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 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 similarly have HSUPA where U stands for uplink?
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.
Were any of these demos impressive?
According to The Register these demos were quite impressive. They reported that in Orange/Nortel demo seeing good quality video on 5/6 inch screen that was being streamed. Similarly Siemens did demo for real on its boat out in the harbour and Ericsson demoed up to 11Mbps on a yacht.
Is it possible to buy 3G handsets with HSDPA support?
Not yet but they should be available by Q2, 2006.
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.
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 to DL speed to 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 would like to follow all HSDPA related News, which is the best place to look for?
Our News Section generally has collection of all news relating to 3G (including HSDPA) for all major news websites. Please check the links relating to HSDPA in that.
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
[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