This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Improving link performance (robustness / co-existence) in a PPW network

Other Parts Discussed in Thread: CC8531, CC2591

There are multiple factors influencing the overall robustness and co-existence performance of a PurePath Wireless network. Depending on the application, there can be trade-offs made to improve this

There are things that can be done to improve the audio link performance, but usually associated with a 'cost':

  • Always keep the number of slaves to the lowest possible for a given application. In a multi-cast protocol, time is set aside for each possible slave for potential re-transmissions. If only 1 slave is needed, robustness will be worse if you enable more slaves to join the master etc.
  • Reducing the audio sample rate will increase the total retransmission capacity. However, if the audio latency setting (in number of samples) also is reduced by the same factor to maintain latency "in time", the maximum number of retransmission attempts per slice is reduced. 
  • Latency is a direct trade-off vs. robustness. One is directly trading retransmission attempts for the lower latency. At the lowest settings this goes towards zero retransmission attempts.
  • Number of audio channel supported. The more channels supported, the more bandwidth is needed over the air and the less robust the link will be. 
  • Direction of audio. Typically audio from master to slave is better when having uni-directional audio. For bi-directional links they are equally robust., 
  • The various streaming formats requires different band-width. SLAC is more robust than PCM16 format.
  • Increasing target output power and using the CC2590 range extender. Improves range at the cost of power consumption and to some extent co-existence.
  • Audio fade-out on mute events can be disabled (under advanced settings) for slightly better re-transmission capability.
  • Data side-channel. Note that enabling the use of data side-channel in host control mode will set aside a good portion of the available BW within a timeslot to data. This will significantly reduce the overall capacity for audio re-transmission in the timeslot. Optimal setting is Autonomous or Host control without data side-channel.
  • RF data-rate. 2 Mbit settings is less vulnerable to RF multi-paths and improves sensitivity. This will have a positive effect on range, but is restricted to a few application. See configurator help system for more info.
  • Antenna diversity: If implemented on slaves, it will combat multi-path effects and improve the in-range performance.
  • Changing or disabling LBT: http://e2e.ti.com/support/low_power_rf/f/382/t/326031.aspx

It is up to the end user to consider which, if any, of the above is valid for their application. 

Regards,
PPW team

  • Hi, PPW team

    We have couplt of wireless microphones(low latency is a must) by using CC8531, with RFX2401 RFIC, 2 microphones,a serious problem comes out: too short range!

    We got 20dBm TRP, although did not check the receive sensitivity, but it should be ok, the NF of the RFX2401 is 3dB, with 12dB LNA gain, but the range it too short to accept. Also we have some demo boards from TI, with CC2591 on the boards, it looks your reference design is even worse with the same configurations.

    More info about our configurations:

    2 slaves

    48K sampling rate

    Latency: 14.5ms(even it is still far away from the spec)

    2 channels

    SLAC enabled

    RFX2401 RFIC

    Audio fade-out on mute events disabled

    No data side-channel

    5Mbit data rate

    No antenna diversity(no space on the board)

    Diabled LBT

    We are struggling on this issue, it is a very important product line to our company, and hopefully we can get more support here, I definitely cannot expect too much from the local supporting guys.

    -Marshal

  • Hi,

    What range are we talking about here? Can you give some info about what you are aiming for and what you currently get?

    Regards,
    Johan 

  • Hi, 

    It depends on the enviroment strongly, some places with fewer 2.4G interferences, it is kind of ok, 30-50m is acheivable, or even further. With strong interferences, less than 5m, even 3m, which is definitley a toy. Increasing the latency can improve the range, but it is not our target, even with 14.5ms latency, it is unacceptable at all, from the boss's opinion. Also we did the comparision with TI reference boards, looks the boards are even worse, at almost the same time, same places.

    -Marshal

  • BTW, the range I am talking about is the operational distance between the transmitter and receiver.

  • If there are any testing reports for coexisting performance of CC8531 solution, that should be a reference for us, we need to consider if keep going with CC8531 or change to other direction, to be honest, without enough evaluation at the beginning, now it is almost the time for MP,  and find out that they are not good products to launch into the market.

    Any useful info from your side are appreciated. We need to know the limitation of the solution asap.

  • Hi, I also am finding that for 2.4ghz the cc85030 with PA is lacking in range ! I am also testing diversity which improves link quality fractionaly but range is no better.It would be useful if TI could comment on this or publish or point to some useful range tests? Its frustrating that the master cannot have diversity with slaves using best rssi on master reciever antennas for microphone applications. why was it implimented the other way around forcing the microphone as slave with dual antennas on the TX? strange choice?