Hi all,

i'm working on the IEEE 802.15.4 standard, and the spec for interference is +0 dB at 5 MHz offset and +30 dB at +10 MHz offset. Is this the total integrated interfering power, or is it the maximum power of a sinusoid at a fixed offset.

The reason i'm asking is that the likelihood of receiving a pure sinusoid with 30 dB more power than the desired signal is very low. More likely, that 30 dB higher power is spread over a broad band making it easier to filter.

thanks,
Aaron

Hi,

thanks for the reply. I understand that it is a spectrum mask. However, when we do a frequency domain plot I think we usually either use PSD, or power at a single frequency. The spectrum mask usually covers a band. So for 802.15.4 the adjacent and alternate channel interference requirements are +0 dB and +30 dB.

So taking the +0dB case, assume we receive -85 dBm. Is the interferer:

1) -85 dBm at 5 MHz offset
2) -85 dBm/Hz from 5 MHz onwards (very unlikely)
3) -85 dBm spread over a frequency band (for example 2 MHz) leading to -148 dBm/Hz.

I guess (1) and (3) don't lead to very different receiver specs. However, the second part of my question is, can we assume that to meet standard requirements, the total interference power is -85 dBm + -55 dBm?


thanks,
Aaron

Here is a coexistance oriented paper that does discuss your issue; however, I think even they had to assume some sort of practical interfer scenario because the spec is too vauge.

Yong-Kuk Park; Won-Gi Jeon; Hae-Moon Seo; Yeon-Kuk Moon; Jaeho Kim; Byoung-Chul Song; Kwang-Ho Won; Myung-Hyun Yoon; Jun-Jae Yoo; Seong-Dong Kim, "RF Receiver Specifications of Ubiquitous Network for Coexistence with Various Wireless Devices in 2.4GHz ISM-band," Communications, 2005 Asia-Pacific Conference on , vol., no., pp. 595-599, 03-05 Oct. 2005

For a particular specification you can also send an inquiry to the working group for the spec, or the industry alliance group asking for clarification.