Clean Carrier Allocation for Uplink Interference Reduction
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Solution Overview
Problem
In mobile communications networks, existing solutions face challenges in reducing interference between high data rate (HDR) and low data rate (LDR) users, leading to unstable radio environments and limited data rates for LDR users, as well as inefficiencies in inter-cell interference reduction.
Innovation Solution
The method involves dynamically allocating HDR users to 'clean carriers' where they operate in Time Division Multiplexing (TDM) mode, isolating them from LDR users in Code Division Multiplexing (CDM) mode, thereby preventing interference and allowing HDR users to transmit at higher rates without affecting LDR users, and using L1 signalling for dynamic resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If interference cancellation (IC) is applied to HDR users in TDM mode to reduce interference for LDR users, then interference reduction is achieved, but the radio environment becomes unstable due to high variation in IC efficiency, data rate variation, and power control fluctuations
Solution Approach 1:
The patent segments the uplink transmission into two separate carriers: a clean carrier dedicated to HDR users in TDM mode and a non-clean carrier for LDR users in CDM mode. This physical separation eliminates the unstable interaction between IC operations and LDR users, as HDR users no longer share the same carrier with LDR users. The segmentation resolves the contradiction by isolating the interference source from the affected users while maintaining the benefits of IC where applicable.
Solution Approach 2:
The patent extracts HDR users from the mixed CDM/TDM environment and relocates them to a dedicated clean carrier. This extraction removes the source of radio environment instability from the LDR user experience, allowing LDR users to operate in a stable CDM environment without being affected by HDR users' IC operations, power control variations, or data rate fluctuations.
2Productivity
If HDR users are allowed to transmit at high data rates, then throughput is improved, but interference to LDR users increases due to non-orthogonality in CDM mode
Solution Approach 1:
The patent segments users into two groups operating on separate carriers: HDR users on a clean carrier and LDR users on a non-clean carrier. This segmentation allows HDR users to transmit at high data rates in TDM mode without causing interference to LDR users, as the carriers are physically separated. The high data rate productivity is achieved while eliminating the harmful interference through carrier isolation.
Solution Approach 2:
The patent extracts HDR users from the CDM environment where they would interfere with LDR users and places them on a dedicated clean carrier. This extraction enables HDR users to achieve high data rates without their transmissions affecting LDR users, as they operate in isolation on a separate carrier frequency.
3Device complexity
If TDM scheduling is used for HDR users to reduce interference, then interference cancellation requirements are reduced, but the radio environment becomes unstable due to high variation in IC efficiency and power control
Solution Approach 1:
The patent segments the system into clean and non-clean carriers, allowing TDM scheduling for HDR users on the clean carrier without requiring complex interference cancellation for LDR users on the non-clean carrier. The segmentation isolates the TDM operations from LDR users, eliminating the need for IC while maintaining radio environment stability, as LDR users experience only the stable CDM environment.
Solution Approach 2:
The patent extracts LDR users from the environment where TDM scheduling and IC operations create instability. By placing LDR users on a separate non-clean carrier, the instability caused by TDM scheduling variations, IC efficiency fluctuations, and power control changes is removed from their experience, allowing simpler scheduling without compromising stability.
4Area of stationary object
If LDR users share carriers with HDR users in CDM mode, then carrier utilization is improved, but capacity is reduced due to higher required SIR for LDR traffic
Solution Approach 1:
The patent segments carriers into clean and non-clean types, allowing optimal utilization of each: the clean carrier is dedicated to HDR users who can achieve high data rates in TDM mode, while the non-clean carrier serves LDR users in CDM mode without HDR interference. This segmentation improves overall carrier utilization by matching user types to appropriate carriers while maximizing LDR user capacity on the non-clean carrier by eliminating HDR interference, thereby reducing the required SIR for LDR traffic.
Data Source
AI summary
The invention relates to a method for reducing interference between users in a mobile communications network (1) in which uplink transmissions from user equipment, UE (3), to a radio base station, RBS (5A, 5B), can be performed on at least two different carriers (C1, C2). The UE (3) support dynamic switching between CDM and TDM transmission mode and the RBS (5A, 5B) is arranged to dynamically set the mode of transmission for the UE (3). The method comprises the steps of: —identifying (S200) at least a first UE as a high data rate, HDR, UE currently requiring high data transmission rate; dedicating (S201) at least one of said at least two carriers (C1, C2) to said HDR UE for at least a first period of time (T), said at least one carrier (C1, C2) hereinafter being named clean carrier, and—allocating (S202) said at least first HDR UE to said clean carrier (C1, C2) during said at least first period of time (T). This method ensures that no UE operating in CDM mode is transmitting on the same carrier at the same time as the HDR UE.