IV. NUMERICAL SYSTEM PERFORMANCE RESULTS In this section we will characterise the MAT performance of the multiple transmit/receiveantenna aided DS-CDMA code acquisition scheme of Fig.1. In Table 1 and 2 we outlined the maximum SINR degradation imposed by both the Doppler shift and the frequency mismatch between the transmitter and receiver in conjunction with the coherent integration interval of N chip durations seen in Fig.1 for both initial and post-initial acquisition. The length of the PN sequence in our system was assumed to be (2 15 − 1) · T c , where the chip- duration is T c = 1/1.2288µs . In the case of the initial acquisition scheme of Fig.1, it was found to be sufficient to integrate the detector output seen in Fig.1 over N =128 chips for the sake of analysing SDSS, while the number of chips over which the accumulator Σ of Fig.1 sums the (·) 2 envelope detector’s output in both the search and the verification modes of DDSS are assumed to be 32 and 256 in the R = 1 and 2 receive antennas scenarios or 128 in the R = 4 receiveantenna senario, respectively. By contrast, in the case of the post-initial acquisition scheme, the optimised length of coherent summation of the detector output values invoked for the sake of analysing SDSS is given in Table 3, whilst 64 is selected as the length of coherent summation in the search mode of DDSS. Finally, the optimised intervals of the coherent summation used in the verification mode of DDSS are portrayed in Table 4. In both Table 3 and 4, the numbers seen in (·) can be used as an altenative. These optimised parameter values were calculated by using both Eq (1) and Eq (12)
Employing both multiple transmit antennas and subcarriers in the downlink of wireless systems exhibits an attractive technique of reducing the detrimental effects of time-variant multi-path fading environments -. In recent years diverse combinations of Single- Carrier (SC) CDMA and OFDM  have attracted research efforts -. In inter-cell synchronous CDMA systems the mobile station’s receiver must be capable of synchronising the timing of a locally gen- erated PseudoNoise (PN) spreading sequence with that of the desired user’s PN sequence contaminated by the interfering signals. The code acquisition performance of MC DS-CDMA attained with the aid of serial search based schemes has been investigated in ,. In order to characterise the effects of multiple transmit/receive antennas in terms of the achievable MAT performance, the results of  outlined the characteristics of a serial search based code acquisition scheme in the context of the multiple transmitantenna aided SC-DS-CDMA downlink. However, since there is a paucity of in-depth results on the fundamental characteristics of code acquisition schemes designed for a multiple transmit/receiveantenna assisted MC- DS-CDMA system in the context of Differentially Coherent (DC) code acquisition schemes, solving this open problem is the main objective of the present paper. Similarly to Non-Coherent (NC) code acquisition schemes ,, no prior information concerning the absolute carrier phase is necessary for the operation of DC code acquisition schemes . An additional benefit of using a DC code acquisition scheme is that it is capable of attaining a better performance than its NC counterpart -. Here we adopted the Full-Period Correlation (FPC) based scheme of  in order to analyse the characteristics of serial search based DC code acquisition in the multiple transmit/receiveantenna assisted MC-DS-CDMA downlink. Against this backdrop, in this treatise we examine both serial search based DC and NC code acquisition schemes designed for multiple transmit/receiveantenna assisted MC-DS-CDMA systems. More explicitly, we characterise the MAT versus E c /I 0 performance parameterised by both the number of transmit/receive antennas and that of the subcarriers.
experimentally designed for the initial code acquisition scheme. Fig.3 characterises the MAT versus SINR per chip performance of DDSS for the initial code acquisition arrangement of the SC-DS- CDMA benchmark system as a function of the number of transmit antennas for P = 1, 2 as well as 4 and that of the number of receive antennas for the speciﬁc values of R = 1, 2 and 4. As the number of transmit antennas is decreased, all the curves seen in Fig.3 illustrate an improved MAT peformance of the systems exploiting R = 2 and 4 receive antennas, except for the R = 1 scenarios over the speciﬁc SINR range shown in Fig.3. To illustrate the above fact a little further, in the cases of both P 2R1 and P 4R1 the DDSS scheme exhibits a better MAT peformance in comparison to the P 1R1 arrangement across the speciﬁc SINR range considered. In other words, this clearly implies that the DDSS scheme employing R = 1 receiveantenna beneﬁts from a higher diversity gain in the SC- DS-CDMA scenario. However, the peformance degradation imposed by employing multiple antennas becomes more drastic in the low SINR range, as the number of transmit antennas is increased in the DDSS-aided initial code acquisition scenario. In case of employing both multiple transmit and multiple receive antennas, similar trends are observable, although using two or four receive antennas has the potential of mitigating the associated acquisition performance degradation imposed by the low per-branch E c /I o values associated with the employment of multiple transmitters.
3, the solid lines indicate a single-path scenario (denoted as M 1 in Figs.2 and 3), whereas the dotted lines represent the scenario of receiving three paths (denoted as M 3 in Fig.2). It is worth mentioning that although not explicitly shown in Figs.2 and 3 for avoiding obfuscating details, the operating range of R =2 receive antennas was found to be between that corresponding to the R =1 and R =4 receiveantenna scenarios. As the number of transmit antennas was decreased, all the curves seen in Fig.2 illustrated an improved MAT peformance for the systems exploiting R =4 receive antennas in both the single-path and multi-path scenarios. Similar trends were observed also in the R =1 receiveantenna aided multi- path scenario, except for R =1 in the specific E c /I 0 range of
In ,, explicit MAT formulae were provided for a single- antenna aided serial search based code acquisition system. There is no difference between a single-antenna aided scheme and a multiple- antenna assisted one in terms of analysing the MAT, except for deriving the correct detection and the false alarm probability based upon the multiple transmit/receive antennas. We will commence our discourse by comparing the MAT performance of differential FPC based code acquisition to that of the corresponding noncoherent one using Single Dwell Serial Search (SDSS) , because the correlation operation of the FPC scheme is performed over a full code period . We assume that in each chip duration T c , l number of correct
The relevant information-theoretical analysis predicts  that substantial capacity gains are achievable in wireless commu- nication systems employing a Multiple Input Multiple Output (MIMO) architecture using multiple antennas. Specifically, provided that the fading processes corresponding to different transmit-receiveantenna pairs may be assumed to be indepen- dently Rayleigh distributed, the associated attainable capacity was shown to linearly increase with the smaller of the numbers of the transmit and receive antennas. Additionally, the employ- ment of a MIMO architecture allows for the efficient exploita- tion of the spatial diversity available in a wireless MIMO en- vironment, thus an improvement of the system’s transmission integrity, as well as a further increase in the system’s capacity becomes possible.
The BRP refines the sectors found in the SLS phase. These sectors are determined using inhomogeneous quasi-omni- directional antenna patterns and may have sub-optimal signal quality. Further, the BRP foresees optimization of antenna weight vectors, independent of the pre-defined sector patterns, for phased antenna arrays. This can yield additional throughput gains, while increasing the beam training search space. Even though free variation of the antenna weight vectors can result in arbitrary antenna patterns, the directional nature remains for antenna configurations that yield high throughput. Thus, the training process for pre-defined directional sectors and antenna weight vectors optimization remains the same. Finally, the BRP is used to train receiveantenna configurations in case this was not part of the preceding SLS. Multiple optional pattern refinement mechanisms are defined for the BRP and are out of scope of this paper. We focus on the mandatory beam refinement transactions, an iterative process in which both initiator and responder can request training for receive or transmitantenna patterns.
In telecommunication, Free Space Optics [FSO] provides an optical communication technology which uses light energy to transmit the information from one point to another point. This technology is very useful where it is difficult to incorporate the optical fiber due to structure of the surface or due to maintenance. Like fiber, FSO uses lasers to transmit data, but through the open air instead of using closed fiber cable. FSO is capable of sending up to 1.25 Gbps of data, voice, and video communications simultaneously through the air . Short Range line of sight optical links have the potential for providing high bandwidth access to larger wired network as well as they can be used to link intranets within the corporate campuses. FSO is attractive compared to RF due to several reasons. First, optical beams are very directive with beam width on the order of 10mrads so spatial isolation from other potential interferes is maintained. Secondly, there is no license is required for optical bandwidth. Third, it provides high level of security with data speed of upto 1.25 Gbps. Fourth its maintenance is low and can be installed behind the windows, so roof top is required . Systems using Multiple Transmit and Multiple receiveAntenna are known as Multiple Input and Multiple Output (MIMO) System. This wireless technique has greatly improved the capacity and range of wireless communication channel. MIMO systems constructively explores multipath propagation by using different transmission path to the receiver, which provides redundancy of data thus increases the reliability of transmission. This technique is also useful for increasing the transmitted data rate. MIMO system has attracted users significantly because it offers high speedreliable data range at the same power and bandwidth . MIMO system can also be used for FSO system. As MIMO uses multiple transmit and receiveantenna so at the transmitter several laser diode are used (as laser diodes convert electrical information into optical data stream) for transmitting the data and at the receiver several photo diodes are used to collect the transmitted information.
signals add destructively at the receiver due to an 180 ◦ phase diﬀerence. This method achieves about 40 dB of isolation, however it brings several limitations: (i) the receiveantenna should receive the 180 ◦ out of phase signal only at the center frequency, (ii) the conﬁguration of using multiple antennas is not feasible for handheld devices where space is limited,and (iii) use of multiple antennas creates nulls in the far ﬁeld and degrades radiation pattern. To overcome the above shortcomings, a single antenna is used to transmit and receive simultaneously by incorporating a circulator combined with analog cancellation tools based on a balun, variable attenuators, and delay lines [11, 12]. A circulator can achieve approximately 20 dB of added isolation in this manner, with the loss of an increase in device cost and size. In , using commercially available hardware, a self-interference suppression level of 46 dB is experimentally demonstrated in a highly reﬂective indoor environment implementing a combination of directional isolation, absorptive shielding, and cross-polarization. However, the antenna separation is not less than 35 cm, thus rendering the device too large to be useful in many applications.
Abstract—In this paper, we consider the problem of bistatic multiple- input multiple-output (MIMO) radar systems design for parameters estimation. Maximum channel capacity is used as criterion for the problem of optimal systems design under transmitted power constraint and channel constraint. We obtain that the system design based on maximum channel capacity can be expressed as a joint optimization problem. Given the number of transmitantenna, the number of receiveantenna and signal-noise ratio (SNR), the maximum channel capacity can be determined. This maximum channel capacity can be obtained from a unique appropriate power allocation and antenna placement strategy, which is very important for system design.
Consider a mobile communication system where the base station is equipped with n transmit and the remote unit is equipped with m receive antennas (see Figure 1). At each time slots t, signals are transmitted simultaneously through n transmit antennas. The channel is flat-fading and the path gain from transmitantenna i to receiveantenna j is denoted by hi,j. The path gains are modeled as samples of independent complex Gaussian random variables with variance 0.5 per real dimension, i.e. h i,j ∼ N (0,1),
Since the advent of STTCs and OSTBCs in 1998, various other families of space-time codes have been proposed in the literature. Similar to OSTBCs, square-matrix embeddable STBCs allow for ML detection at the receiver by means of (generalized) linear processing. A family of non- orthogonal full-rate linear STBCs, called diagonal algebraic STBCs, was constructed. Diagonal algebraic STBCs provide full transmit diversity and allow for efficient ML detection by means of the sphere decoding approach. Another non-orthogonal full-rate STBC for two transmit antennas, constructed based on number theory, For more than one receiveantenna, this STBC provides an improved coding gain compared to Alamouti’s transmit diversity scheme ., STBCs based on linear constellation precoding were proposed, which provide full rate and full diversity for any number of transmit antennas and perform superior to OSTBCs, a sphere decoding approach as well as suboptimal alternatives were used for decoding. Here the strict constraint of perfect orthogonality was relaxed in favor of a higher data rate. The resulting STBCs are therefore referred to as quasi-orthogonal STBCs. Due to the relaxed orthogonality constraint, however, quasi-orthogonal STBCs typically offer reduced diversity gains compared to OSTBCs. In particular, the parallel concatenation of two identical recursive STTCs was studied. Here the encoder structure was inspired by the original turbo code proposed by Berrou, Glavieux, and Thitimajshima in 1993.16 .Recursive STTCs are also well suited for a serial concatenation with an outer channel code (with iterative detection at the receiver).
DESIGN OF 2X2 (Tx-Rx) SCFDE SYSTEM USING STBC AND RECEIVER DIVERSITY Design of single carrier frequency domain equalization system using space time block codes and receiver diversity for 2 transmitantenna and 2 receiveantenna is as follows. The block diagram of transmitter of 2x2 (Tx-Rx) SCFDE system is shown in figure , the symbol notification of SCFDE system is given in Figure, the block diagram of 2x2 (Tx-Rx) SCFDE system is shown in figure , and the block diagram of receiver of 2x2 (Tx-Rx) SCFDE system is shown in figure .
system is designed for a maximum target range of 150 kilometers from the transmitter and 175 kilometers from the receiver, a range resolution of 7.5m, the overall detection rate is 90% and the False alarm rate ( FAR) = 1e-6. The radar operating frequency is 10 gigahertz. The design focuses on implementation of angle estimation and the effects of antenna placement on angle estimation performance. Most literatures on bistatic MIMO radar systems assume equal transmit and receiveantenna elements with half wavelength inter element spacing for both arrays. An antenna placement scheme for varying the number of transmit and receiveantenna for good angle estimation performance is proposed. Matlab simulations were performed to evaluate the performance of the proposed method.
As a result of the utilization of multiple antennas, MIMO wireless technology is ready to significantly increase the capacity of the given channel. By increasing the amount of transmit and receiveantenna it is possible to linearly increase the output of the channel with each pair of antennas added to the system. This makes MIMO wireless technology one amongst the foremost necessary wireless techniques used in recent years. As spectral bandwidth is changing into an ever a lot of valuable commodity for radio communication system, techniques are required to use the out there bandwidth a lot of effectively. MIMO wireless technology is one amongst those techniques. 2.2. MIMO
In an omni to omni link, the constant gain antennas on both sides of the link result in the received power rolling off as 1/f 2 in band. A constant aperture receiveantenna whose gain varies as f 2 cancels out this 1/f 2 roll-off and yields a flat received power in band. This received power may be significantly greater than that of a comparable omni antenna depending upon the magnitude of the receiveantenna gain. This advantage is offset by a narrowing of the pattern and field-of-view that accompanies the increasing gain of a typical directional antenna. Using a directional antenna whose gain varies as f 2 on the transmit side of the link does not improve matters further, because the transmit power must be made to roll-off as 1/f 2 to meet the same flat EIRP spectral mask. Figure 8 depicts this behavior.
In higher modulations MIMO systems provide a number of advantages over single antenna- to-single-antenna communication. Sensitivity to fading is reduced by the spatial diversity provided by multiple spatial paths. Under certain environmental conditions, the power requirements associated with high spectral-efficiency communication can be significantly reduced by avoiding the compressive region of the information-theoretic capacity bound. Here, spectral efficiency is defined as the total number of information bits per second per Hertz transmitted from one array to the other. After an introductory section, the next section describes the concept of MIMO information-theoretic capacity bounds, the phenomenology of the channel with reference to its capacity associated with parameterization techniques, Capacity. Channel estimation is done by two techniques namely data aided and non data aided.
Abstract—An active-antenna array with 18 transmit elements and 18 receive elements is designed and fabricated. This T/R array can work at two diﬀerent frequencies (19.5 GHz and 21.5 GHz) with multiple levels of isolation between the transmit and receive channels. A hybrid element-level vector ﬁnite element and adaptive multilevel fast multipole method (ELVFEM/AMLFMA) is applied to simulation the performance parameters of the array element and the full array fast. To obtained the maximum directivity of the array,the best distances of the T/R elements in the array are optimized by using the genetic algorithm (GE) combining with VFEM/AMLFMA. The design eﬃciency of the array is improved at a ratio of 30%. Finally the performance of the T/R array fabricated is measured in experiments and some good results are obtained.
The simulation process of MANET is implemented using simulator Qualnet 5.0.2. Performance metrics used in this paper are Throughput, Average jitter, Energy consumed in transmit and receive mode and percentage of time in transmit and receive mode.CBR (Constant bit rate) application is used for in the scenarios. The no: of nodes used in the scenarios are 10,20,30,40 and 50. At last result is achieved for different scenarios and the three routing protocols are compared.