Rapid mobile data traffic growth is foreseen next few years, the biggest part of which will be video data. It is challenge for researchers to find solutions how to offload traffic from mobile cellular networks as well as expand the broadband network coverage. Next generation 5G mobile networks will use solutions enabling direct data exchange between users without involvement of base station. One of such would be IEEE 802.11 based wireless ad-hoc network. However, such network is not suitable enough for video transmission as it is unpredictable and has limited capacity. The main aim of the research presented in this thesis is to increase data transmission efficiency in wireless ad-hoc network by using multi-path transmission. Data flow can be split over several paths increasing in such way aggregated data rate. Such approach causes several research problems. First, for multi-path video transmission development of appropriate video coding and transmission techniques are required. Secondly, multipath routing suffers from interference between paths degrading capacity. Ad-hoc network parameters have been comprehensively analysed for network behaviour understanding during multi-path video transmission. It resulted in a new model presenting complex dependences and interconnections between ad-hoc network parameters. Interference influence on data rate has been studied both experimentally in ad-hoc network testbed and by simulation. To improve multi-path transmission efficiency the techniques to reduce interference have been investigated. The wise path selection to reduce path coupling and smart antennas are found as appropriate solutions to cancel interference and increase data rate. This research work is based mainly on computer simulation using improved analytical capacity estimation method and elaborated MATLAB network simulation tool. Parallel computing in HPC cluster has been used to decrease simulation time. Results show that multi-path transmission combined with interference decreasing techniques improves data transmission efficiency in wireless ad-hoc network. The research resulted in recommendations on how to select suitable paths that can be used for decision making in routing protocols. The results of this doctoral research have been published in 8 research papers, presented at 11 international scientific conferences and used in 2 research projects. The thesis consists of introduction, 5 main chapters, conclusion, list of bibliography and 6 appendices. It has totally 190 pages, 65 figures, 10 tables un 126 references.