Reconfigurable intelligent surface assisted communication
Example embodiments of the present disclosure relate to reconfigurable intelligent surfaces (RIS) assisted communication. For example, RIS assisted blockage avoidance for low power internet of things (IoT) devices. An apparatus performs communication with a network device via a RIS, using at least one of a first channel or a second channel, wherein the first channel is for a transmission to the RIS and the second channel is for a reception from the RIS. In this way, it is possible to help reconnecting an IoT device with the network that has lost its connection with a gNB by using an RIS. It is also provided a low-cost and low-power connectivity solution for low-power IoT devices.
1 . An apparatus comprising:
at least one processor; and
at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:
perform communication with a network device exclusively via a reconfigurable intelligent surface (RIS) based on an absence of a direct communication link between the apparatus and the network device, using at least one of a first channel or a second channel wherein the apparatus is a low-power Internet of Things (IoT) device configured to operate with energy below 100 micro-watts and subject to intermittent connectivity, wherein the first channel is a UE assistance channel (UEAC) dedicated to communication between the apparatus and the RIS and is used for transmission to the RIS, and the second channel is used for reception from the RIS;
detect a blockage of signals from the network device based on a failure to receive a response within a predetermined blockage threshold time;
transmit, via the first channel to the RIS, a blockage indication comprising a preamble, a message A (msgA), and an identifier of the apparatus;
receive, from the RIS via the second channel, an acknowledgment indicating that the apparatus is connected to the RIS;
transmit, to the RIS via the first channel, a reference signal having a duration determined based on received signal strength from the RIS, and
receive, from the RIS via the second channel, a phase reconfiguration completion message indicating that the RIS has adjusted phase shifts of its elements to establish a reflected communication path between the apparatus and the network device, wherein the RIS includes a plurality of passive reflecting elements and a subset of active elements allocated specifically for the UE assistance channel, and wherein the apparatus thereafter performs uplink data transmission to the network device through the RIS using the reflected communication path.
2 . The apparatus of claim 1 , wherein the reference signal transmitted to the reconfigurable intelligent surface is repeated or extended in duration in response to a determination that a received signal strength of a signal from the reconfigurable intelligent surface is below a threshold.
3 . The apparatus of claim 2 , wherein the blockage is detected based on expiration of a timer corresponding to a blockage threshold time during which no response is received from the network device following at least one access attempt or scheduling request.
4 . The apparatus of claim 3 , wherein the reconfigurable intelligent surface comprises a plurality of passive reflecting elements and a plurality of active elements, and wherein a subset of the active elements is exclusively allocated for the UE assistance channel while remaining elements are allocated for communication with the network device.
5 . The apparatus of claim 4 , wherein the reference signal transmitted to the reconfigurable intelligent surface is configured to enable the reconfigurable intelligent surface to determine at least one of an angle of arrival (AoA) or a time of arrival (ToA) for forwarding to the network device.
6 . The apparatus of claim 5 , wherein the apparatus is further caused to receive a phase reconfiguration indication signal from the reconfigurable intelligent surface that is transmitted over a range of angles centered around a last known location of the apparatus prior to transmission of the reference signal.
7 . The apparatus of claim 6 , wherein the reconfigurable intelligent surface is configured to operate in a sensing mode using active elements to measure the reference signal and to subsequently switch to a reflecting mode in which the active elements are configured as passive elements to redirect signals toward the network device.
8 . A method comprising:
perform communication with a network device exclusively via a reconfigurable intelligent surface (RIS) based on an absence of a direct communication link between the apparatus and the network device, using at least one of a first channel or a second channel, wherein the apparatus is a low-power Internet of Things (IoT) device configured to operate with energy below 100 micro-watts and subject to intermittent connectivity, wherein the first channel is a UE assistance channel (UEAC) dedicated to communication between the apparatus and the RIS and is used for transmission to the RIS, and the second channel is used for reception from the RIS;
detect a blockage of signals from the network device based on a failure to receive a response within a predetermined blockage threshold time;
transmit, via the first channel to the RIS, a blockage indication comprising a preamble, a message A (msgA), and an identifier of the apparatus;
receive, from the RIS via the second channel, an acknowledgment indicating that the apparatus is connected to the RIS;
transmit, to the RIS via the first channel, a reference signal having a duration determined based on received signal strength from the RIS, and
receive, from the RIS via the second channel, a phase reconfiguration completion message indicating that the RIS has adjusted phase shifts of its elements to establish a reflected communication path between the apparatus and the network device, wherein the RIS includes a plurality of passive reflecting elements and a subset of active elements allocated specifically for the UE assistance channel, and wherein the apparatus thereafter performs uplink data transmission to the network device through the RIS using the reflected communication path.