HSDPA (High Speed Downlink Packet Access) is an enhancement to 3G technology that increases download speeds from 384 Kbps to 10 Mbps. HSDPA works by improving spectral efficiency and introducing fast channel control mechanisms. It uses a high speed downlink shared channel and adaptive modulation and coding to boost speeds. While part of 3G, HSDPA is also referred to as 3.5G. HSUPA provides similar enhancements for the uplink. Networks have rolled out HSDPA widely and compatible phones are available. References on HSDPA specifications and technologies are provided.

1. High Speed Downlink Packet Access
(HSDPA) FAQ
By Zahid Ghadialy (zahidtg@yahoo.com)
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 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).
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.

2. 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 different
countries 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 is
a 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, to
handle 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 to
LTE.
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 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 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).
Is HSDPA applicable 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.
Is HSDPA applicable in CELL_FACH or CELL_DCH or both the UE states.
HSDPA is only applicable to CELL_DCH state.

3. Can you give comparison of HSDPA in FDD & TDD Mode?
With respect to TDD FDD
Uplink Uses HS-SICH (Shared Uses an associated uplink dedicated
Information Channel ) to control channel (DPCCH-HS) to send
send Ack/Nack & CQ I to Node- Ack/Nack, CQI to Node-B.
B
DownLink It consists of associated Dedicated It consists of one or several HS-
Physical Channels and shared PDSCHs along with associated
Control Channels(HS-SCCHs) 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 It uses 10 ms It uses 2ms
Interval
Timing It needs minimum 5 slots between It needs 2 slots between HS- SCCH
Releationships HS- SCCH and start of and start of Corresponding HS-DSCH
Corresponding HS-DSCH TTI TTI
Closed Loop Power Calculates Closed loop Power Not Applicable
Control on HS-SCCH by
estimating BLER using HCSN
(HS-SCCH Cyclic Sequence
Number)
Measurement It is associated with each HS- It is configured by higher layer
Report of CQI SCCH transmission signalling
Information On TFRI carries Resource Allocation TFRI carries Channelisastion
Downlink Codes(7- Bit), Modulation Scheme(1-
(21- Bit), Modualtion (1- Bit) and Bit) and Transport block size(6-Bit)
Transport block size(9- 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:

4. [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 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
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