Augmented reality (AR) technology is an advancement that allows users to see the real world through the use of a virtual device. The explosive manufacturing of mobile devices follows a rise in the popularity of mobile phones and allows the user to run AR applications based on the mobile with substantial mobility awareness. The new generation networking technology (e.g., 6G) serves as a challenge for upcoming AR applications to attain low latency and computationally enhanced during the time that mobile edge computing (MEC) allows the user to communicate easily with AR applications. However, previous work on mobile edge computing support AR may not perform as expected in many practical cases, such as irreparable network interruptions due to wireless connectivity instability and user mobility, which is defining feature of popular AR applications. To attain low latency, deploying computational and mobility, the MEC will perform a major role in either fifth generation (5G) or six-generation (6G) networking. This paper studies in general the AR concept and the utility of mobility management in MEC applications that can be implemented in the next generation of mobile by reviewing the user to connect their interface. This paper discusses augmented reality and mobility challenges. The future direction and solution for the implementation of AR based mobility aware and MEC are also analyzed. This survey will contribute a comprehensive of the issues associated with mobility management, specifically concerning augmented reality with mobility awareness in future.

ARINC 664, which is a heavily used protocol for modern avionics networks, is preferred due to its simplicity although its mixed-criticality support is limited. Time Triggered Ethernet (TTEthernet), and IEEE Time Sensitive Networking (TSN), which utilize time synchronized schedule, are more suitable for supporting mixed-criticality applications; however, both require a fault tolerant time synchronization that makes the certification process more challenging. In this paper, we propose a novel dynamic priority assignment (DPA) concept together with the burst limiting shaper (BLS) from the IEEE TSN standard to enhance the schedulability and the mixed-criticality support of ARINC 664. The decision of flow re-assignment to a new priority class is done by calculating the high priority (HP) and low priority (LP) class worst-case delays using the network calculus framework. The numerical results show that the class utilization rates can be significantly increased by using the DPA concept with and without the BLS while the deadline constraints for all classes are satisfied. Thus, the DPA can improve the schedulability and mixed-criticality of ARINC 664 without using any time synchronization mechanism.

Vehicular ad hoc networks (VANETs) have recently attracted interest for automation and intelligent transportation system (ITS). Two major factors which influence the performance of VANETs in practical transmission are bit error and channel capture. In this paper, to assess the performance of the IEEE 802.11 medium access control (MAC) for VANETs under channel fading and capture effect, an analytical model based on Markov chain model is presented. The parameters that could impact performance are studied. The relationship among parameters and performance metrics are derived. The probability of successful and unsuccessful transmission, probability of frame capture, and throughput expressions are obtained. Furthermore, to verify the analytical studies numerical results are presented.

In vehicular ad hoc networks (VANETs), mobility among vehicles can result in rapid topology changes with frequent link breakage and unstable communications, which cause collision and packet loss. Conversely, cooperative transmission can improve communication reliability and can enhance communication rate with lower delay by alleviating wireless channel impairments caused by mobility in VANETs. In this study, a novel reliable and efficient cooperative medium access control protocol for VANETs (RECV‐MAC) is proposed. Since a random access mechanism is suitable and efficient because of the dynamic and open nature of VANETs, authors used the random access approach, i.e. carrier sense multiple access with collision avoidance, which is used by IEEE 802.11p. The RECV‐MAC protocol is compatible with IEEE 802.11p. New control messages are introduced to support cooperative communication. The mechanism is defined to choose suitable transmission mode as well as to select optimal helper. To investigate the performance of RECV‐MAC protocol, Markov chain model‐based analytical analysis is provided. The RECV‐MAC protocol is validated by numerical results which demonstrate that RECV‐MAC protocol improves the performance with higher throughput, enhances the reliability of communication by decreasing packet dropping rate (PDR), and decreases delay, in particular, satisfies the delay constraint of 100 ms for sm.

We present a distributed joint power control and transmit beamforming selection scheme for multiple antenna wireless ad hoc networks. Under the total network power minimization criterion, a joint iterative beamforming and power control algorithm is proposed to reduce mutual interference at each node. Total network transmit power is minimized while ensuring a constant received signal-to-interference and noise (SINR) at each receiver. First, transmit beamformers are selected from a predefined codebook to minimize the total power in a cooperative fashion. We also study the interference impaired network as a noncooperative beamforming game. By selecting transmit beamformers judiciously and performing power control, convergence of noncooperative beamformer games are guaranteed throughout the iterations. The noncooperative distributed algorithm is compared with centralized and cooperative solutions through simulation results.

A new multihop protocol is devised for cellular networks. Mobiles transmit and receive on uplink time slots assisting in-building users that are experiencing high pathloss. Wireless capacity indoors is improved by 3× to 8× compared to direct transmission. A central feature of the protocol, is that interference to existing or primary" communication may be controlled. Power control by the source mobile, using a measurement of basestation pilots, minimizes uplink interference on a shared multihop uplink slot. Likewise interference cancelation at the basestation, allows the a slot normally reserved for downlink multihop messages to be reused. This paper presents outage analysis of interference at the relay and the source mobile for the two hop link.

Radio networks experience the greatest spectrum scarcity in urban environments. Dynamic radio access enables simultaneous and opportunistic spectrum reuse. This paper considers frequency division duplexing cellular networks, where every mobile user (MU) is allocated a frequency channel for uplink transmission to the base station (BS). Previously a frequency reuse model has been proposed for low power communications among secondary users (SU) in a cell. In the system the secondary user controls its transmit power to minimize interference at the nearest base station. This paper considers reusing frequencies within a cell to allow mobile users in outage to use other active users as relays to the base station. Different criteria are compared for choosing the relay frequency channels to be reused. Simulations consider urban large scale propagation conditions in a multicell environment. Results show significant reduction in the overall outage probability for the enhanced cellular network. The algorithm allows cooperation to share available resources without changing hardware or networks.

In this paper, we present the code design structure of unitary and non-unitary differential space-frequency group codes (DSFCs) for multiple-input multiple-output (MIMO)- orthogonal frequency division multiplexing (OFDM) systems based on optimal coherent space-frequency (SF) group codes. Under the assumption that the transmitter knows only the delay profile of the channel, a differential transmission rule incorporated with subcarrier allocation is obtained that allows data to be sent without channel estimates at the transmitter or receiver. The differential encoding/decoding is performed in the frequency domain within each single OFDM symbol. Therefore, proposed DSFCs can be successfully decoded even for a rapidly fading channel which may change independently from one OFDM symbol to another. Unitary and nonunitary DSFCs, that are constructed based on design criteria, are compared with recently published techniques in the literature and shown to inherit coding gain of optimal coherent SF codes. Due to design structure and energy constraints, our nonunitary DSFCs do not blow up or diminish during the differential encoding.

Downlink cellular packet systems utilizing opportunistic scheduling and adaptive modulation must deal with outdated channel state information. A fade margin is part of the link budget which is used to mitigate the effect of channel variation. Channel prediction reduces this margin, improving the transmission rate. We derive a fade margin which keeps packet outage constant for any prediction error variance. In our model both the signal and the interferer powers are modeled as autoregressive stochastic processes and predicted. The MMSE power predictor is also derived. Improvement in system throughput due to channel prediction is shown for a proportional fair scheduled downlink packet system, and compared to systems without prediction and opportunistic scheduling.

Wireless systems exploiting multi-user diversity require accurate channel state information. In this paper we examine channel prediction as a method to improve the performance of these systems. We model the outdoor channel by the Rician model, which combines diffuse spectra with a single specular component. Prediction accuracy is determined for the Rician model given various ratios (K factors) of specular to diffuse power. Simulation results show that accurate channel prediction further than one wavelength can be achieved at 30 dB SNR when the channel K factor is greater than ten. The predictor was evaluated on measured channels, and the Rician model was found to be appropriate as prediction intervals of the measured data are similar to those of synthetic data with same K factor. Using measurements some results regarding channel stationarity and optimal filter order are presented. We show for a proportionally fair scheduled downlink packet system that the predictor reduces fade margin at fixed packet outage leading to an improvement in throughput.

Cognitive radio is a key enabling technology of dynamic spectrum access for exploiting unused spectrum resources. This article focuses on modeling the opportunity for cellular systems which have the greatest spectrum scarcity problem. A system model is introduced for analyzing the opportunistic bandwidth within a cellular network through a spatial evaluation of the resources used by the primary and available to the secondary systems. Towards this purpose, two metrics are introduced signifying the spatial coherence of resources: the region of interference and the region of communications. Our results suggest significant underutilized resources that can be scavenged through secondary users to greatly improve the spectral efficiency of cellular networks.

In this paper, recent localization algorithms are analyzed under a common one hop network scenario. The performance of localization is affected by physical parameters in a real wireless environment such as anchor node location and quantity, and error in the measured distance. The numerical analysis presented in this paper can be used to choose among localization algorithms to satisfy practical constraints such as number of anchors, nodes, geometry of anchors and computational efficiency.

Cognitive radio is a key enabling technology of dynamic spectrum access for exploiting unused spectrum resources. This article focuses on modeling the opportunity for cellular systems which have the greatest spectrum scarcity problem. A system model is introduced for analyzing the opportunistic bandwidth within a cellular network through a spatial evaluation of the resources used by the primary and available to the secondary systems. Towards this purpose, two metrics are introduced signifying the spatial coherence of resources: the region of interference and the region of communications. Our results suggest significant underutilized resources that can be scavenged through secondary users to greatly improve the spectral efficiency of cellular networks.

This paper looks at the fairness achievable in an OFDMA system. Based on the results, an online resource allocation algorithm is defined for a reservation-based OFDMA system where the frame duration is much shorter than the duration of a call. Simulations show that the algorithm leads to a considerable reduction in the probability of outage. A protocol is introduced for fair resource allocation between two nodes in an ad hoc system. The minimum required overhead is shown to depend on the level of fairness required, and the bounds that are derived.

We examine the prediction of the signal to interference ratio by the mobile as a means of improving the channel feedback in adaptive radio links. A cellular system is considered where the pilots of the desired and interfering basestation are available to obtain channel estimates. Both are modeled as auto-regressive (AR) stochastic processes. We derive the density function of the conditional SIR in order for the mobile to determine the backoff margin required for a percentage of packets to be decoded successfully.

Channel prediction is an appealing approach to mitigate channel mismatch in wireless downlink packet systems. Channel mismatch arises due to the delay in the feedback loop. Both synthetic and measured channels were used to assess the accuracy of channel prediction for various ratios of specular to diffuse power. The power spectrum was estimated rather than assumed known. It has been found that high ratios (K factors) greater than ten are necessary for prediction greater than one wavelength. K factors of measured channels gave prediction accuracy similar to that of the synthetic channel given by the same K factor.

In this paper, we propose a fair pricing strategy to improve the performance of a slotted Aloha system in which users act selfishly to improve their own utility. Based on a game theoretic framework, we show that both throughput and revenue can be optimized by appropriately selecting a pricing strategy for the selfish users. Our proposed solution considers multipacket reception capabilities for the physical layer. The network enforces fairness among different users by employing a pricing policy that favors equal access probabilities.

Space-frequency (SF) group codes are designed for multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. A rather general channel model is assumed, where the channel is frequency-selective Rayleigh fading with arbitrary power-delay profile. It is shown that the SF group code has a symmetric distance structure like the space-time group code, if the group consists of diagonal matrices. A scenario where the multiple codewords are loaded onto the subcarriers of the OFDM system in parallel is considered. The optimality condition on the choice of subcarrier allocation is found, and an optimal subcarrier-allocation scheme is proposed. A transmit scheme where rotated versions of the same signal are transmitted from different transmit antennas is proposed, and it is shown that it satisfies the optimality condition. Then matrix groups are designed which guarantee that the resulting SF codes are full rank. Numerical comparisons with recently published techniques in the literature verify our improved performance.

In orthogonal frequency division multiple access (OFDMA), the total spectral resource is partitioned into multiple orthogonal subcarriers. These subcarriers are assigned to different users for simultaneous transmission. OFDMA is very sensitive to frequency synchronization errors. In an unsynchronized OFDMA uplink, each user has a different carrier frequency offset (CFO) relative to the common uplink receiver. The orthogonality among subcarriers is thus destroyed resulting in multiple access interference as well as self interference. This problem is tackled in this paper by constructing the orthogonal spectral signals that would have been received if all users were frequency synchronized. A generalized OFDMA is described first considering arbitrary subcarrier assignments. A new signal model is formulated to characterize the interference on the generalized OFDMA uplink due to multiuser frequency synchronization errors. Least squares (LS) and minimum mean square error (MMSE) criteria are used to construct the orthogonal spectral signals from one received OFDMA block. An efficient implementation method is developed based on a banded matrix approximation, which is computationally inexpensive and provides good performance.

A delayed space-frequency cyclic group code is proposed in this paper, which applies a new bandwidth and power-efficient space-frequency processing on the orthogonal-frequency- division-multiplexing (OFDM) system. The delayed orthogonality with respect to frequency tones among different transmitter antennas guarantees to exploit the full spatial and frequency diversity of the frequency-selective multi-input multi-output (MIMO) channel. In contrast with the schemes which combine the single-antenna error correcting code with delayed transmitter diversity in multi-antenna OFDM systems, this space-frequency code has a robust performance in flat-fading channel. Without a tradeoff of the diversity gain, the proposed code can be easily expanded to achieve high data rate and generalized to more than two transmit antennas.

A high rate delayed space-frequency cyclic group code is proposed in this paper, which applies a new bandwidth and power-efficient space-frequency processing on the orthogonal-frequency-division-multiplexing (OFDM) system. The delayed orthogonality with respect to frequency tones among different transmitter antennas guarantees to exploit the full spatial and frequency diversity of the frequency-selective multi-input multi-output (MlMO) channel. In addition, after partitioning the subcarriers into groups and coding each group with the proposed block code, a maximized multiplexing gain can be obtained without any diversity loss. The proposed code can also be easily generalized to multiple transmitter antenna systems.

In orthogonal frequency-division multiple access (OFDMA), closely spaced multiple subcarriers are assigned to different users for parallel signal transmission. An interleaved subcarrier-assignment scheme is preferred because it provides maximum frequency diversity and increases the capacity in frequency-selective fading channels. The subcarriers are overlapping, but orthogonal to each other such that there is no intercarrier interference (ICI). Carrier-frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduces ICI, resulting in multiple-access interference. This paper exploits the inner structure of the signals for CFO estimation in the uplink of interleaved OFDMA systems. A new uplink signal model is presented, and an estimation algorithm based on the signal structure is proposed for estimating the CFOs of all users using only one OFDMA block. Diversity schemes are also presented to improve the estimation performance. Simulation results illustrate the high accuracy and efficiency of the proposed algorithm.

In OFDM carrier frequency offset must be estimated and compensated at the receiver to maintain orthogonality. OFDM carrier frequency synchronization performance can be improved by using diversity. In this paper, we examine the sensitivity of the carrier frequency estimator against key system parameters in a practical implementation using real data obtained on the Stevens wireless testbed. The experimental setup is comprised of wideband 65 Msamples/second digital to analog converter, radio frequency (RF) transmitter, which transmits at 2.4 GHz frequency with 12 MHz bandwidth and RF receiver chains whose outputs are sampled at 65 Msamples/sec.

In orthogonal frequency division multiple access (OFDMA), closely spaced multiple subcarriers are assigned to different users for parallel data transmissions. The subcarriers are overlapping but orthogonal to each other such that there is no inter-carrier interference. Carrier frequency offsets between the transmitter and the uplink receiver will cause the loss of the orthogonality among subcarriers, hence introduce inter-carrier interference resulting in multiple access interference. This paper proposes a carrier frequency offset estimation algorithm for the uplink of interleaved OFDMA systems. This algorithm requires only one OFDMA block and utilizes the inner structure of the signals without any aid from training symbols or the knowledge of channels. Simulation results illustrate the high accuracy and efficiency of the proposed estimation algorithm.

Orthogonal frequency division multiplexing (OFDM) communications transforms frequency selective channels into multiple low rate subchannels robust against frequency selective fading. Carrier frequency offset between transmitter and receiver local oscillators must be estimated and compensated at the receiver to maintain orthogonality of these subchannels. In many practical applications, this problem is complicated by signals corrupted by colored noise due to interferer and diversity combining. Multi-antenna receiver diversity may be susceptible to correlation across receiver branches. The nonlinear least squares (NLS) estimator proposed by the authors in an earlier work exploits diversity for carrier frequency synchronization and is shown here robust to colored noise. Furthermore, the estimator mean square error (MSE) is asymptotically efficient attaining performance corresponding to the Cramer-Rao bound (CRB) for large enough sample. Numerical studies are presented to verify our results.

Recently multicarrier communications (MC), eg, OFDM systems, have received a lot of interest. Multicarrier schemes increase the efficiency and capacity of wireless networks, but are very sensitive to carrier frequency synchronization errors. We explore a framework to exploit temporal and spatial diversities to improve the performance of such schemes in the downlink or uplink by enhancing synchronization. The estimator developed here does not depend on the presence of repeated known symbols or pilot tones. Diversity modes are accessed via a common notation and this allows us to conveniently generalize to temporal or spatial diversity reception schemes. The acquisition limit of the proposed algorithm is not limited to half a subcarrier spacing as is the case with many other blind algorithms. Performance of the algorithm is carried out with simulation studies and a summary of our findings for temporal and spatial diversity are reported.

Multicarrier CDMA (MC-CDMA) is a flexible and adaptable radio interface to provide dynamically changing bit rates and a variety of services on radio channels. An accurate channel estimate allows the use of multiuser detection and power loading to improve system performance. A blind linear multiuser channel estimator for MC-CDMA is proposed. Unlike the time varying spreading code or information bearing sequence, the channel is stationary over long time intervals. This fact is exploited in a new method for simultaneous estimation of the channel impulse response vector of multiple users. The complexity of the derived channel estimator can be reduced at the expense of accuracy. It is shown by computer simulation that the proposed method performs well under different scenarios.

In orthogonal frequency-division multiplex (OFDM) communications, the loss of orthogonality due to the carrier-frequency offset must be compensated before discrete Fourier transform-based demodulation can be performed. This paper proposes a new carrier offset estimation technique for OFDM communications over a frequency-selective fading channel. We exploit the intrinsic structure information of OFDM signals to derive a carrier offset estimator that offers the accuracy of a super resolution subspace method, ESPRIT.

In OFDM communications, the loss of orthogonality due to carrier offset must be compensated before DFT-based demodulation can be performed. We present a high accuracy blind carrier offset estimation algorithm and a blind channel equalizer which exploit the intrinsic structure information of OFDM signals. The latter method allows the receiver to perform coherent demodulation in changing environments without the overhead required for additional pilots.