| Abstract: |
The main focus of this thesis has been the application and evaluation of the hybrid OS/SFH lm technique to the land mobile satellite, macro and microcells communication systems with lroposed improvemellt in the hybrid receiver perfonmmcc throughput the use of adaptivenique and LMMSE detection techniquc.In chapter 4, 5 and 6 we presented the thesis contributions.Llr work, we focused on land mobile satellite and assullIe that the satellite is used as base station ransmission and reception of signals to and from the mobile.pter 2 provide a brief overview of the COMA and hybrid systems, receivers and detectors used. ~apter 3 we provide a brief overview of the modulation techniques, coding techniques and dive. techniques that can be used in the wireless communications.Ilapter 4 we start by reviewing the general techniques Hybrid of DS/SrI I. We then present, the losed mathematical model for the evaluation of performance for the application of the Hybrid SFH system in land mobile satellite, macro and microcellular communication. A key results in thesis is the derivation of the BEP of the hybrid OS/SFH over log-normal shadowing channel inmobile satellite, micro and macrocellular, heside the throughput and delay performance. napter 5 we review the adaptive receiver in fading channel and in COMA system and present ;waluation of the system using adaptive technique with OMSK modulation.hapter 6 we present the proposed adaptive receiver using LMMSE detector for hybrid OS/SFH em and present a comparison with all different kinds of detector techniques (matched filter, rake iver, ... ).For land mobile satellite, micro and macrocell, diversity must be combined with coding for having satisfactory BEP performance. For (Et,/No=8dB), the corresponding BEP for land mobile without coding and diversity equal 510-2, and for system with coding only BEP equal 510-3 and for system with coding and fourth order orMRC IJEP equal 10-? The use of MRC is more beneficial for hybrid OS/SFH than the use or forward error correction.The hybrid OS/SFH system for both light and average shadowing is robust than OS for the large multi-access interference power level for the land mobile satellite. An increase in the multi-access interference power by 20dB will cause BEP degradation with large range from 510-5 to 310-1 for OS and with small range from 510-3 to 510-2 for hybrid OS/SFHHybrid OS/SFH system for micro and macrocell is robust than OS system against variation of the ratio of cochannel interference power to the home channel interference power. An increase in cochannel interference power by 10dB will cause BEP degradation with large range from 10-15 to 10-4 for OS and with small range from 10-4 to 510-1 for hybrid DS/SFH.For different combinations of constant Nand q at fixed bandwidth (qN is constant) and a given bit rate, it can be seen that increasing the code length N yields a better performance than increasing in the number of frequencies q. For the same transmission bandwidth (qN=4000) increa.,.i sing N from 50 to 1000 improve system performance by 6dB.- Increasing the number of the resolvable paths L (depending on the value of the maximum delay spread) degrades the performance of the system because of the increasing level of the multipath interference.- BEP performance of the hybrid DS/SFH systems for both micro and macrocellular is inferior to that of purely OS system. ( for El/No=8dB the BEr for hybrid OS/SFH equal 10-4 while for DS system equal I O-R ).- BEP performance of microcell is generally better than the macrocell. For (Et/No=5dB) the co-rresponding BEP for micro equal 810.3 while for the macro equal 810-1.For land mobile the throughput performance is the best for the nearly direct sequence and is the worst for the nearly frequency hopping.The throughput performance of the hybrid DS/SFH communication system increases with increasing order of diversity. The normalized throughput improved from (0.04 to 0.37) corresp-onding to nondiversity and fourth order MRC. and the corresponding delay also decrease. The higher order of diversity provides a lower bit error probability and, accordingly, a higher packet success probability.10- Increasing the number of users K will increase the bit error probability fiJr lanel mobile satCIlite, micro and macrocellular because of the interference power, which is proportional to K. (increasing number of users from 10 to 150 will degrade the BEP by 6dB)1] - The throughput performance comparison between the nearly direct sequence nearly frequency hopping and the hybrid DS/SFH for the macrocellular shows that the throughput performance improves with increasing code length N.12- Insertion of the adaptive filter in the hybrid DS/S FIi receiver reduces the effect of shadowing fading, and multipath effects that encountered in land mobile satellite. An improvem-ent of 10dB can be obtained.13- The proposed hybrid OSISFH receiver using LMMSE detection technique olltperform other kinds of hybrid DS/SFH receivers. For exanple the BEr 10-2 ofrequries El/N,,=8dB for the Rake receiver while for LMMSE will be the E”/N” will be J .9dB.14- BEP performance of the hybrid DS/SFH is superior to that of purly FH and inferior to that of purly DS.15- Throughput delay improves with increasing order of diversity. It decrease from 5103 to 120 corresponding to nondiversity and fourth order M RC.16- Throughput delay degrades with increasing resolvable paths L.17- Throughput and perfonnance delay for microcel1 is better than that of macrocell. The throughput for macr equal. 18 while for micro equal 0.38 and the corresponding delay for macr is 103 while for micro is 500.18- For obtaining a reasonable value for the throughput and delay a combination of FEe and sufficiently high order of diversity is necessary especially in the case of heavy shadowing.J 9- The main ways for performance cnhancement is increasing the order of diversity, increasing the code length N ( decrease the chip time) and use of FEe code, but this require lager bandwidth and fastcr hardware.
|
|
|