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19 megabits on 3G
haligan writes "Bell Labs research arm announced the development of two prototype chips that would allow mobile devices to receive more than 19 megabits of data per second on 3G networks." Power consumption is low enough for cel phone type applications.
On the Minneapolis Wireless Airport network, you get the first day of access free! Everyday after that is $10 tho, but still if you have a long lay over the $10 is more than worth it. I've used the network several times before and the download speeds aren't too slow(usually 125k and up).
Acording to the lecture i attended last year by a very sensior vodaphone engineer this bandwidth is the maximum available. It isnt all used for data in fact they reserve a few channels for voice and a few for data (depending on the area past usage etc) also if you are the only user then things get faster still. However it wtill wont be that fast most 3g implementations relie on doing TCP/IP on top of TCP/IP on top of another protocol or 5 yes there are 2 tcp/ip stacks. This is so the phone network can keep you inside there network
A couple of points about this technique:
a.) I'd call this a 4G demonstration. Maximum data rates in the 3G specs/proposals (WCDMA, cdma2000, etc...) are much lower than 19 Mbps. e.g. 2-3 Mbps. e.g. By transmitting at 19 Mbps, they're not using WCDMA protocols.
b.) In a multiple Tx configuration, you're increasing the amount of interference. With 4 Tx antennas, the amount of interference seen by other users just went up by a factor of 4. This means your overall capacity just dropped by a factor of 4.
c.) Tranmitting at a higher data rate in WCDMA limits the number of other users you can have on the channel. You can only have a few users in a WCDMA cell transmitting at near maximum data rate.
FPGA, Wireless, ASIC, Verilog, VHDL, HW, 10yr exp, Team Lead, Ottawa (More? Email above. slashdotusername=dgmartin98 )
People tend to forget that sending out ACK packets upstream greatly effects the download speed of a connection. Asychronous connections with low upstreams often become saturated and drag down the downstream to unbearable levels.
Actually, the 4 antennas do use the same channel---the same frequency band. BLAST uses space-time coding techniques to increase the capacity of a single channel. Each antenna transmits a different signal on the same frequency band; the signal processing on the receive end separates them out.
In general it works well, although it's quite nonintuitive for a number of reasons.
For example, you might imagine that you could achieve similar data rates if you just transmitted 4 times the power with a single antenna instead. Unfortunately, due to multipath (reflections off buildings, trees, etc.), the average received power will vary so much that you can't be as aggressive with your data rate. With 4 antennas, the average received power will be much more even; when one antenna isn't coming in too well, the other three are likely not to have the same problem.
Secondly, amplifier costs don't scale linearly with power. So at those power levels, multiple lower-power amps can be significantly cheaper than one higher-power amp. The cost difference can be large enough that it's worth all the extra signal processing.
Finally, FCC rules are often kinder to systems which distribute power across multiple antennas than they are with a single antenna transmitting the same power. I don't know if that's the case with 3G but I can imagine so.
Those of you who study this please forgive the oversimplification.