Design and analysis of turbo codes on Rayleigh fading channels

Reconfiguration concept represents reconfigurable functionalities of the radio interface for mobile radio systems. Particularly for the physical layer, some possible reconfigurable architectures can be identified. We focus on outer interleaving for turbo codes, which can improve their performance in flat Rayleigh fading environment. The larger the number of columns in the outer interleaver, the better is the performance, but with the penalty of more complexity and delay. Furthermore, an incorrect choice of the number of columns can increase the bit and frame error rates. Therefore, it would be advantageous to reconfigure the outer interleaver in different operating environments with the optimum number of columns. Using two different data frame lengths, in this contribution simulation results are presented for the four possible outer block interleaver configurations specified for the 3GPP mobile standard in the case of flat Rayleigh fading channel. It is shown that different operating environments require an optimum number of columns in terms of bit error rate and frame error rate performance. Finally, frame fade duration is considered and the effect of the product of the Doppler frequency with the frame duration on the performance for the four different 3GPP outer block interleaver configurations is discussed.

Section: Outer Block Interleaving In Fading Environmentmentioning

confidence: 99%

Reconfiguration Aspects and a Reconfigurable Outer Block Interleaver for 3G Applications

Chaikalis

2006

“…The quantity α k (s) represents a state likelihood at time k based on a forward sweep through the trellis; and β k (s) represents a state likelihood based on a backward sweep through the trellis. The γ i (y k , s , s) is the transitional probability that can be expressed as in [11]:…”

Section: The Map Algorithm With Modified Llrmentioning

confidence: 99%

Turbo Code with Modified LLR and Performance Analysis for Bluetooth Packets in Indoor Environments

Kahveci

Kaya

2009

Most of the restrictions in indoor environments do not exist for outdoor sites. The main limitations for indoors are the attenuation of walls and the multipath fading effects. The signal propagation is limited by the standard free space path loss in outdoor environments or free space. The loss in free space is usually equal to the range squared whereas the loss exponent for indoors is more like the 4th power. This study investigates the performance of turbo codes with modified Maximum-A-Posteriori (MAP) decoding algorithm for Bluetooth data packets in indoor environments over the frequency selective Rayleigh fading channels; which are also called as indoor wireless communication channels. In order to reduce the computational complexity of turbo decoders, MAP algorithm is modified in this study. Bit error rate (BER) versus energy of bit-to-noise ratio (E b /N o ) of modified MAP algorithms for Bluetooth data packets at 2.4 GHz industrial-scientific-medical (ISM) band are evaluated by means of computer simulations. Thus, modified logarithmic likelihood ratio (LLR) method can significantly reduce the computational complexity of the MAP algorithm. Furthermore, the performances of different types of forward error correction (FEC) coding for Bluetooth data packets are compared in the study.

“…The main performance losses for a wireless coded CDMA system are caused by MAI and by the poor capacity of error correction of the turbo codes on slowly fading channels [145,146].…”

Section: Iterative Mud For Wireless Multiuser Mimo Networkmentioning

confidence: 99%

Reconfigurable Antenna for Future Wireless Communication Systems

Morosi

Marabissi

et al. 2007

This paper deals with the processing techniques which are known as reconfigurable antennas: these methods are foreseen to be a booster for the future high rate wireless communications, both for the benefits in terms of performance and for the capacity gains. In particular, adaptive digital signal processing can provide improved performance for the desired signal in terms of error probability or signal-to-noise ratio while the bandwidth efficiency can be increased linearly with the number of transmitting and receiving antennas. In this article, the main antenna processing techniques are reviewed and described, aiming at highlighting performance/complexity trade-offs and how they could be implemented in the future systems. The coexistence of all these different technologies in a wireless environment requires high efficiency and flexibility of the transceiver. Future transceiver implementations which are based on the Software Defined Radio technology are also reviewed and described.