Many research papers about cognitive radio address cooperative spectrum sensing, a technique that require exchanging local sensing results among the cognitive users or reporting them to a fusion center. A TDMA scheme where each user transmit a single bit (e.g., 0 channel is idle, 1 channel is busy) is commonly assumed.
Yet; to the best of my knowledge, transmitting a single bit may result difficult in terms of synchronization and may require preamble, signaling or even redundancy in order to do so.
Thank you in advance.
Regards.
Dear Sir,
I advise you to read this Book "Advanced Wireless Networks"
https://books.google.iq/books?id=XzDODAAAQBAJ&pg=PA558&lpg=PA558&dq=Is+it+possible+to+successfully+transmit+and+receive+a+single+bit+via+wireless&source=bl&ots=m8tkllKP0U&sig=HluzWmNSCxBTbs1eRErFBflZRds&hl=en&sa=X&ved=0ahUKEwit76bH6LTSAhVDM5oKHfOQD-YQ6AEIRDAI#v=onepage&q=Is%20it%20possible%20to%20successfully%20transmit%20and%20receive%20a%20single%20bit%20via%20wireless&f=false
Thank you very much, I will look through the book you suggested; yet in a first overlook I cannot find what I want to know.
Regards.
It is possible to send it via wireless but would be waste of time as the channel will stay idle till the bit isn't transmitted , redundancy will have to be introduced to ensure the flow of the bits in sequence . Kindly refer mobile communications by jochen shiller
This is an engineering problem not a physics one. Yes it can be done and of course you have to be synchronized to do it. However if you have a good clock you are not reliant on the particular bit for synchronization. For example, when you receive one or more bits you could choose to synchronize based on those bits and, with an accurate clock, that synchronization can be maintained till another bit arrives that allows you to update the precise timing of your clock as well as reading the bit. In reality your clock drifts or your communications channel may effectively change in length (causing a time shift). So you have to be sure that there are sufficiently frequent bits to update your clock synchronization by one means or another. The critical point is that you do not necessarily rely on specific re-synchronization before every datum bit (or set of data bits).
How this is done in reality varies from system to system. The reason it is a problem is that people usually push a channel to the highest rate they can which makes synchronization tricky and critical. You may wish to note in some simple communications protocols (not necessarily wireless) there is a scrambling code to ensure that a variety of 1s and 0s are received in order to force physical layer transitions that a local synchronization function can lock onto.
Unfortunately you will have to look into the detail to see how this is done for your system of interest.
Dear, Smriti Tikoo and Brian Turton,
thank you very much for your replies, which reinforce just what I was initially thinking about the question.
Several research papers addressing energy-efficient cognitive radio (CR) base their optimization frameworks in the assumption that many CRs can transmit a single bit to a fusion center in order to determine if a primary channel is vacant or occupied. From my point of view this assumption introduced more problems than solutions when thinking about energy consumption.
Regards.
The point here is that you will spend a lot of resources to transmit just a single bit. Therefore, a protocol that considers several radios sending a single bit for the sake of saving energy does not represent a practical approach.
Also, by opening a socket you are implying at least a frame (link layer header and trailer), which provide a lot of bits in order to carry your payload of only one bit.
Regards.
Hello again, master Cornwall,
perhaps you are missing the whole point. Imagine a cognitive radio wireless network where each node performs spectrum sensing in order to identify spectrum-time opportunities (in a single channel). Many nodes sense the same spectrum band to overcome the effects of shadowing, which may lead to misdetection by identifying an occupied channel as idle. Each sensing device performs a local decision based on its observations and then transmit this decision to a fusion center (a base station or a cluster head, for example). The fusion center compares the sensing outcomes and then broadcast its decision regarding the sensed channel.
In the literature, it is claimed that each node may transmit a single bit carrying its decision for the sake of saving energy.
What I am stating here is that the overhead of sensing a single bit would not worth the effort nor the energy consumption. This is the case you are considering, where you frame the bit with header and trailer. The payload would be one bit but the frame would not. If one would decide not to frame the bit but send it as raw as possible into the channel, then the problems stated above would arise (entirely PHY layer related, and as Dr. Turton stated, it is an engineering problem because the point is how to do it using hardware) .
I know that you can send as much bits as you want using the current approaches for wired and wireless communications, the payload size would determine how many frames, packets or segments would be necessary depending of the technology you employ; yet, in this case which matters the most is maximizing the energy-efficiency (which can be measured as bit per Joule, for example).
I hope this time I have expressed my point better. I really appreciate your interest in the question, and I thank you deeply for your comments.
Regards.
Hi, I am wondering what beacon means in transmission, it is single bit of information which starts frame what ever be requred to do afterwards. Like on and off keying, if your clock is in certain vicinity, you do not need to synchronise it, just detect.
Am I wrong for this case? Regards
Ismail Kaya
Hello, Ismail Kaya,
I do not know how it is done in practice; yet, I would use more than one beacon, e.g., a sequence of beacons, in order to increase the probability of detection.
However, I think the original question can be answered just by considering the bit time, if it is too short, the bit might not be detected and several bits may be necessary. On the other hand, if the the bit time is long enough, the bit is more likely to be detected.
Regards
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