Method and arrangement in a mobile communications network

Abstract

The present invention relates to an arrangement and method to design orthogonal UE-specific reference signals so that multiple UE-specific reference signals are feasible to support non-codebook-based multi-stream beamforming/precoding. This is achieved by re-using an existing UE-specific reference signal to obtain additional UE-specific reference signals being orthogonal to the existing UE reference signal.

1 . A method in a network node of a mobile communication network, wherein the network node is associated with an antenna comprising a plurality of antenna ports using non-codebook-based multi-stream beamforming, the method comprises the steps of:
 applying a first UE specific reference signal on a first antenna port, and   reusing the first UE specific reference signal to be applied orthogonally on an antenna port.   
     
     
         2 . The method according to  claim 1 , wherein the reused first UE specific reference signal are multiplexed on a second antenna port in different time-frequency resource elements than the first UE specific reference signal applied on the first antenna port. 
     
     
         3 . The method according to any of  claims 1 - 2 , wherein the reused first UE specific reference signal are applied on the first antenna port sharing the same time-frequency resource elements as the first set of UE specific reference signals. 
     
     
         4 . The method according to  claim 3 , wherein the step of re-using the first UE specific reference signal further comprises:
 code division multiplexing the reused first UE specific reference signal in a set of resource elements.   
     
     
         5 . The method according to  claim 4 , wherein the reused first UE specific reference signal are cyclic shifts of the first set of UE specific reference signals. 
     
     
         6 . The method according to  claim 4 , wherein the reused first UE specific reference signal are orthogonal covers of the first set of UE specific reference signals. 
     
     
         7 . The method according to any of  claims 1 - 4 , wherein the reused first UE specific reference signal are space-frequency block codes based on the first set of UE specific reference signals. 
     
     
         8 . A network node of a mobile communication network, wherein the network node is associated with an antenna comprising a plurality of antenna ports using non-codebook-based multi-stream beamforming, the network node comprises a processor configured to apply a first UE specific reference signal on a first antenna port, and to reuse the first UE specific reference signal to be applied orthogonally on an antenna port. 
     
     
         9 . The network node according to  claim 8 , wherein the processor is configured to multiplex the reused first UE specific reference signal on a second antenna port in different time-frequency resource elements than the first UE specific reference signal applied on the first antenna port. 
     
     
         10 . The network node according to any of  claims 8 - 9 , wherein the processor is configured to apply the reused first UE specific reference signal on the first antenna port sharing the same time-frequency resource elements as the first set of UE specific reference signals. 
     
     
         11 . The network node according to  claim 10 , wherein the processor is further configured to code division multiplex the reused first UE specific reference signal in a set of resource elements. 
     
     
         12 . The antenna according to any of  claims 8 - 11 , wherein the reused first UE specific reference signal are cyclic shifts of the first UE specific reference signal. 
     
     
         13 . The antenna according to any of  claims 8 - 11 , wherein the reused first UE specific reference signal are orthogonal covers of the first UE specific reference signal. 
     
     
         14 . The antenna according to any of  claims 8 - 11 , wherein the reused first UE specific reference signal are space-frequency block codes based on the first UE specific reference signal.