Two-Step Uplink Synchronization for Pico/Femtocell Interference
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Solution Overview
Problem
In wireless mobile communication systems, pico/femtocells deployed with overlaying macro/microcells face challenges in uplink synchronization, leading to potential interference between radio signals, and existing solutions like non-synchronous ranging channels result in hardware complexity and interference issues.
Innovation Solution
A two-step uplink synchronization method where the pico/femto base station broadcasts UL transmission timing advance offset information, allowing mobile stations to adjust their timing, enabling the use of a unified synchronous ranging channel and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If non-synchronous ranging channel is used for uplink synchronization in pico/femtocell, then uplink interference between pico/femto mobile station and macro/micro mobile station is avoided, but hardware complexity increases and interference issues occur between different channels
Solution Approach 1:
The patent applies homogeneity by making the ranging channel synchronous with the data channel, meaning they share the same timing structure and synchronization mechanism. This eliminates the need for separate non-synchronous channel handling, reducing hardware complexity while maintaining interference avoidance through proper timing alignment based on the offset value
Solution Approach 2:
The patent changes the timing parameter of the ranging channel to be synchronous with the data channel by applying a timing offset. This parameter adjustment allows the ranging channel to maintain synchronization while still avoiding uplink interference, resolving the contradiction between interference avoidance and hardware complexity
2Reliability
If non-synchronous ranging channel with different cyclic prefix length is used, then uplink timing difference is accommodated, but interference with data channel occurs and orthogonality is destroyed
Solution Approach 1:
The patent makes the ranging channel homogeneous with the data channel by using the same cyclic prefix length and synchronization timing. This eliminates the interference and orthogonality destruction problems while maintaining reliable ranging performance through the timing offset mechanism that accounts for propagation delays
3Loss of time
If different cyclic prefix lengths are used for ranging channel and data channel, then time difference of non-aligned uplink subframes is accommodated, but orthogonality in frequency domain is destroyed
Solution Approach 1:
The patent changes the timing parameter of the ranging channel to align with the data channel by applying an offset value that accounts for propagation delays. This allows the system to accommodate time differences through parameter adjustment rather than structural changes, preserving orthogonality and frequency domain reliability
Data Source
AI summary
A two-step uplink synchronization method is provided for uplink synchronization between a mobile station and a pico/femto base station that is deployed together with an overlay macro/micro base station. In a first step, the pico/femto BS encodes and broadcasts UL transmission timing advance offset information via a broadcast channel. The MS decodes the received UL transmission timing advance offset information and advances its uplink timing for uplink ranging or reference signal transmission based on the decoded offset value. In a second step, the MS and the pico/femto BS performs regular uplink synchronization and uplink access. In one example, the UL transmission timing advance offset information indicates a round-trip propagation time of radio signals between the pico/femto base station and the overlay macro/micro base station. By using the two-step uplink synchronization method, a unified synchronous ranging channel may be used for ranging and UL access in pico/femtocells with reduced interference.