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Old 09-16-2012, 05:48 PM   #5
chaley
Grumpy old git
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Posts: 9,241
Karma: 2902112
Join Date: Jan 2010
Location: UK
Device: Reader
@nremi: 3 mbit/sec actual throughput isn't bad over WiFi to a phone.

There are several reasons that wifi throughput doesn't live up to the max numbers that are advertized, such as 54mbit/set one sees for WiFi G. First, WiFi is half duplex, which means that only one device on the entire network (and your neighbors' networks) can transmit at a time. TCP/IP requires positive acknowledgement of data, so the receiving machine can only receive so much before it must respond, stopping transmission. Second, any other WiFi router in the same area that is using a similar channel will cause retransmissions or delay of packets (the neighbor-on-the-same-channel problem). Cabled connections are much faster because they are both point to point and full duplex, meaning that there is no adjacent machine interference and both computers can talk at the same time. For example, a speed test for my laptop connected over wifi G (54 mbit/sec) gets 8 mbit/second throughput. The same test on the same machine using a 100mbit/sec cable connection to the same router runs at 53 mbit/second.

When uploading or downloading books, both calibre and CC stuff bytes at the network as fast as the network will take them. In your case, all 100 mBytes will be sent in one go. We have no control over how fast the networking layers run (speed of the CPU and networking hardware), how the networking layers split up the data, how often the two operating systems choose to stop the transfer to acknowledge what has already been sent, or how fast the device can write the data to the "SD card".

There is one thing we can do to our protocol that might speed things up by around 20%. The problem is that the change totally breaks the protocol, eliminating the ability to embed control information into the data stream. I haven't been eager either to take the risk that things will break or to find a different way to pass the control information. I will eventually take on this task, once we have reduced the "feature queue" to a manageable level.

Regarding news feeds: calibre sends news to devices but does not delete news feeds from devices. This is out of CC's control. However, CC does give you some help for deleting them. Group by tags, choose News, then sort the list by date. Granted you must delete them one at a time, but at least they are all in front of you in the right order.
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