Synchronous Frequency Hopping Mesh Network Acquisition Channels
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Solution Overview
Problem
Existing frequency hopping spread spectrum (FHSS) implementations in mesh networks face challenges in synchronization, requiring clock circuitry and data overhead, especially in self-synchronous systems which need long preambles for device synchronization.
Innovation Solution
The system employs multiple frequency hopping sequences with coinciding acquisition channels, allowing network devices to synchronize clock circuitry and transmit broadcast messages efficiently, eliminating the need for continuous synchronization overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If self-synchronous FHSS mode is used to avoid clock circuitry and synchronization overhead, then device complexity and communication overhead are reduced, but a long preamble is required for channel scanning and locking, increasing data overhead and acquisition time
Solution Approach 1:
The frequency hopping sequence is segmented into two distinct parts: acquisition channels and data channels. Acquisition channels are specifically designated for initial synchronization and channel detection, while data channels are used for normal communication. This segmentation allows receivers to efficiently scan and lock onto channels during the acquisition phase without requiring complex continuous synchronization mechanisms, thereby reducing device complexity while maintaining reasonable acquisition time.
Solution Approach 2:
The system performs preliminary channel scanning and synchronization actions during the acquisition phase before actual data transmission begins. By pre-establishing channel locks and synchronization during this initial phase, the system avoids the need for continuous synchronization overhead during data transmission, reducing both device complexity and overall communication overhead while maintaining efficient data transfer.
2Reliability
If synchronous FHSS mode is used to maintain continuous synchronization, then time and frequency synchronization are improved, but clock circuitry and continuous data traffic are required, increasing device complexity and communication overhead
Solution Approach 1:
The communication protocol is segmented into an acquisition phase for synchronization and a data phase for communication. During the acquisition phase, receivers scan and lock onto channels to establish synchronization. Once locked, the system transitions to the data phase where pre-established synchronization is maintained without requiring continuous complex clock circuitry operations, thus achieving reliable synchronization with reduced device complexity.
Solution Approach 2:
The system uses the transmitted signal itself to maintain synchronization during data transmission. The continuous data traffic carries synchronization information that allows receivers to maintain time and frequency alignment without requiring separate dedicated synchronization signals or complex continuous clock circuitry operations, thereby achieving reliable synchronization with reduced overhead.
3Reliability
If a long preamble is transmitted in self-synchronous systems to enable channel scanning and locking, then channel acquisition reliability is improved, but data overhead increases
Solution Approach 1:
The transmission structure is segmented into an acquisition portion and a data portion. The acquisition portion contains the necessary preamble and synchronization information required for channel scanning and locking. By separating this from the data portion, the system ensures that only the minimum necessary overhead is transmitted for reliable channel acquisition, while the data portion carries actual communication information efficiently without redundant synchronization overhead.
Data Source
AI summary
Synchronous FHSS networks operating within mesh networks typically require a certain amount of network traffic to maintain time as well as for executing other functions, such as registration and neighbor discovery. The concepts presented in this disclosure provide a mesh network with enhanced communication capabilities without adding significant hardware or firmware costs to nodes within the network. The disclosed concept of using acquisition channels (frequencies) integrated within FHSS pseudo-random sequences speeds network responses to conditions like outage and restoration. Assignment of unique hop sequences by hop level or at time of manufacture can guarantee minimal network contention while minimizing system network traffic.