This paper proposes Twin Turbo (T2) MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing). The advanced iterative decoder, called the T2 decoder, decreases the transmission error rate compared to conventional turbo decoders because it uses the correlation information among the bits mapped on an identical symbol of multi-level modulation and updates the channel reliability. When T2 is applied to a MIMO-OFDM, the required symbol energy to noise power density ratio (Es/N0) can be reduced more effectively than when T2 is applied to SISO (Single Input Single Output). This is because T2 can use the correlation among the bits not only mapped on an identical symbol but also transmitted from different antennas. Moreover, T2 achieves good performance in a correlated MIMO channel because the average minimum squared Euclidean distances between symbol replica candidates consisting of signals transmitted from multiple transmitter antennas are reduced. Computer simulations verify that the required Es/N0 of T2 MIMO-OFDM using 16QAM is 1.9 dB lower than that of a conventional turbo decoder when the correlation coefficients of transmitter and receiver antennas are 0.8. A computational complexity analysis clarifies the relation between the increase in computational complexity and the reduction in the required Es/N0.

FEC (Forward Error Correction) is widely used to recover packet loss over the Internet since it does not involve additional network delay. However, FEC still needs much additional network bandwidth for redundancy, and does not consider the priority or the importance of video frames to generate redundant data. In this paper, we present Periodic FEC (PFEC) to make up for the shortcomings of FEC. PFEC divides frames into high-priority frames and low-priority frames, and gives redundancy only to high-priority frames. As specific examples, we describe two types of PFEC: Media-Independent PFEC and Media-Dependant PFEC. Moreover, based on the two-state continuous time Markov chain, we propose redundancy control algorithms of the PFEC schemes that can adjust the amount of redundancy to optimal levels depending on network loss conditions. For better performance, we also consider UEP (Unequal Error Protection) based on PFEC that gives redundancy to low-priority frames as well as high-priority frames. Experimental results show that compared with FEC, PFEC reduces the amount of redundancy considerably but degrades PSNR slightly, and UEP based on PFEC economizes redundancy without the degradation of the PSNR.

In the wireless ATM network, the key issue is to guarantee various QoS (Quality of Service) under the conditions of the limited radio link bandwidth and error prone characteristics. In this paper, we show a combination method of the error correction schemes, which is suitable to establish multimedia wireless ATM Networks while keeping an efficient use of the limited bandwidth. We consider two levels of FEC; a bit-level and a cell-level to guarantee cell loss probabilities of real time applications. By combining two levels of FEC, various requirements on cell loss can be met. We then apply the bit-level FEC and ARQ protocol for the data communication; tolerant to the delay characteristics. Through the analytical methods, the required overheads of FECs are examined to satisfy the various QoS requirements of CBR connections. The mean delay analysis for the UBR service class is also presented. In numerical examples, we show how the combination scheme to guarantee various cell loss requirements affects the call blocking probability of the CBR service class and the delay of UBR service class.