Abstract: Disclosed are techniques for channel-based coding for wireless communications. A transmitter includes circuitry and multiple antennas. The circuitry selects a subset of the antennas, determines a respective channel response for each of the antennas in the subset, generates a respective coded system for each of the antennas in the subset, and transmits the coded symbols using the antennas in the subset.

Abstract: Systems and methods for securing orthogonal frequency division multiplexing (OFDM) transmission of data are discussed herein. Transceivers can sense the signal strength of frequencies on an OFDM wireless channel. The transceivers can determine which of the frequencies are fading frequencies failing below a threshold. A transmitting transceiver can send artificial data on the failing frequencies and genuine data on the remaining frequencies. Artificial data can be designed to mitigate peak-average-power ratio (PAPR) to have an additional benefit without using extra resource.

Abstract: Systems and methods for securing orthogonal frequency division multiplexing (OFDM) transmission of data are discussed herein. Transceivers can sense the signal strength of frequencies on an OFDM wireless channel. The transceivers can determine which of the frequencies are fading frequencies failing below a threshold. A transmitting transceiver can send artificial data on the failing frequencies and genuine data on the remaining frequencies. Artificial data can be designed to mitigate peak-average-power ratio (PAPR) to have an additional benefit without using extra resource. Finally, receiving transceiver can transceiver receive the genuine data while discarding any date received on the failing frequencies.

Abstract: Modulated orthogonal frequency division multiplexing (OFDM) subcarriers generate high sidelobes, resulting in adjacent channel interference (ACI). Current sidelobe suppression techniques, such as inserting guard intervals or cancellation carrier bands, diminish the useful radio spectrum or consume significant wireless device resources. Disclosed is a method of suppressing sidelobes through adding an adaptive extension to OFDM symbols that is calculated to avoid ACI while keeping power consumption to low levels. Bandwidth and user location information are collected by a cognitive radio an utilized to determine the extension used. The method significantly reduces ACI to other bands and reduces the required guard bands, opening the radio spectrum to more efficient use.

Abstract: An optimum time domain windowing scheme for orthogonal frequency-division multiplexing (OFDM)-based waveforms in the sense of spectral concentration is proposed. Instead of evenly suppressing the sidelobes along the frequency, the sidelobe power is concentrated within a guard band while maximally suppressing the power for a desired frequency range. This is achieved by employing optimum finite duration pulses, prolate spheroidal wave functions (PSWF), to shape the OFDM transmit pulse. Also with per-subcarrier windowing scheme, the effect of inner subcarriers on sidelobes is diminished by utilizing the concentration bandwidth versus out-of-band power trade-off in PSWF and the multicarrier nature of the OFDM.

Abstract: Various methods and systems are provided for edge windowing of orthogonal frequency division multiplexing (OFDM) systems. In one example, among others, a method includes obtaining an edge windowing portion by reducing a cyclic prefix size for a quantity of edge subcarriers in an OFDM symbol and reducing side lobes by applying a windowing function to the edge subcarriers. In another example, a device includes a separator capable of dividing subcarriers of an OFDM symbol into first and second subcarrier groups, a first CP adder capable of obtaining a windowing portion by adjusting a cyclic prefix size of the first subcarrier group, and a first windower capable of reducing side lobes by applying a windowing function to the first subcarrier group. In another example, a method includes determining a RMS delay spread of a mobile station and scheduling a subcarrier based at least in part upon the RMS delay spread.

Abstract: Systems, methods and instrumentalities are disclosed for superposed signaling for bandwidth efficiency in wireless communications. Homogeneous and heterogeneous signals may be superposed on the same channel. Superposed signals may comprise, for example, multi carrier, frequency division and code division signals, including multiple access, e.g., OFDMA and CDMA, signals. Data for various receivers may be dynamically selected for signal superpositioning, for example, based on radio access technology, communication rate (e.g. high and low rates), distance between transmitter and receiver (e.g. near and far signals). Communication rate and power may be allocated to superposed signals. Interference nulling may be applied, for example, by selecting or excluding spreading codes and/or subcarriers. Nulled locations may be used to transmit critical information. Interference shaping may be applied to modify interference, e.g., by transmitting interference symbols using reserved spreading codes. Support information, e.

Abstract: Modulated orthogonal frequency division multiplexing (OFDM) subcarriers generate high sidelobes, resulting in adjacent channel interference (ACI). Current sidelobe suppression techniques, such as inserting guard intervals or cancellation carrier bands, diminish the useful radio spectrum or consume significant wireless device resources. Disclosed is a method of suppressing sidelobes through adding an adaptive extension to OFDM symbols that is calculated to avoid ACI while keeping power consumption to low levels. Bandwidth and user location information are collected by a cognitive radio an utilized to determine the extension used. The method significantly reduces ACI to other bands and reduces the required guard bands, opening the radio spectrum to more efficient use.

Abstract: Disclosed are various embodiments that are directed towards distinguishing between various types of interference in an orthogonal frequency division multiplexing (OFDM) wireless communication system. According to some embodiments, the system receives a set of symbols encoded in a predetermined subcarrier activation pattern according to an OFDM protocol. The system may determine a plurality of time averaged interference values, each time averaged interference value corresponding to a respective subcarrier index expressed in the set of symbols. Then, the system may separate frequency-based interference from time-based interference according to the plurality of time averaged interference values.

Abstract: An optimum time domain windowing scheme for orthogonal frequency-division multiplexing (OFDM)-based waveforms in the sense of spectral concentration is proposed. Instead of evenly suppressing the sidelobes along the frequency, the sidelobe power is concentrated within a guard band while maximally suppressing the power for a desired frequency range. This is achieved by employing optimum finite duration pulses, prolate spheroidal wave functions (PSWF), to shape the OFDM transmit pulse. Also with per-subcarrier windowing scheme, the effect of inner subcarriers on sidelobes is diminished by utilizing the concentration bandwidth versus out-of-band power trade-off in PSWF and the multicarrier nature of the OFDM.

Abstract: Various methods and systems are provided for edge windowing of orthogonal frequency division multiplexing (OFDM) systems. In one example, among others, a method includes obtaining an edge windowing portion by reducing a cyclic prefix size for a quantity of edge subcarriers in an OFDM symbol and reducing side lobes by applying a windowing function to the edge subcarriers. In another example, a device includes a separator capable of dividing subcarriers of an OFDM symbol into first and second subcarrier groups, a first CP adder capable of obtaining a windowing portion by adjusting a cyclic prefix size of the first subcarrier group, and a first windower capable of reducing side lobes by applying a windowing function to the first subcarrier group. In another example, a method includes determining a RMS delay spread of a mobile station and scheduling a subcarrier based at least in part upon the RMS delay spread.

Abstract: Modulated orthogonal frequency division multiplexing (OFDM) subcarriers generate high sidelobes, resulting in adjacent channel interference (ACI). Current sidelobe suppression techniques, such as inserting guard intervals or cancellation carrier bands, diminish the useful radio spectrum or consume significant wireless device resources. Disclosed is a method of suppressing sidelobes through adding an adaptive extension to OFDM symbols that is calculated to avoid ACI while keeping power consumption to low levels. Bandwidth and user location information are collected by a cognitive radio an utilized to determine the extension used. The method significantly reduces ACI to other bands and reduces the required guard bands, opening the radio spectrum to more efficient use.

Abstract: Various methods and systems are provided for edge windowing of orthogonal frequency division multiplexing (OFDM) systems. In one example, among others, a method includes obtaining an edge windowing portion by reducing a cyclic prefix size for a quantity of edge subcarriers in an OFDM symbol and reducing side lobes by applying a windowing function to the edge subcarriers. In another example, a device includes a separator capable of dividing subcarriers of an OFDM symbol into first and second subcarrier groups, a first CP adder capable of obtaining a windowing portion by adjusting a cyclic prefix size of the first subcarrier group, and a first windower capable of reducing side lobes by applying a windowing function to the first subcarrier group. In another example, a method includes determining a RMS delay spread of a mobile station and scheduling a subcarrier based at least in part upon the RMS delay spread.

Abstract: In one embodiment, a method of mitigating uplink inter-carrier interference (ICI) from macrocell mobile stations at a dedicated channel femtocell base station is provided that includes: determining a timing offset for a femtocell uplink symbol timing that reduces the ICI based upon an expected spatial distribution for the macrocell mobile stations with respect to the femtocell base station; communicating the timing offset to at least one femtocell mobile station; and at the femtocell base station, receiving an uplink symbol transmission from the at least one femtocell mobile station according to the timing offset.

Abstract: A femtocell increases efficiency and coverage of a macrocellular network operating in a co-channel manner within the macrocell spectrum by selecting subcarriers for its mobile station using both the subcarrier allocation map received from the macrocell and a spectrum sensing operation. Interference is avoided by selecting only subcarriers not allocated by the macrocell and subcarriers allocated to users not nearby to the femtocell. Interference is eliminated from the received signals using co-channel interference avoidance techniques. Selection of subcarriers for femtocell use may take into consideration inter-carrier interference detected.

Abstract: The present invention provides a system and method for exploiting location awareness to improve the communication performance in a wireless cognitive radio system. The invention includes determining the absolute position information for the cognitive radio system, receiving digital topographical data related to the absolute position information, classifying the environment of the cognitive radio system based on the absolute position and the topographical data, matching the classified environment with corresponding statistical parameters and improving the communication performance of the cognitive radio system by adapting the cognitive radio system according to the corresponding statistical parameters.

Abstract: A method of receiving Multiple Input Multiple Output—Orthogonal Frequency Division Multiple Accessing (MIMO-OFDMA) signals using a single receiver rather than multiple receivers and performing measurements specific to various parts of MIMO-OFDMA systems using all measurable parameters of MIMO-OFDMA systems is disclosed. In addition, a method of receiving and completing impairment estimation of WiMAX MIMO signals using a single receiver according to the IEEE 802.16 standards is provided.

Abstract: In accordance with the present invention, novel methods for adaptive receiver design and related parameter estimation techniques for efficient and non-coherent reception of ultrawideband signals are presented. Efficient estimation of maximum excess delay of the channel for enabling many useful adaptation techniques is additionally provided. Also, noise power estimation which significantly improves the performance of the receivers is presented.

Abstract: In accordance with the present invention, a system and method for orthogonal frequency division multiplexing (OFDM) sidelobe suppression is provided. In a particular embodiment an extension is added to OFDM symbols that is calculated using optimization methods to minimize adjacent channel interference (ACI) while keeping the extension power at an acceptable level. Using this technique, interference to adjacent signals is reduced significantly at the cost of a small decrease in the useful symbol energy. The proposed method can be used by cognitive radio (CR) systems to shape the spectrum of OFDM signals and to minimize interference to licensed users (LU), or to reduce the size of guard bands used in conventional OFDM systems.

Abstract: Spectrum sensing is one of the most challenging problems in cognitive radio systems. The spectrum of interest needs to be characterized and unused frequencies should be identified for possible exploitation in a simple and fast way, allowing the radio to catch up with the changing transmission parameters. A sensing method is presented where primary users are identified by matching the features extracted from the received signal to the a priori information about primary users' transmission characteristics. For estimation of some signal parameters, the cyclostationarity of the transmission spectrum is explored by using a suboptimal maximum likelihood (ML) estimator. The proposed algorithms can be used in cognitive radio for identifying various transmissions and for electronic surveillance.