Effect Of Imperfect Power Control Research Articles

Internet of Things (IoT) for MC-CDMA-Based Cognitive Radio Network (CRN) in 5G: Performance Results

Both the internet-connected devices, i.e. IoT and Cognitive Radio Network (CRN) are considered to be the future technologies for the fifth generation of cellular wireless standards (5G). On the one hand, Internet of Things (IoT) focuses primarily on how to allow general objects to see, hear, and smell their own physical environment and make them connected to share the observations. On the other hand, a CRN is based on a complex spectrum allocation system, and licenced primary users (PUs) or unlicenced secondary users (SUs) are allowed to share the spectrum, provided they do not cause significant interference. The IoTs are meaningless if IoT objects are not equipped with cognitive radio capability. In cognitive radio, it is important to control the transmission power of SUs so that the interference should not be harmful to the quality of service of PUs. In this paper, the authors addressed the effects of imperfect power control between primary users (PUs) and the secondary users (SUs) of an IoT-based CRN. The effect of the co-channel interference (CCI) and adjacent channel interferences (ACIs) occurring in CRN using MC-CDMA system is also analysed. A new expression of the signal-to-interference-noise ratio (SINR) for CRN-based MC-CDMA system over a Nakagami-[Formula: see text] fading channel with imperfect power control condition is derived and investigated. The performance of IoT-based CRN using MC-CDMA system over the frequency selective multipath fading channel is examined with varying the number of users, the SINR per bit, number of fading path and number of sub-carriers. From the simulation results, we have seen that the SINR performance is affected by these parameters. The result of the analysis will provide relevant information to design the physical layer protocol for high-speed IoT-based CRN system for 5G.

Performance Analysis of Reactive Symbol-Level Jamming Techniques

The reactive symbol-level jamming (SLJ) technique is a simple but practical technique to disable or disrupt malicious communication links. After sensing the transmission and detecting the digital modulation scheme of the malicious transmitter, a communication node with the reactive SLJ technique, called a reactive jammer, generates random digital modulation symbols and then sends them to the malicious receiver. In this correspondence, we mathematically analyze both uncoded and coded bit error rate (BER) at the malicious receiver under not only reactive SLJ, but also Gaussian SLJ techniques. In particular, we consider the partial jamming scenario, in which a portion of symbols in a data frame are affected by the SLJ, which is a practical scenario under the reactive jamming techniques. We also consider the effect of imperfect power control and channel estimation error of the reactive jammer on the BER performance at the malicious receiver.

Revisiting and Optimizing the Design of the Timer-Based Distributed Selection Scheme for Tackling Imperfect Power Control

Opportunistic selection improves the performance of a multi-node wireless system by exploiting multi-user or spatial diversity. In it, the nodes are sorted in the descending order of their metrics, which captures the utility of a node to the system if selected, and the best node with the highest metric is selected. We analyze the effect of imperfect power control on the conventional timer with power control scheme, which selects the best node in a distributed manner, and quantify the extent by which it reduces the probability of selecting the best node and increases the probability of selecting a non-best node. We then redesign it to ameliorate the impact of imperfect power control. Our systematic approach eschews several ad hoc assumptions implicit in the design of the conventional timer scheme, and jointly optimizes its various parameters to maximize the probability of selecting the best node in the presence of imperfect power control. We present several structural insights, including asymptotic ones, about the optimal scheme, which also enable it to be determined with much lower computational complexity. Our benchmarking results show that it is scalable and outperforms the conventional schemes.

Capture-Induced, Fast, Distributed, Splitting Based Selection with Imperfect Power Control

Opportunistic selection selects the node that improves the overall system performance the most. Selecting the best node is challenging as the nodes are geographically distributed and have only local knowledge. Yet, selection must be fast to allow more time to be spent on data transmission, which exploits the selected node's services. We analyze the impact of imperfect power control on a fast, distributed, splitting based selection scheme that exploits the capture effect by allowing the transmitting nodes to have different target receive powers and uses information about the total received power to speed up selection. Imperfect power control makes the received power deviate from the target and, hence, affects performance. Our analysis quantifies how it changes the selection probability, reduces the selection speed, and leads to the selection of no node or a wrong node. We show that the effect of imperfect power control is primarily driven by the ratio of target receive powers. Furthermore, we quantify its effect on the net system throughput.

EFFECT OF IMPERFECT POWER CONTROL ON PARALLEL INTERFERENCE CANCELLATION FOR CDMA

This paper presents a study of the effect of imperfect power control on the performance of a Partial Parallel Interference Cancellation (PPIC) multiuser receiver. We show that the PPIC receiver can absorb the effect of imperfect power control to a great extent compared with other types of receivers. Additionally, the effect of imperfect power control on the optimum weights of the PPIC receiver is considered. It is found that imperfect power control causes the receiver to become more susceptible to performance degradation as a result of deviation from optimal weights.

Analysis of DS-CDMA System Supporting Heterogeneous Traffic With Decorrelating Detector

Single-cell and multiple-cell direct-sequence code-division multiple-access (DS-CDMA) systems supporting heterogeneous traffic are investigated when decorrelating detector is used at receiver. Theoretical analyses and numerical examples are presented to study the effect of imperfect power control on the system performance of the reverse link. As to the forward link, the system performance is analyzed and the power allocation problem at base stations is formulated as a constrained optimization problem. Two algorithms, namely, the optimal algorithm and the unit transmission power allocation (UTXPA) algorithm, are proposed to solve this optimization problem. Computer simulations are presented to compare the performance of the proposed algorithms.

Performance analysis of M-ary DS-CDMA systems with imperfect power control

The system performance of an M-ary DS-CDMA system is investigated for a coherent reception of uplink signals. In addition, the effect of imperfect power control resulting in a lognormal distribution of signal power on the system performance is also considered. A theoretical expression for the bit error rate (BER) performance of M-ary DS-CDMA systems with imperfect power control is achieved. The results show that the M-ary orthogonal modulation can offer performance improvement in terms of BER and capacity, even under imperfect power control. However, the advantage of M-ary technology is almost lost due to bad power control, even increasing the M value. For a specified performance, the derived results can be used as guides in evaluating the required quality of power control for an M-ary DS-CDMA system. Simulation results verify the theoretical derivations.

Reverse link erlang capacity of multiclass cdma cellular system considering nonideal antenna sectorization

In this paper, the effect of antenna sectorization in the reverse link erlang capacity of a multiclass code-division multiple-access (CDMA) cellular system is studied. Traditionally, it has been considered that the capacity is multiplied by a factor equal to the number of sectors introduced. This is true only in the ideal antenna sectored system. However, due to the nonideal antenna radiation pattern, the sectorization gain is smaller than the number of sectors. Our contribution is the analytical study of the effect of nonideal antenna patterns on the capacity of a multiclass CDMA system. We also present an approximated analysis of the erlang capacity, considering that blocking in CDMA occurs when the interference reaches a predetermined level above the background noise level of mainly thermal origin. The analysis also includes the effects of imperfect power control and service activity detection. We found that the capacity losses due to the consideration of antenna sectorization are about 20.20% for the nonideal antenna radiation pattern and 30.32% for the evaluated commercial radiation pattern. This percentage loss implies that the sectorization gain is approximately 2.39 for a nonideal antenna pattern and 2.09 for a commercial antenna pattern in typical conditions, /spl mu/=4 and /spl alpha/=8 dB.

The performance of turbo coding over power-controlled fading channel in Ka-band LEO satellite systems

The integration of power control and turbo coding is adopted to achieve reliable communications over Ka-band code-division multiple-access (CDMA)-based low Earth orbit (LEO) satellite systems. The effect of imperfect power control on the bit error ratio (BER) performance is analyzed, and the upper bounds on BER are also derived for the case of slow and fast imperfect power control. The analytical and simulation results show that power-control error (PCE) degrades the BER performance of turbo-decoded systems significantly in the waterfall region. In the region of the error floor, the degradation effect slows down and the BER obtained under imperfect power control eventually converges with the BER under perfect power control. Moreover, in the waterfall region, the correlation characteristics of the PCE fluctuation do not degrade the BER performance as anticipated.

Overlaying CDMA systems with interference differentials

In the future wideband CDMA cellular systems, services with different data rates, Quality of Service requirements, and power constraints will coexist in a cell. Multiband CDMA may be used to accommodate these heterogeneous service requirements by overlaying the subbands containing different services within the same spectrum band. In this paper we will derive the capacity of multiband CDMA systems in terms of the number of users in each service class, and the corresponding bandwidth utilization. Both reverse and forward links are analyzed. The effects of imperfect power control, other cell interference, and soft handoff are considered. The performance results are compared with the single-band system where all services share the entire system bandwidth.

The Effect of Satellite Diversity on Service Availability, Blockage Probability and System Capacity over Rician-Lognormal Channel of NGEO Satellite Systems

ABSTRACTIn this paper, we analyse the performance of the downlink of a Non-Geostationary Earth Orbits (NGEO) mobile satellite channel based on Direct Sequence-Code Division Multiple Access (DS-CDMA) in the presence of shadowing, fading and interference from other satellites visible at the same time. In particular, the performance of QPSK convolutionally coded DS-CDMA over a Rice-Lognormal channel is analysed in depth. The provision of such a service requires that the user must have sufficient link quality for the duration of call. To have sufficient link quality, the user must have an adequate power to overcome the path loss and other physical impairments and maintain the performance of the system. The most important factor in determining the performance is the probability of signal shadowing which depends both on the user environment and on the constellation.The paper addresses the exploitation of satellite diversity in the Rician-Lognormal channel. In particular, we focus on the impact of satellite diversity on service availability, path blockage, call dropping and system capacity, considering the effects of imperfect power control, shadowing and voice activity. Concatenated codes are used to provide different bit error probabilities for different services.We show that satellite diversity is an essential in providing service availability especially in urban and suburban areas. Also we show the impact of satellite diversity on the system capacity under different environments, which is related to elevation angle, latitude and the nature of the user terminal environment.

Performance analysis of a multicell DS-CDMA system with base station diversity

The performance of a multicell DS-CDMA cellular system with base station diversity is studied taking into consideration the effects of imperfect power control, multipath fading, shadowing and the dependence of propagation losses to a different base station from a mobile user. It is assumed that a mobile user is connected to the base station that provides the least attenuation among a set of closest uniformly correlated base stations. Analytical expressions are derived for the average probability of error of binary phase shift keying modulated signals for both the reverse link and the forward link. The channel is assumed to undergo correlated lognormal shadowed Rayleigh fading. Analytical results show that base station diversity significantly improves system performance.

Partial successive interference cancellation in hybrid DS/FH spread-spectrum multiple-access systems

Partial successive interference cancellation is considered in hybrid DS/FH spread-spectrum multiple-access (SSMA) systems. We first show that the lowest BER attained by employing full interference cancellation in DS/SSMA systems can almost be achieved by employing a partial interference cancellation in hybrid DS/FH systems. The reduction in the number of cancellations translates into an alleviation of correlator speed requirements and a reduction in delays incurred in interference cancellations. The optimal number of frequency slots that minimizes the BER is investigated as a function of the number of interference cancellations. The effect of imperfect power control on the BER is investigated.

DS-CDMA with power control error using weighted despreading sequences over a multipath Rayleigh fading channel

Closed-form solutions for the average bit error rate (BER) performance of a direct-sequence code division multiple-access system with imperfect power control are derived for both coherent and noncoherent reception operating over a multipath Rayleigh fading channel. The RAKE structure receivers under consideration employ despreading sequences weighted by adjustable exponential chip waveforms optimized for multiple-access interference rejection. The chip-weighting waveforms employed are determined only by one parameter /spl gamma/ which leads to easy tuning of the waveforms in practice to achieve the best performance. The results indicate that the number of active users supported at a given BER for the case of /spl gamma/ tuned to maximize the average signal to interference plus noise ratio H/spl circ/ is much larger than the case of /spl gamma/=0 (fixed or rectangular despreading sequence). It is shown that imperfect power control affects the irreducible BER for the case of /spl gamma/=0. On the other hand, the effect of imperfect power control on the BER performance for the case of /spl gamma/ tuned to maximize H/spl circ/ is equivalent to a reduction in the average signal-to-noise ratio, and, hence, system performance can be compensated by increasing the transmitter power. It is further shown that the effect due to imperfect power control on BER performance is significant while that on the maximum value of H/spl circ/ obtained by tuning /spl gamma/ is rather insignificant.

Effects of imperfect power control and user mobility on a CDMA cellular network

Code-division multiple-access (CDMA) is one of the major candidate access techniques for third generation systems. A great deal of effort has been devoted to the study of the capacity it can support. This paper presents analytical derivations which allow the determination of the link availability in the presence of user mobility and power control imperfections in a CDMA network; moreover, it provides the guidelines which permit the implementation of a simple and flexible simulation tool which is independent of the specific CDMA implementations. As a matter of fact, the reported concepts can be applied to any asynchronous CDMA system, i.e., they hold both for the American Standard IS-95 and for the European Community Standard developed in the framework of the RACE CODIT Project.

Effect of imperfect power control on acquisition performance in a DS/CDMA system

the proposed algorithm with the same truiicafion length in the Viterbi decoder. The results show that the error-correction capa- bility of the proposed algorithm is significantly improved over that of the existing algorithm. When truncation length is set to 25 and channel error is 5%, the existing algorithm cannot correct 0.242% of errors, while the proposed algorithm reduces it to 10.088% These figures become prominent when truncation length is set to 15; 2.939% (existing algorithm) against 0.746% (proposed algo- rithm) uncorrected errors. As shown in Fig. 4, the truncation length of proposed algorithm can be set to the value less than that of the existing algorithm to obtain the same error rate. c

Performance evaluation for cellular CDMA

The authors consider the performance of a cellular radio, direct-sequence code-division multiple access, (CDMA) system. The base-to-mobile link is modeled as a flat Rayleigh fading channel, with all signals transmitted from a given base station fading in unison. For the mobile-to-base link, the authors use a similar model, except that the waveforms from all users are assumed to experience independent fading. The effects of imperfect power control are shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of imperfect power control on cellular code division multiple access system

An analytical model is developed to evaluate the performance of a cellular direct-sequence code division multiple access (DS CDMA) system with a perfect as well as an imperfect power control scheme and without power control considering the near-far effect. The effect of the three schemes on the performance is compared.