Tx Diversity Research Articles

Design and performance evaluation of a hybrid LiFi transceiver using OSTBC-based spatial multiplexing and transmit diversity

The need for data transmission systems that are high-speed, secure, and reliable increases as wireless communication technologies continue to advance rapidly. Light fidelity (LiFi) can meet this need through its several advantages, including high transmission rates, low electromagnetic interference, and indoor localization capabilities. This study proposes a hybrid LiFi transceiver, which utilizes LiFi technology using orthogonal space–time block coding (OSTBC), based on the spatial multiplexing (SM) and transmit diversity (Tx). The suggested hybrid LiFi transceiver aims to integrate the advantages of OSTBC, Tx diversity, and SM techniques to enhance the performance of the overall transceiver. The suggested transceiver plan to implement one of the diversity techniques, which are either Tx diversity or SM at a time. The selected technique will depends on the channel quality, optimizing the transceiver's throughput and ensuring effective utilization of the available spectrum. Through simulation results, this research aims to demonstrate that the proposed hybrid LiFi transceiver surpasses conventional LiFi transceivers that lack Tx diversity or SM. Anticipated outcomes of this research include superior data rates, enhanced reliability, and increased resilience against real channel impairments. These findings hold substantial promise for applications that requires high-speed and reliable communication, including smart homes, the Internet of Things, and forthcoming 5 G/6 G communication networks.

Performance Analysis of PN Code Acquisition with MIMO Scheme for an UWB TH/CDMA System

This paper presents performance and its simulation results of pseudonoise (PN) code acquisition scheme with MIMO scheme for an ultra‐wideband time‐hopping/code‐division‐multiple‐access (UWB TH/CDMA) system. The transmission channel is modelled as a frequency selective lognormal fading channel. In almost practical PN code acquisition system, the existence of more than two synchronous cells in the uncertainty region of the search process is possible due to multipath effect. Therefore, based on deriving the detection probability, false alarm rate, miss detection probability, and mean acquisition time, the acquisition performance is analyzed under the hypothesis of multiple synchronous states (cells) in the uncertainty region of the PN code. And the code acquisition performance is evaluated when the correlator outputs are noncoherently combined by using equal gain combining (EGC) scheme. In this procedure, the closed form for the conditional probability of decision variable is derived using the Gauss‐Hermite quadrature formula. The performance comparison of the scheme mentioned above shows that the code acquisition performance with the diversity combining technique, especially when increasing the number of antenna, is more robust than that using no diversity. And code acquisition performance comparison also shows that if the detection threshold is set inappropriately, the performance might be degraded, even if an antenna diversity method is applied. It is also shown that Tx diversity can improve the acquisition performance but not as much as Rx diversity does. And Rx diversity can be applied to the acquisition system for additional diversity gain if the complexity of the receiver can be accepted.

Analysis of Joint Transmit–Receive Diversity in Downlink MIMO Heterogeneous Cellular Networks

We study multiple-input–multiple-output (MIMO)-based downlink heterogeneous cellular networks (HetNets) with joint transmit–receive diversity using orthogonal space–time block coding at the base stations (BSs) and maximal-ratio combining (MRC) at the users. MIMO diversity with MRC receivers is particularly appealing in cellular networks due to the relatively low hardware complexity at both the BS and the user device. Using stochastic geometry, we develop a tractable stochastic model for analyzing such HetNets taking into account the irregular and multitier BS deployment. We derive the coverage probability for both interference-blind (IB) and interference-aware (IA) MRC as a function of the relevant tier-specific system parameters such as BS density and transmit (Tx) power, number of Tx antennas, and path-loss law. Important insights arising from our analysis for typical HetNets are as follows: 1) IA-MRC becomes less favorable than IB-MRC with Tx diversity due to the smaller interference variance and increased interference correlation across receive (Rx) antennas; 2) ignoring spatial interference correlation significantly overestimates the performance of IA-MRC; and 3) for a small number of Rx antennas, selection combining may offer a better performance–complexity tradeoff than MRC.

Dual code Tx diversity with antenna selection for spatial multiplexing in MIMO-WCDMA networks

This letter investigates the performance of a mixed diversity-spatial multiplexing transmission strategy for multiple input-multiple output (MIMO) networks based on dual code transmission with antenna selection. The wideband code division multiple access (WCDMA) physical layer protocol has been used to demonstrate that for eight transmit and four receive antennas per user, 2.4 Mbps more capacity is provided compared to single code spatial multiplexing transmission and 100% code allocation gain, compared to diversity combining and four codes per user.

Efficient Weight Vector Representation for Closed-Loop Transmit Diversity

For a closed-loop transmit (Tx) diversity, the Tx weights are calculated at a receiver, and fed back to a transmitter. As the number of Tx antennas increases, the potential gain of closed-loop Tx diversity may be significant. However, the amount of feedback information, which is the number of Tx weights that should be fed back, linearly increases, and the performance improvement of a closed-loop Tx diversity system may not be as significant as expected due to delay in the feedback process. Thus, an efficient Tx weight representation, which can reduce the amount of feedback information, is needed. In this letter, a Tx weight vector representation is presented, and its performance is analyzed. Analysis shows that this weight vector representation, referred to as basis selection, significantly reduces the amount of feedback information with little performance degradation.