Multi Carrier Frequency Hopping Spread Spectrum Techniques With Quasi-Cyclic Low Density Parity Check Codes Channel Coding
Loading...
Date
2010-04
Authors
Yahya, Abid
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This work presents a new proposed Multicarrier Frequency Hopping Spread
Spectrum (MCFH-SS) system employing Quasi-Cyclic Low Density Parity Check
(QC-LDPC) codes instead of the conventional LDPC codes. A new technique for
constructing thc QC-LDPC codcs bascd on row division method is proposed. The
new codes offer more flexibility in terms of high girth, multiple code rates and block
length. Moreover, a new scheme for channel prediction in MCFH-SS system is
proposed. The technique adaptively estimates the channel conditions and eliminates
the need for the system to transmit a request message prior to transmitting the packet
data. The ready-to-use channel will be occupied with a Pseudonoise (PN) code and
use for transmission or else, it will be banned. The new QC-LDPC codes are
compared with other well established LDPC codes. The Bit Error Rate (BER)
performance of the proposed QC-LDPC codes is evaluated and compared for short to
longer block lengths with different code rates and fractional bandwidth, p. The new
QC-LDPC codes show good BER performance as compared to the renowned
Mackay and PEG codes for given values of Eb / No by 0.15 dB and 0.1 dB at a BER
oflO-7 respectively. The proposed QC-LDPC codes are implemented on FPGA chip
using Xilinx Spartan-3E development board. The results obtained for the hardware
implementation of the proposed QC-LDPC codes with partial-parallel architecture
accomplishes a throughput of 111.6 Mbps.
Analysis of the hardware implemented QC-LDPC codes reveals that the new codes
require less memory space, thus decreases the hardware complexity. The new QCLDPC
codes are employed in the proposed MCFH-SS system as forward error
correction (FEC) codes. The perfonnance of the proposed MCFH-SS system at
diversity level 4, outperfonns MCFH-SS system (without channel prediction
scheme) with 0.5 dB gain at p =1, when both systems are coupled with the proposed
QC-LDPC codes. It is shown from simulation results that for 40 users at Eb / Jo of 5
dB, the proposed MCFH-SS system and fast frequency hopping spread spectrum
(FFH-SS) system have BER of 10-6 and 10-4 respectively. The significant
perfonnance enhancement has been observed for the same number of users (40) at
high Eb / Jo of 50 dB that the proposed MCFH-SS system has BER of 10-7 while
FFH-SS system with BER oflO-3
• Simulation results show that the proposed MCFHSS
system achieves considerable advantage over the FFH-SS system when the
systems are used under similar conditions. The overall proposed system is
implemented on a hardware platfonn comprised of a communication development kit
that is interfaced with Xilinx development board.
Description
Keywords
Transmit a request message prior , To transmitting the packet data