Abstract:
A method of adapting a transceiver includes receiving a signal at a time instant by the transceiver, determining if the transceiver is transmitting at the time instant, selectively updating one two signal quality measurements based on the transmission determination, evaluating a difference between the two signal quality measurements and adapting an operating mode of the transceiver based on the evaluation

Description:
TECHNICAL FIELD  
       [0001]    The invention relates generally to a mobile terminal, and more particularly, to methods and apparatus for improving the terminal performance. 
       BACKGROUND  
       [0002]    Power is a limited resource in a mobile terminal. As a result, methods for reducing the power consumption of the mobile terminal are highly desirable. One such approach is to adapt the radio receiver in situations with good signal conditions. A reduction in the low noise amplifier/mixer (LNA) linearity requirements by changing the bias current could significantly reduce the power consumption in the radio receiver. However, reduced linearity increases the risk of inter-modulation (IM) products (such as interference) leaking into the receive band. Of particular importance in this respect is the nonlinear mixing of the strong transmitted signal from the device&#39;s own transmitter and a strong interferer located at the half the duplex distance or twice the duplex distance. 
         [0003]    In some bands, the problem with IM products is larger than in other bands. Full Duplex (FD) operation (i.e. simultaneous transmission and reception) provides large throughput. However, due to TX/RX duplex separation and the presence of an interferer at twice the duplex distance (or half the duplex distance), half duplex (HD) (i.e. non-simultaneous transmission and reception) in some instances provides a larger practical throughput. Using HD at all times (i.e. reducing the max UL and DL rate by half in theory) can be too conservative since the interfering scenarios are typically not static. 
         [0004]    An example of a potential strong interferer occurring at twice the duplex distance from the receive channel is when Band 7 (2500-2570 MHz for UL and 2620-2690 MHz for DL) is used for FD. The potential strong interferer can, in this case, be a Bluetooth or a WLAN transmitter using the ISM band (2400-2483.5 MHz). For Band 7, the duplex distance is 120 MHz. If, for instance, the UL is centered at 2540 MHz, the DL will be centered at 2660 MHz. If, at the same time, a WLAN transmitter is using a channel around 2420 MHz, this could result in IM products at 2660 MHz (i.e., in the receive band). 
         [0005]    Methods exist for adaptation of LNA/Mixer linearity based on only received in-band signal-interference-ratio (SIR) or received in-band signal level. However, these methods do not take into account the state of terminal transmission. For instance, in LTE, the reception and transmission at a certain time instant are independent of each other (a correlation does, however, exist between RX @ t and TX @ t+4 ms and vice versa). Scenarios exist where either TX or RX or both TX and RX are on at the same time. Therefore, only looking into the average in-band SIR or signal level, without considering whether the device itself is transmitting will not accurately capture the problem with IM. 
         [0006]    A need exists, therefore, for methods and apparatus that take into account the operational state of the terminal in adapting transceiver performance. 
       SUMMARY  
       [0007]    It should be emphasized that the terms “comprises” and “comprising”, when used in this specification, are taken to specify the presence of stated features, integers, steps or components; but the use of these terms does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 
         [0008]    In exemplary embodiments, the foregoing and other objects are achieved in methods, systems, and apparatuses for adapting a transceiver in a mobile communication terminal. 
         [0009]    According to one exemplary embodiment, a method of adapting a transceiver includes receiving a signal at a time instant by the transceiver, determining if the transceiver is transmitting at the time instant, selectively updating one of two signal quality measurements based on the transmission determination, evaluating a difference between the two signal quality measurements and adapting an operating mode of the transceiver based on the evaluation. 
         [0010]    According to another exemplary embodiment, a transceiver in a mobile communications terminal includes a low noise amplifier for amplifying weak received signals, a detector for detecting received signals, a signal quality estimating module for estimating a received signal quality and a control unit. The control unit determines if the transceiver is transmitting at a time instant during which the signal is received, selectively updates one of least two signal quality measurements based on the transmission determination, evaluates a difference between the two signal quality measurements and adapts an operating mode of the transceiver based on the evaluation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]    The objects and advantages of the invention will be understood by reading the following detailed description in conjunction with the drawings in which: 
           [0012]      FIGS. 1 to 3  illustrate methods in accordance with exemplary embodiments; and 
           [0013]      FIG. 4  illustrates an exemplary transceiver in a mobile communication device. 
       
    
    
     DETAILED DESCRIPTION  
       [0014]    The various features of the invention will now be described with reference to the figures, in which like parts are identified with the same reference characters. 
         [0015]    The various aspects of the invention will now be described in greater detail in connection with a number of exemplary embodiments. To facilitate an understanding of the invention, many aspects of the invention are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., analog and/or discrete logic gates interconnected to perform a specialized function), by one or more processors programmed with a suitable set of instructions, or by a combination of both. The term “circuitry configured to” perform one or more described actions is used herein to refer to any such embodiment (i.e., one or more specialized circuits and/or one or more programmed processors). 
         [0016]    Moreover, the invention can additionally be considered to be embodied entirely within any form of computer readable carrier, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein. Thus, the various aspects of the invention may be embodied in many different forms, and all such forms are contemplated to be within the scope of the invention. For each of the various aspects of the invention, any such form of embodiments as described above may be referred to herein as “logic configured to” perform a described action, or alternatively as “logic that” performs a described action. 
         [0017]    A typical transceiver within a mobile terminal or mobile device is illustrated in  FIG. 4 . Transceiver  400  includes an antenna  405 . In the receive path, transceiver  400  may include low noise amplifier  410  for amplifying weak received signals, local oscillator  415  for mixing down received radio frequency signals to baseband signals, low pass filter  420 , analog to digital converter  425  and detector  430  for detecting the received signal (i.e. demodulation and decoding). In the transmit path, transceiver  400  may include coder  445 , digital to analog converter  450 , low pass filter  455 , local oscillator  460  and amplifier  465 . Transceiver may also include signal quality module  435  and control unit  440 . Signal quality module  435  can estimate or measure the received signal quality. Control unit  440  may have knowledge of transmission (i.e. when transmission takes place for example) and can receive the signal quality information from module  435 . Control unit  440  can control the local oscillators  415  and  460 , low noise amplifier  410  and amplifier  465 . Control unit  440  can adapt or switch an operating mode of the transceiver by, for example, controlling the bias of the amplifier  465  to reduce power consumption. 
         [0018]    According to exemplary embodiments, a transceiver may estimate the received signal quality. The signal quality may be a signal-to-noise-ratio (SNR) or a signal-to-interference-ratio (SIR) on a pilot signal. The signal quality may also be a block error rate (BLER) on a data or control channel. 
         [0019]    The signal quality estimates may be grouped based on whether the transmitter was enabled or disabled at the time instant when the signal was received. Therefore, a first received signal quality may be estimated in sub frames (slots) when the transmitter is enabled and a second received signal quality may be estimated in sub frames (slots) when the transmitter is disabled. 
         [0020]    A transmitter (within the mobile terminal) may be considered to be enabled when the transmitted power (i.e. the power level at which transmission takes place) is above a (pre-determined) power threshold and the transmitter may be considered to be disabled when the transmitted power is below the power threshold. 
         [0021]    The differences between the grouped signal quality estimates (i.e. between those corresponding to when the transmitter is enabled and to when the transmitter is disabled) may be utilized to adapt the transceiver unit. In a first embodiment, the adaptation may be made between different power consuming modes of the transceiver such as, for example, different bias current in the LNA/Mixer stage. In another embodiment, the adaptation may be made between operating the transceiver in a half duplex (operating) mode or in a full duplex (operating) mode in which a signalling procedure between the transceiver unit and a remote node is included. 
         [0022]    A method in accordance with exemplary embodiments in the form of a flow chart is illustrated in  FIG. 1 . The transceiver is in connected mode and connected to a remote node such as to a base station operating in a mobile communication system. In this exemplary embodiment, the transceiver may be operating in a low power transceiver mode. In this mode, the front end components such as the LNA and/or the mixer are in a low power mode with a lower linearity than in the high power mode (with a higher linearity). 
         [0023]    The transceiver may receive a signal at time t=T (at step  110 ). The transceiver may determine whether a transmission (from the mobile terminal) occurred at time T ( 120 ). If there was a transmission at T (“yes”), a first (received) signal quality measurement Q 1  may be updated based on the last received sample (i.e. received at t=T) ( 130 ). If there was no transmission at T (“no”), a second (received) signal quality measurement Q 2  may be updated based on the last received sample ( 140 ). The first signal quality measurement or estimate may correspond to when transmission takes place and the second signal quality measurement or estimate may correspond to when transmission does not take place. 
         [0024]    As described above, the transmitter may be considered to be enabled if the transmitted power is above a power threshold and the transmitter may be considered to be disabled when the transmitted power is below the power threshold. The threshold may be designated as “X” as illustrated in  FIG. 1 . The threshold can, for example, be −20 dBm. The first and second received signal quality estimates Q 1  and Q 2  could be, for example: a Block Error rate/estimate of a data channel or a control channel such as the PDCCH in LTE, or a SNR/SIR on a pilot signal such as the CPICH in WCDMA or Reference Signals in LTE for example. The reception quality measurements can be filtered in time over a number of received pilot symbols, data channel or control channel samples in order to improve the estimates. 
         [0025]    A control unit determines whether the reception quality difference between Q 2  and Q 1  is larger than a threshold designated by “Y” ( 150 ). If the difference is larger than the threshold, this indicates that the transmitter, due to inter-modulation products with another signal, is causing interference to the received signal. A control unit then adapts the transceiver mode to a high power operating mode with larger linearity requirement on the LNA/Mixer ( 160 ). If the difference is equal to or below the threshold, this may indicate that the interference is not an issue and the transceiver mode may be maintained at the low power operating mode (i.e. without switching to a high power operating mode). In comparing the quality estimates, the Q 1  that is being compared to Q 2  is the same measure; that is, both Q 1  and Q 2  may be one of BLER, SNR and SIR. What is being compared is the same quality measure accumulated over a period between when the transceiver is being transmitted and when the transceiver is not transmitting. 
         [0026]    In the embodiment described above, the two metrics (i.e. transmission enablement and difference between reception quality estimates) were used to determine that IM was a problem. This could not have been determined if only the average (averaged over both when transmitting and not transmitting) quality measure had been used. 
         [0027]    In other embodiments, the control unit does not automatically change to high power operating modes (unconditionally). The control unit decides on low power operating mode or high power operating mode based on having prior knowledge of a transmission that may take place. In LTE for example, the terminal knows 4 ms or 4 subframes in advance whether (or not) transmission will take place. In this manner, the high power operating mode will not be unnecessarily used which results in saving power. The transmission information need to be made (available to the transceiver) sufficiently in advance to allow the receiver to adapt he operating modes. 
         [0028]    Additional embodiments may include switching between duplex modes as illustrated in  FIGS. 2 and 3 . The transceiver may be operating in a full duplex mode ( 200 ). That is, the transceiver may be simultaneously transmitting and receiving data ( 200 ). The process steps  210 - 250  correspond to process steps  110 - 150  described above with respect to  FIG. 1 . 
         [0029]    A control unit determines whether the reception quality difference between Q 2  and Q 1  is larger than a threshold designated by “Y” ( 250 ). If the difference is larger than the threshold, this indicates that the transmitter, due to inter-modulation products with another signal, is causing interference to the received signal. A control unit then adapts the connection (from a full duplex connection) to a half duplex connection ( 260 ). That is, a connection where the transceiver does not transmit and receive at the same time. 
         [0030]    Typically, the change of operation mode to half duplex mode needs interaction with the remote node. An exemplary method of switching from full duplex operating mode to half duplex operating mode (corresponding to step  260  of  FIG. 2 ) in cellular systems such as LTE is illustrated in  FIG. 3 . The transceiver is in connection with the remote node in full duplex operation (corresponding to step  205  of  FIG. 2 ). Based on the comparison at step  250 , if the difference between Q 2  and Q 1  is greater than threshold “Y”, the transceiver unit transmits a connection release message to remote unit such as a base station according to protocols used by the system ( 310 ). 
         [0031]    Once the connection is terminated, the transceiver initiates a connection setup (according to protocols for the current system) during which the remote node is informed that the transceiver is functioning in a half duple operating mode ( 320 ). Upon establishing the connection, further communication between the transceiver and the remote node takes place in half duplex operation ( 330 ). 
         [0032]    In another embodiment (not illustrated), the change from a full duplex operating mode to a half duplex operating mode may also be made by explicit signalling during the ongoing connection without the connection release and connection setup steps. 
         [0033]    In newer 3GPP releases of LTE and HSPA, multiple component carrier transmission and reception is allowed. In Release 11 and onwards, non-contiguous reception and transmission may be realized. Exemplary embodiments may also be extended to these cases. 
         [0034]    The various process steps illustrated according to exemplary embodiments in  FIGS. 1-3  may be performed by at least some of the components illustrated in transceiver  400  of  FIG. 4 . For example, signal quality module  435  can estimate the signal quality. Control unit can have knowledge of when transmission takes place. Control unit  460  can update the reception quality measures, Q 1  and Q 2  and compare the difference in signal quality with the threshold. Control unit  460  can adapt the operating mode by, for example, adjusting the low noise amplifier  410  and/or power amplifier  465 . The control unit can be a general purpose processor that may be adapted to at least perform the particular functions highlighted above. 
         [0035]    A number of advantages may be realized by exemplary embodiments. By monitoring the received signal quality dependent on whether the transmitter is enabled or disabled, indication of possible transmitter impact, for instance IM products, on the received signal can be determined. Then, an appropriate transceiver action can be taken to prevent or reduce the transmitter impact on the received signal. A more robust and an improved communication may be achieved as a result. 
         [0036]    The invention has been described with reference to particular embodiments. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the embodiment described above. The described embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, rather than the preceding description, and all variations and equivalents which fall within the range of the claims are intended to be embraced therein.