Compression of associated signaling for adaptive multi-carrier systems

Link adaptation technology has been introduced in new generation transmission systems, such as 3G and 4G, optimizing both their throughput and their power consumption. Adaptation of the 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 to increase the overall system capacity (more users, more available bandwidth). The 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 effects, and in frequency due to multipath delay spread. We intend to exploit this twofold redundancy to decrease signaling information load. An adaptive lossless compression system for an optimized compression performance and complexity is proposed, giving much higher compression ratio than the existing LZW bit loading algorithm (Lestable, T. and Battelli, M., 2002).