Error analysis of data throughput and BER for the wireless OFDM PSK network.
Wireless communication has become vital which uses free space as a communication channel. Now a days we mostly use digital signals, DSP and communication is also in digital, because it has immunity (protection)to noise and external interference. The main objective of transmitting digital information is to minimize errors. It can be done by implementing error correction and detection techniques in digital communication systems. These techniques enable addition of extra bits to the transmitted message. The extra bits convey no information by themselves but it has the ability to detect or correct errors in the regenerated message. There are two types of error messages.
1. Lost message which never arrives at the destination.
2. Damaged message which recognized at the destination but contains one or more transmission errors.
There are two transmission handling errors
* Error detecting codes
* Error correcting codes.
Error detecting codes has enough redundant information with each transmitted message to enable the receiver for determining the error occurred. Parity bits, frame and block check characters and cyclic redundancy characters are examples for error detecting codes. Error correcting codes include sufficient extraneous information along with each message enabling the receiver to determine when an error has occurred and which of the bit is in error.
Forward error correction technique:
FEC is the error correction scheme that detects and corrects the transmission errors when they are received, without the need of retransmission. With FEC, redundant bits are added to the message before transmission when the error is detected, the redundant bits are used to determine which bit is in error, and the simple method of complementing is correcting the bit. The number of redundant bits necessary to correct errors is much greater than the number of bits needed to simply detect errors.
FEC is generally limited to one, two, three bits.
* There is several error controlling codes that are available.
* RS (Reed-Solomon) and BCH (Bose-Chaudhari-Hocquenghem) are the most important codes used to detect and correct multiple symbol error.
Orthogonal frequency division multiplexing (OFDM) schemes are utilized as a digital multicarrier modulation technique. In most of the parallel data streams or channels to carry the data an immensely colossal number of proximately spaced orthogonal sub-carrier signals will be used. Each of the sub carriers are modulated based on the conventional modulation schemes. Each subcarrier is orthogonal to other subcarriers; where OFDM is differentiated from the commonly used FDM. OFDM helps to simultaneously transmit multiple signals in a single transmission path. The signal is modulated by data it travels with its own unique frequency range. In the OFDM spread spectrum method the data is distributed over a broad number of carriers which are spaced flat of accurate frequency. The orthogonality is achieved by this spacing where it will prevent the demodulators by viewing frequencies other than to their own. OFDM transceiver is shown in Figure1.
I. Bose-Chaudhri-Hocquenghem Codes:
In wireless applications, these are among the most potent cyclic block codes which are widely utilized. BCH codes are used to correct multiple random errors. From the specification of the error-correcting capability the code can be designed. Hamming code is a special type of BCH Code whose error correcting ability is 1.For any type of positive pairs of integer v and t; there will be binary(n,k) BCH code with given parameters. This code can rectify all coalescences of t or few errors.
II. Reed-Solomon Codes:
They are a widely used subclass of non-binary BCH codes. The RS codes are well apposite for burst error rectification. In addition to that; efficient coding methods are easily available for the RS-codes. If both type of error are common a technique called interleaving is employed. It is capable of detecting and correcting multiple symbol errors. They are most well suited as multiple-burst-bit-error correcting codes.
III. Awgn Channel:
AWGN channel will integrate the white Gaussian noise to signals that pass through it. Additive white Gaussian noise(AWGN) channels are circumscribed with the noise on high data rate communication.
The signal received with the interval 0<t< T can be expressed by, where, n(t) indicates the sample function of AWGN process with spectral power density.
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IV. Comparison Of Rs And Bch With Awgn Channel:
Wireless communication has become vital which uses free space as a communication channel, the cognitive radio is a technology which proved that it is best in the developing wireless systems. The graphical results obtained shows that BCH codes is the best code than Recodes. The future works includes the OFDM implementation using three transmitters and three receivers using available bandwidth. Cognitive radio technique is to sense the spectra and to mobilize it. Withal the consideration for hardware entelechy of the system is to be made. The result is stimulated using LABVIEW Software.
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(1) M. Meena and (2) Dr. V. Rajendran
(1) (Research scholar) Dept of ECE, VELS University Chennai, Tamil Nadu
(2) (Supervisor &HOD) Dept of ECE, VELS University Chennai, Tamil Nadu
Received 7 June 2016; Accepted 12 October 2016; Available 20 October 2016
Address For Correspondence:
M. Meena, (Research scholar) Dept of ECE, VELS University Chennai, Tamil Nadu
Caption: Fig. 1: OFDM transceiver.
Caption: Fig. 2: BCH Lab VIEW Coding
Caption: Fig. 3: RS Lab VIEW Coding
Caption: Fig. 4: Comparison of RS and BCH with AWGN Channel
Caption: Fig. 5: BCH versus RS comparison over AWGN channel
Table I: BCH and RS Parameters PARAMETERS BOSE-CHAUDHRI-HOCQUENGHEM REED SOLOMON BLOCK LENGTHS n = 2 [conjunction] v-1 N=2 [conjunction] v-1 NO OF CHECK BITS N -k<= vt n-k= v(2t) MINDISTANCE Dmin>=2t+1 Dmin=2t+1 Table 2: Comparison of coding WITHOUT ENCODING 1 BCH CODING Eb/N0 BER 6 0.0039703 0.0023754 7 0.007551170 0.0015202 8 0.0003050412 0.0001450225 9 0.0000500068 0.0000250039 10 0.0000150020 0.00000500089 Table 2: BER System performance in AWGN channel SNR BER 1 0.068 6 0.088 10 0.101 15 0.08075 20 0.087
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|Title Annotation:||Orthogonal frequency division multiplexing|
|Author:||Meena, M.; Rajendran, V.|
|Publication:||Advances in Natural and Applied Sciences|
|Date:||Sep 15, 2016|
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