TelecomStudy18

What is SIR? SIR is the Signal-to-Interference Ratio – the ratio of the energy in dedicated physical control channel bits to the power density of interference and noise after dispreading. What is RSCP? RSCP stands for Received Signal Code Power – the energy per chip in CPICH averaged over 512 chips. What is Eb/No? By definition Eb/No is energy bit over noise density, i.e. is the ratio of the energy per information bit to the power spectral density (of interference and noise) after dispreading. Eb/No = Processing Gain + SIR For example, if Eb/No is 5dB and processing gain is 25dB then the SIR should be -20dB or better. What are the Eb/No targets in your design? The Eb/No targets are dependent on the service:  on the uplink, typically CS is 5 to 6dB and PS is 3 to 4dB – PS is about 2dB lower.  on the downlink, typically CS has 6 to 7dB and PS is 5 to 6dB – PS is about 1dB lower. Why is Eb/No requirement lower for PS than for CS? PS has a bet...

Handover Parameter maxActiveSet: Maximum number of cells allowed in the Active Set. IndividualOffset: Offset value which can be assigned to each cell. It is added to the measurement quantity before the UE evaluates whether or not an event has occurred. It can either be positive or negative value. measQuantity1: Defines the measurement quantity for intra-frequency reporting evaluation. Default is Ec/No . hsQualityEstimate: Indicates whether Ec/No or RSCP should be used for indicating "best cell" for HS-DSCH Cell Change. Default is RSCP. reportingRange1a: Relative threshold referred to the CPICH of the best cell in the Active Set used as evaluation criteria for event 1a (a primary CPICH enters the reporting range). reportingRange1b: Relative threshold referred to CPICH of the best cell in the Active Set used as evaluation criteria for event 1b (a primary CPICH leaves the reporting range). reportingInterval1a: Time between periodic reports at even...

 e1a – a Primary CPICH enters the reporting range, i.e. add a cell to active set.  e1b – a primary CPICH leaves the reporting range, i.e. removed a cell from active set.  e1c – a non-active primary CPICH becomes better than an active primary CPICH, i.e. replace a cell.  e1d : change of best cell.  e1e : a Primary CPICH becomes better than an absolute threshold.  e1f : a Primary CPICH becomes worse than an absolute threshold.

Advantages:   Overcome fading through macro diversity.   Reduced Node B power which in turn decreases interference and increases capacity.   Reduced UE power (up 4dB), decreasing interference and increasing battery life. Disadvantages:   UE using several radio links requires more channelization codes, and more resources on the Iub and Iur interfaces

GSM:  Time -based mobile measures of RxLev and RxQual – mobile sends measurement report every SACH period (480ms).  BSC instructs mobile to handover based on these reports. UMTS:  Event -triggered reporting – UE sends a measurement report only on certain event “triggers”.  UE plays more part in the handover decision.

Handover: call transfer one cell to another cell without disconnecting There are three types of handover used in WCDMA. 1.    Intra frequency Handover (Soft & Softer ) 2.    Inter frequency handover 3.    IRAT Handover Soft Handover:             WhenHandover between two NodeB within same carrier frequency and add in active set. Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN. Soft handover is performed by means of macro diversity, which refers to the condition that several radio links are active at the same time. Softer Handover:                         When Handover between two cells within same NodeB and ADD in active set. IRAT Handover:    ...

Power Control: We know all users are in same frequency at same time soPower control is used to controlled the level of the transmitting power in order to minimize interference,improve quality of connection, reducing of NEAR-FAR effects and increase capacity of system. There are three type of power control Open loop power control Inner loop Closed loop power control Outer loop closed loop power control Open loop power control:                                       The UE determine an estimation of the downlink path-loss between thee base station and the UE by the measuring of UTRA carrier received signal strength at the mobile through the medium of the SI message on the P-CCPCH.   Outer loop closed loop power control:            ...

What is Congestion Control? Congestion Control monitors the dynamic utilization of specific cell resources and insures that overload conditions do not occur.   If overload conditions do occur, Congestion Control will immediately restrict Admission Control from granting additional resources.   In addition, Congestion Control will attempt to resolve the congestion by either down switching, or terminating existing users.   Once the congestion is corrected, the congestion resolution actions will cease, and Admission Control will be enabled. Parameter of congestion control: PwrAdm:   Admission limit for admission on DL cell carrier power. PwrAdmOffset: Relative admission limit on DL cell carrier power. PwrOffset:   Used by Congestion Control. PwrHyst:   Hysteresis time setting for detection of congestion in the DL transmitted carrier power. iFCong: Threshold at which UL congestion is detected in the cell. iFOffset: Offse...

What is Admission Control? Admission control is used to reduce soft congestion. Admission Control make decision on whether call should be admitted or NOT. It could be new call or handover call. In case, if a cell is heavily a loaded and enough resources in terms of power, codes or CEs are not available. One of the following reasons to reject adm attempt: -        OVSF code resource is low -        Iub bandwidth resource is low -        CPU resource is low -        Call request is rejected by CAC module for DCH. Parameter of Admission control: Admission Control will be disabled in the RNC when ulHwAdm and dlHwAdm are set to 100. UlHwAdm: Admission limit on RBS UL HW resource utilization applicable to non-handover guaranteed admission requests. This parameter is also used together with beMarginUlHw for non-handover non-guaranteed admission requ...

Idle Mode Parameter: qQualMin: Minimum required quality level in the cell measured in the UE. qRxLevMin: Parameter that indicates the min. required signal strength in the cell qualMeasQuantity: Used for decision as to whether the 3G ranking for cell selection and reselection is based on Ec/No or RSCP. Default is Ec/No. qHyst1: Hysteresis values used for serving cell, when ranking is based on CPICH RSCP qHyst2: Hysteresis values used for serving cell, when ranking is based on CPICHEc/No qOffset1sn: Signal strength offset b/w source and target cell for cell ranking based on CPICH RSCP. qOffset2sn: Signal offset between serving cell and neighbor cell, based on CPICHEc/No. sIntraSearch: Decision on when intra-freq. measurements should be performed. Following criteria is used: sIntraSearch ≥ qQualmeas - qQualMin (where qQualmeas is the value measured by UE ) sInterSearch: Parameter is used to make decision to start inter-freq. measurements. sInterS...

What are the RRC operation modes? There are two types of Mode  1. Idle mode  2. Connected mode. There are 4 RRC States: Cell_DCH, Cell_FACH, URA_PCH and Cell_PCH. Idle Mode: In idle mode, after the UE is switch ON and UE is able to receive system information message from cell. CELL_DCH: In this state dedicated physical channel is allocated to the UE in UL and DL active set level CELL_FACH: No dedicated channel is allocated to UE, But RACH and FACH cannel can be used, both transferring signaling message and small amount of data. And in this state UE perform cell re-selection and after a reselection always send a cell update message to RNC CELL_PCH: In this state UE perform to monitoring of paging information URA_PCH: It is similar to CELL_PCH expected that the UE does not execute cell update after each re-selection, but instead read URA (UTRA registration area) identities from the broadcast channel.

Cell Search procedure: During the cell search, the mobile station searches for a cell and determines the downlink scrambling code and common channel frame synchronization of that cell. The cell search is typically carried out in three steps: slot synchronization; frame synchronization and code-group identification; and scrambling-code identification. Step 1: Slot synchronization . During the first step of the cell search procedure, the mobile station uses the SCH’s primary synchronization code to acquire slot synchronization to a cell. This can be done with a single matched filter matched to the primary synchronization code that is common to all cells. Step 2: Frame synchronization and code-group identification. During the second step of the cell search procedure, the mobile station uses the SCH’s secondary synchronization code to find frame synchronization and identify the code group of the cell found in the first step. This is done by correlating the received signa...

Briefly describe UMTS air interface channel types and their functions. There are 3 types of channels across air interface – physical channel, transport channel and logical channel: ·          Physical Channel: carries data between physical layers of UE and NodeB. ·          Transport Channel: carries data between physical layer and MAC layer. ·          Logical Channel: carries data between MAC layer and RRC layer. 1.      Logical Channel: ·          Control channel:   BCCH, PCCH, CCCH, DCCH. ·          Traffic channel:     DTCH, CTCH. 2 . Transport Channel: ·          Common control channel:   BCH, FACH, PCH, RACH, CPCH. ·          Dedi...