Wi-Fi Halow: understand this technology!
The first important feature of HaLow Wi-Fi comes from the frequencies used, which are in a free band below 1 GHz, giving a much improved range compared with the traditional 2.4 and 5 GHz bands. In particular, these frequencies penetrate obstacles such as walls much better. However, this small free band does not use exactly the same frequencies between Europe, the United States, China, etc. The figure below shows the frequencies and bandwidth in various countries. Europe has the smallest bandwidth, which could be a problem as objects become more powerful.
Frequencies and bandwidth used by HaLow Wi-Fi technology.
Another advantage of using low frequencies, below 1 GHz, just above the gold frequencies used by operators, is that energy consumption is much lower. The waves propagate better and, even when the range is doubled, the Wi-Fi component consumes much less. There’s also a standby mode to save energy, and the technology’s much lower data rate means it can carry more robust signals. The HaLow standard is therefore well suited to objects that use a battery or small battery.
Going into a little more detail about the characteristics of this product, it should be noted that the peak data rate is fairly complex to determine, since it depends on the bandwidth used, which in turn depends on the region of the globe where the access point is located. It is possible to use a 2 MHz, 4 MHz, 8 MHz or 16 MHz channel and, depending on the user’s distance from the antenna, the peak data rate varies from 0.65 Mbit/s to 234 Mbit/s. The throughput can be increased to 347 Mbit/s when four parallel streams can be received simultaneously, instead of the current best-case scenario of three.
Wi-Fi Halow: the new technology to meet the IoT challenge?
To regulate traffic and prevent too many objects transmitting at the same time, a RAW (Restricted Access Window) can be used to create groups that are only allowed to transmit over certain time slots. This reduces contention between stations and avoids too many collisions in the CSMA/CA access technique.
This first mechanism is complemented by a second mechanism that enables both energy savings and additional traffic regulation. This mechanism, known as TWT (Target Wake Time), determines a set of time periods during which the object has the right to access the access point. These periods, which can be very far apart, allow the object to be put on standby while waiting for its next transmission period. To complete the range of ways of reducing the number of simultaneous accesses, sectorisation can be achieved using directional antennas. This partitioning avoids collisions between objects in different sectors.
