Abstract: A digital radio communications system is presented in which the deleterious effects of fading, time dispersion and interference found in the channel are mitigated by using interference rejection and diversity combining. Digital signals representative of digital symbol sequences are transmitted through a radio channel in which the signals may be corrupted by fading, time dispersion and interference. The corrupted signals are received by a receiver having one or more antennas. The received signals are processed to form a received signal sample stream r.sub.d (kT.sub.s) for each of the antennas. Estimated received signal samples for each of the antennas are produced by combining hypothesized signal sequences and models of each channel. The received signal samples and the estimated received signal samples are processed in conjunction with an estimate of the impairment correlation properties to produce branch metrics to be used by a Viterbi, or other sequence estimation, algorithm.

Abstract: A method and apparatus is presented for transforming a key variable used for scrambling cellular data traffic between a terminal and a network in alternate ways using information transmitted to the terminal from the network with which the terminal is connected. Transformation is accomplished by passing portions of the key variable through a series of S-boxes which provide a mapping between the input and output. Moreover, it is disclosed how to save memory by iteratively passing portions of the key variable through the same S-box.

Abstract: A method and apparatus is provided for extending the battery life of a cellular radiotelephone. A cellular radiotelephone is conditioned to operate in a pager-only mode wherein the radiotelephone may receive short messages from a base station while conserving battery life by cyclically adopting a deep-sleep state. The base station is notified by the radiotelephone before the radiotelephone enters the deep-sleep state that the radiotelephone is unable to receive messages. After a period of time, the radiotelephone wakes-up, re-establishes contact with the base station and notifies the base station that the radiotelephone is ready to receive messages. After receipt of any messages the radiotelephone repeats the process.

Abstract: In a ciphered digital cellular communications system a method and apparatus are presented for selective resynchronization of the cipher upon initial channel acquisition or handoff. Where synchronization between the old channel and the new channel exists, the base station indicates along with an ITCD or handover message that no resynchronization is required. Where synchronization between the old channel and the new channel does not exist, the base station provides an indication along with an ITCD or handover message that resynchronization is required and from the content of this message the manner in which resynchronization is to be achieved is further indicated. By providing options for resynchronization security may be optimized or compromised for handover speed depending upon the specific requirements of the base station or the mobile station.

Abstract: Signals in synchronizing sequences and data sequences are transmitted over a fading channel to a sequence estimation receiver. The signals are received by a plurality of mutually separated antennas and sampled to produce received antenna signals (S.sub.in,r (k)). Using the received antenna signals, part transmission channel estimates (h.sub.est,r) are formed for each antenna. These part channel estimates are used to form precomputed metric values (f.sub.a,r ((.DELTA.T.sub.ij),g.sub.a (.DELTA.T.sub.ij)). For the sequence estimation algorithm, branch metric values (m(.DELTA.T.sub.ij,k)) are formed by combining the precomputed metric values with the received antenna signals for state transitions (.DELTA.T.sub.ij). For one state transition there is formed a metric value such as the sum of a metric value (M(T.sub.j,k-1)) for an old state (T.sub.j) at a preceeding sampling time point (k-1) with a branch metric value (m(.DELTA.T.sub.ij,k)).