# Networking of Multi-Robot Systems: Architectures and Requirements
## 1 Introduction  
The recent technological advances in robotics has opened the door for many useful automation applications in diverse domains. These advances include major enhancements in sensing, actuating, processing, analyzing, communications, recognition, leaning, perception, and controlling capabilities. With such advancements, many applications can be enhanced with better productivity, accuracy, quality, reliability, cost-effectiveness, flexibility, and safety using robots or robotic systems. For example, these capabilities facilitated the development of advanced industrial robot systems that automate and enhance manufacturing processes to produce more products with better accuracy and quality in more cost-effective manners. They also allowed for the development of farm robots to handles agriculture processes and increase productivity, thus reducing the costs of farming and increasing accuracy in handling crops. Furthermore, they allow to develop maintenance robots to perform inspection and repair tasks in difficult and dangerous places such as in underwater facilities and infrastructures spanning rough and inaccessible terrains. Moreover, they allow to develop security robots that support the monitoring of important infrastructures such as oil, gas, and water pipelines and power stations. All these and many other applications will emerge and become more common in the near future as the driving technologies in robotics and supporting systems mature. While some applications require the use of a single robot to effectively automate and enhance a process, there are others that require using multiple robots working together to achieve certain objectives in more cost-effective or/and efficient manners. Multiple robots used for any of these applications can be combined in what is referred to as a Multi-Robot System (MRS). It is worth noting that some researchers use the term Multi-Robot Network (MRN). Although both terms refer to the same systems, we will use the term MRS subsequently in this paper. Any MRS has several robots working together to achieve a certain application objective. Using an MRS over a single robot provides many benefits [1; 2]:  
* Multiple robots can concurrently work on the task to achieve it faster. * Robots can be heterogenous in their capabilities to provide a cost-effective solution to achieve a task where each robot handles specific components of the task matching its capabilities. * Multiple robots can effectively deal with a task that is inherently distributed over a wide area. * Using multiple robots for achieving a task provides fault tolerance as the presence of multiple robots capable of similar processes can be used to compensate when any of them fails. There are many research efforts in investigating different issues in MRS and providing solutions for these issues. The issues include task allocation [3], distributed intelligence [4], learning [5; 6], coordination [7], coalition formation [8], motion planning [9] and middleware support [10]. In addition, there are some research efforts dedicated for developing application-specific solutions and algorithms for MRS such as patrolling algorithms [11], map merging [12], box-pushing [13], and flocking [14]. However, there is little effort in investigating the communication and networking aspects of MRS. Yet, communication and networks represent the main enabling technology for MRS applications. Robots in an MSR are connected with a network and the performance of this network has direct impact on most other solutions in MRS as well as the final performance of the applications. Some of the available work in this area focus on studying some theoretical aspects of MRS such as communication complexity [15] and localization [16]. In addition, there are some efforts to study specific communication issues for specific types such as small, low-power, low-cost MRS [17] and UAVs [18]. In this paper, we investigate the communication issues and networking models for MRS. We also study the communication requirements of different services in MRS.