What are the two types of network access used in IEEE 802.15.4 networks? Describe them.
What will be an ideal response?
There are two types of network access used in IEEE 802.15.4: Beacon-enabled networks in which the frames contain contention-based periods for network access and may contain contention-free periods called guaranteed time slots (GTSs), which are used for data transfer to specific devices. Beacons are a special type of frame transmitted by the coordinator only in star topology networks, or transmitted by routers to other devices, on request from a child device.
In contention-based communications, all devices that want to transmit in a particular frequency use CSMA/CA to determine if the channel is busy. In beacon-enabled networks, the PAN coordinator can transmit control information about which devices are allowed to transmit and when, and it will also inform devices about timing periods in which all devices can contend for access to the medium. Beacons can be transmitted at fixed intervals, during which devices will normally wake-up and turn on their receivers so they can find out if any messages are being held for them at the coordinator or a parent device.
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What will be an ideal response?