2011年8月31日 星期三
2011年8月29日 星期一
2011年8月28日 星期日
2011年8月23日 星期二
2011年8月21日 星期日
2011年8月17日 星期三
2011年8月16日 星期二
2011年8月15日 星期一
2011年8月12日 星期五
如何讓office 2003 2007共存
米粒的億想世界: 如何讓office 2003 2007共存，並預設以2003開啟
在cmd下執行
"C:\Program Files\Microsoft Office\OFFICE11\winword" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\excel" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\powerpnt" /regserver
在cmd下執行
"C:\Program Files\Microsoft Office\OFFICE11\winword" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\excel" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\powerpnt" /regserver
如何讓office 2003 2007共存
米粒的億想世界: 如何讓office 2003 2007共存，並預設以2003開啟
在cmd下執行
"C:\Program Files\Microsoft Office\OFFICE11\winword" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\excel" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\powerpnt" /regserver
在cmd下執行
"C:\Program Files\Microsoft Office\OFFICE11\winword" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\excel" /regserver
"C:\Program Files\Microsoft Office\OFFICE11\powerpnt" /regserver
2011年8月10日 星期三
2011年8月9日 星期二
2011年8月8日 星期一
2011年8月7日 星期日
EuP(Energy-using Products)&ErP(Energy-related Products)&CE Marking的恩怨情仇 - 能邁科技股份有限公司
EuP(Energy-using Products)&ErP(Energy-related Products)&CE Marking的恩怨情仇 - 能邁科技股份有限公司
*由以上兩點來做個總結
1. Energy-related Products(ErP)指令為生態化設計指令，CE的部分比較偏向於該產品的能耗及安全性，彼此之間是沒有絕對關聯性的。
2. 由於Energy-related Products(ErP)指令所涵蓋的範圍遠大於現在CE標章，所以產品可能只被Energy-related Products(ErP)所規範到，而不被CE所管制，此時只需要準備Energy-related Products(ErP)的相關文件即可，再次證明，有ErP不見得有CE；有CE的產品也必須也被ErP管制到才需要ErP文件。
3. 若同時被Energy-related Products(ErP)及CE規範到，也不需在額外準備冗長的文件，只需將過去所用過CE相關文件再附上Energy-related Products(ErP)所要求的TDF文件即可。
由以上結論可以知道，Energy-related Products(ErP)與CE兩者之間是沒有直接關係的，Energy-related Products(ErP)符合報告可以廠商自行製作，不再需要經由第三方檢驗單位。
而在準備Energy-related Products(ErP)報告上，環境評估研究報告有一定的難度，能邁提供了一個來自歐盟EuP團隊報告規格且不需要供應商要資料的方法，詳情請看http://www.tisamax.com/article/view/61
*由以上兩點來做個總結
1. Energy-related Products(ErP)指令為生態化設計指令，CE的部分比較偏向於該產品的能耗及安全性，彼此之間是沒有絕對關聯性的。
2. 由於Energy-related Products(ErP)指令所涵蓋的範圍遠大於現在CE標章，所以產品可能只被Energy-related Products(ErP)所規範到，而不被CE所管制，此時只需要準備Energy-related Products(ErP)的相關文件即可，再次證明，有ErP不見得有CE；有CE的產品也必須也被ErP管制到才需要ErP文件。
3. 若同時被Energy-related Products(ErP)及CE規範到，也不需在額外準備冗長的文件，只需將過去所用過CE相關文件再附上Energy-related Products(ErP)所要求的TDF文件即可。
由以上結論可以知道，Energy-related Products(ErP)與CE兩者之間是沒有直接關係的，Energy-related Products(ErP)符合報告可以廠商自行製作，不再需要經由第三方檢驗單位。
而在準備Energy-related Products(ErP)報告上，環境評估研究報告有一定的難度，能邁提供了一個來自歐盟EuP團隊報告規格且不需要供應商要資料的方法，詳情請看http://www.tisamax.com/article/view/61
2011年8月6日 星期六
2011年8月5日 星期五
2011年8月3日 星期三
2011年8月2日 星期二
2011年8月1日 星期一
Maximal-Ratio Combining
MRC(Maximal-Ratio Combining)
MRC系統的工作是依其合成器內增益的加權值，將每條分支波道信號的訊雜比(signal-to-noise ratio, SNR)大小作調整，信號愈強，加權值愈大，所以強度大的信號會比弱者的信號得到較高的加權值之後再將得到的信號做為系統的輸出值。
首先把兩根發射天線中產生的衰弱(fading) 訊號做比對，在同時間點上各自加權重，權重數學如(5.9)所示:
(5.9)
透過權重把(5.9)代入MRC公式得到在發射端分別產生兩組不同雜訊，數學如(5.10)所示:
(5.10)
最後利用MRC技術把兩根不同路徑發射天線所產生衰落(Fading)相加，得到輸出值在透過接收端去做解調。
5.6.2 MRC架構
此圖為Maximal-Ratio Combining 結構圖，使用於 接收天線
MRC系統的工作是依其合成器內增益的加權值，將每條分支波道信號的訊雜比(signal-to-noise ratio, SNR)大小作調整，信號愈強，加權值愈大，所以強度大的信號會比弱者的信號得到較高的加權值之後再將得到的信號做為系統的輸出值。
首先把兩根發射天線中產生的衰弱(fading) 訊號做比對，在同時間點上各自加權重，權重數學如(5.9)所示:
(5.9)
透過權重把(5.9)代入MRC公式得到在發射端分別產生兩組不同雜訊，數學如(5.10)所示:
(5.10)
最後利用MRC技術把兩根不同路徑發射天線所產生衰落(Fading)相加，得到輸出值在透過接收端去做解調。
5.6.2 MRC架構
此圖為Maximal-Ratio Combining 結構圖，使用於 接收天線
Transmit beamforming | MobileParadigm
Transmit beamforming | MobileParadigm
Transmit beamforming
In this post, we continue my discussion of beamforming by focusing on transmit beamforming. As previously mentioned, beamforming is a method of concentrating radio frequency (RF) energy in order to improve the signal to noise ratio (SNR) at the receiver, thereby improving network performance and predictability.
Transmit beamforming (TxBF) is a method of transmitting two or more phase-shifted signals so that they will be in-phase at particular points in space where the transmitter believes the receiver to be, thereby increasing SNR. Two forms of TxBF are optional components of the IEEE 802.11n draft amendment to the 802.11 standard. Explicit and implicit TxBF require feedback from 802.11n stations (STA) and thus will not operate with legacy stations at all. Enterprise WLAN vendors do not support implicit and explicit TxBF at this time because the 802.11n chipsets do not currently support either form of TxBF.
Cisco has introduced a proprietary form of TxBF called ClientLink. ClientLink can work with 802.11 g/a STAs because it requires no modifications in the STA. ClientLink is designed to improve the SNR for legacy STAs in the downlink (AP-to-STA) direction only. A boost in SNR can improve the STA’s “rate over range” performance because the modulation rate for 802.11 STAs will increase as the SNR increases. Improving rate over range performance is particularly important for legacy STAs because they can consume considerably more airtime than 802.11n STAs, and therefore can reduce the achievable throughput of 802.11n STAs. Alternatively, Air Time Fairness (ATF) mechanisms can also regulate legacy STA airtime consumption.
TxBF changes the phase of the original signals in relation to each other and transmits the phase-shifted signals using two or more antennas to the STA (see figure). As the signals propagate through the air, they additively combine at various points in space. The figure shows an example of two out-of-phase signals propagating from an AP to a legacy STA. The green dots represent the points in space where the two out-of-phase signals combine to form a signal with an SNR that is up to 3 dB higher than (i.e., twice as high as) the original signal. In a multipath-rich environment, even higher levels of gain are theoretically possible. Cisco is the first enterprise WLAN vendor to implement TxBF, and it claims it can achieve 4 to 6.5 dB of SNR gain in a multipath-rich environment. A 6.5 dB gain is an increase of approximately 4.5 times the original signal.
Figure 1: Transmit beamforming (source: Cisco Systems)
The challenge with TxBF is figuring out how to modify the transmit signal phases for the greatest possible gain. In the ClientLink implementation, the AP uses frames received from the STA in the uplink direction to determine how to modify the phase in the downlink direction. TxBF assumes that the uplink channel characteristics and the downlink channel characteristics are “reciprocal” (i.e., the same) in both directions. In reality, the uplink and downlink channels may not be reciprocal, especially when the STA is moving. So, in practice, TxBF performance gains will vary from moment to moment and STA to STA.
Unlike static and dynamic beamforming, TxBF does not change the antenna radiation pattern. Cisco’s TxBF implementation uses omnidirectional antennas that cause the signals to radiate in a doughnut-shaped pattern. Therefore, referring to TxBF as “beamforming” is somewhat misleading because it does not actually form a directed beam. Cisco’s TxBF achieves an SNR gain at “points in space” (i.e., the green dots in the figure). So the receiving STA must be located at the right point in space in order to achieve the maximum SNR gain. In contrast, static and dynamic beamforming achieve SNR gain throughout the radiated coverage area because both techniques focus the radiated energy.
TxBF and spatial multiplexing are mutually exclusive. This is because spatial multiplexing transmits different signals on each antenna, whereas TxBF transmits the same (phase-shifted) signals on each antenna. So, it is impossible to use TxBF and spatial multiplexing at the same time. That is why enterprises should use TxBF to provide SNR gain for legacy STAs only. In contrast, static and dynamic beamforming can operate in conjunction with spatial multiplexing.
Next time, we will look at dynamic beamforming.
Transmit beamforming
In this post, we continue my discussion of beamforming by focusing on transmit beamforming. As previously mentioned, beamforming is a method of concentrating radio frequency (RF) energy in order to improve the signal to noise ratio (SNR) at the receiver, thereby improving network performance and predictability.
Transmit beamforming (TxBF) is a method of transmitting two or more phase-shifted signals so that they will be in-phase at particular points in space where the transmitter believes the receiver to be, thereby increasing SNR. Two forms of TxBF are optional components of the IEEE 802.11n draft amendment to the 802.11 standard. Explicit and implicit TxBF require feedback from 802.11n stations (STA) and thus will not operate with legacy stations at all. Enterprise WLAN vendors do not support implicit and explicit TxBF at this time because the 802.11n chipsets do not currently support either form of TxBF.
Cisco has introduced a proprietary form of TxBF called ClientLink. ClientLink can work with 802.11 g/a STAs because it requires no modifications in the STA. ClientLink is designed to improve the SNR for legacy STAs in the downlink (AP-to-STA) direction only. A boost in SNR can improve the STA’s “rate over range” performance because the modulation rate for 802.11 STAs will increase as the SNR increases. Improving rate over range performance is particularly important for legacy STAs because they can consume considerably more airtime than 802.11n STAs, and therefore can reduce the achievable throughput of 802.11n STAs. Alternatively, Air Time Fairness (ATF) mechanisms can also regulate legacy STA airtime consumption.
TxBF changes the phase of the original signals in relation to each other and transmits the phase-shifted signals using two or more antennas to the STA (see figure). As the signals propagate through the air, they additively combine at various points in space. The figure shows an example of two out-of-phase signals propagating from an AP to a legacy STA. The green dots represent the points in space where the two out-of-phase signals combine to form a signal with an SNR that is up to 3 dB higher than (i.e., twice as high as) the original signal. In a multipath-rich environment, even higher levels of gain are theoretically possible. Cisco is the first enterprise WLAN vendor to implement TxBF, and it claims it can achieve 4 to 6.5 dB of SNR gain in a multipath-rich environment. A 6.5 dB gain is an increase of approximately 4.5 times the original signal.
Figure 1: Transmit beamforming (source: Cisco Systems)
The challenge with TxBF is figuring out how to modify the transmit signal phases for the greatest possible gain. In the ClientLink implementation, the AP uses frames received from the STA in the uplink direction to determine how to modify the phase in the downlink direction. TxBF assumes that the uplink channel characteristics and the downlink channel characteristics are “reciprocal” (i.e., the same) in both directions. In reality, the uplink and downlink channels may not be reciprocal, especially when the STA is moving. So, in practice, TxBF performance gains will vary from moment to moment and STA to STA.
Unlike static and dynamic beamforming, TxBF does not change the antenna radiation pattern. Cisco’s TxBF implementation uses omnidirectional antennas that cause the signals to radiate in a doughnut-shaped pattern. Therefore, referring to TxBF as “beamforming” is somewhat misleading because it does not actually form a directed beam. Cisco’s TxBF achieves an SNR gain at “points in space” (i.e., the green dots in the figure). So the receiving STA must be located at the right point in space in order to achieve the maximum SNR gain. In contrast, static and dynamic beamforming achieve SNR gain throughout the radiated coverage area because both techniques focus the radiated energy.
TxBF and spatial multiplexing are mutually exclusive. This is because spatial multiplexing transmits different signals on each antenna, whereas TxBF transmits the same (phase-shifted) signals on each antenna. So, it is impossible to use TxBF and spatial multiplexing at the same time. That is why enterprises should use TxBF to provide SNR gain for legacy STAs only. In contrast, static and dynamic beamforming can operate in conjunction with spatial multiplexing.
Next time, we will look at dynamic beamforming.
Transmit beamforming
此技術是傳送端在探知接收端的方位後, 利用多天線傳送單一『加強』的訊號給接收端, 此舉同樣可改善SNR, 達到提高傳輸率或增加傳輸距離的效果。傳輸波束成形是802.11n 中的選用(option) 規格, 所以並非所有產品都有實作此技術。
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