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Add documentation on TDD configuration

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Co-authored-by: Robert Schmidt <robert.schmidt@openairinterface.org>
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vijay chadachan
2024-10-09 15:49:44 +02:00
committed by Guido Casati
parent ca72b56c2c
commit fc6e205c89
3 changed files with 115 additions and 1 deletions
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doc/FEATURE_SET.md
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@@ -24,7 +24,9 @@
The following features are valid for the gNB and the 5G-NR UE.
* Static TDD, FDD
* Static TDD
- Multi TDD pattern supported refer [TDD Configuration](NR_SA_Multi_TDD_Pattern.md)
* Static FDD
* Normal CP
* Subcarrier spacings: 15 and 30kHz (FR1), 120kHz (FR2)
* Bandwidths: 10, 20, 40, 60, 80, 100MHz

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doc/MAC/mac-usage.md
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@@ -240,3 +240,115 @@ here, *also they pertain to the DU*, i.e., the scheduler.
options are 2, 4, 6, 8, 10, 12, 32; **32 is a Rel-17 features**)
* `num_ulharq` (default 16): as `num_dlharq` for UL (other valid option is 32;
**32 is i Rel-17 feature**)
## ServingCellConfigCommon parameters
The `gNBs` configuration section has a big structure `servingCellConfigCommon`
that has an influence on the overall behavior of MAC and L1. As the name says,
this structure is a flat representation of the ServingCellConfigCommon
structure, specified by 3GPP. Describing all of these parameters would be too
exhaustive; more information about the individual fields can be found in 3GPP
TS 38.331, section 6.3.2 "Radio resource control information elements".
Below is a description of some of these parameters.
### Frequency configuration
There are many parameters, such as `absoluteFrequencySSB`, etc., that have an
impact on the frequency used by the gNB. For more information, please check the
[corresponding document](../gNB_frequency_setup.md).
### TDD pattern configuration
The TDD configuration parameters allow to use one or two TDD patterns.
#### Single TDD pattern
Configure the TDD pattern through these options:
- `dl_UL_TransmissionPeriodicity`: Refers to the UL/DL slots periodicity for
the TDD pattern. See below for valid numbers.
- `nrofDownlinkSlots`: Refers to the number of consecutive DL slots in the TDD
pattern. The number of DL slots depends on the TDD period.
- `nrofDownlinkSymbols`: Indicates the number of consecutive DL symbols within
the special slot that follows the downlink slots in the TDD pattern. The
special slot is needed only to switch from DL to UL. The maximum number of
symbols in this slot is 14.
- `nrofUplinkSlots`: Refers to the number of consecutive UL slots in the TDD
pattern, depending on the desired TDD period.
- `nrofUplinkSymbols`: Indicates the number of consecutive UL symbols within
the special slot that follows the downlink slots in the TDD pattern. The sum
of downlink and uplink symbols should not exceed 14.
- `prach_ConfigurationIndex`: index for PRACH according to tables 6.3.3.2-2 to
6.3.3.2-4 in TS 38.211.
As an example, the below figure shows a single TDD pattern, consisting of 3 DL
slots, 1 mixed slots (with 10 DL, 2 guard, 2 UL symbols), and 1 UL slot.
![TDD Frame Structure](TDD_Frame_Structure.png)
To configure this pattern in the configuration file, use
```plaintext
#dl_UL_TransmissionPeriodicity 0=ms0p5, 1=ms0p625, 2=ms1, 3=ms1p25, 4=ms2, 5=ms2p5, 6=ms5, 7=ms10, 8=ms3, 9=ms4
dl_UL_TransmissionPeriodicity = 5;
nrofDownlinkSlots = 3;
nrofDownlinkSymbols = 10;
nrofUplinkSlots = 1;
nrofUplinkSymbols = 2;
```
The `dl_UL_TransmissionPeriodicity` is set to `5` (2.5ms). The above figure
shows two TDD periods over 5ms. The 10 ms frame period must be strictly
divisible by the sum of the TDD pattern periods.
#### Two TDD patterns
An optional `pattern2` structure is used to signal a TDD pattern 2.
In this case, the TDD pattern may have two extended values of 3 ms and 4 ms.
These values are standardized as `dl-UL-TransmissionPeriodicity-v1530`. For the
sake of simplicity of the gNB configuration file, we have extended the set of
`dl-UL-TransmissionPeriodicity` values to support the new TDD periods, as
explained in the table below. However, these values will later be encoded as
`dl-UL-TransmissionPeriodicity-v1530` to match the specifications.
| `dl_UL_TransmissionPeriodicity` | TDD period |
|---------------------------------|------------|
| 0 | 0.5 ms |
| 1 | 0.625 ms |
| 2 | 1 ms |
| 3 | 1.25 ms |
| 4 | 2 ms |
| 5 | 2.5 ms |
| 6 | 5 ms |
| 7 | 10 ms |
| 8 | 3 ms |
| 9 | 4 ms |
The 10 ms frame period must be strictly divisible by the sum of the TDD pattern
periods. For example, the 3 ms TDD pattern should be used with a second TDD
pattern of 2 ms. Additionally, the 4 ms TDD pattern should be used with a
second TDD pattern of 1 ms.
As an example, this configuration might be used, where the first TDD pattern is
followed by a second, consisting of 4 DL slots.
```
# pattern1
# dl_UL_TransmissionPeriodicity
# 0=ms0p5, 1=ms0p625, 2=ms1, 3=ms1p25, 4=ms2, 5=ms2p5, 6=ms5, 7=ms10
# ext: 8=ms3, 9=ms4
dl_UL_TransmissionPeriodicity = 8;
nrofDownlinkSlots = 3;
nrofDownlinkSymbols = 6;
nrofUplinkSlots = 2;
nrofUplinkSymbols = 4;
# pattern2
pattern2: {
dl_UL_TransmissionPeriodicity2 = 4;
nrofDownlinkSlots2 = 4;
nrofDownlinkSymbols2 = 0;
nrofUplinkSlots2 = 0;
nrofUplinkSymbols2 = 0;
};
```