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Channel capacity comparisons under different experimental conditions. (a) Channel capacity versus ρ, given N = 2. (b) Channel capacity versus #users, given M = 8. (c) Channel capacity versus CEE, given M = 8, N = 2.
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Time reversal (TR) is regarded as a potential future transmission scheme for multi-user (MU) multiple-input single-output (MISO) ultra-wideband (UWB) communication systems. In spite of TR’s good performance in MU-MISO UWB systems, it suffers from performance degradation due to spatial correlation and imperfect channel state information (CSI). In th...
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... numerical evaluation of the channel capacity is shown with the CIR length L = 110 in the system model. The average channel capacity of every user (setting ϕ = 1, θ = 25 dBm, and SNR = 25 dB) is plotted in Fig.6 with different system configurations. ...
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... the following, without loss of generality, we use ϕ ≈ 1. The numerical evaluation of the channel capacity is shown with the CIR length L = 110 in the system model. The average channel capacity of every user (setting ϕ = 1, θ = 25 dBm, and SNR = 25 dB) is plotted in Fig.6 with different system configurations. As shown in Fig. 6a, the channel capacity per user increases monotonically with M in the low range of correlation, as a result of improved SINR achieved by enhanced spatial focus- ing. In Fig. 6b, it can be seen that even when ρ t and ρ r are equal to zero, a larger N (i.e. more co-existing users) degrades channel capacity of each user due to stronger ...
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... system model. The average channel capacity of every user (setting ϕ = 1, θ = 25 dBm, and SNR = 25 dB) is plotted in Fig.6 with different system configurations. As shown in Fig. 6a, the channel capacity per user increases monotonically with M in the low range of correlation, as a result of improved SINR achieved by enhanced spatial focus- ing. In Fig. 6b, it can be seen that even when ρ t and ρ r are equal to zero, a larger N (i.e. more co-existing users) degrades channel capacity of each user due to stronger inter- ference among users, but it still gives rise to the sum channel capacity listed in Table 3. In more details, when increas- ing the number of co-existing users from 2 to 4 ...
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... more details, when increas- ing the number of co-existing users from 2 to 4 (ρ t = ρ r = 0), the channel capacity per user reduces to 63% of the original while the sum channel capacity increases from 4.626 bps/Hz to 6.328 bps/Hz, i.e. the available bandwidth per user is reduced if the system serves more users. Further- more, based on Table 3 and Fig. 6, it is observed that the more spatial correlation, the more serious IUI, there is the less the channel capacity. In fact, IUI is introduced due to the non-orthogonality of the channel impulse responses among different users. To solve this problem, signature waveform design techniques can be utilized to combat the interference. The ...
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... adjust the amplitude and phase of each tap of the signature waveform based on the known CSI and thereby optimize the received signal to achieve low bit error rate. However, in practical systems, a mismatch between the known CSI and the true channel characteristics may occur. For example, the CSI may be outdated due to channel variations. Fig. 6c demonstrates the combined impacts of CEE and spatial cor- relation on channel capacity per user. It is obvious that the more errors in CSI, the less capacity is ...
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Citations
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Thanks to its characteristics of temporal compression and spatial focusing, the time reversal (TR) transmission system has the intrinsic capability of anti‐eavesdropping. This study analyses the physical layer security performance of the TR transmission system. The probability density functions and cumulative distribution functions of the signal‐to‐noise ratio of the legitimate user and eavesdropper are given. On this basis, the theoretical expressions of the ergodic capacities of the legitimate channel and the wiretap channel, and the achievable ergodic secrecy rate are derived. The bit error rates of the legitimate user and eavesdropper for binary phase‐shift keying modulation are given too. The correctness of the theoretical derivation is verified by simulation. For the legitimate user, the signal power increases as the number of paths increases, which indicates a higher diversity gain can be obtained, and the inter‐symbol interference power decreases as the up‐sampling factor increases. So, the signal‐to‐interference‐plus‐noise ratio (SINR) of the received signal can be significantly improved by appropriately reducing the spectral efficiency. However, the received signal's SINR of the eavesdropper cannot be promoted obviously. That is to say, compared with the eavesdropper, the legitimate user can achieve a higher rate and a lower BER, so secure transmission can be realised.
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