Abstract
The symbol error probability (SEP) and signal to noise ratio (SNR) performance of time-hopping (TH) M-ary Pulse Position Modulation (PPM) systems in the presence of multiuser interference (MUI) is deeply studied in this project. Contrary to previous studies restricted to binary modulation formats, we analyze and evaluate the performance of such multiuser TH systems employing M-ary pulse position modulation (PPM).
Saving communication resources and improving quality of service are the major aims of this project, as we propose a novel TH M-ary PPM technique that increases the transmission data rate with enhanced Symbol Error Rate (SER).
It’s worth mentioning that we were unable to continue the work of graduation project 1 “Digital Terrestrial Television”, the reason is that we were expecting the arrival of Universal Software Radio Peripheral (USRP) platform to build the digital terrestrial television system using GNU radio, unfortunately, the ministry of communication could not bring it on time, so the recommendation was to move on to this project.
Ultra Wideband (UWB) technology is the primary candidate for the physical layer of the upcoming standards for wireless personal area networks, since it provides reliable high-speed data transmission at short ranges over severe multipath conditions. It also exhibits robust Multiple Access (MA) performance with little interference to other communication systems sharing the same bandwidth due to its very low Power Spectral Density (PSD). It also offers a promising solution to the RF spectrum drought by allowing new services to coexist with current radio systems with minimal or no interference. This coexistence brings the advantage of avoiding the expensive spectrum licensing fees that providers of all other radio services must pay.
The fundamental characteristic of UWB is the extremely large bandwidth, which is required since very narrow pulses of appropriate shape and sub nanosecond duration, are being used by the transmitted signal.
One of the most widely studied schemes for UWB communications employs Pulse Position Modulation (PPM) combined with Time Hopping (TH) as its multiple access technique. The UWB pulses are time hopped within a fixed time window (frame) and each transmitted symbol is spread over several pulses in order to facilitate multiple users.
In PPM the position of each pulse, in relation to the position of a recurrent reference pulse, is varied by each instantaneous sampled value of the modulating wave, it used exclusively for transferring digital signals and cannot be used with analog systems. Also it used for transferring simple data and is not effective at transferring files.
Due to the important role of the TH-M-ary PPM modulation technique, we will focus our study on its performance and propose a novel improvement for such a technique with main target of improving the overall system performance under interference dominated system.
Pulse position modulation has many purposes, especially in RF (Radio Frequency) communications. For example, pulse position modulation is used in remote controlled aircraft, cars and boats. Also it’s often used in optical communication, such as fiber optics, in which there is little or no multipath interference, in the next figure (figure 1.1) we can see how PPM is used in optical fibers, i.e. sending a laser pulse in a random location after dividing the frame into number of frames.