Abstract: A method is provided for MIMO uplink communications between a base station and a wireless station with more than two antennae. The method includes: (a) negotiating between the base station and the wireless station uplink MIMO/cooperative MIMO capabilities, using a message exchange protocol in which a message exchanged comprises a field for specifying uplink MIMO/cooperative MIMO capabilities; (b) the base station receiving a request from the wireless station for data transmission; (c) the base station sending the wireless station an allocated resource and an uplink MIMO/cooperative MIMO method for uplink transmission; (e) the wireless station mapping data symbols to the allocated resource with proper pilot pattern; and (f) the base station detecting the data symbols from the channel.

Abstract: In a system including one or more femtocells within a service area of a macrocell, a method includes: (a) receiving from a base station of each femtocell information regarding available resources at the femtocell; (b) measuring an signal-interference-to-noise ratio (SINR) at a mobile station relative to the macrocell and each femtocell; and (c) selecting for the mobile station one of the femtocells for a hand-off, wherein the femtostation is selected based on the combined capacity of the macrocell and the femtocells after the hand-off.

Abstract: In a co-channel deployment of narrowband and multi-carrier technologies (e.g., a femtocell and a macrocell), a method provides cancelling of interference which treats the co-channel signals as desired signals and enhances each of them iteratively. At each iteration, each signal is demodulated and regenerated based on symbol decisions already made and a predetermined channel impulse response. To estimate the other (interfering) co-channel signal, the regenerated signal is subtracted from the aggregate signal. Simulations have shown that a method of the present invention can provide fundamental improvement in the performances of both interfering systems in as few as two iterations. The fundamental performance gain that can be obtained outweigh the required computational burden.

Abstract: A femtocell network uses idle resource blocks of a data frame to reduce interference by spreading the resource blocks of the users over the available spectrum. Spreading may be achieved by repeating the transmission using a number of the resource block groups. As a result, (a) more robustness is obtained against interference; (b) transmission power levels may be decreased because of the spreading, resulting in reducing interference between nearby femtocells and between a macrocell and a femtocell. Other methods of spreading such a frequency or time slot hopping may also be used.

Abstract: A method for an opportunistic network within a coverage area of a primary network includes (a) spectrum-sensing signals from users in the primary network to identify unused spectrum resources in a spectrum shared between the opportunistic network and the primary network; and (b) based on the spectrum resources identified, assigning the identified spectrum resources to be used among the users of the opportunistic network in one or more block sizes determined from expected interference from the users of the primary network. The method is applicable to a primary network whether or not spectrum resources are assigned to its users using a block-wise subcarrier assignment scheme or a randomized allocation scheme. The identified unused spectrum resources that are to be assigned to the users of the opportunistic network exclude un-used subcarriers adjacent to subcarriers used by the users of the primary network to avoid interference.

Abstract: Synchronization of a macrocell network with one of its sub networks (e.g., a femtocell network, a microcell network) is important for reducing the level of inter-carrier interference (ICI) that exists between the uplink users of a macrocell network and the sub-network. Even though blind synchronization techniques based on single-user signal conditions are known, the signal models are ineffective in multiuser scenarios and do not provide for reducing ICI effects. A blind synchronization method is disclosed which reduces ICI for sub network communications. Additionally, a method is disclosed which accurately and blindly synchronizes to the first user using an extended correlation window.

Abstract: A method and a communication system including femtocells within a macrocell efficiently manage interference between the different femtocells, and between each femtocell and a macrocell. An efficient frequency assignment scheme for the femtocells minimizes interference between a femtocell and a macrocell and among different femtocells using a spectrum-sensing technique carried out by the femtocells. The frequency assignment scheme selects a suitable channel from a set of candidate channels and ensures that the femtocell has an acceptable coverage area even when it is close to the macrocell base station (BS). The frequency assignment scheme favors a co-channel implementation to take advantage of the hand-off and cell search characteristics of the co-channel implementation. In one embodiment, a joint power control and frequency band assignment technique is used, which partitions the coverage area of the macrocell into an inner region, a power control region, and an outer region.

Abstract: Non-line-of-sight (NLOS) identification and mitigation are carried out in a wireless positioning system based on channel statistics derived from multipath components of a received signal. The statistics may be based on the kurtosis, the mean excess delay spread, or the root mean square delay spread. The results are justified using IEEE 802.15.4a ultrawideband channel models. Amplitude and delay statistics based on the IEEE models are shown to be log-normal random variables. A joint likelihood ratio test is presented for the LOS and NLOS identification.

Abstract: A method mitigates NLOS conditions based on weighted least squares (WLS) technique, in which the weights are derived from multipath components (MPCs) of the received signals. The weighting methodology can be used with both linear and non-linear least squares models, as well as different other NLOS mitigation schemes, such as residual based algorithms or maximum likelihood techniques.

Abstract: A method that estimates jointly and iteratively the first arriving path of a received signal and a mobile terminal location uses a residual location error. The method may include setting a ranging threshold to reduce residual location error. The method iteratively estimates the first arriving path of the received signals and mobile terminal location, with the estimate of mobile terminal location improving the estimate of the first arriving path, and vice versa. Initially, a peak selection method determines a rough time-of-arrival (TOA) for a signal received at each of a number of different fixed terminals. An estimate of the location of the mobile unit is then provided (e.g., based on a least-squares (LS) triangulation). If the residual error is unsatisfactory, the TOAs are refined, using a search-back algorithm, which searches back from the strongest paths of the received signals. The new TOAs are used to refine the estimate of the location of the mobile terminal.

Abstract: A method for identifying a leading edge time period of a received radio signal includes identifying a greatest energy time period in a sequence of time periods. The received radio signal has a greatest average energy in the greatest energy time period. The method also includes identifying a least energy time period in the sequence of time periods. The received radio signal has a least average energy in the least energy time period. Further, the method includes setting a threshold energy based on the greatest average energy and the least average energy, determining a number of window time periods based on a characteristic of a radio channel used by the received radio signal, and identifying as a leading edge time period an earliest time period that precedes the greatest energy time period within the number of window time periods. The received radio signal in the leading edge time period has an average energy greater than or equal to the threshold energy.

Abstract: A method and apparatus is disclosed herein for synchronized multi-link transmission in an ARQ-enabled multi-hop wireless network. In one embodiment, the method comprises performing pre-transmission of a packet to hops to enable a base station and the plurality of hops in the network to transmit the packet synchronously to one or more mobile stations in the wireless communication system; and performing one or more re-transmissions of the packet at a set of one or more hops forming a path in the network if time remaining before a synchronized transmission time for the path as a whole is greater than a threshold.

Abstract: A method for estimation a time-of-arrival of a radio signal is provided. The signal is an ultra-wideband (UWB) signal. The method uses kurtosis of the received signal to estimate an energy threshold of the signal. The energy threshold can be used to determine a time-of-arrival of the signal.

Abstract: A method and apparatus is disclosed herein for transmitting data in a network (e.g., a relay network). In one embodiment, the method comprises performing pre-transmission of a packet to hops to enable the base station and the plurality of hops to transmit the packet synchronously to one or more mobile stations in the wireless communication system; and performing one or more re-transmissions of the packet at a first set of one or more hops in the system during a delay due to pre-transmissions at a second set of one or more hops in the system.

Abstract: A method and system (500) estimates a time of arrival of a signal received via a wireless communications channel. The energy in the received signal is conditioned at multiple different time scales to produce a conditioned signal (700). Then, a leading edge is detected in the conditioned signal (550). The leading edge corresponds to the time of arrival of the received signal (551).

Abstract: A linear least squares (LLS) estimator provides a low complexity estimation of the location of a mobile terminal (MT), using one of the fixed terminals (FTs) as a reference FT to derive a linear model. A method for selecting a reference FT is disclosed, which improves the location accuracy relative to an arbitrary approach to selecting the reference FT. In addition, a covariance-matrix based LLS estimator is proposed in line-of-sight (LOS) and non-LOS (NLOS) environments to further provide accuracy, taking advantage of the correlation of the observations. Different techniques for selecting the reference FT under non-LOS (NLOS) conditions are disclosed. A map-based two-stage LLS estimator assists in selecting the reference FT under NLOS conditions.

Abstract: A time-of-arrival (TOA) estimation method for multi-band orthogonal frequency division multiplexing (MB-OFDM) signals uses a simple equally-spaced channel model to recover the impulse response of the wireless channel, and locates the delay of the first channel path by minimizing the energy leakage from the first channel path. The TOA is estimated based on the delay. Such a method does not require channel information for TOA estimation at the receiver and does not require modification of the receiver structure. The method also avoids a sub-optimal solution known to occur in maximum likelihood (ML) estimation.

Abstract: A method is provided for MIMO uplink communications between a base station and a wireless station with more than two antennae. The method includes: (a) negotiating between the base station and the wireless station uplink MIMO/cooperative MIMO capabilities, using a message exchange protocol in which a message exchanged comprises a field for specifying uplink MIMO/cooperative MIMO capabilities; (b) the base station receiving a request from the wireless station for data transmission; (c) the base station sending the wireless station an allocated resource and an uplink MIMO/cooperative MIMO method for uplink transmission; (e) the wireless station mapping data symbols to the allocated resource with proper pilot pattern; and (f) the base station detecting the data symbols from the channel.

Abstract: A method and apparatus is disclosed herein for performing multi casting. In one embodiment, the method comprises receiving routing, association, relaying, and/or topology information associated with a plurality of nodes in a multi-hop wireless network, the plurality of nodes communicably coupled in a tree or mesh arrangement via a plurality of broadcast channels; and determining a subset of the plurality of nodes over each broadcast channel on the multi-hop wireless network that is responsible for sending acknowledgment information, in response to receipt or lack of receipt of transmissions, back to senders of transmissions.

Abstract: A method mitigates NLOS conditions based on weighted least squares (WLS) technique, in which the weights are derived from multipath components (MPCs) of the received signals. The weighting methodology can be used with both linear and non-linear least squares models, as well as different other NLOS mitigation schemes, such as residual based algorithms or maximum likelihood techniques.