NB-IoT Subcarrier Allocation in LTE Guard Bands
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Solution Overview
Problem
Narrowband Internet of Things (NB-IoT) systems face limitations when operating in-band with LTE carriers, as they occupy LTE resources, reducing LTE throughput and not fully utilizing available capabilities, and when operating in guard bands, they require passband extensions and have insufficient bandwidth in low-bandwidth LTE options.
Innovation Solution
The solution involves shifting the frequency of LTE and NB-IoT channels, blanking resources in LTE and NB-IoT channels, and adjusting duplex distances to increase the guard band size, allowing NB-IoT to operate in the guard band of LTE by providing additional resources and optimizing filter roll-off, thereby enabling efficient coexistence and utilization of spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If NB-IoT operates in-band with LTE carrier, then spectrum utilization is improved, but LTE throughput is reduced and LTE resources are occupied
Solution Approach 1:
The patent segments the LTE physical resource block by designating specific resource elements for NB-IoT while preserving other resources for LTE. This includes allocating specific subcarriers and resource elements within the PRB for NB-IoT control channels (NPBCH, NPDCCH, NPDSCH) and data channels (NPUCCH, NPUSCH), while leaving PDSCH, PUCCH, and other LTE-specific resources available for LTE operations, thereby enabling simultaneous operation of both systems without complete resource occupation
Solution Approach 2:
The patent applies local quality by allowing different parts of the resource block to have different functions. Specific resource elements are designated with NB-IoT-specific properties (e.g., muted reference signals, dedicated control channel resources) while other regions maintain standard LTE properties. This enables NB-IoT to utilize specific local resources within the PRB without affecting the overall LTE throughput, as only localized portions of the spectrum are dedicated to NB-IoT operations
2Productivity
If NB-IoT operates at guard band of LTE, then LTE resources are preserved, but guard band bandwidth is insufficient for low-bandwidth LTE options
Solution Approach 1:
The patent implements nesting by placing the NB-IoT system within the LTE carrier structure itself rather than in the external guard band. The NB-IoT physical resource block is nested within the LTE PRB boundaries, allowing NB-IoT to access resources internally within the LTE spectrum allocation. This nested approach enables NB-IoT to operate even when external guard bands are too small, as it utilizes the internal structure of the LTE carrier rather than requiring external spectrum space
Solution Approach 2:
The patent transitions from the traditional one-dimensional guard band approach to a two-dimensional resource allocation within the PRB. Instead of requiring additional spectral space in the frequency dimension (guard band extension), the solution creates virtual NB-IoT resources by reconfiguring the time-frequency grid within the existing PRB boundaries. This dimensional transformation allows NB-IoT to operate within the same spectral footprint as LTE by utilizing different resource element patterns and mappings
3Area of stationary object
If NB-IoT operates at guard band with passband extension, then NB-IoT bandwidth requirements are met, but stop band requirements for LTE are imposed
Solution Approach 1:
The patent extracts the NB-IoT operational requirements from the traditional guard band context and relocates them within the LTE PRB structure. By taking out the need for external guard band space and implementing NB-IoT resources internally within the PRB, the solution eliminates the requirement for LTE stop band filtering. The NB-IoT resources are isolated through resource element muting and dedicated allocation patterns rather than requiring spectral separation, thereby removing the harmful filtering requirements while still meeting NB-IoT bandwidth needs
Data Source
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AI summary
Various communication systems may benefit from an improved signaling protocol. For example, communication systems may benefit from an improved network support for a narrowband internet of things in a hosting long term evolution carrier. A method, in certain embodiments, includes shifting a frequency of a downlink long term evolution channel by a pre-determined amount. The shift causes a duplex distance between the downlink long term evolution channel and an uplink long term evolution channel to change. The method includes blanking at least one overlapping radio resource in at least one of the uplink long term evolution channel or an uplink narrowband internet of things channel. The uplink narrowband internet of things channel and the uplink long term evolution channel at least partially overlap. In addition, the method includes receiving data on the uplink narrowband internet of things channel and an additional uplink narrowband internet of things channel at a network entity from a user equipment.