Heterogeneous Network Pilot Signal Spatial Reuse
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Solution Overview
Problem
In heterogeneous network deployments, the combined-cell deployment using Single Frequency Network (SFN) operation for downlink signaling is inefficient due to lack of spatial reuse, leading to inferior performance compared to separate-cell deployments, especially at high network loads, resulting in significant consumption of orthogonal variable spreading factor (OVSF) codes and increased energy consumption.
Innovation Solution
Implementing non-SFN pilot signals transmitted by less than all radio units in a cell, allowing for spatial reuse of OVSF codes across different cell portions by using non-SFN pilot signals as references for control and data channel demodulation, enabling efficient downlink scheduling and reducing energy waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SFN operation is used in combined-cell deployment, then legacy UE compatibility is maintained, but downlink performance deteriorates at high network loads due to lack of spatial reuse
Solution Approach 1:
The patent segments the cell portions within a combined cell to allow different cell portions to transmit different HS-SCCH signals using spatial reuse. This segmentation enables multiple UEs to be served simultaneously in different spatial regions, improving downlink performance while maintaining SFN operation for legacy UE compatibility.
Solution Approach 2:
The patent applies local quality by allowing different cell portions to have different transmission characteristics. Specifically, different cell portions can use different OVSF codes for HS-SCCH signaling, enabling spatial reuse in local regions while maintaining overall SFN coherence for legacy device support.
2Productivity
If spatial reuse is applied in combined-cell deployment, then downlink performance improves, but OVSF code consumption increases significantly
Solution Approach 1:
The patent segments the OVSF code space by allocating different codes to different cell portions. This segmentation allows efficient reuse of codes across spatial dimensions while controlling overall code consumption, as each cell portion uses a subset of codes that can be reused in other portions.
Solution Approach 2:
The patent introduces spatial dimension to OVSF code usage by allowing the same code to be reused in different cell portions simultaneously. This dimensional approach transforms code scarcity into a manageable resource through spatial separation, improving performance without proportionally increasing code consumption.
3Productivity
If multiple HS-SCCH signals are transmitted in each cell portion for spatial reuse, then capacity increases, but device complexity increases for monitoring and demodulation
Solution Approach 1:
The patent applies preliminary action by having the network pre-configure UEs with information about which cell portions to monitor and which HS-SCCH signals are relevant. This pre-configuration reduces the monitoring burden on UEs, allowing them to focus on specific cell portions rather than blindly monitoring all possible signals, thus reducing device complexity while maintaining high capacity.
Data Source
AI summary
A method, in a network node, for transmitting data in a heterogeneous network cellular communication system comprises transmitting of a SFN pilot signal (262). A SFN pilot signal is a pilot signal transmitted by all radio units of a heterogeneous network cell. Optionally, configuration information about non-SFN pilot signals in a cell of the network node is transmitted (260). Non-SFN pilot signals are pilot signals transmitted by less than all radio units of a heterogeneous network cell. The non-SFN pilot signal is transmitted (264). A control channel signal is transmitted (270) on a control channel and a data channel signal associated with the transmitted control channel signal is transmitted (280) on a data channel. A network node operable therefore is also presented. A method for receiving data in a heterogeneous network cellular communication system and a wireless device operable therefore are also presented.