Thinking of Home Gateway

Fixed network operators are facing a continuous decrease of their revenues from voice services, so they are urged to develop other services to make up such a decrease. However, there are two factors that have placed the fixed network operators in a dilemma. On one hand, it is difficult to further develop terminal technologies for the fixed networks, so the terminals have restricted the development of new services. On the other hand, the personalization and mobility of mobile services that meet more demands have given fixed services a heavy shock.

    Facing the dilemma mentioned above, the fixed network operators are actively looking for effective solutions. Home networks, as an important solution, are attracting more and more attention. The terminal and service development of the home networks and their service provision will change the operation models of the fixed network operators. The existing voice-dominated operation will be changed into the nonvoice-dominated operation, and the  network provision into the service provision.

    Home gateways play a core role in home networks. At present, the available home gateway products are some kind of integrated network access equipment. Therefore, they emphasize multiple access and equipment interconnection. This paper discuss the positioning and functionality of the home gateways in the future from the point of view of network convergence.

1 Functions of Home Gateway
At present time, there are no unified standards for home gateways. Now many products such as Integrated Access Device (IAD), Asymmetric Digital Subscriber Line (ADSL) products and Set-top Box in the market are called home gateway products. There are different understandings of the home gateway in the industry. The author thinks that the home gateway should be positioned as a pivotal part to connect homes and access networks, and operators can provide various access services and telecom services through it to the homes.

    The home gateway should have the following functions:
(1) Basic Functions
    As a bridge to connect the external networks and the home networks, the home gateway should support multiple access to various networks, even to the networks from different operators. At the same time, it should provide QoS control capability to guarantee QoS of the home networks. These are the basic functions of the home gateway.

    People often stay at homes and offices, where network users request little mobility. Therefore, the external access of the home gateway should be with the wires, while its internal access is through the wireless network such as Wi-Fi, the bluetooth and Ultra Wide Band (UWB) in the future. With such an access model, terminals of a home network are mainly integrated with the wireless technologies such as Wi-Fi and bluetooth. They access networks through the gateway when at home, and their external access is implemented through the mobile networks. This is the development trend of the terminals of the home networks.

 (2) Service Platform
    The home gateway is requested to be an open service platform in order to support users to obtain available services through it. It should adopt standard interfaces to implement service management, service control and service download, as well as to converge and coordinate different services. Service coordination and service convergence are interrelated. For example, a Wi-Fi integrated terminal should be able to change its service access mode into access through Wi-Fi and the home gateway when its user arrives at home, and this handover should be seamlessly implemented.

(3) Management Capability of Operator
    Functionality of a home gateway will become more and more complex, so it is obviously unrealistic to let home users manage the home gateway. Its management should be done by operators. The home gateway can provide related interfaces to implement operator’s management such as configuration management and trouble-shooting management, while the management of home users is only simple management of items related to users’ privacy (such as their passwords).

(4) Security Function
    As an interface with external networks, the home gateway must be ensured safe. This security should be implemented on all levels. For the aspect of information protection, the home gateway should have a firewall; for service security, it should implement protection and security of various services, such as network access restriction. A home gateway can even implement Virtual Private Network (VPN), supporting multiple VPNs between homes or home and office.

    With the above discussion, we can find that the home gateway has comprehensive functions. However, currently available products are still with simple functions. The home gateway should be developed step by step, gradually implementing the above-mentioned functions. Basic physic access functions can be implemented first, followed by the gradual introduction of various telecom services. Management functions can be simple first and comprehensive later, to fit the home gateway for future network development.

2 Home Gateway Under  Circumstance of Network  Convergence
The Next Generation Network (NGN) should be an integrated network, converging various networks such as PSTN and IP. The home gateway should be regarded as part of NGN. From the aspect of network convergence, the home network should be a converged network, which is the NGN@HOME concept of ETSI.
The home gateway under the circumstance of network convergence is positioned as shown in Figure 1.

    In Figure1, the multi-service platform implements such functions as user data, authentication, billing and service management. It has open service interfaces (like the Parlay interface), and can support service customization. The unified service platform truly implements integration of services for homes and individuals. The home gateway is located at the last section of a system that offers telecom services to users. It has access capability to the service platform, cooperating with background service platforms to implement the introduction of services at home.

2.1 Service Platform Implementation of Home Gateway
The home gateway is developing with intelligence and the service platform, which is in accordance with the network intelligence trend toward edge networks. Now home services include two types. One is traditional telecom services such as phone calls, faxes and value-added services. These services are offered by such systems as switching networks, intelligent networks and Softswitch systems. The other is data services like Internet access and stream media, which is implemented through special application servers. Besides access interfaces, the home gateway should provide home service interfaces, acting as a service gateway. With this service platform, home users can enjoy diversified telecom services, while operators offer and manage home services. The home gateway should be able to support the above-mentioned two service types.

    At present, the industry has no idea about how to implement the service platform at the home gateway yet. Figure 2 illustrates a service platform of the home gateway that is based on the Open Service Gateway Initiative (OSGi) technologies[1]. The sevice platform divides the home gateway into a few layers. The service capabilities of equipment are abstracted as resources first, such as bandwidth and interfaces, and then information of the resources like their locations and users are managed. Based on the resource management, services are generated. The top layer is responsible for service management. The OSGi-based home gateway adopts open interfaces, which allow operators to develop services there and then download and locally execute the services. This can fit in with changeable service models.

    OSGi has wide application, so the industry is thinking of applying OSGi into the home networks, along with more and more attention to home networks and home gateways. Several OSGi-based home network products have launched. Technically speaking, OSGi-based home gateway products are feasible. However, the original object of OSGi definition was not the home network product, so it considered little about home services that are a key part of the home gateway. Fortunately, OSGi is being improved, and expected to be more and more suitable for usability of the home gateway.

2.2 Network Management Functions
The author thinks that operators should manage the home gateway, because it is impossible for users to maintain the home gateway with comprehensive functions. Therefore, home gateways, just like the fittings boxes of cable TV, are put at house entries and managed by operators. In this way, the service of operators is extended from residential areas or local offices to home. The home gateway is capable to keep online, to implement online services such as online ads, and even to record the reading of home meters.

    A home gateway should have the following management functions:
(1) Configuration Management 
    A home gateway should be able to obtain configuration information of the service platform of an operator, at the same time, it should also be able to download new customized services upon requests. Different home users have different configuration and requirements. The users may change their configuration at the home gateway, and the home gateway will automatically implement the configuration changes according to the users’ demands.

(2) Trouble-shooting Management
    With trouble-shooting management functionality, the home gateway can support such functions as remote diagnosis and trouble declaration.

(3) Billing Management
    Integrating multiple services of a home user, the home gateway should offer a unified billing function, hiding billing differences of external networks and providing a unified service-based charge model.

(4) Performance and User Management
    The home gateway should have performance management functions like display of bandwidth and traffic volume. Besides, it should support different access settings for different home users, such as access restriction for children.
Technically, the above-mentioned management functions can be implemented. According to practical demands of operators, trouble-shooting management and billing management are basic requirements. As for the configuration function, fixed configuration can be adopted first, and the function does not work until a good service platform system is set up. Besides, the performance and user management can be regarded as additional services of the home gateway. Operators are responsible for most management functions, while users for the left few, like user password management and websites visit restriction.

2.3 Implementation of Private Communication and  Private Number
In fact, mobile communication is bound together with individuals. Each SIM card only belongs to one subscriber. A person’s services have mobility with the move of mobile terminals, so mobile communication is a kind of private communication. However, this has not been implemented on fixed networks yet. For fixed networks, number is bound to the terminal, so do services. Is it possible for the home network and home gateway to implement private number function and mobility of personal services? Here the author makes an assumption.

    In order to implement the mentioned functions, it is necessary to use mobile communication system as a reference. First, a unique identification number is needed, which can be kept in something like the SIM card that has a standard interface with the terminal or can be fixed in the terminal. A terminal at home connects to networks through the home gateway, while it uses local gateways to access networks when it moves to offices or hotels. It is necessary for the service system to implement number mapping between home and visit locations to support such functions. This service system can be implemented either on the background service platform or at the home gateway. The former implementation is fit for roaming in a large scope, and the latter can be used in small-area roaming such as roaming in a Metropolitan Area Network (MAN).

    IPv6 can be used to implement terminal mobility. Each terminal has a unique IPv6 address as its identification, and this address is just the equipment number of this terminal. The mobility of the terminal can be implemented with the mobility feature of IPv6. When the terminal moves to other networks, it obtains information of visited networks by visiting its home agent. The home agent will transfer its communication to the visited networks, which is a feature of IPv6 and easy to implement.

3 Conclusions
The home gateway is a core part of future home networks. However, there still exist many problems, and the industry has no clear picture about it. The function positioning of the home gateway must be combined with the development of NGN and convergence of fixed and mobile networks. Current home network and gateway products are just primary products. With the development of NGN, the home network and home gateway are expected to grow mature.

Reference
[1] Fujii N. Home Network Service Aggregation Platform and Service Collaborations[Z]. Tokyo: ITU-T Workshop on Home Networking and Home Services，2004.

Manuscript received: 2005-02-16