In addition to the class A structure of uplink followed by two downlink windows, class C further reduces latency on the downlink by keeping the receiver of the end-device open at all times that the device is not transmitting (half duplex). The latency is programmable up to 128 seconds to suit different applications, and the additional power consumption is low enough to still be valid for battery powered applications.Ĭlass C – Lowest latency, bi-directional end-devices: This provides the network the ability to send downlink communications with a deterministic latency, but at the expense of some additional power consumption in the end-device. In addition to the class A initiated receive windows, class B devices are synchronized to the network using periodic beacons, and open downlink ‘ping slots’ at scheduled times.
This makes class A the lowest power operating mode, while still allowing uplink communication at any time.īecause downlink communication must always follow an uplink transmission with a schedule defined by the end-device application, downlink communication must be buffered at the network server until the next uplink event.Ĭlass B – Bi-directional end-devices with deterministic downlink latency: The end-device is able to enter low-power sleep mode for as long as defined by its own application: there is no network requirement for periodic wake-ups. Each uplink transmission can be sent at any time and is followed by two short downlink windows, giving the opportunity for bi-directional communication, or network control commands if needed.
The default class which must be supported by all LoRaWAN end-devices, class A communication is always initiated by the end-device and is fully asynchronous.
While substantially reducing the feedback overhead, it is shown that the proposed scheduling algorithm performs closely to the opportunistic scheduling algorithm that requires instantaneous CSI feedback from all users.LoRaWAN has three different classes of end-point devices to address the different needs reflected in the wide range of applications:Ĭlass A – Lowest power, bi-directional end-devices: Simulation results demonstrate that the developed analytical framework provides a good approximation for a practical number of antennas. Using these ergodic rates, a joint user and mode selection algorithm is proposed, where only the scheduled users need to feed back instantaneous CSI. Utilizing the results of random matrix theory, an analytical framework is proposed to approximate the ergodic rate of each user with different number of data streams. Multimode transmission is applied that is able to adaptively adjust the number of data streams transmitted to each user. We propose a scheduling algorithm based only on the knowledge of the average SNR at each user from all the cooperating BSs, denoted as incomplete CSI. In such a network, obtaining perfect channel state information (CSI) of all users at the central unit to exploit opportunistic scheduling requires a substantial amount of feedback and backhaul signaling. We consider a cooperative multicell MIMO (a.k.a network MIMO) downlink system with multiantenna base stations (BSs), which are connected to a central unit and communicate with multiantenna users.
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