A method and apparatus are disclosed for assessing the available resources in a network and using the assessment for admission control. A VoIP call can be established with a device only if the network has sufficient resources to accommodate the call or it is possible to make such resources available by curtailing ongoing data connections. A network utilization characteristic (NUC) provides a measure of network capacity. The network utilization characteristic of a flow is the fraction of time the network is busy transmitting data for that flow. The sum of the network utilization characteristics of all flows yields the fraction of time the network is busy transmitting data. The difference between one and the sum of all flows indicates the time that the network is idle in the measured time interval. A new flow can be accommodated if the NUC of the new flow is smaller than this difference value.
A wireless local area network (LAN), and a method of operating the same, prevents unauthorized users from accessing the wireless LAN. A signal strength of a station attempting to access the wireless LAN is measured. If the signal strength is less than a predetermined threshold value, the system concludes that the station is outside of an authorized geographical area. Such a station attempting to establish a connection is characterized as an unauthorized station, and access to the wireless LAN is denied. The system may also periodically verify that authorized stations remain within the authorized geographical area. A station that has moved outside of the authorized geographical area can be notified or denied further access to the wireless LAN.
This invention relates to an information processing apparatus, an information processing method, a recording medium, and a program for transmitting an RTS frame at full power and data at low power. If it is ascertained that data is to be transmitted, an RTS frame is transmitted at full power. If a CTS frame enabling data transmission is not received, a determination is made as to whether a CTS frame is received with its RA field carrying the address of another terminal. If the latter CTS is found to have been received, a transmission-prohibited interval is set and counted based on a duration field in the CTS frame. If the CTS frame enabling data transmission is found to have been received, a reception level of the frame is measured and stored. Data is transmitted by a PDA at lower power. An ACK frame is received. This invention applies illustratively to PDAs.
