vấn đề đầu cuối ẩn • Vectors phân bổ mạng (NAV) để nhận ra ý nghĩa nhà cung cấp dịch vụ ảo trong các giao thức truy cập ngẫu nhiên khác, thời gian backoff ngẫu nhiên trong CSMA / CA làm việc để tránh va chạm giữa truyền đi từ Stas khác nhau. Thời gian backoff ngẫu nhiên có thể được tính từ phương trình này: | 182 APPLICATION PLATFORMS FOR NEXT-GENERATION MOBILE NETWORKS the third-party service provider in some scenarios. For example if the buddy-alert application is part of an on-line chat application that supports seamless chatting as buddies move the third-party service provider can use the open API to access location information available at the IP level such as from mobile IP or SIP messages. By bypassing the high-level middleware API the third-party service provider can improve the accuracy of location information but at the same time will need to process more protocol details. Furthermore even though the API at the core network level might provide a certain level of abstraction for underlying access networks because of the heterogeneity of the next-generation access systems APIs at the access network level might be useful for developing location-aware adaptation schemes such as adaptive codecs for different access network bandwidths. No matter what level of API is used the third-party service provider must pass security checks of the network operator before it can access the functionalities supported by the network. In the deployment here the security check is handled by an operator application gateway that separates the trusted network operator s domain from the untrusted outside network domain. In any case part of the user data or business logic might be deployed within the operator s domain in a secure and controllable manner. In the deployment here location services are provided by a Location Server offered by the operator accessed via the operator s application gateway through a closed API. The collected location information is then parsed and provided to third-party service provider via a chosen open API. To collect buddy location information the Location Service uses an internal closed API to contact servers at different access networks. If some buddy is outside of the operator s network the Location Service can use a third-party open API to interact with .
