Design and Implementation of a flexible Random Access wireless Transmitter


Ubiquitous wireless connectivity is one of the key research fields of the next 10 years. The anytime, anywhere paradigm of wireless connectivity is expected to have a profound impact on our lives.
The number of devices capable to interconnect is steadily increasing, posing new and interesting research questions. A remarkable example is the quest for an efficient way to manage the access of a large number of terminals to a shared wireless medium, which is of paramount importance in order to increase the overall quality of service perceived by the users. One of the possibilities for managing the access to the medium is the Random Access (RA) paradigm, which, in its simplest ALOHA version, allows the devices to transmit whenever they have data, regardless of the activity of other peers and with the risk of creating collisions among concurrently sent packets. Based on this very simple paradigm, more and more efficient schemes have been proposed in the recent past, improving performance while adding complexity both at the receiver and at the transmitter side. As to the latter, multi-packet transmissions, pseudo random seed generation and advanced coding schemes are only some of the new features that are currently under investigation and deployment.
Within this context, DLR is investigating a satellite-based maritime communications scenarios, where a large number of ships travelling on the seas or oceans need to exchange data among each other or with a station on the ground. Data are sent from the see to the satellite using RA, and a high efficiency of the communication system has to be achieved.

Goal of the thesis:

As a first step towards the definition of a maritime satellite system, the development and implementation of a portable wireless transmitter will be carried out. Such a device will be of use as a proof of concept for some key ideas and algorithms for advanced RA techniques later to be refined.
To this aim, the candidate shall develop a portable transmitter with wireless capabilities, composed by a Linux based micro-PC and a radio frontend working in the WiFi frequency bands, and able to support different RA schemes. The candidate will be responsible of the following activities:

  • setup of the basic transmitter system, with proper connection and interfacing of a micro-PC and a radio frontend
  • definition of a transmitter software architecture capable of effectively coping with different random access schemes
  • software design of the transmitter
  • implementation of the defined features in the portable wireless transmitter
  • definition and realization of a test campaign

Key tasks:

  • Review and understand the state-of-the-art RA protocols and their features
  • Definition, development and implementation of the transmitter, including:
    • Implementation in the micro-PC of the functionalities necessary to acquire an external clock signal via Ethernet
    • Implementation in the micro-PC of the control functionalities required to send and receive data through the wireless frontend
    • Implementation in the micro-pc environment of all the functionalities (protocol stack) that are necessary to realize the transmission of data packets following different random access schemes
  • Simulate and evaluate test scenarios of the designed transmitter


  • Studies in electrical or communications engineering or computer science
  • Basic knowledge of layer 2 (medium access) protocols
  • Good knowledge about Linux operative systems
  • Good programming skills (C/C++)
  • Knowledge about embedded programming
  • Basic knowledge of the IAR suite for embedded programming is a plus, but not a prerequisite


6 months


As soon as possible

Federico Clazzer
Deutsches Zentrum für Luft- und Raumfahrt (DLR)

Institut für Kommunikation und Navigation
, Satellitennetze
Tel: +49 8153 28-1120

Fax: +49 8153 28-2844

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