介绍了TFSK(Time Frequency ShiftKeying)-MFSK(Multiple Frequency ShiftKeying)的数据传输方法。该系统采用纠错能力很强的串行级联码对信号进行编码,串行级联码的外码选用(255,223)RS码,内码选用(2,1,7)卷积码,信号译码采用软判决维...介绍了TFSK(Time Frequency ShiftKeying)-MFSK(Multiple Frequency ShiftKeying)的数据传输方法。该系统采用纠错能力很强的串行级联码对信号进行编码,串行级联码的外码选用(255,223)RS码,内码选用(2,1,7)卷积码,信号译码采用软判决维特比(V iterbi)译码方式。TF-SK-MFSK调制改善了MFSK因M增加导致频带利用率低的情况,能够更加充裕地组合各个频率进行信号传输,组合信号方式可借鉴跳频扩频思想,不容易受限于频率范围非常窄的水声信道,有效地对抗信号的干扰和衰减。展开更多
Wireless communication systems have greatly advanced during the last years. A significant contributor in these systems’ performance has been Orthogonal Frequency Division Multiplexing (OFDM). Since its invention, it ...Wireless communication systems have greatly advanced during the last years. A significant contributor in these systems’ performance has been Orthogonal Frequency Division Multiplexing (OFDM). Since its invention, it is considered to be a technological leap. This leap in splitting an information stream in multiple frequency carriers has been adapted by various scientists working on the development of wireless systems. Moreover, as OFDM presented excellent tolerance of channel fading and noise signals, the evolvement in terms of speed and reliability was consequent, because only a small stream of information is lost due to noise effects. OFDM along with the knowledge that Turbo codes is another excellent scheme of reducing BER, has triggered us to expand our research. So, we experimented in simulation level not only in joining OFDM with Turbo Codes but even in finding a better Turbo scheme compared to a typical PCCC, SCCC and a Convolutional encoder with Viterbi decoder. As the last goal has already been accomplished, in this paper is presented the new OFDM system consisted of our Turbo scheme. The analysis of the previous system took into consideration the effects of an AWGN channel. Also, this noise analysis was conducted using a simulation platform with specific attributes such as transmitting and receiving fixed number of subcarriers (2048 carriers after IFFT block) while using different types of convolutional concatenated codes, such as PCCC (Parallel), SCCC (Serial) and the new PCCC scheme. The results clearly show not only the improvement in the BER performance of the Turbo Coded OFDM systems (compared to others consisted of Viterbi decoders) but the overall superiority of the proposed design.展开更多
文摘介绍了TFSK(Time Frequency ShiftKeying)-MFSK(Multiple Frequency ShiftKeying)的数据传输方法。该系统采用纠错能力很强的串行级联码对信号进行编码,串行级联码的外码选用(255,223)RS码,内码选用(2,1,7)卷积码,信号译码采用软判决维特比(V iterbi)译码方式。TF-SK-MFSK调制改善了MFSK因M增加导致频带利用率低的情况,能够更加充裕地组合各个频率进行信号传输,组合信号方式可借鉴跳频扩频思想,不容易受限于频率范围非常窄的水声信道,有效地对抗信号的干扰和衰减。
文摘Wireless communication systems have greatly advanced during the last years. A significant contributor in these systems’ performance has been Orthogonal Frequency Division Multiplexing (OFDM). Since its invention, it is considered to be a technological leap. This leap in splitting an information stream in multiple frequency carriers has been adapted by various scientists working on the development of wireless systems. Moreover, as OFDM presented excellent tolerance of channel fading and noise signals, the evolvement in terms of speed and reliability was consequent, because only a small stream of information is lost due to noise effects. OFDM along with the knowledge that Turbo codes is another excellent scheme of reducing BER, has triggered us to expand our research. So, we experimented in simulation level not only in joining OFDM with Turbo Codes but even in finding a better Turbo scheme compared to a typical PCCC, SCCC and a Convolutional encoder with Viterbi decoder. As the last goal has already been accomplished, in this paper is presented the new OFDM system consisted of our Turbo scheme. The analysis of the previous system took into consideration the effects of an AWGN channel. Also, this noise analysis was conducted using a simulation platform with specific attributes such as transmitting and receiving fixed number of subcarriers (2048 carriers after IFFT block) while using different types of convolutional concatenated codes, such as PCCC (Parallel), SCCC (Serial) and the new PCCC scheme. The results clearly show not only the improvement in the BER performance of the Turbo Coded OFDM systems (compared to others consisted of Viterbi decoders) but the overall superiority of the proposed design.
