Wi-Fi and 5G 145
may or may not be contiguous – that is, they may belong to television
channels that are directly beside one another or that are separated by
active television channels.
A channel contains 64 bearers. Four channels may be selected,
each operating at 6, 7 or 8 MHz. In the latter two cases, as the data
rate per channel reaches 26.7 Mbps and given that, as with IEEE
802.11ac, we can have at least four directions in SDMA, the
maximum base rate is 568.9 Mbps, with 8 MHz channels.
The bearer access technique is the same as with normal Wi-Fi.
Service classes using an EDCA (Enhanced Distributed Channel
Access) technique from IEEE 802.11e are available, and correspond to
the four classes Background, Best-Effort, Video and Voice. A fifth,
even higher, priority is added for spectrum-monitoring, to determine
which channels could potentially be used.
6.6. IEEE 802.11ah
The IEEE is working on a new standard, apt for the connection of
“things” – i.e. sensors or other small devices with low consumption
and often minimal cost. This solution works in the non-licensed bands
available below 1 GHz. The technique should enable us to connect a
large number of things with low consumption. The sharing of the
transmissions takes place in classic Wi-Fi mode, but with a much
lower data rate and a much greater range, of up to 1 km. The things
are grouped into clearly-defined sets so as to avoid too high a number
of simultaneous accesses and so as not to lose too much in contention
in CSMA/CD mode. In addition, IEEE 802.11h involves the use of
classic techniques in the world of Ethernet to put stations on standby
and reawaken them.
IEEE 802.11h introduces the function of relay, whereby certain
things can connect through the relay, which decreases competition by
limiting the number of objects attempting to transmit simultaneously.
Relay increases the geographic scope of the things that can be
connected and, at the same time, saves energy by having tasks
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may or may not be contiguous – that is, they may belong to television
channels that are directly beside one another or that are separated by
active television channels.
A channel contains 64 bearers. Four channels may be selected,
each operating at 6, 7 or 8 MHz. In the latter two cases, as the data
rate per channel reaches 26.7 Mbps and given that, as with IEEE
802.11ac, we can have at least four directions in SDMA, the
maximum base rate is 568.9 Mbps, with 8 MHz channels.
The bearer access technique is the same as with normal Wi-Fi.
Service classes using an EDCA (Enhanced Distributed Channel
Access) technique from IEEE 802.11e are available, and correspond to
the four classes Background, Best-Effort, Video and Voice. A fifth,
even higher, priority is added for spectrum-monitoring, to determine
which channels could potentially be used.
6.6. IEEE 802.11ah
The IEEE is working on a new standard, apt for the connection of
“things” – i.e. sensors or other small devices with low consumption
and often minimal cost. This solution works in the non-licensed bands
available below 1 GHz. The technique should enable us to connect a
large number of things with low consumption. The sharing of the
transmissions takes place in classic Wi-Fi mode, but with a much
lower data rate and a much greater range, of up to 1 km. The things
are grouped into clearly-defined sets so as to avoid too high a number
of simultaneous accesses and so as not to lose too much in contention
in CSMA/CD mode. In addition, IEEE 802.11h involves the use of
classic techniques in the world of Ethernet to put stations on standby
and reawaken them.
IEEE 802.11h introduces the function of relay, whereby certain
things can connect through the relay, which decreases competition by
limiting the number of objects attempting to transmit simultaneously.
Relay increases the geographic scope of the things that can be
connected and, at the same time, saves energy by having tasks
www.it-ebooks.info