CC2430 chip, voice over zigbee, should I use codec?

hi all,

i have been working on CC2430 chip which use zigbee(802.15.4) protocol for communication. i need to do realtime voice communication by using it.

should i definitly use codec before sending voice?
What is the important part of realtime communiation? i used 8 bit adc and sample frequency is 8 khz. and 8 bit dac to convert to analog again. The bit rate of zigbee is 250Kbps (K bit per second).

without sending voice packet, i tried to produce voice with microphone and converted it with adc and again converted it to analog with dac and used amplifier before speaker. i heard voice well. this part worked good enough. i mean the problem is sending voice packet via rf. when i tried to send voice via rf i heard some meaningless sounds from speaker.

thanks for helps...

Re: voice over zigbee

from wiki..

ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking.

Click to expand...

Using it in realtime communication is not advisable. Try some thing else.

Nandhu

Re: voice over zigbee

Hi

In order to that you will need to sample the voice (using ADC) at known sample rate
(most voice can be sampled using 8 KHz sample rate)

To save band width you will also need to compress the voice using a known algorithm like ADPCM Or G721(more complex)

And then you can send the DATA via the radio channel

In the other side you will need to decompress the DATA and send it to the DAC using the same sample rate

All the best

Bobi

The microcontroller specialist

Re: voice over zigbee

2.4GHz IEEE 802.15.4 has a burst rate of 250kbps over the air. Adding overhead like CCA, frame structure, and such, the best implementers have been able to squeeze about 110kbps continuous, one-way. I'd strongly suggest that you use only about 5% of that bandwidth for good performance. Also, remember that the 15.4 data frame has room for about 118 bytes of payload, but with networking and apps overhead that can drop as low as about 80 bytes. Any voice sample you send really needs to fit in 1 packet, no more.

Like the cat sez, you'll need a good comms-grade voice codec to compress the audio. You want a data stream out of the codec that is 3 to 8kbps average and with individual blocks that are no more than 80-100 bytes in length. (note that GSM has a codec that can operate down to a few kbps, depending on the traffic). With the right codec, you should be able to get away with one transmitted packet every 50 ms. That automatically defines a minimum latency of at least 100ms for the voice channel, even if the codecs are really fast. So maybe use packets on 25ms intervals, but half as long?

I have a pair of 802.15.4 "homemade" "walkie-talkies" here that work pretty well and have excellent battery life. Range at +3dBm with fullsize 1/4-wave antennas is about 500m open air, line of sight.

luis

Added after 10 minutes:

nandhu015 said:

from wiki..

ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking.

Click to expand...

Using it in realtime communication is not advisable. Try some thing else.

Nandhu

Click to expand...

The IEEE 802.15.4 standard does not mandate use cases. It's really how you want to take advantage of the technology, so long as you stay within the rules of your particular regulatory environment.

ZigBee using 802.15.4 does support voice functions. See

**broken link removed**

Note about 2/3 ways down in the press release, the feature called "Voice over ZigBee"...

luis