CDMA Spreading Code Sharing via Time Division Multiplexing

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Solution Overview

Problem

CDMA telecommunications systems, such as WCDMA, face limitations in accommodating more than N users in a cell without increasing the spreading factor or using secondary scrambling codes, as each spreading code is allocated exclusively to a user, restricting the effective code resource.

Innovation Solution

A method where multiple telecommunications apparatuses share spreading codes through a Time Division Multiplexing (TDM) scheme, where a first apparatus selects a group of second apparatuses to share spreading codes, performing spreading operations in turns, allowing for increased effective code resource utilization without secondary scrambling codes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If spreading codes are allocated exclusively to users, then code resource management is simplified, but the number of users that can be accommodated in a cell is limited to N

Engineering Contradiction:

Improvecode resource management complexityVSAvoidnumber of users accommodated

Core Design Contradiction:

Device complexityVSQuantity of substance

Solution Approach 1:

Multiple users are merged into a single spreading code allocation, where K users share one spreading code through time-division multiplexing. This combining approach allows the system to accommodate more users than the number of available spreading codes by having users share codes in a coordinated manner.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The spreading code allocation is made dynamic through turn-based assignment, where the first telecommunications apparatus assigns different spreading codes to different users at different time intervals. This dynamic allocation allows the system to adapt to varying user demands and accommodate more users than static allocation would permit.

Inventive Principle:

Principle #15Dynamics

2Quantity of substance

If spreading factor is increased to accommodate more users, then user capacity increases, but system complexity and interference management become more difficult

Engineering Contradiction:

Improveuser capacityVSAvoidsystem complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The user population is segmented into groups, where each group shares a specific spreading code. The first telecommunications apparatus manages these segments by assigning users to different time slots with different spreading codes, thereby increasing capacity without increasing the spreading factor or overall system complexity.

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If secondary scrambling codes are used to increase user capacity, then more users can be accommodated, but interference from secondary scrambling codes increases

Engineering Contradiction:

Improveuser capacityVSAvoidinterference from secondary scrambling codes

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The system employs periodic time-division multiplexing where users transmit in alternating time slots using the same spreading code. This periodic structure eliminates the need for secondary scrambling codes, as the time-division approach inherently separates user signals, reducing interference while maintaining increased user capacity.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS9831908B2Telecommunications methods facilitating sharing of spreading codes

Publication Date: 2017.11.28 MEDIATEK INC

AI summary

Embodiments of the invention provide telecommunications methods that facilitate sharing of spreading codes. According to one of the embodiments, a first telecommunications apparatus first selects a plurality of second telecommunications apparatuses to share at least one spreading code. Then, the first telecommunications apparatus uses each of the at least one spreading code to perform spreading operations for the second telecommunications apparatuses by turns repetitively.