Presentation on theme: "Derives the optimal achievable rate for MISO secondary users under coexistence constraints Proposes practical strategy for cognition and cooperation in."— Presentation transcript:
Derives the optimal achievable rate for MISO secondary users under coexistence constraints Proposes practical strategy for cognition and cooperation in MIMO system Finds out the relation between secondary user’s achievable rate and primary user’s power allocation scheme Cooperation and cognition in MIMO cognitive networks Ying Chang, Andrea Goldsmith Decompose the MIMO channel into orthogonal components and leverage secondary user’s beneficial and deteriorative impact to the primary user. Introduce cooperation to broadcast system In MIMO networks, we are more flexible to deal with interference MAIN ACHIEVEMENT: HOW IT WORKS: Secondary user has non causal knowledge of primary users’ transmission and performs cognition together with cooperation to compensate the interference to primary receiver. We study the cases with MISO and MIMO secondary transmission system and multiple primary receivers. ASSUMPTIONS AND LIMITATIONS: Primary users’ transmission rate is unchanged In literature, achievable rates of single-antenna secondary user is well studied How to do cooperation and cognition with multiple antennas and multiple primary users is our main focus Study multiple primary receivers with multiple antennas Information theoretical bounds on MIMO cognitive networks IMPACT NEXT-PHASE GOALS ACHIEVEMENT DESCRIPTION STATUS QUO NEW INSIGHTS MISO, single primary user MISO multiple primary users MIMO Single primary user How to utilize new degrees of freedom brought by MIMO technique? Single-primary-user cognitive network Multi-primary-user cognitive networks System model We consider a MIMO cognitive network as in the following picture. The cognitive transmitter determines its codeword as a function of the messages m p and m c. MISO cognitive user In this case, we have a MISO cognitive transmission pair. We propose a optimal transmission strategy for cognitive user through project the beamforming vector onto orthogonal and aligned channel components. The relation between primary user’s rate and cognitive user’s rate is illustrated as follows: To not impact the transmission rate of primary (licensed) user, the cognitive user performs cooperation to compensate its interference to the primary user. Encoding rule for the cognitive user: The cognitive encoder acts in two stages. For every message pair (m p, m c ), the cognitive encoder first generates a codeword for the primary message m p. In the second stage, the cognitive encoder generates a codeword for m c using Costa pre-coding. The two codewords are superimposed to form the cognitive codeword. MIMO cognitive user In this case, we have a MIMO cognitive transmission pair. We propose a two sub-optimal transmission strategies for cognitive user: Direct Channel SVD (D-SVD) The precoding matrix is obtained from the SVD of the cognitive user’s channel Projected Channel SVD (P-SVD) The cognitive user’s channel is projected onto the null space of the channel between cognitive transmitter and primary receiver. Than SVD is performed on the projection. Under different power constraint, the performances of the two strategies are compared with the MIMO channel capacity. In this case, the primary transmitter broadcasts to several primary receivers. To maintain the capacity region of primary users, the cognitive user cooperate with each primary receiver. Power allocation scheme is developed for MISO and MIMO cognitive user. When the capacity region of primary broadcast channel is achieved the transmission rate for cognitive user is illustrated as follows: Interestingly, we find out the relation between primary users’ sum rate and cognitive user’s transmission rate is non monotonic.