Research On Interference In High-Density Wi-Fi Networks

As the most popular Wireless Local Area Network (WLAN), Wi-Fi network has characteristics of wide coverage, high speed transmission, and easy deployment. So it is widely used in the fields of education, healthcare, entertainment and transportation. Each individual can set up Access Points (AP) in the corporation, home and public areas on demands, to surf the Internet anytime anywhere. On the other hand, Wi-Fi networks can offload data streams from3G network, which reliefs the pressure of mobile communication network. All of these result in density deployment of APs and severe interference. And these problems can be settled by allocating wireless resource reasonably. To overcome the limitations of current research, this thesis focuses on the interference problem caused by high density of Wi-Fi networks in the scenarios of downlink and uplink respectively.For the downlink of Wi-Fi networks, the thesis presents a joint algorithm of channel allocation and power control, in which each AP operates independently. Firstly AP selects its channel from the thirteen overlapping channels. Its basic concept is that neighboring APs have large channel spacing. Furthermore, AP with good channel quality of downlink estimates the low threshold of transmitting power through RSSI value and wireless channel model, which guarantees the smooth communication. According SINR balance principle, AP calculates power value ranging from the default value to the low threshold. For every user associated with the AP, AP can get the power value respectively and choose the maximum value as its transmitting power. Simulation results demonstrate that our presented algorithm enhances performance greatly in light of throughput, interference and power. Furthermore, it also solves the problem of coverage hole caused by power control.For the uplink of Wi-Fi networks, the thesis proposes a joint algorithm of user access and power control, which each user operates independently. With the consideration of the number of associated users and RSSI value, a new concept of AP usability is proposed. In the algorithm, the user calculates AP usability for APs within its coverage and accesses the AP with maximal AP usability. The user which has good link quality of uplink tunes transmitting power based on SINR values within ranges depending on RSSI and wireless transmission model. It has been verified that the presented algorithm can reduce the interference between users effectively and enhance the throughput of uplink by the way of simulating.In addition, it also saves energy of mobile terminal and balances load.