GB2460112A - Controlling transmission diversity by delaying a signal on a second transmit path relative to a first transmit path - Google Patents

Controlling transmission diversity by delaying a signal on a second transmit path relative to a first transmit path Download PDF

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Publication number
GB2460112A
GB2460112A GB0809077A GB0809077A GB2460112A GB 2460112 A GB2460112 A GB 2460112A GB 0809077 A GB0809077 A GB 0809077A GB 0809077 A GB0809077 A GB 0809077A GB 2460112 A GB2460112 A GB 2460112A
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United Kingdom
Prior art keywords
signal
transmit path
apparatus
delay
power
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GB0809077A
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GB0809077D0 (en
Inventor
Marko Leinonen
Seppo Rousu
Juha Valtanen
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Nokia Oyj
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Nokia Oyj
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Priority to GB0809077A priority Critical patent/GB2460112A/en
Publication of GB0809077D0 publication Critical patent/GB0809077D0/en
Publication of GB2460112A publication Critical patent/GB2460112A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0667Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
    • H04B7/0671Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different delays between antennas

Abstract

A communications apparatus 101, e.g. a mobile device supporting multiple transmission antennas 20, 46, comprising a first transmit path 111 configured to receive a first signal and provide a first output signal and a second transmit path 113 configured to receive the first signal and provide a second output signal. The second transmit path 113 comprises at least one delay element (66 fig.4-8) configured to receive and delay at least a portion of the first signal. The apparatus 101 may further comprise a processor 105, which is configured to control the distribution of power of the first signal to the delay element, the delay of the delay element and/or the gain of the second transmit path. A power divider and/or power combiner may be adjustable in response to a control signal provided by a sensor 90 (fig.4-8).

Description

APPARATUS

Field of the Invention

The present invention relates generally to apparatus for communications, and more specifically to a transmitter/receiver apparatus, and in particular but not exclusively to an apparatus for use in a mobile device supporting multiple transmission antennas

Background

A communication device can be understood as a device provided with appropriate communication and control capabilities for enabling use thereof for communication with others parties. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. A communication device typically enables a user of the device to receive and transmit communication via a communication system and can thus be used for accessing various service applications.

A communication system is a facility which facilitates the communication between two or more entities such as the communication devices, network entities and other nodes. A communication system may be provided by one or more interconnect networks. One or more gateway nodes may be provided for interconnecting various networks of the system. For example, a gateway node is typically provided between an access network and other communication networks, for example a core network and/or a data network.

An appropriate access system allows the communication device to access to the wider communication system. An access to the wider communications system may be provided by means of a fixed line or wireless communication interface, or a combination of these. Communication systems providing wireless access typically enable at least some mobility for the users thereof. Examples of these include wireless communications systems where the access is provided by means of an arrangement of cellular access networks. Other examples of wireless access technologies include different wireless local area networks (WLANs) and satellite based communication systems.

A wireless access system typically operates in accordance with a wireless standard and/or with a set of specifications which set out what the various elements of the system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely user equipment, is provided with a circuit switched bearer or a packet switched bearer, or both.

Communication protocols and/or parameters which should be used for the connection are also typically defined. For example, the manner in which communication should be implemented between the user equipment and the elements of the networks and their functions and responsibilities are typically defined by a predefined communication protocol.

In the cellular systems a network entity in the form of a base station provides a node for communication with mobile devices in one or more cells or sectors. It is noted that in certain systems a base station is called Node B'. Typically the operation of a base station apparatus and other apparatus of an access system required for the communication is controlled by a particular control entity. The control entity is typically interconnected with other control entities of the particular communication network. Examples of cellular access systems include Universal Terrestrial Radio Access Networks (UTRAN) and GSM (Global System for Mobile) EDGE (Enhanced Data for GSM Evolution) Radio Access Networks (GERAN).

A non-limiting example of another type of access architectures is a concept known as the Evolved Universal Terrestrial Radio Access (E-UTRA). This is also known as Long term Evolution UTRA or LIE. An Evolved Universal Terrestrial Radio Access Network (E-UTRAN) consists of E-UTRAN Node Bs (eNBs) which are configured to provide base station and control functionalities of the radio access network. The eNBs may provide E-UTRA features such as user plane radio link control/medium access control/physical layer protocol (RLC/MAC/PHY) and control plane radio resource control (RRC) protocol terminations towards the mobile devices.

Figure 1 shows a prior art transceiver such as may be implemented in a contemporary mobile terminal. The illustrated transceiver is a (MISO) Multiple Input Single Output transceiver, and has two antennas that are used to receive signals, but only a single antenna is used as a transmit antenna.

In the circuit of Figure 1, a Transmitter 10 is coupled to a digital to analog converter (DAC) 12. The output of the DAC 12 is coupled to a first Mixer 14 which also receives a mixing frequency from Oscillator 22. The output of the first Mixer 14 is the upconverted transmission signal which is applied to Amplifier 16, where the signal is amplified ready for transmission. The amplified transmission signal is then coupled to the antenna 20 through duplexer 18.

The antenna 20 also receives a signal, and this signal is separated from the transmitted signal in Duplexer 18. The received signal is then amplified in low noise amplifier (LNA) 32 before being downconverted to base band in second Mixer 30.

The second mixer 30 receives the mixing frequency from Oscillator 24. The downconverted received signal is then digitized in analog to digital converter 28 and the digitized signal is coupled to first Receiver 26 where the signal may be decoded.

The circuit further comprises a further antenna 46 which will also receive signals for the device. The signals received by the second antenna 46 are coupled to channel filter 44 and the filtered signal is coupled to a further LNA 42. The amplified signal output by further LNA 42 is coupled to third Mixer 40 where the signal is downconverted to baseband, using a frequency supplied by third oscillator 38. The downconverted signal may then be digitized in further ADC 36, and the digitized signal coupled to second Receiver 34 where the signal may then be decoded.

Thus in the circuit of Figure 1, receive signal diversity is achieved, but as only a single transmitter is used, there is no opportunity to provide a transmission diversity in the transmit signal.

While only a single transmit/receive branch has been shown for each antenna, it should be remembered that the described system would commonly comprise both In-phase and Quadrature-phase channels in each branch.

Figure 2 shows a circuit for a proposed transceiver capable of transmission diversity operation. The circuit and operation of the transmitter 10, and receiver 26 connected to first antenna 20 is identical to that described above in relation to Figure 1.

However, in Figure 2, the circuit connected to second antenna 46 further comprises a second transmitter chain, comprising: transmitter 48, second DAC 50, fourth Mixer 52 and second amplifier 56. In place of channel filter 44, a second Duplexer 58 is provided in order to couple both transmit and receive branches to second antenna 46.

By controlling the first 10 and second 48 transmitters independently to transmit the same signal at different times, time diversity may be achieved in the transceiver of Figure 2.

However, the presence of two transmit chains significantly increases the complexity of the device over the contemporary device shown in Figure 1.

Furthermore, the presence of two transmit amplifiers 16 and 56 means that the transmit power required will typically be double of that required of the device shown in Figure 1 if each amplifier is considered to output roughly the same amount of power. This is a particular problem in relation to handheld or mobile terminals, since each power amplifier will consume a certain amount of current, which may lead to the talk or operational time of the terminal being dramatically reduced.

Alternatively, even for fixed location transmitters (such as base transceiver stations) although the problem of power consumption is not as significant the operation of two amplifiers and the higher power dissipation associated with operating two separate power amplifiers will produce problems such as heat dissipation and may limit the use of power amplifiers or require significant heat management apparatus to be employed to disperse the heat generated.

It is an aim of some embodiments of the present invention to address, or at least mitigate, some of these problems.

Summary

According to a first aspect of the invention, there is provided an apparatus comprising a first transmit path configured to receive a first signal and provide a first output signal, a second transmit path configured to receive the first signal and provide a second output signal, wherein the second transmit path comprises at least one delay element configured to receive and delay at least a portion of the first signal.

Thus in embodiments of the invention it may be possible to reduce power consumption and reduce heat production by operating a single amplifier in a more optimal high power range and controlling the transmission diversity by delaying the signal on the second transmit path using the delay element relative to the signal on the first transmit path.

The second transmit path may further comprise a power divider having a first output coupled to said delay element and a second output coupled to a delay element bypass, said power divider configured to receive said first signal.

The power divider may be adjustable to adjust the proportion of input power on each output.

The power divider is preferably a switch configured to select either the delay element bypass or the delay element.

The second transmit path may further comprise a power combiner having a first input coupled to said delay element and a second input coupled to the delay element bypass.

The power combiner may adjustable to adjust the proportion of output power from each input.

The power combiner may be a further switch.

The apparatus may further comprise a sensor, wherein at least one of said power divider and said power combiner is adjustable in response to a control signal provided by said sensor.

The second transmit path may further comprise a first switch having an input configured to receive said first signal, wherein said first switch is controllable between a first position wherein a signal is connected to said delay element, and a second position wherein said delay element is bypassed.

The second transmit path may further comprise a second switch having an output configured to provide said second output signal, wherein said second switch is controllable between a first position wherein a signal is received from said delay element, and a second position wherein said delay element is bypassed.

The first transmit path may further comprise a transmitter, wherein at least one of said first and second switches are controlled in dependence on a control signal provided by said transmitter.

The apparatus may further comprise a sensor, wherein at least one of said first and second switches may be controlled in dependence on a control signal provided by said sensor.

The first transmit path may further comprise a first amplifier configured to provide said first signal.

The first transmit path may further comprise a second amplifier coupled between said first amplifier and an output of said first transmit path; wherein an input of said second transmit path is coupled to an output of said first amplifier and an input of said second amplifier.

The second transmit path may further comprise a variable gain element configured to receive said first signal.

The variable gain element may be configured to be controllable in dependence on one or more control signals provided by at least one of: a first transmitter, a first receiver, and a second receiver.

The delay element may be configured to be adjustable such that the delay provided by the delay element may be controlled.

The adjustable delay element may be controlled in dependence on one or more control signals provided by at least one of: a transmitter, a first receiver, and a second receiver.

According to a second aspect of the invention, there is provided a method comprising receiving a first signal at a first transmit path, providing a first output signal from the first transmit path, receiving the first signal at a second transmit path, and delaying at least a portion of the first signal to generate a second output signal.

The method may further comprise dividing the first signal received at the second transmit path in a power divider to provide said at least a portion of the first signal, wherein the remainder of said first signal received in the second transmit path is bypassed around said delaying.

The dividing the first signal received may comprise adjusting the proportion of first' signal delayed.

The dividing the first signal received at the second transmit path may comprise switching the first signal to either be delayed or bypassed.

The method may further comprise combining said delayed signal with said bypassed signal in a power conbiner.

The method may further comprise providing a control signal to control at least one of the power divider and the power combiner.

The method may further comprise sensing and wherein at least one of the dividing and the combining is dependent on the sensing.

The method may further comprise amplifying or attenuating said first signal received at the second transmit path in a variable gain element.

The method may further comprise controlling at least one of: the distribution of the portion of the first signal to be delayed; the delay period of the delay; and the amplification gain of the second transmit path. According to a further aspect of the invention, there is provided a chipset comprising the apparatus as described above.

According to a further aspect of the invention, there is provided an electronic device comprising the apparatus as described above.

According to a further aspect of the invention, there is provided a computer program code means adapted to perform any of the steps of the method as described above, when the program is run on a processor.

According to a further aspect of the invention, there is provided an apparatus comprising first transmit means for receiving a first signal and providing a first output signal, second transmit means for receiving the first signal and providing a second output signal, wherein said second transmit means comprises at least one delaying means for receiving and delaying at least a portion of the first signal.

Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying Figures, in which:

Figure 1 shows a prior art transceiver;

Figure 2 shows a further prior art transceiver;

Figure 3 shows a schematic view of a transceiver within which embodiments of the invention may be employed; Figure 4 shows a schematic view of a circuit in accordance with an embodiment of the invention as shown in figure 3; Figure 5 shows a schematic view of a circuit in accordance with a further embodiment of the invention as shown in figure 3; Figure 6 shows a schematic view of a circuit in accordance with a further embodiment of the invention as shown in figure 3; Figure 7 shows a schematic view of a circuit in accordance with a further embodiment of the invention as shown in figure 3; Figure 8 shows a circuit in accordance with a further embodiment of the invention; and Figure 9 illustrates a method in accordance with one embodiment of the invention.

Detailed Description of Embodiments

Embodiments of the invention are described herein by way of particular examples and specifically with reference to exemplary embodiments. It will be understood by one skilled in the art that the invention is not limited to the details of the specific embodiments given herein.

Throughout the specification, when referring to the Figures, like numbers are used to identify the same components when present in each of the described embodiments.

With respect to figure 3, a schematic view of a transceiver capable of implementing embodiments of the invention is shown. The transceiver or apparatus 101 may be any apparatus configured to transmit and receive wireless communications. In some embodiments of the invention the apparatus may be part of a user equipment for example a mobile communications device, mobile phone, or portable communications device. Other embodiments of the invention may implement the apparatus as part of a base transceiver station (BTS) otherwise known as a node B (NB) in third generation mobile communications systems, or an enhanced node B (eNB).

The apparatus 101 comprises a processor 105 configured to control the transceiving process. The processor 105 may in some embodiments of the invention be a digital signal processor. In other embodiments of the invention the processor 105 may be one or more of the following: a signal generating processor; a signal detection processor; and an application software processor.

The processor 105 may be connected to the main receiver unit (main RX unit) 109, main transmitter unit (main TX unit 111), diversity transmitter unit (diversity TX unit) 113 and diversity receiver unit (diversity RX unit) 115 and control each of the units to perform their transmitting and receiving tasks as described below.

The processor 105 may be connected to a user interface 103 configured to enable a user to communicate with the transceiver. In some embodiments of the invention the user interface 103 may be a keypad for data entry. In some embodiments of the invention the user interface may be a display for displaying information for the user.

In some embodiments of the invention the user interface may be a speaker/microphone arrangement for receiving and transmitting audio information to and from the apparatus.

in other embodiments of the invention any suitable user interlace 103 implementatIon may be used.

The apparatus 101 may further comprise memory 107 connected to the processor 105 for storing information required by the transceiver apparatus.

The apparatus 101 may further comprise a main receiver unit 109 configured to be the receiver connected to a first antenna unIt 20 via a first duplexer 18.

The apparatus 101 may further comprise a main transmitter unit 111 configured to be the transmitter connected to the first antenna unit 20 vIa the first duplexer 18.

The apparatus 101 may further comprise a diversity receiver unit 115 configured to bethe recelverconnectedto asecond antenna unlt48vlaa second duplexers8.

The apparatus 101 may further comprise a diversity transmitter unit 113 configured to be the transmitter connected to the second antenna unit 46 vIa the second duplexer 58. The diversity transmitter unit 113 is further configured to be connected to the output of the first transmitter unit 111. The operation and configuration of the diversity transmitter unit 113 in various embodiments of the Invention will be described In further detail below.

In some embodiments of the Invention as described hereafter the apparatus may further comprise a sensor 60 whIch Is connected In some embodiments to the processor 105 and In other embodiments connected directly to the diversity transmitter unit 113. ThIs is shown in figure 3 by the dashed box and the dashed connection lines from the sensor to the processor 105 and the diversity transmitter unit 113.

With respect to the hereafter described embodiments a transceiver or transmitter element with two antennas Is shown. However it would be understood by the person skilled In the art that embodiments of the Invention may employ further transmitter and receiver diversity units to transmit and receive from more than two antennas and that similar apparatus and procedures may be used to generate similar advantageous embodiments. These embodiments of the invention are able to provide transmit time diversity for transceivers/transmitters suitable for implementation in a multiple antenna device without requiring the same number of power amplifiers as the number of antennas used. Simitarly although the below embodiments of the invention specifically describe the invention in terms of transceivers it would be understood by the person skilled in the art that the same advantageous elements and features may be employed in pure transmitters.

In order to have time domain diversity it is necessary to provide some delay of the second transmitted signal relative to the first transmitted signal. For different systems suitable radio channel models may be generated based on measurements on the used frequencies. As a reference 3gpp (3rd Generation Partnership Project) channel models are shown in Table 1, where relative delays for each path are shown.

FIG 1 Channel models of TS2G.104 onriex B2 Case 1 (3 kin/h) Case 2 (3 krnf hi Case 3 (120 km/h) Case 4 (3 km/h) Case 5 (50 km/h) Relative Average Relative Average Relative Average Relative Average Relative Average delay power delay power delay poeer delay power delay power Path 1 0 ns 0 d8 0 ris 0dB 0 ns 0dB 0 ns U dB 0 ns 0dB Path 2 976 ns -10dB 976 ns 0dB 290 is -3dB 976 ns 0dB 976 n -10dB Path 3 20000 n 0 dB 521 es -6dB Pail, 4 791 is -908

Table I

A first embodiment of the invention is illustrated in Figure 4. In the circuit of Figure 43, the main receiver unit 109, the main transmitter unit 111, the diversity receiver unit 115 and the diversity transmitter unit 113 is shown in more detail.

The main transmitter unit 111 comprises a transmitter 10 coupled to a digital to analog converter (DAC) 12. The output of the DAC 12 is coupled to a first mixer 14 which also receives a mixing frequency from an oscillator 22. The output of the first mixer 14 is the upconverted transmission signal which is applied to amplifier 16, where the signal is amplified ready for transmission. The amplified transmission signal is then coupled to the antenna (the first antenna) 20 through duplexer (also known as a duplex filter) 18. The output of the amplifier 16 is further coupled to the diversity transmitter unit 113 and specifically a power divider in the diversity transmitter 60.

The amplifier 16 may include a variable gain controlling stage which may change a signal power level when it passes the amplifier. The variable gain block 16 can be controlled by a gain controlling algorithm which may be implemented in the processor 105 or in the transmitter unit 10. The gain controlling algorithm may change the output signal power from the antenna based on the controlling commands from network. Alternatively, the power level may be changed based on information from a power detection circuitry, which is not shown in figure 3. The main transmitter unit circuitry may in some embodiments of the invention be located physically close to the first antenna 20 or the second antenna 46. Alternatively in other embodiments of the invention the main transmitter unit 111 may be placed near the first and/or second duplex filters 18, 58.

The first antenna 20 may also receive a signal, and this received signal is separated from the transmitted signal in the duplexer 18. The duplexed received signal is then passed to the main receiver 109.

The main receiver unit 109 comprises the following elements which may receive and decode the duplexed received signal. Firstly the main receiver unit may amplify the received signal in a low noise amplifier (LNA) 32 before downconverting the signal to a base band in a second mixer 30. The second mixer 30 receives the mixing frequency from a main receiver oscillator 24. The downconverted received signal may then be digitized in a main receiver analog to digital converter 28 and the digitized signal coupled to a first receiver 26 where the signal may be decoded.

The circuit comprises a further or second antenna 46 which will also receive signals for the device. The signals received by the second antenna 46 are applied to a second duplexer 54 to separate any received signals from any signals being transmitted using the second antenna 46. The received signal is then passed to the diversity receiver unit 115. The diversity receiver unit 115 comprises the following elements which may receive and deOoded the received signal from the second antenna 46. The diversity receiver unit may coupled the second duplexer 54 to a diversity receiver LNA 42. The amplified signal output by the diversity receiver LNA 42 is coupled to a third mixer 40 where the signal is downconverted to baseband, using a frequency supplied by a diversity receiver unit oscillator 38. The downconverted signal may then be digitized in a diversity receiver unit ADC 36, and the digitized signal coupled to the diversity receiver 34 where the signal may then be decoded.

The diversity transmitter unit 113 comprises the power divider 60 which is configured to receive the amplified transmit signal from the main transmitter 111 amplifier 16, and divides the power of the signal between two outputs. A first output of the power divider 60 is coupled to a first input of a power combiner 62. A second output of the power divider 60 is coupled to a delay element 66 which delays the signal by a known amount. The output of delay element 66 is coupled to a second input of the power combiner 62. The output of the power combiner 62 is then coupled to the second antenna 46 via the second duplexer 58.

According to one embodiment of the invention, power divider 60 and power combiner 62 are adjustable so that the magnitude of the delayed signal may be altered if the transmission power control of the system requires. The power divider 60 and power combiner 62 may be adjusted in response to a power control signal received from the processor 105 via the power control line 63. The control signal received from the processor 105 may be dependent on the operations carried out by any of or a combination of the main transmitter unit 111 the main receiver unit 109 and the diversity receiver unit 115.

Thus a proportion of the power of the amplified transmit signal output from the main transmitter unit 111 amplifier 16 is delayed in the diversity transmitter unit 113 delay element 66 and then applied to the second antenna 46 to provide a delayed transmit signal.

Thus as shown above there is provided an apparatus comprising a first transmit path, which is provided in these embodiments by the main transmitter unit 111. The first transmit path is configured to receive a first signal, and provide a first output signal.

Furthermore the apparatus comprises a second transmit path, which is provided in these embodiments of the invention by the diversity transmitter unit 113. The second transmit path is configured to receive the first signal and provide a second output signal. Furthermore the second transmit path comprises at least one delay element configured to receive and delay at least a portion of the first signal.

Furthermore the second transmit path may comprise: a power divider 60 having a first output coupled to said delay element and a second output coupled to a delay element bypass, said power divider configured to receive said first signal.

The second transmit path may further comprise: a power combiner 62 having a first input coupled to said delay element and a second input coupled to the delay element bypass.

The signals transmitted from the first and second antennas may have substantially different group delays compared to each other, so that the transmission signal from the second antenna is delayed with respect to the signal transmitted from the first antenna 20.

The amount of the delay introduced by the diversity transmitter unit 113 delay element 66 may be a fixed delay (or fixed delay line) or may be a variable delay. In some embodiments of the invention the diversity delay element 66 may alter the delay based on control signals received from the processor 105 via the delay control line 64. The processor 105 may determine a desired amount of the delay, for example based on the information of the received signal delay profiles. The received signal paths (the main and the diversity receiver paths) may contain information as to how much the signal should preferably be delayed in order to enable efficient time space diversity from available different multipath propagations. In some embodiments of the invention the power control signal received from the processor may be dependent on the operations carried out by any of or a combination of the main transmitter unit 111 the main receiver unit 109 and the diversity receiver unit 115.

In time division duplex (TDD) systems uplink and downlink signals are transmitted and received at the same frequency and may be generally assumed to experience in a steady environment the same channel characteristics. When the apparatus is in a steady state condition, for instance when a user equipment is placed on a table, the channel properties are almost constant when considered over a certain time period.

The apparatus, if in such situation may adjust optimal delay properties for communication based on received signal information in a TDD system or based on information provided by a node B in TDD/FDD systems. In FDD systems uplink and down link channels use different frequencies, so these transmit and receive.channels will experience different propagation channels. However in embodiments where the transmit and receive channels have relatively small differences in frequency the diversity power and delay characteristics may be chosen based on the receive channel values as the difference may be considered to be minor.

Urban and countryside environments provide different fading channel environments for signals. In an Urban environment signals may have several routes between transmission and reception antennas. Fading channel properties are related to user equipment speed, i.e. how fast the apparatus moves if it is the user equipment or how fast the other apparatus with the apparatus is communicating if the apparatus is a node B or similar base station receiver. At walking speed < 3km / h the channels may be expected to change slowly, but receiver introduced signal strength intensity changes may have large intensity fluctuations. For example, when located behind an urban buildings where no line of sight connection is present between the user equipment and the node B. Alternatively, fading channel properties may change quickly when terminal speed increases. By optimizing the amount by which the second signal is delayed so that for signals received via different antennas, the probability is low that the same chip info from an original signal and from a delayed signal do not meet weak point for the channel at same time, overall reception quality may be increased.

In an alternative embodiment a network or node B can provide information to an user equipment relating to an amount of delay in terminal transmission between at least two signals to optimize base station reception. On the other hand, an user equipment can provide information to the node B relating to how much delay is being used at a certain time. Delaying a signal may be considered equivalent to phase shifting the signal.

In an alternative embodiment of the invention, an user equipment may provide a node B with information relating to, for example, the delay used, a terminal speed, direction, location coordinates, detailed route information what functionality a user is using or planned to use, and from where the connection is being made. Using this information, a node B may locate an user equipment physically on a map/physical route. When the node B knows which a route on which the user equipment is travelling, the node B may predict the next fading points and adjust the user equipment transmitted signal delay to allow for the predicted fading channel properties. The user equipment may acquire location related information from its sensors or location calculations units, for example GPS, Galileo. The location calculation unit may be located in the user equipment or be external to the user equipment or calculation may be performed on the network side.

In an alternative embodiment when the user equipment moves it may become close to a cell edge where a first node B needs to handover connection to a second node B when the user equipment moves into the cell range of the second node B. Both the first node B and the second node B can receive signals from the user equipment at a certain time. As part of the handover procedure, when handing over from the first Node B to the second Node B, a second transmit path delay may be provided, such that the delayed transmitted signal is optimal for reception by the second Node B. According to one example embodiment, the second Node B may provide the updated delay information directly to the user equipment, or may provide the information via the first Node B. When the handover is performed, then the delay value being used may be switched to the new delay value so that both transmit antennas may be used to optimize the new connection to the second Node B. In a further embodiment of the invention, the user equipment may inform when the user equipment starts to use and when the user equipment stops using delayed transmission and how much the delay should be. The network or the second user equipment may request that the first user equipment starts or stops using delayed transmission.

In an alternative embodiment, different user equipment may have the power and delay adjustment of the diversity transmitter unit 113 implemented differently, and may have different limits as to how much they are able to delay the second transmission. The possible adjustable delay range may be related to the implementation of the invention in the user equipment. User equipment may be assigned to different categories according to their capability to support delayed transmission, and user equipment may communicate their delay amount or class to a nodeB. Additionally, user equipment may provide the nodeB with information relating to the accuracy of location information that they provide.

In a further embodiment of the invention, user equipment antennas may be located at different places. When a user holds the user equipment in their hand or changes the terminal location on their cheek then the antennas may see changes in the VSWR (voltage standing wave ratio). The user equipment may be able to adjust the delay used according to received information so that at least one antenna may have a good channel to the nodeB.

In a further embodiment of the invention, main duplexer 18 may be replaced with receive and transmit filters. The first antenna 20 may be replaced with separate transmit and receive antennas, with the transmit antenna coupled to the transmit filter, and the receive antenna coupled to the receive filter. In this embodiment, the transceiver and receiver antennas may be different. A corresponding modification of the described implementation is possible with the second (diversity) duplexer 58 and second antenna 46. These modifications may be done alone or combined within the same device. The signal provided to the second transmit antenna 46 may be taken from the first transmitter path using a directional coupler, capacitor, divider, adjustable divider, or any other known method. The signal may be taken before the power amplifier or after any gain stages. Additionally, for the delayed signal to be routed to the second transmit antenna, the signal may be amplified a certain amount in a small power buffer/driver amplifier or power amplifier (not shown in Figures).

In a further embodiment of the invention, a main duplexer 18 or a second duplexer 58 may be replaced with receive and transmit filters and with a transmission and reception switch. The transmission and reception switch can combine transmission and reception signals into an antenna. In one embodiment of the invention at least one radio frequency characteristic of a main duplexer 18 or a second duplexer 58 may be changed when transmission signal is convoyed to the second antenna.

In one embodiment of the invention, both the power amplifier 16 in the first transmit path and the gain stage in the second transmit path may be used at same time or the second transmit path amplifier may be active and the signal bypassed around the first transmit path amplifier with an alternative path to the first antenna. A device implemented in this way may be able to transmit the signal via the two antennas with certain powers e.g the first antenna 23 dBm and the second antenna 10 dBm power.

The total radiated power in this example is 210mW; 200 mW with the first antenna + 10 mW with the second antenna.

The power transmitted from the second antenna may be selected so that total radiated power from the terminal fulfils communication system transmission power tolerance requirements. In one embodiment of the invention, transmission power from the second antenna may be higher than from the first antenna.

User equipment may have different power classes with their capability to transmit with at least two antennas and these terminals may have power class which may be indicated to network. The highest power levels are needed at the edge of the cell and for high throughput, and the lowest power levels are mainly used close to the base station.

In an alternative embodiment, the user equipment may request the base station to allocate a lower output power class to the user equipment so that the user equipment is not required to use power amplifiers for high data throughput. If the user equipment can bypass a power amplifier e.g. when in an office and home environment, then terminal power consumption may be reduced and battery life will be improved.

The delay element 66 may be implemented in any known way. For example, the delay element 66 may comprise one or more delay lines, that is long transmission lines which will delay the signal. One possible implementation is a strip line which may be a fixed or variable length, which may be implemented on top or inner layer of a printed wire board. The delay may also be achieved by filtering the signal. Selection of the filter material and filter shape will affect the actual value of the group delay. If a high group delay is required this may be implemented with a material with a high value of Er (i.e. a material with a high relative static permittivity).

In other embodiments of the invention the delay element 66 may be implemented as a filter to introduce a time domain delay. A filter will have a group delay property which defines a time domain delay of each frequency passing through the filter. This delay of the filter is a function of a phase transfer function of the filter. The filter can be designed so that the filter may have a substantially constant amplitude response at the operational frequency of a signal but it will introduce a delay to a signal. When a centre frequency of a filter is low then higher delay of a filter pass band can be implemented. One possible method to increase the delay of a delay element is to down convert the transmission signal to a lower frequency where the signal will pass a delay element and then after the delay element, up convert the filtered signal to a transmission frequency.

According to an embodiment of the invention, the delay steps which may be selected for the signal transmitted from the second antenna 46 may be selected so that the delay is a multiple of the chip or symbol rate of the first transmission signal. In this way, the signal transmitted from each antenna may be in the same phase. By ensuring that the transmitted signals are in the same phase, it may be possible to ensure that the radiated error vector magnitude is according the system specification.

Therefore, this method may reduce the code domain power leakage from one code to further code when CDMA transmission is considered.

The power divider 60 may be implemented in any known way, for example the power divider 60 may be implemented as a step attenuator or as a scalable potentiometer or as a fixed directional coupler or an adjustable directional coupler. Similarly the power combiner 62 may be implemented in any known way for example as a scalable potentiometer or a fixed/adjustable directional coupler.

A timing and amount of a delay and a diversity transmission power control are dependent of the amount of delay needed and configuration of the transmitter arrangement. The control may be done based on information at least one of an operational frequency of a receiver(s), an operational frequency of a transmitter(s); also other communication systems included into the terminal; timings of the receptions and transmissions, a power level of transmissions, a power level of receptions, a modulation methods of receptions/transmissions.

Figure 9 illustrates a method according to one embodiment of the present invention.

In step 100, the transmit signal is amplified for transmission in an amplifier. A first portion of this amplified signal is then provided to the first antenna 20, from which it is transmitted in step 102. A second portion of the amplified signal is delayed in delay element 66 in step 104. This delayed signal is then provided to the second Antenna 46 for transmission in step 106.

Figures 5 to 8 show a series of further embodiments of the invention.

The embodiment shown in Figure 5 is similar to that shown in Figure 4, however, the diversity transmitter unit power divider 60 shown in the embodiment of Figure 4 has been replaced with a first switch 70, and the diversity transmitter unit power combiner 62 has been replaced by a second switch 72. The first and second switches 70 and 72 may be controlled using control signals from the processor 105 via the switch control line. By controlling the switches, the Transmitter 10 is able to select whether the portion of the transmit signal transmitted from the second antenna 46 passes through the delay element 66 and is delayed, thereby providing transmit time diversity. Alternatively the portion of the transmit signal transmitted from the second antenna 46 may be bypassed around the delay element 66, so that there is substantially no delay of associated with the signal transmitted from the second antenna 46 relative to the signal transmitted from the first antenna 20, to thereby provide transmit current diversity. The embodiment as shown in figure 5 may be considered to be similar to that shown in figure 4 where the power control is an either/or decision where the output from the main transmitter amplifier 16 is either passed though the delay element 66 or bypasses the delay element. In alternative embodiment multiple delay elements 66 may be implemented. These elements may be connected in parallel or in series of each other. In such embodiments delay control may be maintained by switching on and off delay elements to create a delay network path with the desired total delay.

The embodiment shown in Figure 6 is similar to the embodiment shown in Figure 4, However the main transmitter unit 111 comprises a further power amplifier located after the power amplifier 16 and before the duplexer 18. Thus in this embodiment the portion of the transmit signal to be transmitted via the second Antenna 46 is divided after the first Amplifier 16, but before the further power amplification signal produced by amplifier 80. This embodiment may be advantageous when maximum transmit power levels are not transmitted via the second transmission Antenna 46 as the diversity transmitter unit may be implemented using lower power rated devices.

The embodiment of Figure 7 is similar to that of Figure 5, where a first switch 70 and a second switch 72 respectively switch the diversity transmitter path between the delay element path and the bypass path. In the embodiment shown in Figure 7 the output of the main transmitter amplifier 16 is received by a variable gain amplifier 82 and the output of the variable gain amplifier connected to the fist switch 70 input. The gain applied to the signal by the variable gain amplifier 82 may be a gain or a loss, in order to control the relative strengths of the portion of the transmit signal transmitted via first Antenna 20 and via second Antenna 46. Control of the variable gain amplifier 82 may be made from a control signal from the processor 105 via a variable gain line 67.

The variable gain element 82 may be used to alter the magnitude of the second transmitted signal, which is delayed before being transmitted from the second antenna 46, in combination with any of the other described embodiments. The variable gain element may either amplify or attenuate the second transmitted signal.

The controlling of the variable gain element 82 may be dependent on the operations carried out by any of or a combination of the main transmitter unit 111, the main receiver unit 109, and the diversity receiver unit 115.

By combining information from at least two of the first transmitter, first receiver or second receiver blocks, the delayed signal magnitude can be correctly controlled.

According to one embodiment of the present invention, the desired delayed signal level may be determined by the total transmission signal level, which is a sum of first transmitted signal and the second transmitted signal.

The embodiment of Figure 8 is similar to that of Figure 5, however the control signals for controlling the first and second switches are provided by a sensor 90 via the sensor control line 68 from the processor 105. The sensor 90 may monitor any aspect or aspects of transceiver operation to determine whether the delay element 66 should be bypassed, or whether the portion of the transmit signal to be transmitted via the second antenna 46 should be delayed in delay element 66. In an alternative embodiment sensor 90 may provide control directly via the sensor control line 68.

According to a further embodiment of the invention, the delay provided by the delay element 66 may be selected based on information from the sensor 90 which may be integrated into the user equipment. In an example embodiment of the invention, sensor 90 may comprise a proximity sensor which is able to detect the operational mode of the terminal. For example the sensor may detect if a clam shell terminal is in an open or closed position, and this information may be used to in the delay path selection. The sensor information may also be used in conjunction with any other proposed control method.

It should be noted that a number of permutations and combinations of the above described embodiments are possible and are considered within the scope of this disclosure. For example, it should be noted that power dividersfpower combiners shown in the embodiments of Figure 4 may alternatively be implemented as switches. Similarly, the switches shown in the embodiments of Figures 5 to 8 may alternatively be implemented as power dividers/power combiners. Alternatively, embodiments of the invention maybe implemented with a SIMO (Single Input Multiple Output) transceiver.

It is noted that whilst embodiments have been described in relation to user equipment such as mobile terminals, embodiments of the present invention are applicable to any other suitable type of apparatus suitable for communication via access systems. A mobile device may be configured to enable use of different access technologies, for example, based on an appropriate multi-radio implementation. It shall be appreciated that the term user equipment is intended to cover any suitable type of wireless user equipment, such as mobile telephones, portable data processing devices or portable web browsers.

It is also noted that although certain embodiments were described above by way of example with reference to the exemplifying architectures of certain mobile networks and a wireless local area network, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted that the term access system is understood to refer to any access system configured for enabling wireless communication for user accessing applications.

In general, the various embodiments of the invention may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The above described operations may require data processing in the various entities.

The data processing may be provided by means of one or more data processors.

Similarly various entities described in the above embodiments may be implemented within a single or a plurality of data processing entities and/or data processors.

Appropriately adapted computer program code product may be used for implementing the embodiments, when loaded to a computer. The program code product for providing the operation may be stored on and provided by means of a carrier medium such as a carrier disc, card or tape. A possibility is to download the program code product via a data network. Implementation may be provided with appropriate software in a server.

For example the embodiments of the invention may be implemented as a chipset, in other words a series of integrated circuits communicating among each other. The chipset may comprise microprocessors arranged to run code, application specific integrated circuits (ASIC5), or programmable digital signal processors for performing the operations described above.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or fab" for fabrication.

It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture, as non-limiting examples.

The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims.

Claims (28)

  1. CLAIMS: 1. An apparatus comprising: a first transmit path configured to receive a first signal and provide a first output signal; a second transmit path configured to receive the first signal and provide a second output signal, wherein the second transmit path comprises at least one delay element configured to receive and delay at least a portion of the first signal.
  2. 2. The apparatus of claim I wherein the second transmit path further comprises: a power divider having a first output coupled to the delay element and a second output coupled to a delay element bypass, the power divider configured to receive said first signal.
  3. 3. The apparatus of claim 2 wherein the power divider is adjustable to adjust the proportion of input power on each output.
  4. 4. The apparatus of claims 2 to 3, wherein the power divider is a switch configured to select either the delay element bypass or the delay element.
  5. 5. The apparatus of claims 2 to 4 wherein said second transmit path further comprises: a power combiner having a first input coupled to said delay element and a second input coupled to the delay element bypass.
  6. 6. The apparatus of claim 5 wherein said power combiner is adjustable to adjust the proportion of output power from each input.
  7. 7. The apparatus of claim 6 wherein the power combiner is a further switch.
  8. 8. The apparatus of claims 2 to 7 further comprising a sensor, wherein at least one of the power divider and the power combiner is adjustable in response to a control signal provided by said sensor.
  9. 9. The apparatus of claims I to 9, wherein the first transmit path further comprises a first amplifier configured to provide the first signal.
  10. 10. The apparatus of claim 9, wherein said first transmit path further comprises a second amplifier coupled between the first amplifier and an output of the first transmit path; wherein an input of the second transmit path is coupled to an output of the first amplifier and an input of the second amplifier.
  11. 11. The paratus of claims I to 10 wherein the second transmit path further comprises a variable gain element configured to receive the first signal.
  12. 12. The apparatus of claims I to 11 wherein the delay element is adjustable.
  13. 13. The apparatus of claims 2 to 12, further comprising a processor, wherein the processor is configured to control at least one of: the distribution of power of the first signal to the delay element; the delay of the delay element; and the gain of the second transmit path.
  14. 14. The apparatus of claim 13, wherein the processor is configured to control dependent on the type of the first signal.
  15. 15. A method comprising: receiving a first signal at a first transmit path; providing a first output signal from the first transmit path; receiving the first signal at a second transmit path; and delaying at least a portion of the first signal to generate a second output signal.
  16. 16. The method according to claim 15, further comprising: dividing the first signal received at the second transmit path to provide the at least a portion of the first signal, wherein the remainder of the first signal received in the second transmit path bypasses said delaying.
  17. 17. The method of claim 16, further comprising adjusting the proportion of first signal delayed.
  18. 18. The method of claims 16 to 17, wherein the dividing the first signal received at the second transmit path comprises switching the first signal to either be delayed or bypassed.
  19. 19. The method of claims 16 to 18, further comprising combining the delayed signal with the bypassed signal.
  20. 20. The method of claim 19, wherein the combining the delayed signal with the bypassed signal comprises adjusting the combination of the proportions of the delayed signal and the bypassed signal.
  21. 21. The method of claims 19 and 20, wherein combining the delayed signal with the bypassed signal comprises switching at least one of the delayed signal and the bypassed signal to be output.
  22. 22. The method of claims 16 to 21, further comprising sensing and wherein at least one of the dividing and the combining is dependent on the sensing.
  23. 23. The method of claims 15 to 22 further comprising amplifying or attenuating the first signal received at the second transmit path in a variable gain element.
  24. 24. The method of claims 17 to 23 further comprising controlling at least one of: the distribution of the portion of the first signal to be delayed; the delay period of the delay; and the amplification gain of the second transmit path.
  25. 25. A chipset comprising the apparatus of any of claims I to 14.
  26. 26. An electronic device comprising the apparatus as claimed in any of claims 1 to 14.
  27. 27. A computer program code means adapted to perform any of the steps of claims 15 to 24 when the program is run on a processor.
  28. 28. An apparatus comprising: first transmit means for receiving a first signal and providing a first output signal; second transmit means for receiving the first signal and providing a second output signal; wherein said second transmit means comprises at least one delaying means for receiving and delaying at least a portion of the first signal.
    29 An apparatus comprising: a first controller configured to control an output signal of an amplifier of a first antenna; a second controller configured to control a portion of said amplified output signal to a first antenna; a third controller configured to control a further portion of said output signal through delayer configured to delay to at least one of the second antenna.
GB0809077A 2008-05-19 2008-05-19 Controlling transmission diversity by delaying a signal on a second transmit path relative to a first transmit path Withdrawn GB2460112A (en)

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