On the suitability of the 433 MHz band for M2M low‐power wireless communications: propagation aspects

Abstract

The 433 MHz band is gaining relevance as an alternative to the 2.4 GHz band for machine-to-machine communications using low-power wireless technologies. Currently, two standards are being developed that use the 433 MHz band, DASH7 Mode 2 and IEEE 802.15.4f. The article presents propagation models based on measurements conducted at the 433 MHz and 2.4 GHz bands that can be used for link budget calculations in both outdoor and indoor environments depending on node height. The results obtained show that the 433 MHz band has a larger communication range in both indoor and outdoor environments despite the negative effects of having a larger Fresnel zone. In addition, indoor propagation measurements are conducted in line-of-sight and nonline-of-sight conditions to determine the suitability of channel hopping to combat the effects of multipath propagation. Contrary to the 2.4 GHz band, the results show that channel hopping at 433 MHz does not provide any link robustness advantage because the channel coherence bandwidth is larger than the whole band bandwidth, and thus, all channels are highly correlated.

Why is frequency channel diversity so beneficial in wireless sensor networks?

“…At 1m, much like previously experienced at a few meters in the 433MHz band [8], we do not expect that changing frequency would have much effect: accordingly, there is hardly any gain variation above 6dB in the histogram at the top in Figure 2a. However, Figure 2b shows a different behavior: at 1m indoors, gain changes of 6 dB or above are common.…”

Communication techniques and challenges for wireless food quality monitoring

“…Another full evaluation kit by Agaidi Oy, Finland, which is no longer available for purchase, is also in circulation. [34] found that 433 MHz was significantly better in free airspace by field tests and theoretical analysis. Our outdoor tests with 433 MHz wireless nodes were conducted with OpenTag running on the Agaidi evaluation kits, based on the CC430F5137 SoC.…”

LPDQ: A self-scheduled TDMA MAC protocol for one-hop dynamic low-power wireless networks

“…This is due to the fact that the channel coherence bandwidth at the sub-GHz bands is larger than the available bandwidth [33], which causes that all the channels of the band are highly correlated. Taking into consideration these results, other mechanisms may be required to add robustness against multi-path propagation in LPDQ implementations that operate at Sub-GHz bands.…”

“…For our implementation, we have used a data rate of 250 kbps, which yields a measured sensitivity of -91 dBm for a PER (Packet Error Rate) of 1% transmitting packets of 20 bytes and using a channel bandwidth of 540 kHz. This data rate has been selected because it is equivalent to that of IEEE 802.15.4 and achieves the least energy consumption per bit while offering a range that has been measured to be 1.6 times that of the 2.4 GHz band in real conditions [33]. In case that a longer range is required, the lower data rates defined in the standard, e.g., 31 kbps or 100 kbps, can be selected at the expense of increasing the energy consumption per bit if the transmit power is kept constant.…”