Abstract: A security node disposed in the telecommunications network connecting calling and called parties transforms information (which can be voice, data, facsimile, video and other types of calls or messages) encrypted in a first format to (a) encrypted information in a different format or to (b) non-encrypted information, and vice-versa. The node is accessible from any location connected to the network. By routing calls or messages originated by the calling party and destined for the called party via the security node, and providing appropriate control signals to the node, the information may be encrypted only over a portion of the transmission path between the parties, and clear over the remainder of the transmission path. Alternatively, the information may be encrypted in different portions of the path using different encryption algorithms.

Abstract: A method of transmitting signals from a mobile unit to a base station in the reverse link direction using multi-tone techniques includes the step of dividing a frequency band into a plurality of generally even spaced tones. The tones are partitioned into a predetermined number of tone sets which each contain a predetermined number of tones. Each unit within a given sector is assigned a tone set for transmitting information signals. The tones within each tone set are selected so that the modulated signals transmitted by each unit are orthogonal with respect to all other tone sets assigned to units in that sector. Adjacent cells have no more than one tone in common.

Abstract: Encoded blocks of video information are selected for transmission at a plurality of channel rates based on the corresponding location of the portions of the video image represented by the encoded blocks. Each encoded block is designated an image type which determines its transmitted channel rate. The image types are associated with spatial positions of a video image such that encoded blocks within a first area of the video image are designated a first image type and encoded blocks within a second area of the image are designated a second image type. In general, data blocks representing the central portion of the video image are transmitted at a channel rate having less susceptibility to noise or other degradation, thereby ensuring that such portion can be received in fringe areas.