CN101150828B - Method and system for detecting quick paging channel by using signal-to-noise ratio correlation threshold - Google Patents

Abstract

Methods and systems for detecting paging indicators using a multi-level and multi-threshold detection mechanism so that mobile terminals can be properly taken out of idle mode are disclosed. The method of the present invention determines whether a first indicator metric corresponding to a first paging indicator is between first and second predetermined thresholds after receiving the first paging indicator. If so, a second indicator metric is derived from the second paging indicator, and the predetermined function of the first and second paging indicator metrics is again compared to a third predetermined threshold, wherein the first and second predetermined thresholds are based on the square root of the signal-to-noise ratio of the first paging indicator, and the third predetermined threshold is based on the square root of the signal-to-noise ratio corresponding to the second paging indicator.

Description

Method and system for detecting quick paging channel by using signal-to-noise ratio correlation threshold

technical field

The present invention relates generally to wireless communication systems, and more particularly to methods and systems for detecting the presence of switch signaling in wireless communication networks.

Background technique

The Quick Paging Channel (QPCH) is an uncoded channel used in CDMA (Code Division Multiple Access) based telecommunication systems to convey switch signaling. This channel conveys various indicators like paging indicators, broadcast indicators, and configuration change indicators. The following discussion will use a specific indicator like a paging indicator as an example, however, it should be understood that anything that can be applied to a paging indicator can also be applied to other indicators transmitted by a QPCH.

In a wireless communication network, when there are neither voice nor data calls, the mobile terminal remains in an idle state to save battery power. In the idle state, the mobile terminal periodically wakes up every period of time, usually on the order of milliseconds, and monitors the paging indicator to detect whether there is a page for the mobile terminal. A relatively simple predetermined algorithm is typically used to determine whether the paging indicator indicates that there is an ongoing or imminent voice or data call. If the result of the predetermined algorithm is positive, the mobile terminal switches on to decode the information transmitted over the common channel which may contain dedicated or broadcast messages at intervals of up to 100 ms. If the final determination according to a simple algorithm is negative, the mobile terminal returns to a "sleep mode", during which most of the mobile terminal Parts are disconnected to save battery power. As is known to those skilled in the art, the more often a mobile terminal decodes information in a common channel, the more power the mobile terminal must consume. Therefore, there is a need to increase the latency, or amount of time the mobile terminal is in "sleep mode".

To increase latency, a wireless communication system that periodically communicates with a mobile terminal transmits the same paging indicator several times over time to indicate whether there is a page for the mobile terminal. For example, 3rd Generation Partnership Project 2 (3rd Generation Partnership Project 2) describes a Quick Paging Channel designed for this purpose in a CDMA2000 environment. For related content, please refer to "Physical Layer Standard for CDMA2000 Spread Spectrum Systems" ("Physical Layer Standard for CDMA2000 Spread Spectrum Systems", 3GPP2C.S0002, March, 2000). Also refer to "The upper layer (layer 3) of CDMA2000 Spread Spectrum Systems (2000) ) signaling standard ("Upper Layer (Layer3) Signaling Standard for CDMA2000 Spread Spectrum Systems (2000)", 3GPP2C.S0005, March, 2000). The QPCH indicator is generally on/key controlled to reduce transmission power. The paging indicator is used to signal to the mobile terminal the presence of a paging message during a predetermined paging slot in the QPCH. If the paging indicator is on, the mobile terminal should be awake and able to receive pages. If the paging indicator is off, the mobile terminal can remain in an idle state to save power. This indicator is sent repeatedly to obtain time fading diversity information.

To conserve battery power, it is critical to reliably and efficiently detect the presence of the paging indicator. Due to the presence of noise and fading of over-the-air communications, the signal-to-noise ratio (SNR) can become very low, making any detection mechanism challenging. There are generally two types of paging-related errors. Type I errors, ie, false alarm errors that may cause false alarms, which in turn cause more battery power to be drained, incorrect page detection. Type II errors, ie lost errors for incorrect detection of lost voice/data calls. In wireless communication systems, detection mechanisms have to be designed to minimize false alarms without increasing the loss rate exponentially.

Single-stage detection mechanisms are disclosed in prior art references, where a threshold is set for a given false alarm and the probability of detection is maximized. See "Fundamentals of Statistical Signal Processing: Detection Theory", PrenticeHall PTR, ^1st Edtion, March 1993 for more. However, since only a single threshold is used while the channel gain ratio is changing, this mechanism cannot realistically minimize both false alarm and loss rates for multi-level paging indicator detection. Although other existing methods solve some of the above-mentioned problems, they cannot effectively detect paging indicators in multiple stages.

Existing paging detection methods cannot utilize channels with known signal-to-noise ratio (SNR) to improve detection performance. In fact, most designs are usually made for worst-case scenarios. If a design keeps the probability of false alarm constant over the entire operating range, then the probability of lost detection will be almost zero at high SNR. Even though it is possible to reduce the false alarm probability to a value lower than the design target with little sacrifice of loss detection probability at high SNR, existing methods cannot use different thresholds to Change detection performance.

If there is no effective detection mechanism, battery power will be consumed more and high loss rate is unavoidable, resulting in poor communication performance. Therefore, there is a need to improve existing methods of detecting paging indicators.

Contents of the invention

In view of the above circumstances, the present invention provides a method for detecting a paging indicator in a wireless communication system.

Disclosed herein are methods and systems for detecting paging indicators using a multi-stage and multi-threshold detection mechanism so that a mobile terminal can be properly brought out of idle mode. After receiving the first paging indicator, it is determined whether a first indicator metric corresponding to the first paging indicator is between a first and a second predetermined threshold. If so, derive a second indicator metric from the second paging indicator, and again compare the non-decreasing function of the first and second paging indicator metrics with a third predetermined threshold, wherein the first and second predetermined The threshold is based on the square root of the signal-to-noise ratio of the first paging indicator, and the third predetermined threshold is based on the square root of the signal-to-noise ratio corresponding to the second paging indicator.

This paper discloses a method for detecting a paging indicator through a paging channel in a wireless communication system, so as to make a mobile terminal leave an idle mode. The method comprises receiving a first paging indicator I1; determining first and second thresholds T ₁ and T ₂ based on the signal-to-noise ratio of the first paging indicator, if the signal-to-noise ratio of the first paging indicator is lower than a predetermined initial signal-to-noise ratio threshold, then the first and second thresholds are different, otherwise, the first and second thresholds are the same; deriving a first paging indicator metric _x1 corresponding to the first paging indicator; In the first stage, it is determined whether the mobile terminal will leave idle mode according to the comparison between x ₁ and T ₁ and T ₂ respectively, if x ₁ is less than T ₁ , then the mobile terminal remains in idle mode; if x ₁ is greater than or equal to T ₂ , the mobile terminal leaves the idle mode; if x ₁ is between T ₁ and T ₂ , it means that it cannot be determined whether the mobile terminal leaves the idle mode in the first stage, and the second paging indicator I2 is derived according to the received second The paging indicator measures _x2 , and in the second stage it is determined whether the mobile terminal will come out of idle mode from a comparison between a third threshold _T3 and a non-decreasing function of _x1 and _x2 , if _x1 and _x2 If the non-decreasing function is less than T ₃ , the mobile terminal remains in the idle mode, otherwise, the mobile terminal leaves the idle mode; among them, T ₁ represents the limit of tolerating lost calls and T ₂ represents the limit of tolerating false alarms, and T ₁ and T ₂ are based on is derived from the square root of the signal-to-noise ratio corresponding to the first paging indicator, and T3 is derived from the square root of the signal-to-noise ratio corresponding to the second paging indicator.

This paper discloses a system for detecting a paging indicator through a paging channel in a wireless communication system, so as to make a mobile terminal leave an idle mode. The system comprises a receiver for receiving first and second paging indicators I1 and I2; a threshold generator for determining first and second thresholds T _and T based on the signal-to-noise ratio of the first paging indicator _2. If the signal-to-noise ratio of the first paging indicator is lower than a predetermined initial signal-to-noise ratio threshold, the first and second thresholds are different, otherwise, the first and second thresholds are the same; the processor, for deriving a first paging indicator metric (x ₁ ) corresponding to the first paging indicator, or deriving a second paging indicator metric x ₂ from a received second paging indicator I2; a comparator for In the first stage, it is determined whether the mobile terminal will leave idle mode according to the comparison between x ₁ and T ₁ and T ₂ respectively, if x ₁ is less than T ₁ , then the mobile terminal remains in idle mode; if x ₁ is greater than or equal to T ₂ , the mobile terminal is out of idle mode; if x ₁ is between T ₁ and T ₂ , it means that it cannot be determined whether the mobile terminal is out of idle mode in the first level, and in the second level according to the third threshold T ₃ and x The comparison between the non-decreasing function of ₁ and _x2 determines whether the mobile terminal will come out of idle mode, if the non-decreasing function of _x1 and _x2 is less than _T3 , the mobile terminal remains in idle mode, otherwise, the mobile terminal comes out of idle mode ; where T ₁ represents the bound of tolerating lost calls and T ₂ represents the bound of tolerating false alarms, T ₁ and T ₂ are derived according to the square root of the signal-to-noise ratio corresponding to the first paging indicator, and T3 is derived according to is derived from the square root of the signal-to-noise ratio corresponding to the second paging indicator.

The structure and operation method of the present invention, as well as other objects and advantages of the present invention will be more clearly described through the following description of specific embodiments of the present invention with reference to the accompanying drawings.

Description of drawings

1 is a graph showing the difference in signal-to-noise ratio of paging indicators based on two target thresholds corresponding to false alarm probability and lost call probability according to one embodiment of the present invention;

Figure 2 is a flowchart illustrating the determination made for multi-stage paging indicator detection according to one embodiment of the present invention; and

Fig. 3 is a schematic diagram of hardware implementing multi-level paging indicator detection according to an embodiment of the present invention.

Detailed ways

A detailed description of a method and system for determining the presence of an indicator transmitted on a quick paging channel in a wireless communication network will be provided below. The subject matter set forth herein is applicable to wireless communication systems that multiplex signals utilizing time division multiplexing (TDM), code division multiplexing (CDM), and frequency division multiplexing (FDM) techniques. For illustration, a CDMA2000 system is used as an example. In wireless communication systems like CDMA2000 systems, several paging indicators are implemented. Those of ordinary skill in the art may understand a paging indicator as a signal for detecting the presence of a paging signal, and broadly define it as including the following paging indicator examples, but not limited thereto. For example, a Quick Paging Channel paging indicator is designed for the Quick Paging Channel (QPCH). Another quick paging channel configuration change indicator is designed for the common control channel (CCCH). Yet another Quick Paging Channel broadcast indicator is designed for the Broadcast Control Channel (BCCCH).

The invention estimates the SNR of the QPCH, and calculates the detection threshold according to the estimated SNR. The working range of SNR is divided into two ranges: a high SNR range and a low SNR range. For each range, a SNR-related threshold is used for a different decision mechanism. For example, in the high SNR range, due to the good signal quality, both the target loss of detection probability and the target false alarm probability can be satisfied with a single threshold. In fact, the high SNR range enables the detector to meet the detection performance between the probability of missing detection and the probability of false alarm with a single SNR correlation threshold. More specifically, a double decision mechanism is used in the high SNR range. In the low SNR range, it is not possible to satisfy both the target loss of detection probability and the target false alarm probability with a single threshold. Therefore, it is necessary to use two thresholds, which introduces a state of doubt or uncertainty. When the first paging indicator enters this suspect state, subsequent paging indicators are tested for detection, and possibly in combination with the first paging loss indicator. Therefore, a triple decision mechanism is used in the low SNR range.

According to one embodiment of the present invention, two paging indicators I1 and I2 are sent in each paging slot cycle in the CDMA2000 system, wherein I2 is the time-diversity counterpart of I1. These two indicators span the channel coherence length (approximately 20 ms) to achieve time diversity. Assume that the received symbol signal is expressed as _ri,k,l , where i is the paging indicator index (1 or 2 for I1 or I2, respectively), k is the index of the multipath including the diversity branch, and 1 is a quadrature phase shift keying (QPSK) symbol index, where QPSK should be understood as a digital frequency modulation technique for sending digital data on a communication channel, and its corresponding estimated radio channel information is a _{i, k, l} , a _{i , k, l} represent channel conditions. Then, the measurement metric corresponding to the display part of the paging indicator bar can be obtained through a predetermined combination method. For example, through the simple pilot weighted combination method, the three normalized measurement metrics (or paging indicator metrics) x ₁ , x ₂ and x ₃ are expressed as:

$x_1=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K1}{\mathrm{\&Sigma;}}}(\mathrm{Re}(a_{1,k,l}^{*}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l})+\mathrm{Im}(a_{1,k,l}^{*}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}))}{\mathrm{QPR}\&Center\; Dot;\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{\left|a_{1,k,l}\right|}^2}$ (equation 1)

$x_2=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K2}{\mathrm{\&Sigma;}}}(\mathrm{Re}(a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l})+\mathrm{Im}(a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}))}{\mathrm{QPR}\&CenterDot;\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{\left|a_{2,k,l}\right|}^2}$ (equation 2)

$x_3=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K1}{\mathrm{\&Sigma;}}}(\mathrm{Re}(a_{1,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l})+\mathrm{Im}(a_{1,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}))+\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K2}{\mathrm{\&Sigma;}}}(\mathrm{Re}(a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l})+\mathrm{Im}(a_{2,k,l}^{*}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}))}{\mathrm{QPR}(\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">K</figure-callout>}1}{\mathrm{\&Sigma;}}}{\left|a_{1,k,l}\right|}^2+\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">K</figure-callout>}2}{\mathrm{\&Sigma;}}}{\left|a_{2,k,l}\right|}^2)}$ (Equation 3)

Where K1 and K2 are the number of multipaths (including diversity branches) of I1 and I2 respectively, L is the number of QPSK symbols per paging indicator, QPR is the power ratio between the quick paging indicator and the pilot signal The ratio between , and is also called the channel gain notified by the base station. In the CDMA2000 system, QPR has the mathematical representation of QPR=10 ^{(QPCH_POWER_LEVEL_PAGE+3)/20} , and QPCH_POWER_LEVEL_PAGE is the paging indicator modulation symbol power level relative to the forward pilot channel also defined in the CDMA2000 standard.

It should be understood that the measurement metric is derived from the channel gain notified by the base station, and the estimated radio channel information is significantly better than the prior art. The above method may be referred to as a pilot weight combination method. With this method, the noise reduction weights are not explicitly specified to solve the noise problem since the effect of weighting is already achieved. As shown, since x ₁ , x ₂ and x ₃ are all functions of and normalized to QPR, there is a built-in inherent adaptation mechanism that can work with any communication system. The summation corresponding to the radio channel information represented by the above equation provides a normalization process so that the analysis can be simplified. It should also be understood that the measurement metric is not necessarily normalized, and in fact, the QPR may be taken into account while determining the threshold to which the measurement metric is intended to be compared (discussed further below). By combining QPR and Signal-to-Noise Ratio (SNR) when deriving and analyzing these measurement metrics and their corresponding thresholds, both channel conditions and channel configurations can be factored such that page detection can be fully adaptive to a variety of channel environment.

In another embodiment using the maximum ratio combining method, three similar normalized indicator metrics x ₁ , x ₂ and x ₃ are given as follows:

$x_1=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K1}{\mathrm{\&Sigma;}}}(\mathrm{Re}\left(\frac{a_{1,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}}{{\mathrm{\&sigma;}}_{1,k,l}^2}\right)+\mathrm{Im}\left(\frac{a_{1,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}}{{\mathrm{\&sigma;}}_{1,k,l}^2}\right))}{\mathrm{QPR}\&CenterDot;\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\frac{{\left|a_{1,k,l}\right|}^2}{{\mathrm{\&sigma;}}_{1,k,l}^2}}$ (Equation 1')

$x_2=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K2}{\mathrm{\&Sigma;}}}(\mathrm{Re}\left(\frac{a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}}{{\mathrm{\&sigma;}}_{2,k,l}^2}\right)+\mathrm{Im}\left(\frac{a_{2,k,l}^{*}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}}{{\mathrm{\&sigma;}}_{2,k,l}^2}\right))}{\mathrm{QPR}\&CenterDot;\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\frac{{\left|a_{2,k,l}\right|}^2}{{\mathrm{\&sigma;}}_{2,k,l}^2}}$ (Equation 2')

$x_3=\frac{\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K1}{\mathrm{\&Sigma;}}}(\mathrm{Re}\left(\frac{a_{1,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}}{{\mathrm{\&sigma;}}_{1,k,l}^2}\right)+\mathrm{Im}\left(\frac{a_{1,k,l}^{*}\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k,l}}{{\mathrm{\&sigma;}}_{1,k,l}^2}\right))+\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}(\mathrm{Re}\left(\frac{a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}}{{\mathrm{\&sigma;}}_{2,k,l}^2}\right)+\mathrm{Im}\left(\frac{a_{2,k,l}^{*}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{2,k,l}}{{\mathrm{\&sigma;}}_{2,k,l}^2}\right))}{\mathrm{QPR}(\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">K</figure-callout>}1}{\mathrm{\&Sigma;}}}\frac{{\left|a_{1,k,l}\right|}^2}{{\mathrm{\&sigma;}}_{1,k,\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">l</figure-callout>}}^2}+\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">K</figure-callout>}2}{\mathrm{\&Sigma;}}}\frac{{\left|a_{2,k,l}\right|}^2}{{\mathrm{\&sigma;}}_{2,k,l}^2})}$ (Equation 3')

是第i寻呼指示符、第k多径、和第1码元的噪声方差。在这种导出x₁、x₂和x₃的方法中，噪声用因子表示，并且还适当考虑了应用权重。一般说来，如果噪声较高，应用权重就应该低一些。从上面的度量中可以看出，噪声方差被放置在分母部分中，以表示“反比”关系。在这种最大比组合方法中，像上面说明的那样应用特定权重来降低噪声干扰，从而提高系统的性能。in,

is the noise variance of the ith paging indicator, the kth multipath, and the 1st symbol. In this method of deriving x ₁ , x ₂ , and x ₃ , the noise is represented by a factor, and weights are applied with due consideration. In general, if the noise is high, lower weights should be applied. As can be seen from the metrics above, the noise variance is placed in the denominator part to represent an "inverse" relationship. In this maximal ratio combining method, specific weights are applied as explained above to reduce noise interference and thus improve the performance of the system.

The effective signal-to-noise ratios (SNRs) of paging indicators I1 and I2 are referred to as SNR1 and SNR2, respectively. SNR3 is defined as the combined SNR of I1 and I2. In communication systems, those of ordinary skill in the art should understand that SNR often depends on the characteristics of the mobile terminal demodulator, channel conditions, and inherent noise. For this application, since the QPCH power can be known in advance according to the pilot channel power, SNR can be used interchangeably with Eb/Nt, and Eb/Nt is the ratio of energy per bit to effective noise spectral density.

Any decision rule for determining a paging indicator requires some form of SNR estimation. For example, SNR can be estimated from pilot signals. The total received power-to-interference ratio Ec _p /Io is expressed in decibels (dB), where Ec _p and Io are the pilot chip energy and the total received input power spectral density including both signal and interference, respectively. This ratio can be easily obtained from the mobile terminal searcher. The noise factor in terms of SNR is then given by:

SNR=QPCH_Ec/Ioc=(QPR) ² *Ee _p /Io (Equation 4)

Among them, Ec _p and Ioc are the chip energy of the pilot signal and the power spectral density of band-limited white noise and interference from other cells including multipath interference. QPCH_Ec is the total chip energy of the paging indicator. Since I _o =I _or +I _oc , for bad radio channel conditions of I _or ≌I _oc , an approximate formula I _oc ≌I _o /2 can be obtained, where the term I _or is the post-transmission power spectral density of the channel. In the forward link, I _or is the total transmit power spectral density of the base station under soft handoff. In the CDMA2000 system, I _or /I _oc is called a geometry factor.

Therefore, the approximate formulas for the SNR of I1 and I2 are as follows:

SNR1=2R*(QPR) ² *Ec _p1 /I _o1 (Equation 5)

SNR2=2R*(QPR) ² *Ec _p2 /I _o2 (Equation 6)

The approximate formula for the SNR of the combination I1 and I2 is as follows:

SNR3=2R*(QPR) ² *[Ec _p1 /I _o1 +Ec _p2 /I _o2 ] (Equation 7)

Wherein, for the CDMA2000 system, for the quick paging channel data rate of 4,800 bps or 2,400 bps, R=256 or 512. When the signal is equal to noise plus interference, the approximation error is approximately zero. The estimation is relatively accurate when the geometry factor (I _or /I _oc ) is low (eg, from -5db to 5dB), which corresponds to low SNR regions and is mainly important for detection and decoding. In the decision rules discussed below, the decision threshold is constant in high SNR regions corresponding to high geometry factors.

The estimated indicator SNR is compared to an SNR threshold that determines the boundary between the high SNR range and the low SNR range. The SNR threshold is the SNR at which both the target false alarm probability and the target loss detection probability are satisfied in the first indicator detection. Given the probability of false alarm (P _F ) and the probability of missed detection (P _MD ), the SNR threshold that divides the SNR range into high SNR or low SNR is obtained by solving the following joint equation:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; T</span>}}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dx</span>}$

$P_{\mathrm{MD}}=\frac{1}{\sqrt{2\mathrm{\&pi;}}}{\&Integral;}_{-\&infin;}^{T-\sqrt{\mathrm{SNR}}}\exp (-\frac{x^2}{2})\mathrm{dx}$ (Equation 8)

where "T" is the threshold and x is the indicator. In general, T can be derived from the predetermined false alarm probability, and the SNR in the above equation can be derived from T and the predetermined loss detection probability. Thus, the threshold is SNR dependent.

Figure 1 is a graphical representation showing selected regions of the high SNR range according to one example of the present invention. As shown in Figure 1, the SNR-related threshold can be expressed as a function of the square root of the indicator SNR (horizontal axis). If the threshold is expressed as a linear function, the selected detection performance can be obtained by adjusting the slope and intercept of the threshold. In the high SNR range, only one detection threshold is required. The threshold (T _f ) that satisfies a given probability of false alarm is a constant that is independent of SNR (shown by the dashed line), while the threshold (T _d ) that satisfies a given probability of loss of detection is a linear function of the square root of SNR (shown by the solid line ). The detection threshold in the high SNR range can be seen as a non-decreasing function of the square root of the SNR in the region between _Tf and _Td to the right beyond the intersection of _Tf and _Td . This particular region, to which any detection threshold of high SNR may coincide, is shown shaded for the sake of illustration.

When in the low SNR range, the detection is a multi-stage detection mechanism that detects at least two quick paging indicators in combination. For detection of paging indicators from SNR, two thresholds _T1 and _T2 are needed, but for combined paging indicator based detection a third threshold _T3 is needed. T ₁ represents the bound to tolerate lost calls, and T ₂ represents the bound to tolerate false alarms. According to an example of the invention, the detection threshold determination in the low SNR range can be chosen as:

T ₁ =T _d

T ₂ = T _f (Equation 9)

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

where f is a non-decreasing function.

If the threshold T ₃ is expressed as a linear function, T ₃ can be displayed as:

${\mathrm{<figure-callout\; id="3"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_3=a_3({\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1,{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2,\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_1})\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_2}+b_3({\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1,{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2,\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_1})$ (equation 10)

Here, the SNR range for a given region (E _s /N _t ) 1 is divided into several regions as a ₃ and b ₃ are precomputed and stored in memory.

FIG. 2 provides a flowchart 100 illustrating an improved detection process according to one embodiment of the present invention. In Fig. 2, x ₁ and x ₂ are the first and second indicator detection metrics, and x ₁₂ is the combined indicator metric (x ₁₂ =w1*x ₁ +w2*x ₂ , where w1 and w2 are possible select the weight). (E _s /N _t ) ₁ is the energy-to-noise ratio of the first indicator symbol, and (E _s /N _t ) ₂ is the energy-to-noise ratio of the second indicator symbol. SNR_threshold is the overall SNR threshold, and T ₁ , T ₂ and T ₃ are the three thresholds as discussed above. a ₁ , a ₂ and a ₃ are constants representing the slope of the linear function, and b ₁ , b ₂ and b ₃ represent the intercept between T _f and T _d .

Flowchart 100 begins with a first level entering decision step 102 . If the total SNR of the QPCH (i.e., QPCH(E _s /N _t ) ₁ ) is not less than the predetermined total SNR threshold SNR_threshold, then the values of T ₁ and T ₂ are set to the same value, and in step 104, in the mathematical determined as:

${\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1={\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2=a_{12}\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_1}+b_{12}$ (Equation 11)

On the other hand, if the total SNR of the QPCH (i.e., QPCH(E _s /N _t ) ₁ ) is less than the predetermined total SNR threshold SNR_threshold, the values of T ₁ and T ₂ are set to different values in step 106, and in the mathematical determined as:

${\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1=a_1\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_1}+b_1$ and ${\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_2=a_2\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_1}+b_2$ (Equation 12)

It can be seen that _T1 and _T2 are set to different values based on different weight constants a and b, although still only according to the first indicator. With T ₁ and T ₂ initially set, the process goes to step 108 where the first indicator detection metric x ₁ is compared with the set T ₁ , if it is less than T ₁ , the mobile terminal should stay In idle state (step 110). If it is determined in step 108 that the first indicator detection metric x ₁ is greater than T ₁ , then in step 112 it is further determined whether the first indicator detection metric x ₁ is greater than or equal to T ₂ . If yes, then in step 114 there is a strong indication that the mobile terminal should be turned on. This means that if the first indicator detection metric x ₁ is greater than both T ₁ and T ₂ , it is unlikely to be a false alarm.

In case _x1 is between _T1 and _T2 , a second indicator detection metric _x2 is introduced for further detection. The second indicator detection metric _x2 is derived from the second paging indicator I2, which may be the temporal counterpart of the first paging indicator I1. The combining threshold _T3 is first derived from the square root of the SNR of the second paging indicator. That is to say,

${\mathrm{<figure-callout\; id="3"\; label="T"\; filenames="S071D7390720070806E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}_3=a_3\sqrt{{({\mathrm{E.}}_{\mathrm{the\; s}}/N_t)}_2}+b_3$ (Equation 13)

Wherein, both a ₃ and b ₃ are predetermined constants that can be stored in the mobile terminal in advance. The selected non-decreasing function f as a function of _x1 and _x2 as its variables is then compared to _T3 in step 116 . If it is determined in step 116 that the threshold _T3 is below, then the mobile terminal is switched off. Otherwise, in step 120 the mobile terminal is turned on. So far, the two-level indicator detection process is completed.

It should be noted that in step 102, SNR_threshold is an artificial division line that cuts the SNR working range into a high SNR range and a low SNR range. As mentioned above, a single threshold is sufficient to satisfy both the target loss of detection probability and the target false alarm probability if in the high SNR range. On the other hand, if it is below the overall threshold, it is considered to be in the low SNR range and a triple decision process needs to be applied. Two different thresholds _T1 and _T2 introduce a suspicion that _x1 is larger than _T1 but smaller than _T2 . At this point, it stands to reason that, as seen from step 116 above, a further determination should be introduced and the second indicator used to further decide whether the mobile terminal should be switched on or not. It should also be noted that the values of _T1 , _T2 and _T3 are all somewhat based on the square root of the SNR of the respective paging indicators.

FIG. 3 illustrates a hardware schematic 300 containing various components to accomplish paging indicator detection. In the mobile terminal there is a signal receiver or detector 302 that receives the QPCH signal, as well as other signals from other communication channels like the pilot channel. At least one comparator module 304 is located in the mobile terminal, which performs multiple rounds of comparison as described above. The SNR calculator 306 provides the SNR value from the received signal, and the threshold generator 308 performs the process of calculating the required threshold. The comparator cooperates with a processing unit like the microcontroller 310 to make the comparison when the SNR and the threshold are fed into the comparator from the detection signal. According to the comparison result, the controller 310 provides a decision signal for the mobile terminal to wake up or stay in an idle state. It should also be understood that the various calculators and generators can be implemented by hardware or software means. For example, all processing power may be provided by a microprocessor like a controller in a mobile terminal without being broken down into different units. Alternatively, certain modules may be implemented by discrete hardware modules operating independently of the controller.

The above illustrations provide many different embodiments or embodiments for implementing different features of the invention. Specific embodiments are described to illustrate the components and processes of the present invention. These are, of course, only examples and are not intended to limit the invention to anything other than what is described in the claims.

While the invention has been illustrated and described herein as embodied in one or more specific examples, the invention is not limited to the details shown since there may be no departure from the spirit of the invention and the scope of the claims or equivalents. Various modifications and structural changes have been made. Accordingly, it is proper to read the appended claims broadly and in a manner consistent with the scope of the present invention as set forth in the appended claims.

Claims (10)

1. A method for detecting a paging indicator through a paging channel in order to bring a mobile terminal out of an idle mode in a wireless communication system, the method comprising:

receiving a first paging indicator I1;

determining first and second thresholds T based on signal-to-noise ratio of first paging indicator₁And T₂The first and second thresholds are different if the signal-to-noise ratio of the first paging indicator is below a predetermined initial signal-to-noise ratio threshold, otherwise the first and second thresholds are the same;

deriving a first paging indicator metric x corresponding to the first paging indicator₁；

In the first stage according to x₁Respectively with T₁And T₂The comparison between determines whether the mobile terminal will leave the idle mode, if x₁Less than T₁Then the mobile terminal remains in the idle mode; if x₁Greater than or equal to T₂The mobile terminal is separated from the idle mode; if x₁At T₁And T₂In between, indicating that it cannot be determined in the first stage whether the mobile terminal has left the idle mode, a second paging indicator metric x is derived from the received second paging indicator I2₂(ii) a And

in the second stage according to a third threshold value T₃And x₁And x₂Determines whether the mobile terminal will leave the idle mode if x is₁And x₂Is less than T₃If not, the mobile terminal is separated from the idle mode;

wherein, T₁Indicating a margin and T for tolerating a lost call₂Indicating a margin for tolerance of false alarms, T₁And T₂Is derived from the square root of the signal-to-noise ratio corresponding to the first paging indicator, and T3 is derived from the square root of the signal-to-noise ratio corresponding to the second paging indicator.

2. The method of claim 1, wherein the steps of determining the first and second thresholds further comprise thresholding T if the signal-to-noise ratio of the first paging indicator is below a predetermined initial SNR threshold₁And T₂Is defined as

And

wherein,

is the signal-to-noise ratio, a, corresponding to the first paging indicator₁、a₂、b₁、b₂Is a predetermined constant.

3. The method of claim 1, wherein the steps of determining the first and second thresholds further comprises applying T if the signal-to-noise ratio of the first paging indicator is above a predetermined initial signal-to-noise ratio threshold₁And T₂Is defined asWherein,

is the signal-to-noise ratio, a, corresponding to the first paging indicator₁₂And b₁₂Is a predetermined constant.

4. The method of claim 1, wherein a third threshold T₃Is determined as

Wherein,

is the signal-to-noise ratio corresponding to the second paging indicator, and a₃And b₃Is a predetermined constant.

5. The method of claim 1, wherein the second paging indicator I2 is a time diversity counterpart of the first paging indicator I1.

6. A system for detecting a paging indicator through a paging channel in order to bring a mobile terminal out of an idle mode in a wireless communication system, the system comprising:

a receiver for receiving first and second paging indicators I1 and I2;

a threshold generator for determining the first and second thresholds T based on the signal-to-noise ratio of the first paging indicator₁And T₂The first and second thresholds are different if the signal-to-noise ratio of the first paging indicator is below a predetermined initial signal-to-noise ratio threshold, otherwise the first and second thresholds are the same;

a processor for deriving a first paging indicator metric (x) corresponding to a first paging indicator₁) Or derive a second paging indicator metric x from the received second paging indicator I2₂；

A comparator for in a first stage according to x₁Respectively with T₁And T₂The comparison between determines whether the mobile terminal will leave the idle mode, if x₁Less than T₁Then the mobile terminal remains in the idle mode; if x₁Greater than or equal to T₂The mobile terminal is separated from the idle mode; if x₁At T₁And T₂In the first stage, it is not determined whether the mobile terminal is out of the idle mode, and in the second stage, it is determined according to a third threshold value T₃And x₁And x₂Determines whether the mobile terminal will leave the idle mode if x is₁And x₂Is less than T₃If not, the mobile terminal is separated from the idle mode;

wherein, T₁Indicating a margin and T for tolerating a lost call₂Indicating a margin for tolerance of false alarms, T₁And T₂Is derived from the square root of the signal-to-noise ratio corresponding to the first paging indicator, and T3 is derived from the square root of the signal-to-noise ratio corresponding to the second paging indicator.

7. The system of claim 6, wherein the second paging indicator I2 is a time diversity counterpart of the first paging indicator I1.

8. The system of claim 6, wherein if the first paging indicatorThe signal-to-noise ratio is lower than the predetermined initial signal-to-noise ratio threshold, the first and second threshold values T₁And T₂Is defined as

And

wherein,

is the signal-to-noise ratio, a, corresponding to the first paging indicator₁、a₂、b₁、b₂Is a predetermined constant.

9. The system of claim 6, wherein the first and second thresholds T are based on the signal-to-noise ratio of the first paging indicator being above a predetermined initial signal-to-noise ratio threshold₁And T₂Are set to be identical and set to

Wherein,is the signal-to-noise ratio, a, corresponding to the first paging indicator₁₂And b₁₂Is a predetermined constant.

10. The system of claim 6, wherein the third threshold T₃Is determined asWherein,

is the signal-to-noise ratio corresponding to the second paging indicator, and a₃And b₃Is a predetermined constant.

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