The second step to improve WCDMA coexistence is to apply appropriate filtering and mitigation techniques to reduce or eliminate the impact of coexistence issues. These can be divided into two categories: hardware and software. Hardware techniques refer to the physical components and devices that can enhance the signal quality and isolation of WCDMA. Examples of hardware techniques include using bandpass filters, notch filters, duplexers, circulators, isolators, and directional antennas. Software techniques refer to the algorithms and protocols that can optimize the signal processing and resource allocation of WCDMA. Common examples of software techniques are adaptive modulation and coding, power control, handover, interference cancellation, interference coordination, and carrier aggregation. These techniques can help to filter out unwanted signals and noise, improve the SINR of WCDMA, reduce power consumption and heat dissipation of WCDMA devices, increase spectral efficiency and capacity of WCDMA networks, as well as adjust the signal parameters and resources according to the channel conditions and traffic demand.