Evolutionary algorithms for geographic load balancing using a distributed antenna system

#Distributed antenna systems (DAS) have been widely implemented in state-of-the art cellular communication systems to enhance wireless network capabilities. DAS has discernible advantages over conventional communication systems, due to its architectural design compared to traditional wireless network installations. Recent studies have identified other potential advantages for using DAS. However, most of the recent work on DAS does not focus on load balancing techniques for optimizing such performance. Therefore, there is a need in the art for improved methods and systems related to load balancing in DAS.

#With the increase of cellular users, traffic hot spots and unbalanced traffic distributions are common in wireless networks. Embodiments of the present invention relate to a load-balancing system for mobile networks that optimizes cellular performance according to the traffic geographic distribution in order to provide a high quality of service (QoS). In some embodiments, a Virtualized Distributed Antenna System (VDAS) fed by a multi-sector Base Transceiver Station (BTS) has the ability to distribute the cellular capacity over a given geographic area. The VDAS can focus a portion of the BTS capacity around traffic “hot spots” and redistribute the remaining BTS capacity over the other cells. To enable load balancing among Distributed Antennas (DAs), embodiments of the invention may dynamically allocate DAs to the BTS sectors, depending on the time-varying traffic. VDAS sectorization is formulated as an integer linear constrained optimization problem in some embodiments, which minimizes the blocked calls and handoffs as two important key performance indicators (KPIs) in the network. In some embodiments, a VDAS sectorization technique considers connected and compact sectors to minimize the number of handoffs, while satisfying the capacity demand at each sector. Various embodiments include at least one of two evolutionary algorithms to solve the problem: Genetic Algorithm (GA) and Estimation Distribution Algorithm (EDA). Results are presented that evaluate the system performance for different traffic scenarios. Results demonstrate that the two algorithms attain excellent KPIs for small-scale networks.

#Embodiments of the present invention include methods and apparatuses for optimizing traffic in VDAS wireless communications systems. Sectorization of DRUs is examined to balance the traffic in the VDAS LTE system. Proper sectorization is considered to effectively use the resources (licenses) in each sector that satisfies the soft and hard capacity. Connected and compact sectors are proposed to reduce handoffs and interferences. The DRU sectorization is formulated as an integer linear programming problem which minimizes blocked and handoff calls in some embodiments.

#An understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

#FIG. 1 is a schematic illustration of an example Distributed Antenna System (DAS) according to some embodiments.

#FIGS. 2A and 2B illustrate an example methodology according to some embodiments.

#3GPP LTE is a promising candidate for next generation wireless networks. In the last 15 years there has been substantial growth in cellular mobile communication systems. It is imperative to provide a high quality of service (QoS) at a minimum cost. With the substantial increase in cellular users, traffic hot spots and unbalanced call distributions are common in wireless networks. This decreases the quality of service and increases call blocking and dropping. Inter-cell optimization in GSM and UMTS networks is usually delivered at the stage of network planning, and often done manually. As traffic environments change, the network performance will not be optimum. It is therefore necessary to perform inter-cell optimization of the network dynamically according to the traffic environment, especially when cell traffic loads are not uniformly distributed. This is one of the important optimization issues in self-organizing networks (SON) for 3GPP LTE. When the traffic loads among cells are not balanced, the blocking probability of heavily loaded cells may be higher, while their neighboring cells may have resources not fully utilized. In this case load balancing can be conducted to alleviate and even avoid this problem. Additionally, other next-generation networks besides 3GPP LTE may experience similar problems. In some embodiments, the solutions presented herein may apply to those architectures as well.

#According to some embodiments, one approach to solve this problem is to take advantage of aspects of a Distributed Antenna System (DAS). A DAS breaks the traditional radio base station architecture into two pieces: a central processing facility and a set of distributed antennas (DAs) connected to the central facility by a high-bandwidth network. The DAS network transports radio signals, in either analog or digital form, to/from the central facility where all the base stations processing is performed. By replacing a single high-power antenna with several low-power antennas distributed to give the same coverage as the single antenna, a DAS is able to provide more-reliable wireless service within a geographic area or structure while reducing power consumption. In a Virtualized DAS, the traffic load from multiple sectorized eNodeBs, at a hotel station, is distributed to multiple Digital Remote Units (DRU). This synergistic configuration also allows multiple operators to use multiple technologies over the same physical facilities, thereby providing a cost-effective means of furnishing subscribers with high quality, highly reliable communication services. With respect to a Virtualized DAS configuration, multiple DRUs can be dynamically assigned to the different eNodeB sectors depending on the time-varying traffic, in order to resolve unbalanced traffic scenarios.

#One of the primary design challenges for a Virtualized DAS system is location area management. The location area management problem can be generally stated as: For a given network of nDRUs, the objective is to partition the network into m coverage areas, without exceeding the number of users which can be supported by the eNodeBs. To provide the best Quality of Service (QoS) for a given number of eNodeBs and resources, the call traffic must be dynamically balanced when we consider call handoffs and call blockage rates. This is a location management optimization problem that can be accomplished through delivering the sectorized eNodeB traffic to the independent DRUs.