3g Umts Hspa

download 3g Umts Hspa

of 21

Transcript of 3g Umts Hspa

  • 7/30/2019 3g Umts Hspa


    3G UMTS HSPA - High Speed Packet


    3G HSPA of High Speed packet Access is the combination of twotechnologies, one of the downlink and the other for the uplink that

    can be built onto the existing 3G UMTS or W-CDMA technology

    to provide increased data transfer speeds.

    The original 3G UMTS / W-CDMA standard provided a maximum

    download speed of 384 kbps. With many users requiring much

    high data transfer speeds to compete with fixed line broadband

    services and also to support services that require higher data rates,

    the need for an increase in the speeds obtainable became

    necessary. This resulted in the development of the technologies for

    3G HSPA.

    3G HSPA benefits

    The UMTS cellular system as defined under the 3GPP Release 99

    standard was orientated more towards switched circuit operationand was not well suited to packet operation. Additionally greater

    speeds were required by users than could be provided with the

    original UMTS networks. Accordingly the changes required for 3G

    HSPA were incorporated into many UMTS networks to enable

    them to operate more in the manner required for current


    3G HSPA provides a number of significant benefits that enable thenew service to provide a far better performance for the user. While

    3G UMTS HSPA offers higher data transfer rates, this is not the

    only benefit, as 3G HSPA offers many other improvements as


  • 7/30/2019 3g Umts Hspa


    1.Use of higher order modulation: 16QAM is used in thedownlink instead of QPSK to enable data to be transmitted at

    a higher rate. This provides for maximum data rates of 14

    Mbps in the downlink. QPSK is still used in the uplink where

    data rates of up to 5.8 Mbps are achieved. The data ratesquoted are for raw data rates and do not include reductions in

    actual payload data resulting from the protocol overheads.

    2.Shorter Transmission Time Interval (TTI): The use of ashorter TTI within 3G HSPA reduces the round trip time and

    enables improvements in adapting to fast channel variations

    and provides for reductions in latency.

    3.Use of shared channel transmission: Sharing the resourcesenables greater levels of efficiency to be achieved andintegrates with IP and packet data concepts.

    4.Use of link adaptation: By adapting the link it is possible tomaximize the channel usage.

    5.Fast Node B scheduling: The use of fast scheduling within3G HSPA with adaptive coding and modulation (only

    downlink) enables the system to respond to the varying radio

    channel and interference conditions and to accommodate data

    traffic which tends to be "bursty" in nature.

    6.Node B based Hybrid ARQ: This enables 3G HSPA toprovide reduced retransmission round trip times and it adds

    robustness to the system by allowing soft combining of


    For the network operator, the introduction of 3G HSPA technology

    brings a cost reduction per bit carried as well as an increase in

    system capacity. With the increase in data traffic, and operators

    looking to bring in increased revenue from data transmission, thisis a particularly attractive proposition. A further advantage of the

    introduction of 3G HSPA is that it can often be rolled out by

    incorporating a software update into the system. This means that

    the use of 3G HSPA brings significant benefits to user and

    operator alike.

  • 7/30/2019 3g Umts Hspa


    3G UMTS HSPA constituents

    There are two main components to 3G UMTS HSPA, eachaddressing one of the links between the base station and the user

    equipment, i.e. one for the uplink, and one for the downlink.

    Uplink and downlink transmission directions

    The two technologies were released at different times through

    3GPP. They also have different properties resulting from the

    different modes of operation that are required. In view of these

    facts they were often treated as almost separate entities. Now they

    are generally rolled out together. The two technologies are

    summarized below:

    HSDPA - High Speed Downlink Packet Access: HSDPAprovides packet data support, reduced delays, and a peak raw

    data rate (i.e. over the air) of 14 Mbps. It also provides

    around three times the capacity of the 3G UMTS technology

    defined in Release 99 of the 3GPP UMTS standard.

    HSUPA - High Speed Uplink Packet Access: HSUPAprovides improved uplink packet support, reduced delays anda peak raw data rate of 5.74 Mbps. This results in a capacity

    increase of around twice that provided by the Release 99


  • 7/30/2019 3g Umts Hspa


    Beyond 3G HSPA

    With the elements of 3G HSPA launched, further evolutions were

    in the pipeline. The first of these was known as HSPA+ or Evolved

    HSPA. The evolved HSPA or HSPA+ provides data rates up to 42Mbps in the downlink and 11 Mbps in the uplink (per 5MHz

    carrier) which it achieves by using high order modulation and

    MIMO (multiple input, multiple output) technologies.

    In addition to 3G HSPA, and its evolutions, the next evolution for

    3G UMTS is known as LTE - Long Term Evolution. This uses a

    completely different air interface that is based around OFDM as

    the modulation format. While many operators have opted to

    migrate directly from UMTS to LTE, the majority are using 3G

    HSPA to upgrade their existing 3G networks.

    3G UMTS HSPA and 3GPP standards

    The new high speed technology is part of the 3G UMTS evolution.

    It provides additional facilities that are added on to t e basic 3GPP

    UMTS standard. The upgrades and additional facilities wereintroduced at successive releases of the 3GPP standard.

    Release 4: This release of the 3GPP standard provided forthe efficient use of IP, a facility that was required because the

    original Release 99 focused on circuit switched technology.

    Accordingly this was a key enabler for 3G HSDPA.

    Release 5: This release included the core of HSDPA itself.It provided for downlink packet support, reduced delays, araw data rate (i.e. including payload, protocols, error

    correction, etc) of 14 Mbps and gave an overall increase of

    around three over the 3GPP UMTS Release 99 standard.

    Release 6: This included the core of HSUPA with anenhanced uplink with improved packet data support. This

  • 7/30/2019 3g Umts Hspa


    provided reduced delays, an uplink raw data rate of 5.74

    Mbps and it gave an increase capacity of around twice that

    offered by the original Release 99 UMTS standard. Also

    included within this release was the MBMS, Multimedia

    Broadcast Multicast Services providing improved broadcastservices, i.e. Mobile TV.

    Release 7: This release of the 3GPP standard includeddownlink MIMO operation as well as support for higher

    order modulation up to 64 QAM in the uplink and 16 QAM

    in the downlink. However it only allows for either MIMO or

    the higher order modulation. It also introduced protocol

    enhancements to allow the support for Continuous Packet

    Connectivity (CPC). Release 8: This release of the standard defines dual carrier

    operation as well as allowing simultaneous operation of the

    high order modulation schemes and MIMO. Further to this,

    latency is improved to keep it in line with the requirements

    for many new applications being used.

    HSPA summary

    3G HSPA is widely deployed and providing significantly increased

    data transfer rates required for the variety of data applications

    including mobile broadband for Internet connectivity now being

    used by mobile users. As 3G UMTS HSPA is normally a relatively

    straightforward upgrade based around a software change, its

    incorporation involves a relatively low cost upgrade. As the use of

    3G HSPA is able to increase the efficiency of the overall network,

    reducing the cost per bit, then it is often a very cost effective


  • 7/30/2019 3g Umts Hspa


    3G UMTS HSDPA - High Speed

    Downlink Packet Access

    3G HSDPA High Speed Downlink Packet Access is an upgrade tothe original 3G UMTS cellular system that provides a much greater

    download speeds for data. With more data being transferred across

    the downlink than the uplink for data-centric applications, the

    upgrade to the downlink was seen as a major priority. Accordingly

    3G UMTS HSDPA was introduced into the 3GPP standards as

    soon as was reasonably possible, the uplink upgrades following on

    slightly later.

    3G UMTS HSDPA significantly upgrades the download speeds

    available, bring mobile broadband to the standards expected by

    users. With more users than ever using cellular technology for

    emails, Internet connectivity and many other applications, HSDPA

    provides the performance that is necessary to make this viable for

    the majority of users.

    Key 3G HSDPA technologies

    The 3G HSDPA upgrade includes several changes that are built

    onto the basic 3GPP UMTS standard. While some are common to

    the companion HSUPA technologies added to the uplink, others

    are specific to HSDPA High Speed Downlink Packet Access,

    because the requirements for the each direction differ.

    Modulation:One of the keys to the operation of HSDPA isthe use of an additional form of modulation. Originally W-

    CDMA had used only QPSK as the modulation scheme,

    however under the new system16-QAM which can carry a

    higher data rate, but is less resilient to noise is also used

    when the link is sufficiently robust. The robustness of the

  • 7/30/2019 3g Umts Hspa


    channel and its suitability to use 16-QAM instead of QPSK is

    determined by analyzing information fed back about a variety

    of parameters. These include details of the channel physical

    layer conditions, power control, Quality of Service (QoS),

    and information specific to HSDPA. Fast HARQ: Fast HARQ (hybrid automatic repeat request),

    has also been implemented along with multi-code operation

    and this eliminates the need for a variable spreading factor.

    By using these approaches all users, whether near or far from

    the base station are able to receive the optimum available

    data rate.

    Improved scheduling: Further advances have been made inthe area of scheduling. By moving more intelligence into thebase station, data traffic scheduling can be achieved in a

    more dynamic fashion. This enables variations arising from

    fast fading can be accommodated and the cell is even able to

    allocate much of the cell capacity for a short period of time to

    a particular user. In this way the user is able to receive the

    data as fast as conditions allow.

    Additional channels: In order to be able to transport thedata in the required fashion, and to provide the additional

    responsiveness of the system, additional channels have been

    added which are described in further detail below.

    Use of 16QAM within HSDPA

    The rate control within HSDPA is achieved dynamically by

    adjusting both the modulation and the channel coding. Both

    16WAM and QPSK are used, the higher order 16QAM modulationbeing used to provide a higher data rate, but it also requires a better

    Eb/N0 (effectively signal to noise ratio). As a result the 16QAM

    modulation format is normally used under high signal conditions,

    e.g. when the mobile is close to the NodeB and in the clear.

  • 7/30/2019 3g Umts Hspa


    The coding rate as well as the modulation are then selected for

    each 2ms TTI by the NodeB according to its assessment of the

    conditions. In this way the rate control mechanism can rapidly

    track the variations that may occur.

    HSDPA Hybrid ARQ and soft combining

    Hybrid ARQ or HARQ is hybrid automatic repeat request and it is

    essentially a form of the more common ARQ error correction

    methodology. When the basic ARQ format is used, error-detection

    information bits are added to data to be transmitted. One form of

    this may be a cyclic redundancy check, CRC. However whenHybrid ARQ is used, forward error correction (FEC) bits are also

    added to the existing error detection bits. The added error detection

    means that Hybrid ARQ performs better than ordinary ARQ in

    poor signal conditions, but the additional overhead can reduce the

    throughput in good signal conditions.

    The combination of Fast Hybrid ARQ and soft combining enables

    the terminal to request the retransmission of data that may be

    received erroneously. This can be done within the adaptive

    modulation and channel coding scheme so that when error-rates

    rise the link can be modified accordingly.

    The user equipment or terminal receives the data and decodes it,

    reporting back the result to the NodeB after the reception of each

    block, and in this way rapid retransmission of any blocks with

    errors can be undertaken. This significantly reduces delays,

    especially under poor radio link conditions or when the link ischanging rapidly.

    Soft combining is a process whereby the user equipment or

    terminal does not discard information it cannot decode. Instead it

  • 7/30/2019 3g Umts Hspa


    retains it to combine with any retransmission data to increase the

    chance of successful decoding of the data.

    A process called Incremental Redundancy (IR) is also used with

    the retransmissions. This process adds additional parity bits inretransmissions to make the data retransmission more robust.

    HSDPA performance

    Using HSDPA scheme it will be possible to achieve peak user data

    rates of 10 Mbps within the 5 MHz channel bandwidth offered

    under 3G UMTS. The new scheme has a number of benefits. Itimproves the overall network packet data capacity, improves the

    spectral efficiency and will enable networks to achieve a lower

    delivery cost per bit. Users will see higher data speeds as well as

    shorter service response times and better availability of services.

    However new mobile designs will need to be able to handle the

    increased data throughput rates. Reports indicate that handsets will

    need to have at least double the memory currently contained within

    handsets. Nevertheless the advantages of 3G HSDPA mean that it

    will be widely used as networks are upgraded and new phones


  • 7/30/2019 3g Umts Hspa


    HSDPA Channels

    A number of new channels were added to the downlink within

    HSDPA to provide the additional data capacity as well as the

    control required. The new HSDPA channels are used in the

    downlink in addition to the existing 3G UMTS channels.

    High Speed Downlink Shared Channel (HS-DSCH)

    The HS DSCH channel is the data transport channel that all active

    HSDPA users connected to the NodeB will use. The use of a

    shared channel is a key characteristic of HSDPA and being acommon resource, the HS-DSCH is dynamically shared between


    The HS-DSCH supports adaptive coding and modulation changing

    to adapt to the changing conditions within the system. The use of

    the 2ms TTI means that scheduling delays are reduced and it also

    enables fast tracking of the channel conditions allowing for the

    optimum use of the available resource.

    It is worth noting that the HS-DSCH is not power controlled but

    rate controlled. This allows the remaining power, after the other

    required channels have been serviced to be used for the HS-DSCH,

    and this means that the overall power available is used efficiently.

    High Speed Signaling Control Channel (HS-SCCH)

    This HSDPA channel is used to signal the scheduling to the users

    every 2 ms according to the TTI. The channel carries three main

    elements of information:

  • 7/30/2019 3g Umts Hspa


    It carries the UE identity to allow specific addressing ofindividual UEs on the shared control channel.

    The HS-SCCH carries the Hybrid ARQ to enable thecombining process to proceed.

    This channel carries the Transport Format and ResourceIndicator (TFRI). This identifies the scheduled resource and

    its transmission format.

    High Speed Dedicated Physical Control Channel(HS-DPCCH)

    This HSDPA channel is used to provide feedback to the schedulerand it is located in the uplink. The channel carries the following


    Channel Quality Information which is used to provideinstantaneous channel information to the scheduler.

    HARQ ACK/NAK information which is used to provideinformation back about the successful receipt and decoding

    of information and hence to request the resending

    information that has not been successfully received.

    These channels are added to the existing 3G UMTS channels and

    provide the additional data capability and adaptively required to

    enable the much faster download speeds provided by 3G HSDPA.

  • 7/30/2019 3g Umts Hspa


    HSDPA UE categories and data rates

    Within HSDPA a number of categories are defined. UEs with

    different HSDPA categories will have different characteristics

    including different HSDPA data rates.

    These HSDPA categories are needed to cater for a number of

    different implementations of the HSDPA standard. This allows for

    different levels of performance to be implemented. The

    characteristics of the UE can then be easily communicated to the

    network which can then communicate with the UE in a suitable

    manner. Accordingly these HSDPA categories are widely used.



    Max No of



    Min inter-

    TTI interval

    Data rate



    block size

    Max no

    soft bits

    Supported mo


    1 5 3 3.6 7298 19200 16QAM, QPSK

    2 5 3 3.6 7298 28800 16QAM, QPSK

    3 5 2 3.6 7298 28800 16QAM, QPSK

    4 5 2 3.6 7298 38400 16QAM, QPSK

    5 5 1 3.6 7298 57600 16QAM, QPSK

    6 5 1 3.6 7298 67200 16QAM, QPSK

    7 10 1 7.2 14411 115200 16QAM, QPSK

    8 10 1 7.2 14411 134400 16QAM, QPSK

    9 15 1 10.1 20251 172800 16QAM, QPSK

  • 7/30/2019 3g Umts Hspa


    10 15 1 14 27952 172800 16QAM, QPSK

    11 5 2 1.8 3630 14400 QPSK

    12 5 1 1.8 3630 28800 QPSK

  • 7/30/2019 3g Umts Hspa


  • 7/30/2019 3g Umts Hspa


    The key specification parameters that are introduced by the use of

    HSPA are:

    Increased data rate: The use of HSUPA is able to provide asignificant increase in the data rate available. It allows peakraw data rates of 5.74 Mbps.

    Lower latency: The use of HSUPA introduces a TTI of 2ms, although a 10ms TTI was originally used and is still


    Improved system capacity: In order to enable the largenumber of high data rate users, it has been necessary to

    ensure that the overall capacity when using HSUPA is

    higher. BPSK modulation: Originally only BPSK modulation that

    adopted for UMTS was used. Accordingly it did not support

    adaptive modulation schemes. Higher order modulation was

    introduced in Release 7 of the 3GPP standards when 64QAM

    was allowed.

    Hybrid ARQ: In order to facilitate the improvedperformance the Hybrid ARQ (Automatic Repeat request)

    used for HSDPA is also employed for the uplink, HSUPA.

    Fast Packet Scheduling: In order to reduce latency, fastpacket scheduling has been adopted again for the uplink as

    for the downlink, although the implementation is slightly


    With these specification parameters enable HSUPA to complement

    the performance of HSDPA, providing an overall performance

    improvement for systems incorporating HSPA.

    3G HSUPA basics

    At the core of HSUPA, High Speed Uplink Packet Access is a

    number of new technologies that are very similar to those used

  • 7/30/2019 3g Umts Hspa


    with HSDPA. However there are a few fundamental differences

    resulting from the different conditions at either end of the link.

    The uplink in UMTS, and HSUPA is non-orthogonal becausecomplete orthogonally cannot be maintained between all theUEs. As a result there is more interference between the

    uplink transmissions within the same cells.

    The scheduling buffers are located in a single location(NodeB) for the downlink, whereas for the uplink they are

    distributed within several UEs for the uplink. This requires

    the UEs requiring to send buffer information to the scheduler

    in the NodeB so that it can then provide an overall schedule

    for the data transmission. In the downlink, the shared resource is the transmission

    power. In the uplink, the resource is limited by the level of

    interference that can be tolerated and this depends upon the

    transmission power of the multiple UEs.

    High order modulation techniques are able to provide higherdata rates for high signal level links in the downlink. There is

    not the same advantage in the uplink where as there is no

    need to share canalization codes between users and the

    channel coding rates are therefore lower, although higherorder modulation was introduced under Release 7.

    HSUPA summary

    HSUPA is an integral element of the overall HSPA upgrade for

    UMTS. HSUPA enables much higher data rates to be achieved in

    the uplink and thereby provides a significant improvement. As aresult, the overall UMTS system is able to support data rates more

    in line with those being achieved by wired connections.

  • 7/30/2019 3g Umts Hspa


    HSUPA Category Definitions and Data


    In order to be able to cater for a number of variations in the level towhich HSUPA is implemented, a number of different HSUPA

    categories have been defined. These HSUPA categories allow for

    different levels of performance within the UE. The characteristics

    of the UE can then be easily communicated to the network which

    can then communicate with it in a suitable manner.



    Maximumnumber E-




    Supportfor 2 ms



    block size

    (10 ms TTI)


    block size

    (2 ms TTI)

    Maximumdata rate


    1 1 SF4 - 7110 - 0.7 Mbps

    2 2 SF4 Y 14484 2798 1.4 Mbps

    3 2 SF4 - 14484 - 1.4 Mbps

    4 2 SF2 Y 20000 5837

    2 Mbps for

    10 ms TTI

    2.9 Mbpsfor 2 ms


    5 2 SF2 - 20000 - 2.00 Mbps

    6 2 + 2** SF2 Y 20000 11520

    2 Mbps for10 ms TTI

    5.74 Mbps

    for 2 msTTI

    HSUPA category definitions


    *A 10 ms TTI is supported in all categories

    ** Two E-DPDCHs at SF2 and two at SF4

  • 7/30/2019 3g Umts Hspa


    3G HSUPA channels

    In order to provide the required data speeds and capabilities withinHSUPA, further channels have been added to the basic 3G UMTS

    scheme that is used. These HSUPA channels provide additional

    signaling and data capabilities.

    While HSUPA is effectively an uplink enhancement, channels

    have been added to both the uplink and the downlink. The reason

    for the downlink HSUPA channels is to provide the control, etc

    needed for the uplink data.

    Uplink HSUPA channels

    A variety of new channels have been introduced for HSUPA to

    enable the system to carry the high speed data. These new channels


    E-DCH, the Enhanced Dedicated Channel: Uplink E-DPCCH (Enhanced Dedicated Physical Control

    Channel): Uplink

    E-DPDCH (Enhanced Dedicated Physical Data Channel):Uplink

  • 7/30/2019 3g Umts Hspa


    Downlink HSUPA channels

    A variety of new channels have been introduced for HSUPA to

    enable the system to carry the high speed data. These new channels


    E-AGCH (Enhanced Absolute Grant Channel): Downlink F-DPCH (Fractional-Dedicated Physical Channel):


    E-HICH (Enhanced DCH Hybrid ARQ IndicatorChannel): Downlink

    E-RGCH (Enhanced Relative Grant Channel): Downlink

  • 7/30/2019 3g Umts Hspa


  • 7/30/2019 3g Umts Hspa


    HSPA+ data rate comparison with LTE

    The next migration of the cellular services beyond HSPA+ is

    known as LTE. Using a completely new air interface based around

    the use of OFDM rather than W-CDMA which is used for UMTS,

    HSPA and HSPA+, it offers even higher data traffic rates. It is then

    anticipated that it will be used as the basis for the next generation,

    i.e. 4G systems.

    It is however worth comparing the maximum data rates offered by

    both HSPA+ and LTE.




    HSPA+ data rate


    LTE data rate


    5 42 37

    10 84 73

    20 -- 150