Mobile Calculated BER Test

Clearcoded payload on TCH

During Mobile Calculated BER test, the test set generates a downlink TCH at a known level with data using the clearcoded pattern you specify. Clearcoded speech is transmitted on full rate (including enhanced full rate) TCH channel and the speech source is PRBS9, PRB15 or Custom. Through the following two diagrams, you can differentiate the Clearcoded payload transmission and a normal transmission on a full rate TCH channel.

Channel coding and interleaving for full rate TCH

Channel coding and interleaving for full rate TCH

Figure 1 illustrates how channel coding and interleaving is applied at full rate on TCH channel. GSM uses a voice coder to generate 260-bit voice frame on TCH channel. The 260-bit are added with error-correction bits in GSM codec which acts as a channel coder. As a result, the 456 bits of speech data are sliced up into 8 blocks of 57-bit for each of them. Each TCH frame carries two 57-bit blocks of data from two different 456-bit speech segments. The remaining 2 bits are used for stealing bits (SB). Figure 2 illustrate an example how ClearCoded payload bits are directly filled onto TCH bursts. The two 57-bit fields are filled with information bits without channel coding and interleaving. The training sequence bits, tail bits and guard bits are not shown. The following table lists the difference between normal transmission over full rate TCH channel and ClearCoded payload over full rate TCH channel.

ClearCoded payload on EGPRS PDTCH

During Mobile Calculated BER test, the test set generate a downlink EGPRS PDTCH at a known level with data using the clearcoded pattern you specify. (See Payload Patterns ). The ClearCoded information bits are directly applied to the specific bit positions which are determined by the modulation and coding scheme selected.

• MCS 1-4

  Since the USF, header and data are interleaved together in MCS1-4, it is impossible to delimit the field for data bit, USF and header when they are interleaved together. Hence, 114 raw data bits sourced from the data generator are directly applied to the burst bits [0,56] and[59,115].

  • e(B, j) and e(B,59+j) = i(B,57+j) for j=0,1,...,56
  • e(B, 57) = hl(B) and e(B,58) = hu(B)

  The two bits labeled hl(B) and hu(B) on burst number B are flags used for indication of control signaling.

• MCS 5/6

  In MSC5 and MCS6, 312 data bits are available in each burst for ClearCoded payload bits. The remaining 36 bits are used for USF, header and SB which is coding scheme identification. The mapping is

  • e(B, j) = di (312B+j) for j=0,1,...,155
  • e(B, j) = di (312B+j-36) for j=192,193,...,347

  Where B represents the burst number, di(k) are the ClearCoded payload bits. The ClearCoded payload is applied directly to bits [0,155] and [192,347] of the burst. The bit swapping and channel coding is not performed. But for the filed of SB, USF and header, the channel coding and interleaving is still needed.

  The following diagram illustrates the e(B,j) bits for burst number B. The test set applies the 312 ClearCoded payload bits to the 2 block of 156 data bits. The next burst contains the next 312 bits of the ClearCoded payload sources, and so on.

  Channel coding and interleaving for full rate TCH

  
• MSC 7/8/9

  MCS 7/8/9 is nearly identical to MCS 5/6, only 306 data bits are available per burst for ClearCoded payload. The mapping and diagram below illustrate this.

  • e(B, j) = di (306B+j) for j=0,1,...,152
  • e(B, j) = di (306B+j-42) for j=195,193,...,347

  Where B represents the burst number, di(k) are the ClearCoded payload bits. But for the field of SB, USF and header, the channel coding and interleaving are still needed.

  Channel coding and interleaving for full rate TCH

  

  The test box applies the 312 source ClearCoded payload bits to the 2 blocks of 156 data bits. The next burst contains the next 312 bits of the ClearCoded payload sources and so on.

ClearCoded payload vs. 8PSK ClearCoded

ClearCoded payload is different from the existing 8PSK ClearCoded. 8 PSK ClearCoded is only applicable for 8PSK bursts. When 8PSK ClearCoded is applied, the ClearCoded payload bits are applied to the whole 348 bits per burst including the fields for stealing bits(SB), USF, header and data in normal data transmission. But the ClearCoded payload is applicable for both GMSK and 8PSK bursts. When ClearCoded payload for 8PSK bursts with a selected modulation and coding scheme (MCS) from MCS1 to MCS9, only data field is filled with ClearCoded payload, the other fields such as SB, USF and header are still filled with encoded data. However, only if 8PSK ClearCoded is enabled, the ClearCoded payload is applied to the whole bits of a burst regardless of whether ClearCoded payload is enabled.

TCH ClearCoded State

This parameter allows you to enable ClearCoded speech on TCH. This parameter only affects the test set's operation when the operating mode is set to GSM BCH+TCH, the channel mode for TCH is set to FR Speech or EFR Speech and the TCH speech source is set to PRBS 9, PRBS 15 or Custom. This parameter is not available in GPRS BCH+PDTCH+TCH. This is because the header and data of a RLC/MAC block are interleaved and clearcoded payload become impossible.

The GPIB command to set this parameter is CALL:TCHannel:CLEarcoded:STATe .

Multi Source Payload Pattern for downlink Burst [n]

This parameter allows you to set the payload pattern for each of the downlink burst which is configured independently. This parameter only affects the test set's operation when the operating mode is set to EGPRS BCH+PDTCH test mode and when EGPRS Test Mode Payload Mapping is Multi Source, ClearCoded. See Payload Patterns for more information.

The GPIB command to set this parameter is CALL:FUNCtion:DATA:PAYLoad:PATTern[:OTHer]:MSOurce:BURSt<n> .

EGPRS Test Mode Payload Mapping

This parameter allows you to enable the ClearCoded payload and set the payload mapping scheme. One of the following is selected as the payload mapping scheme used for EGPRS BCH+PDTCH test mode.

• Single Source, Normal: ClearCoded payload is disabled and the payload from the same data source spreads over all the downlink PDTCH channels. The modulation and coding scheme is determined by MCS/PS setting.
• Single Source, ClearCoded: ClearCoded payload is enabled and the payload from the same data source spreads over all the downlink PDTCH channels. The payload is directly applied to the bursts of PDTCH channel without channel coding and interleaving. If "8PSK Clearcoded" is selected in MCS/PS setting, the payload spreads over the whole burst including the headers, SB and USF fields. Otherwise, they are coded an interleaved only when the payload is Clearcoded.
• Multi Source, ClearCoded: ClearCoded payload is enabled and the payload for each of the downlink PDTCH channels is independently generated. The payload is directly applied to the bursts of PDTCH channel without channel coding and interleaving. If "8PSK Clearcoded" is selected in MCS/PS setting, the payload is filled into the whole burst including the headers, SB and USF fields. Otherwise, they are coded an interleaved only when the payload is Clearcoded.

The GPIB command to set this parameter is CALL:(PDTCH|PDTChannel):EGPRS:MAPPing .

TCH Speech Source

This parameter allows you to set the speech data configuration that is transmitted on the downlink TCH. This is a TCH parameter, see Speech for more information.

The GPIB command to set this parameter is CALL:TCHannel:DOWNlink:SPEech .

PDTCH Payload Pattern (Other)

This parameter allows you to set the type of downlink payload pattern to be used when the test set's operating mode is set to a valid connection type. This is a Logical Link Control (LLC) Layer parameter, see Payload Patterns for more information.

The GPIB command to set this parameter is CALL:FUNCtion:DATA:PAYLoad:PATTern[:OTHer] .

PDTCH Payload Pattern BLER

This parameter allows you to set the type of downlink payload pattern to be used when the test set's operating mode is set to BLER in Active Cell operating mode, and the LLC Frame Check Sequence parameter is set to CORRupt . This is a Logical Link Control (LLC) Layer parameter, see Payload Patterns for more information.

The GPIB command to set this parameter is CALL:FUNCtion:DATA:PAYLoad:PATTern:BLER .