Adaptive Coding and Modulation for Large-Scale Antenna Array-Based Aeronautical Communications in the Presence of Co-Channel Interference

In this paper, the performance analysis of two different diversity models in presence of multiple interferers and co-channel interference is presented. Arbitrary number of received signals are examined and processed using these diversity techniques. The performance analysis is presented for a Partitioned Selection Diversity Combiner (PSDC) which is an Advanced Diversity Combiner (ADC) consisting of $L$ Selection Combiners (SC) followed by a Maximal Ratio Combiner (MRC). The results are also presented for another ADC consisting of a Generalized Selection Combiner (GSC) followed by an MRC. Both the models are analyzed in the presence of co-channel interference (CCI) over Nakagami-m fading channels. The signal to interference plus noise ratio (SINR) is derived. Using the obtained expressions of SINR, the Average bit error rate (ABER) expression for differential phase shift keying (DPSK) and non-coherent frequency shift keying (NCFSK) modulation techniques are derived. The ABER results are plotted and comparison is made between the two diversity models. Numerical and simulation results are done.

Due to cell planning in a cellular communication network, it is difficult for a mobile user in a cell to get ranging measurements from other neighboring cells. Consequently, it is necessary to enhance signal sensitivity using long integration techniques so that the user position is obtained by trilateration. In order to maximize integration gain in coherent/noncoherent hybrid long integration, it is desirable to make SNR (signal to noise ratio) after coherent integration become as large as possible. Because SIR (signal to interference ratio) is not improved by the long integration, however, it is needed to mitigate CCI (Co-Channel Interference) so that the resultant hearability can be enhanced for weak signals. This paper presents a hybrid long integration scheme in presence of CCI. SNIR (signal to noise plus interference ratio) is employed to explain the loss induced by interference as well as noise. Together with interference cancellation and residual frequency estimation technique, design procedure of hybrid long integration is proposed to maximize SNIR. Simulation results show that hearability is greatly improved at most of cell coverage when the proposed method is used.

The level crossing rate (LCR) is an important second-order statistical quantity that characterizes the rate of occurrence of fading time intervals. In this paper, we investigate the LCR of multiantenna flat-fading channels in the presence of additive white Gaussian noise and cochannel interferers with unequal received powers and Doppler shifts. We first present a unified approach to derive the exact LCR of the signal-to-interference-noise ratio at a receiver, where maximum ratio combining is deployed over spatially correlated or uncorrelated systems. Through the exact LCR derivation, we identify an accurate approach to obtain a simplified approximate LCR expression in the spatially uncorrelated system case. Benefits of the LCR expressions derived in the paper are demonstrated in two important applications: 1) the packet error rate is evaluated through the finite-state Markov channel model; and 2) the optimum packet length to maximize the throughput of the system with the stop-and-wait automatic repeat request protocol is derived. The analytical results are validated by simulations.

This paper propose a new multiple-input multipleoutput (MIMO) signal processing scheme that combines optimum transmit and receive beamforming with the Alamouti space-time block code (STBC) transmission and modifies the decoding process. The scheme uses double antenna array groups to achieve stable performance regardless of direction of arrived (DOA) and angular spread (AS). In a multiuser MIMO communications scenario, the beamforming suppresses co-channel interference (CCI) by maximizing the uplink signal-to-noise-plus-interference-ratio (SINR) and suppress CCI independently while preserving orthogonality of the MIMO channel. It is shown that the beamforming process provides array gain by increasing the bit-error-rate (BER) performance and maximizes the available uplink channel capacity for each user in the presence of CCI.

The performance of dual-hop communication over independent and non-identical Nakagami-m fading channels in the presence of co-channel interference is investigated. Specifically, an upper-bound of the equivalent signal-to-interference-plus-noise ratio (SINR) at the destination is introduced. Then, the cumulative distribution function (CDF) and the probability density function (PDF) of the upper bounded SINR are obtained. Moreover, simple, yet general, asymptotic expression for the error probability is presented and discussed. Besides, with the goal to minimize the asymptotic average error probability of the system under study, we investigate three optimization schemes, namely, adaptive power allocation under fixed location for the relay, optimal relay positioning with fixed power allocation, and joint optimization of the power allocation and relay location under transmit power constraint. Results show that optimum power allocation brings only coding gain, while the optimum relay location scheme yields diversity gains as well.

The asymptotic performance of multi-user amplify-and-forward relay networks with massive MIMO is investigated. By using transmit power scaling laws at the user nodes, the asymptotic signal-to-interference-plus-noise ratio (SINR) expressions are derived when the antenna counts at the relay and destination are allowed to grow unbound, and thereby, the asymptotic sum rate expressions are obtained. Notably, these asymptotic SINRs and sum rates are independent of the fast fading component of the wireless channel, and consequently, yield a low-complexity medium access control layer and reduced latency in the air interface. Further, the detrimental impact of practical transmission impairments, including (i) imperfect channel state information (CSI), (ii) co-channel interference (CCI), and (iii) pilot contamination is studied by deriving the corresponding asymptotic SINRs and sum rates. For the perfect CSI case, the transmit power at each user node can be scaled down inversely proportional to the antenna count at the relay without degrading the system performance. However, for the imperfect CSI case, the transmit powers of the user nodes can only be scaled down inversely proportional to the square-root of the number of relay antennas. Interestingly, for the perfect CSI case, the presence of CCI neither affects these transmit power scaling laws nor degrades the asymptotic SINR. However, pilot contamination significantly limits the system performance.

Hybrid ANN reducing training time requirements and decision delay for equalization in presence of co-channel interference

In this paper, the impact of co-channel interference (CCI) on the performance of an underlay cognitive radio network over Nakagami- ${m}$ fading channels is thoroughly presented and analysed. More precisely, a decode-and-forward relay protocol for a cognitive cooperative network is considered. In this study, the impact of both the primary transmitter interference and CCI on the secondary system performance are considered. First, an exact expression for the equivalent signal-to-interference-plus-noise ratio of the secondary system is obtained. Then, the corresponding exact and asymptotic cumulative distribution functions are derived. From this, the exact outage performance for the secondary network is investigated. Furthermore, the equivalent probability density function is obtained and discussed. In addition, approximate expressions for the average error probability and the system ergodic capacity performances are derived. From the results, it can be inferred that the presence of the CCI and primary network interference severely degrades the system performance. Moreover, a higher value of the shape parameter of the desired fading channel gives better performance and diversity gain. In addition, despite the impact of interferences, the secondary network performance gives better results in comparison to the Rayleigh fading channels scenario.

Multiple input multiple output (MIMO) technique that requires multiple antennas at both transmitter and the receiver is a key technology to meet the peak data rates and spectral efficiency targets of long term evolution (LTE) systems. MIMO is a widely researched topic, and understanding of MIMO concepts have an interaction with other essential enhancement mechanisms in the system including link adaptation, resource scheduling, inter stream interference, rank of the channel, etc. This paper mainly aims to target the MIMO mode adaptation strategies in LTE systems by considering the rank and other key parameters like antenna correlation, doppler frequency, bit rate, throughput, etc. 3GPP LTE rel-8 has adopted seven MIMO modes and variable modulation and coding schemes (MCS) to effectively utilize the available resources for maximizing the throughput of the system. In this paper, new techniques for obtaining appropriate rank and a new MIMO mode switching algorithm to maximize data rate of the user equipment (UE) for a given channel consider at the receiver with reasonable complexity, and there by improving the average system throughput are proposed. The paper considers only four MIMO modes namely transmit diversity, open loop spatial multiplexing (OLSM), closed loop spatial multiplexing (CLSM) and beam-forming with different modulation levels. MIMO mode switching is done based on throughput value between open loop modes namely transmit diversity and OLSM for high mobility UE in the presence of co channel interference (CCI). Similarly, mode switching is done between closed loop modes namely CLSM and beam-forming for pedestrian UE in the presence of CCI. Simulation results are provided to illustrate the performance benefits of the proposed algorithm. The simulation results reveal that these new techniques improves the system throughput significantly.

In this paper, we examine the impact of channel estimation errors on Maximum Ratio Combining (MRC) in receive diversity systems, in the presence of co-channel interferers. The channel is modelled as flat Rayleigh fading, slowly varying and spatially independent. It is assumed that the spatial combiner weights are imperfect estimates of the desired user's fading coefficients and complex Gaussian distributed. Closed form expressions for signal to interference plus noise ratio (SINR) distribution and outage probability is obtained. Using these expressions, the effect of channel estimation quality on performance is investigated.

Orthogonal frequency division multiplexing (OFDM) is an optimal technique for high-speed transmission. In this paper, a multicell multiuser OFDM system with adaptive subcarrier allocation and adaptive modulation is considered. We propose an adaptive subcarrier, bit and power allocation algorithm to maximum the total throughput of the multicell system in the presence of cochannel interference (CCI), frequency selective Rayleigh fading and additive white Gaussian noise (AWGN). Its performance in a multicell system with different number of users is investigated through simulation. It is shown from the simulation that this adaptive allocation algorithm enhances the throughput of OFDM systems as compared to equal power allocation and is suitable for multiuser system.

The performance of conventional and decision feedback differential detection receivers for Gaussian minimum-shift keying (GMSK) signals transmitted in the presence of cochannel interference (CCI) and additive white Gaussian noise (AWGN) is evaluated. For the interference, the authors adopt a model which includes N statistically independent static as well as faded CCI. Various bit-error-rate (BER) performance evaluation results have indicated that the receiver under investigation performs better as compared to other more conventional receiver structures. Especially significant BER improvements are obtained for the static CCI channel. For example, it is shown that with a carrier-to-interference ratio of 14 dB, the performance of a 2-b decision feedback differential receiver outperforms a conventional 2-b differential detector by more than 14 dB (at a BER 10/sup -3/). For the faded CCI, the improvement is less: mainly they result in error-floor reductions of about half an order of magnitude. By comparing the performance of static and faded CCI, it was also found that for a given C/I, the performance of the former would depend on the number of interferers, whereas this is not the case for the latter. >

This paper investigates low complexity detection for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with co-channel interference (CCI). We firstly derive minimum mean square error (MMSE) detection based on sorted QR decomposition (SQRD) and modified MMSE SQRD detection for MIMO-OFDM systems with CCI. Although better performance can be achieved by the new detectors than liner MMSE (LMMSE) detection, the computational complexity is still high due to the required matrix inversion operation. In order to overcome such an issue and design low complexity detection method for MIMO-OFDM systems with CCI, then, we propose an improved MMSE SQRD detector by utilizing a regularization method. The simplification of the regularization parameter calculation in the proposed method is then discussed. Simulation results show that the error performance of the proposed method approaches modified MMSE SQRD detection in presence of CCI, while keeping a much lower complexity.

We consider the design of space-time codes for multiple-input multiple-output (MIMO) systems operated in the presence of co-channel interference (CCI). Based on the pairwise probability of error analysis, we develop a new design criterion that determines the code robustness to CCI (CCI diversity gain). We further develop an algebraic framework for constructing space-time codes that jointly optimize the fading and CCI diversity gains. The proposed framework is general for arbitrary numbers of transmit antennas and quadrature amplitude modulation constellations. Numerical results that quantify the performance gains offered by the proposed techniques are also presented.

This paper investigates network coding with full diversity and a high rate for improving the reliability of wireless communications against the co-channel interference. We consider a cellular network composed of two user terminals that are intended to communicate with a common base station (BS), where a two-way relay node is used to assist the bidirectional communications between the users and BS. We propose an opportunistic network coding (ONC) scheme with the two-way relay, called two-way ONC, which operates depending on whether or not the relay node successfully decodes data packets of the user terminals and BS. Closed-form outage probability expressions of the uplink transmission (from users to BS) and downlink transmission (from BS to users) are derived for the proposed two-way ONC scheme in the presence of co-channel interference over Rayleigh fading channels. We also develop the diversity-multiplexing tradeoff (DMT) of the two-way ONC scheme and show that it obtains the full diversity and an increased multiplexing gain , as compared with conventional one-way relay methods. Additionally, numerical outage probability results demonstrate that the proposed two-way ONC scheme outperforms the conventional one-way relay approaches in terms of improving the communication’s reliability against co-channel interference.