Abstract: A communications system (20) and method (100) learns and dynamically selects routes among a number of nodes (1-12) based on network state information. Each of the nodes (1-12) monitors its links and determines the state of each of its link. Each of the nodes (1-11) transmits their respective link state information to a designated node called a center node (12) by using forward propagation. After the link state information has been received from all of the nodes (1-11), the center node (12) aggregates them and forms a comprehensive state of the entire network. This network state information is subsequently distributed by the center node (12) to each of the nodes (1-11) in the network using reverse propagation. Each of the node (1-11) uses the network state information in making route selection decisions for connection requests that arrive after the node updates its network state information.

Abstract: A communications network (20) includes any number of moving switching nodes (30) and a route-determining node (28). The route-determining node (28) performs an off-line procedure (58) to define a-priori routing for the entire network. This procedure (58) is performed repetitively to track switching node (30) movement and to define routing for numerous epochs included in a planning period. The procedure (58) includes a process (86) for determining all shortest path routes between all possible origination and destination switching nodes (30). Another process (84) matches predicted call traffic for a subject epoch with the shortest path routes. Another process (88) generates routing code tables (54) in response to the predicted call traffic matched to shortest path routes. This process (88) assigns logical routing IDs (52) to physically distinct, shortest path routes in proportion to the predicted call traffic allocated to the distinct routes.

Abstract: A communications network (20) includes a constellation (30) of any number of moving switching nodes and a route-determining node (28). The route-determining node (28) performs an off-line procedure (58) to define a-priori routing for the entire network for a planning period. When a link (40) fails, the switching nodes (30) terminating the link (40) implement an interim rerouting procedure (78). The route-determining node (28) then operates in a failure response mode to quickly devise updated routing definitions. In the failure response mode route trees (110) which include the failed link (40') are identified. Shortest path routes for nodes (30) isolated by the link failure are revised to omit the failed link (40'). Shortest path routes for non-isolated nodes (30) and in route trees which do not include the failed link are not changed.

Abstract: A cellular communication system projects multiple cells throughout a user area. Subscriber units (24) encounter multiple cells as they roam through the user area or as the cells migrate past the subscriber unit (24). When a subscriber unit (24) encounters the fringe area of a cell it maintains contact with the system by selecting and transitioning to a target cell. The subscriber unit (24) performs an analysis using Doppler data of the location, proximity, and expected duration of exposure to candidate target cells. The subscriber unit (24) selects a target cell based on these factors.

Abstract: A cellular communication system projects multiple cells throughout a user area. Subscriber units (24) encounter multiple cells as they roam through the user area or as the cells migrate past the subscriber unit (24). When a subscriber unit (24) encounters the fringe area of a cell it must select and transition to a target cell to maintain contact with the system. The subscriber unit (24) performs an analysis of the location, proximity, and expected duration of exposure of candidate target cells using location data transmitted by control channels located in the candidate cells. The subscriber unit (24) then selects a target cell based on these factors.

Abstract: An apparatus and method for adaptive route selection between a source and a destination node where multiple routes are available. Link state variables are monitored and updated when call termination requests or call arrival requests are received. When a call arrival request is received, a list of potential routes between the source and destination nodes is determined. A best route is selected by evaluating the link states for each potential route. A call is attempted on the best route and if the attempt is not successful, a call is attempted using the next best route and so on.

Abstract: Methods for handoff in a wireless communication network including a local area network connected to a plurality of base stations, each of which has a geographic area, defined as a cell, within which mobile stations can communicate with a base station, with each such base station being capable of performing bidirectional wireless communication with one or more of said mobile stations under control of a controller, with communication between base stations and mobile stations being performed by frequency hopping, with there being n available frequency hopping channels in a fixed frequency band, with each channel being of a same fixed duration and having a fixed frequency different than another channel.

Abstract: A method for use in multicellular communication network system of the type having base stations and a plurality of remote stations. The method achieves reliable and fault tolerant synchronization between the stations in a call when a frequency hopping technique is used. The method includes steps for acquiring the frequency hop sequence by remote station and tracking the frequency hop sequence after acquisition in order to stay in synchronism. The method also provides for recovering from loss of synchronism and for staying in synchronism.

Abstract: A control system for automated management of frequency-hopping in a radio network. The system includes a Wireless Network Manager (WNM) or Controller and a Wireless Control Agent (WCA), which control the distribution and maintenance of hopping patterns in the radio network. In a single cell network, the WNM and the WCA are included in a single base station. In a multiple cell network, the WNM is in a specific station on a LAN, and a WCA is located in each base station on the LAN. In each instance, the WNM is a centralized managing station and the WCA acts as a cell controller.

Abstract: A Medium Access (MAC) Protocol is utilized for wireless radio access for a plurality of remote stations to a base station on a LAN. There is a time division fixed frame structure in which time is slotted, and time slots are grouped into fixed frames consisting of data and control subframes or periods. The fixed frame structure consists of three periods (A, B, and C) along with their respective headers. The first period, the A period, is used exclusively for data transfer from the base station to the remote stations. The following period, the B period, is used for contention-free data transfer from the remote stations to the base station. The allocation of the data slots in the A and B periods is performed by the base station. The last period of the frame, designated as the C period, is used for the transmission of reservation requests and data from the remote stations to the base station in a random-access contention mode using a slotted Aloha protocol.

Abstract: A method for communicating information bidirectionally between a wired network (1) and a wireless network. The wireless network is of the type that includes header stations (12) each having a communication cell (2) associated therewith and one or more mobile communication units (10) disposed within the communication cell. The method includes a first step of, during a first portion of a wireless communication cycle, transmitting information over an uplink wireless communication channel from one or more of the mobile communication units to the header station. A second step of the method, accomplished during a second portion of the wireless communication cycle, transmits information over a downlink wireless communication channel from the header station to one or more of the mobile communication units. The information transmitted downlink includes frames of data received by the header station from the wired network.

Abstract: Method and apparatus for improving an efficiency of solution of constraint-satisfaction type problems performed with a digital computer. A method includes the steps of creating a data structure having storage allocated for a plurality of entries, each of the entries having a plurality of attribute fields, including a Binding.sub.-- set attribute, a Potential.sub.-- savings attribute and an Accumulated.sub.-- savings attribute. The method further includes a step of inserting entries into the data structure in response to an occurrence of a failure path identified during a backtrack search of a search tree structure. The method also includes a step of examining the entries of the data structure during a backtrack search in order to avoid paths of the tree structure that are repetitively identified to be failure paths.

Abstract: A method and apparatus for conserving battery power in a wireless link adapter of a battery operated computer such as a portable laptop computer, as controlled by a scheduled multiaccess protocol. The portable computer is operable as a mobile unit in a multi-cell wireless network. The scheduled access multiaccess protocol is implemented to effectively conserve battery power by suitable control of the state of the controller, the transmitter and receiver units at the wireless link adapter by scheduling when the adapter is in a normal running mode, or a standby mode in which power is conserved.

Abstract: A method includes a first step of receiving a message from a wired network (1) with at least one header station (12). The message is a message type that authorizes a header station or header stations to transmit on a wireless network. A second step of the method is accomplished in response to the received first message, and initiates wireless communications with any mobile communication units (10) that are located within a communication cell served by the at least one header station. In one embodiment the message circulates around a token ring and activates header stations in turn. In another embodiment disjoint groups of header stations are predetermined by graphical techniques, including graph coloring methods. The predetermined group information is maintained by a network controller that thereafter selectively activates the header stations within the different groups.

Abstract: A method of solving a constraint-satisfaction problem with a data processor includes the steps of (a) providing a search tree structure (10) representing a plurality (N) of variables (X), the search tree structure having a plurality of levels; (b) searching (L) shallow levels of the search tree structure by employing a backtrack search method wherein (L) is less than or equal to a specified value H; and (c) searching (M) remaining, deeper, levels of the search tree structure by employing a lookahead search method. The step of searching (L) shallow levels of the search tree structure includes a step of binding a set of X.sub.1 through X.sub.H variables each to an element from its domain such that no constraints are violated. The step of searching (M) remaining, deeper, levels of the search tree structure includes the steps of, given the bindings for the set of variables X.sub.1 through X.sub.H, determining for each variable X.sub.i, H<i.ltoreq.

Abstract: In a wireless communications network having a plurality of header stations (12) in bidirectional wireless communication with one or more mobile communication units (10), a method of managing ownership of the mobile units. In accordance with the method the following steps are executed. A first step receives, with a mobile communication unit located at a position (44) that is served by two or more of the header stations, a transmission from each of the header stations. The received transmissions are received over the wireless communications network and each uniquely identify the transmitting header station. The method further includes a step of selecting, with the mobile communication unit, one of the header stations as a header station to manage future wireless communications for the mobile communications unit. A further step is performed if the selected header station is not a header station that is presently managing wireless communications for the mobile communications unit.

Abstract: A wireless communications network includes a local area network connected to a plurality of nodes which perform bidirectional wireless communication with mobile stations as controlled by a controller. Each node has a geographic area, termed a cell, within which mobile stations can communicate with the node associated with the cell. A cell interference graph is read into the controller, and a maximal independent set of nodes is determined. Each node in the maximal independent set of nodes is put in a set termed ACTIVE for performing wireless communication with mobile stations in their respective cells. Nodes which are not in the maximal independent set of nodes is put in a set termed WAITING to wait for permission to enter the set ACTIVE. A node in the set ACTIVE which has completed communications sends a completion signal to the controller.

Abstract: Apparatus and method for minimizing, in a multiprocessor system, a variance in a search effort along different subtrees of a backtrack search tree employed for solving an instance of a constraint-satisfaction problem. A method includes the steps of (a) estimating an amount of search effort required for different subtrees of the search tree, (b) allocating an appropriate number of processors to each of the different subtrees of the search tree based upon the estimated amount of search effort, the number of processor allocated to each of the subtrees being selected to minimize a variance in search processing time along the different subtrees, and (c) executing the search with the allocated processors in parallel along the different subtrees of the search tree.

Abstract: A system for the adaptive reordering of sequential decisions in the search of a data base is provided with a device that simplifies and speeds up a heuristic search method by implementing in hardware the computation required for the adaptive reordering. The system includes an arithmetic unit for computing for each decision the ratio p/c where p is the probability of a successful outcome of the decision and c is the cost of computation to make that decision. The arithmetic unit includes a device for estimating the logarithms of the prabability p and the cost c for each decision. Logarithms of ratios p/c are calculated for each decision by subtracting the log c from the log p, and then the logarithms of the ratios for the decisions are compared to produce a priority value for each decision. The decisions are reordered based on the priority value assigned to each decision to obtain the optimal ordering of the decisions.

Abstract: An adaptive mechanism is presented in the context of optimization of expert system applications. Both single and multiple processor implementations are disclosed. The mechanism is used to maintain a near-optimal sequence for scanning rule lists in expert systems. For a program containing a sequential-decision chain with many independent or mutually exclusive outcomes with each decision having associated with it some fixed cost and probability, the adaptive mechanism tends to produce the optimal ordering automatically from repeated observations of the execution of the decision chain.