Maximal Ratio Combining Scheme Research Articles

Investigation of Correlated Rayleigh Fading Channel with Alamouti’s STBC-MRC system

The effect of antenna diversity for a double transmit and multiple receive antenna supported wireless communication system is investigated, that employs multi user Alamouti’s space time block coding (STBC) and maximal ratio combining (MRC) scheme on secured text message transmission. The FEC encoded Alamouti’s-MRC transmission system under investigation implements RSA cryptographic algorithm and deploys various multi-level digital modulations (16-PSK and 16-QAM) techniques over an Additive White Gaussian Noise (AWGN) and Correlated Rayleigh Fading Channels. Rayleigh channel correlation parameter ρ is varied from 0 to 0.9. It has been observed from the study that in case of without receive antenna diversity the system shows comparatively worst performance in 16PSK scheme and satisfactory performance in 16-QAM for the correlation parameter ρ=0.9. It can also be seen that the system performance is improved with increase in number of receive antenna. The performance analysis shows that with implemented Alamouti’s-MRC scheme under 16-QAM digital modulation, the system provides excellent performance over a significantly low signal to noise ratio (SNR) values.

Frequency acquisition synchronization for multiple antenna systems

SUMMARYIn this paper, we consider the problem of frequency acquisition synchronization by using multiple antennas over wireless fading channels. We introduce frequency synchronization with different combining schemes including space diversity and time diversity. Their performance is estimated for a Rayleigh fading channel with an analysis both theoretically and by simulation. We investigate the relationship between the mean squared error (MSE) and the average signal‐to‐noise ratio (SNR) for combining of different blocks and antennas. Both the carrier frequency offset and the sampling frequency offset are estimated when multiple antennas are utilized for signal transmission. The estimation with maximum ratio combining (MRC) scheme is presented in detail, and the estimation with selection combining scheme and equal gain combining scheme are introduced briefly. The simulation results explicitly show that the performance of the frequency acquisition synchronization with MRC scheme is better than that of others and that the MSE at low SNR is not very close to the Cramér–Rao low bound in multiblock combining frequency synchronization. Furthermore, the results address that in order to improve the performance, the total number of receive antennas will be increased exponentially. Copyright © 2013 John Wiley & Sons, Ltd.

Performance Comparison of RI & TBI Based System in Fading Environment Using MRC Scheme

In interleave division multiple access (IDMA), interleavers are used for the user separation. This paper presents the performance comparison between random and tree based interleaver based IDMA system, in fading environment. We also know that Maximal Ratio Combining (MRC) diversity approach is popularly used to mitigate the fading problem in any wireless system so here MRRC scheme is used with both RI & TBI based system to mitigate fading. The approach involves receiver diversity analysis as 1:2 antenna systems in fading environment; no. of antennas can be increased to improve diversity order.

Enhancement of Performance of Cognitive Radio Network with Incorporation of MRC Scheme at Secondary Receiver

The faithful detection of presence of a primary user (PU) is the most essential requirement of a cognitive radio network. Otherwise the PU will experience jamming from a secondary user (SU) which will eventually lead to reduction in throughput of the PU. Similarly, the false detection of a PU will abstain a SU from its transmission opportunity hence reduce the throughput of the SU. Under this situation we propose a cognitive receiver equipped with multiple antenna and maximal ratio combining scheme (MRC) to detect the presence of a PU. The rest of the communication links like PU to PU or SU to PU uses single antenna. In this paper the concept of test statistics of fusion center from a previous literature is applied in the derivation of the probability of false alarm, probability of detection, channel capacity and symbol error rate of the network. The performance of a cognitive radio network under MRC scheme at receiving mode of SU is found better than the case of a single antenna.

Minimizing Sensing Decision Error in Cognitive Radio Networks using Evolutionary Algorithms

Cognitive radio (CR) is envisioned as a promising paradigm of exploiting intelligence for enhancing efficiency of underutilized spectrum bands. In CR, the main concern is to reliably sense the presence of primary users (PUs) to attain protection against harmful interference caused by potential spectrum access of secondary users (SUs). In this paper, evolutionary algorithms, namely, particle swarm optimization (PSO) and genetic algorithm (GA) are proposed to minimize the total sensing decision error at the common soft data fusion (SDF) centre of a structurally-centralized cognitive radio network (CRN). Using these techniques, evolutionary operations are invoked to optimize the weighting coefficients applied on the sensing measurement components received from multiple cooperative SUs. The proposed methods are compared with each other as well as with other conventional deterministic algorithms such as maximal ratio combining (MRC) and equal gain combining (EGC). Computer simulations confirm the superiority of the PSO-based scheme over the GA-based and other conventional MRC and EGC schemes in terms of detection performance. In addition, the PSO-based scheme also shows promising convergence performance as compared to the GA-based scheme. This makes PSO an adequate solution to meet real-time requirements.

Partial PIC-MRC Receiver Design for Single Carrier Block Transmission System over Multipath Fading Channels

Single carrier block transmission (SCBT) system has become one of the most popular modulation systems due to its low peak-to-average power ratio (PAPR), and it is gradually considered to be used for uplink wireless communication systems. In this paper, a low complexity partial parallel interference cancellation (PIC) with maximum ratio combining (MRC) technology is proposed to use for receiver to combat the intersymbol interference (ISI) problem over multipath fading channel. With the aid of MRC scheme, the proposed partial PIC technique can effectively perform the interference cancellation and acquire the benefit of time diversity gain. Finally, the proposed system can be extended to use for multiple antenna systems to provide excellent performance. Simulation results reveal that the proposed low complexity partial PIC-MRC SIMO system can provide robust performance and outperform the conventional PIC and the iterative frequency domain decision feedback equalizer (FD-DFE) systems over multipath fading channel environment.

Performance Analysis of Optimum and Suboptimum Selection Diversity Schemes on Rayleigh Fading Channels With Imperfect Channel Estimates

In this paper, we present a comparative analysis on the effects of channel estimation errors on the performance of optimum and suboptimum selection diversity (SD) receivers on Rayleigh-fading channels. By modeling the estimation errors as independent complex Gaussian random variables, we derive simple closed-form expressions for the average probability of error for both optimum and suboptimum SD schemes with noisy channel estimates. With dual diversity and imperfect estimates, we establish a connection between optimum SD and maximal-ratio combining (MRC), and between suboptimum SD and equal-gain combining diversity schemes. Interestingly, we show that the optimum SD receiver structure and the resulting performance for differential binary coherent phase-shift keying (DBPSK) signaling can be obtained, in a straightforward way, as a special case of the performance of the optimum SD scheme with binary PSK signaling and channel estimation errors. For a fixed average power and bit duration, in conjunction with pilot-assisted minimum mean-square error channel estimation, we show that the optimum coherent SD scheme coincides with that of the optimum noncoherent SD scheme with binary frequency-shift keying (BFSK) signaling, whereas the coherent MRC scheme coincides with the optimum noncoherent receiver (i.e., the square-law combiner) for BFSK. The optimum number of diversity channels, under an energy-sharing mode of operation, is also studied. Finally, we formulate the problem of optimal pilot placement, consider channel estimation with a practical pilot-symbol-assisted modulation technique, and present some numerical results illustrating the comparative performances of various SD receivers

Exploiting Diversity for Coverage Extension of Bluetooth-Based Mobile Services

This paper investigates the impact of diversity reception techniques on the performance of Bluetooth (BT) packet transmission in wireless channels with fast fading and shadowing to improve the coverage extension. We firstly derive a tight parametric exponential approximation for the instantaneous bit error probability (BEP) in additive white Gaussian noise with parameters dependent on GFSK modulation format according to the BT standard. Then, from this expression, we derive the mean block error probability (BLEP) for DH packets transmission in Rayleigh fading channel by adopting different diversity reception techniques, such as selection diversity (SD) and maximal ratio combining (MRC). In particular, the joint impact of the diversity order, the combining techniques and the block length on the BLEP, is shown. For both MRC and SD schemes, we also obtain a tight and invertible bound on the BLEP, that enables us to analytically evaluate the quality of service expressed in terms of outage probability in channel affected by fading and shadowing and, as a consequence, the impact of multiple antennas on the system coverage.

Performance analysis of linear diversity-combining schemes on Rayleigh fading channels with binary signaling and Gaussian weighting errors

In this paper, we analyze the error probability performance of maximal-ratio combining (MRC), equal-gain combining (EGC), selection combining (SC), and generalized-selection combining (GSC) diversity schemes with coherent binary phase-shift keying (BPSK) signaling on Rayleigh fading channels with Gaussian channel-estimation errors. We first show that, with weighting errors, averaging the conditional probability of error with the density function of the instantaneous signal-to-noise ratio (SNR) at the output of the combiner yields a lower bound on the exact probability of error. Later, we derive the exact probability of error for MRC, EGC, SC, and GSC diversity schemes and show that, for the case of nonnegative values of the in-phase correlation coefficient between the actual and the estimated channel gains, the exact probability of error with weighting errors is the same as that of the case with perfect channel estimation, but with the average SNR per diversity branch /spl gamma/~, for the case of perfect channel estimation, replaced by the effective SNR /spl gamma/~/sub /spl rho//, due to weighting errors. The effective SNR is a function of both /spl gamma/~ and /spl rho/, the magnitude of the normalized cross correlation between the actual and the estimated channel gains. Finally, we show that, as /spl rho//spl rarr/0, the average probability of error approaches 0.5, irrespective of the order of diversity and the diversity-combining rule.

Diversity with distributed decisions combining for direct-sequence CDMA in a shadowed Rician-fading land-mobile satellite channel

The performance of two diversity schemes with distributed decisions combining is analyzed and compared with that of the selection and maximal ratio-combining schemes for binary-phase shift keying (BPSK) direct-sequence code-division multiple access (DS-CDMA) in a shadowed Rician-fading land-mobile satellite channel. In the first scheme of distributed decisions combining, the combiner collects only the binary branch decisions to make the data decision. In the second scheme, the combiner makes the data decision using the branch decisions and the channel states. Both symmetrical and asymmetrical diversity branches are considered. Based on optimal likelihood ratio testing, a new data decision rule is devised for the detection of the spread-spectrum signals in the DS-CDMA system. Upper bounds are employed for the performance evaluation of the diversity combining schemes when the bit error probability is difficult to compute. Numerical results are presented for the satellite channel under light, average, and heavy shadowing.