For many countries in the world, 5G is of strategic significance. In the 5G era, telecom operators are expected to enable and provide multiple services with different communication characteristics like enhanced broadband, ultra-reliable and extreme real-time communications at the same time. To meet the requirements, the 5G network essentially will be more complex compared with traditional 3G/4G networks. The unique characteristics of 5G resulted from new technologies bring a lot of opportunities as well as significant challenges. In this paper we first introduce 5G vision and check the global status. And then we illustrate the 5G technical essentials and point out the new opportunities that 5G will bring to us. We also highlight the coming challenges and share our 5G experience and solutions toward 5G vision in many aspects, including network, management and business.

We present a design of knowledge circulation framework for quality of service (QoS) control of multimedia communication service (MCS). This framework aims to realizing user oriented and resource aware MCS by enabling effective placement of QoS control knowledge on the network. In this paper, we propose a conceptual design of the framework with knowledge-based multiagent system. In this framework, QoS control knowledge is actively circulated by getting on the agents. We implement a prototype of real-time bidirectional MCS (videoconference system) using this framework, and show initial experiment results using it to evaluate the effectiveness of the framework.

Personal communication service (PCS) networks support the delivery of communication services as the mobile user moves from one region to another. When a mobile user receives a call, the network has to quickly determine its current location. The existing approach suffers from high delay in locating the mobile since the mobile's current location has to be always consulted on the location databases. Caching the location of the remote mobile is useful to reduce this delay. However, the longer the useless record caused by the movement of the mobile remains in a cache, the higher the degradation of cache memory utilization is imposed on a system. In this paper, we propose an efficient caching scheme that a cached record is not allowed to remain over the predefined time, called a time-threshold, in a cache. A long time-threshold may cause to increase the obsoleteness of the cached record. In contrast, a short time-threshold may cause to degrade memory utilization. This paper finds the optimal time-threshold to enlarge cache memory utilization. Also, we provide a unique solution for determining the optimal time-threshold, and study the effects of changing the important parameters of mobility, calling patterns, and network conditions on the optimal time-threshold. Furthermore, we compare the performance of the proposed caching call delivery scheme and the existing call delivery schemes.

An improved movement-based registration scheme reduces location update cost on conventional movement-based location update scheme but increases uncertainty of the position of a mobile terminal (MT). The effect of this uncertainty of the MT position on the paging cost of the improved movement-based registration scheme is analyzed. We show that the paging cost of the improved movement-based registration scheme in [2] is underestimated, especially for large values of movement threshold. The result shows that the underestimation cannot be ignored.

In this paper, we propose a new location tracking method for pointer forwarding with distributed HLRs schemes to decrease the location tracking cost. Similar to the distributed HLR schemes, the location information is replicated on all HLRs in our scheme. However, unlike the traditional distributed HLR schemes, we propagate the most recent location changes from an HLR to reset the forwarding pointers in other HLRs, and thus reduce the cost of location tracking for call deliveries. The signaling cost of location propagation may be too costly to be practical. Therefore, we allow some inconsistency to exist among the location data of HLRs and defer the propagation of location changes to reduce the propagation cost. Three delay propagation policies are also proposed and analyzed using simulation. The performance result shows that the delay propagation policies reduce the propagation cost and the propagation resetting process degrades the location tracking cost. Our method preserves a low total cost for call deliveries, registrations and propagations in distributed HLRs.

Feature interaction detection determines whether interactions occur or not between the new and existing telecommunication services. Most of conventional detection methods on state transition model utilize an exhaustive search. The exhaustive search is fundamentally very powerful in the sense that all interactions are exactly detected. However, it may suffer from the state explosion problem due to the exponential growth of the number of states in the model when the number of users and the number of features increase. In order to cope with this problem, we propose a new detection method using a state reduction technique. By means of a symmetric relation, called permutation symmetry, we succeed in reducing the size of the model while preserving the necessary information for the interaction detection. Experimental evaluation shows that, for practical interaction detection with three users, the proposed method achieves about 80% reduction in space and time, and is more scalable than the conventional ones especially for the increase of the number of users in the service.

Despite the fact that the necessity of FDT (formal description techniques) had been emphasized, many approaches to verifying feature interactions were insufficient. This paper proposes formal definitions for feature interactions which can occur when telecommunication services specified independently are operated in parallel. Seven types of feature interactions are defined formally.

This paper proposes a requirement description and elicitation approach for communication services. Requirements are described in natural language, refined with a knowledge base, and converted to a formal language for program generation. A model for communication services is made as a set of three items: terminal state, terminal action and the response of the communication system to the action. This set, in turn, corresponds to natural language syntax that expresses two conditions (terminal state and action) and their result. These conditions and result are expressed as a sequence of simple sentences that describe the relationship between a terminal and a communication system. Thus, by defining such a description style to reflect the features of communication services, it should be possible to achieve both a high level of description and mechanical processing capabilities at the same time. However, requirement descriptions usually include omission and inconsistency. This problem cannot be solved by merely introducing natural language for the descriptions. Knowledge about the target domain of requirements is needed to resolve it. This paper reports on a knowledge base that stores constraints existing between conditions and results in communication services. This knowledge base is shown to be effective in supplementing omissions and resolving inconsistency. This paper also presents a technique for converting the elicited requirements in natural language to descriptions in a formal language that can be used to generate a program.

A conflict detection support method for combining additional telecommunication services with existing services is proposed. In this method, telecommunication services are described by the STR (State Transition Rule) method which specifies a set of state transition rules. Though conflict detection in the past depended on manual analysis by the designer, with this method, conflict candidates are mechanically narrowed down and indicated to the designer. All conflicts between five actual telecommunication service descriptions are detected in an experiment using a system developed in line with the proposed method.

Telecommunication services are accomplished by cooperative networks of widely distributed communication processes and service users. Those specifications are often modeled by a set of possible message sequences among cooperating processes and users. The distributed and cooperative nature of telecommunication services results in a wide variety of message sequences and makes it more difficult for service designers to design such telecommunication services. To mitigate the difficulty, we propose a design support system with MSRs (message sequence rules) as design knowledge. The system supports the following two design activities: (1) specification of a typical message sequence that corresponds to a service behavior in a successful case, and (2) specification of incidentally possible message sequences that involve service behaviors in successful and unsuccessful cases. For the former activity, the system interacts with designers and identifies the messages they give with MSRs to understand the context of the message sequence and suggest possible subsequent messages. For the latter activity, the system applies MSRs to the typical message sequence and reasons possible messages from/to relevant processes and users under every state to suggest incidentally possible message sequences. Accordingly, designers may be relieved of investigating a wide variety of service behaviors in successful and unsuccessful cases. The system capability is based on MSRs equivalent to reusable message sequence components. MSRs can be obtained through abstraction of implementation-dependent messages and decomposition of those sequences into temporal relations among messages. The rule acquisition method provides MSRs with the potential to generate a wide variety of message sequences. In order to verify rule applicability, we have experimentally designed three kinds of services and conducted an experimental rule application to those specifications. The experimental evaluation results indicate that applicability is fairly high.