Random Access Subframe Timing Adjustment for Extended Cell Coverage

Solution Overview

Problem

The existing LTE system's random access technology cannot support cell coverage beyond 100 km, limiting its ability to provide effective communication over longer distances.

Innovation Solution

A method where a receiver performs cell search and downlink synchronization to obtain a time reference, calculates the distance to the base station, selects a suitable random access format based on system parameters and load conditions, and transmits a random access subframe with an adjusted line-of-sight transmission time delay to compensate for downlink time delays, thereby expanding the cell coverage radius without modifying existing protocols.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If the existing LTE random access format parameters (CP length, GT length, cyclic shift) are used, then the system can maintain compatibility with current protocols and base station processing modes, but the cell coverage radius is limited to within 100 km

Engineering Contradiction:

Improvecell coverage radiusVSAvoidcompatibility with existing protocols

Core Design Contradiction:

Length of stationary objectVSAdaptability or versatility

Solution Approach 1:

The receiver performs downlink synchronization to obtain time reference information before transmitting the random access preamble. This preliminary timing alignment allows the receiver to calculate the line-of-sight transmission time delay in advance and compensate for it when transmitting the preamble, enabling coverage beyond 100 km while maintaining protocol compatibility

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the transmission timing parameter by introducing a time advance equal to the line-of-sight transmission time delay. This parameter adjustment compensates for the downlink time delay, allowing the random access preamble to be received within the expected time window at the base station, thereby extending coverage without modifying protocol structures

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If the cyclic shift window length TNcs is increased to support larger cell radii, then the cell edge user can distinguish different cyclic shifts, but the supported cell radius is reduced by half due to the need to absorb two time delays (2D)

Engineering Contradiction:

Improvecell radiusVSAvoidtime delay

Core Design Contradiction:

Length of stationary objectVSLoss of time

Solution Approach 1:

The receiver performs downlink synchronization to obtain time reference information before transmitting the random access preamble. This preliminary timing alignment allows the receiver to calculate the line-of-sight transmission time delay in advance and compensate for it when transmitting the preamble, enabling coverage beyond 100 km while maintaining protocol compatibility

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention applies preliminary counter-action by compensating for the downlink time delay D1 in advance through time advance calculation. By subtracting the calculated time delay from the transmission timing, the system pre-corrects the timing offset, ensuring that the round-trip delay does not cause the preamble to fall outside the cyclic shift window

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If the Guard Time (GT) length is increased to prevent disturbance to following subframes, then the cell edge user transmission is protected, but the overall subframe structure becomes less efficient

Engineering Contradiction:

Improvesubframe isolationVSAvoidsubframe efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The receiver performs downlink synchronization to obtain time reference information before transmitting the random access preamble. This preliminary timing alignment allows the receiver to calculate the line-of-sight transmission time delay in advance and compensate for it when transmitting the preamble, enabling coverage beyond 100 km while maintaining protocol compatibility

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9426829B2Random access method and receiver

Publication Date: 2016.08.23 ZTE CORP

AI summary

The embodiments of the present document provide a random access method and a receiver, wherein, the random access method includes: after starting up, a receiver performing cell search and downlink synchronization to obtain a time reference; the receiver obtaining a distance between itself and a base station; the receiver selecting a random access format according to parameters and a load condition of the system where it is located; the receiver obtaining a cell radius supported by the selected random access format, and calculating a line-of-sight transmission time delay if the cell radius is less than the distance; and based on the time reference, the receiver transmitting a random access subframe the line-of-sight transmission time delay in advance.