The ever increasing wireless data services, such asimaging, video, audio, multimedia, etc., have de-mands for the very high speed wireless communicationsand network, which are unfortunately a bottleneck whencombining ...
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The ever increasing wireless data services, such asimaging, video, audio, multimedia, etc., have de-mands for the very high speed wireless communicationsand network, which are unfortunately a bottleneck whencombining with the wireline core network. Users＇ arenow expecting high quality of experience with low-costdevices, ubiquitous connectivity, energy efficiency, highreliability, or even ultra-low latency if a vehicle terminalis applied.
The performance of MC-CDMA is limited by multiple access interference (MAI). To mitigate this problem, equal BER power control (PC) was proposed for MMSE-SIC receiver, which provides a powerful solution for MAI suppre...
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The performance of MC-CDMA is limited by multiple access interference (MAI). To mitigate this problem, equal BER power control (PC) was proposed for MMSE-SIC receiver, which provides a powerful solution for MAI suppression (M. Tan and Y. Bar-Ness, IEEE commun. Lett., vol. 8, pp. 348-350, 2004), wherein the power distribution on different users was derived under the assumption of perfect channel state information (CSI) at the receiver. In practice, CSI is obtained from channel estimation, in which errors are inevitable. Therefore, the analysis of the robustness of the MMSE-SIC with the equal BER PC to channel estimation errors (CEE) is of great importance. In this paper, a method of second-order approximation is applied to estimate the mean excess MSE (MEMSE) of different users in a given decision order. The accuracy of the approximation is confirmed by simulation results. Furthermore, it is interesting to find out that the MMSE-SIC receiver with the equal BER PC presents significant robustness to CEE.
Multicode multi-carrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) of use...
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Multicode multi-carrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) of user's multicodes and multi-user interference (MUI). In this paper, to mitigate this problem, a minimum mean square error successive interference cancellation (MMSE-SIC) receiver is applied in the multicode MC-CDMA. Furthermore, to increase the efficiency of SIC, a simple power distribution control (PDC) algorithm, based on equal BER criterion, is investigated under a short-term constraint of average transmit power. In correlated Rayleigh fading channels, the MMSE-SIC receiver integrated with the equal BER PDC can suppress interference effectively, resulting in a performance close to the single user bound (SUB).
Multicode multicarrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) and mul...
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Multicode multicarrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) and multiuser interference (MUI). To mitigate this problem, a nonlinear zero-forcing successive interference cancellation (ZF-S1C) receiver is applied in this paper. Furthermore, to minimize each user's bit error rate (BER), optimal power distribution control (PDC) is considered. Results show that in correlated Rayleigh fading channels, the multicode MC-CDMA system based on the ZF-SIC receiver with the optimal PDC remarkably out performs other receivers proposed in the literature. Moreover, the ZF-SIC integrated with the optimal PDC present significant performance advantage over that with the equal BER PDC, particularly under a short-term total transmit power constraint.
We derive a throughput bound for CDMA unslotted ALOHA with memory ARQ in general. Since the conventional 'single queue with feedback' model, customarily employed for an ALOHA system with pure or hybrid type-I ...
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We derive a throughput bound for CDMA unslotted ALOHA with memory ARQ in general. Since the conventional 'single queue with feedback' model, customarily employed for an ALOHA system with pure or hybrid type-I ARQ, cannot be applied to this case, we introduce an expanded model, which consists of a network of queues, and apply the Jackson theorem to simplify the analysis. When using code combining, it is very difficult to find the actual probability of packet success. Hence, instead of finding actual values, we evaluate a lower bound on it. Together with the expanded model and the packet success probability bound, we obtain the throughput bound for given composite offered traffic by using an iterative search procedure.
In a regular multicarrier CDMA (MC-CDMA) receiver, timing of the starting point of the desired signal must be found with small error in order to demodulate correctly the information carried by different subcarriers. T...
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In a regular multicarrier CDMA (MC-CDMA) receiver, timing of the starting point of the desired signal must be found with small error in order to demodulate correctly the information carried by different subcarriers. This requires a complicated timing acquisition for each user in the receiver of the uplink MC-CDMA system due to the randomness of delays. We remove this requirement for the uplink receiver by providing a method using partial sampling demodulation. The proposed partial sampling minimum mean square error (MMSE) receiver is shown to have stronger capability of both interference suppression and near-far resistance than that of a regular symbol receiver The proposed receiver can be implemented adaptively by using a least-mean-square (LMS) algorithm. A training sequence is required to achieve initial adaptation.
We propose a novel dual-rate synchronous multi-carrier code division multiple access (MC-CDMA) system. In this system, all users are designed to have the same processing gain and share the same set of subcarriers. Two...
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We propose a novel dual-rate synchronous multi-carrier code division multiple access (MC-CDMA) system. In this system, all users are designed to have the same processing gain and share the same set of subcarriers. Two decorrelator-based receivers are implemented and analysed in this paper for the dual-rate MC-CDMA system; a high-rate decorrelator (HRD) matches high data rate and a low-rate decorrelator (LRD) matches low data rate. It has been proved that for low-rate users, HRD and LRD perform similarly, while for high-rate users, LRD outperforms HRD when the signature sequences of high-rate and low-rate users are not orthogonal. Furthermore, we propose a blind multiuser detection method, which can be implemented adaptively by applying the bootstrap algorithm. It is shown that the blind adaptive detector is near-far resistant and has performance similar to that of minimum mean square error (MMSE) detector.
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