lteSRS
Uplink sounding reference signal
Description
returns
a complex matrix, seq
= lteSRS(ue
,chs
)seq
, containing uplink sounding
reference signal (SRS) values and information structure array given
structures containing UE-specific settings, and signal transmission
configuration settings. For more information, see SRS Processing and TS 36.213 [1], Section 8.2.
Examples
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 = 4×1 complex
0.7071 - 0.7071i
-0.7071 + 0.7071i
0.7071 + 0.7071i
-0.7071 - 0.7071i
Generate SRS Symbols for Two Antennas
Generate the SRS symbols for two transmit antenna paths. Display the information structure.
Initialize UE-specific and channel configuration structures (ue
and chs
) for 3 MHz bandwidth and two antennas using the default SRS configuration. Generate SRS symbols and the information structure (ind
and info
).
ue.DuplexMode = 'FDD'; ue.CyclicPrefixUL = 'Normal'; ue.NFrame = 0; ue.NULRB = 15; ue.NSubframe = 0; chs = struct(); chs.NTxAnts = 2; chs.BWConfig = 7; chs.BW = 0; chs.CyclicShift = 0; chs.ConfigIdx = 7; chs.SeqIdx = 0; chs.SeqGroup = 0; [ind,info] = lteSRS(ue,chs);
Since there are two antennas, the SRS symbols are output as a two column vector and the info
output structure contains two elements.
ind(1:6,:)
ans = 6×2 complex
0.5000 - 0.5000i 0.5000 - 0.5000i
-0.5000 + 0.5000i 0.5000 - 0.5000i
0.5000 + 0.5000i 0.5000 + 0.5000i
-0.5000 - 0.5000i 0.5000 + 0.5000i
-0.5000 + 0.5000i -0.5000 + 0.5000i
0.5000 - 0.5000i -0.5000 + 0.5000i
size(info)
ans = 1×2
1 2
View the contents of the two info
structure elements.
info(1)
ans = struct with fields:
Alpha: 0
SeqGroup: 0
SeqIdx: 0
RootSeq: -1
NZC: -1
info(2)
ans = struct with fields:
Alpha: 3.1416
SeqGroup: 0
SeqIdx: 0
RootSeq: -1
NZC: -1
Input Arguments
ue
— UE-specific settings
structure
UE-specific settings, specified as a structure containing these following fields.
NULRB
— Number of uplink resource blocks
positive integer
Number of uplink resource blocks, specified as a positive integer.
Data Types: double
NSubframe
— Subframe number
0 (default) | optional | nonnegative integer
Subframe number, specified as a nonnegative integer.
Data Types: double
NTxAnts
— Number of transmission antennas
1 (default) | optional | 2 | 4
Number of transmission antennas, specified as 1, 2, or 4.
Data Types: double
CyclicPrefixUL
— Cyclic prefix length for uplink
'Normal'
(default) | optional | 'Extended'
Cyclic prefix length for uplink, specified as 'Normal'
or 'Extended'
.
Data Types: char
| string
NFrame
— Initial frame number
0 (default) | optional | nonnegative integer
Initial frame number, specified as a nonnegative integer.
Data Types: double
DuplexMode
— Duplexing mode
'FDD'
(default) | optional | 'TDD'
Duplexing mode, specified as 'FDD'
or 'TDD'
to
indicate the frame structure type of the generated waveform.
Example: 'TDD'
Data Types: char
| string
TDDConfig
— Uplink or downlink configuration
0 (default) | integer from 0 to 6 | optional
Uplink or downlink configuration, specified as an integer from
0 to 6. Only required for TDD
duplex mode.
Data Types: double
SSC
— Special subframe configuration
0 (default) | integer from 0 to 9 | optional
Special subframe configuration, specified as an integer from
0 to 9. 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 'Normal'
or 'Extended'
.
Data Types: char
| string
Data Types: struct
chs
— Signal transmission configuration
structure
Signal transmission configuration, specified as a structure containing these fields.
NTxAnts
— Number of transmission antennas
1 (default) | optional | 2 | 4
Number of transmission antennas, specified as 1, 2, or 4.
Data Types: double
BWConfig
— SRS bandwidth configuration
7 (default) | integer from 0 to 7 | optional
SRS bandwidth configuration, specified as an integer from 0 to 7. (CSRS)
Data Types: double
BW
— UE-specific SRS bandwidth
0 (default) | optional | 1 | 2 | 3
UE-specific SRS bandwidth, specified as an integer from 0 to 3. (BSRS)
Data Types: double
ConfigIdx
— Configuration index for UE-specific periodicity
7 (default) | integer from 0 to 644 | optional
Configuration index for UE-specific periodicity, specified as a nonnegative integer from 0 to 644. This parameter contains the configuration index for UE-specific periodicity (TSRS) and subframe offset (Toffset).
Data Types: double
CyclicShift
— UE-specific cyclic shift
0 (default) | integer from 0 to 7 | optional
UE-specific cyclic shift, specified as an integer from 0 to 7. ()
Data Types: double
SeqGroup
— SRS sequence group number
0 (default) | integer from 0 to 29 | optional
SRS sequence group number, specified as an integer from 0 to 29. (u)
Data Types: double
SeqIdx
— Base sequence number
0 (default) | optional | 1
Base sequence number, specified as either 0 or 1. (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. 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
seq
— Uplink SRS values
complex matrix
Uplink SRS values, returned as a complex matrix. The symbols for each antenna are in the
columns of the matrix, seq
. The symbols for each
antenna are in the columns of seq
, with the number of
columns determined by the number of transmission antennas configured. For
more information, see SRS Processing.
Data Types: double
Complex Number Support: Yes
info
— Information related to SRS
structure
Information related to SRS, returned as a structure array with elements corresponding to each transmit antenna and containing these fields.
Alpha
— Reference signal cyclic shift
numeric scalar
Reference signal cyclic shift, returned as a numeric scalar. (α)
Data Types: double
SeqGroup
— SRS sequence group number
0,...,29
SRS sequence group number, returned as an integer from 0 to 29. (u)
Data Types: double
SeqIdx
— Base sequence number
0 | 1
Base sequence number, returned as 0 or 1. (v)
Data Types: double
RootSeq
— Root Zadoff-Chu sequence index
integer
Root Zadoff-Chu sequence index, returned as an integer. (q)
Data Types: double
NZC
— Zadoff-Chu sequence length
integer
Zadoff-Chu sequence length, returned as an integer. ()
Data Types: double
Data Types: struct
More About
SRS Processing
As specified in TS 36.213, Section 8.2, a UE shall transmit the sounding reference symbol (SRS) on per serving cell SRS resources, based on two trigger types:
trigger type 0 — periodic SRS from higher layer signalling
trigger type 1 — aperiodic SRS from DCI formats 0/4/1A for FDD or TDD and from DCI formats 2B/2C/2D for TDD.
The parameter chs
.
ConfigIdx
indexes Tables 8.2-1, 8.2-2, 8.2-4, and 8.2-5 defined in TS 36.213, Section 8.2. The
applicable table and appropriate range of chs.ConfigIdx
depends on the
duplex mode and the SRS trigger type.
If type 0 triggered SRS transmission is intended, then:
The valid range of
chs.ConfigIdx
(ISRS) is from 0 to 636 for FDD (Table 8.2-1) and from 0 to 644 for TDD (Table 8.2-2).
If type 1 triggered SRS transmission is intended, then:
chs.ConfigIdx
indexes trigger type 1 UE-specific periodicity TSRS,1 and subframe offset Toffset,1. The valid range ofchs.ConfigIdx
(ISRS) is from 0 to 16 for FDD (Table 8.2-4) and from 0 to 24 for TDD (Table 8.2-5).Frequency hopping is not permitted. Therefore, set
chs.HoppingBW
to be greater than or equal toBW
. (bhop ≥ BSRS).
To control whether to call the lteSRS
and
lteSRSIndices
functions in a subframe, use
info.IsSRSSubframe
, returned by lteSRSInfo
.
UE-specific configurations determine how lteSRS
and lteSRSIndices
operate.
When no SRS is scheduled, calling lteSRS
or lteSRSIndices
in
a subframe:
May generate an SRS depending on the cell-specific SRS subframe configuration.
Returns an empty
seq
orind
vector, for a given UE-specific SRS configuration. Also, theinfo
structure scalar fields are set to –1, and any undefined vector fields are empty.
For short-base reference sequences, used with SRS transmissions
spanning 4 PRBs, the lteSRS
function does not
use Zadoff Chu sequences and it sets info
.
RootSeq
and info
.
NZC
to
–1.
lteSRSIndices
returns the UE-specific SRS
periodicity, info
.
UePeriod
,
and subframe offset, info
.
UeOffset
.
These parameters are distinct from the cell-specific SRS periodicity
and subframe offset that lteSRSInfo
returns.
If chs
.
NTxAnts
is
not present, ue
.
NTxAnts
is
used. If neither is present, the function assumes one antenna. In lteSRSIndices
,
for SRS transmission on multiple antennas:
When
chs
.
NTxAnts
is set to 2 or 4, the value ofinfo
.
Port
matches the position in the structure array (0,...,NTxAnts
– 1).If
chs
.
NTxAnts
is set to 1,lteSRSIndices
usesinfo
.
Port
to indicate the port chosen by SRS transmit antenna selection.info
.
Port
indicates the selected antenna port, 0 or 1.
References
[1] 3GPP TS 36.213. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.
Version History
Introduced in R2014a
See Also
lteSRSIndices
| lteSRSInfo
| lteCellRS
| lteCSIRS
| lteDMRS
| ltePRS
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