Space Shift Keying Modulation Research Articles

Performance Comparison of IRS-Assisted SSK Modulation Over Rayleigh and Nakagami-m Fading Channels

To meet the needs of society, the next generation of communication systems will have to learn to juggle multiple responsibilities effectively. This is leading to exponential growth in both circuit complexity and error rates. It is possible to solve these issues by using the intelligent reflecting surface (IRS)-Assisted space shift keying (SSK) modulation technique. IRS is a cutting-edge technology that shows promise for future networks due to its low mistake rates and low-energy consumption. Similarly, SSK modulation is favored due to its preference for simpler hardware. Therefore, integrating IRS with SSK is preferable for minimizing both error rates and circuit complexity. In this article, a new framework is developed to characterize the average bit error rate (ABER) with the help of the moment generating function (MGF) over Nakagami-m fading channels. The ABER is derived by factoring the direct path and IRS reflected path at the receiver and also comparing the performance analysis over the Rayleigh fading channel. The analytical results are validated through Monte-Carlo simulations.

Performance Evaluation of SSK Modulation Over Shadowed-Rician Land Mobile Satellite Links

We investigate the performance of satellite communication systems acquiring the space shift keying (SSK) modulation technique over shadowed-rician (SR) land mobile satellite (LMS) link. Specifically, we discuss the analytical performance of the considered system over independent and identically distributed SR fading channels in terms of symbol error rate (SER), diversity order, and average capacity. The SER of the considered set-up is derived by utilizing moment generating function (MGF) expression over the SR fading LMS communication links. The analytical diversity order of the scheme is derived by using SER expression. We consider the effect of elevation angles on the SER performance, diversity order, and channel capacity of the considered SSK-assisted satellite communication system. As observed from simulation and analytical results, the performance of the considered set-up can be raised by improving elevation angles. Further, a closed-form expression of the average capacity of the SSK assisted satellite communication system is also derived. It is shown through simulation and analysis that the fading conditions and elevation angle does not affect the diversity order of the system, but it adversely acts on the SER performance and average capacity of the system.

HP-DF SSK Method for UAVs Communication in Cooperative Multi-Hop Rician Networks

This paper presents techniques that are expected to improve the bit error rate (BER) performance of Unmanned Aerial Vehicles (UAVs) communication systems. The decode-and-forward (DF)-based cooperative multi-hop Rician network using space shift keying (SSK) modulation is employed for this purpose. The SSK modulation and cooperative communication are merged and used together. This enhances the BER performance for multiple-input multiple-output (MIMO) channels, thus accentuating its significance as an important technique for consistently reliable communication methodology while, at the same time, eliminating wastage of energy. The new technique is named as high performance (HP) due to not only BER performance improvement but also increase of the diversity of the communication system. This new model is further used for multi-hop networks and the resulting BER characteristics are assessed for possible enhanced performance in Rician channels. The paper also showcases the generalized-n-hop BER equation for various multi-hop DF-based cooperative communication systems in diverse UAV models. The Monte Carlo simulations further confirm the theoretical results that already exist for transmit-receive antennas. This work also underlines the fact that the number of hops in a communication system has no bearing whatsoever on the BER performance diversity value.

Analysis of SWIPT based dual-hop AF relay with SSK modulation over Nakagami-m fading channel

Space shift keying (SSK) modulation performance is analyzed with simultaneous wireless information and power transfer (SWIPT) based cooperative amplify-and-forward (AF) relaying system over the Nakagami-m fading channel. SWIPT technique can remove the need for power supply at the relays in cooperative communication. In contrast, SSK is a low complex index modulation technique that eliminates inter antenna synchronization, inter-channel interference and reduces the number of radiofrequency chains. Closed-form expression for average bit error probability (ABEP) is derived using a single AF relay with selection combining (SC) at the receiver, and an Upper bound ABEP expression is derived for multiple AF relays with the direct link (DL) from source to destination. The partial relay selection (PRS) technique has been proposed with energy harvesting (EH) to reduce the hardware complexity compared to the multiple relays. Numerical and computer simulation results are presented with the discussion. The result demonstrates that EH with SSK modulation can improve the system performance.

Performance analysis of SSK modulation for UAVs communication

In this paper, we investigate the performance of Space Shift Keying (SSK) modulation on a Multiple-Input-Multiple-Output (MIMO) wireless communication system for Unmanned Aerial Vehicles (UAVs) over Rician fading channels. SSK modulation can be a key technique for energy-efficient and reliable communication scenarios for UAV applications. The first part of the performance analysis consists of theoretical derivations for the Bit Error Rate (BER) performance of UAVs' SSK communication. The second part consists of theoretical derivations for the outage probability. Error rate performance comparison between SSK modulation for UAV communication systems and conventional systems is given. Then, the proposed system's diversity order is derived and presented as a number of receive antenna Nr. The BER performance decrease against non-line-of-sight channel scenarios is shown via simulation results due to the line-of-sight effect on the SSK modulated system. Monte Carlo simulations validate theoretical derivation results for various transmit - receive antennas and Rician K factor values.

Secrecy Analysis of SSK Modulation: Adaptive Antenna Mapping and Performance Results

In this paper, we investigate the physical layer security based on space shift keying (SSK) in which bit-to-spatial mapping of antenna indices dynamically adapts according to the partial channel state information (CSI) of the legitimate channel at the transmitter (Tx). Further, the Tx also adapts transmit power allocation to each transmit antenna according to partial CSI. Since an eavesdropper (Eve) is not (usually) aware of the legitimate CSI, it cannot successfully decode the antenna index; thus, transmission over the legitimate channel is secured from the wiretapping of Eve. An important virtue of the proposed scheme is that the Tx does not require full CSI of the legitimate and eavesdropper channels to secure the confidential information. The proposed work focuses on the secrecy rate (SR) and bit error rate (BER) of the considered multiple-input single-output system over Rayleigh fading channels. Approximate expressions of Bob's data rate for 2-ary and 4-ary SSK modulations are derived in closed-form. Furthermore, an upper-bound of Bob's data rate for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> -ary SSK modulation is also derived. In order to obtain the secrecy rate for the proposed scheme, we also evaluate Eve's data rate. Analytical results of SR and BER demonstrate the robustness of the proposed scheme. All numerical results are thoroughly verified by using extensive Monte Carlo simulations.

Full Euclidean Distance Based Selection Combining for SSK DF Cooperative Diversity Systems

Space Shift Keying (SSK) is a multiple-input multiple-output technique that has drawn more attention in recent years because of its low complex transceiver design. In this paper, an investigation on the Symbol Error Probability (SEP) performance of SSK in a Decode-and-Forward (DF) cooperative relaying system is done. The DF cooperative relaying scenario considers an origin node, an intermediate node and an end node with a direct link between origin and end node, and an indirect link between origin to the intermediate node and intermediate to end node. The SSK modulation is considered at the origin and intermediate nodes with Full Euclidean Distance based Selection Combining (FED-SC) employed at the end node for SSK symbol detection. The SEP expression of the SSK FED-SC in the DF cooperative relaying scheme is derived using the Order Statistics Approach (OSA). Further, a closed-form SEP expression is obtained using a Combined Order Statistics Approach (COSA) considering the number of receive antennas at the intermediate node is equal to the number of receive antennas at the end node. In addition, the closed-form asymptotic SEP expression is presented to evaluate the diversity order of the system. The SEP expressions derived through OSA and COSA are verified using the Monte Carlo simulations. The simulation results revealed that the proposed SSK FED-SC outperforms all the existing SSK DF cooperative selection combining schemes.

SSK modulated WPCN with Euclidean distance based selection combining receiver

In this paper, the performance of space shift keying (SSK) modulation in a wireless-powered communication network (WPCN) is analysed with selection combining based on generalized Euclidean distance at the receiver. The network considered here is with multiple number of transmitting antennas and multiple number of receiving antennas operates under Rayleigh fading. Based on the Euclidean distance between the SSK modulation constellation points, this scheme selects any number of antennas out of $$N_a$$ receiving antennas. Selecting one or $$N_r$$ ( $$N_r<N_a$$ ) number of receiving antennas with energy harvesting, the system performance will improve and the receiver complexity as well as the number of radio frequency (RF) chains can be reduced. A closed form expression for the average bit error probability (ABEP) is derived for two transmitting antennas and $$N_a$$ receiving antennas with WPCN using SSK modulation. The numerical results and simulation results are presented to illustrate the energy harvesting on system performance.

Feedback-Based SSK Modulation: Constellation Design and Performance Results

In this article, we propose a limited feedback-based space-shift keying (SSK) modulation scheme where transmitter (Tx) obtains partial channel state information (CSI) via a feedback link from receiver (Rx). More specifically, the Tx does not receive perfect information of channel gain, but is aware only of channel gain ordering. Based on the received partial CSI, the Tx adapts the spatial constellation and allocates different transmit weights to each transmit antenna representing spatial constellation points. Furthermore, the power adapted spatial constellation points are encoded by using gray coding scheme, which results in unit hamming distance between adjacent spatial constellation points. Next, a multiple-input single-output (MISO) system with maximum–likelihood detection is investigated. Accurate expressions for the average bit error rate (ABER) for ${2}\times {1}$ and ${4}\times {1}$ MISO systems over Rayleigh fading channel are derived. Further, an approximate expression for the ABER of a generalized MISO system is also obtained. It is shown analytically that the ABER performance of the proposed SSK scheme can be improved by applying a non-uniform power allocation to make transmit links more distinguishable at the Rx. Moreover, we demonstrate analytically that the proposed scheme attains a diversity order which is twice of the conventional SSK scheme. Numerical results, corroborated by Monte Carlo simulations, verify the proposed analysis and clearly highlight that, the proposed scheme significantly outperforms existing closed-loop spatial constellation-based schemes relying on full CSI in Tx and conventional open-loop SSK scheme.

Use of Nakagami-m Fading Channel in SSK Modulation and Its Performance Analysis

In recent years, multiple-input-multiple-output communication has a great demand due to its flexibility and well technical implementation. Though it has been approached by many researchers, in this paper, authors taken an approach with Nakagami-m fading channel as it is a generalized fading channel for the performance of space shift keying (SSK) modulation. Simple closed form expression for the probability of bit error of SSK modulation is presented using probability density function based method for independent and identically distributed (IID) Nakagami-m fading channel. An upper bound expression for IID and correlated Nakagami-m fading channel is also presented. Obtained probability of error are in the form of Gauss hypergeometric function, confluent hypergeometric function and Gamma function which can be numerically evaluated and verified by Monte Carlo simulation.

SSK-Based SWIPT With AF Relay

The performance of space shift keying (SSK) modulation using energy harvesting amplify and forward (AF) relaying is analyzed over the Rayleigh fading channel. Simultaneous wireless information and power transfer technique eliminates the need of power supply at the relay in cooperative communication. However, energy tapped from an information signal for harvesting would degrade receiver performance. At the same time, the distance between the relay and the receiver can be increased due to the power splitting-based relay with the SSK modulation. New closed-form expressions for average bit error probability (ABEP) is derived with a single AF relay and an upper bound expression for multiple relays with a direct link. Furthermore, the ABEP is analyzed for a partial relay selection operation. The numerical and computer simulation results are presented with the discussion.

SSK modulation performance with relay selection and selection combining

In this letter, the performance of space shift keying (SSK) modulation is analyzed with partial amplify and forward (AF) relay selection (RS) from multiple numbers of relays and selection combining (SC) at the receiver. This scheme selects a single radio frequency (RF) chain from the transmitter to the relay using the RS as well as relay to the receiver using the SC technique. Closed‐form expression for average bit error probability (ABEP) is derived and Numerical and computer simulation results are presented with the discussion. The result derived is compared with the best RS where the best link between the transmitter to the receiver is selected with SC at the receiver. It is revealed that there is an interesting trade‐off between partial RS and best RS with SC at the receiver. However, it is shown that partial RS with SC has almost equal ABEP performance in comparison to best RS with SC with low hardware complexity.

Impact of symmetric and asymmetric fading channels on dual-hop AF relay system with SSK modulation

Performance of dual-hop amplify-and-forward relaying system is analyzed over asymmetrical Nakagami-m/Rcian and symmetrical Nakagami-m/Nakagami-m fading channel with space shift keying (SSK) modulation. Expressions for average bit error probability (ABEP) of SSK modulation scheme over the line-of-sight and non-line of sight fading channels have been obtained. Analytical expressions for cumulative distribution function of the end-to-end signal-to-noise ratio are derived and a mathematical expression for the ABEP of SSK modulation is obtained for both in presence of the direct link between source to destination and in absence of the direct link. The derived expressions are given in terms of the Whittaker functions and Gamma functions. ABEP expressions are also derived which provide useful insights into the factors governing the performance of the considered system. The numerical results have been verified with Monte-Carlo simulation results.

Space shift keying for multi-hop multi-branch networks

In this paper, we propose two different multi-hop multiple-input multiple-output (MIMO) space shift keying (SSK) schemes and investigate their error performance. In the first scheme, we consider a multi-hop multi-branch SSK system, in which the source and destination are equipped with multiple transmit and receive antennas, respectively. In this scheme, SSK is applied by using the source transmit antennas. Moreover, in each branch, single-antenna relays are used to amplify the transmitted signal from the source and forward it to the next relay until it reaches to the destination. In the second scheme, we consider a multi-hop MIMO-SSK system with path selection. In this scheme, the best path is selected among multiple branches and a multiple-antenna source communicates with a multiple-antenna destination via the relays of the selected path. Each relay is equipped with multiple transmit and receive antennas. Moreover, the source and all relays employ SSK modulation to transmit information bits and each relay in each path follows the decode-and-forward protocol. Approximate theoretical error probability expressions are derived for both schemes. Furthermore, an asymptotic symbol error probability performance analysis is also performed for the multi-hop MIMO-SSK system with path selection. It is shown that the proposed multi-hop SSK systems outperform conventional multi-hop M-PSK systems in terms of the error performance for especially high data rates and sufficient number of receive antennas at the receiving nodes.

A reliable relay selection scheme for SSK modulation in cooperative communication systems

Space shift keying (SSK) modulation is a scheme in which the indices of active transmit antennas play an essential role in carrying information bits. In SSK modulation, the communication channel acts as modulating unit. Therefore, using the conventional relay selection schemes based on channel coefficients are impossible in cooperative systems using SSK modulation. In this paper, we propose a novel relay selection scheme that is applicable in cooperative systems using SSK modulation. The proposed scheme is based on calculating and measuring the Euclidean distances between received signal and all active or inactive channel coefficients. The proposed relay selection scheme is applied for a cooperative communication system with multiple relay nodes and a direct link between source and destination. The analytical expressions are derived to calculate the average bit error rate over Rayleigh fading channels. The analytical and simulation results show that this relay selection scheme can provide a full cooperative diversity order, for SSK modulation. In addition, we show that this scheme can be used at destination as a signal selection method, to select the best received signal from different paths. The analytical results are validated using Monte Carlo simulation studies.

Complex Hadamard Matrix-Aided Generalized Space Shift Keying Modulation

In this paper, we present a complex Hadamard matrix-aided generalized space shift keying (HSSK) modulation scheme, which introduces complex-Hadamard-based signal vectors at the transmitter to provide higher spectrum efficiency than generalized space shift keying (GSSK). It also has lower maximum-likelihood detection complexity than the multiple active spatial modulation (MA-SM) and generalized spatial modulation (GSM) systems due to the corresponding fast complex Hadamard transform at the receiver. Based on the Lee distance of our signal vectors, we provide an optimized mapping between our data bits and signal vectors. We also analyze the upper bound on the average bit error rate of our HSSK system, which agrees well with the simulation results. Finally, the performance of HSSK is compared with MA-SM, GSM, and GSSK systems through Monte Carlo simulations. It is shown that for the same transmission rate the HSSK system performs better than the GSM, MA-SM, and GSSK systems.

Characterization of IDF and SDF Relaying Protocols in SSK Modulation Systems

In this paper, the performance of space shift keying (SSK) modulation is investigated in a cooperative communication system, using incremental decode-and-forward (IDF) and selective decode-and-forward (SDF) relays. The IDF and SDF relays use instantaneous signal-to-noise ratio (SNR) to verify the quality of received signal, which is not applicable to SSK modulation. In addition to instantaneous SNR, channel coefficients play the main role in the performance of SSK modulation. Moreover, in this modulation scheme, the active channel coefficient is unknown. In this paper, instead of instantaneous SNR, a new reliable criterion is introduced to be used in the IDF or SDF protocols for SSK modulation. This criterion is based on the Euclidean distances between active channel coefficient and other inactive channel coefficients. The analytical expressions are derived to calculate the average bit error rate (ABER) and the power consumptions in a cooperative system, over Rayleigh fading channels, for both IDF and SDF relaying protocols. There is good agreement between the Monte Carlo simulated and analytical results. These results show that this Euclidean distance-based criterion, in IDF or SDF relaying protocols, improves cooperative diversity gain and the ABER performance significantly.

Performance Analysis of Coded SSK Modulation on Block-Fading Channels

In this paper, we analyze the performance of convolutionally coded space-shift keying (SSK) modulation on block-fading channels. We derive the transfer function bound for the conditional error performance of coded SSK modulation. Existing works on SSK error performance focus mostly either on uncoded systems or on coded systems with independent fading between successive symbols. Code performance analysis is complicated by the fact that SSK modulation does not yield a uniform symbol, i.e., the error probability of a bit in a symbol is not independent of the position of the bit in the label. Furthermore, there are no nearest neighbors in the SSK constellation. The code and modulation must be jointly analyzed. We show techniques that can be employed to derive the error transfer function of the convolutional code. The degrees of separation in SSK modulation are accurately represented. The diversity order achieved by the system can be predicted. We also show a technique that can simplify analysis of the coded system. We present simulation results that demonstrate the asymptotic accuracy of the derived transfer function bound.

Layered Space Shift Keying Modulation over MIMO Channels

Space shift keying (SSK) modulation is an emerging transmission technique for multiple-input multiple-output (MIMO) wireless channels, which exploits the spatial domain to convey information. In this paper, we present a layered space shift keying (LSSK) modulation scheme to fully exploit the spatial domain to transmit information bits, where a layered architecture is developed to achieve spatial multiplexing transmission in an SSK system. Specifically, LSSK leverages the rotated signals predetermined at the transceiver to identify different layers and improve the bit-error-rate (BER) performance. The layered signals are directly generated by the proposed LSSK modulation method with a low computational overhead. Furthermore, we propose a layered-and-joint (LJ) near-optimal detection algorithm based on the layered architecture of LSSK to reduce the detection complexity. In LJ detection, layered detection is performed to find a set of detection candidates for each layer, and then, joint detection is performed with these candidates. We show that the performance of LJ detection is quite close to that of optimal maximum-likelihood detection with significantly reduced detection complexity for high-spectrum-efficiency scenarios. Results demonstrate that the proposed LSSK scheme substantially improves the spectrum efficiency of an SSK system and outperforms other existing MIMO schemes.

Performance Analysis of Physical Layer Network Coded Bidirectional Relay Networks using Space Shift Keying Modulation for Los Communication at Millimetre Wave Frequencies

Space-shift keying (SSK) modulation is a novel multiple-input–multiple-output (MIMO) technique, which activates only a single antenna for transmission at any time instant and uses the index of this active antenna to implicitly convey information. In this paper, SSK modulation for physical layer network coding (PLNC) based two-way or bi-directional decode and forward relay network is proposed. It is assumed that a bidirectional relay network consists of two sources and a relay and operates in a half duplex mode. Specifically, the transceiver sends the data by employing SSK modulation and detects the signal based on the maximum likelihood (ML) detection criterion both at sources and relay. The error performance of the physical layer network coding (PLNC) protocol in bidirectional relay networks for SSK is analyzed in line-of-sight space shift keying (LOS-SSK) conditions. By considering LoS environment, the pair-wise error probability (PEP) is derived at the relay in closed form. The tight upper and lower bounds in closed form for the end-to-end average pairwise error probability (PER) are also obtained.