that the energy per bit relative to the noise floor improves. However, each bit is now carrying more information SO if the bit is received in error proportionately more information is lost. Even with all of the adaptive process in an LTE radio network, the radio channel is still an error-prone channel when compared to broadcast networks and the errors have a habit of occurring in bursts that can translate at higher layers of the protocol stack into packet errors and retries that are disruptive to compression techniques that rely on memory - the result is error extension. Additionally, higher-order compression is computationally complex, power hungry and time hungry - the extra clock cycles needed to compress a signal in digital TV can be easily accommodated in the power and time budget both at the transmitter and the receiver (which is normally connected to the mains). This is not the case in a mobile broadband network. Interrelationship of the Physical Layer with Other Layers of the OSI Model Doing higher-order compression on the user equipment TX path for instance will introduce compression delay, absorb energy and require performance parameters such as error vector magnitude to be more closely controlled (which in turn will have an impact on the user's energy budget). Compression techniques have generally been developed either to maximise broadcast trans- mission efficiency (DVB T as an example) or memory bandwidth efficiency (MP3 and MP4). These efficiency gains do not translate comfortably into a mobile broadband channel. Im- provements in compression techniques may have some beneficial impact on future spectral efficiency but these benefits are likely to be marginal rather than fundamental and less useful than RF performance and baseband performance gain. 3.7.2 MOS and QOS Measuring the quality of voice codecs is done on a well-established mean opinion score (MOS) basis and similar processes are being agreed for video perceived quality benchmarking. Note that if actual video quality stays the same but audio