Channel Capacity of Multi User TR-MIMO-UWB Communications System Tran Ha Vu† , Nguyen Thanh Hieu∗ , Ho Duc Tam Linh† , Nguyen Thuy Dung and Le Van Tuan †Faculty of Electronics and Telecommunications, Hue University ∗School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 University of Engineering and Technology, Vietnam National University, Hanoi Email: vu.tran@aricent.com, nguyenth@ntu.edu.sg response (CIR) of an environment where a base station (BS) is forwarded to any user MU-MIMO UWB TR system has been proposed as a hot research direction [5], [6], [11] and [12].In [7], there are results about channel capacity of MU-SISO UWB TR and MU-MISO UWB TR systems (without correlation among antennas), however, that of MU-MIMO UWB TR system still have not been presented yet In this paper, we will investigate the operation capability of this system in different noisy environments with correlation among antennas Especially, we achieve an interesting result that the transmit correlation affect achieved capacity more significantly than receive correlation does When the correlation factor among receive antennas is too high (approximately 0.9), if we increase a number of receive antennas then the achieved capacity is virtually unchanged Meanwhile, with correlation factor among transmit antennas is higher than 0.7 (MR = 2), if we increase a number of transmit antennas the channel capacity will be decreased In addition, the UWB system in combination with MIMO and TR operates better in highly noisy environment, reduces the influence of multi-path fading effect and provides user with stable traffic even when the noise of environment changes The rest of article is organized as follow: part II is MUMIMO UWB TR system description, part III is channel capacity analysis of the proposed model, part IV is numerical results, part V is conclusion of problems Abstract—Ultra wideband (UWB) system using multi antennas and time reversal (TR) possesses capability of multiuser system Each user with long channel response signature is exploited for multiple access problems If UWB channels are independent, the multi antenna UWB system shows both capacity and diversity gain However, due to correlation between antennas, the performance of system degrades In this paper, the channel capacity of multi user multi antenna TR-UWB system and the difference between the impact of transmit correlation and that of receive correlation on the system are derived Channel capacity of system is significantly improved when number of using antennas increases in a acceptable range of the correlation coefficient If the correlation of antennas is considered, at high correlation, the capacity reduces up to 60% in comparison with capacity if without correlation Keywords– UWB, TR, channel capacity, multiple access, correlation I I NTRODUCTION Ultra Wideband (UWB) is an attractive topic in recent years because of its capability of high-speed communication in short distance [1], [2] UWB comes thoroughly to solve the problem of bandwidth limit in wireless environment However, it is realized that channels in reality are multi-path fading channels [3], [4], so issues about affecting quality of transmission in UWB system serving multi-user is really complex One can resolve this problem by combining Multi-User Multi-Input Multi-Output (MU-MIMO) UWB system and Time-Reversal (TR) technique to improve transmission rate and minimize the influences of channel which decrease the quality of MU UWB system [5], [6], [7] MIMO technique is well-known with its extremely good anti-multipath-fading-effect capability using multi transmit and receive antennas to increase diversity and also help the system improve its transmission rate significantly MIMOUWB is a combination with high efficiency [5] Time-Reversal (TR) technique has been used in acoustic, medical and especially submarine communication applications [8], [9] Its advantage is decreasing bad effects caused by the channel such as Inter-Symbol Interference (ISI), Inter-User Interference (IUI), etc., without the need of using highly complex equalizers at transmitter and receiver [10], [9] In a TR system, multipleaccess mechanism is based on the unique of channel impulse 978-1-4673-2088-7/13/$31.00 ©2013 IEEE II S YSTEM DESCRIPTION A Correlation channel model MU-MIMO UWB TR system only operates when it anticipates information of CIRs which is forwarded to each user Therefore, first of all, users will send an impulse to BS to get the CIRs’ information of the communication environment The Time-Reversal Mirror (TRM) module of BS records and stores received information which is used for processing transmitted signals Multiple-Access (MA) technique is based on TR technique which uses the unique of CIRs that BS is forwarded to each antenna or user Thus, the MA-TR technique operates efficiently in the environment in which CIRs are various Proposed MU-MIMO UWB TR model includes MT transmit 22 VW VW 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