This paper presents about error minimization in OFDM system. In conventional system, usually using channel coding such as BCH Code or Convolutional Code. But, performance BCH Code or Convolutional Code is not good in implementation of OFDM System. Error bits of OFDM system without channel coding is 5.77%. Then, we used convolutional code with code rate 1/2, it can reduce error bitsonly up to 3.85%. So, we proposed OFDM system with Modified Convolutional Code. In this implementation, we used Software Define Radio (SDR), namely Universal Software Radio Peripheral (USRP) NI 2920 as the transmitter and receiver. The result of OFDM system using Modified Convolutional Code with code rate is able recover all character received so can decrease until 0% error bit. Increasing performance of Modified Convolutional Code is about 1 dB in BER of 10-4 from BCH Code and Convolutional Code. So, performance of Modified Convolutional better than BCH Code or Convolutional Code. Keywords: OFDM, BCH Code, Convolutional Code, Modified Convolutional Code, SDR, USRP

A high PAPR value is one of important weaknesses in OFDM systems. Several reduction techniques are applied to reduce PAPR including partial transmit sequence (PTS) as well as clipping and filtering (CF). Adaptive iterative clipping and filtering is a development of iterative clipping and filtering techniques. In this paper, a combination of Partial transmits sequence and adaptive iterative clipping filtering (PTS-AICF) techniques on multi-antenna OFDM transmitters was carried out. The simulation results showed that combined technique application had a better performance than non-combined technique (PTS), either for two or four antennas, and also for different sub block numbers. Performance was also influenced by iterations number on AICF section, the more iterations were used, the better the reduction technique performance was because it produced smaller PAPR 0 value.