Wireless telecommunications apparatus and methods
A first network access node for use with a handover procedure for a terminal device involving the first network access node and a second network access node. The first network access is configured to receive a block of uplink data from the terminal device and establish whether the block of data has been ciphered by the terminal device using a cipher key corresponding to a first cipher key or to a second cipher key. In response to establishing the block of data has been ciphered using a cipher key corresponding to the first cipher key, decipher the block of data using the first cipher key. In response to establishing the block of data has been ciphered using a cipher key corresponding to the second cipher key, forward the block of data to the second network access node.
1. A first network access node configured for use in a wireless telecommunications system comprising the first network access node, a second network access node and a terminal device, wherein the first network access node comprises controller circuitry and transceiver circuitry configured to operate together such that the first network access node is operable to:
receive a block of uplink data from the terminal device;
establish whether the block of data was ciphered by the terminal device using a cipher key corresponding to a first cipher key associated with the first network access node or corresponding to a second cipher key associated with the second network access node, wherein the first network access node is configured to receive a block of uplink data from the terminal device on grant-free radio resources;
in response to establishing the block of data has been ciphered using a cipher key corresponding to the first cipher key, decipher the block of data using the first cipher key; and
in response to establishing the block of data has been ciphered using a cipher key corresponding to the second cipher key, forward the block of data to the second network access node.
2. The first network access node of claim 1 , wherein the first network access node is configured to establish whether the block of data was ciphered by the terminal device using a cipher key corresponding to the first cipher key or the second cipher key based on an indication received from the terminal device.
3. The first network access node of claim 2 , wherein the indication received from the terminal device comprises an entry in a header for the data block.
4. The first network access node of claim 2 , wherein the indication received from the terminal device comprises an end marker transmitted by the terminal device to indicate when the terminal switches from ciphering uplink data using a cipher key corresponding to the second cipher key to the first cipher key.
5. The first network access node of claim 1 , wherein the first network access node is configured to establish whether the block of data was ciphered by the terminal device using a cipher key corresponding to the first cipher key or the second cipher key based on an attempt to decipher the block of data using the first cipher key.
6. The first network access node of claim 1 , wherein first network access node comprises a target network access node for a handover procedure for the terminal device involving the first network access node and the second network access node.
7. The first network access node of claim 1 , wherein first network access node comprises a source network access node for a handover procedure for the terminal device involving the first network access node and the second network access node.
8. The first network access node of claim 1 , wherein in response to establishing the block of data has been ciphered using a cipher key corresponding to the first cipher key and deciphering the block of data using the first cipher key, the first network access node is further configured to forward the deciphered block of data to a core network part of the wireless telecommunications system.
9. The first network access node of claim 1 , wherein in response to establishing the block of data has been ciphered using a cipher key corresponding to the second cipher key and forwarding the block of data to the second network access node, the first network access node is further configured to receive the deciphered block of data back from the second network access node after the second network access node has deciphered the block of data using the second cipher key.
10. The first network access node of claim 1 , wherein the first network access node is further configured to forward the deciphered block of data received from the second network access node to a core network part of the wireless telecommunications system.
11. A terminal device configured for use in a wireless telecommunications system comprising the terminal device, a first network access node and a second network access node, wherein the terminal device comprises controller circuitry and transceiver circuitry configured to operate together such that the terminal device is operable to:
transmit a block of uplink data to the first network access node, wherein the block of data is ciphered by the terminal device using a cipher key corresponding to a second cipher key associated with the second network access node rather than a cipher key corresponding to a first cipher key associated with the first network access node, wherein the terminal device is configured to transmit an indication of the cipher key used to encipher the data in a header for the data block; and
subsequently transmit to the first network access node an indication the terminal device will not send further data ciphered with a cipher key corresponding to the second cipher key.
12. The terminal device of claim 11 , wherein the terminal device is configured to transmit the indication the terminal device will not send further data ciphered with a cipher key corresponding to the second cipher key in response to achieving layer 2 synchronisation with the first network access node.
13. The terminal device of claim 11 , wherein the indication of the cipher key used to encipher the data in a header for the data block comprises a plurality of bits for indicating more than two cipher keys respectively associated with more than two network access nodes.
14. A first network access node configured for use in a wireless telecommunications system comprising the first network access node, a second network access node and a terminal device, wherein the first network access node comprises controller circuitry and transceiver circuitry configured to operate together such that the first network access node is operable to:
receive a block of uplink data from the terminal device;
establish whether the block of data was ciphered by the terminal device using a cipher key corresponding to a first cipher key associated with the first network access node or corresponding to a second cipher key associated with the second network access node, wherein:
the first network access node comprises a target network access node for a handover procedure for the terminal device involving the first network access node and the second network access node, or
the first network access node comprises a source network access node for a handover procedure for the terminal device involving the first network access node and the second network access node;
in response to establishing the block of data has been ciphered using a cipher key corresponding to the first cipher key, decipher the block of data using the first cipher key; and
in response to establishing the block of data has been ciphered using a cipher key corresponding to the second cipher key, forward the block of data to the second network access node.