NFC Anti-Collision Using Vector-Based Time Slot Allocation
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Solution Overview
Problem
In Near Field Communication (NFC) systems, collisions between response signals from multiple listen devices can corrupt Unique Identifiers (UIDs) and other signal parts, leading to identification delays and potential failures in the initiation process, especially with the probabilistic collision resolution methods being prolonged and unreliable, while deterministic methods are slow.
Innovation Solution
The implementation of an NFC anti-collision method where the initiator device broadcasts a poll request signal with a sequence of introduction vectors coupled to allocation vectors, allowing listen devices to compare received introduction vectors with embedded ones and respond at times determined by the allocation vectors, ensuring non-overlapping time slots and preventing bit-level collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If probabilistic collision resolution method is used, then device complexity is reduced, but identification reliability deteriorates and process duration increases
Solution Approach 1:
The patent applies preliminary action by pre-assigning dedicated time slots to each listen device based on their introduction vectors before the actual communication begins. The initiator device pre-calculates and transmits allocation vectors that map each device's introduction vector to a specific time slot, ensuring that devices know in advance when to transmit without collision. This eliminates the need for complex probabilistic collision resolution while guaranteeing reliable identification.
2Reliability
If deterministic collision resolution method is used, then identification reliability is improved, but identification speed deteriorates and process duration increases
Solution Approach 1:
The patent applies segmentation by dividing the identification process into parallel independent time slots, each dedicated to a specific listen device. Instead of sequentially querying devices one by one (deterministic method), the system segments the time domain so that multiple devices can be identified simultaneously in different slots. This maintains 100% reliability through dedicated slots while dramatically improving speed through parallel identification.
Solution Approach 2:
The patent transitions from the traditional sequential time dimension to a two-dimensional structure by introducing device-specific time slot allocation based on introduction vectors. Each device is assigned a unique time slot coordinate in the time domain, creating a structured matrix where rows represent devices and columns represent time slots. This dimensional organization enables parallel identification while maintaining deterministic reliability.
3Productivity
If multiple listen devices respond simultaneously, then communication efficiency is improved, but signal collision occurs and identification reliability deteriorates
Solution Approach 1:
The patent applies periodic action by organizing device responses into regular, non-overlapping time slots that repeat in a structured sequence. Each listen device is assigned a specific periodic time slot based on its introduction vector, creating a rhythmic pattern where devices transmit in turn without collision. This periodic structure maintains high communication efficiency by enabling multiple devices to respond while eliminating signal collision through precise temporal separation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures efficient and reliable identification of all listen devices by avoiding signal collisions, reducing identification delays, and achieving a 100% successful identification rate without the need for prolonged processes or extensive recording of introduction vectors on the initiator device.
Implementation Method 1
The initiation process starts by generating an RF field at 13.56 MHz
Implementation Method 2
The listen device load modulates the existing RF field to achieve communication
Data Source
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AI summary
In near field communication between an active initiator (30) and a plurality of passive listen devices (40) the initiator device (30) must obtain a unique identity code from each listen device (40) in range by means of an initialisation process. After establishing an RF field (M) and thereby activating the listen devices the initiator (30) transmits a poll request signal. The poll request signal consists of a sequence of couples. Each couple comprises an identification vector (IVC) and an allocation vector (AVC). Each listen device includes a memory (42) which records control code and an embedded introduction vector (IVL). Each listen device receives the entire poll request signal, and compares each received introduction vector (IVC) with its embedded introduction vector (IVL). When a match is found the listen device calculates a time slot for transmission of its poll response signal based on the allocation vector coupled with the matched introduction vector. The time slot calculated will not overlap with any other time slot so that bit level collisions in the poll response signals will be avoided.