Patent Description:
Portable battery powered communication devices are often utilized in public safety environments, such as law enforcement, fire rescue, and the like. There is an increased desire to expand the functionality of public safety communication devices to incorporate additional features that run on different operating platforms, other than the main mission critical public safety platform. Such devices may be referred to as converged devices. It is highly desirable that a converged device be able to operate two modems simultaneously. However, operating two modems simultaneously can result in plethora of complex self-interference scenarios not encountered in conventional single modem devices. For example, out-of-band emissions, blocking and/or intermediation occurring in one sub-system of a converged device may severely interfere with the performance of another sub-system of the converged device. Compliance with regulatory emission limits may also lead to inter-modulation artifacts from one modem interference with nearby spectrum of another modem.

<CIT> discloses an antenna coexistence mutual-interference processing method. The method comprises the following steps: judging whether coexistence mutual-interference is present between an LTE antenna and a WLAN antenna, wherein the LTE antenna is used for transmitting an LTE signal, and the WLAN antenna is used for transmitting a WLAN signal, if the coexistence mutual-interference is present between the LTE antenna and the WLAN antenna, detecting whether a situation in which one of the LTE antenna and the WLAN antenna transmits the signal and the other receives the signal within the same time period exists, if so, adjusting a resonance point of the LTE antenna and/or the resonance point of the WLAN antenna according to a preset adjustment strategy, so that the resonance point of the LTE antenna and the resonance point of the WLAN antenna are away from each other.

Existing strategies to interference mitigation, such as those used on single modem devices, do not lend themselves well to converged devices, as these strategies tend to negatively impact performance and timing of one or more sub-systems.

Hence, there is a need for an improved interference mitigation approach in a converged portable communication device.

Briefly, there is provided herein an apparatus and method for dynamically managing simultaneous modem operation in a portable communication device. The embodiments are directed to mitigating interference resulting from the simultaneous operation of the two or more modems. Improved converged communications is provided through the use of a programmable logic array operating as a coexistence module (CEM) interoperating with a plurality of different processors, a plurality of different modems, and a plurality of attenuation switches. Interference during converged operation is detected, analyzed, and applicable mitigation is applied to the interference, thereby enabling converged communications to be established in a mitigated mode. The mitigated mode of operation continues until the interference has been removed. Mission critical communications is maintained without relying on the use of infrastructure collaboration.

<FIG> is a block diagram of a portable communication device <NUM> formed and operating in accordance with some embodiments. The portable communication device <NUM> is powered by a battery (not shown). The portable communication device <NUM> comprises a programmable logic array operating as a coexistence module (CEM) <NUM>, an applications processor (AP) <NUM> operatively coupled to the CEM <NUM>, and a baseband processor (BP) <NUM> operatively coupled to the CEM and the AP. The portable communication device <NUM> further comprise a first modem <NUM>, such as a land mobile radio (LMR) modem, operatively coupled to the BP <NUM>, the first modem operating using a first frequency band of operation. The first modem is responsible for mission critical operations, such as scan, push-to-talk (PTT), and high power audio. The portable communication device <NUM> further comprises a second modem <NUM>, such as a long term evolution (LTE) modem, operatively coupled to the AP <NUM>, the second modem operating using a second frequency band of operation. The AP <NUM> is responsible for non-mission critical operations, such as software applications associated with touchscreen interface, low power audio, and global positioning system (GPS). Other radio elements such as radio frequency (RF) transmitters, receivers, power amplifiers are not shown (to maintain simplicity) but are understood to be embodied within the device <NUM>.

In accordance with some embodiments, the AP <NUM>, the BP <NUM>, and the first and second modems <NUM>, <NUM> are operable in a converged mode in which both the first and second modems operate simultaneously receiving and transmitting signals via respective first and second antennas <NUM>, <NUM>, such as an LMR antenna and an LTE antenna. Data <NUM> is transferred between the baseband processor <NUM> and the first modem <NUM> and then via the LMR TX/RX <NUM> onto the first antenna <NUM>. For example, narrowband data is transferred between the BP and the LMR modem and then to the LMR antenna. Data <NUM> is also transferred between the applications processor <NUM> and the second modem <NUM> and then via the LTE TX/RX <NUM> onto the second antenna <NUM>. For example broadband data is transferred between the AP and the LTE modem and then to the LTE antenna.

In accordance with the embodiments, the portable communication device <NUM> further comprises an attenuation switch <NUM> operatively coupled to the CEM <NUM> and to the second modem <NUM>. The attenuation switch <NUM> operates as a hardware clamp to second modem communications. The attenuation switch <NUM> is disengaged during normal, non-interfered converged operation. During engagement of the attenuation switch <NUM>, incoming RF signals to the second (LTE) antenna <NUM> are disconnected, thereby preventing external RF energy from damaging the second modem <NUM>. Protection is also provided from internal RF energy generated from the first modem (LMR internal). Additionally, outgoing RF signals from the second modem <NUM> via the LTE TX/RX signal <NUM> are also disconnected, thereby preventing RF Energy from the second modem <NUM> from interfering with the first modem <NUM>. The methods employed by the attenuation switch <NUM> may be one of shunting the antenna path to ground, or providing an open circuit between the antenna path and the second modem. The attenuation switch <NUM> may also be realized as a plurality of switches each acting on a plurality of paths to the second modem <NUM> and a plurality of second antennas <NUM>.

During converged operation, the BP <NUM> further generates indicator signals <NUM>, <NUM> to the CEM <NUM> and to the AP <NUM> while the first modem <NUM> is transmitting and receiving on a first frequency band. Simultaneously, the second modem <NUM> is generating indicator signals <NUM> to the CEM <NUM> and the AP <NUM> while transmitting and receiving on the second frequency band. For example, the BP <NUM> may generate the indicator signal <NUM> indicative of 'LMR transmit enabled' to the CEM <NUM> and to the AP <NUM>. The BP <NUM> may also generate the indicator signal <NUM> indicative of frequency band, such as 'LMR frequency', to the CEM <NUM> and to the AP <NUM>. The "LMR Frequency' may specify the exact LMR Frequency in use or a range of LMR frequencies that are currently in use. In simultaneous operations, the second modem <NUM> generates the indicator signal <NUM> to the CEM <NUM> and the AP <NUM> indicative of the frequency band of operation, such as 'LTE band'. 'The LTE' band' may specify the exact LTE frequency in use, or a range of LTE Frequencies in use, for example Band14 or Band5.

In accordance with some embodiments, the indicator signals <NUM>, <NUM>, <NUM> are analyzed by the CEM <NUM> and the AP <NUM> for interference. In response to detecting interference by the CEM <NUM>, the CEM drives a hardware attenuation enable line <NUM> to both the AP <NUM> and the attenuation switch <NUM>, thereby engaging the attenuation switch <NUM> which serves to disconnect the second modem <NUM> from the second antenna <NUM>. In response to the hardware attenuation enable line <NUM> being enabled, the AP <NUM> performs additional analysis to confirm the interference detected by the CEM <NUM>. In some embodiments, a change in the indicator signals <NUM>,<NUM>, <NUM> will trigger this interference analysis. The AP <NUM> then determines and performs an appropriate interference mitigation. This mitigation will be performed after an optional holdoff timer stage. The holdoff timer may be a configurable holdoff timer. The AP validates that the interference is still present before applying the interference mitigation. An example scenario would be during LMR scan, in which the time spent in the interference scenario would be shorter than the time required to engage the software mitigation. In some embodiments, where the AP determines that software mitigation is the appropriate interference mitigation, the AP <NUM> then drives the software mitigation line <NUM> to the CEM <NUM>. In other embodiments, where AP <NUM> determines that power mitigation is the appropriate interference mitigation, the AP <NUM> then instructs the second modem <NUM> to perform a specific power level interference mitigation, and the second modem <NUM> then drives a TX Power Level line <NUM> to the CEM <NUM>. In response to either the TX power level signal <NUM> or software mitigation signal <NUM>, the CEM <NUM> then releases the hardware attenuation enabled line <NUM> thereby releasing the attenuation switch <NUM> in response to the interference software mitigation being engaged.

The CEM <NUM> further detects changes in interference conditions, such as via the indicator signals <NUM>, <NUM>, <NUM> and instructs the AP <NUM> to disengage the interference mitigation, via a release mitigation signal <NUM>, when the interference is no longer present. In some embodiments, a change in the indicator signals <NUM>,<NUM>, <NUM> will trigger the AP to reevaluate if the interference is no longer present. Prior to removing the mitigation, the AP may apply a second holdoff timer to prevent mitigation thrashing scenarios that may occur with LMR scan or trunking mobility. At the completion of the second holdoff timer, the AP will remove the mitigation, thereby returning the first and second modems <NUM>, <NUM> to normal converged operation. For example, interference mitigation can be removed in response to a frequency change by one of the modems which negates the need for the interference mitigation.

In accordance with the embodiments, the interference mitigation may comprise one or more of: power reduction to the second modem; data throttling to the second modem; and/or band steering of the second modem. For example, for the LMR/LTE application, the interference mitigation may comprise one or more of: power reduction to the LTE modem, reducing data speed to the LTE modem, and/or band steering of the LTE modem. The band steering may be performed for example, through dynamically disabling certain LTE bands to steer the LTE modem to a non-interfering location.

While examples are provided which refer to LMR and LTE modems, it is to be appreciated that the embodiments can be applied beyond LMR and LTE operations. The use of the baseband processor <NUM> and the LMR modem <NUM> is particularly advantageous to public safety communication devices which support mission critical communications. Such devices rely on mission critical push-to-talk (PTT) and scan, hence the mitigation of interference from the LTE modem <NUM> is extremely important. The applications processor <NUM> and the LTE modem <NUM> provide a plurality of non-mission critical features such as text-to-speech, touch screen display features, BLUETOOTH, WiFi, and/or global positioning system (GPS) to name a few.

The portable communication device <NUM>, when operating using first and second frequency bands controlled by first and second modems is able to detect and mitigate interference generated by second modem transmit frequency bands conflicting with first modem receive bands, external RF transmissions interfering with the second modem, internal first modem transmissions interfering with the second modem, and second modem transmit frequency bands interfering with internally generated first modem transmissions. For example, the portable communication device <NUM>, when operating using LMR and LTE frequency bands controlled by LMR and LTE modems is able to detect and mitigate interference generated by: LTE transmit frequency bands conflicting with LMR receive bands, external LMR transmissions interfering with the LTE modem, internal LMR transmissions interfering with LTE modem, and LTE transmit frequency bands interfering with internally generated LMR transmissions.

To address the LTE transmit frequency bands conflicting with LMR receive bands and to address the LTE transmit frequency bands interfering with internally generated LMR transmissions, the mitigation approach comprises reducing power, and/or band steering, and/ or reducing data speed to the second modem in the manner described previously.

Examples of potential interference may include but are not limited to, the upper edge of LMR <NUM> band (<NUM> - <NUM>) which may be very close to the lower edge of LTE BAND <NUM> (Uplink <NUM> - <NUM>) resulting in out of band emissions interference when two transceivers are operating simultaneously. Another example, in which frequencies overlap are LMR <NUM> band (<NUM> - <NUM>) and LTE BAND <NUM> (Downlink <NUM> - <NUM>). The hardware mitigation provided by the CEM <NUM> to engage the attenuation switch <NUM> provides instantaneous interference protection while the software mitigation is executed. These software mitigations can take hundreds of milliseconds to enact, and relying on them without the hardware mitigation would result in degraded LMR scan and mobility operations.

To address internal or external LMR transmissions interfering with the LTE modem, the portable communication device <NUM> further comprises a radio frequency (RF) detector <NUM> operatively coupled to a receive input of the second antenna <NUM> for detecting unwanted RF signals associated with a specific LMR frequency range that can interfere with or cause damage to the LTE modem <NUM>. Although not shown, the RF detector <NUM> may interoperate with RF filtering and voltage reference circuits known in the field of RF detection. In the past, the presence of a strong unwanted RF signal to the second antenna <NUM> could have damaged the second modem <NUM> and/or cause interference to the second modem <NUM>. For example, the presence of a strong unwanted external LMR RF signal or internal inter-modulation artifacts being picked up by the second antenna <NUM> could have damaged the second modem <NUM> and/or cause interference to the second modem <NUM>. The RF detector <NUM>, in response to a strong unwanted signal, generates an external power detect signal <NUM> to the CEM <NUM> and to the AP <NUM>. The CEM <NUM>, in response to the external power detect signal <NUM>, drives the hardware attenuation signal <NUM> thereby enabling the attenuation switch <NUM> and disconnecting the LTE antenna from the LTE modem thereby protecting the second modem <NUM> from damage or interference. The switch <NUM> remains engaged until the external power detect signal <NUM> changes to an acceptable level as determined by the CEM <NUM>, thereby ensuring that the second modem <NUM> remains undamaged. For example, the presence of, a strong LMR signal at an LTE antenna is prevented from causing damage to the LTE modem by having the CEM maintain the attenuation switch engaged.

The coexistence module (CEM) <NUM> provided by the embodiments takes into account the currently active first and second modems and automatically applies respective mitigation only as needed under the predetermined scenarios of concern. Portable communication device <NUM> advantageously allows for fine adjustment of predetermined modem transceiver parameters such as power level and band operation. Implementation of the CEM <NUM> and attenuation switch <NUM> in hardware advantageously avoids substantial delays that would be experienced through a software only mitigation approach. In many cases, the dynamically changing nature of the communications protocol makes a software implementation impractical or unrealizable.

<FIG> is a flowchart of a method <NUM> for managing simultaneous modem operations in a portable communication device, such as the converged portable communication device <NUM> of <FIG>, in accordance with some embodiments. The method <NUM> has been illustrated in terms of LMR and LTE frequency bands, controlled by separate modems for ease of description, however it is to be appreciated that the method <NUM> is applicable to other modems operating simultaneously in frequency bands susceptible to interference.

The method begins at <NUM>, with simultaneous operation of first and second modems, such as first and second modems <NUM>, <NUM>, respectively operating on first and second frequency bands. For example, simultaneous LMR and LTE communications taking place using LMR and LTE modems <NUM>, <NUM> respectively, in a coexistence mode of the portable communication device <NUM>. When a change in frequency band operation takes place at <NUM>, for example a change in either LTE band operation and/or LMR TX/RX and/or LMR band operation, the method ensures operation of the first frequency band communications (LMR band) remains normal. At <NUM>, a check is made for detecting interference during the coexistence mode. For example, the method detects whether the LTE band operations have interfered with the LMR band operations.

When interference is detected at <NUM>, the method <NUM> proceeds by engaging an attenuation switch <NUM> to the antenna path of the second modem at <NUM> to temporarily negate second frequency band communications at <NUM>. For example, the attenuation switch <NUM> can be used to temporarily negate LTE communications, while the LMR modem which may be handling mission critical communications operates normally.

At <NUM>, the cause of interference is analyzed, by the applications processor <NUM> and a determination is made as to whether a mitigation action is possible. For example, the cause of interference may be analyzed by the AP and CEM of <FIG> as previously described. When a mitigation action is possible at <NUM>, the method <NUM> proceeds to a mitigation mode at <NUM>. The mitigation may be a software controlled mitigation comprising for example, reduced power to the second modem and/or reduced data speed to the second modem (the LTE modem) as determined at <NUM>. The software mitigation <NUM> may incorporate an optional holdoff timer as previously described to cater for LMR scan and mobility operations. When the applicable software mitigation has been completed at <NUM>, the method <NUM> proceeds by disengaging the attenuation switch at <NUM> and establishing communications using the applicable software mitigation thereby re-establishing coexistence operations at <NUM>. For example the LTE modem may operate at restricted power and/or speed while the LMR operations remain normal. Communications continue in the mitigated coexistence mode returning to <NUM> to await a frequency change or change in TX/RX state.

Returning back to <NUM>, when the cause of interference is analyzed and a determination is made that a software mitigation action is not possible, the method <NUM> returns back to <NUM> to await a frequency change or change in LMR TX/RX state. Here, the first frequency band communication, such as the LMR communication, operates normally while the second frequency band communication, such as LTE communications, has been negated at <NUM>.

Returning back to <NUM>, when interference is no longer detected in the mitigated coexistence mode, the attenuation switch is disengaged at <NUM>. The removal of software mitigation <NUM> may incorporate an optional holdoff timer as previously described to cater for LMR scan and mobility operations. Any previously applied software mitigation is removed at <NUM>, thereby allowing the second frequency band operations, such as the LTE band communications, to return to normal, non-mitigated operation at <NUM>, while returning to <NUM> to await changes in frequency change or change in LMR TX/RX state.

The method and apparatus provided herein have beneficially enabled coexistence by mitigating interference without infrastructure interaction. The method and apparatus advantageously allow for fine adjustment for specific transceiver parameters such as power level, data throttling, and band steering.

The mitigation approach advantageously focus on band edges and avoids the use of large filters that could result in increased insertion loss across the band, as well as the cost and size associated with such filters. Additionally, the mitigation approach avoids the use of a software-only approach that can take hundreds of milliseconds which would degrade LMR scan/mobility operations that can be on the order of <NUM>.

While the AP and BP have been described in terms of advantageously supporting converged operation of two different modems, for example the LMR modem and the LTE modem, it is also to be appreciated that the embodiments can be applied to communication devices having more than two processors supported more than two modems operating with nearby frequency bands that are susceptible to RF interference. As such the embodiments can be said to apply to a plurality of different modems supporting communication protocols operating over different but nearby frequency bands which are susceptible to interference with each other.

Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present teachings.

Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has," "having," "includes," "including," "contains," "containing" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises. a," "includes. a," or "contains. a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms "a" and "an" are defined as one or more unless explicitly stated otherwise herein. The terms "substantially," "essentially," "approximately," "about" or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within <NUM>%, in another embodiment within <NUM>%, in another embodiment within <NUM>% and in another embodiment within <NUM>%. The term "coupled" as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is "configured" in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

Claim 1:
A portable communication device (<NUM>), comprising:
a programmable logic array for operating as a coexistence module (<NUM>), CEM;
an applications processor (<NUM>), AP, operatively coupled to the CEM (<NUM>);
a baseband processor (<NUM>), BP, operatively coupled to the CEM (<NUM>);
a first modem (<NUM>) operatively coupled to the BP, the first modem (<NUM>) configured to operate using a first frequency band;
a second modem (<NUM>) operatively coupled to the AP (<NUM>), the second modem (<NUM>) configured to operate using a second frequency band;
the AP (<NUM>), the BP (<NUM>), and the first and second modems (<NUM>, <NUM>) configured to operate in a converged mode in which both the first and second modems (<NUM>, <NUM>) operate simultaneously;
an attenuation switch (<NUM>) operatively coupled to the CEM (<NUM>) and the second modem (<NUM>);
the BP configured to generate signals to the CEM (<NUM>) and to the AP (<NUM>) while the first modem (<NUM>) is transmitting and receiving on the first frequency band;
the second modem (<NUM>) configured to generate signals to the CEM (<NUM>) and to the AP (<NUM>) when the second modem (<NUM>) is transmitting and receiving on the second frequency band; and
the AP (<NUM>) and the CEM (<NUM>) configured to detect signals indicating interference between the first and second frequency bands and to determine a cause of interference as being one from a plurality of predetermined interference scenarios, the CEM (<NUM>) configured to engage the attenuation switch (<NUM>) to temporarily disconnect an antenna path of the second modem (<NUM>) and negate RF communications associated with the second modem (<NUM>) while the AP (<NUM>) configured to determine an applicable interference mitigation to counter the interference, the AP (<NUM>) configured to apply the interference mitigation to enable the second modem (<NUM>) to operate in a restricted mode; and
the AP (<NUM>) configured to generate a disengage signal to the CEM (<NUM>), and the CEM (<NUM>) configured to disengage the attenuation switch (<NUM>) in response thereto, thereby re-establishing converged operation during which the first modem (<NUM>) and second modem (<NUM>) operate simultaneously, the second modem (<NUM>) operating in the restricted mode.