Modern applications of wireless communications often fea- ture by high-rate transmission requirements. Therefore systems with high spectral efficiency characterisation incorporating multiple antennas at both transmit and receive side of the com- munication link, referred to as multiple-input multiple-output (MIMO) have recently received considerable attention , . The communication channel of these systems cannot be considered as frequency-flat channel and hence incurs inter- symbol-interference (ISI) along with co-channel-interference (CCI). Typical non-block based precoding/equalisation ap- proaches including mostly decision feedback equalisation , V-BLAST approaches  adopted for the broadband case or a mixture thereof , as well as Tomlinson-Harashima precoding (THP) , . These methods do not require a guard interval, can be globally optimised w.r.t. to e.g. mean squared error, and can therefore potentially achieve a higher spectral efficiency. The drawback of these schemes is the large effort in determining the optimum detection order in both space and time, often motivating the adoption of suboptimal approaches , .
The geometry and fabricated prototype of the proposed antenna are illustrated in Figure 1. The antenna includes two identical hybrid trapezoidal-elliptical monopoles that are printed perpendicular to each other and orthogonally fed by two 50 Ω CPW lines. The spacing between the two monopole is S = 4.3 mm. The orthogonal placement of the feeding structures accomplishes the dual polarization performance of the antenna. The antenna is printed on an FR4 substrate of a relative permittivity ε r = 4.4 and thickness h = 1.2 mm with total area of 25 × 53 mm 2 . In order to achieve compact size and broadband dual-polarized performance, the design parameters of the antenna are optimized by using Ansoft HFSS. The optimal geometrical parameters of the antenna are as follows: w = 25 mm, l = 53 mm, r 1 = 8.7 mm, r 2 = 6.53 mm, d = 0.5 mm, l p = 13.2 mm, w p = 24.5 mm, w g = 10 mm,
We have discussed a design of precoders and equalisers for broadband MIMO systems which are based on two separate steps. First, the CCI imposed by the MIMO transmission sys- tem is suppressed by means of a BSVD, similar to how a stan- dard SVD would be employed for a narrowband MIMO chan- nel. Second, SISO precoding and equalisation techniques are invoked in order to mitigate ISI within the subchannels.
The remainder of this paper is organized as follows. The system model for the massive MIMO system is described in Section 2. Different utility functions are analyzed under cor- related fading channels in Section 3, including mean square error of channel estimation (MSE-CE), mean square error of signal detection (MSE-SD), received signal-to-interferen- ce-plus-noise ratio (SINR), and spectrum efficiency (SE). In Section 4, the definition of the coalition game is given, and then the coalition structure, the adjustment principle of coalition structure, and the condition of final sta- bility are defined. After that, the coalition formation algorithm is given, a pilot allocation scheme based on the coalition game is proposed, and the implementa- tion method of the proposed scheme is discussed. In Section 5, simulations are developed with respect to different utility functions, and the proposed pilot allo- cation scheme is compared with the greedy approach in reference  and the random coalition scheme. Section 6 concludes this paper. The proof of theorem is given in the Appendices 1, 2, and 3.
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MIMO systems makes use of space-time block codes to allow the transmission of many number of copies of an information stream over a number of antennas and to utilize the multiple received data units to enhance the capability of data transfer. Space time coding helps to combat major problems like fading and thermal noise because of the use of number of copies of data .
As shown in Figs. 1(a)–(b), the proposed HP antenna element consists of four printed arc dipoles, four arc parasitical strips and four double L-shaped parasitical strips on the top side of the substrate and a broadband balun feeding network on the bottom side. The element is fed by a 50-Ω coaxial cable with an SMA connector from the center of the top plane. It is coupling fed by the balun feeding network. The feed point is given in Fig. 1(d). Four parasitical strips and four double L-shaped parasitical strips are applied to the top plane of the substrate to suppress the reactance of the antenna for bandwidth enhancement. The step increments of the balun are optimized for broadband impedance matching. When excited, the symmetric layout of the radiators will yield a synchronous clockwise or counter clockwise current ﬂow on the surface of the radiators, and it in turn generates omnidirectional radiation in azimuth plane. Fig. 2(a) depicts the return loss of the HP element with and without parasitical
precoding design with orthogonal or conventional AF schemes [12–14]. A transceiver precoding design is a pro- cessing technique that exploits channel state information (CSI) by weighting information streams at the transmitter to achieve transmit diversity. Mo and Chew  proposed two schemes of precoding design for AF MIMO relay net- works under minimum mean square error (MMSE) criter- ion and QoS requirements, i.e., optimal joint source and relay precoding (OJSRP) and suboptimal relay only pre- coding (SROP) schemes. They proved that the OJSRP scheme outperforms the SROP scheme in terms of MSE performance and capacity, which shows that precoding at both source and relay nodes achieves an improved (higher) performance compared to precoding only at the relay nodes. To optimize the power distribution between the source and relay nodes in the OJSRP scheme, a joint precoder design and node power allocation based on the MSE criterion in AF MIMO relay networks has been con- sidered . This approach demonstrated that the most efficient method to allocate node power is adjusting the noise level of the receiver nodes. A detailed investigation of the diverse linear precoder designs for AF MIMO relay networks based on MMSE, zero-forcing (ZF), and max- imum information rate (MIR) criteria can be found in the literature . In that study, the results showed that the MMSE criterion achieves near-optimal performance
From (5), it can be found that once a MIMO antenna is designed, there are two possible DNs that correspond to the designed antenna: a positive B implies a capacitor and a negative B indicates an inductor. Because a positive B corresponds to a positive θ, which means a shorter length of T- lines, a capacitor is preferred in the conventional DN . However, the conventional DN suffers from the narrow-band limitation because the transadmittance (and coupling coefficient) of the MIMO system cannot be removed effectively when the length of the T-line is too short. In order to overcome this narrow-band characteristic, it is necessary to consider a resonance type of antenna system and variations of the imaginary part of the transadmittance, or trans-susceptance (Im[Y 21 ]). The MIMO antenna section at the reference plane a is assumed to be well matched at desired center frequency at each port. After adding T-lines (Z 0 , θ) at each port, the transadmittance (or transimpedance) of the
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Figure 8 show the BPSK BER performance for the various systems developed in this paper. The systems are the same as those in Figure 7, but the simulations are now performed only over a “realistic” SNR range of 0 dB to 30 dB. We see that for the 100 MHz-sampled SV channel the performances are all quite similar. Only the FDO curves are worse as the point where a fixed regularisation factor outperforms the noise power value occurs at about 30 dB. The performance of the 1 GHz-sampled SV channel is the best due to the much longer equaliser filters.
In this paper, two broadband microstrip antennas using coplanar line feeding have been successfully implemented. Results show that, with the present proposed coplanar line feeding, the microstrip bandwidth can be significantly enhanced. This broadband design method is applicable to the microstrip antennas with square patch and circular polarization design.
The contribution of this work is that we develop a new BD precoding for downlink MU-MIMO system with multiple data streams per user to improve the BER performance without complex power, modulation, or coding. As detailed in the paper, the proposed algorithm is based on the multiple users and multiple streams MIMO systems which will be finally used for the deriv- ation of the analytical system performance. A more thor- ough evaluation of proposed algorithm is confirmed via simulations. Furthermore, the new algorithm demon- strates a superiority performance.
Abstract. In this paper, an overview of carrier frequency off- set (CFO) estimation algorithms for Orthogonal Frequency Division Multiplexing (OFDM) systems is presented. It is well-known that multicarrier systems suffer from their high sensitivity to mismatches of transmitter and receiver oscilla- tor frequencies. The performance degrades since the CFO destroys the orthogonality of the subcarriers. Hence, exten- sive research has been done on the estimation and correc- tion of the CFO in Single-Input Single-Output (SISO) sys- tems. Mainly, the proposed algorithms can be categorized into data-aided and blind techniques. Several estimation techniques have been extended to the Single-Input Multiple- Output (SIMO) case where multiple receive antennas can be utilized to gain diversity. However, less attention has been paid on synchronization in the attractive Multiple-Input Multiple-Output (MIMO) case which is topic of tremendous interest in current research. The present paper concentrates on aspects of this new scenario. Starting with algorithms for SISO and SIMO, this contribution reviews briefly proposed carrier frequency synchronization techniques which could be implemented in forthcoming MIMO systems.
The length of the channel is truncated to 5 since the im- pulse response samples beyond the 5th are statistically very small. So in the following simulations, the signals are trans- mitted over a length-5 frequency-selective MIMO channel. Since optimal precoders are applicable only to fixed or slowly time-varying channels, we consider these two types of chan- nels in our simulation. For the case of a fixed channel, the channel is assumed to be quasistationary, that is, it is station- ary during the transmission of one block but changes inde- pendently from one block to another. This simulation pro- cedure ensures that the results presented do not depend on one specific (good or bad) channel, but instead sample ex- haustively the space of all possible channels. The simulation results shown below represent an average over 1000 random channels and the length of each block is 1000 symbols. The channel noise is simulated by adding independent complex circular white Gaussian noise sequences which zero-mean and variance σ 2
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Data have been collected under controlled pedestrian traffic conditions. Four different scenarios were considered: vacant, one, two and three person walking along the indicated trajectories. Additionally, as the performance of MIMO- OFDM system can dramatically change due to a small shift of the antenna array , two data sets have been collected for each scenario by placing the Rx antenna array in two different locations 4 λ (approximately 25 cm) apart. Wide band relative power was collected for the 4x4 antenna-to-antenna channels.
A performance comparison of the IA receiver with a standard (interference unaware) receiver for TM5 is given in Figure 2. For comparison, we also consider fallback trans- mit diversity (TM2) and closed-loop SU-MIMO schemes (TM6). We consider ideal OFDM system (no intersymbol interference (ISI)) and analyze the system in the frequency domain where the channel has iid complex Gaussian matrix entries with unit variance and is independently generated for each channel use. We assume no power control in MU- MIMO mode, so two UEs have equal power distribution. It is assumed that the UE knows its own channel from the eNB, so in MU-MIMO mode, UE can find the eﬀective channel of interference based on the fact that the eNB schedules second UE on the same RE which has requested 180 ◦ out-of-phase precoder. Note that the MCS for a particular user is the same in each set of simulations. So where one UE is served with a particular MCS in TM6 or TM2, two UEs are served with the same MCS in MU-MIMO (TM5) mode thereby doubling the sum spectral e ﬃ ciency.
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One of the prominent wireless technologies is Mobile networking, which can yield voice and/or data network connectivity through wireless. Most famous application of mobile networking is cellular phone . In mobile as well as fixed, demand for radio transmission throughput will always increase. One can definitely predict that, in coming decades, millions of users in a large city will want to transmit and receive holographic video more or less continuously, about 100 Mbps per consumer in each direction. Hyper- MIMO often called Massive MIMO is a promising technology for meeting this demand.
Wireless networking has become common needs in the last few years. With prices reduced to a fraction of what they were, it is no wonder that wireless networking products have transitioned from the home, office and currently used in manufacturing. A wireless network provides freedom in convenience and lifestyle to exchange words, data and music or video with any computer across the internet, or around the world. One of the major problems of future mobile communications system is the rapid increase in the demand for different broadband services and applications .
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The previous sections have shown that MIMO systems with distributed antennas and unequal average link SNRs behave in a very similar way as MIMO systems with colocated an- tennas and spatially correlated links (with regard to various performance measures). In other words, both eﬀects entail very similar performance degradations. For example, spatial fading correlations (unequal average link SNRs) can lead to significantly reduced ergodic or outage capacities . With regard to space-time coding, the presence of receive antenna correlations (distributed receive antennas) always degrades the resulting PEP, particularly for high SNRs. As opposed to this, the impact of transmit antenna correlations (dis- tributed transmit antennas) depends on the employed space- time code and the SNR regime under consideration . Concerning the average SEP of OSTBCs, correlated anten- nas (unequal average link SNRs) always entail a performance loss [31, Chapter 3.2.5].
Developments in the ICT industry have had a considerable effect on healthcare sectors, and have conceived and shaped the eHealth phenome- non. Of the many ICT developments influencing and affecting health- care sectors, recent advances in the areas of telecommunication and net- working in particular have given rise to innovative tools and technologies, that have made possible a wide range of efficient and powerful health- care/medical applications that were previously not possible. For instance, accessing patient records logged in a mobile digital form, performing robot- ically assisted surgeries remotely, phone and online consultations, medical paging systems, and remote cardiac monitoring .
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perform Perfect Tracking for Multiple-Input Multiple-Output (MIMO) systems. Perfect Tracking is the task of very closely following a reference signal or trajectory by a system in the absence of modelling error or external noise. The architecture in this paper is based on the Dual Feedforward Method which has previously been applied for Single-Input Single-Output systems. Extension and generalization of the method to MIMO systems is non-trivial and our main contribution lies in designing the two feedforward paths through Right Matrix Fraction Description (RMFD) which enables perfect tracking of continuous-time MIMO systems. The paper presents the proposed architecture, the design methodology and illustrative simulation results. The architecture is also successfully implemented on the classic virtual Quadruple Tank laboratory apparatus.