On the Bandwidth Efficiency of D2D Link Adaptation Under Co-channel Interference

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.

Ultra-dense networks (UDNs) have been widely regarded as a promising technology to meet higher requirements of the fifth generation (5G) network. However, densely deployed femtocells bring an unprecedented challenge of importing severe co-channel interference (CCI), which greatly limits the performance of the network. Therefore, interference management in UDNs is particularly important. The conflict-graph is widely recognized as the representation of underlying interference constraints of the network. Most prior studies establish conflict-graphs based on accurate geographical distance information which is usually unavailable by the network operators in practice. A more practical neural network based conflict-graph construction approach, which utilizes up-link signal to interference plus noise ratio (SINR) data and up-link resource block (RB) allocation data, is proposed in this paper. These data are used to train a neural network for predicting the up-link SINR under single interfering user conditions. Utilizing the predicted SINR data as the edge weights of the constructed conflict-graph considers both the influence of inter-user interference and the interference tolerance ability of each user, which better reflects the resource reuse conflict between users. Users can collaborate and coordinate their resource allocation strategies according to the constructed conflict-graph so as to mitigate severe CCI in the network. Therefore, the proposed approach facilitates the realization of the intelligent resource allocation optimization. Furthermore, the proposed conflict-graph construction approach achieves quite a high accuracy, which has been verified by simulation results.

This paper investigates power allocation for D2D communications in a Heterogeneous Network (HetNet) which includes a macro cell and pico cells, whereas femto cells are distributed inside. The objective is to minimize the total power consumption of D2D transmitter while satisfying a set of Quality of Service in D2D receivers and cellular users communication interference. To this end, we first obtain expression for the formula of signal to interference plus noise ratio (SINR) and spectral efficiency of each D2D receiver. Then, an optimization problem is formulated to minimize the total transmit power of D2D transmitters subject to QoS constraints. It is shown that this optimization problem is linear programming and it can be solved in polynomial time with standard tools. In addition, the maximization value of D2D pair transmission rates are determined with fixed cellular users parameters.

In order to offload base station (BS) traffic and to enhance efficiency of spectrum, operators can activate many Device-to-Device (D2D) pairs or links in LTE networks. This increases the overall spectral efficiency because the same Resource Blocks (RBs) are used across cellular UEs (CUEs) (i.e., all UEs connected to BS for both C-Plane and D-plane communication) and D2D links (i.e., where the UEs are connected to BS only for C-plane communication). However, significant interference problems can be caused by D2D communications as the same RBs are being shared. In our work, we address this problem by proposing a novel scheduling algorithm, Efficient Scheduling and Power control Algorithm for D2Ds (ESPAD), which reuses the same RBs and tries to maximize the overall network throughput without affecting the CUEs throughput. ESPAD algorithm also ensures that Signal to Noise plus Interference Ratio (SINR) for each of the D2D links is maintained above a certain predefined threshold. The aforementioned properties of ESPAD algorithm makes sure that the CUEs do not experience very high interference from the D2Ds. It is observed that even when the SINR drop (i.e., maximum permissible drop in SINR of CUEs) is as high as 10 dB, there is no drastic decrease in CUEs throughput (only 3.78%). We also compare our algorithm against other algorithms and show that D2D throughput improves drastically without undermining CUEs throughput.

In this chapter, an effective blind source separation (BSS) algorithm is applied to solve the co-channel interference problem in wireless communication systems. Algorithms developed for this purpose must not only have the capability of working in the complex domain and improving output signal to interference plus noise ratio (SINR), but also have relatively low computational complexity. We propose a fast Fourier transform (FFT)-based algorithm called feedback independent component analysis (FebICA) that is able to blindly separate complex modulated digital signals. By applying this algorithm to communication signals, it is observed that it has the advantages of SINR gain improvement as well as low computational complexity. The performance of the FebICA algorithm is shown to be better than the joint approximate diagonalization of eigen-matrices (JADE) algorithm in terms of the output SINR and requires lower computational complexity than the analytical constant modulus algorithm (ACMA). The algorithm is also shown to be more robust with increasing number of sources compared to other algorithms. The separation performance by using the collected field data has also been demonstrated.

Signal to interference plus noise ratio (SINR) based call admission control (CAC) scheme admits incoming calls as long as the measured SINR is higher than threshold value (SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ). If a high value of SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is chosen, the signal quality will improve but this will increase the blocking probability (p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> ), and as a result, will decrease the network utilization. On the other hand, a low value of SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> will reduce p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> , however degrades the signal quality and increases outage probability (p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ). Hence, how to choose appropriate SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is very important. In this paper, we focus on the following aspects. Firstly, an accurate upper bound of SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is derived. Secondly, based on the upper bound of SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> and a lower bound from other literature, we design a fuzzy logic controller (FLC), which can adaptively adjust SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> according to the number of active users (AUs) in a cell and average arriving traffic intensity (AATI) in Erlang per cell. Finally, network performance based on FLC is compared with that based on optimal fixed SINR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> . Numerical results show that the proposed scheme based on FLC has better performance than the optimal fixed threshold CAC scheme.

For future high-speed orthogonal frequency division multiplexing (OFDM) wireless communications, two major system requirements will exist: broadband transmission and rich interference elimination. Because of its broadband nature and limited frequency allocations worldwide, interference from co-located wireless LAN operating in the same frequency band will become a serious deployment issue, since interference may have a large amount of multipath and also have similar levels of received power compared to the desired signal. This paper presents recent investigations in OFDM smart antenna systems, more specifically the signal properties in the frequency domain, for co-channel interference detection and rejection. A novel architecture is proposed in this paper, which is a complexity-reduced frequency-domain technique using subcarrier clustering. Research results are presented and show that the proposed architecture can achieve high performance with low complexity, within a rich multipath environment with low signal to noise plus interference ratio (SNIR).

The problem of cochannel interference (CCI) suppression using a noise-plus-interference whitening matched filter (WMF) is addressed. Binary phase-shift keying modulated transmission over a Nakagami-m fading channel is considered in a bandlimited microcellular wireless system. It is shown that the signal-to-interference-plus-noise ratio (SINR) of the WMF can not exceed that of the conventional matched filter (CMF) receiver for synchronous CCI, but in the asynchronous channel, CCI whitening can be used to improve receiver performance. The SINR-maximizing filter (SINRMF) in an asynchronous channel is derived and shown to be composed of a WMF followed by a discrete time filter. The SINRs of the WMF and SINRMF receivers are analytically evaluated for a standard raised-cosine (RC) and a Beaulieu-Tan-Damen pulse. It is shown that for the RC pulse, the WMF can achieve a SINR gain as large as 1.76 dB over the CMF receiver provided that the transmission is free of intersymbol interference (ISI). The SINR of the ISI-impaired system is also evaluated and the conditions under which this system can achieve close to ISI-free SINR are studied. The SINR is evaluated for the SINRMF and it is shown that this filter can restore much of the SINR loss incurred due to ISI introduced by the WMF.

Device-to-device (D2D) communication is one of the promising technology of the fifth-generation (5G) network. In D2D, the devices are in close proximity to each other communicate directly with or without depending upon the base station (BS), resulting in large gain, low latency, and high energy efficiency. Also, it improves the spectral efficiency by sharing the spectrum resources with cellular mobile users (CMUs). Despite these advantages, co-channel interference and eavesdropping attack on the D2D links are two major challenges. To overcome these issues, we used the power domain non orthogonal multiple access (PDNOMA) techniques with the D2D mobile groups (DMGs) under the social-domain scenario. The successive interference cancellation technique of PD-NOMA in the DMGs mitigate the intra-user and co-channel interference among the D2D receivers (DDRs), resulting in an increase in signal to interference noise ratio (SINR) and better quality of services. Furthermore, to improve the spectral efficiency, and reduce the security risk of the eavesdropper on the DMGs over each resource block (RB) in the presence of dynamic channel environment of imperfect channel state information, we used the coalition game approach. The simulated results show the proposed scheme achieves 5.5% and 27.77% higher sum rate and ensure 8.3% and 41.6% higher information secrecy as compared to first-order algorithm (FOA) and orthogonal frequency division multiple access (OFDMA) schemes.

Low‐power machine‐type communications devices in machine‐to‐machine networks are expected to operate autonomously for years, or even decades. Meanwhile, device‐to‐device (D2D) communications make large benefits on users' data rate and power consumption because of the proximity between potential D2D transmitters and receivers. In this paper, we facilitate machine‐type D2D links where the machine‐type communications devices are connected to a nearby device, such as a number of sensors connected to a gateway that acts as the relay towards the evolved NodeB. A challenging problem is the co‐channel interference caused by spectrum sharing between underlaying machine‐type D2D links and traditional cellular user equipments (CUEs). Therefore, we consider joint mode selection, radio resource allocation and power control to improve overall system data rate and reduce average traffic delay. We first formulate a problem to maximise the sum of users' utilities with signal‐to‐interference‐plus‐noise and power constraints for both D2D links and CUEs. Furthermore, we adopt the coalition formation game with transferable utility to solve the formulated problem. In the game model, the D2D links and CUEs that share the same resource block pair form a coalition, and the coalition formation decisions are determined by the best‐reply rule. In addition, ‘experimentation’ is introduced in the coalition formation process to improve the effectiveness of the final coalition structure. Simulation results show that the proposed scheme outperforms the scheme with heuristic greedy algorithm in terms of overall system throughput, average traffic delay and users' fairness. Copyright © 2015 John Wiley &amp; Sons, Ltd.

This paper presents a theoretical analysis of subband adaptive array combining the cyclic prefix transmission scheme (SBAA-CP) in a multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). We also show that if the output SINR is plotted versus the delay of the delay path then the output SINR of SBAA-CP is in effect the SINR of SBAA shifted by C samples to the right.

Multicarrier code division multiple access (MC-CDMA) systems are well suited for high data rate wireless multimedia services, due to their ability to convert frequency-selective fading channels to distinct flat fading channels with low complexity fast Fourier transform (FFT) devices. However, when multiple users are present, the performance of MC-CDMA systems is degraded by the multiuser interference (MUI) when the channel is frequency-selective. In order to mitigate MUI, we present a joint algorithm that combines transmit power control, antenna array processing and multiuser detection at the receiver. Interestingly, the frequency-selectivity that entails the MUI also provides multipath diversity which can help suppress the MUI. Performance of the algorithm in a number of MC-CDMA system models is evaluated in terms of the average transmit power to achieve the target signal to interference plus noise ratio (SINR). Simulations confirm the outstanding performance of this algorithm compared with the existing ones in MC-CDMA systems.

We propose and compare two receiver structures that combine optimum receive beamforming, respectively, with the conventional Alamouti space-time block code (STBC) decoder and the minimum mean squared error (MMSE) decoder. The beamforming process suppresses co-channel interference (CCI) by maximizing the uplink signal to noise plus interference ratio (SINR). Co-antenna interference (CAI) is suppressed at the Alamouti STBC decoders. Simulation results show that both receivers significantly improve the bit error rate (BER) performance and increase the achieved channel capacities. The comparison of the two receivers indicates that, in the presence of beamforming, the conventional Alamouti decoder outperforms the MMSE decoder when there are sufficient degrees of freedom (DOF) at the receiver antenna array.

In this paper, we propose a fully-distributed random access protocol for the device-to-device (D2D) communication in a cellular network. The D2D communication can provide a significant capacity gain by enabling a cellular network to offload data traffic to direct communication links between devices (i.e., D2D link). However, a D2D link can generate serious interference to other D2D links as well as cellular devices without any proper interference control mechanism. Compared to centralized resource allocation and power control schemes for the D2D communication, a distributed scheme is advantageous in that it has smaller control overhead and is more responsive to traffic demands. To protect a D2D receiver, the proposed scheme employs a collision avoidance mechanism that creates an exclusion region around the D2D receiver, where interferers are prohibited from transmitting a signal. We analyze the proposed scheme by assuming that the locations of devices follow a Poisson point process. By simulation, we show that the analysis results accurately match the simulation results and that the proposed scheme outperforms a distributed D2D scheme without collision avoidance by a very wide margin.

This paper considers a device-to-device (D2D) underlaying cellular network where an uplink cellular user communicates with the base station while multiple direct D2D links share the uplink spectrum. This paper proposes a random network model based on stochastic geometry and develops centralized power control algorithm. The goal of the proposed power control algorithm is two-fold: ensure the cellular users have sufficient coverage probability by limiting the interference created by underlaid D2D users, while also attempting to support as many D2D links as possible. This paper adopts the two level control strategy: Cellular link SINR(signal-to-interference-plus noise ratio) and sum rate maximization, to ensure the cellular communication and improve the coverage probability of D2D and cellular links. Numerical results show the gains of the proposed power control algorithm and accuracy of the analysis.KeywordsPower controlStochastic geometryPoisson point processCoverage probability