Single Antenna Transmission Research Articles

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.

Single-RF Spatial Modulation Requires Single-Carrier Transmission: Frequency-Domain Turbo Equalization for Dispersive Channels

In this paper, we propose a broadband single-carrier (SC) spatial modulation (SM)-based multiple-input–multiple-output (MIMO) architecture relying on a soft decision (SoD) frequency-domain equalization (FDE) receiver. We demonstrate that conventional orthogonal-frequency-division-multiplexing (OFDM)-based broadband transmissions are not readily suitable for the single-radio-frequency-assisted SM-MIMO schemes since this scheme exhibits no substantial performance advantage over single-antenna transmissions. To circumvent this limitation, a low-complexity SoD FDE algorithm based on the minimum mean square error (MMSE) criterion is invoked for our broadband SC-based SM-MIMO scheme, which is capable of operating in a strongly dispersive channel having a long channel impulse response at moderate decoding complexity. Furthermore, our SoD FDE attains a near-capacity performance with the aid of a three-stage concatenated SC-based SM architecture.

Performance Analysis of Successive Decoding Based on Shadowing Side Information Under Non-Identical Composite Fading/Shadowing Channels

The performance of a distributed multiple input-multiple output (MIMO) system with $m$ single-antenna transmitters and a receiver with $n\ge m$ antennas is analytically investigated. Particularly, the transmitters simultaneously send their information streams to the receiver, operating under the spatial multiplexing regime. To this end, the receiver utilizes the zero forcing detection followed by the ordered successive interference cancellation technique. Composite fading/shadowed channels between receiver and transmitters are assumed, which are modeled as non-identical $\mathcal{K}$ faded channels (i.e., Rayleigh multipath fading and Gamma distributed shadowing). The receiver sequentially detects and decodes the streams, starting from the strongest to the weakest, whereas symbol ordering is implemented with regards to shadowing side information without taking into account the fast varying multipath fading fluctuations. New closed-form expressions regarding the outage probability and the average symbol error probability are derived in terms of finite sums of the Meijer's- $\boldsymbol{G}$ functions. Further, simplified expressions in terms of elementary functions are obtained in some specific asymptotic cases of interest, namely, in high signal-to-noise regions and when the receiver is equipped with very large antenna arrays (i.e., massive MIMO systems). Moreover, useful engineering insights are manifested, such as the diversity order of the considered system.

Performance Analysis of Cooperative Wireless Networks With Unreliable Backhaul Links

A cooperative wireless network, where a cluster of $K$ single-antenna transmitters jointly serve a single-antenna receiver, is considered. Each transmitter is connected to the control unit (CU) via independent but unreliable backhaul links. The CU sends a common message to each transmitter over backhaul links, which upon successful reception, jointly transmit this message to the intended receiver. To facilitate analysis, a general expression is derived for the complementary cumulative distribution function of a sum of $K$ independent random variables, where each random variable is a product of an exponential and a Bernoulli random variable. This result is applied to find a simple closed-form expression that characterizes the system outage performance as a function of network parameters and node geometry. The analytical model is validated using numerical simulations. As an application, the derived expression is also used for investigating the impact of backhaul assignment on the system performance.

Towards the Next Generation Video Broadcasting: Improved Performance Using Distributed MIMO

Distributed multiple-input multiple-output (MIMO) is a promising technique for the future terrestrial TV broadcasting systems due to its higher efficiency over the traditional single-antenna transmission scheme. In this article, we investigate the application of distributed MIMO technique in the future broadcasting systems. We first show the advantage of the distributed MIMO from the channel capacity perspective. Then different space-time block codes (STBCs) that can be applied in the distributed MIMO broadcasting scenarios are discussed and compared with real system configurations and channel conditions. It is shown that the simple and sophisticated STBCs have mutually complementary application scenarios. Particularly, short 3D MIMO code is a good performance versus decoding complexity compromise among different application scenarios.

A Comparative Analysis of Adaptive Digital Predistortion Algorithms for Multiple Antenna Transmitters

This paper presents a comparative study of adaptive algorithms for digital predistortion (DPD) in multiple antenna transmitters. Crossover predistorter (CO-DPD) and crosstalk canceling predistorter (CTC-DPD) were proposed to overcome the deleterious effect of RF crosstalk before the power amplifiers (PA) on digital predistortion (DPD) in multiple antenna transmitters. This paper discusses the linearization performance and computational complexity of least mean square (LMS) and recursive least squares (RLS) adaptive algorithms for CO-DPD and CTC-DPD. The adaptive predistortion algorithms for a single antenna transmitter can be extended for CO-DPD, by incorporating the DPD coefficients of more than one branch in to one filter coefficient vector of the adaptive algorithm. The adaptive CTC-DPD involves predistorters for each transmitter running in parallel with the adaptive algorithms that track the coupling between the transmitters. The computational complexity of CTC-DPD is considerably lower compared to CO-DPD, as it has lesser predistorter branches. It is estimated that the number of computations needed per sample duration, for the real-time operation of the adaptive CTC-DPD is 47% lesser compared to CO-DPD for a two-antenna transmitter, when a 9th order memory polynomial with 3 memory taps was used. The linearization performances of these adaptive predistortion techniques for two and four antenna transmitters are evaluated through simulations using QPSK, 16-QAM, UMTS, and LTE signals. It is observed that CTC-DPD performs approximately identical to CO-DPD in all the examined cases. In the presence of frequency selective crosstalk, an extension of CTC-DPD which can pre-cancel such crosstalk, performs considerably better than CO-DPD, which cannot model the frequency selectivity of the crosstalk.

An Improved DMRS Design Scheme of LTE-Advanced Uplink

The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink supports only a single antenna transmission. However, in order to improve the uplink spectrum efficiency, support multiple antenna transmission in LTE-Advanced. Meanwhile, taking into account backwards compatibility for LTE. LTE-Advanced De-Modulation Reference Signal (DMRS) needs to be designed [1]. According to requirement of LTEAdvanced uplink pilot design, introducing orthogonal cover code (OCC) as a supplement, analysis and study of the current problems, proposes a Circular Shift (CS), Group/Sequence Hopping (GSH) and the OCC joint instructions method of pilot design. Finally, simulation and analysis of the performance of this scheme. Results show that this scheme can meet LTE- Advanced demand for pilot design well.

Non-Vanishing Space Time Block Code for Three Time Slots and Two Transmit Antennas

Recently, space time block codes (STBCs) are proposed for multi-input and multi-output (MIMO) antenna systems. Designing an STBC with both low decoding complexity and non-vanishing property for the Long Term Evolution Advanced (LTE-A) remains an open issue. In this paper, first our previously proposed STBC’s non-vanishing property will be completely described. The proposed STBC scheme has some interesting properties: 1) the scheme can achieve full rate and full diversity; 2) its maximum likelihood (ML) decoding requires a joint detection of three real symbols; 3) the minimum determinant values (MDVs) do not vanish by increasing signal constellation sizes; 4) compatible with the single antenna transmission mode. The sentence has been dropped. Second, in order to improve BER performance, we propose a variant of proposed STBC. This scheme further decreases the detection complexity with a rate reduction of 33%; moreover, non-vanishing MDVs property is preserved. The simulation results show the second proposed STBC has better BER performance compared with other schemes.

Anti-Collision Technique of SAW Tags Using Walsh Code

—In view of the inefficiency of coding, the complexity of signal extraction and the strict demands of machining in the existing multiple SAW tags system, an anti-collision technique based on Walsh Code was proposed. First, it encodes the 2PSK using the single antenna transmission structure, then it implements the orthogonal encoding of each tag in a multiple SAW tags system using Walsh coding, and finally the encoding information of each tag is acquired by reading the echo signals from the reader and doing cross-correlation operation with each code block in the orthogonal code-set. The proposed approach incorporates both the coding efficiency and the processing technology, simplifies the complexity of signal extraction, and achieves the goal of anti-collision of multiple SAW tags system. The theoretical analysis and simulation verify the feasibility of this technique.

Transmit Diversity in the Downlink for the TETRA-TEDS System

In the paper a proposal for the improvement of performance for the TETRA Enhanced Data System (TEDS) employing transmit diversity based on two antennas in the downlink is described. The key idea of the considerations relies on using the space-frequency coding algorithm. The proposal described required some relatively simple changes to the existing TEDS’s Single Input Single Output (SISO) interface but the original number of payload and signaling symbols in the normal downlink burst is preserved. The simulation results obtained indicate a significant improvement in performance. The Eb/No parameter could be reduced from 5 to 8 dB with respect to Frame Error Rate (FER), compared to a single antenna transmission for the same FER = 10−3.

Use of SSK Modulation in Two-Way Amplify-and-Forward Relaying

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, a pragmatic communication strategy for the use of SSK modulation in two-way amplify-and-forward (AF) relaying is proposed. Specifically, the transceiver sends the signal by employing SSK modulation and detects the signal based on the maximal-ratio combining principle. By considering a Nakagami- m fading environment, upper bounded and asymptotic bit error probabilities (BEPs) are both derived in closed form. The optimal power allocation problem in the minimization of the average BEP is also addressed. Finally, Monte Carlo simulations are conducted to verify the accuracy of the analysis.

Physical Layer Security of Maximal Ratio Combining in Two-Wave With Diffuse Power Fading Channels

This paper advocates physical layer security of maximal ratio combining (MRC) in wiretap two-wave with diffuse power fading channels. In such a wiretap channel, we consider that confidential messages transmitted from a single antenna transmitter to an M-antenna receiver are overheard by an N-antenna eavesdropper. The receiver adopts MRC to maximize the probability of secure transmission, whereas the eavesdropper adopts MRC to maximize the probability of successful eavesdropping. We derive the secrecy performance for two practical scenarios: 1) the eavesdropper's channel state information (CSI) is available at the transmitter and 2) the eavesdropper's CSI is not available at the transmitter. For the first scenario, we develop a new analytical framework to characterize the average secrecy capacity as the principal security performance metric. Specifically, we derive new closed-form expressions for the exact and asymptotic average secrecy capacity. Based on these, we determine the high signal-to-noise ratio power offset to explicitly quantify the impacts of the main channel and the eavesdropper's channel on the average secrecy capacity. For the second scenario, the secrecy outage probability is the primary security performance metric. Here, we derive new closed-form expressions for the exact and asymptotic secrecy outage probability. We also derive the probability of nonzero secrecy capacity. The asymptotic secrecy outage probability explicitly indicates that the positive impact of M is reflected in the secrecy diversity order and the negative impact of N is reflected in the secrecy array gain. Motivated by this, we examine the performance gap between N and N+1 antennas based on their respective secrecy array gains.

Differential Spatial Modulation

Spatial modulation (SM) is a newly emerging multiple-input–multiple-output technique that activates only a single antenna for transmission at any time instant and uses the index of the active antenna as an additional information-carrying mechanism. However, by its nature, SM decoding is coherent in that channel state information (CSI) is required at the receiver. In fact, coherent SM decoding can be very complex due to the heavily entangled channel estimation and symbol detection. In this correspondence, a differential SM scheme that completely bypasses any CSI at the transmitter or receiver, while preserving the single active transmit antenna property, is developed. The proposed scheme can be applied to any constant energy constellation such as phase-shift keying (PSK) and to systems with arbitrary numbers of transmit and receive antennas. Simulation results are presented under various system configurations. With the same spectral efficiency, the proposed scheme is capable of paying no more than 3 dB of signal-to-noise ratio penalty compared with coherent SM and outperforming the single-antenna differential PSK and differential space–time coding schemes.

Averaging time required for measuring the specific absorption rate of a MIMO transmitter

This paper presents a new method to measure electric field (E-field) for human-body exposure to electromagnetic fields from Multi-Input Multi-Output (MIMO) wireless communication transmitters, and an estimation of averaging time required in the E-field measurement. The proposed method is to measure time-averaged E-field, and the averaging time is the duration required for a measurement system to make averaged E-field converged. The estimation is based on averaging the square of amplitude of received signals or measured E-field strength. Several simulation results with different measurement parameters for MIMO wireless communication transmitters are presented and discussed. It is pointed out that the averaging time in E-field measurements for multi-antenna transmitters is considerably longer than that for single antenna transmitters.

Joint User Grouping and Linear Virtual Beamforming: Complexity, Algorithms and Approximation Bounds

In a wireless system with a large number of distributed nodes, the quality of communication can be greatly improved by pooling the nodes to perform joint transmission/reception. In this paper, we consider the problem of optimally selecting a subset of nodes from potentially a large number of candidates to form a virtual multi-antenna system, while at the same time designing their joint linear transmission strategies. We focus on two specific application scenarios: 1) multiple single antenna transmitters cooperatively transmit to a receiver; 2) a single transmitter transmits to a receiver with the help of a number of cooperative relays. We formulate the joint node selection and beamforming problems as cardinality constrained optimization problems with both discrete variables (used for selecting cooperative nodes) and continuous variables (used for designing beamformers). For each application scenario, we first characterize the computational complexity of the joint optimization problem, and then propose novel semi-definite relaxation (SDR) techniques to obtain approximate solutions. We show that the new SDR algorithms have a guaranteed approximation performance in terms of the gap to global optimality, regardless of channel realizations. The effectiveness of the proposed algorithms is demonstrated via numerical experiments.

A Phase Adjustment Approach for Interference Reduction in OFDM-Based Cognitive Radios

The problem of cross-band interference in single-antenna and multi-antenna OFDM cognitive transmitters is considered. Cross-band interference, which is caused by large OFDM signal sidelobes, is a major drawback of OFDM, especially in cognitive radio applications where it is crucial to protect primary licensed users from the secondary user's interference. In this paper, we propose a novel low complexity technique, referred to as a phase adjustment technique, to tackle this problem in single-antenna and multi-antenna OFDM cognitive transmitters. In this technique, the phase of each OFDM symbol is adjusted in an attempt to minimize the interference caused by the secondary user to the primary. Unlike prior methods, this technique does not decrease data throughput and has no impact on the bit-error-rate and peak-to-average power ratio of the OFDM symbols. Furthermore, to calculate the adjustment phases, three heuristics, one of which is very low complexity and achieves near optimal performance in numerical simulations, are also proposed. In addition, the performance of the proposed technique is evaluated analytically in some special cases in single and multi-antenna cognitive transmitters, and is verified by numerical simulations.

A Novel Space Time Block Code Scheme for Three Time Slots and Two Transmit Antennas

Mobile station (MS) in the Long Term Evolution Advanced (LTE-A) equips with two transmit antennas and the data are transmitted during three time slots. This has brought up an interesting space time block code (STBC) design for LTE-A. In this paper, a novel STBC scheme is proposed for three time slots and two antennas. The proposed STBC scheme has these properties: i) the scheme can achieve full rate and full diversity, ii) its maximum likelihood (ML) decoding requires a joint detection of three real symbols, iii) the minimum determinant values (MDVs) do not vanish by increasing signal constellation sizes, iv) compatible with the single antenna transmission mode. Simulation results show that the proposed scheme has the same bit error rate (BER) performance with the best known scheme at high signal to noise ratio (SNR).

Error Performance of Multidimensional Lattice Constellations—Part I: A Parallelotope Geometry Based Approach for the AWGN Channel

Multidimensional lattice constellations which present signal space diversity (SSD) have been extensively studied for single-antenna transmission over fading channels, with focus on their optimal design for achieving high diversity gain. In this two-part series of papers we present a novel combinatorial geometrical approach based on parallelotope geometry, for the performance evaluation of multidimensional finite lattice constellations with arbitrary structure, dimension and rank. In Part I, we present an analytical expression for the exact symbol error probability (SEP) of multidimensional signal sets, and two novel closed-form bounds, named Multiple Sphere Lower Bound (MLSB) and Multiple Sphere Upper Bound (MSUB). Part II extends the analysis to the transmission over fading channels, where multidimensional signal sets are commonly used to combat fading degradation. Numerical and simulation results show that the proposed geometrical approach leads to bounds that can be used for the performance evaluation and the design of multidimensional lattice constellations, both in Additive White Gaussian Noise (AWGN) and fading channels.

Enhancing Security in Correlated Channel With Maximal Ratio Combining Diversity

In this correspondence, we consider a confidential communication through slow non-selective correlated Rayleigh fading channel, where a single antenna transmitter communicates at a pre-decided constant rate with a legitimate receiver in the presence of an eavesdropper. Both the legitimate receiver and eavesdropper are equipped with multiple antennas and employ maximal ratio combining (MRC) reception scheme. With the presence of channel diversity, we find the closed-form expressions for the probability of non-zero secrecy capacity and the outage probability of secrecy capacity in terms of channel parameters such as correlation coefficient and the ratio of main and eavesdropper channel gains that will be called average channel gain ratio (CGR). The analysis of secure outage performance with the MRC diversity scheme tells how the channel diversity enhances the secrecy capacity. We quantify the effect of antenna correlation on the probability of positive secrecy capacity and the secure outage probability. We also investigate how the target secrecy rate influences the effect of antenna correlation on the secure outage probability. Moreover, as a result of obtaining the closed-form expressions for the probability of positive secrecy capacity and the outage probability, it is insightful to see how the channel parameters affect the secure outage performance of the correlated channels.

Multihop Hybrid Virtual MIMO Scheme for Wireless Sensor Networks

Wireless sensor network devices commonly use a single antenna for transmission and reception, as well as for relaying packets over multiple hops to a final destination, which is referred to as single-input-single-output (SISO) multihop transmission. Advancements in multiple antenna systems enable reliable broadband wireless communications using multiple-input-multiple-output (MIMO) transmission technology. In addition, through collaboration of several single-antenna-equipped devices, cooperative MIMO communication is possible in the form of virtual MIMO (V-MIMO), virtual multiple-input-single-output (V-MISO), and virtual single-input-multiple-output (V-SIMO), which are collectively called V-MIMO technology. In this paper, a multihop hybrid V-MIMO (HV-MIMO) networking scheme is proposed to configure a minimum energy consuming route (MECR) that provides high end-to-end connectivity while satisfying end-to-end data rate and bit error rate (BER) requirements by using the best cooperative MIMO configuration for each hop. In the proposed scheme, first, the source-to-destination path is divided into long wireless communication hops, and the minimum energy consuming V-MIMO configuration is applied to each hop. Next, the long communication hops are individually evaluated for replacement with two half-length V-MIMO hops, where changes are applied only when a gain in energy consumption is obtainable. If no gain is obtainable for a certain hop, then the hop configuration is not changed, and that hop is no longer compared for replacement. This procedure of testing for possible replacement with two half-length hops is repeated individually for all hops until no further changes are made in the source-to-destination path, which is when the HV-MIMO MECR is complete. For equivalent end-to-end data rate and BER requirements, the proposed HV-MIMO multihop scheme provides a significant energy saving (e.g., 52.32% energy saving at the node density of 0.003 nodes/m2) compared with the conventional SISO multihop path's MECR. In addition, the HV-MIMO scheme always results in an energy saving gain and a significantly higher end-to-end multihop MECR connection probability compared with using the same type of cooperative MIMO configuration for each hop (i.e., homogeneous V-MIMO configuration).