Software And Firmware
Many modern hardware devices have embedded software, commonly known as firmware, which allows the manufacturer to patch bugs or add features. Some common examples of firmware you may be familiar with are cellular phone ROMs and your motherboard's BIOS. In most cases, firmware is read-only to the device, and specific steps must be followed in order to perform an upgrade. The read-only nature of firmware provides a layer of security by helping ensure malicious code doesn’t get applied to the device. Firmware updates should be handled with care, as misapplied firmware updates are a common reason for device failure (known as bricking).
In general, the biggest difference between a wireless range extender and a wireless router or access point is its firmware, as this determines the capabilities that are enabled on the device and ultimately drives the hardware. Unfortunately, firmware is rarely interchangeable between devices, so don’t plan on applying a router firmware to your range extender anytime soon.
For the adventurous types there is an open-source firmware alternative for Wi-Fi routers, which is beginning to offer support for range extender hardware. DD-WRT is a Linux distribution designed for use on wireless networking hardware. A list of supported devices is maintained on the project website, so check there in order to determine if your hardware is supported. If you’d prefer to re-purpose an old router to perform range extender duties, DD-WRT offers comparable functionality. Be aware that flashing a custom firmware to your device could potentially void your warranty.