Short message transmission and handover procedures
The present invention relates to an improved method for handover of a mobile node from E-UTRAN to UTRAN in a scenario where SMS is the only service of the mobile node. The improved handover method allows saving radio resources by establishing the signalling connection for SMS exchange in the target network, and avoiding the data connection in the target network, since it is not used. The MME takes the decision to establish or not the data connection in the target UTRAN, and accordingly instructs the SGSN and UE to set the corresponding PDP contexts for the data connection to a “preserved” state, so as to avoid the establishment of same. Embodiments further relate to improved SMS delivery for IDLE mode UEs that activate ISR so as to avoid the involvement of the MSC server. Instead, packet-switched domain nodes are to be involved only.
1. A method for transmitting downlink small data packets to a user equipment subscribed to a mobile communication network comprising a base station, the method comprising the steps of:
triggering the user equipment by a connectivity-related network entity to establish connectivity with the mobile communication network via the control plane only and not via user plane,
establishing by the user equipment and the connectivity-related network entity control plane connectivity for the user equipment, in response to the triggering,
transmitting the downlink small data packets to the user equipment using the established control plane connectivity, not using user plane connectivity,
starting by the user equipment a control-plane establishment timer when initiating the establishing of the control plane connectivity, in response to the triggering, and
stopping the control-plane establishment timer, upon establishing the control plane connectivity with the mobile communication network.
2. The method according to claim 1 , wherein when the user equipment is in an IDLE state, the triggering includes transmitting to the user equipment a paging message comprising a control-plane-only indication, and the connectivity-related network entity is a mobility management entity of the user equipment, or when the user equipment is in a DEREGISTERED state, the triggering includes transmitting to the user equipment a device trigger message comprising a control-plane-only indication, and the connectivity-related network entity is a mobility management entity.
3. The method according to claim 1 , wherein the downlink small data packets are transmitted to the user equipment using non-access stratum messages of the control plane.
4. The method according to claim 1 , wherein the downlink small data packets are received in the connectivity-related network entity, and are transmitted from the connectivity-related network entity to the base station using signaling messages, and are transmitted from the base station to the user equipment using RRC, Radio Resource Control, messages.
5. The method according to claim 1 further comprising the step of:
determining by the connectivity-related network entity to trigger the user equipment for control plane connectivity only, based on the time point of the connectivity establishment, and/or on the interface from which the connectivity-related network entity receives a trigger to trigger the user equipment.
6. The method according to claim 1 , wherein in case the downlink small data packets are received by the connectivity-related network entity, the triggering by the connectivity-related network entity is triggered by receiving the downlink small data packets, or
in case the downlink small data packets are received by a gateway, the triggering by the connectivity-related network entity is triggered by receiving a connection initiation message from the gateway, the connection initiation message including information on the downlink small data packets.
7. The method according to claim 1 , wherein in case the downlink small data packets are received by a gateway, the downlink small data packets are transmitted from the gateway to the connectivity-related network entity using control plane signaling.
8. The method according to claim 1 , further comprising the steps of:
estimating by the user equipment characteristics of uplink data to be transmitted in response to the downlink small data packets, in response to the triggering,
transmitting by the user equipment the estimated characteristics of the uplink data to the connectivity-related network entity,
deciding by the connectivity-related network entity on whether to establish data bearers, based on the received characteristics of the uplink data, and
in case the connectivity-related network entity decides to establish data bearers, transmitting downlink small data packets to the user equipment using the established data bearers, and transmitting the uplink data from the user equipment using the established data bearers, and
in case the connectivity-related network entity decides not to establish data bearers, transmitting downlink small data packets to the user equipment using the established control plane connectivity.
9. The method according to claim 8 , wherein the decision by the connectivity-related network entity is further based on limitation parameters related to the processing of uplink data received in the connectivity-related network entity.
10. The method according to claim 8 wherein in case the connectivity-related network entity decides to not establish data bearers, the method further comprising the steps of:
determining by the connectivity-related network entity limitation parameters related to the processing of uplink data received in the connectivity-related network entity,
transmitting by the connectivity-related network entity the determined limitation parameters to the user equipment,
determining by the user equipment the uplink data to be transmitted, based on the received downlink small data packets,
deciding by the user equipment on whether to establish data bearers to transmit the uplink data, depending on the received limitation parameters and based on the determined uplink data to be transmitted, and
in case the user equipment decides to establish data bearers, transmitting the uplink data using the established data bearers, and transmitting downlink small data packets using the established data bearers,
in case the user equipment decides not to establish data bearers, transmitting the uplink data using the established control-plane connectivity.
11. The method according to claim 8 , wherein the characteristics of the uplink data includes information on the amount and/or periodicity of the uplink data and/or an indication on whether the uplink data is small or large.
12. A user equipment for receiving downlink small data packets, the user equipment being subscribed to a mobile communication network comprising a base station, the user equipment comprising:
a receiver configured to receive a trigger message from a connectivity-related network entity to establish connectivity with the mobile communication network via the control plane only and not via user plane,
a processor, a transmitter and the receiver configured to establish control plane connectivity with the connectivity-related network entity, in response to the trigger message,
the receiver is further configured to receive the downlink small data packets using the established control plane connectivity not using user plane connectivity,
wherein the processor is further configured to start a control-plane establishment timer when initiating the establishing of the control plane connectivity, and to stop the control-plane establishment timer, upon establishing control plane connectivity with the mobile communication network.
13. The user equipment according to claim 12 , wherein the receiver is configured to receive the downlink small data packets from the base station using RRC, Radio Resource Control, messages.
14. The user equipment according to claim 12 , wherein when the user equipment is in an IDLE state, the receiver is configured to receive a paging message as trigger message.
15. The user equipment according to claim 14 , wherein a processor of the user equipment is configured to estimate characteristics of uplink data to be transmitted in response to the downlink small data packets, in response to receiving the trigger message,
a transmitter of the user equipment is configured to transmit the estimated characteristics of the uplink data to the connectivity-related network entity, such that the connectivity-related network entity decides on whether to establish data bearers, based on the transmitted characteristics of the uplink data,
in case the connectivity-related network entity decides to establish data bearers, the receiver, transmitter and processor are configured to establish data bearers,
the receiver is configured to receive downlink small data packets using the established data bearer, and
the transmitter is configured to transmit the uplink data using the established data bearer.
16. The user equipment according to claim 15 , wherein in case the connectivity-related network entity decides to not establish data bearers, the receiver is configured to receive limitation parameters from the connectivity-related network entity, related to the processing of uplink data received in the connectivity-related network entity,
the processor is configured to determine the uplink data to be transmitted, based on the received downlink small data packets,
the processor further configured to decide whether to establish data bearers to transmit the uplink data, depending on the received limitation parameters and based on the determined uplink data to be transmitted,
in case the processor decides to establish data bearer, the transmitter, receiver, processor being configured to establish data bearer, and the transmitter configured to transmit the uplink data using the established data bearer, and the receiver configured to receive downlink small data packets using the established data bearer.
17. A connectivity-related network entity for transmitting downlink small data packets to a user equipment subscribed to a mobile communication network comprising a base station, the connectivity-related network entity comprising:
a transmitter configured to transmit a trigger message to the user equipment to establish connectivity with the mobile communication network via control plane only and not via user plane,
a processor, receiver and the transmitter configured to establish control plane connectivity for the user equipment,
the transmitter configured to transmit the downlink small data packets to the user equipment using the established control plane connectivity, not using user plane connectivity,
wherein the processor is further configured to start a control-plane establishment timer when initiating the establishing of the control plane connectivity, and to stop the control-plane establishment timer, upon establishing control plane connectivity with the mobile communication network.
18. The connectivity-related network entity according to claim 17 , wherein when the user equipment is in an IDLE state, the transmitter is configured to transmit a paging message as the trigger message, comprising a control-plane only indication, and the connectivity-related network entity is a mobility management entity of the user equipment.