Wireless Ad-Hoc Networking System Design

1. System Objectives and Definitions

1. Objective: To achieve centerless interconnection and bidirectional wireless communication among multiple individual terminals without relying on external public base stations (4G/5G) or a central node.

2. Method: Utilize antennas + RF modules (AD936X) + baseband modules (FPGA modulation) to establish a physical layer communication link, completing basic packet transmission and status synchronization.

3. Features:

• Centerless, multi-hop self-organizing network (AdHoc)

• Fully hardware implementation (can be expanded to multi-node Mesh)

• Lightweight, low power consumption, quick deployment

2. System Architecture Diagram

The wireless communication between three nodes is shown in the diagram below (Figure 1).

Figure 1: Individual soldier self-organizing network communication schematic

3. Communication Technical Parameters

The self-organizing network communication parameters are shown in the table below (Table 1).

Table 1: Communication Parameter Table

Name	Parameter Value Description
Communication Mode	TDD bidirectional time-division communication
Modulation Method	BPSK/QPSK/64QAM (can be expanded to OFDM)
Bandwidth Setting	1～32 MHz (configurable by AD936X)
Frequency	600MHz/1.4GHz or custom (supports 70 MHz～6 GHz)
Data Rate	500 kbps～80 Mbps
Receiving Sensitivity	Better than –100 dBm (depends on modulation method)
Scrambling and Encryption	Can addM sequence scrambling + simple XOR encryption

4. Communication Process (Simplified Design)

The time slot rotation TDD for self-organizing network communication is shown in the table below (Table 2), with time synchronization achieved through fixed periods/predefined training symbols.

Table 2: Communication Process Table

Time Slot	Individual Soldier A Operation	Individual Soldier B Operation
T0	Transmit data frame	Receive mode
T1	Receive acknowledgment frame	Send acknowledgment frame
T2	Wait for the next frame	Wait for the next frame

5. Communication Protocol Frame Structure (Simplified Version)

The communication protocol frame structure for wireless self-organizing networks is shown in the table below (Table 3).

Table 3: Communication Protocol Frame Structure

[Header]	[Frame Header]	[Address]	[Data Field]	[CRC]	[Frame Tail]
4B	2B	1B	32B	2B	1B

• Header: Used for synchronization capture at the receiving end

• Frame Header: Distinguishes data/control/ACK types

• Address: Supports extended multi-node

• Data Field: Up to32B (expandable)

• CRC: Cyclic Redundancy Check

• Frame Tail: Indicates end of frame

6. Baseband Minimum Module Design

The functional description of the baseband minimum module design is shown in the table below (Table 4).

Table 4: Communication Protocol Frame Structure

Module Name	Functional Description
AD9361 SPI Configuration	Initialize AD9361 registers, set frequency, bandwidth, etc.
Baseband Modulation	Implement BPSK/QPSK/64QAM modulation, pulse shaping filtering; Modulate data into IQ symbols (BPSK/QPSK/64QAM), output to AD9361
Receive Demodulation	Receive IQ data from AD9361, perform matched filtering and symbol decision
Packetization and Depacketization	Package data → Add start/stop bits/verification/CRC; Add frame header, frame tail, CRC, etc. structure for reliable communication
TDD State Machine	Control transmit/receive switching, ensure communication polling rhythm synchronization
UART Module	Interact with user terminal, output received data and display status

7. RF Unit Configuration (Typical Parameters)

The functional configuration of the minimum RF front-end module design is shown in the table below (Table 5).

Table 5: RF Front-End Functional Configuration

Name	Parameter Configuration
Center Frequency	600MHz/1.4GHz or custom (supports 70 MHz～6 GHz)
Bandwidth	32 MHz
Analog Gain Mode	Automatic gain/fixed gain (fixed during testing)
TDD Control Interface	GPIO control, TDD synchronization window adjustable
Receive/Transmit Mode	Utilize TDD synchronization control, using timing or GPIO trigger
Gain Control	Fixed gain or automatic gain mode (AGC)
Calibration	Use initialization scripts provided by ADI for calibration

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