editor@iaset.us www.iaset.us TRELLIS CODED MODULATION OVER LAND MOBILE SATELLITE CHANNEL KHALID W. HAMEED Al-Nahrain University Information Engineering College, Baghdad, Iraq ABSTRACT In order to start designing any communication system, simulation is needed and especially when the system design cost is very expensive like satellite link. The simulation make us take the right decision about the system and its component and parameters. One of to the trends enhance the transmission is the use of coding. In this paper the performance of trellis coding modulation (TCM) over land mobile satellite (LMS) channel is presented and compared with other coding method and the absent of coding. It was found that the supplement of coding will not enhance the system always and the TCM is not always give better performance over normal coding in all cases. KEYWORDS: Trellis Coded Modulation over Land Mobile Satellite Communication Channel Using Loo’s Model INTRODUCTION This paper is reported on the performance of two types of trellis coded modulation over land mobile satellite communication channel using Loo’s model. Satellite communication has found its place in practice and is implemented in numerous applications. Some of the more common implementations are Global Positioning Systems, satellite television and marine communications [1]. There is a renewed interest and market opportunities for Mobile Satellite Service (MSS) for it is an attractive approach in areas of world not well covered by existing terrestrial infrastructures [2]. For small, portable or even handheld terminals, the MSSs may suffer from time varying non Line-of-Sight (LOS) fading propagation conditions due to the presence of multipath[2]. A link budget analysis forms the cornerstone of the system design. Link budgets are performed in order to analyses the critical factors in the transmission chain and to optimize the performance characteristics, such as transmission power, bit rate and so on, in order to ensure that a given target quality of service can be achieved [3]. The possible solution to overcome the bad channel condition and decrease BER is to increase transmission power. We can increase the transmission power in terrestrial station but this solution is restricted with the power limitation in mobile units and the satellite itself. One of the key designs in communication systems is the bandwidth efficiency. So the use higher order modulation can make efficient use of bandwidth, but it will enfaces with increase of BER. To make efficient use of power and bandwidth of a system, adaptive scheme for modulation is used; it was discussed over satellite link in [2]. Another solution to enhance the link is the use trellis coded modulation proposed by Ungerboeck in [4]. [5] and [6] had discussed the TCM over satellite channel. But non of them use the QPSK nor use the LMS channel model (Loo's Model). Here in a description of simulation for the transmission over the satellite link depending on Loo’s channel model using MATLAB is presented. SYSTEM MODEL The system model used in the simulation is shown in Figure 1. The core of the model is the transmission channel International Journal of Civil Engineering (IJCE) ISSN(P): 2278-9987; ISSN(E): 2278-9995 Vol. 4, Issue 2, Mar 2015, 19-26 © IASET