Patent Description:
The following abbreviations are herewith defined, at least some of which are referred to within the following description: Third Generation Partnership Project ("3GPP"), Positive-Acknowledgment ("ACK"), Binary Phase Shift Keying ("BPSK"), Clear Channel Assessment ("CCA"), Cyclic Prefix ("CP"), Channel State Information ("CSI"), Common Search Space ("CSS"), Discrete Fourier Transform Spread ("DFTS"), Downlink Control Information ("DCI"), Downlink ("DL"), Downlink Pilot Time Slot ("DwPTS"), Enhanced Clear Channel Assessment ("eCCA"), Enhanced Mobile Broadband ("eMBB"), Evolved Node B ("eNB"), European Telecommunications Standards Institute ("ETSI"), Frame Based Equipment ("FBE"), Frequency Division Duplex ("FDD"), Frequency Division Multiple Access ("FDMA"), Guard Period ("GP"), Hybrid Automatic Repeat Request ("HARQ"), Internet-of-Things ("IoT"), Licensed Assisted Access ("LAA"), Load Based Equipment ("LBE"), Listen-Before-Talk ("LBT"), Long Term Evolution ("LTE"), Multiple Access ("MA"), Modulation Coding Scheme ("MCS"), Machine Type Communication ("MTC"), Multiple Input Multiple Output ("MIMO"), Multi User Shared Access ("MUSA"), Narrowband ("NB"), Negative-Acknowledgment ("NACK") or ("NAK"), Next Generation Node B ("gNB"), Non-Orthogonal Multiple Access ("NOMA"), Orthogonal Frequency Division Multiplexing ("OFDM"), Primary Cell ("PCell"), Physical Broadcast Channel ("PBCH"), Physical Downlink Control Channel ("PDCCH"), Physical Downlink Shared Channel ("PDSCH"), Pattern Division Multiple Access ("PDMA"), Physical Hybrid ARQ Indicator Channel ("PHICH"), Physical Random Access Channel ("PRACH"), Physical Resource Block ("PRB"), Physical Uplink Control Channel ("PUCCH"), Physical Uplink Shared Channel ("PUSCH"), Quality of Service ("QoS"), Quadrature Phase Shift Keying ("QPSK"), Radio Resource Control ("RRC"), Random Access Procedure ("RACH"), Random Access Response ("RAR"), Reference Signal ("RS"), Resource Spread Multiple Access ("RSMA"), Round Trip Time ("RTT"), Receive ("RX"), Sparse Code Multiple Access ("SCMA"), Scheduling Request ("SR"), Single Carrier Frequency Division Multiple Access ("SC-FDMA"), Secondary Cell ("SCell"), Shared Channel ("SCH"), Signal-to-Interference-Plus-Noise Ratio ("SINR"), System Information Block ("SIB"), Transport Block ("TB"), Transport Block Size ("TBS"), Time-Division Duplex ("TDD"), Time Division Multiplex ("TDM"), Transmission Time Interval ("TTI"), Transmit ("TX"), Uplink Control Information ("UCI"), User Entity/Equipment (Mobile Terminal) ("UE"), Uplink ("UL"), Universal Mobile Telecommunications System ("UMTS"), Uplink Pilot Time Slot ("UpPTS"), Ultra-reliability and Low-latency Communications ("URLLC"), and Worldwide Interoperability for Microwave Access ("WiMAX"). As used herein, "HARQ-ACK" may represent collectively the Positive Acknowledge ("ACK") and the Negative Acknowledge ("NAK"). ACK means that a TB is correctly received while NAK means a TB is erroneously received.

In certain wireless communications networks, some system information may be transmitted and/or received more often than is necessary. In certain configurations, to reduce the signaling load for providing system information, a minimum amount of system information may be used. The minimum system information ("SI") may contain basic information for initial access to the cell (e.g., subframe number, list of public land mobile networks ("PLMNs"), cell camping parameters, RACH parameters) that is broadcast periodically in a cell. In some configurations, the other non-minimum SI doesn't necessarily need to be periodically broadcast (e.g., it may be a network decision). In various configurations, the other SI may be provided on-demand to UEs (e.g., a UE may request it). Delivery of other SI may be done in a broadcast or unicast manner. In some configurations, the minimum SI may indicate whether a specific SIB is periodically broadcasted or provided on-demand. To obtain the one or more SIBs which are not periodically broadcasted and are provided on-demand, a UE may initiate an on-demand SI acquisition procedure (e.g., SI request). For an SI used by the UE, the UE may determine whether it is available in the cell and whether it is broadcast or not before it sends a request for it. The scheduling information for other SI may be provided by the minimum SI (e.g., an SIB type, validity information, periodicity, SI-window information, etc.).

In various configurations, multiple UEs may send a request for the same SI. The UEs may use power and resources to send the requests. Moreover, a gNB that receives multiple requests for the same SI may use excessive resources to receive and/or respond to the requests. Furthermore, there may be interference among the multiple requests sent by the UEs.

Claim <NUM> defines a first user equipment, claim <NUM> defines a method performed by a first user equipment, and claim <NUM> defines a processor for wireless communication.

Any non claimed embodiment or example is solely presented as information.

<FIG> depicts a wireless communication system <NUM> for determining a request for system information. In one embodiment, the wireless communication system <NUM> includes remote units <NUM> and base units <NUM>. Even though a specific number of remote units <NUM> and base units <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM> and base units <NUM> may be included in the wireless communication system <NUM>.

The base units <NUM> may be distributed over a geographic region. In certain embodiments, a base unit <NUM> may also be referred to as an access point, an access terminal, a base, a base station, a Node-B, an eNB, a gNB, a Home Node-B, a relay node, a device, or by any other terminology used in the art. The base units <NUM> are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding base units <NUM>.

In one implementation, the wireless communication system <NUM> is compliant with the LTE protocols standardized in 3GPP, wherein the base unit <NUM> transmits using an OFDM modulation scheme on the DL and the remote units <NUM> transmit on the UL using a SC-FDMA scheme or an OFDM scheme. More generally, however, the wireless communication system <NUM> may implement some other open or proprietary communication protocol, for example, WiMAX, among other protocols.

In one embodiment, a base unit <NUM> may receive information indicating a request for system information from the remote unit <NUM>. In certain embodiments, the base unit <NUM> may transmit the system information to the remote unit <NUM>.

In another embodiment, a remote unit <NUM> may determine whether system information used by the remote unit <NUM> is scheduled to be transmitted. The remote unit <NUM> may, in response to the system information not being scheduled to be transmitted, determine whether the system information is requested by a second remote unit. Accordingly, a remote unit <NUM> may be used for determining a request for system information.

<FIG> depicts an apparatus <NUM> that may be used for determining a request for system information. The apparatus <NUM> includes one embodiment of the remote unit <NUM>. Furthermore, the remote unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. In some embodiments, the input device <NUM> and the display <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit <NUM> may not include any input device <NUM> and/or display <NUM>. In various embodiments, the remote unit <NUM> may include one or more of the processor <NUM>, the memory <NUM>, the transmitter <NUM>, and the receiver <NUM>, and may not include the input device <NUM> and/or the display <NUM>.

In various embodiments, the processor <NUM> determines whether system information used by the remote unit <NUM> is scheduled to be transmitted. In certain embodiments, the processor <NUM> in response to the system information not being scheduled to be transmitted, determines whether the system information is requested by a second apparatus.

In some embodiments, the memory <NUM> stores data relating to system information.

The transmitter <NUM> is used to provide UL communication signals to the base unit <NUM> and the receiver <NUM> is used to receive DL communication signals from the base unit <NUM>. In various embodiments, the transmitter <NUM> may be used to transmit information indicating a request for system information.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for receiving and responding to requests for system information. The apparatus <NUM> includes one embodiment of the base unit <NUM>. Furthermore, the base unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. As may be appreciated, the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> may be substantially similar to the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> of the remote unit <NUM>, respectively.

In various embodiments, the receiver <NUM> is used to receive information from the remote unit <NUM> indicating a request for system information. In some embodiments, the transmitter <NUM> may be used to transmit system information to the remote unit <NUM>. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the base unit <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>.

<FIG> illustrates one embodiment of communications <NUM> for transmitting a request for system information. Specifically, communications <NUM> between a UE <NUM> and a gNB <NUM> are illustrated. The communications <NUM> may facilitate the UE <NUM> requesting on-demand SIBs using a RACH message <NUM> based approach.

In certain embodiments, the gNB <NUM> may transmit a periodic broadcast <NUM> to the UE <NUM>. The periodic broadcast <NUM> may include minimum SI used by the UE <NUM> for communication. In various embodiments, the UE <NUM> may transmit a PRACH preamble <NUM> to the gNB <NUM>. In some embodiments, in response to transmitting the PRACH preamble <NUM>, the gNB <NUM> may transmit an UL grant in a random access response <NUM>. After receiving the random access response <NUM>, the UE <NUM> may transmit a system information ("SI") request <NUM> to the gNB <NUM> that indicates on-demand SIBs requested by the UE <NUM>. The system information request <NUM> may be a random access message <NUM>. As may be appreciated, the on-demand SIBs may not be broadcast (e.g., transmitted) unless requested.

In certain embodiments, because message <NUM> is a UL-SCH transmission (e.g., medium access control ("MAC") protocol data unit ("PDU")) more information may be provided by the UE <NUM> within the message <NUM> than in a PRACH preamble. In one embodiment, the UE <NUM> includes a MAC control element ("CE") within the RACH message <NUM> to convey the SI request information. In such an embodiment, the MAC CE may contain a bitmap indicating the SI(s)/SIB(s) that the UE <NUM> wants to acquire. Moreover, the bitmap may have an entry for all on-demand SI(s)/SIB(s) (e.g., all SIBs not broadcast in the cell). Using the bitmap, the UE <NUM> may indicate (e.g., by setting the corresponding field/bit to a predefined value) which of the SI(s)/SIB(s) it wants to acquire. In certain embodiments, the UE <NUM> requests system information not only for the current cell, (e.g., cell UE is camped on/connected with) but also for neighboring cells. In one embodiment, the UE <NUM> includes information within the message <NUM> (e.g., SI request message) which indicates that the gNB <NUM> should provide to UE <NUM> all system information used in a predetermined area, covering one or multiple cells.

In various embodiments, the gNB <NUM> may include the requested SIB(s)/SI(s) in a RACH message <NUM> (e.g., RRC message). In various embodiments, the SIB(s)/SI(s) requested by the UE <NUM> may be broadcast (instead of sending them in message <NUM>). In such embodiments, the RACH message <NUM> may include the scheduling information which indicates the timing information for the broadcast of the requested SIB(s)/SI(s). Furthermore, in such embodiments, the UE <NUM> may not read minimum system information in order to acquire the timing information before receiving the broadcasted SIB(s)/SI(s).

In various embodiments, SIB(s)/SI(s) requested by the UE <NUM> may be partly provided by broadcast and partly within RACH message <NUM>. In one embodiment, the RACH message <NUM> may include information indicating which SI(s)/SIB(s) are provided by RACH message <NUM> and which SI(s)/SIB(s) are broadcast (e.g., the UE <NUM> monitors during the SI window associated with these SI(s)/SIB(s) for receiving the broadcast channel). In some embodiments, the RACH message <NUM> may indicate scheduling information for SI(s)/SIB(s). In such embodiments, the UE <NUM> may use the scheduling information provided by message <NUM>. In embodiments in which message <NUM> does not include scheduling information, the UE <NUM> may use scheduling information provided in the minimum SI to receive the SI(s)/SIB(s).

In one embodiment, the gNB <NUM> may send multiple RACH message <NUM> (e.g., to be provided SI(s)/SIB(s) may not fit within only one downlink transmission). In certain embodiments, an indication is contained within the RACH message <NUM> (e.g., SI feedback response) indicating whether the UE <NUM> should continue monitoring for further downlink transmissions (e.g., further RACH message <NUM> transmissions, monitor the same RNTI) for reception of further SI(s)/SIB(s) or whether UE may stop monitoring for further downlink transmissions (e.g., further RACH message <NUM> transmissions). In one embodiment, this indication is a boolean flag. In certain embodiments, the boolean flag may be set to mean that the gNB <NUM> may provide further SI(s)/SIB(s) directly in further downlink transmissions, and the boolean flag may be unset to mean that the gNB <NUM> may not provide further message <NUM> messages and thus the UE <NUM> may stop monitoring PDCCH for a corresponding RNTI. In various embodiments, the RACH message <NUM> may include information indicating whether the UE <NUM>, in response to receiving the RACH message, should initiate an RRC connection establishment procedure or an RRC connection resume procedure.

In some embodiments, the radio network temporary identifier ("RNTI") used for RACH message <NUM> transmission may indicate the on-demand SIB(s) which are either included in message <NUM> (e.g., RRC message) or being broadcast. In such embodiments, a certain number of RNTI(s) (e.g., from the cell RNTI ("C-RNTI") space) may be reserved and associated to a specific SIB or a combination of several SIB(s).

In certain embodiments described herein, the RACH procedure may be used for the sole purpose of requesting on-demand SI. However, in some embodiments, the UE <NUM> may establish an RRC connection and at the same request on-demand SI, or the UE <NUM> in an inactive state may transmit UL data and at the same time trigger an on-demand SI acquisition procedure. In such embodiments, which are just examples, the UE <NUM> may send the SI-request MAC CE and the RRC connection request message in RACH message <NUM>, or SI-request MAC CE and UL data and potentially some buffer status report ("BSR") MAC CE in RACH message <NUM>. In such embodiments, the gNB <NUM> may distinguish between the different cases (e.g., SI-request, SI-Request plus initial access, SI-request plus UL data) so that the gNB <NUM> may dimension the size of the UL grant accordingly. Accordingly, in some embodiments, PRACH preambles may be reserved for identification of the different cases.

<FIG> illustrates another embodiment of communications <NUM> for transmitting a request for system information. Specifically, communications <NUM> between a UE <NUM> and a gNB <NUM> are illustrated. The communications <NUM> may facilitate the UE <NUM> requesting on-demand SIBs using a RACH message <NUM> based approach.

In certain embodiments, the gNB <NUM> may transmit a periodic broadcast <NUM> to the UE <NUM>. The periodic broadcast <NUM> may include minimum SI used by the UE <NUM> for communication. In various embodiments, the UE <NUM> may transmit a PRACH preamble <NUM> to the gNB <NUM>. The PRACH preamble <NUM> indicates an SI request to the gNB <NUM> that indicates on-demand SIBs requested by the UE <NUM>. The PRACH preamble <NUM> may be a message <NUM>. As may be appreciated, the on-demand SIBs may not be broadcast (e.g., transmitted) unless requested.

In certain embodiments, the PRACH preamble <NUM> is resource specific to an SIB or set of SIBs which the UE <NUM> wants to obtain. In some embodiments, the PRACH preamble <NUM> that is resource specific to each SIB or set of SIBs are reserved and indicated in periodically broadcasted minimum SI. In certain embodiments, the UE <NUM> may request system information not only for the current cell, (e.g., cell UE is camped on/connected with) but also for neighboring cells. In one embodiment, a PRACH preamble <NUM> indicates that the gNB <NUM> should provide to UE <NUM> all system information used in a predetermined area, covering one or multiple cells.

In various embodiments, the UE <NUM> may receive a request to perform the random access procedure for a different purpose than for on-demand SI acquisition (e.g., initial access) while also being triggered to perform the SI acquisition. In such embodiments, the UE <NUM> may deprioritize the RACH procedure for SI request. For example, the UE <NUM> may first perform the initial access and then retrieve the system information by dedicated signaling (e.g., RRC signaling).

<FIG> is a schematic flow chart diagram illustrating one embodiment of a method <NUM> for determining a request for system information. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In certain embodiments, UEs may monitor the same random access RNTI ("RA-RNTI") to receive a random access response (RAR or Msg2) to check if its (a particular UE's) sent preamble was received by the network and therefore in RAR it may confirm if the corresponding SI(s)/SIB(s) would be subsequently transmitted by the network on an on-demand basis. In such embodiments, an RA-RNTI (or a group of such pre-known RNTIs) may be known to the UEs because of one of the following: the RA-RNTI (or a group of such pre-known RNTIs) is specified; the RA-RNTI (or a group of such pre-known RNTIs) is configured as part of SI (e.g., minimum SI may be available by broadcast from the network); and/or the RA-RNTI (or a group of such pre-known RNTIs) is calculated from a known set of parameters like time and frequency resources of the PRACH resource(s) used by the UE(s) to transmit their preamble (e.g., message <NUM>).

In some embodiments, one RA-RNTI may be sufficient to cater to all UEs requesting SI within a certain window; however, to cater to more than one overlapping window and/or for generalization, more than one RA-RNTI may be used.

In another embodiment, UEs that sent a message <NUM> (e.g., Msg3) may monitor the same C-RNTI (or a group of such pre-known C-RNTIs) to receive a message <NUM> (e.g., Msg4) and further check if its (a particular UE's) Msg3 for requesting particular SI(s)/ SIB(s) is received by the network and the request is accepted by the network. In some embodiments, a UE receives and analyzes Msg4 to check if the corresponding SI(s)/SIB(s) will be transmitted by the network on an on-demand basis. In certain embodiments, one C-RNTI (or a group of such pre-known C-RNTIs) may be known to the UEs because of one of the following: the C-RNTI (or a group of such pre-known RNTIs) is specified; the C-RNTI (or a group of such pre-known RNTIs) is configured as part of SI (e.g. a minimum SI may be available by broadcast from the network); the C-RNTI (or a group of such pre-known RNTIs) is calculated from a known set of parameters like time and frequency resources of the PRACH resource(s) used by the UE(s) to transmit their preamble (e.g., Msgl); and/or the C-RNTI (or a group of such pre-known RNTIs) is provided as part of RAR and the RAR is received using a RA-RNTI pre-known to the UE.

In various embodiments, only one C-RNTI may be sufficient to cater to all UEs requesting SI within a certain window; however, for generalization, more than one such C-RNTIs may be used.

In some embodiments, transmission of Msg1 (e.g., PRACH preamble) in a Msg1 based method may be unnecessary to obtain particular SI(s)/SIB(s). In various embodiments, transmission of Msg1 (e.g., PRACH preamble), reception of Msg2, and transmission of Msg3 in Msg3 based method may be unnecessary to obtain particular SI(s)/SIB(s).

Turning to the method <NUM>, the method <NUM> may include determining <NUM> whether all SIBs to be used by a remote unit <NUM> are broadcast by a base unit <NUM>. In response to all SIBs to be used by the remote unit <NUM> being broadcast, the method <NUM> acquires <NUM> SIBs using scheduling information that may be obtained from minimum SI, and the method <NUM> may end. In response to all SIBs to be used by the remote unit <NUM> not being broadcast, the method <NUM> determines <NUM> which SIBs are provided by the base unit <NUM> on an on-demand basis.

The method <NUM> then determines <NUM> whether a persistence check is required. The persistence check may be performed, in various embodiments, to avoid a situation in which there are too few remote units transmitting and too many remote units just listening to responses to on-demand requests made by other UEs. In one embodiment, the persistence check may be required to be performed as indicated by a base unit <NUM>. In response to the persistence check not being required, the method <NUM> may transmit <NUM> message <NUM> to request SI(s)/SIB(s) that are available on-demand. Transmitting <NUM> the message <NUM> as described herein may include choosing a preamble to transmit.

In certain embodiments, a network (e.g., base unit <NUM>) may configure multiple different preambles (e.g., Preamble <NUM> that indicates SIBs A and B, Preamble <NUM> that indicates SIBs C and D, Preamble <NUM> that indicates SIBs E and F, Preamble <NUM> that indicates SIBs G and H, and so forth). In one example, a remote unit <NUM> may choose a preamble to transmit by determining that it needs SIBs A, B, and H and then selecting a preamble that corresponds to at least a portion of the needed SIBs (e.g., Preamble <NUM>). After transmitting Preamble <NUM> to indicate SIBs A and B, the remote unit <NUM> may then check to see if SIBs A, B, and H are indicated to be provided. In response to none of A, B, and H being indicated to be provided, the remote unit <NUM> may again transmit Preamble <NUM> and check for an indication. In response to an indication that A and B are indicated as being provided, but not H, the remote unit <NUM> may proceed to acquire A and B and initiate Preamble <NUM> transmission in a similar manner as described above relating to Preamble <NUM>. In response to only H being indicated as being provided, the remote unit <NUM> may proceed to acquire H and again transmit Preamble <NUM>. In response to A, B, and H being indicated as being provided, the remote unit <NUM> may proceed to acquire A, B, and H.

In response to the persistence check being required, the method <NUM> performs the persistence check. The persistence check may be performed in one embodiment by comparing a UE generated decimal value between <NUM> and <NUM> (designated herein as 'r') against another decimal value (designated herein as 'p'). `p' may be specified or configured using a broadcast message (e.g., like minimum SI). The method <NUM> may determine <NUM> whether the persistence check passes. In one embodiment, the persistence check may pass if 'r' is smaller than or equal to 'p'. In another embodiment, the persistence check may pass if 'r' is greater than or equal to 'p'. In response to the persistence check passing, the remote unit <NUM> may transmit <NUM> message <NUM> to request SI(s)/SIB(s) that are available on-demand. By using the persistence check, the base unit <NUM> may control how many remote units initiate a RACH procedure. In certain embodiments, a specific value of 'p' could have a special meaning (e.g., 'p' = <NUM> could mean an automatic persistence check pass i.e., all remote units send message <NUM>, 'p' = <NUM> could mean an automatic persistence check fail i.e., no remote units send message <NUM>. For example, special values of 'p' may be used, due to congestion, to indicate that the network is already transmitting the required SI using broadcast, or in a time frame known to the remote unit <NUM>, or vice-versa.

In response to the persistence check not passing, the method <NUM> receives <NUM> RAR on a known RA-RNTI. The method <NUM> checks the RAR to determine <NUM> whether desired SI(s)/SIB(s) is indicated. As used herein, "desired SI(s)/SIB(s)" may mean the SIB(s)/SI(s) corresponding to transmitting <NUM> the message <NUM> (e.g., preamble) and/or preambles that may have been transmitted to receive other SIB(s)/SI(s).

In response to determining that the desired SI(s)/SIB(s) is not indicated, the method <NUM> returns to determining <NUM> whether a persistence check is required. In response to determining that the desired SI(s)/SIB(s) is indicated, the method <NUM> acquires <NUM> SIBs using scheduling information.

In certain embodiments, such as in a message <NUM> based solution, the following preambles may be used to make on-demand requests: Preamble <NUM> may indicate all SI A to H; Preamble <NUM> may indicate SI A and B; Preamble <NUM> may indicate SI C and D; Preamble <NUM> may indicate SI E and F; and Preamble <NUM> may indicate SI G and H.

In some embodiments, using a message <NUM> based method <NUM> some preamble transmissions from a remote unit <NUM> may not be necessary thereby saving the remote unit <NUM> power, reducing UL resources, reducing UL traffic, reducing UL collision, and so forth. This is facilitated because all remote units receive the RAR response (e.g., Msg2) using a particular (specified or configured) RA-RNTI and may check as part of RAR content (or alternatively DCI) if the particular remote unit's requested SI(s)/SIB(s) are listed therein. In certain embodiments, in RAR the base unit <NUM> may provide a list of SIs and SIBs (e.g., using a bitmap in which every bit or bitmap corresponds to a particular SI(s)/SIB(s), and this mapping is known to both the remote unit <NUM> and the base unit <NUM>, setting a bit may mean that the corresponding system information will be provided, an unset bit means the corresponding system information will not be provided, or vice-versa) that it intends to provide on an on-demand basis (e.g., broadcast for certain duration known to the remote units from minimum SI). Accordingly, a particular remote unit <NUM> does not need to actually transmit a corresponding preamble (e.g., Preamble <NUM>) to request SIs (e.g., C and D) as long as it can verify that SIs C and D are listed in RAR.

In certain embodiments, a base unit <NUM> includes just one MAC PDU containing just one MAC RAR including a bitmap of SIs and/or SIBs that it is going to provide on demand (based on all requests it received within a window). In such embodiments, only one RA-RNTI may be used.

In various embodiments, to be able to receive/check RAR, a remote unit <NUM> need not have transmitted the message <NUM> itself. In such embodiments, the remote unit <NUM> may listen for Msg2/RAR which the base unit <NUM> may have sent in response to Msg1 sent by other remote units. As set forth above, a persistence check may be used so that remote units that are not transmitting Msg1 but just listening for Msg2 do not just listen endlessly. The persistence check helps to avoid unnecessarily listening when no response (RAR) would actually come, or only responses (RARs) not containing its required SI(s)/SIB(s) in the list are received. In some embodiments, the amount of time that the remote unit <NUM> may perform just listening may be limited. In various embodiments, this limited time (e.g., duration, start time, end time, etc.) may be either remote unit implementation specific, specified, or configured (e.g., using a broadcast message like minimum SI).

In certain embodiments, a message <NUM> based solution may be similar to the message <NUM> based solution of method <NUM>, except that the C-RNTI used to scramble the cyclic redundancy code ("CRC") of PDCCH scheduling Msg4 may be known to all UEs (e.g., the C-RNTI(s) may be specified or configured using a broadcast message like minimum SI). In various embodiments, remote units that are just listening, receive only Msg4 on the C-RNTI and check the contents of Msg4 (or alternatively DCI) to determine if the particular remote unit's requested SI(s)/SIB(s) are listed therein. In Msg4, the base unit <NUM> may provide a list of SIs and SIBs (e.g., using a bitmap in which every bit or bitmap corresponds to a particular SI(s)/SIB(s), and this mapping is known to both the remote unit <NUM> and the base unit <NUM>, setting a bit may mean that the corresponding system information will be provided, an unset bit means the corresponding system information will not be provided, or vice-versa) that it intends to provide on an on-demand basis (e.g., broadcast for a certain duration known to the remote units from minimum SI). Accordingly, in such embodiments, it is not important that a remote unit <NUM> actually transmitted the Msg1 and Msg3 to request SIs as long as it can see that SIs that the remote unit <NUM> is interested in are listed in RAR. Certain embodiments of a message <NUM> based solution may include limiting a time that the remote unit <NUM> is just listening for Msg4 without transmitting and/or persistence checks as described herein.

In some embodiments, if a remote unit <NUM> determines that it will send multiple different preambles for different SI(s)/SIB(s) requests, the remote unit <NUM> may determine an order for sending the different preambles. In various embodiments, the remote unit may: send an SI-request for an SI in which the SI-window is the closest in time; prioritize transmission of a preamble which corresponds to an essential SIB (e.g., request corresponding SI first); prioritize transmission of a preamble which corresponds to SIB(s) which are required for a particular feature (e.g., like evolved multimedia broadcast multicast services ("eMBMS") reception in idle mode) activation; or some combination thereof.

<FIG> is a schematic flow chart diagram illustrating another embodiment of a method <NUM> for determining a request for system information. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

The method <NUM> may include determining <NUM>, at a first remote unit (e.g., remote unit <NUM>), whether system information used by the first remote unit is scheduled to be transmitted. The method <NUM> also includes, in response to the system information not being scheduled to be transmitted, determining <NUM> whether the system information is requested by a second remote unit (e.g., remote unit <NUM>).

In one embodiment, the method <NUM> includes, in response to the system information being scheduled to be transmitted, receiving the system information based on scheduling information for the system information. In a further embodiment, determining whether the system information is requested by the second remote unit includes monitoring messages for an indication that the system information is requested by the second remote unit. In certain embodiments, determining whether the system information is requested by the second remote unit includes checking a common radio network temporary identifier for an indication that the system information is requested by the second remote unit. In various embodiments, the method <NUM> includes, in response to the system information being requested by the second remote unit, receiving the system information in response to the system information being transmitted to the second remote unit. In some embodiments, the method <NUM> includes, in response to the system information not being requested by the second remote unit, transmitting a request for the system information.

In certain embodiments, transmitting a request for the system information includes determining whether the first remote unit is authorized to transmit the request prior to transmitting the request. In some embodiments, determining whether the first remote unit is authorized to transmit the request includes checking a parameter. In various embodiments, the method <NUM> includes, in response to the parameter passing a predetermined threshold, transmitting the request for system information, and, in response to the parameter not passing the predetermined threshold, not transmitting the request for system information.

In one embodiment, the method <NUM> includes receiving a response to the request for the system information. In certain embodiments, the response to the request for the system information is received as part of a random access response having a random access radio network temporary identifier. In some embodiments, the response to the request for the system information includes an indication identifying the system information. In various embodiments, transmitting the request for system information includes determining an order of requests in response to the request including multiple preambles. In certain embodiments, the order of requests includes transmitting a preamble of the multiple preambles first that corresponds to system information scheduled to be transmitted a closest in time, system information more important than other preambles of the multiple preambles, system information for a particular feature, or some combination thereof.

Claim 1:
A first user equipment (<NUM>) for wireless communication, comprising:
at least one memory (<NUM>); and
at least one processor (<NUM>) coupled with the at least one memory (<NUM>) and configured to cause the first user equipment (<NUM>) to:
determine whether system information used by the first user equipment is scheduled to be transmitted; characterized by the processor being further configured to cause the first user equipment to:
in response to the system information not being scheduled to be transmitted, determine whether the system information is requested by a second user equipment, by checking a common radio network temporary identifier for an indication that the system information is requested by the second user equipment; and
in response to the system information being requested by the second user equipment, receive the system information in response to the system information being transmitted to the second user equipment.