Mobile data transmission and data services are constantly making progress. With the increasing penetration of such services, a terminal apparatus such as a user equipment UE (or mobile station MS, or the like; different names may apply for respective different standards) is capable of communicating within a cellular network environment. For example, a terminal device UE communicates within the network environment in which it is deployed or “camping” based on an available system configuration, generally adopted by a serving network transceiver station (e.g. base station BS or NodeB, or evolved NodeB, eNB) and related network architecture.
Typically, however, those cellular network environments are prone to interference, and also intercell interference may occur insofar as one network entity such as a network transceiver device (e.g. base station, NodeB, or evolved NodeB eNB) may interfere with its transmission with the transmission of another network transceiver device. Such interference phenomena may increase and/or be more dominant in case of network transceiver devices applying different transmission powers and hence exhibiting different coverage areas of the cells which they represent. One typical and exemplary scenario is for example a cellular network environment which adopts so-called macro cells (associated to/defined by macro eNBs) together with one or more pico or femto cells (associated to/defined by pico/femto eNBs) that are deployed within the coverage of the macro cell.
In the following, aspects of the invention will be exemplarily described with reference to such a scenario. In order to enhance legibility and understandability of the invention, for explanatory purposes only, reference is made to the communication system of LTE or LTE-A (Long Term Evolution, LTE-Advanced). However, reference to such specific system and use of specific signalling names or channel names or names of entities constituting such a communication network or partial network environment is not intended to limit the present invention to those specific examples. Rather, the principles of the present invention can be transferred to any other communication system adopting different channel/signaling/entity names as compared to LTE/LTE-A.
Also, the macro/pico cell environment is used as an example only and other environments can be used, e.g. environments having plural macro cells/macro eNBs and/or plural pico/femto eNBs within a macro cell, as long as (intercell) interference occurs or may be expected to occur between the respective cells.
In case of a terminal such as a UE communicating in such an environment while being “mobile” and thus moving within the network environment and the coverage of one or more cells, the terminal may be served by different network transceiver devices eNBs over time. In order to change the serving network transceiver device, the terminal needs to be handed over from an initially serving network transceiver device (source) to a target network transceiver device (which, upon handover, becomes the new serving network transceiver device).
Thus, when a terminal UE performs a handover from a macro cell to a pico cell in a cell range extension area, the terminal UE needs some signaling to assist the terminal UE to do cell specific reference signal (CRS) interference cancellation (IC). In this regard, some work is already ongoing in 3GPP (3rd Generation Partnership Project) on advanced receivers for UE in order to enable better overall performance e.g. in situations where the network is deploying cells using range extension (RE). So far, in those works, the understanding is that cell specific reference signal interference cancellation (CRS IC) is to be used by UEs in connected mode and there does not seem to be any need for idle mode UEs to apply CRS IC. Even in networks where enhanced ICIC (eICIC) is used and network is applying range extension (RE) by use of a concept of pico/macro coordinated almost blank subframe (ABS) muting, there is still some information transmitted in the downlink (DL) almost blank subframe (ABS) from the eNBs. For example, due to support of legacy UEs, the CRS is still transmitted in ABS as well as other DL signals like e.g. a primary broadcast control channel PBCH. These transmissions in ABS will cause interference and work is ongoing on how to limit the impact from this interference on the UE side by applying advanced receiver types which are capable of canceling this interference by applying CRS IC.
In order to apply CRS IC, the UE, however, needs to know which CRS to cancel and also some other basic information concerning the transmission from one or more interfering eNB. In order to get the most efficient system solution, support from the network should be provided in form of such related information to the UEs.
Currently, eICIC is only used by a UE in connected mode. In most of the cases, a UE in pica RE region will camp on a macro cell first in idle mode and then after connection setup, the eNB will handover the UE to pico cell. In this way the offload gain from macro (to pico) can be reached once the macro eNB cell has transferred “handling” of the UE communication to the pico eNB.
Related network signaling can be done in many alternative ways such as by a dedicated radio resource control (RRC) signaling or including the information in the handover (HO) command.
However, a problem with including the information in the HO command is that this command is normally sent at cell edge. However, at cell edge (i.e. border of neighboring cells) the probability of unsuccessful reception at UE side is somewhat higher (e.g. due to lower signal strength of serving eNB at the edge and/or due to increase in interference from a potential target eNB). Additionally one can expect that one of the (most) interfering cells (or at least a dominant interference point (DIP) to cancel) will be the (serving) cell from which the HO is performed.
Thus, there is still a need to further improve such systems in relation to enable proper operation of terminals in such scenarios in relation to CRS IC, and hence a need to provide improved methods, devices and computer program products for corresponding terminals and network transceiver devices.