# US 7,610,036 B2 · Space-time-frequency sensing of RF spectrum in cognitive radios > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,610,036 B2 - Document ID: US7610036B2 - Status: Granted - Kind: B2 - Application number: 11/620,759 - Filed: 2007-01-08 - Published: 2008-07-10 - Granted: 2009-10-27 - Earliest claimed: 2007-01-08 - Assignees: Mitsubishi Electric Research Laboratories, Inc. - Inventors: Koon Hoo Teo; Hongyuan Zhang; Yves-Paul N. Nakache; Jinyun Zhang - Web page: https://patentgrep.com/patent/US7610036B2 ## CPC - H04W 72/046: {the resource being in the space domain, e.g. beams} - H04L 27/0006: {Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio (for spectrum sharing between different networks H04W16/14)} - H04L 5/0062: {Avoidance of ingress interference, e.g. ham radio channels} - H04W 16/28: using beam steering - H04W 24/00: Supervisory, monitoring or testing arrangements - H04W 72/542: using measured or perceived quality - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method detects unused frequency bands in a cognitive radio network. Multiple frequency bands for RF signals are sensed using an antenna array including a plurality of elements coupled to a receive RF chain, in which the plurality of elements are individually controllable. For each frequency band, multiple spatial directions are sensed for the RF signals using the antenna array. A particular frequency band and a particular direction and a particular time slot are assigned as an available frequency band, an available direction and a particular time slot for transmitting RF signals in a cognitive radio if the RF signals are not sensed in the particular spatial direction for the particular frequency band, and in which the RF signals are transmitted by a transmit chain connected to the antenna array. ## Claims ### Claim 1 A method for detecting unused frequency bands in a cognitive radio network, comprising the steps of: sensing a plurality of frequency bands for RF signals using an antenna array including a plurality of elements coupled to a receive RF chain, in which the plurality of elements are individually controllable; sensing, for each frequency band, a plurality of spatial directions for the RF signals using the antenna array including the plurality elements coupled to the receive RF chain; and assigning a particular frequency band and a particular direction as an available frequency band and an available direction for transmitting RF signals in a cognitive radio if the RF signals are not sensed in the particular spatial direction for the particular frequency band, in which the RF signals are transmitted by a transmit chain connected to the antenna array. ### Claim 2 (depends on 1) The method of claim 1, further comprising: sensing the plurality of spatial directions over different time intervals. ### Claim 3 (depends on 1) The method of claim 1, in which the plurality of spatial directions are sensed by time shifting the RF signals received by the plurality of elements with respect to each other. ### Claim 4 (depends on 1) The method of claim 1, in which the plurality of spatial directions are sensed by phase shifting the RF signals received by the plurality of elements with respect to each other. ### Claim 5 (depends on 1) The method of claim 1, in which the set of spatial directions are orthogonal to each other and further comprising: sensing the set of spatial directions at the same time and in the same frequency band. ### Claim 6 (depends on 5) The method of claim 5, in which a number of the spatial directions is equal to a number of the elements. ### Claim 7 (depends on 1) The method of claim 1, in which the sensing and assigning is performed cooperatively by multiple transceivers. ### Claim 8 (depends on 1) The method of claim 1, in which results of the sensing are distributed in a frequency domain. ### Claim 9 (depends on 1) The method of claim 1, in which the distribution uses a media access layer. ### Claim 10 (depends on 1) The method of claim 1, further comprising: selecting transmit and receive beamforming matrices for the available frequency band. ### Claim 11 (depends on 1) The method of claim 1, in which the matrices are quantized. ### Claim 12 (depends on 1) The method of claim 1, further comprising: calibrating RF imbalance between the receive RF chain and a transmit RF chain. ### Claim 13 (depends on 1) The method of claim 1, in which the sensing and transmitting are separated in different time durations. ### Claim 14 (depends on 1) The method of claim 1, in which the sensing and transmitting are conducted simultaneously at different frequency bands. ### Claim 15 (depends on 1) The method of claim 1, in which the receive RF chain is operated according to a matrix RxBF, and the transmit RF chain is operated according to a matrix TXBF, and in which the matrices are combined as an equivalent channel matrix for a MIMO network. ### Claim 16 (depends on 1) The method of claim 1, in which the receive RF chain is operated according to a matrix RxBF, and a transmit RF chain is operated according to a matrix TXBF, and in which the matrices are combined as an equivalent channel matrix for multi-user network. ### Claim 17 (depends on 1) The method of claim 1, in which the assigning is performed at a centralized location. ### Claim 18 (depends on 1) The method of claim 1, in which multiple transmit chains transmit the RF signals in the same available frequency band using time multiplexing. ### Claim 19 (depends on 1) The method of claim 1, in which each frequency band includes a set of subcarriers, and the sensing and assigning is performed for each subcarrier for the plurality of directions.