Peter Akuon

Polar coded spatial modulation

A scheme is proposed, called polar coded spatial modulation (PCSM), to provide both detection/decoding of the transmitted symbol and the transmit antenna index in multiple-input-multiple-output (MIMO) antenna systems. Based on the free polar set and the frozen polar set in polar codes, the proposed PCSM scheme maps the transmitted information data in the free polar set and the transmit antenna index bits in the frozen polar set whose positions are known at the receiver. This has the advantage that the bits that identify the transmit antenna are not transmitted to the receiver and do not need to be detected as is the case in conventional spatial modulation (SM). Thus, PCSM presents a spectrally efficient and a power-efficient system. For the simulations, MIMO channels with transmission over independent and identically distributed flat fading characteristics are exploited. Firstly, capacity results for coded SM which is a requirement for the construction of the codes are presented. Consequently, the bit error rate performances of the M-ary quadrature amplitude modulation SM are analysed for various MIMO architectures after which the desirable MIMO architecture is proposed for the PCSM. In addition, the upper and lower bounds on probability of frame error for the transmitted symbol information, under successive cancellation decoding are derived and the PCSM scheme suits the bounds for the suiting architecture.

Path reduction factor modeling for terrestrial links based on rain cell growth

A new path length reduction factor that accounts for the growth and occurrence of multiple rain cells along a propagation path of a given terrestrial link is introduced in this work. In addition, the mathematical and empirical derivations that were used to come up with this new factor are outlined. This model is investigated by comparing it to other well-known models by utilizing attenuation statistics from a 19.5 GHz terrestrial link experiment carried out in Durban, South Africa. The predicted and measured attenuation values are then compared for the three models. Evaluation of the three models is then carried out by calculating their attenuation percentage error values. It is seen that the proposed model performs well over the ITU-R model in the terrestrial link thus validating it as a good model for rain attenuation predictions in the Southern Africa region.

Optimal error analysis of receive diversity schemes on arbitrarily correlated Rayleigh fading channels

A simple optimal error analysis of multiple-branch equal gain combining (EGC) and selection combining (SC) in the presence of arbitrarily correlated Rayleigh fading channels is presented. It is shown that the error rates over correlated branches for diversity combining schemes can be analysed at the output of an eigenfilter splitter, which is placed at the output of the diversity combiner. Since the outputs of the splitter are uncorrelated, the error analysis of maximal ratio combining (MRC) technique is applied to EGC and SC. This analysis is possible since error performance of MRC with correlated branches is optimal and invariant to eigenfilter or eigenvector decorrelation and the decorrelated outputs can simply be analysed similar to independent branches. The authors exploit extensive simulations for average bit error probability, which show tight bounds with the proposed analytical approach. Channel correlations for different practical antenna spacing of 0.15, 0.2 and 0.5 of the signal carrier wavelength, λ are analysed.

Optimal bit error analysis of N r -branch EGC under Rayleigh fading channels

To date, several analyses of diversity systems involve very complex mathematical derivations. These complex methods achieve precise analytical results, but some lack insightful engineering representations which can be used to implement the systems directly. Concerned for equal-gain combiner (EGC), a simple closed-form error analysis of Nr-branch EGC system in the presence of Rayleigh fading is presented. The average output signal-to-noise ratio (SNR) of the EGC combiner is split into equal Nr power splitter output SNRs. Since the average output SNR of the splitter equals the sum of the outputs, EGC system reduces to maximal ratio combiner (MRC) whose properties are well known. By devising SNR coefficient for EGC, optimal bit error rate (BER) is derived using the properties of the MRC. Besides an approach of splitter design is illuminated.

Polar coded MQAM with no noise variance estimation for capacity and soft decision metric

Polar coding (PC) separates the codeword into free and frozen sets of channels. In this paper, the construction of the two sets of channels and decoding are carried out based on the channel capacity and soft decision metric, respectively with unity noise variance. Additionally, the capacity for which signal and noise power are equal results in an interesting capacity spectrum whose average value is used in the PC construction. Simulations results show that this simplified soft metric achieves the same bit error rate (BER) when compared to the exact metric with receive overhead advantage. Transmission of symbols is made via flat fading Rayleigh channels. We see that the simulations results are well bounded within the theoretical performance limits.

Gain of spatial diversity with conjoint signals

This paper proposes a novel method of achieving conjoint coding gain without additional signal measurement requirements. In the proposed scheme, received signals in a spatial diversity system are used to synthesize additional conjoint signals within the neighbourhood of receive antennas. These excess signals are assumed to be from virtual antennas. In an Nr branch system and in order to retain the diversity order, a total of N2r output signals are obtained, where Nr (Nr − 1) is the number of conjoint signals or virtual antennas. When combined, a coding gain of at least 1 [dB] is achieved. It is shown that the bit error rate (BER) of selection combining (SC) with conjoint signals results in coding gains over that of the conventional SC. Also, equal gain combiner (EGC) results in BER that is equal to that of the maximal ratio combiner (MRC). The coding gains are achieved through a dual transformation that does not require the measurement of signal information. As a result, the EGC can be used to obtain BER results similar to the computationally complex MRC scheme. The proposed system is tested under flat Rayleigh fading channels.

Performance of multiple active-spatial modulation: information theoretic criteria over correlated Rayleigh fading channels

In this study, symbol error probability of transmitted modulation signals for a single-input–multiple-output system is used to derive overall average bit error probability (ABEP) of multiple active-spatial modulation (MA-SM) system as a function of the number density of bits in error. Specifically, a theoretic method of determining the number density of bits in error in the joint detector of MA-SM is proposed. Sample variance (SV) criterion uses the sample covariance of detector noise data, while mutual information (MI) criterion uses relative entropy derived from the Kullback–Liebler distance to compute the number density of bits in error. The choice for the better criterion is formulated as a model selection problem between the SV and the MI criteria. Analytical results for ABEP are tightly verified from simulations, which are carried out under arbitrarily correlated flat Rayleigh fading channels. Various data rates, antenna spacing and number of transmit and receive antenna configurations are tested, where it is also shown that SM is a special case of MA-SM. Moreover, a basis spectral efficiency (BSE) formula for MA-SM systems is proposed, which can be used to select a preferred antenna configuration without the need for simulations.