New answers tagged

1

Is there a simple way of representing the MIMO channel without a matrix form since in our case we don't have diversity and we are not exploiting the multipath components? Or do we have always to represent MIMO channel as a matrix H? Yes and no. Yes Each of the T transmit antennas has a path to each receive antenna. So by definition, you have TxR equations. ...


1

We consider a wireless communication system, where there is only Line Of Sight path between the MIMO transmitter and the MIMO receiver. Good news: having line of sight is a good situation, often. Bad news: you don't get any diversity in that case, so your MIMO system, in the best case, is as good as a SISO system with a directive antenna (as you noticed). ...


0

Low Frequency crystal frequency feeding a phase locked loop integrated into the RFIC. An LC oscillator (Colpitts oscillators are a good example) is used to provide the on-channel (900MHz/1800MHz etc) RF carrier. All of these low cost/high volume systems use Zero IF Architectures, where the local oscillator is at the channel frequency.


0

The carrier is generated by: Cheap quartz crystal from 26 to 40 MHz and +/- 10 ppm frequency deviation An internal PLL that pulls the frequency up. There's no need for using a more precise TXCO with +/- 1 ppm frequency deviation because channels are pretty wide in frequency. Harmonic filters are mandatory. To answer your question: The oscillator is a ...


0

I have two such transceivers ... With two independent transcievers, there's no reason they should drift together in phase. You would have to supply both from the same 10 MHz reference signal if you wanted them to stay coherent. Even then, reprogramming one to a different frequency and back again would randomise the phase. Generally the absolute phase of a ...


0

In the big picture, the two things that differentiate wireless communication strategies from each other are throughput and range. Within these, are power and cost. Throughput is determined by channel bandwidth and by the modulation scheme used to encode the data. In the 2.4 GHz band, 802.11bgn supports 20 or 40 MHz channels, and using the modulations ...


1

Different wireless technologies can work in very different ways. Any technology can in theory be used in any frequency band. However two present in the same band will tend to interfere with each other's signals unless special precautions are taken. For example WiFi, bluetooth, microwave ovens and car door keys all use 2.4 GHz. But if a badly maintained (...


1

They overlap a lot. Wifi and bluetooth and a number of bespoke wireless communication systems share the same frequency band... as does your microwave oven, for that matter. It's the protocol that differentiates them, not anything to do with what frequency you run them at. You could theoretically use wifi at a completely different frequency, if you had a ...


1

Appearance of RTS/CTS signaling presumes the CSMA/CA implementation is supplemented in your application with Multiple Access Collision Avoidance, a technique used to fight hidden/exposed terminal problems. It is unclear if you ask about scenarios which the technique is designed for, or you have concerns about a station violating the CSMA/CA + MACA protocol ...


1

Will that affect the whole network? All stations that now lose packets are affected. I.e. every station at which your malfunctioning's station is strong enough to damage received packets. How this kind of an issue is handled? Well, since that bad station won't always have something to send, it will probably not be handled at all: packets that collided ...


0

Power and ground connections to the PIC are not shown in your schematic. Although, power and ground are shown on the HC12. Please add the missing connections to the schematic. Using two serial ports on your PC you should test that the HC12's can communicate together via those two ports.


1

Since this question is asked very often and it's not easy to find clear answers from internet (well, there are, but there is also just as much misinformation,) I feel that I should write here my findings - even though the original post is quite "oldish." The OP's link about the device is not working anymore, so I'm assuming we are talking about the ...


Top 50 recent answers are included