1. Field of the Invention
The present invention relates to an evaluation device and method for providing a transceiver system with performance information thereof, more particularly to an evaluation device and method for providing a transceiver system, which models a channel thereof using Nakagami distribution, with performance information thereof.
2. Description of the Related Art
Referring to
In “Outage capacity analysis of multiuser diversity in MIMO antenna selection systems,” IEEE PIMRC' 2007, September 2007, pages 1-5, X. Zhang et al. proposed a method for evaluating performance of a transceiver system under the TAS/MRC scheme by using Rayleigh fading channels (see
Therefore, an object of the present invention is to provide an evaluation device and method adapted for appropriately evaluating performance of a transceiver system by using Nakagami channels to compute an outage capacity of the transceiver system.
Accordingly, an evaluation device of the present invention is adapted for providing a transceiver system with performance information thereof. The transceiver system includes a transmitter and a receiver, and models a channel between the transmitter and the receiver using Nakagami distribution with a fading parameter. The evaluation device comprises a signal-to-noise ratio (SNR) computing module, a capacity computing module, and an output module.
The SNR computing module is operable to set an average SNR for the channel between the transmitter and the receiver of the transceiver system, and to compute an expected value and variance of an effective SNR of the transceiver system according to the fading parameter and the average SNR. The capacity computing module is operable to compute an outage capacity of the transceiver system based upon the expected value and the variance of the effective SNR and a transmission outage parameter associated with a guaranteed transmission rate. The output module is operable to provide the transceiver system with the average SNR and the outage capacity as the performance information of the transceiver system.
According to another aspect, an evaluation method of this invention is adapted for providing a transceiver system with performance information thereof. The transceiver system includes a transmitter and a receiver, and models a channel between the transmitter and the receiver using Nakagami distribution with a fading parameter. The evaluation method is adapted to be implemented by an evaluation device, and comprises the steps of:
a) configuring the evaluation device to set an average SNR for the channel between the transmitter and the receiver of the transceiver system;
b) configuring the evaluation device to compute an expected value and variance of an effective SNR of the transceiver system according to the fading parameter and the average SNR;
c) configuring the evaluation device to compute an outage capacity of the transceiver system based upon the expected value and the variance of the effective SNR and a transmission outage parameter associated with a guaranteed transmission rate; and
d) configuring the evaluation device to provide the transceiver system with the average SNR and the outage capacity as the performance information of the transceiver system.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:
Referring to
In such a TAS/MRC scheme, there are a number LT×LR of possible channels each of which is defined by one of the transmit antennas 12 and one of the receive antennas 22. The channel estimator 23 of the receiver 2 is operable to provide the diversity unit 11 of the transmitter 1 with transmission qualities of the possible channels corresponding to the respective transmit antennas 12. Then, according to the transmission qualities, the diversity unit 11 of the transmitter 1 is operable to determine which one of the transmit antennas 12 will be used to transmit signals. The diversity unit 11 is further operable to transmit the signals to a selected one of the transmit antennas 12 for transmission of the signals to the receiver 2. After the receiver 2 receives the signals from the transmitter 1 through the receive antennas 22 thereof, the signals are transmitted to the synthesis unit 21. According to the transmission qualities of the channels between the selected one of the transmit antennas 12 and the receive antennas 22, the synthesis unit 21 is operable to weight the signals received by the receive antennas 22 so as to obtain a synthesized signal.
In “Analysis of transmit antenna select ion/maximal-ratio combining in Rayleigh fading channels,” IEEE Trans. Veh. Technol., Vol. 54, No. 4, pages 1312-1324, July 2005, Z. Chen et al. disclosed the use of Nakagami distribution (see
In Equation (1),
It should be noted that the fading parameter m of Nakagami distribution shown in
Further, referring to Equations (8.352.1), (8.351.2), (9.14.1) and (0.314) in “Table of Integrals, Series, and Products,” the term in
Equation (1) can be represented by the following Equation (2) for the fading parameter m that is greater than or equal to ½, and Equation (3) for the fading parameter m that is a positive integer.
In Equations (2) and (3),
for a positive integer n, β0=1, and
for a positive integer t.
From Equation (2), when the fading parameter m is greater than or equal to ½, an expected value μQ and variance σQ2 of an effective SNR of the transceiver system 100 can be expressed as Equations (4) and (5), respectively.
From Equation (3), when the fading parameter m is a positive integer, the expected value μQ and variance σQ2 of the effective SNR can be expressed as Equations (6) and (7), respectively.
According to “Outage capacity analysis of multiuser diversity in MIMO antenna selection systems,” IEEE PIMRC' 2007, pages 1-5, September 2007, proposed by X. Zhang et al., when the SNR of the synthesized signal is equal to Q, and the expected value and variance of the effective SNR are equal respectively to μQ and σQ2, a channel capacity C(Q) of the transceiver system 100 under the TAS/MRC scheme may be approximated to Equation (8), and an expected value μC and variance σC2 of the channel capacity may be approximated to Equations (9) and (10), respectively.
Further, according to the central limit theorem, values of the PDF of the channel capacity C(Q) may be approximated to Gaussian distribution. Regarding m=3, LT=3, and LR=2, Gaussian distribution is indicated by a solid line in
Moreover, with reference to “Outage capacity analysis of multiuser diversity in MIMO antenna selection systems” proposed by X. Zhang et al., the maximum channel capacity CB (i.e., the outage capacity) of the transceiver system 100 with a guaranteed transmission rate (100−B) % (i.e., the outage rate is B %, B being a transmission outage parameter associated with the guaranteed transmission rate) can be expressed as Equation (12).
In Equation (12), erfc−1(x) is an inverse function of a complementary error function erfc(x)=1−erf(x), and erf(x) is an error function,
The guaranteed transmission rate (100−B) % is defined as a ratio of a summation of values of the PDF of the channel capacity 0 to CB to a summation of values of the PDF of the channel capacity 0 to ∞.
From Equations (4) to (7) and (12), the outage capacity (i.e., the maximum channel capacity CB) of the transceiver system 100 under the TAS/MRC scheme can be obtained.
Referring to
The evaluation device 300 includes an SNR computing module 3, a capacity computing module 4 coupled to the SNR computing module 3, and an output module 5 coupled to the capacity computing module 4. The SNR computing module 3 is operable to set the average SNR
In step 71, the SNR computing module 3 is operable to set each of the channels with the same average SNR
In step 72, the SNR computing module 3 is operable to compute the expected value μQ and the variance σQ2 of the effective SNR according to the fading parameter m and the average SNR
In practice, the SNR computing module 3 is operable in advance to determine whether the fading parameter m is a positive integer. When the determination is affirmative, the SNR computing module 3 is operable to compute the expected value μQ and the variance σQ2 of the effective SNR based upon Equations (6) and (7), respectively. When it is determined that the fading parameter m is not a positive integer, the SNR computing module 3 is operable to compute the expected value μQ and the variance σQ2 of the effective SNR based upon Equations (4) and (5), respectively.
From Equations (4) to (7), it can be appreciated that the SNR computing module 3 computes the expected value μQ, and the variance σQ2 of the effective SNR based upon the average SNR
In step 73, the capacity computing module 4 is operable to compute, based upon Equation (12), the outage capacity CB corresponding to the average SNR
In step 74, the output module 5 is operable to determine whether there is an instruction of setting another average SNR
In step 75, the output module 6 is operable to provide the transceiver system 100 with the outage capacity CB corresponding to each of the average SNRs
Taking
From
In this embodiment, the fading parameter m of Nakagami channels is not limited to a positive integer. The SNR computing module 3 is capable of computing the expected value μQ and the variance σQ2 of the effective SNR with the fading parameter m that is an arbitrary positive integer, or that is equal to or greater than ½. Therefore, the evaluation device 300 according to this invention is suitable for simulation of the channels of the transceiver system 100 with various fading levels in a metropolis.
It should be noted that, in other embodiments, the transmitter 1 may include only one transmit antenna 12. Thus, the diversity unit 11 could be omitted, and the transmitter 1 is operable to transmit signals through the sole transmit antenna 12. Further, the receiver 2 may also include only one receive antenna 22. Thus, the synthesis unit 21 could be omitted, and the evaluation device 300 directly analyzes the signal received from the sole receive antenna 22.
In conclusion, the evaluation device 300 according to the present invention is capable of computing the outage capacity CB corresponding to a particular outage rate once the expected value μQ and the variance σQ2 of the effective SNR are obtained. Therefore, the evaluation device 300 according to this invention is suitable for simulating the performance of the transceiver system 100 in a metropolis.
While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Number | Name | Date | Kind |
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20030045307 | Arviv et al. | Mar 2003 | A1 |
Number | Date | Country | |
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20120129466 A1 | May 2012 | US |