CAZAC Walsh Code Encoding for Wireless Terminal Capacity
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Solution Overview
Problem
Conventional methods for encoding control signals in 3G mobile communication systems limit the number of terminal stations that can be assigned different codes, leading to inefficiencies in upstream link control signal transmission.
Innovation Solution
A wireless terminal and base station apparatus that employs a phase-shifting operation on a constant amplitude zero autocorrelation code combined with orthogonally crossing codes to encode and decode control signals, allowing for increased assignment of unique codes to multiple terminal stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CAZAC code with different phase shift amounts is assigned to each terminal station, then terminal stations can be differentiated, but the number of terminal stations that can be assigned codes is limited
Solution Approach 1:
The patent divides the code assignment into two independent parts: a first code (CAZAC code) that is shared among all terminal stations, and a second code (Walsh code) that is uniquely assigned to each terminal station. This segmentation allows the system to differentiate between multiple terminal stations using a combination of codes rather than requiring unique first codes for each station, thereby increasing the number of assignable terminal stations.
Solution Approach 2:
The patent merges the first code (CAZAC code with phase shift) and the second code (Walsh code) into a combined encoding structure. The control signal is encoded by multiplying the first code and the second code, creating a composite code that combines the benefits of both: the phase shift provides terminal differentiation while the Walsh code provides orthogonal separation, enabling more terminal stations to be assigned uniquely identifiable codes.
2Productivity
If unique codes are assigned to each terminal station for upstream control signal transmission, then transmission efficiency is improved, but the system capacity is limited by the number of available codes
Solution Approach 1:
The patent transitions from a one-dimensional code assignment (single code per terminal) to a two-dimensional code assignment structure. Instead of assigning a unique code from a limited set to each terminal, the system uses a combination of a shared first code and a second code, effectively adding a dimensional layer to the code space. This allows the system to differentiate between terminal stations using the combination of codes rather than being limited by the size of the original code set.
Data Source
AI summary
Both a wireless terminal apparatus and wireless base station apparatus are provided that can, in an operation of encoding the control signals of the upstream link transmitted from the multiple terminal stations while encoding with regard to each of the terminal stations, increase a number of the terminal stations to which different codes are respectively assigned. A wireless terminal apparatus includes: an encoding information receiving portion receiving encoding information which is used at the wireless terminal apparatus from the base station; a phase-shifting unit which conducts a phase-shifting operation on a predetermined first code based on the encoding information; a code selection unit which, based on the received encoding information, selects a second code from multiple codes orthogonally crossing each other; and a control signal encoding portion which conducts an encoding operation on the control signal that is going to be transmitted to the base station by using both the first code on which the phase-shifting operation has been conducted and the second code.