There are several reasons for this.
1. The router is faulty
This is the most common problem, it may just be a temporary connection stuck in a dead loop, the simplest solution is to unplug the router power interface, let the router restart, this will solve 90% of the router caused by the problem. Of course, it is also possible that the router hardware is faulty, which can only be sent for repair. Now the router price before 50-200 yuan, not expensive.
In addition, there may be a router configuration problem, which depends on whether the router itself can connect to the network, if it can not link to the network, it is necessary to reconfigure the router.
2. Connect multiple devices at the same time
Generally, this problem occurs in the work environment, or in public places such as cafes and shopping malls that provide free wifi. If you do not have the permission to change the router Settings, you can only try to avoid the Internet at peak times, or connect to the network in advance. If there is an IP conflict, IP allocation must be performed on each connected device in the router to avoid mutual impact.
In addition, there are some individual cases, such as the Tianyi router presented by China Telecom, which was forcibly locked by the official routing function, so if you want to use the Tianyi router for wifi Internet access, you must unlock it first.
3, beyond the signal coverage
The wireless signal of the wireless router will be weakened by external influences, the most direct is the distance, and the signal of the ordinary router will become very poor beyond ten meters. Therefore, it is recommended to stay as close to the signal source as possible when connecting to wifi to enhance the wifi signal. In addition, if there is a dielectric barrier between you and the wireless router, such as a wall, the signal will also become poor.
4. The wireless network adapter is faulty
The mobile phone receives wifi signals by relying on the wireless network card in the mobile phone. Some mobile phone wireless card has been eliminated or seriously aging, will cause poor wifi signal reception, or even a phone call will lead to wireless network disconnected, this situation can only be repaired by the maintenance center to solve.
5. Baseband or ROM problems
Baseband is responsible for communication modules, often a mobile phone has multiple basebands to choose from. If you brush an inappropriate baseband when you brush ROM, it may cause your wifi connection to be abnormal, and even SMS can not be sent out, and phone calls can not be made. In addition, if the ROM itself is not perfect, then there will be the problem of abnormal wifi connection. For example, as soon as Android 4.1 was released, some machine friends brushed the beta version of CM10(third-party ROM based on 4.1 framework), and the result was unable to connect to wifi, which must be re-brushed a more perfect ROM to solve.
Mobile phone can not connect to the wireless card there are two cases, the first case is that the wireless card can not be used. The second case is that the phone can not connect to wifi, you can change the wifi connection to see whether the phone's wifi problem