FH/SS-OFDMA Subcarrier Group Allocation for Cellular Interference
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Solution Overview
Problem
Current multiple access technologies in cellular communication systems, such as DS-CDMA, face challenges with severe multipath fading, increased complexity, and difficulty in achieving multiplexing gain and high-speed modulation due to interference between users, making them unsuitable for next-generation mobile communication systems. Additionally, existing OFDMA technologies face issues with pilot load and orthogonality damage in uplink environments.
Innovation Solution
The proposed FH/SS-OFDMA technology divides the frequency band into subcarrier groups, allocates them dynamically to users, and uses both code spreading and frequency hopping to manage resources flexibly, reducing pilot load and maintaining orthogonality between codes through pilot symbols and channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DS-CDMA technology is used to support 2G and 3G mobile communication, then transmission data can be spread in frequency band using spreading code, but severe multipath fading occurs causing interference between adjacent symbols and increased receiving apparatus complexity
Solution Approach 1:
The patent segments the frequency band into multiple subcarrier groups and assigns different spreading codes to different subcarrier groups. This segmentation allows the receiving apparatus to process signals on a per-subcarrier-group basis rather than handling the entire frequency band simultaneously, thereby reducing complexity while maintaining data transmission capability
Solution Approach 2:
The patent implements dynamic resource allocation where subcarrier groups are reassigned to different users based on channel conditions and traffic requirements. This dynamic approach allows the system to adapt to varying multipath fading conditions, improving productivity while keeping the receiving apparatus complexity manageable through selective processing
2Productivity
If DS-CDMA technology is used for transmission, then data can be transmitted using spreading code multiplication, but multiplexing gain for multiple users in frequency domain cannot be achieved and high-speed modulation is difficult due to user interference
Solution Approach 1:
The patent divides the frequency band into multiple subcarrier groups and assigns orthogonal spreading codes to different subcarrier groups. This segmentation creates orthogonal channels for multiple users, enabling multiplexing gain in the frequency domain while maintaining signal orthogonality even at high transmission rates
Solution Approach 2:
The patent changes the allocation parameters dynamically by assigning different spreading codes and subcarrier groups to different users based on channel conditions. This parameter variation allows the system to achieve high-speed modulation while maintaining reliability through adaptive orthogonality management
3Productivity
If MC-CDMA technology is used to allocate different codes to different users in sub-frequency bands, then frequency multiplexing can be achieved, but in uplink it is difficult to restore orthogonality between codes because signals are received through different channels
Solution Approach 1:
The patent introduces a base station as an intermediary that performs centralized channel estimation and resource allocation. The base station receives signals from multiple users through different channels, estimates the channel conditions, and allocates subcarrier groups and spreading codes to maintain orthogonality. This intermediary approach enables frequency multiplexing while restoring code orthogonality in the uplink
Solution Approach 2:
The patent implements feedback mechanisms where the base station receives channel state information from users and adjusts spreading code assignments and subcarrier allocations accordingly. This feedback loop allows the system to maintain code orthogonality in uplink transmissions despite signals traveling through different channels, while preserving frequency multiplexing capabilities
4Adaptability or versatility
If frequency band is divided into subcarrier groups and allocated dynamically to users in FH/SS-OFDMA, then resource allocation flexibility and frequency efficiency are improved, but pilot load increases due to channel estimation requirements
Solution Approach 1:
The patent segments the frequency band into multiple subcarrier groups and performs channel estimation separately for each group. This segmentation allows the system to use fewer pilot signals overall, as each subcarrier group requires fewer pilots compared to estimating the entire frequency band at once, thereby reducing pilot load while maintaining resource allocation flexibility
Solution Approach 2:
The patent performs channel estimation only for actively allocated subcarrier groups rather than for the entire frequency band. This partial action approach reduces the quantity of pilot signals required, as pilots are transmitted and processed only where needed, maintaining adaptability while reducing overhead
Data Source
AI summary
Disclosed is a method and apparatus for transmitting data in a cellular communication system including at least one base station that communicates with a plurality of mobile stations through a given frequency band. The method and apparatus divides the frequency band into at least two subcarrier groups each including a plurality of subcarriers; allocates at least one subcarrier group to each mobile station, and changes the subcarrier group allocated to each mobile station according to a predetermined period; and codes data to be transmitted to each mobile station with a plurality of codes, and transmits modulation symbols obtained by performing inverse fast Fourier transform (IFFT) on a plurality of subcarriers of the allocated subcarrier group.