Improvement Of Ber In Wlan Using Mimo-Ofdm

Abstract

The Multiple Input Multiple Output and Orthogonal Frequency Division Multiplexing technology is used for developing various wireless communications. The combination of MIMO-OFDM gives improvement in Bit Error Rate, capacity and reliability. To achieve high throughput, MIMO with greater form of modulation is used. The MIMO-OFDM technology in wireless helps to use maximum bandwidth with less cost. Space time block coding along with MIMO gives improvement in Bit Error Rate. The performances of the various systems are evaluated by comparing the BER and SNR. Keywords: MIMO, OFDM, BER, BPSK, QPSK, QAM,1.

Introduction

Recently, the mobile communication systems are experiencing a dramatic increase with even data rates more than 1gbps. A difficult task in wireless atmosphere is to develop a decisive communication design. Various techniques are implementing to enhance the performance of MIMO system. MIMO systems are the most promising technology for the future generations. MIMO enables us to enhance capacity of the link and band width adaptability. The technique here we used is Space Time Block Coding which gives maximum data rate and diversity gain. OFDM is a well-known method to transmit the high data in wireless medium. Now the high rate wireless communications get attracted and research are being undertaken to challenge the context of the WLAN and in other multimedia networks.

These wireless systems are very popular which helps in communication OFDM changes over wideband channel into parallel level sub channels. OFDM is well-known because of its bandwidth adaptability. OFDM is the multicarrier technique and was considered as the future generative networks. OFDM is now emerged as popular block modulation technique. OFDM combined with MIMO helps in making the wireless communication better. The combination of MIMO and OFDM is considered as the most powerful technique. The MIMO - OFDM technology has been a great fame and a boon for the coming generation’s wireless networks and boost the performance of wireless communication systems. The MIMO-OFDM system performance is evaluated with the help of MIMO channel measurement data. The MIMO performance was compared to the other detection systems through computer simulations. The performance of MIMO-OFDM was analysed by the BER versus SNR. By this ISI was reduced and has high reliability and better performance, high data rate is achieved. Here MIMO-OFDM technique is used to enhance the performance by having multiple transmit and receive antennas for the Rayleigh channel.

Bit Error Rate

In wireless communication, the information is transmitted in digital stream of 0’s and 1’s. During transmission, data can’t be received properly. Bit error rate is a parameter which can be used to analyse the performance of communication system. BER is the ordinary rate in which bit error occurs during communication process. BER is defined as ratio of number of error bits to number of transmitted bits. The bit error chance is the estimated value of BER in any of wireless communication system, where there is a chance to occur error in communication system due to inclusion of noise. The BER can be redesigned by choosing a flag of more quality, by choosing a moderate and vigorous and legitimate tweak plan or line coding plan, and by applying channel coding plans, for example, excess forward correction codes.

Mimo Technology

MIMO means Multiple Input Multiple Output. This means MIMO technology uses numerous antennas at both transmitter side and as well as receiver side. By using numerous antennas at both transmitter and receiver side improves the system work capacity as related to single antenna systems. The use of Multiple Input Multiple Output (MIMO) frameworks has expanded because of its strength against Multipath blurring, increment in the Spatial Multiplexing Gain and Spatial Diversity Gain. The signal model of the MIMO is represented in a matrix form is given as:

r = H. s + n

The multiple signals are broadcasted together from the multiple antennas through the channel and the receiver receives the signals that are transmitted. By using multiple antennas we can achieve higher data transmission rates, diversity gain, spatial multiplexing gain, more extensive scope and higher dependability without utilizing extra recurrence range. A dependable execution is gotten by differences which can be accomplished in MIMO frameworks.

Space Time Block Coding

STBC is a strategy to accomplish high assorted qualities execution which all the while transmits similar information over various reception apparatuses at various circumstances. In STBC method numerous duplicates of same information are transmitted over number of radio wires and to abuse the different got forms of information to enhance unwavering quality of information exchange. The beneficiary joins every one of the duplicates of got flag in an ideal approach to extricate as much data from each of them.

The Received vectors areY1 = h1(X1) + h2(X2) + n1 Y2 = h1(-X*2) + h2(X1*) + n2 STBC is generally defined by a matrix

Ofdm Technique

OFDM means Orthogonal Frequency Division Multiplexing. It is a multicarrier adjustment strategy in which input information is isolated into various parallel sub streams and transmitted over the individual subcarriers which are orthogonal to each other. Henceforth, the recurrence particular wideband channel is separated into number of parallel thin band sub-channels which prompts to level blurring. The individual sub carriers are orthogonal to each to each other and thus it avoids the interference between adjacent sub carriers. OFDM is a broad band system and operates on large bandwidth. Hence it gives higher data rates in wireless transmission.

If the symbol time is very less than delay time then Inter symbol Interference will occur. To overcome this problem the entire bandwidth is divided into sub bands. For each sub band, there will be a sub carry. Hence by this way the symbol time is not less than the delay time.

Mimo-Ofdm System

The framework execution is broke down by MATLAB programming regarding Bit Error Rate. Here the data grouping is created utilizing arbitrary whole number generator. In this model we utilize convolution coding as forward mistake amendment code. The yield is changed over into OFDM images and transmitted through numerous radio wires by STBC system over the multipath blurring channel.

Simulation Results

The MIMO OFDM framework is performed for various balance orders utilizing productive channel coding procedure. The underneath figure demonstrates BER plot of STBC-OFDM framework. By expanding recieving wire number there is a change in BER. Fig: BER graph of STBC – OFDM along with convolution codingFig: Response of Convolution codingFrom the above figure plainly the BER for the framework with convolution coding (CC) is not exactly for the framework without convolution coding. Along these lines the convolution coding diminishes the mistakes as contrasted and encoded BER plots. Fig: BER graph of STBC-OFDM with convolution coding for 2 Tx and 2 Rx8.

Conclusion

The MIMO system provides maximum capacity and maximum BER versus SNR theoretically and it is proved in the simulation results. The primary target of this paper is to assess the execution of MIMO frameworks in remote correspondence. From this paper the MIMO-OFDM performance is decided as better result than SISO-OFDM and MISO-OFDM. It is demonstrated from the recreation comes about acquired from MIMO and MIMO-OFDM with an irregular created information. While comparing the BER vs. SNR among these three systems MIMO-OFDM obtains a better BER value and proved it is efficient for high rate data transmission in wireless communication. As an enhancement, BER rate is decreased by increasing efficiency. MIMO-OFDM can be compared with other similar techniques and the performance should be evaluated.