Documentation

lteSRS

Uplink sounding reference signal

Syntax

  • [seq,info] = lteSRS(ue,chs)
    example

Description

example

[seq,info] = lteSRS(ue,chs) returns a complex matrix, seq, containing Uplink sounding reference signal (SRS) values and information structure array, info. The function returns these values for UE-specific settings, ue, and signal transmission configuration, chs. The symbols for each antenna are in the columns of seq, with the number of columns determined by the number of transmission antennas configured.

Type 1 triggered SRS transmission corresponds with aperiodic SRS triggered by DCI formats 0/4/1A for FDD or 0/4/1A/2B/2C for TDD. For this case, the parameter chs.ConfigIdx indexes trigger type 1 UE-specific periodicity T_SRS,1, and subframe offset, T_offset,1. Also, the valid range of chs.ConfigIdx (I_SRS) is from 0 through 16 for FDD and from 0 through 24 for TDD.

If the NTxAnts parameter field is present in the chs structure, the function uses its value for the number of transmission antennas. Otherwise, the function uses the value of the same parameter field in the ue structure instead.

For short base reference sequences, used with SRS transmissions spanning 4 PRBs, Zadoff-Chu sequences are not used. In this case, RootSeq and NZC are set to –1. For cases where the seq output is empty, as is the case when the SRS is not scheduled for transmission in the subframe, the info structure contains all fields, but each field is set to –1.

    Note:   UE-specific configurations as defined in TS 36.213 [1], Section 8.2 determine the operation of lteSRS. lteSRS may generate an SRS signal even in a subframe that, based on cell-specific SRS subframe configuration, is not an SRS subframe. lteSRS returns an empty vector if no SRS is scheduled for a given UE-specific configuration.

    Use the field info.IsSRSSubframe returned by lteSRSInfo to control whether to call lteSRS in a subframe.

Examples

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Generate Uplink SRS Values

This example generates SRS values for 1.4 MHz bandwidth using the default SRS configuration.

Set the signal transmission configuration, chs structure fields.

chs.BWConfig = 7;
chs.BW = 0;
chs.CyclicShift = 0;
chs.SeqGroup = 0;
chs.SeqIdx = 0;
chs.ConfigIdx = 7;

Set ue structure fields.

ue.DuplexMode = 'FDD';
ue.CyclicPrefixUL = 'Normal';
ue.NTxAnts = 1;
ue.NFrame = 0;
ue.NULRB = 6;
ue.NSubframe = 0;

Generate Uplink SRS resource element values.

srs = lteSRS(ue,chs);
srs(1:4)
ans =

   0.7071 - 0.7071i
  -0.7071 + 0.7071i
   0.7071 + 0.7071i
  -0.7071 - 0.7071i

Input Arguments

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ue — UE-specific settingsstructure

UE-specific settings, specified as a structure. The structure contains the following fields.

NULRB — Number of uplink resource blockspositive scalar integer

Number of uplink resource blocks, specified as a positive scalar integer.

Data Types: double

NSubframe — Subframe number0 (default) | optional | scalar integer

Subframe number, specified as a scalar integer. Optional.

Data Types: double

NTxAnts — Number of transmission antennas1 (default) | optional | 2 | 4

Number of transmission antennas, specified as 1, 2, or 4. Optional.

Data Types: double

CyclicPrefixUL — Cyclic prefix length for uplink'Normal' (default) | optional | 'Extended'

Cyclic prefix length for uplink, specified as a string. Optional.

Data Types: char

NFrame — Initial frame number0 (default) | optional | numeric scalar

Initial frame number, specified as a numeric scalar. Optional.

Data Types: double

DuplexMode — Duplexing mode'FDD' (default) | optional | 'TDD'

Duplexing mode, specified as a string. Optional. This string represents the frame structure type of the generated waveform.

Example: 'TDD'

Data Types: char

TDDConfig — Uplink or downlink configuration0 (default) | optional | (0...6)

Uplink or downlink configuration, specified as a nonnegative scalar integer from 0 through 6. Optional. Only required for TDD duplex mode.

Data Types: double

SSC — Special subframe configuration0 (default) | optional | (0...9)

Special subframe configuration, specified as a nonnegative scalar integer from 0 through 9. Optional. Only required for TDD duplex mode.

Data Types: double

CyclicPrefix — Cyclic prefix length in the downlink'Normal' (default) | optional | 'Extended'

Cyclic prefix length in the downlink, specified as a string. Optional.

Data Types: char

Data Types: struct

chs — Signal transmission configurationstructure

Signal transmission configuration, specified as a structure. The structure contains these fields.

NTxAnts — Number of transmission antennas1 (default) | optional | 2 | 4

Number of transmission antennas, specified as 1, 2, or 4. Optional.

Data Types: double

BWConfig — SRS bandwidth configuration7 (default) | optional | 0...7

SRS bandwidth configuration, specified as a nonnegative scalar integer from 0 through 7. Optional. The default is 7. (C_SRS)

Data Types: double

BW — UE-specific SRS bandwidth0 (default) | optional | 0...3

UE-specific SRS bandwidth, specified as a nonnegative scalar integer from 0 through 3. Optional. The default is 0. (B_SRS)

Data Types: double

ConfigIdx — Configuration index for UE-specific periodicity7 (default) | optional | 0...644

Configuration index for UE-specific periodicity, specified as a nonnegative scalar integer from 0 through 644. Optional. This parameter contains the configuration index for UE-specific periodicity (T_SRS) and subframe offset (T_offset).

Data Types: double

CyclicShift — UE-specific cyclic shift0 (default) | optional | 0...7

UE-specific cyclic shift, specified as a nonnegative scalar integer from 0 through 7. Optional. The default is 0. (n_SRS^cs)

Data Types: double

SeqGroup — SRS sequence group number0 (default) | optional | 0...29

SRS sequence group number, specified as a nonnegative scalar integer from 0 through 29. Optional. (u)

Data Types: double

SeqIdx — Base sequence number0 (default) | optional | 1

Base sequence number, specified as either 0 or 1. Optional. (v)

Data Types: double | logical

OffsetIdx — SRS subframe offset 0 (default) | optional | 1

SRS subframe offset choice for 2 ms SRS periodicity, specified as 0 or 1. Optional. Only required for 'TDD' duplex mode. This parameter indexes the two SRS subframe offset entries in the row of TS 36.213 [1], Table 8.2-2 for the SRS configuration index specified by the ConfigIdx parameter.

Data Types: double

Data Types: struct

Output Arguments

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seq — Uplink SRS valuescomplex matrix

Uplink SRS values, returned as a complex matrix. The symbols for each antenna are in the columns of the matrix, seq. The number of transmission antennas configured determines the number of columns.

Data Types: double
Complex Number Support: Yes

info — Information related to SRSstructure

Information related to SRS, returned as a structure. The structure contains the following fields.

Alpha — Reference signal cyclic shiftnumeric scalar

Reference signal cyclic shift, returned as a numeric scalar. (alpha)

Data Types: double

SeqGroup — SRS sequence group number(0...29)

SRS sequence group number, returned as a nonnegative scalar integer from 0 through 29. (u)

Data Types: double

SeqIdx — Base sequence number0 | 1

Base sequence number, returned as 0 or 1. (v)

Data Types: double

RootSeq — Root Zadoff-Chu sequence indexnumeric scalar

Root Zadoff-Chu sequence index, returned as numeric scalar. (q)

Data Types: double

NZC — Zadoff-Chu sequence lengthnumeric scalar

Zadoff-Chu sequence length, returned as a numeric scalar. (NRS_ZC)

Data Types: double

Data Types: struct

References

[1] 3GPP TS 36.213. "Physical layer procedures." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: http://www.3gpp.org.

Introduced in R2014a

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