.. _sec-channel-Sounding-Timing-Parameters:

Channel Sounding Timing Parameters 
==================================

Many parameters impact Channel Soundings procedure duration. Bluetooth® LE 6 
specification defines mandatory and optional values for some of these parameters. Other 
timing parameters are fixed.

The two first sections below show the settings defined by the specification. The first 
includes the parameters having several possible values and which one are supported by |STACK|. 
The second, the fixed ones as defined in the specification. The third one shows the timing 
parameters based on the packet view.

.. _sec-Variable-Parameters :

Variable Parameters 
^^^^^^^^^^^^^^^^^^^

.. table::    

            +------------------------+------------------------------------------+---------------------------------------------+
            | Parameter              | Description                              | Supported                                   |
            +========================+==========================================+=============================================+
            | T_FCS                  | Time for Frequency Change Spacing        | 80 µs | 100 µs | 120 µs | **150 µs**        |
            +------------------------+------------------------------------------+---------------------------------------------+
            | T_IP1                  | Time for Interlude Period 1              | 40 µs | 50 µs | 60 µs | 80 µs | **145 µs**  |
            +------------------------+------------------------------------------+---------------------------------------------+
            | T_IP2                  | Time for Interlude Period 2              | 40 µs | 50 µs | 60 µs | 80 µs | **145 µs**  |
            +------------------------+------------------------------------------+---------------------------------------------+
            | T_SW                   | Time for antenna switch                  | **1 µs** | **2 µs** | **4 µs** | **10 µs**  |  
            +------------------------+------------------------------------------+---------------------------------------------+
            | Optional PHY supported | Physical layer                           | RFU | 2M PHY | 2M BT PHY                    |                   
            +------------------------+------------------------------------------+---------------------------------------------+
            | T_PM                   | Time for Phase Measurement               | 10 µs | 20 µs | **40 µs**                   |
            +------------------------+------------------------------------------+---------------------------------------------+
        
.. note::
     Bolded values are mandatory, the others are optional.

.. _sec-Fixed-Parameters :

Fixed Parameters 
^^^^^^^^^^^^^^^^

.. table::    

            +-----------------+------------------------------------------+----------------------------------------+
            | Parameter       | Description                              | Supported                              |
            +=================+==========================================+========================================+
            | T_FM            |  Time for Frequency Measurement          | 80 µs                                  |
            +-----------------+------------------------------------------+----------------------------------------+
            | T_GD            |  Time for Guard period                   | 10 µs                                  |
            +-----------------+------------------------------------------+----------------------------------------+
            | T_RD            |  Time for transmission (RampDown)        | 5 µs                                   |
            +-----------------+------------------------------------------+----------------------------------------+
            | T_SY            |  Time for synchronization sequence       | LE 1M PHY  = 44 µs                     |
            |                 |  (CS packet)                             | | LE 2M / 2M 2BT = 26 µs               |
            +-----------------+------------------------------------------+----------------------------------------+
            | T_MAX_PROCEDURE |  Time after a CS procedure is considered | RFU | 2M PHY | 2M BT PHY               |
            |                 |  complete and closed                     |                                        |
            +-----------------+------------------------------------------+----------------------------------------+



Parameters details
^^^^^^^^^^^^^^^^^^

* T_FCS 


.. ditaa::

    +------------------------------------------------------------------------------------------------+
    |                                                                                                                              
    |                                           Procedure                                            
    |                                                                                                
    +------------------------------------------------------------------------------------------------+

    +--------------------------------------------------------------------------+   +-----------------+
    |                                                                          |   |                 
    |                                Event                                     |   |        Event    
    |                                                                          |   |                 
    +--------------------------------------------------------------------------+   +-----------------+

    +-----------------------------------+  +-----------------------------------+   +-----------------+
    |                                   |  |                                   |   |                 
    |             Subevent              |  |              Subevent             |   |      Subevent    
    |                                   |  |                                   |   |                 
    +-----------------------------------+  +-----------------------------------+   +-----------------+
                                           
    +-----+----------+ +-----+----------+  +-----+----------+ +-----+----------+   +-----+-----------+
    |     |          | |     |          |  |     |          | |     |          |   |     |           |
    |T_FCS|   Step   | |T_FCS|   Step   |  |T_FCS|   Step   | |T_FCS|   Step   |   |T_FCS|   Step    |
    |     |          | |     |          |  |     |          | |     |          |   |     |           |
    +-----+----------+ +-----+----------+  +-----+----------+ +-----+----------+   +-----+-----------+
    

* T_IP1 and T_RD


 .. ditaa::
    
                      +--------------------------+                             +-------------+------------+ 
                      |                          |                             |             |            |
    CS step mode 0    |       CS_SYNC_0_I        |    T_RD          T_IP1      | CS_SYNC_0_R |   CS_TONE  |    T_RD
                      |                          | <---------> <-------------> |             |            | <--------->
                      +--------------------------+                             +-------------+------------+

                      +--------------------------+                             +--------------------------+ 
                      |                          |                             |                          |
    CS step mode 1    |        CS_SYNC_1         |    T_RD          T_IP1      |        CS_SYNC_1         |    T_RD
                      |                          | <---------> <-------------> |                          | <--------->
                      +--------------------------+                             +--------------------------+
                                              
                                                                         
* T_IP2 and T_RD

 .. ditaa::
                      +--------------------------+                             +--------------------------+ 
                      |                          |                             |                          |
    CS step mode 2    |         CS_TONE          |    T_RD          T_IP2      |         CS_TONE          |    T_RD
                      |                          | <---------> <-------------> |                          | <--------->
                      +--------------------------+                             +--------------------------+ 

 .. ditaa::
                      +-------------+-----------+                              +-------------+------------+
                      |             |           |                              |             |            |
    CS step mode 3    | CS_SYNC_3_I |  CS_TONE  |     T_RD          T_IP2      | CS_SYNC_3_R |   CS_TONE  |    T_RD   
                      |             |           |  <---------> <-------------> |             |            | <--------->
                      +-------------+-----------+                              +-------------+------------+
                                                           

* T_SW and T_PM

.. _Antenna_switch_procedure: 
.. figure:: resources/Antenna_switch_procedure.png
    :align: center

    Antenna switch procedure in a 3:1 configuration with the antenna path permutation slot

* T_FM

.. ditaa::
                                      +-------------+------------+ 
                            T_IP1     |             |            |           T_FM                 T_RD
    CS Step Mode 0    <-------------> | CS_SYNC_0_R |   CS_TONE  | <-------------------------> <--------->
                                      |             |            | 
                                      +-------------+------------+

* T_GD, only for Mode 0 and Mode 3 steps.  

.. ditaa::
                            +------------------------+             +------------------------+
                            |                        |    T_GD     |                        |
    CS Step Mode 0          |      CS_SYNC_0_R       | <---------> |         CS_TONE        |
                            |                        |             |                        |
                            +------------------------+             +------------------------+

                            +------------------------+             +------------------------+
                            |                        |    T_GD     |                        |
    CS Step Mode 3          |      CS_SYNC_3_X       | <---------> |         CS_TONE        |
                            |                        |             |                        |
                            +------------------------+             +------------------------+

* T_SY 

.. ditaa::
        

        +---------------------------+
        |                           |
        |          CS_SYNC          |
        |                           |
        +---------------------------+
        <--------------------------->
                    T_SY