Acta Metallurgica Sinica(English letters) ›› 2013, Vol. 20 ›› Issue (3): 20-25.doi: 10.1016/S1005-8885(13)60043-6

• Wireless • Previous Articles     Next Articles

Achievable rate region for the multiple-access channel with multiple cognitive transmitters


  1. Key Lab of Universal Wireless Communication, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China
  • Received:2012-08-24 Revised:2013-01-18 Online:2013-06-30 Published:2013-06-26
  • Contact: Yuchen Guo
  • Supported by:

    This work was supported by the National Basic Research Program of China (2009CB320401), the National Natural Science Foundation of China (61101117), Research Funds for Doctoral Program of Higher Education of China (20090005110003), National Key Scientific and Technological Project of China (2010ZX03003-001, 2012ZX03004005-002), Fundamental Research Funds for the Central Universities (BUPT2012RC0112).


A scenario where one ‘dumb’ radio and multiple cognitive radios communicating simultaneously with a common receiver is considered. In this paper, we derive an achievable rate region of the multiple-user cognitive multiple-access channel (MUCMAC) under both additive white Gaussian noise (AWGN) channel and rayleigh fading channel, by using a combination of multiple user dirty paper coding (DPC) and superposition coding. Through cognition, it is assumed that the secondary users (SUs) are able to obtain the message of the primary user (PU) non-causally beforehand. Using this side information, the SUs can perform multiple user DPC to avoid the interference from the SU. Besides, the SUs can also allocate part of their transmit power to aid the PU, using superposition coding. Therefore, the capacity region of traditional multiple-access channel (MAC) can be enlarged. Moreover, some asymptotic results are shown as the number of SUs increases. In the AWGN case, it is illustrated that the maximum achievable rate of the PU grows logarithmically with the increase of the number of SUs, whereas in the Rayleigh case, we show that the cognitive gain will increase with the decreasing of the channel signal to noise ratio (SNR).

Key words:

cognitive radios, MAC, superposition coding, DPC