

the power amplifier, which has to be a full power, 45-watt model, to handle the extra data output.

What could be the possible uses of HSDPA?

The same use as that of Broadband connections at home. It would be possible to watch extremely 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 incr ease the speed to DL speed to 10Mbps?

To increase the data rates a new channel called HS-DSCH (High speed downlink shared channel) was defined.
http://www.theregister.co.uk/2005/02/16/hsdpa_3g_demo/http://www.theregister.co.uk/2005/02/16/hsdpa_3g_demo/http://www.theregister.co.uk/2005/02/16/hsdpa_3g_demo/http://www.theregister.co.uk/2005/02/16/hsdpa_3g_demo/


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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 support this 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).

I s HSDPA appli cable for CS and PS RABs both?

In release 5 HSDPA is only applicable for PS streaming/interactive/background RABs. In release 6, HSDPA

will be used for Signalling Radio Bearers as well.

I s HSDPA appli cable in CELL_FACH or CELL_DCH or both the UE states.

HSDPA is only applicable to CELL_DCH state.

Can you give compari son of HSDPA in FDD & TDD Mode?

With respect to TDD FDD

Uplink Uses HS-SICH (Shared Information

Channel ) to send Ack/Nack & CQ I to

Node-B

Uses an associated uplink dedicated control

channel (DPCCH-HS) to send

Ack/Nack, CQI to Node-B.

DownLink It consists of associated Dedicated

Physical Channels and shared Control

Channels(HS-SCCHs)

It consists of one or several HS-PDSCHs

along with associated DPCH 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

Timing Releationships It needs minimum 5 slots between HS-

SCCH and start of Corresponding HS-

DSCH TTI

It needs 2 slots between HS- SCCH and

start of Corresponding HS-DSCH TTI

Closed Loop Power Calculates Closed loop Power Control

on HS-SCCH by estimating

BLER using HCSN (HS-SCCH Cyclic

Sequence Number)

Not Applicable

Measurement Report ofCQI

It is associated with each HS-SCCHtransmission

It is configured by higher layer signalling

Information On

Downlink

TFRI carries Resource Allocation

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

Transport block size(9- Bit)

TFRI carries Channelisastion Codes(7- Bit),

Modulation Scheme(1- Bit) and Transport

block size(6-Bit)

I am a researcher and i would li ke 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
http://www.3gpp.org/ftp/Specs/archive/25_series/25.855/http://www.3gpp.org/ftp/Specs/archive/25_series/25.855/http://www.3gpp.org/ftp/Specs/archive/25_series/25.855/http://www.3gpp.org/ftp/Specs/archive/25_series/25.858/http://www.3gpp.org/ftp/Specs/archive/25_series/25.858/http://www.3gpp.org/ftp/Specs/archive/25_series/25.858/http://www.3gpp.org/ftp/Specs/archive/25_series/25.858/http://www.3gpp.org/ftp/Specs/archive/25_series/25.855/


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[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 Physical Channels; 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
http://www.3gpp.org/ftp/Specs/archive/25_series/25.950/http://www.3gpp.org/ftp/Specs/archive/25_series/25.950/http://engr.smu.edu/~jseraj/2003_termpapers/Douglas%20Mc%20Carthy%20Term_Paper_HSDPA.dochttp://engr.smu.edu/~jseraj/2003_termpapers/Douglas%20Mc%20Carthy%20Term_Paper_HSDPA.dochttp://www.3gpp.org/ftp/tsg_t/WG1_Test/TSGT1_22_India/tdocs/T1-040140.ziphttp://www.3gpp.org/ftp/tsg_t/WG1_Test/TSGT1_22_India/tdocs/T1-040140.ziphttp://www.3gpp.org/ftp/tsg_t/WG1_Test/TSGT1_22_India/tdocs/T1-040140.ziphttp://www.3gpp.org/ftp/Specs/archive/25_series/25.877/http://www.3gpp.org/ftp/Specs/archive/25_series/25.877/http://www.3gpp.org/ftp/Specs/archive/25_series/25.899/http://www.3gpp.org/ftp/Specs/archive/25_series/25.899/http://www.nokia.com/downloads/aboutnokia/press/pdf/HSDPA_A4.pdfhttp://www.nokia.com/downloads/aboutnokia/press/pdf/HSDPA_A4.pdfhttp://www.nokia.com/downloads/aboutnokia/press/pdf/HSDPA_A4.pdfhttp://www.3gpp.org/ftp/Specs/archive/25_series/25.211/http://www.3gpp.org/ftp/Specs/archive/25_series/25.211/http://www.3gpp.org/ftp/Specs/archive/25_series/25.211/http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_AHs/2001_01_Study_Items/R2A010017.ziphttp://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_AHs/2001_01_Study_Items/R2A010017.ziphttp://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_AHs/2001_01_Study_Items/R2A010017.ziphttp://www.3gpp.org/ftp/Specs/archive/25_series/25.308/http://www.3gpp.org/ftp/Specs/archive/25_series/25.308/http://www.3gpp.org/ftp/Specs/archive/25_series/25.308/http://www.3gpp.org/ftp/Specs/archive/25_series/25.890/http://www.3gpp.org/ftp/Specs/archive/25_series/25.890/http://www.3gpp.org/ftp/Specs/archive/25_series/25.890/http://www.3gpp.org/ftp/Specs/archive/25_series/25.848/http://www.3gpp.org/ftp/Specs/archive/25_series/25.848/http://www.3gpp.org/ftp/Specs/archive/25_series/25.848/http://www.3gpp.org/ftp/Specs/archive/25_series/25.876/http://www.3gpp.org/ftp/Specs/archive/25_series/25.876/http://www.3gpp.org/ftp/Specs/archive/25_series/25.835/http://www.3gpp.org/ftp/Specs/archive/25_series/25.835/http://www.3gpp.org/ftp/Specs/archive/25_series/25.835/http://www.3gpp.org/ftp/Specs/archive/25_series/25.876/http://www.3gpp.org/ftp/Specs/archive/25_series/25.848/http://www.3gpp.org/ftp/Specs/archive/25_series/25.890/http://www.3gpp.org/ftp/Specs/archive/25_series/25.308/http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_AHs/2001_01_Study_Items/R2A010017.ziphttp://www.3gpp.org/ftp/Specs/archive/25_series/25.211/http://www.nokia.com/downloads/aboutnokia/press/pdf/HSDPA_A4.pdfhttp://www.3gpp.org/ftp/Specs/archive/25_series/25.899/http://www.3gpp.org/ftp/Specs/archive/25_series/25.877/http://www.3gpp.org/ftp/tsg_t/WG1_Test/TSGT1_22_India/tdocs/T1-040140.ziphttp://engr.smu.edu/~jseraj/2003_termpapers/Douglas%20Mc%20Carthy%20Term_Paper_HSDPA.dochttp://www.3gpp.org/ftp/Specs/archive/25_series/25.950/

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