Multi Carrier Frequency Modulated Spread Spectrum System
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Solution Overview
Problem
Current communication systems face challenges in efficiently utilizing bandwidth and managing interference in multi-user environments, particularly in cellular networks, where spread-spectrum technologies like DSSS and OFDM have limitations in capacity and power control, leading to suboptimal performance in high-data-rate applications.
Innovation Solution
The Multi Carrier Frequency Modulated Spread Spectrum (MC FM SS) system combines FM modulation with direct sequence spread spectrum, utilizing multiple subcarriers and pseudo-random sequences to efficiently spread data in time and frequency, allowing for concurrent operation with OFDM systems and reducing power consumption in base stations and handsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spread-spectrum technologies like DSSS and OFDM are used in cellular networks, then bandwidth utilization is improved, but interference management in multi-user environments deteriorates
Solution Approach 1:
The patent segments the spread spectrum signal into multiple orthogonal subcarriers, each independently modulated and spread with unique pseudo-random sequences. This segmentation allows individual control of interference levels on each subcarrier while maintaining overall bandwidth efficiency, resolving the contradiction between bandwidth utilization and interference management.
Solution Approach 2:
The patent applies different modulation schemes, spreading factors, and power allocation strategies to different subcarriers based on local channel conditions. This localized optimization enables efficient bandwidth utilization in good channels while maintaining robust interference rejection in poor channels, simultaneously achieving both goals.
2Device complexity
If conventional spread-spectrum systems are used, then system complexity is reduced, but data rate capabilities deteriorate
Solution Approach 1:
The patent transitions from single-carrier spread spectrum to multi-carrier spread spectrum, adding the frequency dimension to the time-spreading mechanism. This dimensional expansion enables parallel data transmission on multiple subcarriers, dramatically increasing data rate while maintaining manageable system complexity through orthogonal frequency division.
3Reliability
If high power is used in base stations and handsets, then signal coverage is improved, but power consumption deteriorates
Solution Approach 1:
The patent dynamically adjusts transmission power parameters across different subcarriers and users based on channel conditions and quality of service requirements. This selective power allocation achieves adequate signal coverage only where necessary, minimizing overall power consumption in both base stations and handheld devices.
Data Source
AI summary
A transceiver block for multi-user, duplex, wireless access system architecture called Multi Carrier Frequency Modulated Spread Spectrum System (MC FM SS). Here symbols are transmitted at multiple subcarriers where each subcarrier is FM or phase encoded with the data. The data is spread in time/bandwidth using a pseudo-random (PN) sequence. In one realization the transmission is performed with the guard ring carriers and/or pilot subcarriers of an Orthogonal Frequency and Code Division Multiplexing, OFDM, system carried on the main RF carrier. The MC FM SS transmits the data symbol over N subcarriers, with each subcarrier encoded in frequency or phase. In Variable Spreading Factor Orthogonal Frequency and Code Division Multiplexing, VSF OFDM, by DoCoMo Japan with 1024 (which can increase to e.g. 6144) carriers are proposed in Long Term Evolution (LTE) 4G system in the down link direction and 2 carriers MC DS CDMA are used in the uplink direction.