| Telecontrol |
Telecontrol means "remote control".
This involves the use of radio waves for radio control of devices or
machinery at a remote location. This is used principally for remote
control of cranes, concrete pumping machinery, and the industrial
equipment used for engineering work, construction, forestry and the
like. |
| Telemetry |
Telemetry is the transmission of
remote measurement data, and this involves the transmission of
measurement results from a measuring device or the like at a remote
location using radio waves. In general with telemetry a host sends an
enquiry to equipment that has a measuring sensor (water level,
temperature, humidity, voltage, current, rate of flow and so on)
asking if it has data to transmit, and if there is data, it receives
it, often gathering information from several devices. |
| Preamble |
In order to establish
synchronization of the frames required for the transmission of data
between transmitter and receiver, this signal is added to the front of
the frame, and may consist of a bit stream of alternately repeated 0s
and 1s. |
| Receive sensitivity |
The unit for receive sensitivity is
dBm, and it is expressed as 0 dBm of relative power when received
power is 1 mW. It is also sometimes shown as a voltage uV. The method
of stipulating receive sensitivity varies according to the
manufacturer, and may be stipulated as SINAD or error rate or the
like. |
| Spurious emissions |
These are unwanted emissions that
fall outside the radio wave of interest. If there are many spurious
emissions, they will have adverse effects on other communications.
|
| Deviation |
This is the degree of frequency
shift in the frequency modulation system. |
| RSSI (Received Signal Strength
Indicator) |
Used with carrier sensing, this
signal indicates the intensity of the received signal. It is output by
the receiving equipment. |
| VCO |
An oscillator that can change an
oscillating frequency using a signal voltage added to the input. It is
used with FM modulation and FSK modulation. |
| Carrier |
A signal that is suited to the
transmission path whose parameters are manipulated in order to convey
the information of the base band data. |
| Carrier sensing |
This denotes the checking of a
channel to see if it is free before transmitting equipment transmits
radio waves. If the checked channel is being used, the equipment
switches channels, and if the channel is free, it begins emitting
radio waves. |
| Base band data |
Information that has been changed
into an electric signal. |
| Base band transmission system |
A system for transmitting
information that has been changed into an electric signal. |
| Carrier transmission system |
This is a system by which the
carrier is modulated by the base band signal, and transmits on the
frequency band of the carrier frequency. |
| Modulation |
The parameters of a carrier that is
suited to the transmission path is shifted proportionally by the base
band signal. In radio transmissions, this denotes the manipulation by
shifting of a base band waveband to a high frequency waveband. |
| BER (Bit Error Rate) |
BER = Number of error bits / Number
of transmitted bits |
| S/N (Signal to Noise Ratio) |
The voltage ratio for the output
level (noise) when nothing is input in an amplifier or the like, and
the output level when a reference signal is input can be found with
the following equation.
S/N = 20 log 10 (signal voltage / noise voltage)
It is necessary to consider the following 2 points as reasons for why
S/N can become a problem with radio equipment.
1) The receiving antenna receives RF noise from space.
2) There is noise generated by components of the receiver circuit
themselves. |
| C/N (Carrier to Noise Ratio) |
The ratio of the power of the
carrier to the power of noise output. |
| Noise figure |
The components used in amplifiers
necessarily generate noise, and amplifying a signal decreases S/N.
Noise figure denotes the ratio of the input SN rate and the output SN
rate, and if this value is smaller, better amplifier performance is
indicated. |
| SINAD (Signal + Noise +
Distortion to Noise + Distortion Ratio) |
This refers to the method of taking
the ratio of the demodulated output level of the received signal level
when modulation is applied, and of the aggregate level of noise and
distortion of the demodulated output with only the signal component
removed. A ratio of 12 dB for the received signal level may be taken
as a reference for sensitivity.
 |
| ISM band (Industrial, Scientific,
and Medical band) |
This is a waveband reserved for the
industrial, scientific and medical sectors, and is used in every
country. Specifically, the 2.4 GHz band is common to all countries,
and the devices using wireless LAN, Bluetooth, Home RF and so on are
in competition with this band. This equipment uses the spread spectrum
communication system required for wide band.
| Japan |
2.4 GHz band |
| North America |
0.9 GHz, 2.4 GHz, 5.7 GHz bands |
| Europe, Hong Kong, Singapore,
Australia |
2.4 GHz, 5.7 GHz band |
|
| Spread Spectrum Communication |
The communication method used for
wireless LAN and Bluetooth. There are two types, direct sequence
spread spectrum (DSSS) used by wireless LAN, and frequency hopping
spread spectrum used by Bluetooth. By spreading the signal spectrum
over a wide band, multi-access, good resistance to noise, and good
security can be achieved. |
| Burst error |
Consecutive data errors that occur
suddenly. If errors spanning several bytes occur, complete decoding at
the receiving end is not possible even if error correction is applied.
As a measure against burst errors, methods such as interleaving are
used. |
| FEC (Forward Error Correction) |
In order to carry out error
correction at the receiving equipment end, the transmitting equipment
includes an error correction function in the sent data. Reed-Solomon
code, trellis code and the like are used, and although they increase
the data amount, they allow more reliable transmission. |
| Interleaving |
A technique for handling burst
errors in the transmission path. In order to prevent the loss of data
through burst errors, with this method data streams containing error
correction functions are dispersed, so that even if burst errors
occur, the error correction function can be used effectively for
decoding at the receiving equipment end. The operation performed at
the receiving end to return the signal to its original state is called
deinterleaving. |
