nRF5340 audio CIS versus BIS maxium distance

[TueTD]

Hi team,

I setup two nrf5340 Audio DK boards in BIS mode, CIS mode (walkie talkie) and measured the longest distance the boards could synchronize the audio. After several testing times, CIS (walkie talkie) is always longer than BIS mode. 

 + BIS: around 60m.

 + CIS(Walkie Talkie): around 110m. 

I also have 2 custom board using nrf5340 chipset and i archived the same result with the same test. So my questions are:

1. Is there a difference  in BIS mode and CIS mode range?

2. Can you show me nrf5340 Audio DK's distance test results, or something similar with my test? 

I am using NCS V2.2.0 and I don't change any config related to TX_POWER.

[Amanda Hsieh]

Hi, 

That is strange. In theory, BIS should have longer (or at least the same) range because of no ACK. It also looks like BIS has 4 retransmits and CIS has 2.

Are you using the same SDU size (audio frame size) for both BIS and CIS?

Can you test with NCS v2.4.0?

Regards,
Amanda H.

[TueTD]

Hi Amanda,

Since the configurations of the LC3 codec are the same (bitrate, sample rate, number of channel, bit depth) for both mode so i think i have used the same audio frame size. To be sure, i will clarify this in next week.

Yes, i have also tested with the v2.4.0 version. The result still remains CIS has longer range than BIS.

To be more specific about the test, I place the gateway on the ground and move the headset away from it until they cannot synchronize again (within minutes)

+ BIS mode: At 50 meters, boards lost sync. I waited for minutes and did the reset but they cannot sync again unless I moved both boards closer.

+ CIS mode: From 50 meters, sometimes 2 boards lost synchronize but they can re-sync again (in seconds). I tested until the distance reached 130 meters.

[Amanda Hsieh]

Hi, 

Please add the following config for BIS and try again. 

CONFIG_BLE_ACL_PER_ADV_INT_MIN=80

CONFIG_BLE_ACL_PER_ADV_INT_MAX=120

These will make the periodic ADV interval shorter.

-Amanda H.

[TueTD]

Hi Amanda

Thanks for suggestion, i'll try it out 

[TueTD]

Hi Amanda,

I have tried add your config to shorten ADV interval in BIS. Nothing was improved. I did the test again, CIS was still better range than BIS. SDU is the same for both mode.

It seem the HS is still in the GW's radio range but the HS couldn't sync even when I did the soft and hard reset

[JONATHAN LL]

Hi,

Amanda is currently on vacation so I am taking over the case for now. 

Seems like we don't have any number so share right now, is this a urgent matter for you?

And is it a requirement that CIS and BIS has the same range? What is the criteria or use case here that needs to be achieved or is it mostly curiosity? 

Regards,
Jonathan