Compression of bit loading power vectors for adaptive multi-carrier systems

Link adaptation technology has been introduced in new generation transmission systems such as 3-G or 4-G, optimizing both their throughput and their power consumption. The adaptation of radio configuration requires information about the radio link quality. The information must be exchanged between the access point and the mobile terminal, leading to an associated signaling load, whose amount may decrease the system transmission efficiency. A mechanism for reducing the amount of signaling information has to be designed for increasing the overall system capacity (more users, more available bandwidth). This paper addresses multi-carrier systems whose link adaptation is carried out by means of bit loading algorithms. However, the associated signaling load increases quickly with the number of sub-carriers, modulation schemes and users. These bit loading vectors are considered a-priori known at the receiver, and almost no literature concerning transmission of such information is available. In realistic transmission systems, correlation exists in time due to Doppler effect, and in frequency due to multi-path delay spread. We intend to exploit this twofold redundancy to decrease the signaling information load related to the power vector data for bit loading. A compression system for the power vector data of the bit loading is proposed. The performance of such compression system is then evaluated on real power vector data.