Virtual Carrier Interference Coordination for Machine Type Communication
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Solution Overview
Problem
The increasing deployment of wireless telecommunications systems, particularly LTE networks, leads to higher likelihoods of intercell interference due to the use of unit frequency reuse, which complicates communication for low capability terminal devices like smart meters that require simpler and less resource-intensive solutions.
Innovation Solution
The introduction of virtual carriers within the bandwidth of host carriers allows for reduced complexity receivers in low capability terminals, enabling them to operate effectively by allocating resources differently based on geographic location and using power-boosted transmissions in challenging areas, while coordinating with neighboring base stations to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If advanced data modulation techniques are used in third and fourth generation networks, then data rates are improved, but device complexity and power consumption increase
Solution Approach 1:
The network bandwidth is segmented into multiple virtual carriers, each operating independently with simplified modulation schemes. Low capability terminals can select and camp on a single virtual carrier with reduced complexity requirements, while high capability terminals can utilize multiple virtual carriers to achieve high data rates. This segmentation resolves the contradiction by allowing different terminals to operate at different complexity levels within the same network infrastructure.
Solution Approach 2:
Different virtual carriers are assigned different modulation and coding schemes tailored to specific terminal capabilities and channel conditions. Virtual carriers can be configured with QPSK, 16-QAM, or higher order modulations depending on the intended terminal type and service requirements. This local quality approach allows the system to optimize for low complexity where needed while maintaining high performance capabilities where beneficial.
2Productivity
If unit frequency reuse is adopted in LTE networks, then spectrum efficiency is improved, but intercell interference increases
Solution Approach 1:
Virtual carrier frequencies are dynamically assigned and can be flexibly adjusted based on interference conditions, terminal capabilities, and network load. The system can dynamically select which virtual carriers to activate, their frequency positions, and their bandwidth allocations to optimize the trade-off between spectrum efficiency and interference management in real-time conditions.
Solution Approach 2:
The system changes key parameters such as virtual carrier bandwidth, subcarrier spacing, and cyclic prefix length to adapt to different interference scenarios. By modifying these parameters, the system can maintain spectrum efficiency while reducing vulnerability to intercell interference, particularly for virtual carriers serving cell-edge terminals.
3Device complexity
If virtual carriers are introduced for low capability terminals, then device complexity is reduced, but resource usage efficiency decreases
Solution Approach 1:
The virtual carrier infrastructure serves multiple terminal types simultaneously - low capability terminals can camp on simplified virtual carriers with basic modulation, while high capability terminals can utilize the same virtual carriers with advanced modulation schemes or aggregate multiple virtual carriers. This multi-functionality ensures that resource usage remains efficient across different terminal capabilities without requiring separate infrastructure for each terminal type.
Solution Approach 2:
Low capability terminals autonomously select and camp on virtual carriers that match their capabilities without requiring complex network configuration or handover procedures. The terminals can independently identify suitable virtual carriers, synchronize to them, and begin communication using simplified procedures, thereby reducing network overhead and improving resource usage efficiency.
4Reliability
If power-boosted transmissions are used in challenging areas, then communication reliability is improved, but intercell interference increases
Solution Approach 1:
The system performs preliminary power control and resource allocation decisions before transmissions occur. Base stations exchange coordination information about intended power-boosted virtual carrier transmissions, allowing neighboring cells to preemptively adjust their resource allocations and avoid conflicting transmissions. This preliminary coordination reduces the likelihood of severe intercell interference while maintaining communication reliability in challenging areas.
Solution Approach 2:
The virtual carrier framework acts as an intermediary layer between power control and interference management. By confining power-boosted transmissions to specific virtual carriers with carefully selected frequency positions and time resources, the system can isolate and control interference effects. The virtual carrier structure enables granular power control that limits interference propagation compared to traditional wideband power boosting.
Data Source
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AI summary
A method of operating a base station in a wireless telecommunications system is described. Downlink communications from the base station to terminal devices are made using a plurality of OFDM sub-carriers spanning a system frequency bandwidth. The base station supports communications with a first type of terminal device on a host carrier using OFDM sub- carriers distributed across the system frequency bandwidth and supports communications with a second type of terminal device on a restricted bandwidth carrier using OFDM sub-carriers distributed across a restricted frequency bandwidth which is smaller than and within the system frequency bandwidth. The base station receives from a further base station of the wireless telecommunications system an indication of a transmission characteristic to be used by the further base station for transmissions to the second type of terminal device using a reduced bandwidth carrier associated with the further base station. The base station selects a transmission characteristic for its own transmissions to be made to the second type of terminal device using the restricted bandwidth carrier in a manner that takes account of the indication of the transmission characteristic received from the further base station. The base station then conveys an indication of the transmission characteristic from the base station to at least one other base station of the wireless telecommunications system. Thus, the respective base stations exchange information regarding their restricted bandwidth carrier transmissions to help them coordinate their respective transmissions with a view to reducing intercell interference.