This protocol was designed under the assumption that all nodes have the same transmission ranges, and does not solve the hidden terminal problem. The RTS/CTS frames can cause a new problem called the exposed terminal problem in which a wireless node that is nearby, but is associated with another access point, overhears the exchange and then is signaled to back off and cease transmitting for the time specified in the RTS.
RTS/CTS is an additional method to implement virtual carrier sensing in carrier sense multiple access with collision avoidance (CSMA/CA). By default, 802.11 relies on physical carrier sensing only, which is known to suffer from the hidden node problem.
The RTS/CTS packet size threshold is 0–2347 octets. Typically, sending RTS/CTS frames does not occur unless the packet size exceeds this threshold. If the packet size that the node wants to transmit is larger than the threshold, the RTS/CTS handshake gets triggered. Otherwise, the data frame gets sent immediately.
IEEE 802.11 RTS/CTS mechanism could help solve exposed node problem as well, only if the nodes are synchronized and packet sizes and data rates are the same for both the transmitting nodes. When a node hears an RTS from a neighboring node, but not the corresponding CTS, that node can deduce that it is an exposed node and is permitted to transmit to other neighboring nodes.[1] If the nodes are not synchronized (or if the packet sizes are different or the data rates are different) the problem may occur that the exposed node will not hear the CTS or the ACK during the transmission of data of its neighbor.
chunk = 1024# Record in chunks of 1024 samples sample_format = pyaudio.paInt16 # 16 bits per sample channels = 2 fs = 44100# Record at 44100 samples per second seconds = 3 filename = "output.wav"
p = pyaudio.PyAudio() # Create an interface to PortAudio
# Store data in chunks for 3 seconds for i inrange(0, int(fs / chunk * seconds)): data = stream.read(chunk) frames.append(data)
# Stop and close the stream stream.stop_stream() stream.close() # Terminate the PortAudio interface p.terminate()
print('Finished recording')
# Save the recorded data as a WAV file wf = wave.open(filename, 'wb') wf.setnchannels(channels) wf.setsampwidth(p.get_sample_size(sample_format)) wf.setframerate(fs) wf.writeframes(b''.join(frames)) wf.close()
近日遇到一个怪事,即资源管理器左侧的导航面板中的One Drive图标消失了,而One Drive for Business的图标却还在。尝试了重新登录One Drive、重新安装One Drive、修改注册表等方法,均无果。最后通过修改注册表找回了图标,注册表项文件内容如下:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Windows Registry Editor Version 5.00
; Created by: Shawn Brink ; Created on: March 20th 2015 ; Updated on: December 5th 2019 ; Tutorial: https://www.tenforums.com/tutorials/4818-add-remove-onedrive-navigation-pane-windows-10-a.html