Abstract: A plurality of encryption keys is generated, and each encryption key is associated with one geographical area of a plurality of geographical areas. Each encryption key is forwarded to one or more base stations in the geographical area associated with the encryption key. At least one of the plurality of geographical areas that is adjacent to a first geographical area is determined, yielding one or more adjacent geographical areas, and an encryption key for at least one of the one or more adjacent geographical areas is forwarded to at least one base station covering the first geographical area.

Abstract: A home location register stores key material related to mobile stations associated with the home location register. A first visited location register associated with a first site in a first zone stores key material related to a first mobile station of the mobile stations associated with the home location register. When the first mobile station roams to a second site in a second zone associated with a second visited location register, the key material related to the first mobile station is encrypted with an interkey, yielding encrypted key material, wherein the interkey is used only by infrastructure system devices other than a mobile station for encrypting at least the key material for transport between at least the first and second zones. The encrypted key material is forwarded to the second visited location register.

Abstract: A first infrastructure system device other than a mobile station generates key material and forwards the key material to a second infrastructure system device other than a mobile station. A determination is made as to whether a mobile station for which the key material is directed is active on the system, and if so the key material is forwarded to a base station where the mobile station is active. The base station forwards the key material to the mobile station.

Abstract: A first infrastructure system device other than a mobile station generates an encryption key and encrypts the encryption key with a first intrakey associated with a first zone that includes a second infrastructure system device other than a mobile station, yielding a first encrypted encryption key. The first intrakey is used only by infrastructure system devices other than a mobile station for encrypting at least the encryption key prior to transport within the first zone. The first infrastructure system device forwards the first encrypted encryption key to the second infrastructure system device.

Abstract: An apparatus and method for indicating sources of high error conditions, including out-of-range and interference conditions, to a user of a digital voice communication system. When the vocoder (206) of a communication unit (200, 450) silences due to high error conditions, a source of the high error conditions (e.g., out-of-range or interference) is determined based on the signal strength, and a source indicator (218, 220) is generated to inform the user of the source of the high error conditions. In one embodiment, where a repeater (400) is used, sources of high error conditions are detected both inbound to and outbound from the repeater. In an event of high error conditions on the inbound signal path (404), the repeater puts out a distinctive erasure (420, 422, 424) identifying the source. The communication unit (450) detects the erasure and generates a source indicator associated with the erasure.