I'm doing a project on live audio streaming through xbee. The baud rate we are using is 115200. Audio transmission works perfectly through wired UART connection. But when we performed wireless communication through xbee, audio got distorted. I think the problem is within the xbee data rate. How can i solve this issue?

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    \$\begingroup\$ What is the audio sampling rate? Which xbee band are you using? 2.4GHz? 915MHz? 868MHz? Which modules are they? Need more information. \$\endgroup\$ – Martin Jan 13 '14 at 7:57
  • \$\begingroup\$ As above more information is needed. If it works with a wired UART latency is a likely problem so it'd also be worth adding what platform it's connected to, you'll probably need some RAM available for buffering. \$\endgroup\$ – PeterJ Jan 13 '14 at 8:01
  • \$\begingroup\$ sampling rate is 16kHz and the xbee band is 2.4GHz. I'm using xbee series 1. \$\endgroup\$ – Linu Das Jan 13 '14 at 8:10
  • \$\begingroup\$ "distortion" implies clipping to me - can you be more specific? \$\endgroup\$ – Andy aka Jan 13 '14 at 8:17
  • \$\begingroup\$ actually it is not clipping. I think we are getting uneven samples. actually the tone of output voice and the original voice are different. \$\endgroup\$ – Linu Das Jan 13 '14 at 8:23

Like Jerome said, your XBee module is probably at its limits... but here are some factors you may still be able to change, and other you probably can't:

  1. Forward Error Correction (FEC, CRC, etc). Higher FEC lowers throughput, but decreases errors.
  2. Transmitter Output power - The higher, the better SNR & Eb/N0 and lower Bit Error Rate (BER), but consumes more power.
  3. Channel noise - the lower, the better SNR & Eb/N0.. again lower BER. Make sure you are transmitting on a clean channel. If you are on 2.4GHz or 5.8GHz, wifi is probably interfering.
  4. Antenna gain - higher gain (more dBi) antennas will give you more EIRP horizontally (but less vertically). I would recommend atleast a 6dBi antenna for 360-horizontal applications. You are allowed a MAX EIRP of 36dBm in the ISM bands (2.4GHz, 900MHz, 5GHz, etc). The higher your EIRP, the longer distance you can transmit.
  5. Modulation Scheme (for example: QPSK is one of the most robust modulation schemes, FHSS is slow, FSK is a bandwidth hog)
  6. Dispersion & Multipath in a channel (OFDM is a better modulation to fight this)
  7. RF Bandwidth - the higher the more baseband bandwidth you can use
  8. Carrier Frequency - 2.4GHz is smaller & cheaper, but very noisy; 900MHz is much better in terms of multipath and noise.

You will probably have to google some of these terms...

Alot of these factors are locked as soon as you purchase a transceiver. Some of these you can change. You need to make sure that you have the best system and settings for your application.

Without knowing the model of your chipset, my guess is that the only things you probably have control of is:

1, 2, & 4


Generally speaking, I don't think xbee/zigbee network is suitable for this type of communication: high throughput, and real time. The throughput of xbee network can be as high as 35kbps, but many factors like structure of network, presence/absence of interference, distance of nodes etc can decrease throughput. The actual throughput can be anywhere between 0-35kps, it may or may not be sufficient for your purpose, and the transmission is subject to delay up to a few seconds.

All in all, I would suggest you try something else like wifi.


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