In this chapter, the design of piecewise fuzzy \(H_{\infty }\) filters for discrete-time T-S fuzzy systems has been studied without considering the effect of system delay on system performance. However, it should be noted that network delay is usually considered to be one of the main causes of the performance degradation, oscillation or even instability of the engineering systems [1–3]. Therefore, it is necessary to conduct research on the systems with delay, and in the past few decades, scholars have invested extensive attention and achieved fruitful results in addressing delay issues, such as Refs. [4–8].