Energy efficient resource allocation in mobile communications
Σιγάλας, Κωνσταντίνος Π.
The current evolution of mobile communications may be something very difficult to predictor even imagine 20 years ago. The rapid growth of mobile communications has resulted in constant and increasing demand for wireless and multimedia communication. In this course, the greatest contribution equipments of modern market with a unified and functional system of mobile communications, and the plethora of multimedia applications are now available to users and are increasing rapidly. More specifically, in the last decade the third generation (3G) - Universal Mobile Telecommunication System (UMTS) cellular networks have begun to rise and the usage has spread universal. 3G networks have replaced the existing second generation mobile networks and moreover, are in position offering higher (broadband) speed access and advanced services to mobile customers-users. This led to the further development of 3G networks and to the adoption of new technologies, with main representative the High Speed Packet Access (HSPA) technology. This technology is the natural evolution of UMTS, which is mentioned in the literature as 3.5G or 3G+, indicating the upgrade. However, despite the fact that HSPA technology is expected to allow the provision of numerous broadband services, the 3rd Generation Partnership Project (3GPP), the authorized organization for the standardization of new mobile technologies, already examines new technologies that will prevail in the mobile communications industry over the next decades. This novel project is known as Long Term Evolution (LTE) and aims at achieving increased data rates and reduced latency compared to UMTS and HSPA networks. Simultaneously, multimedia content and service providers show an increased interest in supporting multicast data in order to effectively manage and re-use the available network resources. Additionally, more and more users require access to applications and services that until today could only be accessed by conventional wired networks. Thus, real time applications and services may face low penetration today; however, they are expected to gain high interest in future mobile networks. These applications actually reflect a modern, future way of communication among mobile users. For instance, mobile TV is expected to be a “killer” application for 3G’s. Such mobile TV services include streaming live TV (news, weather forecasts etc.) and streaming video (such as video clips). All the above constitute a series of indicative emerging applications that necessitate advanced transmission techniques. One of the most significant steps towards the provision of such demanding services is the introduction of Multimedia Broadcast/Multicast Service (MBMS). MBMS is a point-to-multipoint service in which data is transmitted from a single source entity to multiple destinations, allowing the networks resources to be shared. Actually, MBMS extends the existing UMTS infrastructure and efficiently uses network and radio resources, both in the core network and most importantly, in the air interface of UMTS, where the bottleneck is placed to a large group of users. Therefore, MBMS constitutes an efficient way to support the plethora of the emerging wireless multimedia applications and services such as IP video conferencing and video streaming. The main requirement during the provision of MBMS multicast services is to make an efficient overall usage of radio and network resources. This necessity mainly translates into improved power control strategies, since the base stations’ transmission power is the limiting factor of downlink capacity in UMTS networks. Under this prism, power control is one of the most critical aspects in MBMS due to the fact that downlink transmission power in UMTS networks is a limited resource and must be shared efficiently among all MBMS users in a cell. Moreover, power control aims at minimizing the transmitted power, eliminating in this way the intercell interference. However, when misused, the use of power control may lead to a high level of wasted power and worse performance results. After taking into account the above analysis, objective of this dissertation is the study of power control issues in next generation mobile communication networks as well as finding ways and methods /mechanisms for optimization. Being evaluated of existing transmition channels of UMTS and HSPA technology, based in applied force to be assigned by the base station for each of them, the transmission rate, the number of users that can serve, the quality of service for each user, the maximum possible coverage of the