Channelization Code Assignment for HPSK Overshoot Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for assigning channelization codes in CDMA systems face challenges with Peak to Average Ratio (PAR) increase due to overshoot in HPSK modulation, particularly when the number of multiplexed data channels is five or more, and cannot effectively handle channels like HS-DPCCH with different gain factors.
Innovation Solution
A communication apparatus with a controlling unit that calculates and determines optimal channelization code combinations to minimize overshoot by considering phase variations between chips, assigning codes such as C4,2 and C4,3 to channels with the largest gain factors and C4,1 or C4,0 to remaining channels based on spreading factor and data amount, while adapting to the presence or absence of HS-DPCCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional channelization code assignment methods are used, then the system can support multiple data channels, but the Peak to Average Ratio increases due to overshoot in HPSK modulation
Solution Approach 1:
The patent changes the parameter of channelization code selection by introducing gain factor as a criterion. The controlling unit calculates gain factors for each data channel and assigns channelization codes based on these gain factors, specifically selecting codes that minimize phase variation when gain factors differ significantly. This parameter change in the selection criterion resolves the overshoot issue while maintaining support for multiple channels.
Solution Approach 2:
The patent applies preliminary action by calculating gain factors for all data channels before assigning channelization codes. The controlling unit performs this calculation and determination in advance, selecting optimal code combinations that prevent overshoot before transmission occurs. This preliminary optimization ensures minimal PAR increase while supporting the required number of multiplexed channels.
2Ease of operation
If channelization codes are assigned without considering gain factor, then the assignment process is simple, but the system cannot effectively handle channels with different gain factors like HS-DPCCH
Solution Approach 1:
The patent introduces gain factor as a new parameter in the channelization code assignment process. The controlling unit calculates gain factors for each data channel and uses this parameter to determine optimal code assignments. This adds adaptability to handle channels with different gain factors while maintaining automated operation through the controlling unit's calculations.
Solution Approach 2:
The patent makes the channelization code assignment dynamic by adapting to the specific characteristics of each data channel. The controlling unit calculates gain factors and determines code assignments based on these calculated values, allowing the system to dynamically adjust to different channel configurations including HS-DPCCH with its specific gain factor requirements.
3Object-generated harmful factors
If channelization codes are assigned to minimize phase variation, then overshoot is reduced, but the code selection becomes more complex
Solution Approach 1:
The patent uses gain factor as a key parameter to simplify the complex optimization problem. By calculating gain factors for each channel and using these values to guide code selection, the system reduces phase variation and overshoot without requiring complex iterative optimization. The gain factor parameter provides a straightforward criterion for selecting appropriate channelization code combinations.
Data Source
AI summary
It is an object to propose a way to assign channelization that is applicable to a case in which the number of multiplexing of DPDCHs (Dedicated Physical Data Channels) is at least five for overshoot of HPSK (Hybrid Phase Shift Keying) modulation. Assignment of channelization codes is set as follows. For all possible combinations of channelization assigned to given data channels and control channels, a transition θ1 from the first chip to the second chip and a transition θ2 from the third chip to the fourth chip are obtained. For each transition, 0 degrees or 180 degrees is desirable, and 90 degrees is the worst, so that a combination is obtained in which squares of sine of respective transitions become the smallest. Consequently, by obtaining a combination that makes sin2 θ1+sin2 θ2 the smallest, the one that is close to the most desirable combination can be obtained.