Hybrid FDM-CDM Structure for Non-Contiguous Uplink Transmission
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Solution Overview
Problem
Conventional wireless communication systems lack the ability to provide maximum frequency diversity to users, restricting them from transmitting over non-contiguous tones and thus not utilizing the entire available bandwidth effectively.
Innovation Solution
The implementation of a hybrid FDM-CDM (Frequency Division Multiplexing-Code Division Multiplexing) structure, which allows users to transmit over non-contiguous tones by employing cyclic shifts of spreading sequences and frequency hopping, along with time-domain CDM to maintain orthogonality between pilots across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FDM or CDM structures are used, then users can transmit on assigned frequencies or codes, but users cannot transmit over non-contiguous tones and thus cannot achieve maximum frequency diversity
Solution Approach 1:
The patent combines FDM and CDM into a hybrid structure where FDM provides frequency division for different users while CDM enables each user to transmit across non-contiguous frequency tones using code spreading. This merging allows users to achieve maximum frequency diversity by occupying dispersed frequency resources while maintaining user isolation through orthogonal codes.
Solution Approach 2:
The invention adds a code domain dimension to the traditional frequency domain resource allocation. By introducing spreading codes in the CDM dimension, users can transmit on non-contiguous tones that would traditionally be assigned to different users, thereby achieving frequency diversity without sacrificing transmission flexibility.
2Productivity
If users are allowed to transmit over non-contiguous tones to maximize frequency diversity, then bandwidth utilization improves, but maintaining orthogonality between users becomes more difficult
Solution Approach 1:
Orthogonal spreading codes serve as intermediaries that mediate between multiple users transmitting on overlapping or non-contiguous frequency resources. The codes ensure that even when users occupy the same or overlapping frequency tones, their signals remain orthogonal and can be separated at the receiver, thus maintaining orthogonality while maximizing bandwidth utilization.
3Reliability
If the entire available bandwidth is utilized by a single user through non-contiguous tones, then frequency diversity is maximized, but interference management with other users becomes more complex
Solution Approach 1:
The available bandwidth is segmented into multiple frequency tones that are allocated to different users through a combination of FDM (contiguous frequency blocks) and CDM (dispersed non-contiguous tones with code separation). This segmentation allows each user to access dispersed frequency resources for diversity while the systematic allocation and orthogonal coding simplify interference management compared to allowing arbitrary non-contiguous access for all users.
Data Source
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AI summary
A system and method for hybrid FDM (frequency division multiplexing)-CDM (code division multiplexing) structure for single carrier control channels is provided. The hybrid FDM-CDM structure maximizes frequency diversity over the entire available bandwidth such that orthogonality between signals from users in a given cell is maintained. Thus, users in the given cell can transmit over a non-contiguous set of tones. Furthermore, the hybrid FDM-CDM structure maintains orthogonality of a pilot of users in different cells based on a despreading operation in the time domain.