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Thread: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Carrier

  1. #1
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    Default Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Carrier

    Dear All,

    We have second carrier, F1 for R99 service & F2 for HSDPA service.
    now we set DRD ON, BlindHoFlag TRUE, & Cell Bar F2 in order to direct HSDPA service to F2

    I need enlightenment about the differences between the DRD (Directed Retry Decision) and the blind handover.
    Should it be set concurrently or independent?

    As I know there is 3 parameter for DRD:
    Recommended Value: DR_RRC_DRD_SWITCH:ON,DR_RAB_SING_DRD_SWITCH:ON,DR_RAB_COMB_DRD_SWITCH:OFF
    and for blind handover we need to set the FLAG to TRUE

    What will happen during call setup if we set parameter as below scenario?
    1. DRD ON & BlindHoFlag FALSE
    2. DRD OFF & BlindHoFlag TRUE
    3. DRD OFF & BlindHoFlag FALSE

    Thanks

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  3. #2
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    2 out of 2 members found this post helpful.

    Default Re: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Car

    According Huawei's implementation:

    There are two types of blind handover
    >Emergent blind handover is triggered by 1F event (e.g. whenever UE loses coverage) which indicates the used frequency becomes worse. The UE must perform emergent handover to avoid call drops.
    >Non-emergent blind handover may be triggered by procedures such as LDR, DRD, or HCS speed estimation

    DRD is typically executed during RAB setup, this is the non-periodic DRD. effectivelly non-periodic DRD forces the establishment of a RAB to a specific frequency (or even to the least loaded frequency).

    For Huawei, there are two different ways to push traffic for non-periodic DRD (operator must decide which of the two should use):

    1. Measurement based non-periodic DRD: RNC orders the UE to endter CM and perform inter-frequency meansurements. if a suitable inter-frequency cell is found then the RNC orders the UE to establish the RAB to that cell

    2. Blind-handover based non-periodic DRD: No measurements are performed and UE is ordered to go directly to target inter-frequency cell

    there are no restrictions in havind non-periodic DRD and emergent blind handover (due to coverage)

    > Non-periodic DRD = OFF, emergent blind handover = ON
    > Non-periodic DRD = measurement-based, emergent blind handover = ON
    > Non-periodic DRD = blind-handover, emergent blind handover = ON
    > Non-periodic DRD = measurement-based, emergent blind handover = OFF
    > Non-periodic DRD = blind-handover, emergent blind handover = OFF

    etc

    Hope this helps!

  4. #3
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    Default Re: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Car

    What about periodic DRD? when this is used?

  5. #4
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    1 out of 1 members found this post helpful.

    Default Re: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Car

    Quote Originally Posted by fuzzy_animals View Post
    What about periodic DRD? when this is used?
    Hi, I found good document here:

    http://www.finetopix.com/showthread....038#post156038

    Overview:
    Periodic DRD => After RAB setup or after the bearer scheme is changed

    Periodic DRD is used to select a suitable cell according to the device type
    priority, technological satisfaction and service priority.

    It can be performed to select a suitable cell when the RNC determines
    that the UE can be served by a better HSPA/HSPA+ technology or when a
    neighboring cell has a higher service priority than the current cell.

    After periodic DRD is triggered, it can be performed through either of the
    following two ways:
    1. Blind‐handover‐based periodic DRD: It mainly applies to the
    inter‐frequency co‐coverage scenarios. It selects the target cell
    that support blind handover and does not consider the signal
    quality of the target cell.
    2. Measurement‐based periodic DRD: It applies to both the interfrequency
    different‐coverage scenarios and the inter‐frequency
    co‐coverage scenarios. It selects the target cell according to
    the signal measurement results. Only the cell that meets the
    specified signal conditions can be selected as the target cell.
    Note that only measurement‐based periodic DRD can be
    triggered by cell service priority.

    Blind‐handover‐based periodic DRD cannot work with measurementbased
    periodic DRD. When the latter is enabled, the former is disabled
    automatically.

  6. #5
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    Default Re: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Car

    I still bit confuse about DRD during RRC.
    if RRC fail then it will go through DRD, in case DRD sucsess whether RRC fail will be counted in counter or not?
    How about retransmissions of the RRC CONNECTION REQUEST (N300 = 3), is it work before or after DRD?

  7. #6
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    Default Re: Difference between the DRD (Directed Retry Decision) and blind handover- 2nd Car

    "VS.RRC.Estab.DRDOut.Att" measures the no. of RRC DRD out from cell. RRC fails are not counted if RRC is successfully directed to another cell. N300 is applicable in different scenario, UE sends RRC Request and waits for response, if no response received in Timeframe; the request is repeated as per N300. But in case of RRC DRD, RNC receives the request and sends RRC connection setup, pushing UE to another frequency.
    Last edited by jayk; 2012-03-21 at 05:21 AM

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