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For a three user Gaussian multiple access channel (MAC), we propose a new superposition block Markov encoding based cooperation scheme. Our scheme allows the three users to simultaneously cooperate both in pairs, and collectively, by dividing the transmitted messages into sub-messages intended for each cooperating partner. The proposed encoding and decoding at the transmitters take into account the...
Besides delivering high data rates in a point-to-point scenario, multi-input multi-output (MIMO) antenna techniques can broadcast personalized data to multiple users in the point-to-multipoint scenario. Zero-forcing beamforming (ZFB) is a suboptimal but simple MIMO broadcast technique, which basically decouple the MIMO channel into many parallel single- input single-output (SISO) channels. In this...
We study a cognitive network consisting of multiple cognitive users communicating in the presence of a single primary user. The primary user is located at the center of the network, and the cognitive users are uniformly distributed within a circle around the primary user. Assuming a constant cognitive user density, the radius of this circle will increase with the number of users. We consider a scheme...
In practical systems, due to the time-varying radio channel, the channel state information (CSI) may not be known well at both transmitters and receivers. For most of the current multiuser multiple-input multiple-output (MIMO) schemes, they suffer a significant degression on the performance due to the mismatch between the true and estimated CSI. To alleviate the performance penalty, a robust downlink...
This paper considers zero-forcing beamforming (ZFBF) at the transmitter for a downlink multi-user multiple-input single-output (MU-MISO) system. Transmit beamforming as a simple yet efficient technique can exploit the benefits of multiple transmit antennas provided that the instantaneous channel state information (CSI) is known at both sides of transmission link. In order to have such improvements,...
Subcarrier allocation for multiuser MC-DS-CDMA systems is much more complicated when compared to OFDM systems due to the presence of multiple access interference (MAI) when multiple users transmit simultaneously on the same subcarrier. In this paper, we propose a novel suboptimal algorithm to adaptively allocate subcarriers for MC-DS-CDMA systems, with the effect of MAI taken into consideration. An...
Multi-channel multi-radio WMNs are promising solutions for overcoming the limited capacity problem in multi- hop wireless networks. In these WMNs, each mesh router is equipped with multiple radios and each radio operates in a distinct frequency band. Channel assignment is the key issue that should be addressed in these networks. In this paper we propose a channel assignment scheme with the objective...
Opportunistic scheduling has been known as one of the possible ways of exploiting multi-user diversity, which comes from the time-varying propagation characteristics and broadcast nature of wireless radios, to improve communication efficiency and reliability. Multi-channel multi-radio technology has offered great opportunity in designing wireless network MAC protocol to utilize all kinds of resource...
Imperfect channel state information (CSI) at the transmitter is one of the major challenges that the downlink multiuser multiple-input-multiple-output (MU-MIMO) technology faces in real applications. It will lead to increased co- channel interference (CCI) among users and deteriorate the capacity of MU-MIMO seriously, especially at high signal-to- noise-ratios (SNRs). In this paper, we propose an...
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