Patent Description:
Technical Specification 3GPP TR <NUM> v11. <NUM> describes coordinated multi-point operation (CoMP) for LTE physical layer aspects and discloses various techniques with the common aspect that there is a dynamic coordination and/or reception at the user terminal from multiple geographically separated or collocated base stations (called evolved NodeBs in LTE). One of these techniques is termed 'dynamic cell selection' wherein at a particular point in time data is transmitted only from a single transmission node and there is a process to dynamically select which of the transmission nodes transmits the data. For example, selecting a transmission node with the, at the particular point in time, best conditions on the wireless interface allows to increase the rate at which data packets may be delivered at the user device, compared to a single-point mode of operation. It is a drawback of these techniques that they require either a significant amount of control and coordination between base stations or, if this inter-base station control or coordination does not exist, that they may involve redundant transmissions to user terminals.

<NPL> relates to Coordinated multipoint (CoMP) and discloses a low complexity decoding method named Adaptive K-Best Sphere Decoder to serve high mobility cell edge user facing different varying frequency selective channels from multiple base stations.

It is a first object of the invention to provide a mobile communication system, in which the amount of control and coordination between base stations and the amount of redundant transmissions to user terminals is limited.

The invention is defined by a mobile communication system according to independent claim <NUM>.

The mobile communication system of the invention allows a user terminal to start receiving data segments from another base station whenever this is beneficial, e.g. when it is able to receive this other base station better and/or the other base station has a lower load than the base station it is currently receiving data segments from, while limiting the amount of control and coordination between base stations and the amount of redundant transmissions to user terminals when doing so. If the first base station and the second base station would transmit the first data set in the same sequence, coordination between the base stations would be required every time the user terminal would switch from an old base station to a new base station. Without such coordination, the new base station would transmit data to the user terminal that the user terminal might have already received from the old base station. By configuring the first base station and the second base station such that the sequence in which the first data set is transmitted by the respective base stations is inverse, the new base station can resume transmission at the point it previously left off with limited redundant transmissions. Coordination/synchronization between base stations is only needed when the user terminal has received all data segments of a data set.

The mobile communication system <NUM> of the invention comprises a first base station <NUM> and a second base station <NUM>, see <FIG>. The first base station <NUM> is configured to transmit at least part of a first data set of data segments arranged in a first sequence to a user terminal <NUM>. The second base station <NUM> is configured to transmit at least part of the first data set of data segments arranged in a second sequence to the user terminal <NUM>. The second sequence of the first data set is an inverse of the first sequence of the first data set.

The mobile communication system <NUM> may be, may comprise or may be part of an GPRS, UMTS, CDMA or LTE communication network, for example. In the embodiment shown in <FIG>, the mobile communication system <NUM> is an LTE communication network in which a Serving Gateway (S-GW) <NUM> is present. The Serving Gateway <NUM> is typically connected to a PDN Gateway (P-GW). The invention can be used in conjunction with LTE's Coordinated multipoint (CoMP) transmission techniques.

In the embodiment shown in <FIG>, the first base station <NUM> comprises a data receiver <NUM>, data transmitters <NUM> and <NUM> and a processor <NUM>. The processor <NUM> is configured to use the data transmitter <NUM> to transmit a data set comprising a plurality of data segments to a user terminal <NUM>, to use the data receiver <NUM> to receive from the user terminal <NUM> a data segment acknowledgment acknowledging receipt of a first one of the plurality of data segments, to use the data receiver <NUM> to receive from the user terminal <NUM> a data set acknowledgement acknowledging receipt of the data set and to use the data transmitter <NUM> to inform the second base station <NUM> of the data set acknowledgment while not informing the second base station <NUM> of the data segment acknowledgement. The first base station <NUM> further comprises a data receiver <NUM> for receiving data from the Serving Gateway <NUM>.

The second base station <NUM> comprises a data receiver <NUM>, data transmitters <NUM> and <NUM> and a processor <NUM>. The processor <NUM> is configured to use the data transmitter <NUM> to transmit a data set comprising a plurality of data segments to a user terminal <NUM>, to use the data receiver <NUM> to receive from the user terminal <NUM> a data segment acknowledgment acknowledging receipt of a first one of the plurality of data segments, to use the data receiver <NUM> to receive from the user terminal <NUM> a data set acknowledgement acknowledging receipt of the data set and to use the data transmitter <NUM> to inform the first base station <NUM> of the data set acknowledgment while not informing the first base station <NUM> of the data segment acknowledgement. The second base station <NUM> further comprises a data receiver <NUM> for receiving data from the Serving Gateway <NUM>.

When the user terminal <NUM> does not inform both the first base station <NUM> and the second base station <NUM> of the data set acknowledgment, whichever base station receives the data set acknowledgement from the user terminal <NUM> informs the other base station(s). This communication may be direct between base stations, but may also be routed via the Serving Gateway <NUM>, for example.

The user terminal <NUM> comprises a data receiver <NUM>, a data transmitter <NUM>, and a processor <NUM>. The processor <NUM> is configured to use the data receiver <NUM> to receive a first one of a plurality of data segments of a data set from the first base station <NUM>, to use the data transmitter <NUM> to transmit a data segment acknowledgment acknowledging receipt of the first one of the plurality of data segments to the first base station <NUM>, to use the data receiver <NUM> to receive a last one of the plurality of data segments of the data set from the first base station <NUM>, to use the data transmitter <NUM> to transmit a data set acknowledgement acknowledging receipt of the data set to the first base station <NUM> and to the second base station <NUM> and not to transmit the data segment acknowledgment to the second base station <NUM>.

In an embodiment, the processor <NUM> of the user terminal <NUM> is further configured to use the data receiver <NUM> to switch to receiving data segments from the second base station <NUM> instead of the first base station <NUM> in dependence on at least one of reception conditions and load conditions with respect to the first base station <NUM> and the second base station <NUM>. In LTE, this technique is referred to as "Dynamic Cell Selection".

The data segments may be arranged in the first and second sequences by a coordination component. In the embodiment shown in <FIG>, the first base station <NUM> is the coordination component. In this embodiment, the processor <NUM> of the base station is configured to arrange a first data set of data segments in a first sequence, to arrange the first data set of data segments in a second sequence, the second sequence of the first data set being an inverse of the first sequence of the first data set, and to use the data transmitter <NUM> to transmit coordination information to the second base station <NUM>, the coordination information comprising at least one of a request to transmit the first data set in the first sequence to a user terminal <NUM> and a request to transmit the first data set in the second sequence to the user terminal <NUM>.

The transmission of the coordination information is shown in <FIG> with a dotted line between the data transmitter <NUM> of the first base station <NUM> and the data receiver <NUM> of the second base station <NUM>. This communication may be direct between base stations, but may also be routed via the Serving Gateway <NUM>, for example. The second base station <NUM> preferably receives data segments from the Serving Gateway <NUM> (even when the coordination information is exchanged directly between base stations), as shown in <FIG>, but may also receive the data segments from the first base station <NUM>, for example. In LTE, such a first base station <NUM> may be referred to as a so-called 'anchor' eNB and the user data and coordination signalling is exchanged via the X2 interface between the 'anchor' eNB and the cooperating eNBs (e.g. the second base station <NUM>). Preferably, the cooperating eNBs are able to provide feedback to the 'anchor' eNB.

In the embodiment shown in <FIG>, the Serving Gateway (S-GW) <NUM> is the coordination component, which coordinates the downlink transmissions from the multiple points/base stations. In this embodiment, a processor <NUM> of the Serving Gateway is configured to arrange a first data set of data segments in a first sequence, to arrange the first data set of data segments in a second sequence, the second sequence of the first data set being an inverse of the first sequence of the first data set, and to use a data transmitter <NUM> to transmit coordination information to (the data receiver <NUM> of) the first base station <NUM> and (the data receiver <NUM> of) the second base station <NUM>, the coordination information for one of the base stations comprising a request to transmit the first data set in the first sequence to a user terminal <NUM> and the coordination information for the other of the base stations comprising a request to transmit the first data set in the second sequence to the user terminal <NUM>. The Serving Gateway <NUM> further comprises a data receiver <NUM> for receiving data segments from the first base station <NUM> and from the second base station <NUM>.

In an embodiment, the first base station <NUM> is configured to detect that a user terminal <NUM> has not received a previous transmission by the first base station <NUM> of at least part of a data segment and to retransmit the at least a part of the data segment to the user terminal <NUM> upon this detection and the second base station <NUM> is configured to detect that a user terminal <NUM> has not received a previous transmission by the second base station <NUM> of at least part of a data segment and to retransmit the at least a part of the data segment to the user terminal <NUM> upon this detection. In LTE, this can be achieved in the "Acknowledged" mode, for example.

<FIG> illustrates an example of sequences determined in a mobile communication system comprising the first base station <NUM> and the second base station <NUM>. In this example, the first base station <NUM> and the second base station <NUM> are both transmitting to the user terminal <NUM>. The data segments of the first data set (A) are scheduled to be transmitted by the two base stations in inverted sequence. The first base station <NUM> is scheduled to transmit the first data set (A) in normal order in sequence 45a: X1, X2, X3, X4 and then X5, and the second base station <NUM> is scheduled to transmit the first data set (A) in reverse order in sequence 45b: X5, X4, X3, X2 and then X1. Coordination between the base stations only needs to occur when user terminal <NUM> has received all data segments of the first data set (A).

In this example, it is assumed that both base stations take turns transmitting with the same probability, so that the user terminal <NUM> will have received all data segments of the first data set (A) while receiving data segment X3 from the first base station <NUM> or from the second base station <NUM>. This is because the user terminal <NUM> will already have received data segments X1 and X2 from the first base station <NUM> and data segments X5 and X4 from the second base station <NUM>. Then when the user terminal <NUM> has received data segment X3, it will possess all data segments of the first data set (A) and will send a data set acknowledgement to the base station it is currently receiving data segments from. Only then does this base station need to inform the other base station about the completed transmission of the data set, in order to discard the remaining data segments of the data set, i.e. switch to another data set.

The fact that both base stations have same probability of transmission is not restrictive. Independently of how many data segments are transmitted by each base station, there is only an exchange of signalling between the base stations (e.g. through the LTE X2 interface) when there is a data set acknowledgement and not when there is a data segment acknowledgement. In the worst case, there will be one redundant transmission: the user terminal <NUM> acknowledges receipt of the first data set (A) to the base station from which it received the last data segment, e.g. the first base station <NUM>, but in the next timeslot switches to the other base station, e.g. the second base station <NUM>, which transmits one more data segment before it gets informed by the first base station <NUM> about the data set acknowledgement.

<FIG> illustrates an example of sequences determined in a mobile communication system comprising a third base station <NUM> in addition to the first base station <NUM> and the second base station <NUM>. The third base station <NUM> is configured to transmit at least part of a second data set (B) of data segments arranged in a first sequence 46a to the user terminal <NUM>, the second data set (B) comprising different data segments than the first data set (A). So while the first base station <NUM> and the second base station <NUM> are both transmitting the first data set (A), the third base station <NUM> is transmitting a different data set: the second data set (B).

When the first base station <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange a second data set (B) of data segments in a first sequence 46a, the second data set (B) comprising different data segments than the first data set (A), and to use the data transmitter <NUM> to transmit further coordination information to the third base station <NUM>, the further coordination information comprising a request to transmit the second data set (B) in the first sequence 46a to the user terminal <NUM>. When the Serving Gateway <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange a second data set (B) of data segments in a first sequence 46a, the second data set (B) comprising different data segments than the first data set (A), and to use the data transmitter <NUM> to transmit further coordination information to the third base station <NUM>, the further coordination information comprising a request to transmit the second data set in the first sequence 46a to the user terminal <NUM>.

In the example of <FIG>, the first base station <NUM> is configured to transmit at least part of a second data set (B) of data segments arranged in a second sequence 46b after the user terminal <NUM> has acknowledged receipt of the first data set (A), the first sequence 46a of the second data set (B) being an inverse of the second sequence 46b of the second data set (B). The second data set (B) may comprise data segments Y1, Y2, Y3, Y4, Y5 and Y6, for example. In this case, the first sequence 46a of the second data set (B) may be Y2, Y3, Y1, Y5, Y6 and Y4 and the second sequence 46b of the second data set (B) may be Y4, Y6, Y5, Y1, Y3 and Y2, for example.

When the first base station <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange the second data set (B) in a second sequence 46b, the second sequence 46b of the second data set (B) being an inverse of the first sequence 46a of the second data set (B), and the coordination information further comprises a request to transmit the second data set (B) in the second sequence 46b to the user terminal <NUM> after the first data set (A) has been transmitted. When the Serving Gateway <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange the second data set (B) in a second sequence 46b, the second sequence 46b of the second data set (B) being an inverse of the first sequence 46a of the second data set (B), and the coordination information further comprises a request to transmit the second data set (B) in the second sequence 46b to the user terminal <NUM> after the first data set (A) has been transmitted.

In the example of <FIG>, the second base station <NUM> is configured to transmit at least part of a third data set (C) of data segments after the user terminal <NUM> has acknowledged receipt of the first data set (A), the third data set (C) comprising different data segments than the first data set (A) and the second data set (B). So if the transmission of the first data set (A) is finished, one of the base stations that transmitted the first data set (A), in this example the first base station <NUM>, starts to transmit the second data set (B) being transmitted by the third base station <NUM>, while the other base station that transmitted the first data set (A), in this example the second base station <NUM>, progresses with a new, third data set (C).

When the first base station <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange a third data set (C) of data segments in a first sequence 47a and the coordination information sent to the second base station <NUM> further comprises a request to transmit the third data set (C) in the first sequence 47a to the user terminal <NUM> after the first data set (A) has been transmitted, the third data set (C) comprising different data segments than the first data set (A) and the second data set (B). When the Serving Gateway <NUM> is the coordination component, as shown in <FIG>, the processor <NUM> is further configured to arrange a third data set (C) of data segments in a first sequence 47a and the coordination information sent to the second base station <NUM> further comprises a request to transmit the third data set (C) in the first sequence 47a to the user terminal <NUM> after the first data set (A) has been transmitted, the third data set (C) comprising different data segments than the first data set (A) and the second data set (B).

Similarly, when the user terminal <NUM> has completely received the second data set (B), the first base station <NUM> starts transmitting the third data set (C) in sequence 47b, which is the inverse of sequence 47a, which is being used by the second base station <NUM> to transmit the third data set (C). Furthermore, when the user terminal <NUM> has completely received the second data set (B), the third base station <NUM> starts transmitting a new, fourth data set (D) in sequence 48a in a normal order.

<FIG> illustrates another example of sequences determined in a mobile communication system comprising three base stations. In this example, the third base station <NUM> is not available at the same time as the first base station <NUM> and the second base station <NUM>, but becomes available later. This might be the result of the user terminal <NUM> moving closer to the third base station <NUM>, for example. Similar to the example of <FIG>, the third base station <NUM> starts transmitting at least part of a second data set (B) of data segments arranged in a first sequence 46a to the userterminal <NUM>. In this example, it is again assumed that all base stations take turns transmitting with the same probability. As a result, the third base station <NUM> spends less time transmitting the second data set (B) in the example of <FIG> than in the example of <FIG>. On the other hand, the first base station <NUM> spends more time transmitting the second data set (B) in the example of <FIG> than in the example of <FIG>.

<FIG> further shows that when the user terminal <NUM> has completely received the third data set (C), the first base station <NUM> starts transmitting the fourth data set (D) in sequence 48b, which is the inverse of sequence 48a, which is being used by the third base station <NUM> to transmit the fourth data set (D). Furthermore, when the user terminal <NUM> has completely received the third data set (C), the second base station <NUM> starts transmitting a new, fifth data set (E) in sequence 49a in a normal order. Then, when the user terminal <NUM> has completely received the fourth data set (D), the first base station <NUM> starts transmitting the fifth data set (E) in sequence 49b, which is the inverse of sequence 49a, which is being used by the second base station <NUM> to transmit the fifth data set (E).

<FIG> illustrates an example of sequences determined in a mobile communication system comprising a fourth base station <NUM> in addition to the first base station <NUM>, the second base station <NUM> and the third base station <NUM>. In the case of four base stations, it would be possible to group the base stations in two independent sets of two base stations each. However, it would be more beneficial to use all four base stations to transmit all data sets in a more efficient manner, extending the arrangement shown in the example of <FIG>.

Preferably, every time two base stations are transmitting the same data set, the other two base stations are transmitting two different data sets, as shown in <FIG>. As a result, when the first base station <NUM> and the second base station <NUM> are transmitting the first data set (A) in sequences 45a and 45b, the third base station <NUM> is transmitting a second data set (B) in sequence 46a and the fourth base station <NUM> is transmitting a third data set (C) in sequence 47a. The fourth base station is not transmitting the second data set (B) in an inverse of sequence 46a. Similarly, when the user terminal <NUM> has completely received the first data set (A), the first base station <NUM> starts transmitting the second data set (B) in a sequence 46b, which is an inverse of sequence 46a in which the third base station <NUM> is transmitting the second data set (B), but the second base station <NUM> starts transmitting the fourth data set (D) in sequence 48a instead of transmitting the third data set (C) in an inverse of sequence 47a, which is being used by the fourth base station <NUM> to transmit the third data set (C).

Similarly, when the user terminal <NUM> has completely received the second data set (B), the first base station <NUM> starts transmitting the fifth data set (E) in sequence 49a instead of transmitting the fourth data set (D) in an inverse of sequence 48a, which is being used by the second base station <NUM> to transmit the fourth data set (D). A drawback of this scheme is that it might increase latency. This is due to the fact that the user terminal <NUM> might not receive the data sets in sequential order. For example, if the first base station <NUM> and the third base station <NUM> both encounter a problem transmitting the second data set (B), the other base stations cannot assist with transmission until they are done transmitting their own data sets and the user terminal <NUM> might receive the third data set (C) from the fourth base station <NUM> before receiving the second data set (B) from the first base station <NUM> and/or the third base station <NUM>.

<FIG> shows a current protocol implementation used in LTE. LTE uses PDCP protocol <NUM>, RLC protocol <NUM>, MAC protocol <NUM> and PHY/L1 protocol 66a between user equipment <NUM> and eNodeB <NUM>. LTE uses PHY/L1 protocol 66b between eNodeB <NUM> and Serving Gateway <NUM> and PHY/L1 protocol 66c between Serving Gateway <NUM> and PDN Gateway <NUM>. LTE uses GTP-U protocol <NUM>, UDP protocol <NUM> and L2 protocol <NUM> between eNodeB <NUM> and Serving Gateway <NUM> and between Serving Gateway <NUM> and PDN Gateway <NUM>. LTE further uses IP protocol <NUM> between user equipment <NUM> and PDN Gateway <NUM>. Furthermore, an application layer <NUM> is shown is shown in <FIG> connecting user equipment <NUM> with an application running elsewhere, e.g. in the cloud.

<FIG> shows a modified version of this LTE protocol implementation which facilitates the transmission of coordination information. Existing functionalities in eNB and S-GW nodes are re-used to provide CoMP with inverse data segment ordering. In addition to the entities shown in <FIG> shows an additional coordination function <NUM>. This coordination function <NUM> may be part of eNodeB <NUM> or Serving Gateway <NUM>, for example. Alternatively, the coordination function <NUM> may be part of a different coordination component. In LTE, the GTP-U protocol <NUM> is responsible for delivering IP protocol <NUM> packets to the IP endpoint in the backhaul network (i.e. the eNodeB <NUM>). In the modified protocol implementation of <FIG>, the endpoint of the GTP-U protocol is the coordination function <NUM>. This implies that if the coordination function <NUM> is located at the eNodeB <NUM>, the endpoint of the GTP-U is the same as in <FIG>. In case the coordination function <NUM> is located at the Server Gateway <NUM>, the IP layer endpoint is moved from eNodeB <NUM> to the Server Gateway <NUM>. In <FIG>, the coordination function <NUM> and the eNodeB <NUM> communicate using a proposed new GTP-MT protocol <NUM>, which is a version of the GTP-U protocol <NUM> modified for multipoint transmission to include coordination information. The eNodeB <NUM> and the user equipment <NUM> communicate using a proposed new MT-RLC protocol <NUM>, which is a version of the RLC protocol <NUM> modified for multipoint transmission to include data set acknowledgements.

The afore-mentioned protocols are used to transfer payload data between applications. Data packets created in accordance with these protocols typically also have an additional overhead (bits or bytes), e.g. header and/or trailer bits, for the purpose of transporting the payload data. Examples of overhead comprise an indication of the data packet (e.g. a packet sequence number) and/or payload destination, of a (logical) channel, of a data packet and/or a payload length and/or an error check (e.g. CRC). For example, a data packet may comprise an Internet Protocol (IPv4, IPv6) datagram, possibly with additional overhead such as GTP overhead for tunneling the IP packet through part of the telecommunications network (e.g. from a Serving Gateway <NUM> to eNodeB <NUM>), an RLC PDU and a Transport Block as e.g. used on a wireless (radio) connection between eNodeB <NUM> and user equipment <NUM>. A data segment may correspond to a data packet, may comprise a fragment of a data packet or may comprise multiple data packets.

Coordination information sent to eNodeB <NUM> by the (CoMP) coordination function <NUM> may indicate the sequence in which data segments should be transmitted by referring to existing sequence numbers, e.g. PDCP protocol <NUM> or GTP-U protocol <NUM> sequence numbers. The coordination information may then indicate which existing sequence numbers are part of the same data set and in which sequence they should be transmitted. The eNodeB <NUM> can then use this coordination information and the existing sequence numbers of the received data packets to change the order in which the eNodeB <NUM> transmits the received data packets to the user equipment <NUM>.

The method of arranging data segments in sequences comprises three steps, see <FIG>. A step <NUM> comprises arranging a first data set of data segments in a first sequence. A step <NUM> comprises arranging the first data set in a second sequence, the second sequence of the first data set being an inverse of the first sequence of the first data set. A step <NUM> comprises using a data transmitter to transmit coordination information to at least one base station, the coordination information comprising at least one of a request to transmit the first data set in the first sequence to a user terminal and a request to transmit the first data set in the second sequence to the user terminal. The method may be performed by a base station or by a different coordination component.

The method of of transmitting an acknowledgement comprises three steps, See <FIG>. A step <NUM> comprises using a data receiver to receive a first one of a plurality of data segments of a data set from a base station and/or a data segment acknowledgement acknowledging receipt of the first one of the plurality of data segments by a user terminal. A step <NUM> comprises using the data receiver to receive a last one of the plurality of data segments of the data set from the base station and/or a data set acknowledgement acknowledging receipt of the data set by the user terminal. A step <NUM> comprises using a data transmitter to transmit to a further base station a data set acknowledgment acknowledging receipt of the data set by the user terminal, while not transmitting to the further base station a data segment acknowledgment acknowledging receipt of the first one of the plurality of data segments by the user terminal. The method is preferably performed by a base station or a user terminal.

The mobile communication system <NUM> of <FIG> is preferably part of a cellular telecommunications system. <FIG> shows a schematic illustration of a cellular telecommunications system <NUM>. The telecommunications system <NUM> comprises cellular radio access network systems <NUM> (E-UTRAN) and <NUM> (UT(RAN)) and a core network system containing various elements or nodes as described in further detail below.

In the telecommunications system <NUM> of <FIG>, three generations of networks are schematically depicted together for purposes of brevity. A more detailed description of the architecture and overview can be found in 3GPP Technical Specification TS <NUM> 'Network Architecture' which is included in the present application by reference in its entirety.

The lower branch of <FIG> represents a GSM/GPRS or UMTS network.

For a GSM/GPRS network, a radio access network (RAN) system <NUM> comprises a plurality of nodes, including base stations (combination of a BSC and a BTS), not shown individually in <FIG>. The core network system comprises a Gateway GPRS Support Node <NUM> (GGSN), a Serving GPRS Support Node <NUM> (SGSN, for GPRS) or Mobile Switching Centre (MSC, for GSM, not shown in <FIG>) and a Home Location Register <NUM> (HLR). The HLR <NUM> contains subscription information for user devices <NUM>, e.g. mobile stations MS.

For a UMTS radio access network (UTRAN), the radio access network system <NUM> also comprises a Radio Network Controller (RNC) connected to a plurality of base stations (NodeBs), also not shown individually <FIG>. In the core network system, the GGSN <NUM> and the SGSN <NUM>/MSC are connected to the HLR <NUM> that contains subscription information of the user devices <NUM>, e.g. user equipment UE.

The upper branch of the telecommunications system in <FIG> represents a next generation network, commonly indicated as Long Term Evolution (LTE) system or Evolved Packet System (EPS).

The radio access network system <NUM> (E-UTRAN), comprises base stations (evolved NodeBs, eNodeBs or eNBs), not shown individually in <FIG>, providing cellular wireless access for a user device <NUM>, e.g. a user equipment UE. The core network system comprises a PDN Gateway (P-GW) <NUM> and a Serving Gateway <NUM> (S-GW). The E-UTRAN <NUM> of the EPS is connected to the S-GW <NUM> via a packet network. The S-GW <NUM> is connected to a Home Subscriber Server HSS <NUM> and a Mobility Management Entity MME <NUM> for signalling purposes. The HSS <NUM> includes a subscription profile repository SPR for user devices <NUM>.

For GPRS, UMTS and LTE systems, the core network system is generally connected to a further packet network <NUM>, e.g. the internet.

Further information of the general architecture of a EPS network can be found in 3GPP Technical Specification TS <NUM> 'GPRS enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access'.

<FIG> depicts a block diagram illustrating an exemplary data processing system that may perform the methods as described with reference to <FIG>.

Examples of input devices may include, but are not limited to, a keyboard, a pointing device such as a mouse, or the like.

Claim 1:
A mobile communication system (<NUM>), comprising:
a first base station (<NUM>) configured to transmit at least part of a first data set of data segments arranged in a first sequence to a user terminal (<NUM>); and
a second base station (<NUM>) configured to transmit at least part of said first data set of data segments arranged in a second sequence to said user terminal (<NUM>), said second sequence of said first data set being an inverse of said first sequence of said first data set,
a third base station (<NUM>) configured to transmit at least part of a second data set of data segments arranged in a first sequence to said user terminal (<NUM>), said second data set comprising different data segments than said first data set,
wherein one of said first base station (<NUM>) and said second base station (<NUM>) is configured to transmit at least part of said second data set of data segments arranged in a second sequence after said user terminal (<NUM>) has acknowledged receipt of said first data set, said first sequence of said second data set being an inverse of said second sequence of said second data set.