Small Cell Timing via Wireless Side-Haul
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Solution Overview
Problem
In indoor deployments of LTE and 5G small cells, achieving strict time synchronization in TDD mode is challenging without access to a clear sky for GPS signals, as traditional methods require external GPS antennas, which are impractical in multi-tenant buildings.
Innovation Solution
Utilizing User Equipment (UE) connected to a macro base station to receive timing information, which is then wirelessly transmitted to a Precision Time Protocol (PTP) Grand Master within the small cell network, eliminating the need for external GPS signals by leveraging existing MNO base station timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external GPS antenna is used for time synchronization, then timing accuracy is improved, but installation complexity and accessibility worsen in multi-tenant buildings
Solution Approach 1:
The patent introduces an intermediary system consisting of a macro base station and small cell base stations that relay timing information wirelessly. Instead of directly connecting GPS antennas to each small cell, the macro base station receives GPS timing signals and distributes them to small cells through wireless communication, eliminating the need for physical GPS antenna installation in each location.
Solution Approach 2:
The patent replaces the mechanical/physical connection system (GPS cables running through buildings) with a wireless communication system. Timing information is transmitted via radio frequency signals between macro base stations and small cell base stations, eliminating the need for physical cable infrastructure and GPS antenna installation in each small cell location.
2Reliability
If GPS cable is run from roof to data room, then time synchronization is achieved, but installation cost and complexity increase in multi-story buildings
Solution Approach 1:
The patent replaces the mechanical cable installation system with a wireless communication system. The macro base station receives GPS timing signals wirelessly and transmits them to small cell base stations via radio frequency, eliminating the need to run physical GPS cables from roofs through building structures to data rooms.
Solution Approach 2:
The patent makes the existing wireless communication infrastructure serve multiple functions: it not only transmits user data but also carries timing synchronization signals. The macro base station and small cell base stations use their existing wireless communication capabilities to distribute timing information, eliminating the need for separate dedicated GPS cable infrastructure.
3Measurement precision
If PTP GM is placed in each store, then timing distribution is improved, but negotiation and coordination requirements worsen
Solution Approach 1:
The patent merges the timing distribution function into the existing cellular network infrastructure. Instead of placing separate PTP Grand Masters in each store, the macro base station serves as a centralized timing source that distributes synchronized time to all small cell base stations across multiple tenants, eliminating the need for separate timing systems and negotiations for each location.
Data Source
AI summary
A method and apparatus are disclosed in which a first UE (User Equipment) receives signals from one or more MNO base stations. The UE synchronizes with the MNO base station timing. The first UE then communicates with a second UE over a wireless side-haul, providing the second UE with timing information derived from the MNO base station. By using the wireless side-haul, a relatively short GPIO (General Purpose Input/Output) connection over a wireline can be used to communicate the timing information from the second UE to a PTP GM (Precision Timing Protocol Grand Master). The second UE may be integrated into a cell of a communications network that contains the PTP GM. Accordingly, using the side-haul to communicate the timing information avoids cabling to a master cell.