eMTC Uplink Multi-User Multiplexing via Cyclic Shift and Spreading Code Segmentation
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Solution Overview
Problem
Current wireless communication systems face challenges in supporting multi-user multiplexing for machine type communication (MTC) devices with limited resources, particularly in LTE networks, where devices have restricted bandwidth and limited dimensions, making it difficult to share resources among multiple users without reducing data rates or transport block sizes.
Innovation Solution
The proposed solution involves identifying narrowband regions within a wider system bandwidth and assigning parameters such as cyclic shifts, spreading codes, and configurable spreading factors to user equipment (UEs) for uplink transmissions, allowing for efficient multiplexing of multiple UEs within a single resource block or fractional resource block, maintaining orthogonality and increasing user capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple UEs share the same narrowband region for uplink transmissions, then user capacity increases, but orthogonality between users deteriorates leading to interference
Solution Approach 1:
The patent segments the uplink transmission resources by dividing the narrowband region into multiple orthogonal resources. Each UE is assigned a unique combination of cyclic shift value and spreading code, creating segmented orthogonal transmission paths within the same physical resource block. This allows multiple UEs to share the narrowband region while maintaining orthogonality through mathematical separation of their signals.
Solution Approach 2:
The patent introduces additional dimensions for resource separation beyond traditional time-frequency domains. By applying cyclic shifts (phase rotation in frequency domain) and spreading codes (code division multiplexing), the system creates new orthogonal dimensions. This enables multiple UEs to transmit simultaneously in the same time-frequency resources while remaining distinguishable through their unique cyclic shift-spreading code pairs.
2Device complexity
If resource allocation is restricted to narrowband regions, then device complexity is reduced, but user capacity is limited
Solution Approach 1:
The patent makes the narrowband region universally support multiple users through multi-functionality. The same physical resource block can simultaneously serve multiple UEs by applying different cyclic shifts and spreading codes. This universal resource allocation mechanism allows the limited narrowband region to function as multiple independent channels, increasing user capacity without requiring additional physical resources or increasing device complexity.
Solution Approach 2:
The patent changes the parameters of the uplink transmission by applying variable cyclic shift values and spreading code sequences to different UEs. These parameter modifications transform identical physical resources into differentiated logical channels. The base station can dynamically assign different cyclic shift-spreading code parameter combinations to maximize user capacity within the constrained narrowband region while keeping the physical device structure simple.
3Quantity of substance
If spreading factor is increased to support more users, then user capacity increases, but data rate per user decreases
Solution Approach 1:
The patent implements dynamic resource allocation where the base station can flexibly adjust the spreading factor, cyclic shift values, and spreading code assignments based on current system conditions. This dynamic approach allows the network to optimize the balance between user capacity and individual data rates. When user capacity is prioritized, larger spreading factors are applied; when data rate is prioritized, smaller spreading factors with more efficient cyclic shifts are used, providing adaptive control over the capacity-rate tradeoff.
Solution Approach 2:
The patent applies partial spreading where the spreading factor can be selectively applied to different portions of the transmission or to different UEs based on their requirements. Not all users need to use the maximum spreading factor; instead, the system applies spreading selectively and partially to achieve sufficient user capacity while preserving higher data rates for users who need it, rather than uniformly reducing all data rates to support capacity expansion.
Data Source
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AI summary
Certain aspects of the present disclosure generally relate to wireless communications, and more specifically increasing user capacity through a frame structure which supports eMTC UL multi-user multiplexing. According to aspects, a UE may identify at least one narrowband region within a wider system bandwidth, determine at least one parameter assigned to the UE for transmitting symbols of a physical uplink channel in the narrowband region that are multiplexed with symbols transmitted by one or more other UEs, and transmit the physical uplink channel using the at least one determined parameter.