Abstract: Signal, e.g., message, security techniques are described for wireless systems. A first signal is received by an access node via a wireless link. The signal includes a first authenticator that was generated by the transmitting device, e.g., wireless terminal. The access node determines from an attribute of the signal at least some information known to both the access node and transmitting device but which was not transmitted as part of the message content. The determined information was used by the wireless terminal in generating the first authenticator. The access node sends at least a portion of the first signal including the first authenticator and the determined information to another entity. The entity compares the first authenticator to a second authenticator it generates from the determined information and a secure key which it shares with the transmitting device to determine if the first and second authenticators match.

Abstract: Methods and apparatus for performing amplitude and phase imbalance correction operations on in-phase and quadrature phase signal components corresponding to a received signal are described. The imbalance correction operations relay on the use of relatively simple to implement feedback loops. The phase imbalance feedback loop relies on the tendency of transmitted symbols to be distributed uniformly around the origin of the I/Q plane if proper phase balance is present in the processed signal. Phase correction coefficients are generated over time as a function of the negated product of the processed in-phase and quadrature phase signal components. Amplitude correction coefficients are generated over time as a function of the difference in the squared values of the I and Q processed signal components.

Abstract: A mobile communications device initiates a handoff from its current base station (BS) sector network attachment point to a new BS sector. The mobile sends a handoff request over its current wireless link to the current BS sector, which forwards the request to the new BS sector, e.g., via a network link. The new BS sector processes the request assigning dedicated resources, e.g., an identifier and dedicated uplink segments. Information identifying the allocated resources is conveyed from the new BS sector via the current BS sector to the mobile. The mobile determines the time of the allocated dedicated segments based upon a received beacon signal from the new BS sector with known timing relationships to dedicated segments. The mobile breaks the original wireless link just prior to the time of the first assigned dedicated segment. The mobile communicates information on the assigned dedicated segments to perform registration operations, e.g.

Abstract: Transmit and/or receive diversity is achieved using multiple antennas. In some embodiments, a single transmitter chain within a wireless terminal is coupled over time to a plurality of transmit antennas. At any given time, a controllable switching module couples the single transmitter chain to one the plurality of transmit antennas. Over time, the switching module couples the output signals from the single transmitter chain to different transmit antennas. Switching decisions are based upon predetermined information, dwell information, and/or channel condition feedback information. Switching is performed on some dwell and/or channel estimation boundaries. In some OFDM embodiments, each of multiple transmitter chains is coupled respectively to a different transmit antenna. Information to be transmitted is mapped to a plurality of tones. Different subsets of tones are formed for and transmitted through different transmit chain/antenna sets simultaneously.

Abstract: Scheduling of regular signal transmissions, e.g., between a plurality of wireless terminals and a base station in a cellular network in a manner designed to reduce or minimize recurring periodic interference encountered by individual wireless terminals from transmission in neighboring cells is described. Signal transmissions of wireless terminals in each cell are scheduled on a group slot basis. A group slot comprises a number of time slots. Each wireless terminal serviced by a particular base station is assigned a time slot in a group slot used by the particular base station. A given wireless terminal is assigned different time slots in successive group slots as specified by a hopping function. Adjacent, base stations e.g., base stations of physically neighboring or overlapping cells, use distinct, i.e., different, hopping functions for the scheduling purpose thereby avoiding correlation of slots between overlapping or adjacent cells during consecutive group slots.

Abstract: A method and apparatus for joint time and frequency synchronization for orthogonal frequency division multiplexing (OFDM) systems. A multitone pilot signal is sent in a designated OFDM symbol period. The receiver synchronizes to the pilot signal in a two-stage procedure. The first stage estimates the frequency offset coarsely with a frequency-domain correlation method and estimates the time offset with smoothed time-domain correlation. In a multipath channel, the smoothed time offset estimate is used to locate a cyclic prefix interval which captures the maximum total signal energy. The second stage improves the frequency estimate with a computationally efficient numerical optimization method.

Abstract: Methods and apparatus for aggregating IP packets over an access link between a wireless access router and a core node and for managing resource allocation to access link packet aggregates, e.g., as a function of the status of wireless communications links used to couple mobile nodes to the access router are described. Improved aggregate resource control messages and use of such messages are described. Some of the new messages allow aggregate resources for both upstream and downstream aggregates to be controlled in a single message. A single message may include information corresponding to multiple aggregates and/or multiple constituent flows included in an aggregate with aggregate direction information being included. Use of tunnels to communicate management messages, e.g., messages used to control resource allocation to aggregates is also described. Propagation of access link aggregate information is communicated to tunnel end nodes which generate packets that are communicated over the access link.

Abstract: Extending Mobile IP to support both local and remote access by using two MIP client stacks in the end node, a roaming Node in the local access network, a standard Home Agent in the remote network. Messages between the AR and the MN, and between the internal modules of the MN, are then used to control hand-off for each MIP client and to enable backwards compatibility with legacy remote access clients.

Abstract: Location update techniques are described. A dormant mobile node updates its location information by sending a first message over a wireless link to an access node. The access node generates a second update message in response to the first message. The second message includes a mobile node identifier and, in some embodiments is directed to the mobile node. The second message is received by a tracking agent, which updates location information corresponding to the mobile node. In the case where second message is an IP message and is routed to the mobile node using Mobile IP, a Mobile IP home agent routes the second message to the mobile node's last point of network attachment where the tracking agent is located and intercepts the message. The tracking agent may send a response message to the access node sending the second message.

Abstract: A wireless communications system, e.g., an OFDM system, uses a plurality of carrier frequencies each with an associated frequency band. A base station sector transmitter in the system transmits ordinary signaling, e.g., user data, in its own assigned band. In addition the sector base station transmitter periodically transmits beacon signals into its own frequency band and the frequency bands used by adjacent sector transmitters for their ordinary signaling. Beacon signals, being short duration high power signals with sector transmission power concentrated on one or a few tones, are easily detectable. Each beacon signal may be identified as to the source base station sector transmitter, e.g., based on tone. A mobile node, tuned to a single carrier band, receives a plurality of beacon signals, identifies the sources of the received beacons, compares the received strength of the beacons, and makes handoff decisions, without having to switch carrier band.

Abstract: Methods and apparatus for storing, manipulating, retrieving, and forwarding state, e.g., context and other information, used to support communications sessions with one or more end nodes, e.g., mobile devices, are described. Various features are directed to a mobile node controlling the transfer of state from a first access node to a second access node during a handoff operation thereby eliminating any need for state transfer messages to be transmitted between the second access node and the first access node during handoff. Other features of the invention are directed to the use of a core network node to store state information. State information stored in the core node can be accessed and used by access nodes in cases where a mobile node does not send a state transfer message during a handoff, e.g., because communication with the first access node is lost or because such messages are not supported.

Abstract: Receivers accommodating carrier frequency selection methods in wireless communications systems employing multiple carrier frequencies are described. Although the receiver is tuned to a single band, an estimate of the channel quality corresponding to the currently used carrier and an alternative carrier is generated without switching between carriers. Transmitters of different cells and/or different sectors primarily use different carrier frequencies but periodically transmit using a neighboring sector's carrier frequency. Mobile node receivers use a single RF chain with a controllable RF filter to receive and process a signal within a first selected carrier band including two components, a first signal component identified with the first currently selected band and a second signal component identified with a second alternative band.

Abstract: Methods and apparatus for generating and transmitting frequency division multiplexed signals are described. Each transmitted FDM signal is generated by combining, e.g., multiplexing, a plurality of individual analog subcarrier signals together. Individual analog subcarrier signals are generated by processing one or more digital signals, e.g., symbols plus a cyclic prefix for each symbol, corresponding to the subcarrier to generate an analog subcarrier signal there from. A cyclic prefix incorporated into subcarrier signals is designed to be of sufficient length that it covers delays introduced by filters in the individual subcarrier signal paths and common signal path. The incorporated cyclic prefix has a minimum duration determined as a function of several group signal dealys including a common signal path group signal delay and a communications channel group signal delay.

Abstract: A few high power tones used for synchronization and/or other purposes are transmitted in a FDM system during a period of time, e.g., a symbol transmission time period. During normal data transmission symbol periods signals are transmitted using at least 10 tones, e.g., per symbol time. Less than 5 high power signals are transmitted in a symbol time with at least 80% the maximum total transmitter power transmitted being allocated to the high power signals where the maximum total transmitter power is determined from a period of time which may includes one or more data and/or high power tone transmission periods. When the high power tones are transmitted at most 20% of transmitter power is available for transmitting other tones with the power normally being distributed among multiple tones. Normally some tones which would be transmitted in a symbol time go unused during transmission of the high power signals.

Abstract: A mobile communications system that uses IP packets to transmit data between end nodes, such as mobile devices, is described. In order to facilitate session establishment, maintenance, security, and handoff operations, access nodes through which end nodes communicate with one another include a session signaling server module and a mobility agent module. The session signaling server module may be implemented as a SIP server while the mobility agent module may be implemented using Mobil IP signaling. The mobility agent and SIP server within an access node are identified using a single shared identifier, IP address. The same security method and common secret may be used to provide security with regard to both mobile IP messages and SIP messages. Sessions admission decisions and resource allocation for admitted sessions can also take place internally to the access node of this invention without need for signaling to external elements.

Abstract: The use of multiple states of mobile communication device operation to allow a single base station to support a relatively large number of mobile nodes is described. Various states require different amounts of communications resources, e.g., bandwidth and/or control signaling. Different numbers of control channels are monitored during different states of operation. A mobile node monitors during a first state of operation, e.g., the on-state, a first control channel to detect control signals in segments of the first control channel intended for the mobile node, detects a period of reduced control signaling to said mobile node on said first control channel, and then, in response to detecting a period of reduced control signal signaling to the mobile node, transitions from said first state to a second state of operation. During the second state of operation fewer control channels are monitored and the first control channel is not monitored.

Abstract: Methods and apparatus for encoding codewords which are particularly well suited for use with low density parity check (LDPC) codes and long codewords are described. The described methods allow encoding graph structures which are largely comprised of multiple identical copies of a much smaller graph. Copies of the smaller graph are subject to a controlled permutation operation to create the larger graph structure. The same controlled permutations are directly implemented to support bit passing between the replicated copies of the small graph. Bits corresponding to individual copies of the graph are stored in a memory and accessed in sets, one from each copy of the graph, using a SIMD read or write instruction. The graph permutation operation may be implemented by simply reordering bits, e.g., using a cyclic permutation operation, in each set of bits read out of a bit memory so that the bits are passed to processing circuits corresponding to different copies of the small graph.

Abstract: A base station having the strongest downlink signal is identified by utilizing a unique slope of a pilot tone hopping sequence being transmitted by a base station. Specifically, base station identification is realized by determining the slope of the strongest received pilot signal, i.e., the received pilot signal having the maximum energy. In an embodiment of the invention, the pilot tone hopping sequence is based on a Latin Squares sequence. With a Latin Squares based pilot tone hopping sequence, all a mobile user unit needs is to locate the frequency of the pilot tones at one time because the pilot tone locations at subsequent times can be determined from the slope of the Latin Squares pilot tone hopping sequence. The slope and initial frequency shift of the pilot tone hopping sequence with the strongest received power is determined by employing a unique maximum energy detector.

Abstract: Methods and apparatus of the present invention can be used to implement a communications system wherein different devices using the same LDPC code can be implemented using different levels of parallelism. The use of a novel class of LDPC codes makes such differences in parallelism possible. Use of a factorable permuter in various embodiments of the invention make LDPC devices with different levels of parallelism in the encoder and decoder relatively easy to implement when using the codes in the class of LDPC codes discussed herein. The factorable permuter may be implemented as a controllable multi-stage switching devices which performs none, one, or multiple sequential reordering operations on a Z element vector passed between memory and a Z element vector processor, with the switching one individual vectors being controlled in accordance with the graph structure of the code being implemented.

Abstract: Base station identification and downlink synchronization are realized by employing pilots including known symbols transmitted at prescribed frequency tones in individual ones of prescribed time intervals. Specifically, the symbols used in the pilots are uniquely located in a time-frequency grid, where the locations are specified by periodic pilot tone hopping sequences. In a specific embodiment of the invention, a period of a pilot tone hopping sequence is constructed by starting with a Latin-square based hopping sequence, truncating it over time, and possibly offsetting and permuting it over frequency. Particular examples of pilot tone hopping sequences are parallel slope hopping sequences in which the periodicity of the sequences is chosen to be a prime number of symbol time intervals. In another embodiment of the invention, a notion of phantom pilots is employed to facilitate use of various system parameters while accommodating the above noted pilot tone hopping sequences.