The constantly increasing demand for high data rates in cellular networks requires new approaches to meet this expectation. A challenging question for operators is how to evolve their existing cellular networks so as to meet the requirement for higher data rates. In this respect, a number of approaches are possible: i) increase the density of their existing macro base stations, ii) increase the cooperation between macro base stations, iii) deploy smaller base stations or relay nodes (RNs) in areas where high data rates are needed within a macro base stations grid, iv) employ pico or small cell overlay technology within buildings, or v) employ device-to-device communications to offload traffic from the cellular macro.
Building a denser macro base station grid, while simultaneously enhancing the cooperation between macro base stations (hence either using options i) or ii) above) is definitely a solution that meets the requirement for higher data rates; however such an approach is not necessarily a cost-efficient option, due to the costs and delays associated with the installation of macro base stations, especially in urban areas where these costs are significant.
Deploying relay nodes as required in a network to grow its capacity and coverage can be advantageous from a perspective of ease and flexibility of deployment, however the robustness of the coverage and capacity provided by overlay relay nodes in a macro network, is not always guaranteed due to possible interference from relay nodes in adjacent cells to the cell of the desired signal transmissions.
One of the main objectives of low power nodes is to absorb as many users as possible from a macro layer in order to offload the macro layer and allow for higher data rates in both the macro and in a pico layer. In this respect, several techniques have been discussed and proposed within 3GPP:                (1) Extending the range of small cells or relays (i.e. low power nodes or LPNs) by using cell specific cell selection offsets.        (2) Increasing the transmission power of Low Power Nodes (LPNs) simultaneously by setting appropriately the UL power control target P0 for the users connected to low power nodes.        (3) Employing beamforming at LPNs acting as relays for communication between the serving macro base stations as well as between receiver mobile devices or user equipment (UE).        
Thus the solution of deploying LPNs acting as relays within the already existing macro layer grid is an appealing option because since these LPNs are anticipated to be more cost-efficient than macro base stations, their deployment time and cost will be less. In such scenarios, use of relay nodes that employ in-band backhaul may provide a viable option that provides pico cell type coverage either indoors or outdoors and mitigates the cost and effort of deploying land-line backhaul to all the pico base stations.
As noted above, there exists the potential for relay based communications to cause interference to both the transmissions in the serving cell of desired signals as well as to adjacent cells in the network.
Deployment of relay nodes that do not cause interference can, in many instances, require careful deployment of the location and orientation of the antenna of relay nodes which can impact the ease and cost of deployment. This may require additional time and labor which is undesirable. As such, systems and methods for interference and/or power reduction for relay nodes are needed.
USPTO Backgrounds
USPTO Backgrounds