Bit Error Rate Constraint Research Articles

Performance of adaptive modulation with optimal switching thresholds for distributed antenna system in composite channels

In this paper, the performance of distributed antenna system (DAS) with adaptive modulation (AM) over a composite fading channel which takes path loss, Rayleigh fading, and log-normal shadowing into account is studied. Based on target bit error rate (BER), the AM scheme for DAS with average BER constraints is presented. The optimum switching thresholds (STs) for attaining maximum spectrum efficiency (SE) are derived by using Lagrange optimization method. An effective iterative algorithm based on Newton method for finding the optimal STs is proposed. With these thresholds, the closed-form expression of SE and average BER are derived for performance evaluation. Simulation results for SE and BER are in good agreement with the theoretical analysis. The results show that DAS-AM with optimal STs has higher SE than that with conventional fixed thresholds. Moreover, the proposed AM can fulfill the target BER for different signal-to-noise ratios (SNRs).

Optimal Chunk-Based Resource Allocation for OFDMA Systems With Multiple BER Requirements

We investigate the chunk-based resource allocation for OFDMA downlink, where data streams contain packets with diverse bit-error-rate (BER) requirements. Supposing adaptive transmissions based on a number of discrete modulation and coding modes, we derive the optimal scheme that maximizes the weighted sum of average user rates under the multiple BER and total power constraints. With the relevant optimization problem cast as an integer linear program, we show that the optimal strategy can be obtained through Lagrange dual-based gradient iterations with fast convergence and low computational complexity per iteration. Furthermore, a novel on-line algorithm is developed to approach the optimal strategy without knowledge of intended wireless channels a priori.

Analysis of a MIMO-OFDM Wireless Communication System Using a Binary Power Control Scheme with Radio Channel Uncertainties

Here a novel binary power control scheme is presented with radio channel uncertainty which includes path loss, Rayleigh fading, shadowing coefficient, and interference from other users to analyse the performance of MIMO-OFDM wireless communication system. From bit error rate (BER) point of view a two tier system with adjacent interference is taken into account to guarantee QoS. The main objective of this system is to optimize energy efficiency with QoS. Taking both energy efficiency and quality of service (QoS) an energy efficient binary power control with BER constraint algorithm is presented. The performance of this system is analyzed and results of the same are presented to show the effectiveness of the system presented.

Adaptive Bit Allocation Algorithm for OFDM System

For the greedy algorithm required a large number of iterations, this paper proposed one adaptive bit allocation algorithm based on Hughes-Hartogs algorithm which was improved greedy algorithm .Under the constraint of bit error rate and data transmission rate, the algorithm first used the Chow algorithm to allocate some of the bits, and then used the greedy algorithm to allocate the remaining bits. When minimize the total power by this algorithm, the iterations of this algorithm were significantly less than the greedy algorithm. By computer simulation, the results showed that performance of this algorithm was very close to the greedy algorithm, and the number of this algorithm’s iterations was 7.4%~34% of the greedy algorithm.

Adaptive resource allocation for downlink grouped MC-CDMA systems with power and BER constraints

This paper proposes a complete solution to adaptively allocate resource for downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems with the power and bit error rate (BER) constraints. Under frequency-selective fading channels, the whole spectrum is divided into several groups and each user is allocated to a group based on its channel state information (CSI). After grouping, the adaptive modulation algorithm assigns the bit loading and allocates the transmission power for each user according to its effective channel response. Simulation results show that the proposed solution can achieve high throughput, guarantee the required BER, and reduce the blocking probability.

Green Distributed Quality of Transmission Aware Routing and Wavelength Assignment in All-Optical Networks

Abstract The Routing and Wavelength Assignment (RWA) algorithms that consider quality of transmission (QoT) in light-path setup spend more time than their conventional counterparts due to exhaustive search and QoT estimation. This paper proposes distributed Quality of Transmission Aware Routing and Wavelength Assignment (QARWA) algorithm to handle dynamic light-path provisioning in wavelength routed all-optical networks taking energy consumption of optical switch nodes into account. Specifically, the QARWA considers bit-error rate (BER), setup delay, and energy consumption constraints at the same time, and establishes light-paths with small BER, low setup latency, and reduced energy consumption. We present and evaluate an enhanced wavelength-assignment solution in the QARWA to handle the wavelength continuity constraint. In QARWA, a source node determines the connection path by means of the shortest path algorithm and a destination node selects a wavelength based on the BER limitation and decreasing order of setup latency. Relating energy consumption to processing time, we show that QARWA can decrease the total energy consumption by reducing the processing time at each node. Under QARWA, when a node finishes the processing of the last control packet, it makes transition to either sleep state or idle state. Hence, QARWA can provide the best performance since it can reduce processing time in control units, light-path setup latency, and energy consumption of nodes.

Performance Evaluation of Adaptive Modulation System over Mobile Satellite Channels

The performance of an adaptive five-mode M-ary quadrature amplitude modulation (QAM) system under constant power constraint over time-varying land mobile satellite channel is evaluated in this paper. The mathematically-tractable closed-form expressions of performance for outage probability, bit error rate (BER) and average spectral efficiency are deduced by a simple Rician channel model in which the amplitude of the line-of-sight path is represented by the Nakagami distribution. Two adaptive modulation schemes (AMS) are compared, one with the optimal switching thresholds to maximize the average throughput under the constraint of average BER and another with fixed thresholds defined by the given BER tolerance for each modulation. Numeric simulation results show that the M -QAM AMS with optimum switching levels offers performance gains of ~2dB compared to fixed mode at given average spectrum efficiency, and nearly 0.3bps higher average throughput for different Rician K-factor.

Discrete‐rate adaptive modulation with optimum switching thresholds for space‐time coded multiple‐input multiple‐output system with imperfect channel state information

The performance analysis of a space-time coded multiple-input multiple-output (MIMO) system with variable-rate adaptive modulation over flat Rayleigh fading channels for both perfect and imperfect channel state information (CSI) is presented. In this study, the optimum fading gain switching thresholds for attaining maximum spectrum efficiency (SE) subject to an average bit error rate (BER) constraint are derived. The existence and uniqueness of the Lagrange multiplier in the constrained SE optimisation is studied. It is shown that the Lagrange multiplier does exist and is unique for imperfect CSI. On the other hand, the Lagrange multiplier will be unique if the existence condition for MIMO under perfect CSI is satisfied. A practical iterative algorithm based on Newton's method for finding the Lagrange multiplier is proposed. By the switching thresholds, closed-form expressions of the SE and average BER are obtained. Simulation results for SE and BER are in good agreement with the theoretical analysis. The results show that the space-time block coded MIMO system using adaptive modulation (AM-STBC-MIMO) with average BER constraint provides SE better than AM-STBC-MIMO with fixed thresholds, and AM-STBC-MIMO using a BER upper bound, but it has performance degradation in SE for imperfect CSI.

Hybrid adaptive/non-adaptive multi-user OFDMA systems in the presence of user-specific imperfect channel knowledge

In this article, a hybrid multi-user OFDMA scheme which considers different user demands regarding channel access and user-specific imperfect channel quality information (CQI) is analytically described and evaluated. The considered hybrid scheme offers two possible modes to serve the user: firstly, via a non-adaptive mode which applies a discrete Fourier transform precoding to exploit frequency diversity and, thus, does not require any CQI at the transmitter. Secondly, via an adaptive mode which performs an adaptive resource allocation and link adaptation. Since this adaptation to the channel is done based on CQI, the adaptive mode is prone to imperfect CQI which results from estimation errors or time delays. Hence, in case of user-specific imperfect CQI, the question arises which user shall be served adaptively or non-adaptively and which resource shall be allocated to which user such that the system data rate is maximized while fulfilling a certain target bit error rate (BER) and minimum required user data rate. Analytical expressions of the system performance considering imperfect CQI and different user demands are derived. Based on these expressions, algorithms determining which user is served adaptively or non-adaptively subject to the BER and minimum data rate constraints are developed. Simulations show the superiority of the hybrid OFDMA scheme in terms of achievable data rate and user satisfaction compared to conventional pure adaptive and non-adaptive OFDMA schemes in the presence of user-specific imperfect CQI.

Adaptive BER-constraint-based power allocation for downlink MC-CDMA systems with linear MMSE receiver

To facilitate the efficient allocation of limited transmit power, a bit error rate (BER) constraint based power allocation scheme is proposed in this paper for the downlink of multi-carrier code division multiple access (MC-CDMA) systems with linear minimum mean square error (MMSE) receiver. According to the instantaneous channel conditions, the proposed scheme can adaptively allocate the required minimum transmit power on each channel to meet the BER constraint. The simulation results show that the proposed scheme is efficient in reducing the transmit power while meeting BER constraint, and thereby improve the system performance.

Radio Resource Allocation for OFDMA Systems in High Speed Environments

In high speed train (HST) system, real-time multimedia entertainments are very important applications in which a data stream often contains packets with different quality of service requirements. For example, video stream encoded with scalability contains the base layer packets with high quality (HQ) bit error rate (BER) requirement and enhancement layers' packets with low quality (LQ) BER requirement. When a conventional allocation approach, which only considers one BER constraint for one data stream, is applied to orthogonal frequency division multiple access (OFDMA) systems, the BER constraint will be the strictest one among multiple requirements from different types of packets, which leads to inefficient allocation when each data stream has multiple BER requirements. This paper aims to develop novel resource allocation approach by considering multiple BER requirements for different types of packets in one data stream. In order to not only simplify the resource allocation, but also to compensate for the channel estimation error caused by Doppler shift in the HST environment, a proper number of contiguous subcarriers are grouped into chunks and spectrum is allocated chunk by chunk. Simulation results show that the developed resource allocation scheme outperforms the conventional scheme, particularly when the BER ratio of HQ packets to LQ packets is larger than one. Furthermore, in order to reduce the complexity of resource allocation further, an empirical allocation scheme is proposed to allocate better chunks to HQ packets. It is shown that the performance of the empirical allocation scheme is quite close to that of the optimal scheme.

Link adaptation for physical layer security over wireless fading channels

A secure link adaptation framework is proposed, which exploits the inherent fluctuations of wireless fading channels for high-performance communications and physical layer security in the presence of an eavesdropper. The authors use very sharp channel codes intended for reliability and demonstrate that they also provide security, when successfully incorporated in the link adaptation design framework and the security constraint is not very stringent. Two scenarios are considered in which the transmitter has access to the eavesdropper channel state information either instantaneously or statistically. The proposed secure link adaptation framework is formulated to maximise the spectral efficiency of the communication, whereas both reliability and security constraints are provisioned. Different designs are considered when the security constraint is quantified by instantaneous bit error rate (BER), average BER or leakage probability. For the problem with instantaneous BER constraint, an efficient analytical solution and a numerical solution are presented. A closed-form analytical solution is also provided for secure link adaptation with average BER constraint, whereas the problem with the leakage constraint is tackled numerically. Extensive results and detailed analysis are provided to draw insights on the effects of different design parameters on the performance.

Distributed Approach for Power and Rate Allocation to Secondary Users in Cognitive Radio Networks

We consider a multichannel cognitive radio network where multiple secondary users (SUs) share a single channel and where multiple channels are simultaneously used by a single SU to satisfy their rate requirements. We attempt to evaluate the optimal power and rate distribution choices that each SU has to make to maintain their quality of service (QoS). Our measures for QoS include bit error rate (BER) and minimum rate requirement. We design a QoS-constrained bi-objective optimization problem with the objective of minimizing transmit power and maximizing rate. Unlike prior efforts, we transform the BER constraint into a convex constraint to guarantee optimality of the resulting solution. Our interest in this paper is to develop a user-based distributed approach to solve the optimization problem and compare the solution with the centralized approach. We employ dual decomposition theory to derive three different formulations of the distributed problem. Simulation results demonstrate that optimal transmit power follows the “reverse water filling” process and that rate allocation follows signal-to-interference-plus-noise ratio (SINR). We show that the solutions from the distributed formulations follow the centralized solution.

Chunk-Based Resource Allocation in Multicast OFDMA Systems with Average BER Constraint

The resource allocation problem for the downlink of Orthogonal Frequency Division Multiple Access (OFDMA) wireless multicast systems is investigated. It is assumed that both the Base Station (BS) and each user are equipped with a single antenna and the allocation unit is not the subcarrier, as in conventional OFDMA systems, but a set of contiguous subcarriers (chunk). The aim of the proposed efficient algorithm is to maximize the total throughput subject to constraints on total available power and average Bit Error Rate (BER) over a chunk. Simulation and complexity analysis are provided to support the benefits of chunk-based resource allocation to multicast OFDMA systems.

The Application of M-Ary Quantum Evolutionary Algorithm in Bit and Power Allocation for OFDM System over the Power Line

Adaptive resource allocation in orthogonal frequency division multiplexing (OFDM) systems is a very promising technique to improve spectral efficiency. According to actual transmission behavior of the channel environment over low voltage power line, M-ary Quantum Evolutionary Algorithm (MQEA) is proposed to allocate bit and power on different sub-carrier channel, which maximizes the total data rate of the system in a downlink transmission with a total power and bit-error rate(BER) constraints. Simulation results show that the proposed algorithm achieve a higher data rate.

EVALUATION OF OPTIMAL TRANSMIT POWER IN WIRELESS SENSOR NETWORKS IN PRESENCE OF RAYLEIGH FADING

Design of an energy efficient wireless sensor network (WSN) has emerged as an important research area. Minimizing energy consumption is the primary objective for WSN. WSN is usually characterized by tiny size, low cost and low transmission power. So optimization of transmission power is of great importance. Optimal transmit power not only achieves better network lifetime but also reduces inter-node interference significantly. In this paper we carry out simulation studies to investigate the effects of Rayleigh fading on the performance of WSN and optimal transmit power in presence of Rayleigh fading is derived. The effects of bit rate and Rayleigh fading on optimal transmit power are investigated under several network conditions. In this paper the network performance is estimated in terms of a quality of service (QoS) constraint given by the maximum tolerable bit error rate (BER). The derived optimal transmit power maintains a minimum BER constraint. The impact of fading on critical bit rate i.e., the bit rate below which a desired BER can not be achieved with any amount of transmit power is also studied.

Energy-Efficient Route Optimization for Adaptive MPSK-Based Wireless Sensor Networks

We study a certain route configuration problem via optimization theory. We consider the optimal bit error rate (BER) and transmission rate allocations on each hop, subject to overall BER and delay constraints for a designated route. The pivot of the problem lies in the delay constraint, which divides the problem into two cases--the loose and the tight delay case. In the former, analytical solutions are obtained by applying the Karush-Kuhn-Tucker (KKT) theorem. Specifically, we discover in this case that for a given target BER, the optimum solutions are only related to the hop lengths in the route. When the delay constraint is tight, a mapping can be used to reduce the dimension of the problem by a factor of two; a numerical optimization algorithm has to be used to find the optimum. Simulation results show that by optimally configuring a chosen route, substantial energy savings could be obtained, especially under tight delay constraints. Simulation also reveals that a performance limit is reached as the number of hops increases. A parameter determining this limit is defined, and physical explanations are given accordingly.

Adaptive power loading with BER-constraint for OFDM systems

A novel adaptive power loading algorithm with the constraint of target overall bit error rate (BER) for orthogonal frequency division multiplexing (OFDM) systems is proposed in this article. The proposed algorithm aims to minimize the required transmit power with fixed data rate and uniform (nonadaptive) bit allocation, while guaranteeing the target overall BER. The power loading is based on the unequal-BER (UBER) strategy that allows unequal mean BERs on different subcarriers. The closed-form expressions for optimal BER and power distributions are derived in this article. Simulation results indicate the superiority of the proposed algorithm in terms of BER performance and algorithmic complexity.

QoS constrained resource allocation to secondary users in cognitive radio networks

In this paper, we consider a multi-channel cognitive radio network (CRN) where multiple secondary users share a single channel and multiple channels are simultaneously used by a single secondary user (SU) to satisfy their rate requirements. In such an environment, we attempt to evaluate the optimal power and rate distribution choices that each secondary user has to make in order to maintain their quality of service (QoS). Our measures for QoS include signal to interference plus noise ratio (SINR)/bit error rate (BER) and minimum rate requirement. We propose two centralized optimization frameworks in order to solve for the optimal resource management strategies. In the first framework, we determine the minimum transmit power that SUs should employ in order to maintain a certain SINR and use that result to calculate the optimal rate allocation strategy across channels. In the second framework, both transmit power and rate per channel are simultaneously optimized with the help of a bi-objective problem formulation. Unlike prior efforts, we transform the BER constraint into a convex constraint in order to guarantee optimality of the resulting solutions. Simulation results demonstrate that in both frameworks, optimal transmit power follows “reverse water filling” process and rate allocation follows SINR. We also observe that, due to the ability to adapt both power and rate simultaneously to attain a certain BER, the joint optimization framework results in a lower total transmit power than the two-stage approach.

QoS-Aware Wavelength Assignment With BER and Latency Constraints for All-Optical Networks

Physical impairments originating from optical fiber components and intermediate switching nodes can be the dominant reason calls are blocked in wide-area all-optical wavelength division multiplexing (WDM) networks. When a centralized network controller is used, estimating the impact of the physical impairments on the quality of a lightpath before provisioning it can cause a significant delay. In this paper, quality of service aware wavelength assignment algorithms are proposed that consider both bit-error rate (BER) and latency constraints. A novel wavelength assignment technique called wavelength ordering is shown via simulation to reduce the call blocking probability resulting from both physical impairments and excessive processing delay caused by channel BER estimation.