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This letter analyzes the coverage performance of user-centric dense terahertz (THz) networks in which each user is cooperatively served by multiple base stations (BSs). Both dynamic and static clustering approaches are considered, based on which we study the coverage probability of the user-centric THz network by using stochastic geometry. Numerical results are provided to demonstrate the accuracy of the derived expressions and the advantage of both dynamic and static clustering schemes over the conventional single BS association in THz networks.

In millimeter wave (mmWave) networks, base stations (BSs) are expected to be densely deployed in order to meet the demands of mobile users. A major challenge in dense mmWave networks is the interference experienced by the user from the neighboring BSs which limits the density of deployed BSs. A promising solution to this challenge is to adopt user-centric BS cooperation that allows a user to be connected to a set (cluster) of BSs instead of being associated with a single one. In this paper, we investigate the performance of user-centric mmWave networks with dynamic clustering. First, we propose a dynamic clustering model to enable the user-centric BS cooperation. Then, based on the proposed model, we analyze the coverage probability and average spectral efficiency (ASE) performances using stochastic geometry tools. We also propose a BS clustering optimization framework to achieve maximum ASE performance for given network configuration. Finally, numerical and simulation results are provided, showing that the proposed dynamic clustering schemes always outperform static clustering and single-BS selection schemes and yield an optimum system performance for given network parameters.

The user-centric base station cooperation is a new approach that allows a mobile user to be connected to a set (cluster) of base stations instead of being associated with a single one. This approach is highly valuable in millimeter wave networks where the base stations are expected to be densely deployed. In this paper, we evaluate the performance, in terms of coverage probability, of user-centric millimeter wave networks with dynamic clustering. First, we propose a dynamic clustering model for base stations that will cooperate to serve a given user. Then, based on the proposed model, we investigate analytically the coverage probability performance of the considered user-centric network using stochastic geometry tools. Finally, numerical and simulation results are provided, showing that the proposed dynamic clustering model always outperforms static clustering and single base station selection schemes for given network parameters.

This paper presents analytical and empirical data documenting the effects of solar radio emissions on outdoor propagation path loss at 60 GHz bands. Both line-of-sight (LOS) and non-LOS scenarios were considered. The setup used in the empirical studies emulates the future fifth-generation cellular systems for both access and backhaul services, as well as for device-to-device communications. Based on the measurement data collected in sunny weather with intense solar activities, we developed large-scale propagation path loss models at 60 GHz, and observed the effects of solar radio emissions on the path loss data. It is shown that solar radio emission can decrease carrier-to-noise ratio, and that this translates into a corresponding increase in the path loss exponent (PLE) values for the large-scale propagation path loss channel models. Empirical data show that 9.0%-15.6% higher PLE values were observed in hot and sunny weather during the day (41{\deg}-42 {\deg}C) compared with the counterpart measurements taken at night in cool and clear weather (20{\deg}-38 {\deg}C). This translates into a corresponding decrease in 60 GHz radio coverage in hot and sunny weather during the day. The empirical data are closely corroborated by analytical estimates presented.

Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency-division multiplexing (MIMO-OFDM) is an attractive technique for next-generation wireless systems. However, the performance of wireless links is severely degraded due to various channel impairments which cause a decoding failure and lead to packet loss at the receiver. One technique to cope with this problem is the rateless space-time block code (RSTBC). This paper presents experimental results on the performance of a 2×2 MIMO-OFDM system with RSTBC as measured in a testbed implemented with field-programmable gate array (FPGA). The average bit error rate (BER) performance of the proposed scheme is evaluated experimentally, and the results agree closely with simulation and analytical upper bound. It has been shown that RSTBC can be implemented in real-world scenarios and guarantee the reliability of loss-prone wireless channels.

This paper presents propagation path loss channel models developed from real-field measurement campaigns that were conducted in indoor and outdoor Line-of-Site (LOS) propagation environments in Riyadh city, Saudi Arabia, using highly directional antennas at 60 GHz. The setup used in these measurements emulates the future fifth-generation (5G) cellular systems for both access and backhaul services, as well as for Machine-to-Machine (M2M) communications. We used our measurement data to develop the corresponding large-scale propagation path loss models at 60 GHz, using the log-distance and the floating intercept modeling approaches. It is shown that cellular radio links can be established in short-range distances up to 134 m indoors, and up to 77 m outdoors, when employing highly directional antennas at both the transmitter and receiver sides. It is also shown that path loss at 60 GHz in hot and sunny weather during the day, is higher than those obtained in cool and clear weather at night. This is partly due to solar radio noise effect arising from the intense solar radiation that characterizes summer afternoon in Riyadh city, which can cause a decrease in carrier-to-noise ratio at the input of receiving antennas. It is also partly due to the increase in thermal noise when electronics components in the measurement device become hot. The results presented here are thus very useful in 5G cellular design and infrastructure planning in the gulf region, where daytime temperature could reach 43° C or more.

This paper presents experimental results on the performance of generalized spatial modulation scheme with variable active transmit antennas (VA-GSM). In the VA-GSM scheme, one or more transmit antennas are activated simultaneously to transmit the same complex symbol. The indices of the set of activated transmit antennas at any time instant are then used to convey extra information in addition to the transmitted complex symbol. The average bit error rate performance of the proposed scheme is evaluated experimentally, and the results agree closely with simulation. We also compare the VA-GSM with existing SM and GSM schemes.

This paper presents the concept of spatial modulation (SM) scheme for massive multiuser MIMO (MU-MIMO) system. We consider a MU-MIMO system whereKusers, each equipped with multiple antennas, are jointly serviced by a multiantenna base station transmitter (BSTx) using appropriate precoding scheme at the BSTx. The main idea introduced here is the utilization of the user’s subchannel index corresponding to the precoding matrix used at the BSTx, to convey extra useful information. This idea has not been explored, and it provides significant throughput enhancements in a multiuser system with large number of users. We examine the performance of the proposed scheme by numerical simulations. The results show that as the number of users and the receiving antennas for each user increase, the overall system throughput gets better, albeit at the cost of some degradation in the BER performance due to interantenna interference (IAI) experienced at the receiver. We then explore zero-padding approach that helps to remove these IAI, in order to alleviate the BER degradations.