er capacity in wireless networks, let's examine two techniques designed to improve the quality of wireless communications, or more specifically, the integrity of the data flow: Forward error correction (FEC)-FEC improves the reliability of digital radio sys- tems by combining redundant information with the transmission. The receiver, using a probability technique, can detect and correct a certain percentage of errors. However, because this requires more bits to be transmitted, it affects band- width efficiency. There are a variety of FEC techniques that vary in the coding rate, or the amount of additional information that must be sent, which affects the receiver's ability to correct errors. FEC coding refers to the ratio of uncoded to Spectrum Utilization coded bits. The improvement gained is generally expressed in improvements in signal-to-noise ratio or signal-to-interference ratio. Different coding rates affect the FEC overhead. The coding rate is expressed as a fraction that represents the number of uncoded bits input to the FEC encoder and the number of coded bits output to the transmitter. For example, 3/4 means 3 uncoded bits are sent as 4 coded bits, resulting in 33% overhead; 1/2 means 1 uncoded bit is sent as 2 coded bits, resulting in 100% overhead. In WLAN applications, OFDM transmission includes FEC coding that is spread across several subcarriers. If several of the subcarriers are lost, the receiver can reconstruct the information. Convolutional coding-This type of coding is used in 802.11 and 802.11g WLANs. This technique works by taking the transmitted bit sequence, selecting a group of the most recently occurring bits, distributing them into two or more sets, and performing a mathematical operation (convolution) to generate one coded bit from each set as the output. The receiver runs a comparison of the coded bit sequence and retains the best matches, which allows it to make a max- imum likelihood estimate of the correct decoded bit sequence. There are more complicated error correction techniques