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Coexistence techniques in wireless networksRelated Patent Categories: Telecommunications, Transmitter And Receiver At Separate Stations, Short Range Rf CommunicationCoexistence techniques in wireless networks description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060211372, Coexistence techniques in wireless networks. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 09/714,803, filed Nov. 16, 2000, now U.S. Pat. No. 7,039,358, issued May 2, 2006, which claims the benefit of U.S. Provisional Application Ser. No. 60/175,262, filed Jan. 10, 2000 and U.S. Provisional Application Ser. No. 60/196,979, filed Apr. 13, 2000, each of which are incorporated in their entireties herein, and from which priority is claimed. BACKGROUND OF THE INVENTION [0002] This invention relates to wireless data communications networks, and in particular to arrangements for ensuring coexistence between wireless networks that share the same frequency band with different operating protocols. [0003] Wireless devices communicate with one another using agreed-upon protocols that are transmitted in predefined frequency bands. Often, devices using one or more wireless protocols may operate by transmission within the same frequency band. It is therefore necessary to develop coordination techniques in order for devices using one or more wireless protocols to efficiently operate in the same band of frequencies at the same time. [0004] For example, the assignee of the present invention supplies wireless data communications systems known as the Spectrum 24.RTM. System that follows the communications protocol of IEEE 802.11 Standard (802.11), which is hereby incorporated by reference. In the system as implemented, mobile units (MUs) are in data communication with a central computer through one or more access points (APs). The APs may communicate with a computer directly or over an Ethernet wired network. Each of the MUs associates itself with one of the APs. As defined in 802.11, this communications protocol uses the 2.4 GHz ISM frequency band. [0005] As currently designed, 802.11 devices may use several predefined methods for transmission within the 2.4 GHz band to perform as a wireless local area network. One method is to use a frequency hopping spread spectrum (FHSS) mechanism wherein data is transmitted for a certain period of time in a particular channel and, following a pseudorandom sequence, continues transmission at a different channel for the same predetermined length of time. As currently designed, 802.11 devices operate at a frequency hopping rate of 10 hops/second. Another method is to use a direct sequence spread spectrum (DSSS) mechanism wherein the data is transmitted in a predetermined frequency channel and is multiplied by a pseudorandom chipping sequence during transmission. [0006] As all 802.11 devices use the same ISM frequency band, interference among these devices is minimized by use of a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol. Under CSMA/CA, an 8021.11 device listens for another's devices transmission prior to initiating its own transmission. If no other transmission is detected, the device transmits its information and waits for an acknowledgment (ACK) from the receiving device. If no acknowledgment of receipt is received after a pre-determined time interval, the device will retransmit after waiting for a randomly chosen interval of time. Thus, if two or more devices began transmitting coincidentally at the same time and the resulting interference blocks all of the transmissions, each device will wait a random amount of time to attempt a retransmission. This allows the devices to transmit at different times. [0007] Another example of a wireless specification that also uses the 2.4 GHz ISM frequency band is Bluetooth.TM., which is designed for communication among devices within a short range transmitting at a lower power level. The Bluetooth specification, version 1.1, which would be known to one of ordinary skill in the art, is fully incorporated herein by reference. As currently designed, Bluetooth operates using a frequency hopping spread spectrum mechanism at a rate of 1600 hops/second. Bluetooth uses a master/slave system of communication. One example of a Bluetooth network may be a mobile device attached to the user's belt that communicates with a cordless scanner for reading bar codes and worn by the user as a ring. In this case, the mobile device would operate as the master and the cordless ring scanner would operate as the slave. In this system for data transmission, the master and slave only communicate at predefined intervals. At the first interval, the master may communicate to a first slave device, which may only respond during the second interval. At the third interval, a master may communicate to a second slave device, which may only respond during a fourth interval. By using this system, it is ensured that only one device within a particular Bluetooth "piconet" is transmitting at any particular time. Thus, interference is minimized. [0008] Additionally, it is desirable for one Bluetooth piconet to operate in close proximity with another, separate Bluetooth piconet. Because there are 79 different frequency channels used by Bluetooth, different Bluetooth networks are unlikely to be operating on the same frequency at the same time. Interference between the separate Bluetooth piconets is thus minimized. This allows, for example, multiple individuals working in close proximity with one another to each have his or her own mobile unit along with a cordless ring scanner. [0009] Along with the need to operate multiple networks of the same protocol in close proximity, there is also a recognized need in the art to coordinate the transmissions of devices operating under different protocols that use the same frequency band. For example, it may be desirable to use a cordless ring scanner that communicates with belt-mounted terminal using the Bluetooth protocol while the same belt mounted terminal communicates with an access point using the 802.11 protocol. For example, once the user scans-a bar code using the cordless ring scanner, the bar code information may be sent to the belt-mounted terminal. That bar code information may then be transmitted to the 802.11 AP. Then an acknowledgment, and possibly a message, may need to be sent from the AP back to the belt-mounted terminal. The terminal may also need to communicate with other Bluetooth enabled peripherals like a printer or a headset. Although communication protocols such as 802.11 and Bluetooth are designed to ensure that devices using the same protocol may operate in the same frequency band with a minimum of interference, there has heretofore been no method of coordination for the use of these wireless devices in the same frequency operating under different communication protocols. [0010] It is additionally desirable to provide voice service using the Bluetooth communications protocol, for example, between a belt-mounted terminal and a headset worn by the user. Bluetooth supports voice communications using Synchronous Connection Oriented (SCO) voice packets which are transmitted every 3.75 ms. The requirement for such frequent Bluetooth packet transmission makes it difficult to coordinate voice transmission using the Bluetooth SCO packets with 802.11 communications. [0011] It is therefore an object of this invention to utilize coordination techniques to ensure that, for example, both Bluetooth and 802.11 enabled devices, may operate robustly in the same frequency band at the same time. SUMMARY OF THE INVENTION [0012] An embodiment of the present invention includes a first radio transceiver operating in accordance with a first communication protocol (which may be the 802.11 protocol) and using a frequency band (which may be the 2.4 GHz ISM band), a base station operating in accordance with the first communication protocol, a second radio transceiver operating in accordance with a second communication protocol (which may be the Bluetooth protocol) and using the frequency band, and a coordinator associated with the base station for, in turn, activating the first radio transceiver, deactivating the first radio transceiver, activating the second radio transceiver, and deactivating the second radio transceiver. [0013] The first radio transceiver and the second radio transceiver may be mounted together in a housing, which may be suitable for wearing on a belt or a laptop computer or a PDA. One or more slave devices may be associated with the second transceiver and operate in accordance with the second communication protocol. The slave devices may include a scanner, worn on a user's finger and capable of transmitting bar code information to the second transceiver, a printer, or a personal data managing device. [0014] In one arrangement wherein the first and second transceivers are mounted together in a housing, they may include orthogonally polarized antennas. In another arrangement a Bluetooth protocol transceiver transmits at power level of about 0 dBm. In still another arrangement, two or more sub bands within the frequency band are provided and the 802.11 protocol transceiver uses one of the two or more sub-bands and the Bluetooth protocol transceiver uses another of the two or more sub-bands. In still another arrangement in the second radio transceiver is equipped with a look-ahead function for determining whether two or more sub-bands are being used by the first radio transceiver that will also be used by the second transceiver. In still another arrangement, a coordinator is associated with the first radio transceiver for deactivating the second radio transceiver while the first radio transceiver is in use. [0015] According to the invention, there is provided a method for operating a portable data communications device using first and second wireless data communications protocol. The data communications device is operated in a power saving mode of the first communication protocol, whereby the device has active time periods for transmitting and receiving data communications signals using the first communications protocol and dormant time periods during which the device neither transmits nor receives data communications signals using the first protocol. The data communications device is operated as a master device according to the second communications protocol whereby the data communication device controls operation of slave devices communicating therewith. The operation according to the second data communications protocol is controlled to operate only during the dormant time periods of the first protocols. [0016] In one embodiment, a signal indicating that the active time period will commence following a predetermined time interval is provided to terminate operation according to the second data communication protocol during the predetermined time interval. The first wireless data communications protocol may be the 802.11 protocol. The second wireless communication protocol may be Bluetooth. [0017] In another aspect of the invention, there is provided a method for operating a wireless data communications system having an access point and at least one mobile unit associated with said access point using a first wireless protocol (which may be 802.11), wherein said mobile unit is arranged to conduct wireless data communications with other units using a second wireless protocol (which may be Bluetooth). Periodic beacon signals are transmitted from the access point according to the first wireless protocol. Global clear to send signals are transmitted from the access point according to the first wireless protocol, whereby the global clear to send signals prevent mobile units from transmitting signals using the first data communications protocol during an allocated time interval within the beacon signal period. The access point is controlled to avoid transmissions during the allocated time interval, and the mobile unit is operated in response to the global clear to send signal to conduct wireless communications acting as a master unit using the second wireless protocol during the allocated time interval. [0018] In one embodiment, the beacon signal period is divided into three time intervals, wherein the access point conducts power saving mode data communications during a first time interval, wherein the access point conducts data communications using the second communications protocol during the second time interval and wherein the access point conducts data communications using the first wireless protocol during a third time interval. The first time interval may immediately following the beacon signal. In another embodiment, the first time interval may not be utilized. [0019] In accordance with another aspect of the invention, there is provided a method of operating a data communications system using a master-slave protocol (such a Bluetooth), wherein a master transceiver transmits to slave units during first even time slots and wherein slave units transmit to the master unit during odd time slots, and wherein the transmissions follow a predetermined frequency hop pattern at a hop rate corresponding to the time slots. The master unit is operated during a first time period of each time slot to detect interfering signals at a frequency corresponding to the following time slot. Transmission by the master transceiver is inhibited during even time slots if interfering signals have been detected during either of the current or previous time slots. [0020] In a preferred practice, the operating step includes tuning the master unit to receive signals corresponding to the frequency allocated to the next following time slot; detecting the strength of signals received and retuning the master unit to send or receive signals corresponding to the frequency allocated to the current time slot. [0021] In another aspect of the invention, there is provided a method for providing voice communications in a wireless data communications system having a mobile unit arranged to communicate with an access point using a first data communications protocol (such as 802.11) and arranged to communicate with other devices using a second data communications protocol (such as Bluetooth). Data corresponding to the voice communication is communicated between the access point and the mobile unit using the first data communications protocol. The data corresponding to the voice communications is communicated between the mobile unit and a portable device using the second data communication protocol. The communication is arranged at time intervals which avoid interference with the communicating using the first data communications protocol. Voice signals are converted to data corresponding to the voice signals and data signals corresponding to voice signal are converted into voice signals in the portable device. Continue reading about Coexistence techniques in wireless networks... Full patent description for Coexistence techniques in wireless networks Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Coexistence techniques in wireless networks patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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