TECHNICAL FIELD

The present disclosure is directed to wireless communications and, more particularly, to addressing connectivity issues in wireless communications networks that support simultaneous connections of a wireless device to two base stations.

BACKGROUND

In a typical cellular radio system, wireless terminals (also referred to as user equipment unit nodes, UEs, mobile terminals, and/or mobile stations) communicate via a radio access network (RAN) with one or more core networks, which provide access to data networks, such as the Internet, and/or the public-switched telecommunications network (PSTN). The RAN covers a geographical area that is divided into cell areas, with each cell area being served by a radio base station (also referred to as a base station, a RAN node, a “NodeB”, and/or enhanced NodeB “eNodeB”). A cell area is a geographical area where radio coverage is provided by the base station equipment at a base station site. The base stations communicate through radio communication channels with wireless terminals within range of the base stations.

Cellular communications system operators have begun offering mobile broadband data services based on, for example, WCDMA (Wideband Code Division Multiple Access), HSPA (High Speed Packet Access), and Long Term Evolution (LTE) wireless technologies. Moreover, fueled by introduction of new devices designed for data applications, end user performance requirements are steadily increasing. The increased adoption of mobile broadband has resulted in significant growth in traffic handled by high-speed wireless data networks. Accordingly, techniques that allow cellular operators to manage networks more efficiently are desired.

Techniques to improve downlink performance may include 4-branch MIMO, multiflow communication, multi carrier deployment, etc. Since spectral efficiencies per link may be approaching theoretical limits, next steps may include improving spectral efficiencies per unit area. Further efficiencies for wireless networks may be achieved, for example, by changing a topology of traditional networks to provide increased uniformity of user experiences throughout a cell. Currently, so-called heterogeneous networks are being developed for 3GPP as discussed, for example, in: RP-121436, Study on UMTS Heterogeneous Networks, TSG RAN Meeting #57, Chicago, USA, 4th-7th September 2012; R1-124512, Initial considerations on Heterogeneous Networks for UMTS, Ericsson, ST-Ericsson, 3GOO TSG RAN WG1 Meeting #70bis, San Diego, Calif., USA, 8th-12th Oct. 2012; and R1-124513, Heterogeneous Network Deployment Scenarios, Ericsson, ST-Ericsson, 3GPP TSG-RAN WG1 #70bis, San Diego, Calif., USA, 8th-12th Oct. 2012.

A homogeneous network is a network of base stations (also referred to as NodeB's, enhanced NodeB's, or eNBs) in a planned layout, providing communications services for a collection of user terminals (also referred to as user equipment nodes, UEs, and/or wireless terminals) in which all base stations may have similar transmit power levels, antenna patterns, receiver noise floors, and/or backhaul connectivity to the data network. Moreover, all base stations in a homogeneous network may offer unrestricted access to user terminals in the network, and each base station may serve roughly a same number of user terminals. Current cellular wireless communications systems in this category may include, for example, GSM (Global System for Mobile communication), WCDMA, HSDPA (High Speed Downlink Packet Access), LTE (Long Term Evolution), Wimax (Worldwide Interoperability for Microwave Access), etc.

In a heterogeneous network, low power base stations (also referred to as low power nodes, LPNs, micro nodes, pica nodes, femto nodes, relay nodes, remote radio unit nodes, RRU nodes, small cells, RRUs, etc.) may be deployed along with or as an overlay to planned and/or regularly placed macro base stations. A macro base station MBS may thus provide service over a relatively large macro cell area and each LPN may provide service for a respective relatively small LPN cell area within the relatively large macro cell area. Power transmitted by an LPN (e.g., 2 Watts) may be relatively small compared to power transmitted by a macro base station (e.g., 40 Watts for a typical macro base station). An LPN may be deployed, for example, to reduce/eliminate a coverage hole(s) in the coverage provided by the macro base stations, and/or to off-load traffic from macro base stations (e.g., to increase capacity in a high traffic location, also referred to as a hot-spot). Due to the lower transmit power and smaller physical size, an LPN may offer greater flexibility for site acquisition.

SUMMARY

In initial discussions among members of the 3rd-Generation Partnership Project (3GPP) regarding the development of Release 12 specifications for LTE, one of the proposed items for study is the possibility of simultaneously serving a User Equipment (UE) from more than one eNB. In the disclosure that follows, this is called “dual connectivity.” The control plane procedures of LTE have to be updated in order to support this.

With dual connectivity, activation of a new configuration might encounter difficulties. For example, a UE may be connected to a master eNB (MeNB) and add connectivity to a secondary eNB when given the opportunity, e.g. when being within coverage of a LPN providing the UE a capacity boosting by means of an additional radio resources. With two (or more) such connections, the UE may keep the control signaling connection only with the MeNB, and only the master eNB (MeNB) then knows when a reconfiguration towards the SeNB has been applied by the UE. The MeNV needs to inform the SeNB that the UE has applied the reconfiguration. However, meanwhile the UE may continue to communicate using the radio resources of the SeNB. The configuration for this communication can be old or new, which is not known by the SeNB. One possibility would be to indicate an activation time, as used in e.g. 3G/HSPA, upon which the configuration is to be applied. However, such an activation time must be set conservatively to ensure that the UE will receive the configuration before activation, and thus this increases the delay of radio resource reconfiguration.

An object of the present disclosure is to solve or at least alleviate at least one of the above mentioned problems.

The object is according to a first aspect achieved by a method performed in a wireless device for handling connectivity to two network nodes. The method comprises: receiving, from a first network node, a radio resource configuration message, the radio resource configuration message indicating a change in configuration of a connection towards a second network node; applying the change in configuration towards the second network node in response to the radio resource configuration message; and initiating a random access procedure towards the second network node after applying the change in configuration.

The method enables changing a connection configuration towards the second network node in a dual connectivity setup. The method ensures that the second network node and the wireless device change to the new configuration at the same time, and provides a delay efficient way for reconfiguration. By initiating the random access procedure towards the second network node, upon having executed the reconfiguration, the second network node is made aware of the fact that the wireless device has received and applied the new configuration, i.e. that the wireless device has changed to the new configuration.

The object is according to a second aspect achieved by a wireless device for handling connectivity to two network nodes. The wireless device is configured to: receive, from a first network node, a radio resource configuration message, the radio resource configuration message indicating a change in configuration of a connection towards a second network node; apply the change in configuration towards the second network node in response to the radio resource configuration message, and initiate a random access procedure towards the second network node after applying the change in configuration.

The object is according to a third aspect achieved by a computer program for a wireless device for handling connectivity to two network nodes. The computer program comprises computer program code, which, when executed on at least one processor on the wireless device causes the wireless device to perform the method of the first aspect above.

The object is according to a fourth aspect achieved by a computer program product comprising a computer program as above and a computer readable means on which the computer program is stored.

The object is according to a fifth aspect achieved by a method performed in a first network node, for managing connectivity of a wireless device to the first network node and a second network node. The method comprises receiving, from the second network node, radio resource configuration information for a connection between the wireless device and the second network node; sending in response to and based on the radio resource configuration information received from the second network node, a radio resource configuration message to the wireless device, the radio resource configuration message indicating a change in configuration of a connection towards the second network node; and receiving a message from the wireless device, the message indicating that the change in configuration is complete.

The object is according to a sixth aspect achieved by a first network node for managing connectivity of a wireless device to the first network node and a second network node. The first network node is configured to: receive, from the second network node, radio resource configuration information for a connection between the wireless device and the second network node; send in response to and based on the radio resource configuration information received from the second network node, a radio resource configuration message to the wireless device, the radio resource configuration message indicating a change in configuration of a connection towards the second network node; and receive a message from the wireless device, the message indicating that the change in configuration is complete.

The object is according to a seventh aspect achieved by a computer program for a first network node for managing connectivity of a wireless device to the first network node and a second network node. The computer program comprises computer program code, which, when executed on at least one processor on the first network node causes the first network node to perform the method according to the fifth aspect above.

The object is according to an eight aspect achieved by a computer program product comprising a computer program as above, and a computer readable means on which the computer program is stored.

The object is according to a ninth aspect achieved by a method performed in a second network node, for managing connectivity of a wireless device to a first network node and the second network node. The method comprises sending, to the first network node, radio resource configuration information for a connection between the wireless device and the second network node; receiving a random access preamble from the wireless device, responsive to the radio resource configuration information; and sending a random access response to the wireless device.

The object is according to a tenth aspect achieved by a second network node for managing connectivity of a wireless device to a first network node and the second network node. The second network node is configured to: send, to the first network node, radio resource configuration information for a connection between the wireless device and the second network node; receive a random access preamble from the wireless device, responsive to the radio resource configuration information; and send a random access response to the wireless device.

The object is according to an eleventh aspect achieved by a computer program for a second network node for managing connectivity of a wireless device to a first network node and the second network node. The computer program comprises computer program code, which, when executed on at least one processor on the second network node causes the second network node to perform the method according to the ninth aspect above.

The object is according to a twelfth aspect achieved by a computer program product comprising a computer program as above, and a computer readable means on which the computer program is stored.

Further aspects, features and advantages of the present disclosure will become clear upon reading the following description and the accompanying drawings.

