Receiving segments of system information block message

1 . A method comprising:

receiving, by a wireless device from a wireless network, one or more segments of system information block type 12 (SIB12) message, wherein the SIB12 message comprises a sidelink configuration and a system information block tag;

determining, by the wireless device, at least one hash value based on a last successfully received segment, wherein the at least one hash value is determined using the system information block tag and a segment number of a corresponding segment as inputs to a hash function;

transmitting, by the wireless device to the wireless network, a system information request comprising information indicating the SIB12 system information block type and a lastSegmentNumber identifying the last successfully received segment, and the determined at least one hash value,

wherein the wireless device transmits the system information based on:

a change in a wireless connection between the wireless device and the wireless network, wherein the change in the wireless connection comprises a cell reselection or a cell selection; and

a determination by the wireless device of at least one missing segment of the SIB12 message;

in response to the transmitted system information request, receiving, by the wireless device, one or more further segments corresponding to the at least one missing segment of the SIB12 message; and

assembling, by the wireless device, the SIB12 message by combining the received one or more further segments with the one or more segments that were received prior to transmitting the system information request.

2 . The method according to claim 1 , wherein the wireless device hashes each of the received one or more segments using the system information block tag and a segment number of a respective one of the received one or more segments.

3 . The method according to claim 2 , wherein the hash function is selected from a group consisting of MD5, SHA1, SHA256, and SHA512.

4 . The method according to claim 3 , further comprising:

in response to a determination by the wireless network that the at least one hash value is valid, receiving, by the wireless device, one or more subsequent segments of the at least one system information block message,

wherein a first of the one or more subsequent segments has a segment number greater than a last segment received prior to transmitting the system information request; and

in response to a determination by the wireless network that the at least one hash value is not valid, receiving, by the wireless device, a first segment of the at least one system information block message having a segment number of zero.

5 . The method according to claim 1 , wherein the system information request further comprises an information element identifying the hash function used by the wireless device to determine the at least one hash value.

6 . The method according to claim 1 , wherein the change of the wireless connection is triggered by a radio link condition deterioration (RLCD) and comprises performing a Radio Resource Control (RRC) reestablishment.

7 . A method comprising:

determining, by a wireless network, one or more hash values based on one or more segments of at least one system information block 12 (SIB12) message,

wherein the at least one SIB12 message comprises a sidelink configuration and a system information block tag that is determined independently for a cell of the wireless network or based on an exchange of system information block tag information between cells of the wireless network, and

wherein each of the one or more hash values is determined using the system information block tag and a segment number of each of the one or more segments;

receiving, by the wireless network from a wireless device in connection with a cell re-selection, a system information request comprising information identifying at least one system information block message segment received by the wireless device and at least one hash value determined based on the at least one system information block message segment,

wherein the at least one hash value comprises a hash value of a last system information block message segment received by the wireless device or a digest of hash values of a plurality of system information block message segments received by the wireless device;

determining, by the wireless network, at least one non-received segment of the at least one SIB12 message by:

performing a validity check by comparing the at least one hash value in the received system information request with a corresponding hash value from the one or more hash values determined by the wireless network; and

based on the validity check indicating a match, identifying the at least one non-received segment as one or more segments of the at least one SIB12 message having segment numbers greater than a segment number of the last system information block message segment identified in the system information request; and

transmitting, by the wireless network to the wireless device over a changed wireless connection established after the cell re-selection, the determined at least one non-received segment.

8 . An apparatus comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, causes the apparatus to perform:

receiving, from a wireless network, one or more segments of at least one system information block 12 (SIB12) message, wherein the SIB12 message comprises a sidelink configuration and a system information block tag;

determining at least one hash value based on a last successfully received segment, wherein each of the at least one hash value is determined using the system information block tag and a segment number of a respective segment as inputs to a hash function;

transmitting, to the wireless network, a system information request comprising information indicating the SIB12 system information block type and a lastSegmentNumber identifying the last successfully received segment, and the determined at least one hash value,

wherein the system information request is transmitted based on:

a change of a wireless connection between the wireless device and the wireless network, wherein the change of the wireless connection comprises a cell reselection or a cell selection; and

a determination by the wireless device of at least one missing segment of the at least SIB12 message;

in response to the transmitted system information request, receiving, by the wireless device, one or more further segments corresponding to the at least one missing segment of the at least one SIB12 message; and

assembling, by the wireless device, the at least one SIB12 message by combining the received one or more further segments with the one or more segments that were received prior to transmitting the system information request without discarding the previously received segments.

9 . An apparatus comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, causes the apparatus to perform:

determining one or more hash values based on one or more segments of at least one system information block 12 (SIB12) message,

wherein the at least one SIB12 message comprises a sidelink configuration and a system information block tag that is determined independently for a cell of the wireless network or based on an exchange of system information block tag information between cells of the wireless network, and

wherein each of the one or more hash values is determined using the system information block tag and a segment number of each of the one or more segments;

receiving, from a wireless device, in connection with a cell re-selection, a system information request comprising information identifying at least one system information block message segment received by the wireless device and at least one hash value determined based on the at least one system information block message segment,

wherein the at least one hash value comprises a hash value of a last system information block message segment received by the wireless device or a digest of hash values of a plurality of system information block message segments received by the wireless device;

determining at least one non-received segment of the at least one SIB12 message by:

performing a validity check by comparing the at least one hash value in the received system information request with a corresponding hash value from the one or more hash values determined by the wireless network; and

based on the validity check indicating a match, identifying the at least one non-received segment as one or more segments of the at least one SIB12 message having segment numbers greater than a segment number of the last system information block message segment identified in the system information request; and

transmitting to the wireless device, over a changed wireless connection established after the cell re-selection, the determined at least one non-received segment.