Functional Requirements Document (FRD) – Band Locking

Feature: Band Locking Management in zWAN SDWAN CPE
Version: 0.9

1. Objective

To enable control over the modem’s frequency band selection by allowing users to lock the modem to specific bands (LTE/NR/UMTS/GSM) for diagnostic, performance tuning, or compliance reasons.
Band locking improves stability, avoids poor-performing bands, and can aid in testing and carrier certification.

2. Functional Requirements

FR1: Band Listing

• The system must be able to query and list all bands supported by the modem and its current radio technology (e.g., NR5G, LTE, UMTS).
• The supported bands list must include:
  • Band number
  • Band name (e.g., LTE B3, NR n78)
  • Radio Access Technology (RAT)

FR2: Band Lock Configuration

• The system must support user-defined locking to one or more bands for a given RAT.
• Configurable options:
  • RAT type (e.g., NR5G, LTE, WCDMA)
  • Band numbers to lock (single or multiple)
  • Example: Lock to LTE Band 3 and Band 20 only.
  • Single band lock (e.g., only Band 3)
  • Multiple band lock (e.g., Band 3 + Band 5 + n78)
• Band configuration must persist across reboot.
• Notify user if band locking is unsupported on current hardware/firmware.

FR3: Locking/Unlocking Operation

• The user must be able to:
  • Enable band locking with a list of specified bands
  • Disable band locking (return to automatic selection)
• Changes must take effect without requiring system reboot, though modem restart may be required.

FR4: Validation & Status

• The system must:
  • Validate that specified bands are supported by the modem hardware
  • Provide API to query current band lock status
  • Report active bands used in current connection (e.g., via AT+QENG, AT+QNWINFO)
• It must not interfere with normal modem operation when band lock is not active.

FR5: Persistence

• Band locking settings must be stored in a persistent configuration in the database.
• After system or modem reboot, the previous band lock state and settings must be restored.

FR6: Status Display

• The system must provide a status report showing:
  • Currently active RAT
  • Active band(s)
  • Locked bands (if any)

FR7: Event Logging

• All band lock operations (apply, clear, fail) must be logged with timestamps.
• Logs must include success/failure and any modem responses.

3. Out of Scope

• Dynamic band switching based on signal quality (requires advanced modem coordination and policy engine)
• Signal metrics per band
• Auto-scan feature to detect optimal band based on signal quality
• Automatic band locking based on MCC/MNC (operator-specific band policies)