tailieunhanh - Enabling Technologies for Wireless E-Business phần 8

Cuối cùng, sau một thời gian của sự tiến hóa được kiểm soát bởi thông tin phản hồi tích cực, toàn bộ hệ thống sẽ đạt được một trạng thái cân bằng tương ứng với các giải pháp tối ưu mong muốn. Trong mô hình này, thay đổi giá trị tập thể dục đại lý thể hiện hành vi tự thích ứng của họ như những thực thể duy nhất, trong khi các hệ thống thông tin phản hồi tích cực là hiện thân của hành vi selforganized nhiều đại lý | 266 Y. Yang and R. Yan Architecture MMS is an application-level service that fits into the current WAP architecture. The basic concept of sending an MMS message is exactly the same as that of SMS. The originator addresses the receiver the message is first sent to the MMS center MMSC associated with that receiver then the MMSC informs the receiver and attempts to forward the message to the receiver. If the receiver is unreachable MMSC stores the message for some time and if possible delivers the message later. If the message cannot be delivered within a certain time frame it is eventually discarded. In fact it is a much more complicated process. To enable this service a set of network elements is organized as shown in Fig. 14 . The whole MMS environment MMSE encompasses all necessary service elements for delivery storage and notification. The elements can be located within one network or across several networks or network types. In the case of roaming the visited network is considered a part of that user s MMSE. However subscribers to another service provider are considered to be a part of a separate MMSE. The MMS relay and MMS server may be a single logical element or may be separate. These can be distributed across different domains. The combination of the MMS relay server is the MMSC. It is in charge of storing and handling 11 Mobile Content Delivery Technologies 267 incoming outgoing messages and is responsible for the transfer of messages among different messaging systems. It should be able to generate charging data for MMS and VAS provider-related operations. MMS user database contains user-related information such as subscription and configuration. MMS user agent is an application layer function that provides the users with the ability to view compose and handle multimedia messages. It resides on the user equipment UE or on an external device connected to the UE or MS. MMS VAS applications provide VAS to MMS users. They can be seen as fixed MMS .