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Hi Faisal,

I guess you tested per test sample.

Firstly as for abbreviations, RSSI is Received Signal Strength Indication/Indicator that means measured electric field strength at receiving point and indicated as unit dBm.

PER is the abbreviation for Packet Error Rates that means the ratio of packets not received correctly within whole sent packets.

The more RSSI (absolute value is lesser), the more reception condition is better and inversely the less PER, the more receiving packets goes well.

"total packet length if we use smartrf studio software shipped with the kit and using PACKET TX. & RX. OR CONTINEOUS TX. & RX. application = 120 Byte

but the manual says that total payload can be set upto 103 Bytes, how come we set payload to 120 Byte as the studio give option."

See line 29 and 45 in per_test.h and  line 295 in per_test.c

Real sent packet bytes is the size of structure " perTestPacket_t ", I think it wouldn't exceed " MAX_PAYLOAD_LENGTH ".

" how does the TX. AND RX. boards in the kit recongnize each other? "

See line 244 in per_test.c, transmitter's own short address is set and in line 145, receiver's own short address is set too.

Only if transmitter designates destination short address (i.d. receiver's short address), it can send for the proper receiver.

And don't forget to set also PAN ID, see line 346 in per_test.c.

" what is the inter-pkt delay between two packets. if i use the PKT TX & RX. application in studio what will be the packet rate? "

Sorry I couldn't get exactly what you meant, you mean how per is measured in this sample?

If it is,the calculation is quite simple.

Transmitter send number sequence of integer and receiver only counts the received packets if it arrived in number of lost some.

If you still have some question, ask again.

Thanks,

Thucydides

thanks thucydides for your kind reply.

i mean if i set pkt rate = 100 pkt / second then what is the delay or gap between two successful packets. (INTER-PACKET DELAY OR GAP IN MICRO OR MILLI SECOND)

also the kit have option to TX. at -3, 0, 4 dBm transmit power. can i simply convert this dBm into mwatt or add dbi to this dBm to get dBm (EIRP) and convert that into mwatt?

dbi + (-3 or 0 0r 4 dBm) = dBm, if yes then what is the dbi for cc2530 dk board.

how can we calculate signal to noise ratio from RSSI & PER Value?

thanks

Hi Faisal,

"i mean if i set pkt rate = 100 pkt / second then what is the delay or gap between two successful packets. (INTER-PACKET DELAY OR GAP IN MICRO OR MILLI SECOND)"

I see what you mean.

I haven't measured single packet propagation time between two hardwares.

It's not physically impossible, but not easy.

But if you only have to know statistical average bps, you can calculate easily.

On my experience, pragmatic safe bps (per is under 4 or so)  under bad condition was about only 4kbps (250bps is only theoretical possible value but almost impossible in real),.

Assuming a packet length is 10 bytes (i.e. 80 bits),  so the transmit interval will be 50 packets/sec.

So it means you can send next packet after 0.02 sec.

"also the kit have option to TX. at -3, 0, 4 dBm transmit power. can i simply convert this dBm into mwatt or add dbi to this dBm to get dBm (EIRP) and convert that into mwatt?"

As you may know 0dBm equals 1mW. so you can calculate using this.

real value = 10^([dB]/10)

"how can we calculate signal to noise ratio from RSSI & PER Value?"

It would be impossible using these values.

You need to measure the noise intensity or spurious physically.

S/N ration and per is essentially quite different.

I hope it would be helpful for you.

Thucydides

very very thanks thucydides, your ans help me really lot, actually i measure the impact of wifi interference on wsn and also interference between wsn and wsn. as i set two cc2530 dk as TX and one board as RX. set the same config. on transmitters i.e. CH=11, PWR= - 3dBm, Total PKT = 1000, RATE= 100 PKT / s. as i start the TX. simultenuosly then RX. seems hang during test (10 s) and after that period showed

PER = 0/ 1000

RSSI = -53 dBm

Received = 2

what that showed?

also i try to start one Tx. with 3 second delayed then

PER = 0 /1000

RSSI = -52 dBm

Received = 384

i want to know what Tx. packets (384) are that? i came to point as the RX. normally received PKTS (384) till the start of 2nd Tx. and when the second one start all PKTS lost or never reached to RX. due to interference?

AM I RIGHT?

Hi Faisal,

"as i start the TX. simultenuosly then RX. seems hang during test (10 s) and after that period showed"

It's quite often occurring problem, after weak signal continued for some time.

I checked it using debugger, while CPU core is running but only RF packet receive stops after weak signal continued and if once RF packet receive stopped I need to restart cc2530 its self.

I asked to TI technical support but they said there's a only way to restart by user program.

For  in case of recognized No RF, I wrote program like this

while (!RfPacketIsReady()){
    // loop count of No RF
    No_packt_times += 1;
    // over the fixed continuous No RF number
    if((No_packt_times >= NO_PACKET_LIMIT)
    &&(No_packt_times = Previous_No_packt_times + 1)){
        No_packt_times = 0;
        // Need to initialize for RF
        RF_Init();
    }
    Previous_No_packt_times = No_packt_times;
}

"PER = 0/ 1000

RSSI = -53 dBm

Received = 2

what that showed?"

per = 0 means all packets sent safely,

rssi is the intensity of received packet

received means received packet number

 "normally received PKTS (384) till the start of 2nd Tx"

No,  Tx sends periodically with fixed interval without regard that previous packet was safely received or not.

Could I answered to your question properly?

Thycydides

Hi Faisal,

Sorry for late response.

Telling truth, I didn't get what you mean.

"1. what is the csma/ca i.e cca in manual testing(using default PER application with the board)"

You said about the general network access method (Carrier Sense Multiple Access With Collision Avoidance)?

Or about command strobe/CSMA-CA processor (CSP) explained at p. 211 in the swru191?

" i want to set cca of one of the TX"

I think it's impossible to set, since CSMA/CS is not value but method name.

"such that it sense the medium busy backoff and then send its transmission after busy medium is free. "

I didn't understand what did you want to do. Please explain more in detail.

"3. i also test the dk with the wifi A.P (access point) to see the interference? what is the dk cca in that case means does the cc2530 dk board sense the medium if wifi traffic is in progress. and vice versa (wifi can also sense the wsn transmission if wsn transmitting its data?)"

I can only say that, if you so the per measuring test, you'll see usually per is not perfect zero.

It means unless under the quite good condition, all packets are not always transmitted perfect, and some data in packets will be collapsed.

So you can imagine easily if other 2.4G wireless waves coexist, per became worse.

I think It's worth to measure the correlation.

"4. the PER application pre-programmed with kit does not hav option to set CCA (clear channel assesment). am i right?"

Yes, right, but what is the "CCA" that you wrote?

Thanks,

Thucydides

Hi Faisal,

I recommend you to read swra285 , similar experiment is treated.

"i want to ask as both WIFI and WSN employes CSMA/CA then why interference between the two?"

It's a quite simple reason. Stack provided for DK board doesn't use congestion control like the CCA especially but only uses 802.15.4 packet format for sending.

So the per test program always tries to send simply and if there are  interferences, the per value will increase.

This time, was it enough for you?

Thucydides