JP2011523512A - Wireless receiver having intermediate cutoff function of RF circuit - Google Patents

Abstract

A terminal (24) for use in a wireless network (20) that includes a radio frequency (RF) receiver (30) configured to receive a down-converted RF signal to generate an output signal. The RF signal consists of lower link frames, each lower link frame having an allocation area with at least one data area. The allocation area includes one indication of time allocation in which the downlink data is transmitted to the terminal in the data area. An analog / digital (A / D) converter (36) converts the output signal from the RF receiver into a stream of digital samples. A digital processing circuit (40, 52, 54, 56) identifies the time allocation and processes the digital samples to recover the downlink data transmitted within the time of the identified time allocation, The RF receiver is blocked in at least one time interval other than the time of the identified time allocation within the downlink.
[Selection] Figure 1

Description

Comparative Control with Related Applications This application is an extension of a portion of US Patent Application 11 / 647,123, dated December 27, 2006, referenced herein.

TECHNICAL FIELD The present invention relates generally to wireless communication, and more particularly to operation control of a wireless communication terminal.

  WiMAX (World Microwave Access Interoperability) is a new technology for wireless packet data communication. WiMAX is a concept close to the wireless LAN (WLAN) defined in the IEEE 802.11 standard, but has several characteristic functions designed to improve performance and area. The original WiMAX standard, IEEE 802.16, defined WiMAX in the 10-66 GHz band. More recently, IEEE 802.16a has added support for the 2-11 GHz band and IEEE 802.16e (approved as IEEE 802.16-2005) uses WiMAX for mobile communications using the enhanced orthogonal frequency division multiple access (OFDMA) conversion scheme. Expanded. In the context of the present application and in the claims, the expression “802.16” refers to the whole including the original IEEE 802.16 standard and its extensions unless otherwise specified.

  To save power, IEEE 802.16-2005 (see especially 6.3.21) defines a dormant scheme that can be used to reduce the duty ratio at which a mobile station (MS) listens for downlink signals. . To begin that scheme, the mobile station sends a dormant mode request (SLP-REQ) message to the base station, identifying the frame period during which the mobile station enters dormant mode and thus does not receive a downlink signal. During these pauses, the base station shuts down some of its circuitry, reducing power consumption without the risk of losing downlink signals.

  3rd Generation Partner Project Long Term Progress (3GPP-LTE) is a new technology for wireless packet communication, also called Evolved Universal Terrestrial Radio Access (E-UTRA). The LTE standard is being developed by the 3GPP Radio Access Network (RAN) Technical Specification Group (TSG). In one aspect, LTE is similar to the WiMAX technology specified in the IEEE 802.16e standard. For example, both standards use an enhanced orthogonal frequency division multiple access (OFDMA) transform scheme for the downlink (DL) channel.

  The LTE standard defines a dormant scheme called “discontinuous reception (DRX) in RRC connected mode”. The DRX scheme is used to reduce the duty ratio at which a customer terminal (referred to as customer equipment—UE in LTE) attempts to receive a downlink signal from a base station (referred to as extended NodeB-eNodeB). The DRX method defines a duration in which a customer equipment (UE) monitors LTE control messages sent for allocation from an eNodeB and performs various signal measurements. Outside the duration, the customer equipment does not receive the downlink signal.

US patent application 11 / 647,123

  In a wireless multiple access system such as WiMAX or LTE, a base station (BS) transmits and receives signals in which synchronized frames are arranged in order. Based on the data transmission request, the base station dynamically designates each time allocation in each frame for transmission / reception. The base station typically transmits a time allocation designation within the time of the allocation region located near the beginning of each downlink link. The allocation indicates a time zone in which the data of the lower link is transmitted to each terminal within the time of the data area next to the frame (not only the next upper link transmission time).

  The vocabulary of wireless interface and protocol elements varies depending on the standard. For example, the WiMAX standard defines a frame, which can be divided into upper and lower link sub-frames and further subdivided into regions. The LTE standard defines a frame permutation, which is subdivided into one or both of the upper link, lower link sub-frames. The WiMAX base station transmits the allocation information to the customer terminal within the time of the “map area” arranged at the beginning of the downward link frame. LTE eNodeBs, on the other hand, are referred to as dedicated physical downlink control channels (PDCCHs) and transmit within the time of OFDM symbols located near the beginning of the downlink subframe. In the application and claims of the present invention, generally a base station (eg, may consist of a WiMAX base station or LTE eNodeB), a wireless terminal (eg, a WiMAX mobile station or LTE customer equipment (UE)), upper And downlink link frames (eg, WiMAX frame or LTE sub-frame) and allocation information (eg, WiMAX map message or LTE physical downlink control channels (PDCCHs)). These terms should be understood to apply to the corresponding elements of all applicable radio standards, even if other terms are used as a habit.

  In the disclosed embodiment of the present invention, the frame structure defined by applicable standards is used to block the elements of the terminal in the interval between the lower link frames where the terminal is expected to have no data to receive. ing. The terminal circuit is activated and receives and processes the downlink data transmitted from the base station within the specified time allocation in the allocation area and the data area. In the time interval other than the designated time allocation, certain elements of the terminal, for example, wireless receivers, are shut down to save power. (The term “shutdown” is broad in the context of this patent application and claims, and refers to all operating mode changes that reduce power consumption by reducing functionality.) In addition to full-frame blocking technologies such as WiMAX and LTE sleep modes, it can be used to minimize power consumption and maximize battery life of wireless terminals.

According to an embodiment of the present invention,
A radio frequency (RF) receiver;
Wherein the RF receiver is configured to receive a down-converted RF signal to generate an output signal;
The RF signal consists of a lower link frame,
Each down link frame has an allocation area with at least one data area;
The allocation area contains instructions for time allocation in the data area,
Downlink data is sent to the device within the time allotted,
An analog / digital (A / D) converter connected to convert the output signal into a stream of digital samples;
Process the digital samples to identify the time allocation in response to an indication in the allocation region and recover the downlink data within the time allocation identified while the RF receiver A digital processing circuit connected to block at least one time interval other than a time of the identified time allocation within the framework of
A terminal used for a wireless network is provided.

According to an embodiment, the digital processing circuit is
A digital physical layer interface (PHY);
A media connection control (MAC) processor;
In addition to the RF receiver, a power controller that shuts off at least one digital component of the terminal for at least one time interval, wherein the at least one digital component includes an A / D converter, PHY, and MAC processing It is selected from an element group consisting of containers.
According to an embodiment, the time assignment has a start time and an end time, the digital processing circuit shuts off the RF receiver after receiving the indication at the time of the assignment region, and sets the start time of the assignment to the first time. Is configured to activate the RF receiver at a first time, going back by a margin, and delay the allocation end time by a second margin, shut off the RF receiver at a second time. .

  According to another embodiment, the digital processing circuit processes the digital samples in the first portion of the downlink to determine one or more characteristics of the wireless channel over which the RF signal is received. The first and second margins are determined corresponding to the above characteristics. According to the disclosed embodiments, the one or more characteristics include a channel coherence characteristic, the channel coherence characteristic comprises time coherence and bandwidth coherence, and the first and second margins increase time coherence. However, it increases as bandwidth coherence decreases. According to yet another embodiment, the one or more characteristics include a radio channel signal to noise ratio (SNR), and the first and second margins increase as the radio channel signal to noise ratio (SNR) decreases. To do.

According to an embodiment, the downlink frame includes a preamble that precedes the allocation region, and the digital processing circuit processes the digital samples within the time of the preamble to determine one or more characteristics of the radio channel. Configured to do.
According to an embodiment, the digital processing circuit is connected to determine a first margin for a time allocation in a particular downlink link corresponding to a frame preceding the particular downlink link. ing. The digital processing circuit determines whether a frame preceding a particular down link frame includes another down link frame, and a frame preceding the particular down link frame is another one for the terminal. A step of determining whether to include a time allocation, and a first margin corresponding to executing at least one action step selected from a group of action steps comprising:

According to another embodiment, the digital processing circuit determines a second margin for a time allocation within a particular downlink link corresponding to one pane following the particular downlink link. The digital processing circuit is connected to determine a second margin corresponding to the step of determining whether a frame following a particular downward link frame includes another downward link frame.
In yet another embodiment, the digital processing circuit determines that no time is allocated for transmission to the terminal within the time period of a particular downlink link, and the RF receiver is designated for a particular downlink according to that decision. It is configured to block all data areas within the link frame during the time.
In one embodiment, the downlink link frame is transmitted from one base station in accordance with the IEEE 802.16 standard. The lower link frame is transmitted from one base station in accordance with the IEEE 802.16 standard.

In another embodiment, the downlink link frame is transmitted in accordance with Third Generation Partnership Project-Long Term Development (3GPP-LTE) by an enhanced NodeB (eNodeB). The digital processing circuit is connected to identify the time allocation by decoding physical downlink control channel (PDCCH) symbols transmitted in the time allocation domain.
In accordance with an embodiment of the present invention, further, receiving and downconverting a radio frequency (RF) signal using an RF receiver of the wireless terminal to generate an output signal;
Here, the RF signal consists of the frame of the lower link,
Each down link frame has an allocation area with at least one data area;
The allocation area contains one indication of one time allocation in the data area,
Downlink data is sent to the device within the time allotted,
Converting the output signal into a stream of digital samples;
Identifies the time allocation in response to an indication in the allocation domain and processes the digital samples to recover the downlink data within the identified time allocation time, while the RF receiver Blocking in at least one time interval in the window other than the identified time allocation;
A communication method is provided.
The invention will be more fully understood from the following detailed description of the embodiments and the accompanying figures.

1 is a pictorial illustration of a wireless network system according to an embodiment of the present invention. FIG. FIG. 3 is a block diagram of a wireless terminal according to an embodiment of the present invention. FIG. 6 is a timing diagram illustrating a method for starting and shutting down an element of a wireless terminal according to an embodiment of the present invention. FIG. 4 is a timing diagram illustrating details of FIG. 3 according to an embodiment of the present invention. 6 is a flowchart illustrating a method for starting and shutting down an element of a wireless terminal according to an embodiment of the present invention. FIG. 6 is a timing diagram illustrating a method for starting and shutting down an element of a wireless terminal according to another embodiment of the present invention. 6 is a flowchart illustrating a method for starting and shutting down an element of a wireless terminal according to another embodiment of the present invention.

Detailed Description of Embodiments FIG. 1 is a pictorial illustration of a wireless network system 20 according to an embodiment of the present invention. The following description of FIGS. 1-5 describes one or more systems operating primarily in accordance with the aforementioned WiMAX IEEE 802.16 standard for convenience and clarity. 6 and 7 describe aspects that operate according to the LTE standard. System 20 may operate in accordance with other multiple access wireless standards. Such standards are defined, for example, in the specifications of 3GPP2 evolution data optimization (EVDO) modified version C and IEEE 802.20 high-speed mobile broadband wireless connection (MBWA).

  The system 20 consists of multiple radio terminals 24 (called mobile stations in WiMAX), which communicate with the base station within a certain specified allocated time in a frame permutation defined by the base station. The frame structure and timing are shown below with reference to FIG. 3 (other timing available in LTE is shown later in FIG. 6). Alternatively, the terminal 24 may be configured for communication with other wireless networks such as a wireless LAN and a Bluetooth network in addition to the WiMAX network. However, this aspect of mobile station operation is outside the scope of the present invention. As an illustration in FIG. 1, a type of wireless terminal is shown, but the term “wireless terminal” in this patent application and in the claims description refers to a wide range of all suitable types in which the principles of the invention may be implemented. It should be understood to show home appliances, calculators, and communication equipment.

FIG. 2 is a block diagram illustrating elements of one wireless terminal 24 according to an embodiment of the present invention. The figure shows only those elements of the data receiving portion of the wireless modem used at terminal 24 that are useful for understanding the present invention. The transmission part of the terminal 24, the host computing unit, and other elements are omitted for simplicity.
The downlink signal transmitted from the base station 22 is received by the radio frequency (RF) receiver 30 via the antenna 32. The RF receiver 30 uses the reference frequency input provided from the frequency synthesizer 34 to amplify, filter (filter) and downconvert the RF signal. A frequency synthesizer typically consists of a local oscillator having a phase locked loop (PLL) for frequency stabilization. The RF receiver 30 generates a down-converted output signal, typically I and Q baseband signals, or a composite intermediate frequency (IF) signal known in the prior art.

  Digital processing circuit 38 processes the digital samples to recover the downlink data transmitted by the base station. The circuit 38 comprises a digital physical layer interface (PHY) 40 that converts the samples into a stream of data bits. The components of the PHY 40 are generally known prior art, but are described here for completeness. The digital forward terminal 42 performs initial filtering and resampling, and subsequently the time domain samples are converted to frequency domain samples by a Fast Fourier Transform (FFT) calculator 44. Detector 46 converts the samples into data symbols using channel coefficients determined by channel estimator (CE) 48 for each of the sub-carriers in the downlink. A forward error corrector (FEC) 50 decodes the symbols to recover the bitstream of the downlink data. A media connection control (MAC) processor 52 extracts data on the downlink and processes data packets included in the bit stream to perform other MAC level functions.

  As described in detail below, the downlink link transmitted from the base station 22 has a map area in which the base station indicates the time slot and sub-carrier assigned to each radio terminal 24. Instruct. The map region typically provides a downlink map that provides a time slot for transmitting downlink data to each wireless terminal, and for each wireless terminal to transmit uplink data within the next uplink link. Consists of an upper link map that provides slots. The wireless terminal 24 has an allocation calculator 54 that processes the data in the map area of the lower link frame to identify the lower and upper links designated for this terminal. This type of map processing is typically a function of the MAC processor, but is shown here as separate functional blocks for clarity.

  The power controller 56 receives the time slot designation information from the allocation calculator 54 and uses this information for starting and shutting down other elements of the wireless terminal 24. During the time period of the downlink link designated by the wireless terminal as a dormant window (eg, using the aforementioned SLP-REQ message), the power controller shuts down all elements of the receiver for the lifetime of the window. To do. On the other hand, even during the downlink frame where the terminal is ready to receive data from the base station, the power controller may block certain elements of the receiver for a certain period of time within the frame. The function of this breakthrough power controller is further detailed with reference to the figures. It makes it possible to reduce the operating duty ratio of certain elements of the wireless terminal, thus reducing power consumption and extending battery life.

  In FIG. 2, the elements of the wireless terminal 24 are shown in the form of specific functional blocks for clarity of conception, but in practice these blocks are part of one or more dedicated or programmable integrated circuits. It is. In particular, the power controller 56 is executed by software running on a built-in arithmetic unit or by an appropriate logic circuit in a digital integrated circuit including the PHY 40 and the MAC arithmetic unit 52. Alternatively, the power controller is composed of a separate arithmetic unit or logic circuit.

WiMAX Timing Configuration FIG. 3 is a timing diagram illustrating the activation and shutdown schemes of elements of the wireless terminal 24 used by the power controller 56 according to an embodiment of the present invention. The system focuses on the permutation 58 of the lower link frame 60 and the upper link frame 62 defined in accordance with the WiMAX standard by the timing signal transmitted from the base station 22. Each down link frame consists of a preamble 64 containing a predetermined symbol for synchronization, followed by a map area 66 and a data area 68. (The display of the elements of the frames 60 and 62 in FIG. 3 is simplified for the sake of clarity, and parts not necessary for understanding the present invention are deleted. Similarly, “map area” “data The name “region” is also not defined in the WiMAX standard, but rather represents a function that is performed over time for a certain portion of the downward link frame. Those skilled in the art will be able to determine the relevant portion of these “regions” and the WiMAX frame. Is obvious.

The map area 66 typically consists of a map of the lower link (DL) followed by a map of the upper link (UL). The downlink map is a period of time during which the base station transmits the downlink data to the wireless terminal as well as directing the modulation and coding applied to the downlink data in the corresponding burst. A time allocation for each wireless terminal consisting of one or more bursts 70 in region 68 is indicated. In this embodiment, for simplicity, a single burst 70 is shown and described. However, the method described below can be applied to an allocation consisting of a plurality of bursts as it is. The burst 70 has a start time T ₁ and an end time T ₂ , and is composed of a certain set of sub-carriers shown in the vertical direction of the slot block in the figure. A burst consists of a single slot or multiple slots, each slot consisting of a certain number of consecutive symbols on a certain number of sub-carriers, as defined by the WiMAX standard. The map area may include not only additional maps (referred to as submaps in IEEE 802.16-2005), but also broadcast packets (eg, containing information about the configuration).

  As shown in FIG. 3, the power controller 56 synchronizes with the down link frame 60 and sends the RF receiver 30, the frequency synthesizer 34 and the PHY 40 within the preamble 64 and the map area 66 in order to process the map information. To start. The MAC processor 52 is also activated within the time of the map area to extract slot designation and modulation / coding information from the map data. If the wireless terminal 24 requests time allocation for uplink transmission, the power controller will place the RF receiver, PHY and MAC calculators in the entire map region to determine both downlink and uplink slot designations. Start in the period. Alternatively, if the wireless terminal has not requested an upper link assignment, the power controller may run these circuits for the time of the portion of the lower link map of map area 66.

Once the map information is received and decoded, the power controller 56 shuts off the RF receiver, PHY and MAC processor immediately after determining that no broadcast packet or sub-map follows. These elements are maintained for a period of the data area 68, the cut-off state until power controller restarts the verge of T _1. The frequency synthesizer may also be cut off during this period, or as shown in the figure, the operating state may be maintained to maintain frequency stability. After the wireless terminal receives and decodes the downlink data in burst 70, the power controller blocks the receiver element at the next downlink link. Alternatively, if the map information in the map area 66 indicates that the base station has not specified any down link time allocation to the wireless terminal in the current down link frame 60, the power controller Immediately shut off the receiver elements and do not restart them until the beginning of the next down link frame.

  To enable wireless terminal channel accumulation, the base station 22 transmits a test training signal at a predetermined time and frequency within each downlink link, as defined in the WiMAX standard. If the wireless terminal is stationary and the channel does not change with time, the channel estimator 48 may measure the channel coefficient once and then use it without change. However, in practice, the channel coefficient is generally updated due to the movement of the radio terminal or the change of the channel state, and thus the radio terminal needs to receive and process the test signal transmitted by the base station. The power controller 56 typically activates the receiver elements briefly before and after the burst 70 to facilitate accurate channel coefficient updates. This will be described in detail below with reference to the drawings.

FIG. 4 is a detailed timing diagram of FIG. 3 illustrating a method for determining activation and deactivation time of the RF receiver 30 of the power controller 56 according to an embodiment of the present invention. Burst 70 includes an allocation number N _ALLOC in data symbols as specified by the base station. To obtain additional test signals for channel integration, power controller activates the RF receiver N ₁ symbols only time T ₁ previously to block the RF receiver after only time T _2, hereinafter N ₂ symbols. The total operating time (in symbols) of the RF receiver is _therefore W = N ₁ + N _ALLOC + N ₂ . The power controller similarly determines the activation and deactivation times of the other receiver elements.

The values of N ₁ and N ₂ depend on the coherence characteristics such as the channel coherence bandwidth and coherence time. The channel typically has a high coherence time, especially when the wireless terminal is stationary or slowly moving. That is, the characteristics of successive test signals hardly change with the passage of time in the state received by the terminal. Low delay spread channels typically have a high coherence bandwidth. That is, there is relatively little change in channel response between different frequency sub-carriers. When the coherence bandwidth is high and / or when the coherence time is small, the power controller typically uses relatively small values of N ₁ and N ₂ . On the other hand, a large value is required for the reverse condition. High order modulation configurations and low coding gain increase the sensitivity of the receiver to noise, and therefore require larger N ₁ and N ₂ values.
A calculation method of N ₁ and N ₂ based on such a principle will be described below.

  FIG. 5 is a flowchart showing a method of starting and shutting off the element within the wireless terminal 24 by the power controller 56 in the embodiment of the present invention. Immediately prior to each downlink downlink 64 (FIG. 3), where the wireless terminal receives the downlink signal from the base station 22, in an initial receive step 80, the power controller is responsible for the elements of the wireless terminal required to receive and decode the signal. Start up. These elements include an RF receiver 30, an A / D converter 36, and a PHY 40 as well as a frequency synthesizer 34 (which may be activated early to ensure stabilization time). Alternatively, only certain elements of the terminal 24 with high power consumption, such as RF receivers, may be shut off and activated in this way, while the other elements remain active.

  Once the necessary elements are activated, the wireless terminal 24 receives the preamble 64 and the map of the downlink in the time of the map area 66 and identifies the time, frequency, and modulation parameters of the burst 70 to identify the downlink link. Decode the map. If necessary, the receiving component of the wireless terminal may remain operational in order to receive the uplink map information and / or broadcast packets for the remainder of the map area. Otherwise, to minimize power consumption, the power controller 56 shuts off the wireless terminal's receiving elements in an initial shut-off step 82 as soon as the downlink map is decoded. If the base station has not allocated the downlink time to the wireless terminal in the current downlink window 60, the receiving element of the wireless terminal remains blocked until the next window.

ここでｒ（ｋ，ｎ）はシンボル時間ｎにおけるサブ・キャリヤｋ上の受信試験信号であり、合計はすべての受信したサブ・キャリヤとシンボルについて計算される。Ｒ_Ｎ（Ｎ）とＲ_Ｋ（Ｋ）は、言い換えれば、シンボル間あるいはサブ・キャリヤ間の相関性をその識別子の関数として表している。高コヒーレンスのチャネルでは、これらコヒーレンス係数は比較的大きなＮおよびＫの値についても高い値を有し、低コヒーレンスのチャネルでは、これらコヒーレンス係数はＮおよびＫの値が小さい場合のみ高い値となる。 Given that the base station has assigned the downlink time allocation to the wireless terminal, the power controller 56 determines the channel time and bandwidth coherence in a coherence determination step 84. The coherence calculation is based on the channel coefficients measured by the channel estimator 48 in the preamble and map region times. For example, the temporal coherence coefficient R _N (N) and the bandwidth coherence coefficient R _K (K) are calculated as a function of the identifier K between subcarriers and the identifier N between symbols as follows.

Where r (k, n) is the received test signal on sub-carrier k at symbol time n and the sum is calculated for all received sub-carriers and symbols. In other words, R _N (N) and R _K (K) represent the correlation between symbols or sub-carriers as a function of its identifier. In high coherence channels, these coherence coefficients have high values for relatively large N and K values, and in low coherence channels, these coherence coefficients are high only when the N and K values are small.

あるいは、コヒーレンス帯域幅およびコヒーレンス時間の計算に、当業者にとって明らかな他の方法が使用されても良い。例えば、コヒーレンス時間は単に枠による利得の違いに基づいて計算されても良い。 Based on these coherence coefficients, coherence bandwidth C _BW and coherence time C _T is calculated as follows.

Alternatively, other methods apparent to those skilled in the art may be used to calculate the coherence bandwidth and coherence time. For example, the coherence time may be calculated simply based on the difference in gain due to the frame.

ここにｆ_１とｆ_２は既定の関数であり、典型的には電力制御器５６により参照表の形で保管される。これら関数はコヒーレンス帯域幅および時間、チャネル雑音σ_ｎ、雑音マージン（即ち最大許容雑音）σ_ＭＣＳ、さらに、地図により指示され、バーストの間使用される変調と符号化構成に基づいている。 Using the coherence bandwidth and coherence time determined by step 84, power controller 56 calculates margins N ₁ and N ₂ before and after the burst in margin calculation step 86.

Here, f ₁ and f ₂ are predetermined functions, and are typically stored in the form of a lookup table by the power controller 56. These functions are based on coherence bandwidth and time, channel noise σ _n , noise margin (ie, maximum allowable noise) σ _MCS , and the modulation and coding configuration used by the map and used during the burst.

Due to the general characteristic that margins N ₁ , N ₂ decrease as coherence bandwidth increases, coherence time decreases, and / or signal to noise ratio (SNR) increases, a variety of different functional forms are defined as f ₁ . It is used to f _2. Thus, for example, the values of N ₁ and N ₂ are small in a channel with good signal reception state and little movement. If the length N _{ALLOC of} burst 70 is also short (ie, data is transmitted in short bursts, eg, for voice communications), the duty ratio during operation of the RF receiver and other circuits is cut off at times other than time W. Can be greatly reduced. On the other hand, the increase in the margin value due to channel degradation and the movement of the wireless terminal does not impair the data reception performance in these situations as compared with the conventional terminal in which the receiving circuit is kept operating throughout the downlink. Guarantee.

ここにＦはスケール要素であり、経験的に決められる。信号雑音比が高い場合（σ_ｎが既定の閾値より低い場合）、チャネル雑音σ_ｎに対して調整された、増加した実効コヒーレンス帯域幅Ｃ_{ＢＷ−ｅｆｆ}が、等式（４）のＣ_ＢＷの替わりに使用される。
あるいは、高い信号雑音比の場合、Ｃ_ＢＷの替わりにＫ_ｅｆｆが使用されうる。ここにＫ_ｅｆｆはチャネル平滑化フィルタであるｗの絶対値で近似され、ｗは従来技術で既知のように典型的にＣ_ＢＷとσ_ｎに依存する。
または高い時間コヒーレンスのチャネルでは（ＣＴが一定の閾値より大きい場合）、ｆ_１とｆ_２の値はゼロに設定され、プレアンブルの時間で決定されるチャネル積算が、データ領域の時間内で空間―時間符号化が使用されていない限り、データ領域時間内での変更をせずに使用されうる。 In one embodiment, f ₁ and f ₂ are defined based on the target mean square error of the channel estimator when the signal to noise ratio is low.

Here, F is a scale element and is determined empirically. (If sigma _n is lower than a predetermined threshold) when the signal-noise ratio is high, is adjusted to the channel noise sigma _n, increased the effective coherence bandwidth _{C BW-eff} was found for _{C BW} equation (4) Used instead.
Alternatively, K _eff can be used instead of C _BW for high signal to noise ratios. Here, K _eff is approximated by the absolute value of w, which is a channel smoothing filter, and w typically depends on C _BW and σ _n as known in the prior art.
Or for high time coherence channels (when CT is greater than a certain threshold), the values of f ₁ and f ₂ are set to zero, and the channel integration determined by the time of the preamble is spatially within the time of the data domain— As long as time coding is not used, it can be used without modification within the data domain time.

The above functions are shown for illustrative purposes only and similar functions will yield similar results. If the wireless terminal 24 has a dual antenna 32, the applicable dual antenna mode of operation may dilute the test signal and the channel integration performance requirements may become even more sophisticated. The functions f ₁ and f ₂ may need to be adjusted taking into account the channel integration characteristics under such circumstances.
Using the calculated burst value before the margin in step 86, the power controller 56, the burst before starting step 88 activates the RF receiver 30 to the symbol N ₁ a time before the start of the burst 70. The frequency synthesizer 34 is activated immediately before this time if it was previously shut off. The power controller also activates the A / D converter 36 and the digital physical layer interface PHY 40 to process the signal output from the RF receiver. The MAC processor 52 is activated later at time T ₁ after the specified time burst is actually decoded by the forward error corrector FEC 50.

In the data reception step 90, the RF receiver 30 and the ancillary elements of the wireless terminal receive signals during the total operating time W = N ₁ + N _ALLOC + N ₂ . During this time, the digital physical layer interface PHY 40 updates the channel characteristic integration and processes the signal to demodulate the data on the signal sub-carrier using the channel integration.
When the post burst burst ends, at a time after symbol N ₂ after the end of burst 70, power controller 56 shuts off RF receiver 30 in post burst cut step 92. The frequency synthesizer 34 and the A / D converter 36 are also shut off at this point.
Typically, the PHY 40 and the MAC arithmetic processor 52 are shut off after a while after the processing of the data transmitted in the burst 70 is completed. The receiving element of the wireless terminal 24 remains blocked until the next downlink link preamble time at which the terminal may receive data.

LTE timing method
FIG. 6 is a timing diagram illustrating a method for starting and shutting down the elements of the wireless terminal 24 according to another embodiment of the present invention. The timing scheme of FIG. 6 refers to a 3GPP-LTE system in which a customer equipment UE communicates with one base station eNodeB.
In the LTE standard, the subframe of the lower link is generally connected to the subframe of the upper link or another sublink of the lower link in the front-rear direction. Similarly, the upper link sub-frame is generally connected to the lower link sub-frame or another upper link sub-frame in the front-rear direction. For example, the LTE standard defines a time division duplex (TDD) mode that allows different types of mutations between the upper and lower link sub-frames. The standard further defines a frequency division duplex (FDD) mode in which the upper and lower links are transmitted on different carrier frequencies. As described above, in FDD, the sub-frames of the respective lower links are connected to the sub-frames of the other lower links.

In the example of FIG. 6, the base station eNodeB transmits a downlink subframe 100, preceded by another downlink subframe, followed by an uplink subframe. The downlink subframe 100 begins with a physical downlink control channel PDCCH region 104, which typically consists of one and three orthogonal frequency division multiple OFDM symbols (hereinafter referred to as PDCCH symbols for clarity). In the PDCCH region, the base station eNodeB transmits downlink allocation information, which allocates downlink resources to different customer equipment UEs in the time of the data region 108 of the downlink subframe.
Typically, the base station eNodeB identifies a resource partition (RB) that defines the OFDM sub-carriers assigned to each customer equipment UE. The transfer is unidirectional (ie, directed to a specific customer equipment UE), multicast (for one customer equipment UE group) or broadcast (for all UEs). One customer equipment UE is assigned one or more resource partitions (RB), in which one transport partition is transmitted for each multiple input multiple output (MIMO) layer.

In this case, a customer equipment UE monitors the downlink of the base station eNodeB. The power controller 56 of the customer equipment UE activates the RF receiver 30, the frequency synthesizer 34 and the digital physical layer interface PHY 40 within the time of the PDCCH region 104 in order to process the allocation information in synchronization on the downlink subframe. To do. The MAC processor 52 is also activated within the time of the PDCCH region 104 to extract resource partition (RB) assignment and modulation / coding information from the PDCCH data.
In an embodiment, the customer equipment UE monitors only one subset of PDCCH data. Once the appropriate PDCCH symbol has been received and decoded, the power controller 56 determines that no more bursts are being transmitted in this sub-frame and at the same time the RF receiver, digital physical layer interface PHY, and MAC processor Shut off. These elements remain inactive during the time of the data area 108 until the next time the power controller is started. In this example, the customer equipment UE has been allocated burst 112 all the time, so the power controller maintains operation of the different receiver elements.
(In the example of FIG. 6, bursts 112 are contiguous in the frequency domain, ie, consist of a set of adjacent sub-carriers. However, in other embodiments, each allocation is from any sub-carrier set. And may or may not be adjacent on the frequency axis.)

If the customer equipment UE does not need to receive the next subframe after receiving and decoding the downlink data in burst 112, the power controller may shut down the receiver element until it is needed again. There is a case where reception of the next sub-frame is not necessary, for example, when the next sub-frame is a sub-frame of the upper link or a sub-frame of the lower link in the “expired” period of the intermittent reception DRX method. is there.
Alternatively, if the PDCCH information in the PDCCH region 104 indicates that the base station eNodeB has not specified any downlink time allocation to the customer equipment UE in the current downlink sub-frame, the power controller Immediately after processing is complete, block the receiver elements and do not activate them until the beginning of the next downlink sub-frame.

The base station eNodeB transmits a reference signal at a predetermined time and frequency according to the LTE standard and within the sub-frame time of each downlink so that the customer equipment UE can perform channel integration. Since the customer equipment UE may be moving and the channel state may change over time, the UE continuously receives and processes the reference signal transmitted from the base station eNodeB to update the channel coefficients. To facilitate accurate updating of channel coefficients, the power controller activates the receiver element for a short time before and after each burst.
The power controller may activate the receiver element not only after each PDCCH region, but only for a short time before (assuming the previous subframe is the sublink of the downlink). In the LTE protocol, the data region 108 begins with an OFDM symbol that immediately follows the PDCCH region 104. In an embodiment, the power controller selects one of several different scenarios based on the type of front and back sub-frames and whether or not to include an assignment for the customer equipment UE.

For example, if the previous subframe is an uplink subframe, the power controller activates the receiver element at the beginning of the current subframe because there is no reference signal to be received in the previous subframe. If the previous subframe is a downlink subframe, the power controller activates the receiver element slightly before the current subframe because the previous subframe contains a reference signal to be received by the UE.
If the previous subframe is a downlink subframe that includes at least one assignment for the UE, the receiver element is typically already active at the beginning of the current subframe and at least the end of the PDCCH region. To keep up. If there is no allocation for the UE in the current subframe, the power controller shuts off the receiver element after a short period of time in the PDCCH region. The length of the period is typically the number of OFDM symbols that contain reference signals required for proper channel integration, and the UE processes these PDCCH symbols and determines that there is no assignment for the terminal in the current subframe. Depends on the time required.

If the current subframe includes an assignment for the UE, and if the subsequent subframe is not a downlink subframe that the terminal is required to monitor, the power controller may assign the receiver element to a small number of subframes. Shut off after period. The length of the period is determined by the number of OFDM symbols that contain the reference signal required for proper channel integration and assigned data burst detection. The receiver determines whether it is preferable to process the reference signal of the subsequent subframe based on, for example, channel conditions and burst parameters.
If the current subframe includes an assignment for the UE, and if the subsequent subframe is a downlink subframe that the terminal is required to monitor, the power controller receives until the beginning of the subsequent subframe. Keep vessel elements in operation. The receiver may use the reference signal of the subsequent subframe for channel integration for the current subframe.

  In LTE, the reference signal is typically placed in the first and third OFDM symbols from the end of each slot that is 6-7 symbols long. A sub-frame typically consists of two slots. For example, when the base station eNodeB uses two or more transmission antennas, the second OFDM symbol in the subframe is also used to transmit the reference signal. The PDCCH is typically arranged in the first to third OFDM symbols. Therefore, before the subframe (before the burst) if the receiver needs additional reference signals for proper PDCCH detection in addition to the first (possibly second) OFDM symbol. The margin of at least three symbols is required. In addition, the margin after the sub-frame (after the burst) must be set to receive the first (or first two) symbols of the next sub-frame. The previous setting of the sub-frame is appropriate when the previous sub-frame is a sub-frame of a downward link. The setting after the sub-frame is appropriate when the subsequent sub-frame is a sub-frame of a downward link.

Using the foregoing description Figure 4, PDCCH region of the sub-frame having a burst allocated to the UE begins to time T _1. Burst is completed in time _{T 2.} Before margin sub frame that was used to acquire the additional reference signal is displayed as N _1, the margin after the sub-frame is displayed as N _2. The total operating time (counted in symbols) of the RF receiver is _therefore W = N ₁ + N _ALLOC + N ₂ . The power controller adjusts the activation and deactivation times of other receiver elements accordingly. The idea and method for determining the values of N ₁ and N ₂ in LTE is similar to the method described above for WiMAX.

FIG. 7 is a flowchart illustrating a method for activating and shutting down elements of an LTE customer equipment UE by the power controller 56 according to another embodiment of the present invention. Initially, ie before the time of each downlink subframe 100 when the UE receives the downlink signal from the base station eNodeB, the power controller is required to receive and decode the signal in the initial activation step 114. The element of the active customer equipment UE. Initial activation is similar to step 80 of FIG.
Once the appropriate receiver element is activated, the UE receives and decodes the downlink PDCCH in the PDCCH region 104 time in a PDCCH reception step 116. The UE decodes the PDCCH region to identify the frequency and modulation parameters of the burst 112 assigned to the customer equipment UE from the base station eNodeB. In order to minimize power consumption, the power controller 56 shuts down the UE's receiving elements in an initial shut down step 118 as soon as the downlink PDCCH is decoded. For example, if the base station eNodeB has not assigned any downlink resources to the UE in the current downlink subframe 100, the power controller 56 blocks the receiving element. In this case, the receiving element of the UE maintains the blocking state until the next subframe (or until the time of the margin before the subframe of the next subframe).

The power controller 56 continuously determines the signal-to-noise ratio SNR as well as the time and bandwidth coherence in the SNR and coherence determination step 120. The coherence calculation is performed using any of the methods described in FIG. 5 above. In LTE, the calculation of these coefficients is performed based on the reference signal, the synchronization signal, the PDCCH sub-carrier and / or the data sub-carrier obtained from the previous sub-frame.
Accumulated signal to noise ratio at step 120, using the time and bandwidth coherence, the power controller 56, calculated in the sub-frame margin calculation step 124, the margin before and after the sub-frame, the N ₁ and N ₂ To do. As mentioned above, the power controller identifies the previous and subsequent subframes and / or takes into account the allocation of these subframes to UEs when calculating the margin before and after the subframes. Also good.
As mentioned in the description of FIG. 5, the margins before and after the subframe may be calculated by evaluating a predefined function, typically stored in the power controller 56 in the form of a look-up table. Good. Any function or method described in step 86 of FIG. 5 may be used for this purpose.

Using the margin values before and after the sub-frame calculated in step 124, the power controller 56 causes the RF receiver 30 to move the RF receiver 30 to the time N ₁ symbols before the start of the sub-frame in a sub-frame activation step 132. To start. The frequency synthesizer 34 is activated slightly before this time if it was previously shut off. The power controller also activates the A / D converter 36 and the digital physical layer interface PHY 40 to process the signal output from the RF receiver. The MAC processor 52 may be activated later at time T ₁ after the PDCCH symbols and / or allocated data bursts are actually decoded by the FEC 50.
In the data reception step 136, the RF receiver 30 and the adjunct elements of the customer equipment UE receive signals during the total operating time W = N ₁ + N _ALLOC + N ₂ . During this time, the digital physical layer interface PHY 40 updates the channel characteristic integration and processes the signal to demodulate the data on the signal sub-carrier using the channel integration.
When the margin after the sub-frame ends, at a time after symbol N ₂ after the end of burst 112, power controller 56 shuts off RF receiver 30 in a block step 140 after the sub-frame. The frequency synthesizer 34 and the A / D converter 36 are also shut off at this point.
Typically, the PHY 40 and the MAC processor 52 are cut off after a while after the processing of the data transmitted in the burst 112 is completed. The receiving element of the customer equipment UE remains blocked until the next downlink sub-frame where the UE may receive data.

  Although the embodiments described above relate to certain aspects of WiMAX and LTE systems and protocols, the principles of the present invention may be applied mutatis mutandis to systems using other multiple access radio standards. The embodiments described above are referred to by way of example, and the invention is not limited to what has been described and illustrated herein. Rather, the scope of the present invention includes combinations, sub-combinations, variations, and modifications of the various features described above, which would occur to those skilled in the art upon reading the above description, and are not found in the prior art.

20: Wireless network system 22: Base station, BS, eNodeB
24: Wireless terminal
30: RF receiver 32: Antenna, double antenna 34: Frequency synthesizer 36: A / D converter
38: Digital processing circuit 40: Digital physical layer interface, PHY
42: Digital forward terminal 44: Fast Fourier transform (FET) computing unit 46: Detector 48: Channel estimator, CE
50: Forward error corrector, FEC
52: MAC processor 54: Allocation calculator 56: Power controller 58: Permutation 60: Down link frame 62: Up link frame 64: Preamble 66: Map area 68, 108: Data area 70, 112: Burst 100: Sub Frame 104: PDCCH region

Claims (34)

A radio frequency (RF) receiver;
Wherein the RF receiver is configured to receive a down-converted RF signal to generate an output signal;
The RF signal consists of a lower link frame,
Each lower link frame has an allocation area with at least one data area;
The allocation area includes instructions for time allocation in the data area;
Downlink data is transmitted to the terminal within the time allocation period,
An analog / digital (A / D) converter connected to convert the output signal into a stream of digital samples;
Processing the digital samples to identify the time allocation in response to the indication in the allocation region, and recovering the downlink data within the time of the identified time allocation, while Digital processing circuitry connected to shut off an RF receiver in at least one time interval other than the time of the identified time allocation within the downlink link;
A terminal used for a wireless network characterized by including: The digital processing circuit includes:
A digital physical layer interface (PHY);
A media connection control (MAC) processor;
A power controller that, in addition to the RF receiver, shuts off at least one digital element of the terminal in the at least one time interval;
Consists of
Here, the at least one digital element is selected from an element group consisting of the A / D converter, the PHY, and the MAC arithmetic processor.
The terminal according to claim 1. The time allocation has a start time and an end time;
The digital processing circuit shuts off the RF receiver after receiving the indication at the time of the allocation region and traces the start time of the allocation by a first margin at a first time. And delaying the allocation end time by a second margin, and shutting off the RF receiver at a second time. Terminal. The digital processing circuit processes the digital samples in a first portion of the downlink to determine one or more characteristics of a radio channel on which the RF signal is received;
The terminal according to claim 3, wherein the terminal is configured to determine the first and second margins corresponding to the one or more characteristics.   The terminal of claim 4, wherein the one or more characteristics include channel coherence characteristics.   The coherence characteristic of the channel includes time coherence and bandwidth coherence, and the first and second margins increase when the time coherence increases and the bandwidth coherence decreases. 5. The terminal according to 5.   The one or more characteristics include a signal-to-noise ratio (SNR) of the wireless channel, and the first and second margins increase as the signal-to-noise ratio (SNR) of the wireless channel decreases. The terminal according to claim 4.   The downlink frame includes a preamble preceding the allocation region, and the digital processing circuit processes the digital samples within the preamble time to determine the one or more characteristics of the radio channel. The terminal according to claim 4, wherein the terminal is configured to.   The digital processing circuit is connected to determine the first margin for time allocation in a particular down link frame corresponding to a single frame preceding the specific down link frame; The terminal according to claim 3, wherein: The digital processing circuit includes:
Determining whether a frame preceding the specific downward link frame includes another downward link frame;
Determining whether a frame preceding the specific downlink link frame includes another time allocation for the terminal;
The terminal according to claim 9, wherein the terminal is connected to determine the first margin in response to executing at least one action step selected from a group of action steps consisting of .   The digital processing circuit determines the second margin for time allocation within a specific downlink link frame corresponding to a frame following the specific downlink link frame. 3. The terminal according to 3.   The digital processing circuit is connected to determine the second margin in response to determining whether the frame following the specific lower link frame includes another lower link frame. The terminal according to claim 11, wherein:   The digital processing circuit determines that no time is allocated for transmission to the terminal within the time period of a specific downlink link, and in accordance with the determination, the RF receiver is configured to transmit the RF receiver to the specific downlink link frame. 3. The terminal according to claim 1, wherein the terminal is configured to block all data areas within a period of time.   The terminal according to claim 1 or 2, wherein the downlink link frame is transmitted from one base station in conformity with the IEEE 802.16 standard.   15. The digital processing circuit is connected to identify the time allocation by decoding one downward link map message transmitted in the allocation region. Terminal.   The terminal according to claim 1 or 2, wherein the downlink link frame is transmitted according to a third generation partnership project-long term development (3GPP-LTE) by an extended NodeB (eNodeB).   The digital processing circuit is connected to identify the time allocation by decoding a physical downlink control channel (PDCCH) symbol transmitted in the time allocation region. Terminal. Receiving and downconverting a radio frequency (RF) signal using an RF receiver of the wireless terminal to generate an output signal;
Here, the RF signal consists of a lower link frame,
Each lower link frame has an allocation area with at least one data area;
The allocation area includes one indication of one time allocation in the data area;
Downlink data is transmitted to the terminal within the time allocation period,
Converting the output signal into a stream of digital samples;
Identifying the time allocation in response to the indication in the allocation region and processing the digital samples to recover the downlink data within the time of the identified time allocation, while the RF Shutting off the receiver in at least one time interval of time outside the identified time allocation within the downlink link;
A method of communication comprising the steps of: Shutting off at least one digital element of the terminal in the at least one time interval in addition to the RF receiver;
The at least one digital element is selected from an element group consisting of an analog / digital (A / D) converter, a digital physical layer interface (PHY), and a media connection control (MAC) processor. The method according to claim 18. The time allocation has a start time and an end time;
The step of shutting off the RF receiver comprises shutting off the RF receiver after the digital processing circuit receives the indication within the time of the assigned region, and setting the start time of the time assignment to a first margin. Controls to start the RF receiver at a first time, going back by minutes, and shut off the RF receiver at a second time, ending the time allocation end time by a second margin 20. The method according to claim 18 or 19, comprising the step of:   Controlling the RF receiver includes processing the digital samples in a first portion of the downlink to determine one or more characteristics of a radio channel on which the RF signal is received; 21. The method of claim 20, comprising determining the first and second margins corresponding to the one or more characteristics.   The method of claim 21, wherein the one or more characteristics include a coherence characteristic of a channel.   The coherence characteristic of the channel includes time coherence and bandwidth coherence, and the first and second margins increase when time coherence increases and bandwidth coherence decreases. the method of.   The one or more characteristics include a signal-to-noise ratio (SNR) of the wireless channel, and the first and second margins increase as the signal-to-noise ratio (SNR) of the wireless channel decreases. The method of claim 21.   The downlink frame includes a preamble that precedes the allocation region, and the step of processing the digital sample includes determining the digital channel within the time of the preamble to determine the one or more characteristics of the radio channel. The method of claim 21, comprising processing the sample.   Controlling the RF receiver includes determining the first margin for time allocation in a particular downlink link corresponding to a frame preceding the particular downlink link. 21. The method of claim 20, wherein: Determining the first margin comprises:
Determining whether a frame preceding the specific downward link frame includes another downward link frame;
Determining whether a frame preceding the specific downward link frame includes another time allocation for the terminal;
27. The method of claim 26, comprising performing at least one action step selected from a group of action steps consisting of:   Controlling the RF receiver includes determining the second margin for a time allocation within a particular downlink link corresponding to a frame following the particular downlink link. 21. The method of claim 20, wherein:   29. The step of determining the second margin includes determining whether the frame following the specific downward link frame includes another downward link frame. The method described.   Processing the digital samples comprises determining that no time has been allocated for transmission to the terminal within a particular downlink link time, and in accordance with the determination, the RF receiver is configured to: 20. A method according to claim 18 or 19, comprising the step of blocking all data regions within the particular down link frame for a period of time.   The method according to claim 18 or 19, wherein the downlink link frame is transmitted from one base station in accordance with the IEEE 802.16 standard.   32. The processing of claim 31, wherein processing the digital samples includes identifying the time allocation by decoding a down link map message transmitted in the allocation region. the method of.   20. The method according to claim 18 or 19, wherein the lower link frame is transmitted according to a third generation partnership project-long term development (3GPP-LTE) by an extended NodeB (eNodeB).   The processing of the digital samples includes identifying the time allocation by decoding physical downlink control channel (PDCCH) symbols transmitted in the time allocation region. The method described in 1.

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