Advanced Mode

NI-RFmx Waveform Creator User Guide 2.4

Edition Date: November 2017

Part Number: 377063C-01

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In advanced mode of GSM/EDGE modulation, a single carrier frequency signal can be generated with the following characteristics:

    Slot-0 always configured as BCCH carrier.
    Slot-1 to Slot-7 configured to carry TCH/SACCH, PDTCH or Dummy burst.

You can generate the test signals for GSM/GPRS/EDGE.

Under Modulation Tab, the following properties can be configured:

  • Number of Frames

Under Frame Config tab, following properties can be configured:

  • Network Color Code
  • Base Color Code
  • Channel Type
  • Data Type
  • Training Sequence
  • Power Control Level (PCL)
  • Fast Power Control (FPC)
  • Modulation and Coding Scheme (MCS)
  • MAC Header
  • Data Source

Multiframes, Superframes, and Hyperframes

The longest recurrent time period of the structure is called hyperframe and has a duration of 3h 28mn 53s 760ms. The TDMA frames are numbered modulo this hyperframe (TDMA frame number, or FN, from 0 to 2,715,647). A hyperframe is subdivided in 2048 superframes which have duration of 6.12 seconds. The superframe is the least common multiple of the time frame structures. The superframe is itself subdivided in multiframes.

The following multiframes are supported by GSM/EDGE modulation in Advanced Mode of operation:

  • 51- multiframe (26 per superframe) with duration of 235.4 ms (3060/13 ms), comprising 51 TDMA frames. This multiframe is used to carry BCCH, CCCH.


    Fig. 3-9: 51-frame Multiframe


  • 26- multiframe (51 per superframe) with duration of 120 ms, comprising 26 TDMA frames. This multiframe is used to carry TCH (and SACCH/T).


    Fig. 3-10: 26-frame Multiframe


  • 52-multiframe (25.5 per superframe) with duration of 240 ms, comprising 52 TDMA frames. This multiframe is used to carry PDTCH.


    Fig. 3-11: 52-frame Multiframe


Logical Channels

The following logical channels are supported by GSM/EDGE modulation in the Advanced mode of operation:

  1. Frequency correction channels (FCCH): The frequency correction channel carries information for frequency correction of the mobile station.
  2. Synchronization channel (SCH): The synchronization channel carries information for frame synchronization of the mobile station and identification of a base transceiver station.
  3. Broadcast control channel (BCCH): The broadcast control channel broadcasts general information on a base transceiver station per base transceiver station basis. The contents of the BCCH channel are internally configured by GSM/EDGE Modulation.
  4. Common control channel (CCCH): Intended to carry common control signalling in circuit switched mode. The contents of the CCCH channel are internally configured by GSM/EDGE Modulation.
  5. Full rate traffic channel (TCH/F): Intended to carry either encoded speech or user data in circuit switched mode.
  6. Full rate packet data traffic channel (PDTCH/F): Intended to carry user data in packet switched mode.
  7. Slow Associated Control Channel (SACCH/M): Provides a relatively slow signalling connection and is associated with traffic channel TCH/F. The contents of the SACCH channel are internally configured by GSM/EDGE Modulation.

The channels listed above, are not exposed for configuration and are configured by the GSM/EDGE modulation based on the user settings. For example, slot-0 always carries all the BCCH information required for synchronization. The SCH Frame Numbers are internally calculated based on the number of frames to be generated and always start from 1.

For all the modulation schemes, the stealing flags as per the following table are inserted before burst mapping.



Table 3-3 Stealing Flags



The following figure displays the resulting burst in the radio block after burst mapping (Bit swapping is not shown in the figure).

For CS-1 to CS-4 and

MCS-1 to MCS-4:



Fig. 3-12 Burst mapping before bit swapping for each burst in the Radio Block


When advanced mode is selected, the main modulation page will change to reflect the new system mode and will show the settings as shown in the following figure.



Fig. 3-13 Advanced mode modulation tab


The Modulation tab provides the same properties for number of frames and oversampling mode as in Basic Mode modulation.

Creating a Frame

To create an advanced frame, click on the Frame Config tab. This will present the screen shown in the following figure, which will allow you to configure the frame.



Fig. 3-14 showing an advanced GSM Frame


The following Channel types are supported per slot.

  1. BCCH: Slot-0 is set as BCCH carrier and carries all the information required for synchronization with the DUT in non-signaling mode of operation.
  2. TCH/SACCH: This channel type can be set for slot-1 to slot-7. All the slots carry channel coded user data for transmission. When this channel type is selected for a slot, the user can further configure the mode of operation as speech or data.
  3. PDTCH: This channel type can be set for slot-1 to slot-7. This channel type allows the user to transmit PDTCH data. When this channel type is selected, the user can configure the RLC/MAC Header based on the Modulation and Coding scheme.

The Channel type can be set by selecting the appropriate value in Channel Type box for the slot under configuration.

By default, the parameters for BCCH will be displayed, allowing you to configure both the Base Color Code, and the Network Color code. The First slot within the frame is fixed to BCCH and cannot be changed. However, any of the other slots may be edited by clicking on the slot graphic at the top of the screen. The following figure shows the screen that is presented when the second slot, in the above case a TCH-SACCH slot.



Fig. 3-15 showing the TCH-SACCH slot configuration


The type of Channel that is present on the given slot can be modified using the Channel Type control at the top of the edit panel below the main slot graphic. By default, all configurable channels will be set to the TCH/SACCH mode. However, the following slot types are available: TCH/SACCH, PDTCH, and Dummy.

Configuring a TCH/SACCH Slot

The controls below the main slot graphic allow you to change the configuration for the TCH/SACCH Slot, and are as follows.

Channel Bits

This property is only applicable for TCH/SACCH channel type. The Channel Bits control defines whether speech data or circuit-switched data shall be transmitted on TCH.

When the Channel Type is set to TCH/SACCH, the number of Data Source can be 1 or 2 depending on Data Mode selected as listed in the following table:



Table 3-4 Data Sources for TCH/SACCH channel


The Data Mode can be set by selecting the appropriate value in Data Mode box. By default, the Data Mode is set to Speech.

PCL

This field is enabled only if TCH/SACCH Channel Type is selected for transmission. The Power Control Level is 5 bit field in the SACCH message. This means that a value ranging from 0 (High Power) to 31 (Low Power) can be set.

The PCL commands the power level to be used by the mobile station.

Training Sequence

This is the standard training sequence. The training sequence is used as a timing reference and for equalisation. There are total of eight different bit sequences that may be used, each 26 symbols long.

TSC0 to TSC7 can be selected and applies to the whole slot under configuration. The default is TS0

FPC

This field is only enabled if TCH/SACCH Channel Type is selected for transmission. The Fast Power Control is a 1 bit field in the SACCH message.

The PCL field indicates whether fast measurement reporting and power control mechanism is used. If the FPC checkbox is unselected, FPC bit is set to 0 in SACCH message; this indicates FPC is not in use.

By default, the FPC checkbox is selected which results in FPC bit set to 1 in SACCH message. By default the checkbox is selected.

Class Bits

This controls the data payload of the class bits. When the Channel Bits type is set to Speech, two buttons are displayed for Class 1 Bits and for Class 2 bits. When the Channel Bits type is set to Loop C, there will be a single data payload button representing the data to be transmitted on this channel.

Configuring a PDTCH Slot

The channel organization for packet data channels uses the 52-frame multiframe. Four TDMA slots constitute a radio block. It is basically a sequence of four normal bursts carrying one RLC/MAC protocol data units.

The figure below shows the constitution of radio blocks in 52-frame multiframe.



Fig. 3-16: PDTCH Radio blocks


For PDTCH, the data is not coded before mapping to the bursts. The data source configured for generation terminates every radio block and restarts. This allows the data to wrap around if a multiple of 52 frames is used.

When the Channel type of a given slot is changed to PDTCH; the main configuration area will changed to that shown in the following figure.



Fig. 3-17 showing the PDTCH configuration


This channel type will present similar controls to that described in the TCH/SACCH channel configuration above, but will also provide additional controls for MCS and MAC Header

MCS

GSM/EDGE Modulation supports GPRS and EGPRS DL Modulation and Coding Schemes.

Four different coding schemes, CS-1 to CS-4, are defined for the GPRS Radio Blocks carrying RLC data blocks.



Table 3-5 Supported Modulation and Coding Schemes


The modulation and coding scheme can be set by selecting the appropriate value in the MCS box. The selected value of MCS will changes the configuration of the MAC Header.

RLC/MAC block

A RLC/MAC block is the protocol data unit exchanged between RLC/MAC entities.



Fig. 3-18: RLC/MAC Block


A RLC/MAC header block is the part of an RLC/MAC block carrying a control message between RLC/MAC entities.

A RLC data block is the part of a RLC/MAC block carrying user data or signalling data received from an upper layer.

RLC/MAC Header Include

This field sets whether the RLC/MAC header shall be included and coded for transmission.

There are only certain valid combinations of RLC/MAC Header and Data Encoding that are allowed by advanced mode of GSM/EDGE Modulation. These are shown in the following table.



Table 3-6 Valid combinations for RLC/MAC Header Include field and Data Encoding field


The RLC/MAC header inclusion can be set by selecting the appropriate value in the RLC/MAC Header Include checkbox.

Data Encoding

This field sets whether the Data shall be coded for transmission.

There are only certain valid combinations of RLC/MAC Header and Data Encoding that are allowed by advanced mode of GSM/EDGE Modulation. These are shown in the above table.

The data encoding can be set by setting the appropriate value in the Data encoding checkbox.

RLC/MAC Header

RLC/Mac header contains control information of the RLC/MAC block. Depending upon the MCS selected, an applicable RLC/MAC header is displayed. You are able to configure the parameters of RLC/MAC header. The format of RLC/MAC headers for various MCS, are as follows:

For MCS-1, MCS-2, MCS-3, and MCS-4, Header type 3 as per 3GPP TS 44.060 is used. Total header size is 31 bits.



Table 3-7 Header Type 3 (MCS-1, MCS-2, MCS-3 and MCS-4)


For MCS-5 and MCS-6, Header type 2 as per 3GPP TS 44.060 is used. Total header size is 28 bits.



Table 3-8 Header Type 2 (MCS-5 and MCS-6)


For MCS-7, MCS-8 and MCS-9, Header type 1 per 3GPP TS 44.060 is used. Total header size is 40 bits.



Table 3-9 Header Type 1 (MCS-5 and MCS-6)


For CS-1 to CS-4, only USF bits are applicable.



Table 3-10 USF Bits


The Advanced mode of GSM/EDGE generation modulation does not implement all the RLC/MAC Header related functionality except for CPS field which affects the way the coding and puncturing scheme used for the RLC/MAC data block in case the data encoding is set. It allows the user to set the values within the valid range.

All the RLC/MAC Header fields can be set by clicking on each bit in the MAC Header field. The RLC/MAC Header settings are constant across all the RLC/MAC Header data blocks for a configured slot.

Uplink State Flag (USF) Field

The USF field is sent in all downlink RLC/MAC blocks and indicates the owner or use of the next uplink radio block on the same timeslot (3GPP TS 45.002). The USF field is three bits in length and eight different USF values can be assigned.

EGPRS Supplementary/Polling (ES/P) Field

The ES/P field is used to indicate whether the RRBP field is valid or not valid, and what fields the next uplink control block shall contain.

Refer to 3GPP TS 44.060 for more information.

Relative Reserved Block Period (RRBP) Field

The RRBP value specifies a single uplink block in which the mobile station shall transmit either a PACKET CONTROL ACKNOWLEDGEMENT message or a PACCH block to the network.

Refer to 3GPP TS 44.060 for more information.

Temporary Flow Identity (TFI) Field

The TFI identifies the Temporary Block Flow (TBF) to which the RLC data block belongs. It is 5 bits in length.

Refer to 3GPP TS 44.060 for more information.

Power Reduction (PR) field

The Power Reduction (PR) field indicates the power level reduction of the current RLC block. If downlink power control is not used, the MS ignores the PR field.



Table 3-11 PR Field


Block Sequence Number (BSN) field

The Block Sequence Number (BSN) field carries the sequence absolute Block Sequence Number (BSN') modulo Sequence Number Space (SNS) (2 048 in EGPRS) of each RLC data block within the TBF. In EGPRS, the BSN is 11 bits in length and is encoded as a binary number with range 0 to 2 047.

If two to four RLC data blocks are sent within a RLC/MAC block, BSN2 to BSN4 are relative to BSN1, provided the difference between the second to fourth block number and the first block modulo SNS is less than Window Size (WS).

Refer to 3GPP TS 44.060 for more information.

Coding and Puncturing Scheme Indicator Field (CPS)

The Coding and Puncturing Scheme indicator field indicates the kind of channel coding and puncturing used for data blocks.

Refer to the following tables for possible CPS field values.

Refer to 3GPP TS 44.060 for more information.



Table 3-12 Header Type 1 CPS bit fields




Table 3-13 Header Type 2 CPS bit fields




Table 3-14 Header Type 3 CPS bit fields


Split Block Indicator Field (SPB)

The Split Block indicator is only used in header type 3 to indicate if some user data is retransmitted using 2 block re-segmentation

Refer to 3GPP TS 44.060 for more information.

MAC Header Configuration

The MAC Header box allows you to modify the individual portions of the header transmitted as part of the PDTCH channel.

You can either modify individual bits by clicking on the particular box you wish to toggle.



Fig. 3-19 showing toggling a bit within the MAC Header


Alternatively, you can edit the values by clicking on the particular field you wish to edit and typing either 1 or 0; this will fill the field from right to left with the bits you type. Please note that the values you type will not carry over from one field to the next.

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