System and method for dropping and adding an air interface in a wireless communication system

A device and method for dropping an air interface is disclosed. In one embodiment, the method comprises communicating over a first air interface and a second air interface, determining an operational parameter based at least in part on a characteristic of the first air interface, and dropping the second air interface based at least in part on the operational parameter. A device and method for adding an air interface is also disclosed. In one embodiment, the system comprises a processor configured to drop one of a plurality of concurrently established air interfaces and to subsequently determine that at least one predetermined criteria is met before attempting to add the air interface.

BACKGROUND

This disclosure relates to wireless communication.

2. Description of the Related Technology

Wireless communication systems exist which are capable of communicating over multiple air interfaces, but are not capable of concurrently communicating over multiple air interfaces. Thus, a need exists for wireless communication systems able to concurrently communicate over multiple air interfaces.

SUMMARY OF THE INVENTION

The system, method, and devices of the invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this invention provide advantages that include concurrent communication over multiple air interfaces.

One aspect of the disclosure is a method of dropping an air interface, the method comprising concurrently communicating over a first air interface and a second air interface, determining an operational parameter based at least in part on a characteristic of the first air interface, and dropping the second air interface based at least in part on the operational parameter.

Another aspect of the disclosure is a device for dropping an air interface, the device comprising a transceiver configured to concurrently communicate over a first air interface and a second air interface, and a processor configured to drop the second air interface based at least in part on an operational parameter, wherein the operational parameter is based at least in part on a characteristic of the first air interface.

Another aspect of the disclosure is a device for dropping an air interface, the device comprising means for concurrently communicating over a first air interface and a second air interface, means for determining an operational parameter based at least in part on a characteristic of the first air interface, and means for dropping the second air interface based at least in part on the operational parameter.

Still another aspect of the disclosure is a computer chip encoded with instructions for executing a method of dropping an air interface, the method comprising concurrently communicating over a first air interface and a second air interface, determining an operational parameter based at least in part on a characteristic of the first air interface, and dropping the second air interface based at least in part on the operational parameter.

One aspect of the disclosure is a method of adding an air interface, the method comprising dropping one of a plurality of concurrently established air interfaces, determining, after dropping the air interface, that at least one predetermined criterion is met, and adding the air interface after the determination.

Another aspect of the disclosure is device for adding an air interface, the device comprising a processor configured to drop one of plurality of concurrently established air interfaces and to subsequently determine that at least one predetermined criteria is met before attempting to add the air interface.

Another aspect of the disclosure is a device for adding an air interface, the device comprising dropping one of a plurality of concurrently established air interfaces, determining, after dropping the air interface, that at least one predetermined criterion is met, and adding the air interface after the determination.

Still another aspect of the disclosure is a computer chip encoded with instructions for executing a method of adding an air interface, the method comprising dropping one of a plurality of concurrently established air interfaces, determining, after dropping the air interface, that at least one predetermined criterion is met, and adding the air interface after the determination.

DETAILED DESCRIPTION

Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique. SC-FDMA has similar performance and essentially the same overall complexity as those of OFDMA system. SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. SC-FDMA has drawn great attention, especially in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of transmit power efficiency. It is currently a working assumption for uplink multiple access scheme in 3GPP Long Term Evolution (LTE), or Evolved UTRA.

FIG. 1is a diagram illustrating wireless communication devices engaged in simultaneous communication over two air interfaces. Each wireless communication device10can simultaneously establish a first air interface110and a second air interface120between itself and one or more access points130. In one embodiment, the first air interface110is established at a first channel defined by a first frequency or frequency band, whereas the second air interface120is established at a second channel defined by a second frequency or frequency band which is different from the first frequency or frequency band.

In one embodiment, the first air interface110supports 1xRTT traffic and the second air interface120supports EVDO traffic. 1xRTT, also known as 1x, 1xRTT, and IS-2000, is an abbreviation of 1 times Radio Transmission Technology. EVDO, abbreviated as EV or DO, is an abbreviation of Evolution-Data Only. Both 1xRTT and EVDO are telecommunications standards for the wireless transmission of data through radio signals maintained by 3GPP2 (3rdGeneration Partnership Project), which are considered types of CDMA2000 (Code Division Multiple Access 2000).

In other embodiments, the first air interface110or the second air interface120can support 1xAdvanced, DO (Release 0, Revision A or B), UMTS (HSPA+), GSM, GPRS, and EDGE technologies.

FIG. 2is a functional block diagram of a wireless communication device. The wireless communication device10includes a processor210in data communication with a memory220, an input device230, and an output device240. The processor is further in data communication with a modem250and a transceiver260. The transceiver260is also in data communication with the modem250and an antenna270. Although described separately, it is to be appreciated that functional blocks described with respect to the wireless communication device10need not be separate structural elements. For example, the processor210and memory220may be embodied in a single chip. Similarly, two or more of the processor210, modem250, and transceiver260may be embodied in a single chip.

The processor210can be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof designed to perform the functions described herein. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The processor210can be coupled, via one or more buses215, to read information from or write information to memory220. The processor may additionally, or in the alternative, contain memory, such as processor registers. The memory220can include processor cache, including a multi-level hierarchical cache in which different levels have different capacities and access speeds. The memory220can also include random access memory (RAM), other volatile storage devices, or non-volatile storage devices. The storage can include hard drives, optical discs, such as compact discs (CDs) or digital video discs (DVDs), flash memory, floppy discs, magnetic tape, and Zip drives.

The processor210is also coupled to an input device230and an output device240for, respectively, receiving input from and providing output to, a user of the wireless communication device10. Suitable input devices include, but are not limited to, a keyboard, buttons, keys, switches, a pointing device, a mouse, a joystick, a remote control, an infrared detector, a video camera (possibly coupled with video processing software to, e.g., detect hand gestures or facial gestures), a motion detector, or a microphone (possibly coupled to audio processing software to, e.g., detect voice commands). Suitable output devices include, but are not limited to, visual output devices, including displays and printers, audio output devices, including speakers, headphones, earphones, and alarms, and haptic output devices, including force-feedback game controllers and vibrating devices.

The processor210is further coupled to a modem250and a transceiver260. The modem250and transceiver260prepare data generated by the processor210for wireless transmission via the antenna270according to one or more air interface standards. For example, the antenna270may facilitate transmission over a first air interface110and a second air interface120. The modem250and transceiver260also demodulate data received via the antenna270according to one or more air interface standards. The transceiver can include a transmitter, receiver, or both. In other embodiments, the transmitter and receiver are two separate components. The transceiver260can include a first transceiver261aand a second transceiver261b. The modem250and transceiver260, can be embodied as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof designed to perform the functions described herein.

FIG. 2Bis a representational block diagram of air interface characteristics upon which an operational parameter may be based as described below. The air interface110has a number of characteristics, including a receive power291, a bit error rate292, a packet error rate293, a frame error rate294, a signal-to-noise ratio295, a signal-to-interference ratio296, and a signal-to-interference-plus-noise ratio297. An operational parameter may also be based on an interference power298at a frequency near the frequency at which communication over the air interface110occurs.

FIG. 3is a functional block diagram of a receiver of a wireless communication device.FIG. 3illustrates exemplary component which may be embodied in the transceiver260ofFIG. 2. A signal received on the antenna270is amplified by a low-noise amplifier310. Depending on the particular embodiment, the amplified signal is then pass through a SAW (surface acoustic wave) filter320. A SAW filter is an electromechanical device in which electrical signals are converted into a mechanical wave in a device constructed of a piezoelectric crystal or ceramic. The mechanical wave is delayed as it propagates across the device before being converted back into an electric signal by electrodes. The delayed outputs are recombined to produce a direct analog implementation of a finite impulse response filter. The signal is then multiplied by a center frequency at a multiplier330. The base-banded signal is then passed through an analog low-pass filter340, converted to a digital signal at an analog-to-digital converter350, and filtered once again with a digital low-pass filter360.

The signal is then split into multiple paths. Each path is multiplied by a different frequency at a multiplier370and passed through an appropriate filter380before being sampled with a sampler390. Further processing, including demodulation, equalization, deinterleaving, and error correction coding, can be performed in a processing module395or the modem250or processor210ofFIG. 2.

FIG. 4is a functional block diagram of a transmitter of a wireless communication device.FIG. 4illustrates additional exemplary components which may be embodied in the transceiver260ofFIG. 2. The function of the transmitter is similar to that of the receiver, but in reverse. In particular, data generated by the processor210ofFIG. 2may be subject to preliminary processing in a processing module495, the modem250or the processor210itself. The data for each channel is passed through an appropriate filter480before being modulated at a multiplier470. The modulated carriers are added together at an adder455before being converted into an analog signal at a digital-to-analog converter450. The analog signal is passed through an analog low-pass filter440before being modulated to a center frequency at a multiplier430. The modulated signal is optionally passed through a SAW filter420and a power amplifier410before being transmitter via the antenna270.

As described above with respect toFIG. 1, a wireless device10is capable of establishing a first air interface110and a second air interface120. Such a wireless device is able to support simultaneous voice and data services in which two different technologies (such as 1x and DO) are used at the same wireless device at the same time. Under certain scenarios, using shared resources to support two air interfaces results in performance degradation of one or more of the interfaces.

One scenario which may result in a degradation of performance is a large power imbalance between the two technologies. Due to many factors (loading, fading, shadowing, near/far problem, etc.), the transmit power and/or receiver power can be quite different for two supported interfaces. This imbalance can degrade one or more air interfaces due to mixer image noise, quantization noise, RPC resolution, emission, etc. This can effect both the forward link and reverse link.

Another scenario which may result in a degradation of performance is when the system is power-limited. Both air interfaces can share the same power amplifier, such as power amplifier410inFIG. 4, which can necessarily provide only a finite amount of transmit power. In marginal coverage areas, this power may not be enough to support two interfaces with reasonable performances for both interfaces. If the wireless device attempts to support both interfaces, performance will be degraded.

Yet another scenario which may result in a degradation of performance is when an in-band RF interferer is present. If a wireless device, such as the wireless device10ofFIG. 2, is communicating over two interfaces, it may be configured in a wideband mode. For example, if communication over the first air interface occurs at a first frequency and communication over the second air interface occurs over a second frequency, the transceiver may receive, and process these frequencies and those inbetween. If there is an RF interferer falling within this range, it may saturate the analog-to-digital converter, such as the analog-to-digital converter350ofFIG. 3, which results in performance degradation.

In order to avoid such performance degradation, one of the air interfaces can be dropped such that better performance is realized on the other air interface.FIG. 5is a flowchart illustrating a method of dropping an air interface. The process500, begins, in block510with concurrent communication over a first air interface and a second air interface. The first and second air interface can be an 1xRTT interface, an 1xAdvanced interface, a 1Xtreme interface, an EVDO interface, an EV-DV interface, a CDMA200 interface, a DO (Release 0, Revision A or B) interface, an UMTS (HSPA+) interface, a GSM interface, a GPRS interface, an EDGE interface, or any other interface known to those skilled in the art. The communication over the first and second air interface can be performed by the wireless device10ofFIG. 1. Alternatively, the communication can be performed by at least one of the processor210, modem250, transceiver260, or antenna270ofFIG. 2.

Next, in block520, an operational parameter is determined based at least in part on a characteristic of the first air interface. The operational parameter can be determined by the processor210with inputs from other components, including the antenna270or input device230. The operational parameter can include a power imbalance based on the receive power of the first air interface and the receive power of the second air interface. The operational parameter can include other metrics based on the receive power of the first air interface and/or receive power of the second air interface. The operational parameter can include a frame error rate of the communication over the first air interface. The operational parameter can include a bit error rate, a packet error rate, a signal-to-noise ratio, a signal-to-interference ratio, or a signal-to-interference-plus-noise ratio of the first air interface. The operational parameter can include an interference power at a frequency near the first frequency at which communication over the first interface occurs. The operational parameter can include the presence (or absence) or an RF interferer between a first frequency at which communication over the first air interface occurs and a second frequency at which communication over the second air interface occurs. The operational parameter can include any combination or calculation based on the above-mentioned characteristics or other measures.

In block530, it is determined whether or not to drop the second air interface based on the operational parameter. The determination to drop the second air interface can be performed by the processor210ofFIG. 2. This determination can include comparing the operational parameter to a threshold. This determination can include using more than one operational parameter to define a logical function resulting in a determination that the second air interface should be dropped (TRUE) or should not be dropped (FALSE).

If it is determined, in block530, that the second air interface should not be dropped, the process500returns to block510. Alternatively, the process500return to block520. If it is determined, in block530, that the second air interface should be dropped, the process500continues to block540where the second air interface is dropped.

A specific implementation of the process500ofFIG. 5is illustrated by the flowchart inFIG. 6. In particular,FIG. 6is a flowchart illustrating another method of dropping an air interface. In one embodiment of the process600, the second air interface will be dropped if the second air interface is in an idle state and there is either a power imbalance, an RF interferer present, or both. In this embodiment, the second air interface will also be dropped if the second air interface is in a traffic state, an error rate is too high, and there is either a power imbalance, an RF interferer present, or both. The process600reaches these results with the least number of redundant determinations.

The process600begins, in block610, with concurrent communication over a first and a second air interface. The process continues to block620where it is determined if there is a violation of a power constraint. In one embodiment, the violation of the power constraint is indicative of a power imbalance. In one embodiment, determining if there is a power imbalance includes a number of sub-steps. In one embodiment, the receive power of the first air interface is measured and then fed into a 1-tap IIR filter with a first time constant, where the first time constant is based on whether the first air interface is in an acquisition mode or a tracking mode. The receive power of the second air interface is also measured and fed into a 1-tap IIR filter with a second time constant, where the second time constant is based on whether the second air interface is in an acquisition mode or a tracking mode. Both of the filter outputs are converted into decibels (or another logarithmic measure) and the difference between the two is determined. If the absolute value of this difference is greater than a predefined threshold and less than both of the air interfaces (the first, the second, or neither) are in acquisition mode and less than both of the air interfaces are performing an off frequency search (OFS) or hard hand-off, it is determined that a power imbalance exists. Otherwise, it is determined that a power imbalance does not exist.

The process then continues to decision block630, which outputs to block640if the power constraint is violated and to block650if the power constraint is not violated. In block640, it is further determined if the second air interface is in an idle state or a traffic state. If the second air interface is in an idle state, the process bypasses further determination (as such determination would not affect the final result) and the second air interface is dropped in block695. If the second air interface is in a traffic state, the process bypasses determination of an RF constraint (as it would not affect the end result) and goes to block680.

As mentioned above, if the power constraint is not violated, the process continues to block650. In block650it is determined if an RF constraint is violated. This determination can be performed by an RF chip and be indicative of any reason to drop the second air interface. In one embodiment, violation of the RF constraint is indicative of the presence of an RF interferer, which can be detected at any frequency between the center frequencies of the first air interface and second air interface.

The process continues from block650to decision block660which outputs to block670if an RF interferer is present, but returns to block610otherwise. The process returns to block610as it determines that there is no violation of either the power constraint or the RF constraint. Further determination would not affect the final result so it is skipped. In block670, the system determines if the second air interface is in an idle state or a traffic state. If the second air interface is in an idle state, the process bypasses further determination (as such determination would not affect the final result) and the second air interface is dropped in block695. If the second air interface is in a traffic state, the process continues to block680.

At block680, reached if it is determined that there is a violation of either the power constraint or the RF constraint and that the second air interface is not in an idle state, a performance constraint of the first air interface is determined. In one embodiment, the performance constraint is violated if an error rate is too high. The error rate may, for example, be a frame error rate, a packet error rate, a bit error rate, a frame drop rate, etc. The frame error rate may be determined by checking if the frame passes a cyclic redundancy check (CRC). The frame error rate can also be filtered. A 1-tap IIR filter with a error rate time constant can be used.

The process600continues to block690where it is determined whether or not the performance constraint is violated. If it is determined that the performance constraint is violated, the process600continues to block695where the second air interface is dropped. Otherwise, the process600returns to block610.

The second air interface can be dropped, in block695, by storing a ConnectionFailure record with ConnectionFailureReason=‘0×1’ (Connection failure due to tune away) and/or by switching to a narrowband mode communicating only over the first air interface.

FIG. 7is a functional block diagram of a module for dropping an air interface. Such a module can be embodied in software, firmware, hardware, or some combination thereof. The module can be configured to perform at least one of the processes500,600described above with respect toFIGS. 5 and 6, respectively. The module700receives at least one operational parameter as an input, and can also receive one or more parameters such as a threshold or a time constant. The illustrated module700receives the receive power of the first air interface, the receive power of the second air interface, a measure of the first air interface's performance (such as an error rate), and a termination request from the RF chip (which may indicate the presence of an RF interferer). The illustrated module700also receives a power imbalance threshold, as described above with respect toFIG. 6. Output from the module700is a decision regarding whether the second air interface should be dropped. This decision can include instructions to drop a second air interface. This decision can also include information that the second air interface should not be dropped, or simply output nothing in the case that the second air interface should not be dropped.

After the second air interface is dropped, the wireless device may soon attempt to reinitialize (or add) the second air interface. If it is successful prior to a change a conditions, this will result in the second air interface being dropped once again. This process will result in the second air interface being dropped and added repeatedly, leading to a degradation in performance. Thus, when an air interface is dropped, it is precluded from being added until specific criteria are met.

FIG. 8is a flowchart illustrating a method for adding an air interface. The process800begins, in block810, by dropping a second air interface. This drop may be based, at least in part, on an operational parameter based on a characteristic of a first air interface. Such a result may occur in block540ofFIG. 5or block695ofFIG. 6, for example. The process800continues to decision block820, where it remains so long as the first air interface is in a traffic state. The first air interface may be in a traffic state if traffic is being communicated over channel. The first air interface may also be in a traffic state if traffic is expected to be communicated over the channel. For example, the channel may be reserved for traffic or non-continuous traffic may be transmitted. Determination that the first air interface is no longer in a traffic state may be based on the non-detection of traffic for a predetermined time. Once the first air interface is no longer in a traffic state, the process800continues to block830where establishment of the second air interface is initiated.

FIG. 9is a flowchart illustrating a method for adding an air interface based on a timer. The process900begins, in block910, by dropping a second air interface. This drop may be based, at least in part, on an operational parameter based on a characteristic of a first air interface. The process900continues to block920where a timer is set to zero and started.

Next, in decision block930, it is determined if the first air interface is in a traffic state. The first air interface may be in a traffic state if traffic is being communicated over channel. The first air interface may also be in a traffic state if traffic is expected to be communicated over the channel. For example, the channel may be reserved for traffic or non-continuous traffic may be transmitted. Determination that the first air interface is no longer in a traffic state may be based on the non-detection of traffic for a predetermined time. If the first air interface is not in a traffic state, the timer is not used and the process continues to block950where establishment of the second air interface is initiated. If the first air interface is in a traffic state, the process continues to decision block940where the time from the timer is compared to a threshold. If the time from the timer is greater than a threshold, the process continues to block950where establishment of the second air interface is initiated. Thus, the second air interface can be added after a drop if at least one of the following is true: (1) the first interface is not in a traffic state or (2) a predetermined time has passed. If neither of these is true, the process returns to decision blocks930and940until one of them is true and the second air interface can be added again.

FIG. 10is a flowchart illustrating a method for adding an air interface based on measuring a channel. The process1000begins, in block1010, by dropping a second air interface. This drop may be based, at least in part, on an operational parameter based on a first air interface. The process1000continues to block1020where a channel is measured. The channel can be measured in the process of communicating over the first air interface, or by using alternate resources not in use by either the first air interface or the second air interface.

Next, in decision block1030, it is determined if the first air interface is in a traffic state. The first air interface may be in a traffic state if traffic is being communicated over channel. The first air interface may also be in a traffic state if traffic is expected to be communicated over the channel. For example, the channel may be reserved for traffic or non-continuous traffic may be transmitted. Determination that the first air interface is no longer in a traffic state may be based on the non-detection of traffic for a predetermined time. If the first air interface is not in a traffic state, the channel measurement is moot and the process continues to block1050where establishment of the second air interface is initiated. If the first air interface is in a traffic state, the process continues to decision block1040where the channel measurement is used to determine if the channel is “good.”

In one embodiment, the channel is good if the signal-to-noise ratio is above a predetermined threshold. If it is determined that the channel is good, the process continues to block1050where establishment of the second air interface is initiated. Thus, the second air interface can be added after a drop if at least one of the following is true: (1) the first interface is not in a traffic state or (2) a channel measurement indicates that the second air interface can be added. If neither of these is true, the process returns to decision blocks1030and1040until one of them is true and the second air interface can be added again.

Although three criteria are discussed above with respect toFIGS. 8, 9, and10, other criteria could be used to determine if a dropped air interface should be added. For example, if the second air interface was dropped due to a lack of adequate power, a drop in transmit power of the first air interface may indicate that the second air interface can be added.

FIG. 11is functional block diagram of a module for adding an air interface. Such a module can be embodied in software, firmware, hardware, or some combination thereof. The module can be configured to perform at least one of the processes800,900,1000described above with respect toFIGS. 8, 9, and 10, respectively. The module1100can receive a first interface status indicating whether or not the first air interface is in a traffic mode, the output from a timer, and/or a channel measurement. The module1100can also receive a timing threshold or other thresholds. Output from the module700is a decision regarding whether the second air interface could be added. This decision can include instructions to add a second air interface. This decision can also include information that the second air interface should not be added, or simply output nothing in the case that the second air interface should not be added.