Performance Evaluation for Super-Orthogonal Concatenated Convolutional Coding Scheme for Multiple Access Applications over Nonlinear Satellite Channels

Hala M. A. Mansour; Labib Francis Gergis; Mostafa A. R. Eltokhy; Hoda Z. Said

In digital satellite communications there are many earth stations and satellites sharing the transmission channel hence, a multiple access scheme is needed in order to increase the number of simultaneous users and make efficient utilization of power and bandwidth of the channel. Code-division multiple-access (CDAM)has been considered as one of the most efficient and reliable schemes for multiple access satellite communications. In CDMA system, ultimate capacity can be achieved using low rate error correcting codes to perform both coding and spreading. Orthogonal and super-orthogonal convolutional codes have been proposed for this purpose. The super-orthogonal convolutional code performs well in very low rates and requires less bandwidth expansion than the orthogonal convolutional code. Concatenating two or more super-orthogonal convolutional codes through interleavers achieves near Shannon limit performance. A major drawback in satellite communications is the presence of high power amplifier which is needed to provide the signal power required to overcome the large distance between transmitter and receiver. The high power amplifier introduces nonlinear distortion to the amplified signal when it operates in its maximum power efficiency region which results in degradation to the CDMA signal. In order to compensate for this nonlinear response a linearization technique is employed or the operating point of the amplifier is backed-off to its linear region. In this paper we present a new low rate concatenated convolutional coding scheme suitable for spread spectrum CDMA applications. Analysis for the bit error probability performance of the proposed coding scheme is derived in both additive white Gaussian noise (AWGN) channel, and nonlinear satellite channel. Results showed that, the proposed coding scheme achieves superior performance compared to the conventional low rate convolutional codes.

Select Volume / Issues:

• Volume 3 Issue 6, Nov. 2012

Year:

2012

Type of Publication:

Article

Keywords:

CDMA; Code Concatenation; HPA; Low Rate Codes

Journal:

IJECCE

Volume:

3

Number:

6

Pages:

1594-1600

Month:

November