There are multiple factors that will affect your wireless signal

1. Transmitting through objects – The material those objects are made out of will determine how much it impacts the wireless speed. Metal and concrete are the hardest for wireless signals to pass through, while wood, drywall and insulation are not as bad, but can still affect the signal.
2. Saturation of the Wi-Fi signal – Saturation occurs when there are numerous wireless routers surrounding your location.
3. Older Devices – The router will lower the signal quality to accommodate an older device, affecting all other devices on the network.
4. Device Location – If the router is having problems connecting to a device that is farther away, it will affect the communication to all other devices.