Downlink Channel Codes and Levels

Downlink Channel Codes

Downlink Channel Codes can not be changed in Active Cell operating mode (use Cell Off operating mode to change the active cell downlink channel codes). The downlink channel codes currently in use are displayed in the Downlink Code Channel Information window.

Shared DL Channel Codes

• Primary Scrambling Code

  GPIB command: CALL:SCODe

• S-CCPCH Channelization Code

  The S-CCPCH OVSF (Orthogonal Variable Spreading Factor) is fixed at 64. This parameter cannot be set to 26 when RB Test Mode First HS-PDSCH Channel Code or PS Data First HS-PDSCH Channel Code is set to 5 or 6.

  GPIB command: CALL:CCPChannel:SECondary:CCODe:CODE

• PICH Channelization Code

  The PICH OVSF is fixed at 256.

  GPIB command: CALL[:CELL]:PICHannel:CCODe:CODE

• AICH Channelization Code

  The AICH OVSF is fixed at 256.

  GPIB command: CALL:AICHannel:CCODe:CODE

The CPICH OVSF/channelization code is fixed at 256,0.

The P-CCPCH/SCH OVSF/channelization code is fixed at 256,1.

WCDMA DL Channel Codes

The method for setting downlink DPCH channel codes differs between the test application and lab application. The following table illustrates the valid channelization codes for each type of DPCH channel, and indicates the GPIB commands and front panel fields used to set the channelization codes, for both the test application and lab application (see How Do I Change Generator Information? to help you find these fields from the front panel).

HSDPA/HSPA DL Channel Codes

This section is only applicable to the lab application or feature-licensed test application.

The method for setting downlink DPCH channel codes used during HSDPA and HSPA connections differs between the test application and lab application. The following table illustrates the valid channelization codes for each type of DPCH channel used during HSDPA and HSPA connections, and indicates the GPIB commands and front panel fields used to set the channelization codes, for both the test application and lab application (see How Do I Change Generator Information? to help you find these fields from the front panel).

You can also set the channel code for the following downlink HSDPA and HSPA channels:

• E-AGCH Channelization Code

  This setting controls the channelization code of the E-AGCH. The E-AGCH has a spreading factor of 256.

  GPIB command: CALL[:CELL]:EAGChannel:CCODe:CODE

• E-HICH/E-RGCH Channelization Code

  This setting controls the channelization code of the E-HICH and E-RGCH. These channels have a spreading factor of 128 and by definition use the same channelization code (see 3GPP TS 25.213 s5.2.1). 40 bit signatures are used to provide orthogonality between the two channels (see HSPA Downlink Channel Details ).

  GPIB command: CALL[:CELL]:EHIChannel:CCODe:CODE

• PS Data First HS-PDSCH Channel Code

  This parameter sets the channelization code of the first HS-PDSCH when on an HSDPA packet data connection. If more than one HS-PDSCH is being generated, the other HS-PDSCHs are assigned to the subsequent channelization codes.

  This parameter cannot be set to 5 or 6 when S-CCPCH Channelization Code is set to 26. Also, the number of HS-PDSCHs specified by the PS Data Configuration Type , when added to the PS Data First HS-PDSCH Channel Code cannot exceed 15 (otherwise the HS-PDSCHs would collide with the downlink OCNS channels).

  GPIB command: CALL:HSDPa:SERVice:PSData:HSPDschannel:CCODe:CODE

• RB Test Mode First HS-PDSCH Channel Code

  This parameter sets the channelization code of the first HS-PDSCH when on an HSDPA RB Test Mode connection. If more than one HS-PDSCH is being generated, the other HS-PDSCHs are assigned to the subsequent channelization codes.

  This parameter cannot be set to 5 or 6 when S-CCPCH Channelization Code is set to 26. This parameter cannot be set to 5 when HSDPA DPCH 12.2k RMC Channelization Code is set to 45 or 54, and cannot be set to 6 when HSDPA DPCH 12.2k RMC Channelization Code is set to 54. Also, the number of HS-PDSCHs specified by the FRC Type or User Defined Number of Active HS-PDSCHs settings, when added to the RB Test Mode First HS-PDSCH Channel Code cannot exceed 15 (otherwise the HS-PDSCHs would collide with the downlink OCNS channels).

  GPIB command: CALL:HSDPa:SERVice:RBTest:HSPDschannel:CCODe:CODE

• HS-SCCH 1 Channelization Code

  GPIB command: CALL:HSSCchannel[1]:CCODe:CODE

• HS-SCCH 2 Channelization Code

  GPIB command: CALL:HSSCchannel2:CCODe:CODE

• HS-SCCH 3 Channelization Code

  GPIB command: CALL:HSSCchannel3:CCODe:CODE

• HS-SCCH 4 Channelization Code

  GPIB command: CALL:HSSCchannel4:CCODe:CODE

Downlink Channel Levels Overview

The relative level of all downlink channels can be individually set or turned off (except that the P-CCPCH and the SCH are time multiplexed, and use the same level for both channels). The level of each active channel is a fraction of the Cell Power (Îor) setting, expressed in dB. If the summed level of all channels is less than one, the orthogonal coded noise source (OCNS) is turned on to account for the difference (see Orthogonal Channel Noise Simulator (OCNS) ).

The downlink code channel levels currently in use (as well as the "desired" levels) are displayed in the Downlink Code Channel Information screen.

The downlink channel levels for idle mode (no DPCH is present) may be different than the levels used during a call (DPCH is present). Thus, there are two different level settings for the downlink channels in active cell operating mode: Downlink Channel Levels and Connected DL Channel Levels .

Considerations When Setting Code Channel States and Levels

• All code channels can be set between 0 and -20 dB, except the relative power level of the DPCH channel which can be set from 0 to -30 dB.
• Any code channel powers that are On must not be greater than 30 dB below the Total RF Power .
• The sum of the relative levels of the code channels cannot be greater than 100% of the cell power.
• If you set a code channel state to Off , the test set will not automatically turn it back on if it is needed to perform a call processing operation you've requested (for example, if you turn PICH Level to Off , the Originate Call procedure will fail).

Orthogonal Channel Noise Simulator (OCNS)

OCNS is used to simulate additional users on the downlink. OCNS is automatically enabled when the sum of the levels of all the enabled downlink physical channels is less than the cell power setting.

Cell 1 OCNS is made up of the following 16 separate code channels: 2, 11, 17, 23, 31, 38, 47, 55, 62, 69, 78, 85, 94, 113, 119, and 125, with an OVSF of 128. The fraction of the composite OCNS power that is allocated to each of the code channels making up the composite OCNS are as specified by 3GPP TS 34.121 sE.3.6.

Cell 2 OCNS ( lab application only ) consists of a single channel at OVSF 128,2.

As individual downlink channel levels are adjusted, the composite OCNS level is automatically set to a value equal to the difference between the summed downlink channel levels and the cell power setting (when the sum of the downlink code channel levels is such that the composite OCNS is less than -30 dB, it is set to Off ).

The OCNS currently in use (as well as the "desired" level) is displayed in the Downlink Code Channel Information window.

GPIB command: CALL:OCNSource (query only)

OCNS in HSDPA/HSPA

This section is only applicable to the lab application or feature-licensed test application.

When HSDPA or HSPA is active (see HSDPA Activation in FDD Test and HSDPA Activation in Active Cell ), the cell 1 OCNS is made up of the following 7 separate code channels: 122, 123, 124, 125, 126, and 127, with an OVSF of 128, rather than the code channels described in Orthogonal Channel Noise Simulator (OCNS) above. The fraction of the composite OCNS power that is allocated to each of the code channels making up the composite OCNS are as specified by 3GPP TS 34.121 sE.5.2.

Related Topics

Generator Information

How Do I Change Generator Information?

Cell Power and AWGN Power

Signalling Radio Bearer (SRB) Parameters

Active Cell Operating Mode

Cell Off Operating Mode