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CC1350: Interference of different sub-ghz networks

nada wael
Intellectual 380 points
Part Number: CC1350

If I have two cc1350 boards communicating with each others using subghz at 868 freq band and another two boards communicating with each others using subghz at 868  freq band, find the questions below:

1.  Can I prevent the interference in the data sent and received in the two different subghz networks while using the same frequency band?

2. Is there a minimum distance that should be between the two different networks to prevent the interference of the data in both networks?

  • 0
    TI__Mastermind 27145 points

    Hi,

    For Q1: Yes, you can separate in Frequency as much as possible and also you can use Time Division between those 2 networks.

    For Q2: Please refer to Selectivity and Blocking specs in the data sheet to calculate the Link Budget and the distance to be maintained between the networks to prevent interference from each other.

    You may use our Range Estimator to calculate the Signal/Interferer level / Distance / Range. The following is the link. Please see under software development.

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 380 points

    Can you tell me more about the separation in frequency and the time division?

  • 0 in reply to PM
    Expert 1350 points

    1. By separation in frequency, do you mean the idea of selectivity? and How can I implement the Time division multiplexing in both networks?

    2. I found the info about the selectivity in the datasheet, to make sure that I understood correctly the mentioned range of ± 400 kHz and ± 800 kHz at 100 kbps in page 19 in the datasheet means that one network will operate on the 400 kHz frequency and the other on 800 kHz, right?

    If so, I need the difference in frequency to be less than 400 kHz as in the future there will be more than two networks, so I need to know if you have other tests at different data rates or where can I find the RF parameters calculations needed in such case?

  • 0 in reply to Nada Wael
    TI__Mastermind 27145 points

    Hi,

    Q1: Yes, you can use Frequency Separation between the networks as high as possible. The higher the frequency separation between the networks gives lower interference between each other. TDMA implementation means you can time division between the networks. That means if one network is transmitting and the other network in standby / sleep mode at the same time. Only one network on operation at that time. You may need to time sync both networks for TDMA application.

    You can also use LBT (Listen-Before-Talk) function to avoid interference from one network to other network. This function monitors the environment for any RF signal in the band  before it transmits and if it detects the signal above the Threshold level then it won't transmit. When the channel is free then only it transmits.

    Q2: No, need to stuck for 400KHz and 800KHz separation. You can separate the Frequencies as much as possible ( allowed in your Operating Frequency band). More separation is better. You can see Blocking spec also. on the same page.

    Please refer to Selectivity and Blocking specs and also figures 5.21 and 5.23 in the data sheet.

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 380 points

    Q1. I can not use high frequency separation as there might be more than two networks adjacent to each others operating in 868 frequency band. Concerning the listen before talk function, what do you mean by (if it detects the signal above the threshold level) ? What is the threshold level?

    Q2. Blocking is for preventing interference between networks that operate in different frequency bands, right? If so, this will not help me as all the networks will operate in the same frequency band.

    Thank you

  • 0 in reply to nada wael
    TI__Mastermind 27145 points

    Hi,

    Q1: Are you familiar with ETSI Specs?

    Please refer to sections 9 and 8.2 of EN 300 220-1 V2.3.1. You can google it for this standard.

    Q2: What is your Frequency Band?

    Thanks,

    PM

  • 0 in reply to nada wael
    Intellectual 380 points

    Q1. I will check it

    Q2. 868 MHz

  • 0 in reply to nada wael
    TI__Mastermind 27145 points

    Hi,

    Q2: What is the  Lower Freq Limit  and Upper Freq Limit in the Band OF 868MHz?

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 380 points

    Q2. How can I know the upper and lower frequency limit?

    Q3. How to know the right values for the rf parameters to get the desired frequency in the smartrf studio?

  • 0 in reply to nada wael
    TI__Mastermind 27145 points

    Hi,

    What is the application of this project?

    In which country you are going to use?

    Q1: You need to know what is the Unlicensed band (868MHz band) in your country? 868MHz means it is a single frequency, 868MHz band means it has group of Frequencies ( for example 868.000MHz to 868.600MHz is the band).

    Q2: It seems you are new to SmartRF Studio. Please open help button in SmartRF Studio and read the "Device Control Panel" documentation. You can use one of the standard settings under "Typical Settings"

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 380 points

    Subghz project several cc1350 networks adjacent to each others and i do not want an interference to happen

    The country is egypt

    868 MHz band

    I already set the parameters before for a specific frequency but there is no specific parameter to set the desired frequency, there is the deviation and Rx BW to set the desired value for the frequency