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FAQ High Speed Downlink Packet Access

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


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

 Why not similarly have HSUPA where U stands for uplink?

There is already a HSUPA.

 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.

 Can you give comparison 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 of CQI
It is associated with each HS-SCCH transmission
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)

 Where can i find basic tutorial on HSDPA?

Please see the following Tutorial.

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

References as follows: