Configuring a Downlink Signal Under TDD Frame Structure

In this tutorial, TDD frame structure below will be used, which is a DDDSU slot pattern with 2.5 ms repetition period. In the special slot, symbols allocated for downlink, gap and uplink are 10:2:2 respectively. To configure the downlink signal in this slot pattern, two separate DL-SCHs will be needed to represent two different channel configurations in terms of symbol allocation within the slot. In Signal Studio, channel resource allocation in time domain is on a slot basis. Each DL-SCH or UL-SCH represents a particular channel configuration that can be transmitted in multiple slots, by specifying ‘Allocated Slots’ property of that channel. 

Specifically, the parameters in DL-UL-ConfigCommon IE for this configuration is as table below, assuming SCS = 30 kHz and carrier is FR1 100M.

Field name

Value

dl-UL-TransmissionPeriodicity

2.5 ms

nrofDownlinkSlots

3

nrofDownlinkSymbols

10

nrofUplinkSlots

1

nrofUplinkSymbols

2

  1. Start N7631C Signal Studio with the default FR1 100M, SCS = 30 kHz downlink carrier.

  2. Under Channel Setup node, click SS/PBCH button, then turn off it since it’s not needed in this example.

  3. Click DL-SCH button, change channel name from DL-SCH1 to DL-SCH-D to represent the channel transmitted in downlink slots. Then change Allocated Slots to 0:2,5:7,10:12,15:17 that corresponds to those downlink slots in this frame structure. By default, this channel will have First Symbol = 0, Last Symbol = 13, indicating that all symbols are allocated for downlink in one slot.

  4. Click ‘+’ icon to add a new DL-SCH for the channel transmitted in special slots, with the name of DL-SCH-S. Then change Allocated Slots to 3,8,13,18 that corresponds to those special slots in this frame structure. Furthermore, change Last Symbol to 9, indicating that only 10 symbols within the special slots are allocated for downlink. Now the channel list should look like below.

  1. Take a look at the resource allocation graph in Signal Studio, it could be marked as below to match up with this particular TDD frame structure.