# Shapley's Value as a Resource Optimization Strategy for Digital Radio Transmission over IBOC FM
## 2 Materials and Methods
### Audio Source Encoding and Compression in IBOC  
The human voice (analog), to be transmitted efficiently through any medium in a digital format, requires a transformation process known as \"digitization\", which is performed by a device called CoDec (Codec/Decoder), where each transmission mechanism may have several alternatives of Codecs, as appropriate. Considering that, for the transport of voice information, it is necessary to assemble the information in the form of packets or PDUs, the required bandwidth will depend on the overhead generated by these packets [23].  
IBOC uses a Perceptual Audio Coder (PAC) encoding algorithm from Lucent Technologies, which is a coding method that uses advanced signal processing techniques and the use of psychoacoustic models, through which it is possible to obtain a high compression of the source signal. It uses a sampling frequency of 44.1 kHz, 16 bits of resolution, and, by means of a bank of special filters, it obtains a complete description of the audio signal whose processing facilitates an auditory perception analysis for its quantification and subsequent coding, optimizing the transmitted information to the extreme [24]. One of the main benefits of PAC is that it allows audio compression at different bit rates, even as low as 6 kbps. When the channel quality is 6 to 8 kbit/s, the result is similar to an AM signal. For a channel capacity between 16 and 24 kbit/s, the result is similar to an FM signal, and when a capacity of 32 or 64 kbps is available, the audio quality is considered very similar to what can be obtained on a compact disc. In the particular case of IBOC FM, it is possible to perform transmission processes of high-quality audio channels (comparable to compact disc) with transmission speeds of only 96 kb/s. In turn, the IBOC FM system (standardized as NRSC-5) does not propose a specific source encoder, but makes use of nominal and minimum rates of the source encoders for each of the operating modes [25].  
IBOC utilizes a Perceptual Audio Coder (PAC) encoding algorithm developed by Lucent Technologies. This coding method employs advanced signal processing techniques and psychoacoustic models to achieve high compression of the source signal, operating at a sampling frequency of 44.1 kHz with 16 bits of resolution and utilizing a bank of specialized filters. PAC provides a comprehensive description of the audio signal, facilitating auditory perception analysis for quantification and subsequent coding. This optimization of transmitted information allows for significant compression, even at bit rates as low as 6 kbps [24].  
PAC offers several benefits, including the ability to compress audio at different bit rates. For channel quality ranging from 6 to 8 kbit/s, the result resembles an AM signal. In the case of channel capacities between 16 and 24 kbit/s, the quality is akin to an FM signal, while capacities of 32 or 64 kbps yield audio quality similar to that of a compact disc. Remarkably, in the context of IBOC FM, high-quality audio channels comparable to compact discs can be transmitted at speeds as low as 96 kb/s. It is noteworthy that the IBOC FM system (standardized as NRSC-5) does not propose a specific source encoder but instead relies on the nominal and minimum rates of the source encoders for each operating mode [25].