1.2 RFID System Anti-Collision Technology
11
Equation (1.2) is the mathematical model of a two-pair channel.
From the above analysis, it can be seen that the influence of the channel on the
signal can be summarized into two points: one is multiplicative interference k(t),
and the other is additive interference n(t). If we understand the characteristics of
k(t) and n(t), we can figure out the specific effect of the channel on the signal. The
different characteristics of the channel are reflected in the channel model. Only k(t)
and n(t) are different.
In general, k(t) is a complex function that may include a variety of linear and
nonlinear distortions. At the same time, because the delay and loss characteristics of
the channel change randomly at any time, k(t) can only be expressed by a random
process. However, a large number of observations indicate k(t) that in some channels
remains largely unchanged over time. In other words, the channel’s effect on the
signal is fixed or changes very slowly. While some channels, otherwise, their k(t)
is a random change quickly. Therefore, when analyzing multiplicative interference
k(t), channels can be roughly divided into two categories. A class of channels are
called constant parameter channels, that is, their k(t) can be regarded as not changing
with time or not changing at all. The other is called a random parameter channel,
which is a generic term for a non-constant parameter channel, or k(t), which varies
rapidly and randomly.
Now, let’s talk about the coded channel model. It is obviously different from the
modulation channel model. The effect of the modulated channel on the signal is to
make the modulated signal undergo analog changes through k(t) and n(t). The effect
of the coded channel on the signal is a transformation of the digital sequence, which
changes from one digital sequence into another. Therefore, the modulation channel is
sometimes regarded as an analog channel and the coded channel as a digital channel.
Since the coded channel contains the modulation channel, it is affected by the
modulation channel. However, from an encoding and decoding point of view, this
effect is already reflected in the demodulator’s sequence of output digits, that is, the
output digits will slip with some probability. Obviously, the worse the modulated
channel, that is, the less ideal the characteristic and the more serious the additive
noise, the greater the probability of error will be. Therefore, the coded channel
model can be described by the transfer probability of numbers.
The mathematical model of the two-pair channel is described in detail above, and
the following concepts are very important in discussing the effect of the channel on
the tag work.
Channel bandwidth is defined as the bandwidth of the channel allowed to pass,
referred to as bandwidth [20]. The bandwidth is calculated as follows:
BW = f 2 − f 1
(1.3)
where f 2 is the highest frequency that the signal can pass in the channel; f 1 is the
lowest frequency. Both are determined by the physical properties of the channel.
When the composition of the channel is determined, the bandwidth is determined.
11
Equation (1.2) is the mathematical model of a two-pair channel.
From the above analysis, it can be seen that the influence of the channel on the
signal can be summarized into two points: one is multiplicative interference k(t),
and the other is additive interference n(t). If we understand the characteristics of
k(t) and n(t), we can figure out the specific effect of the channel on the signal. The
different characteristics of the channel are reflected in the channel model. Only k(t)
and n(t) are different.
In general, k(t) is a complex function that may include a variety of linear and
nonlinear distortions. At the same time, because the delay and loss characteristics of
the channel change randomly at any time, k(t) can only be expressed by a random
process. However, a large number of observations indicate k(t) that in some channels
remains largely unchanged over time. In other words, the channel’s effect on the
signal is fixed or changes very slowly. While some channels, otherwise, their k(t)
is a random change quickly. Therefore, when analyzing multiplicative interference
k(t), channels can be roughly divided into two categories. A class of channels are
called constant parameter channels, that is, their k(t) can be regarded as not changing
with time or not changing at all. The other is called a random parameter channel,
which is a generic term for a non-constant parameter channel, or k(t), which varies
rapidly and randomly.
Now, let’s talk about the coded channel model. It is obviously different from the
modulation channel model. The effect of the modulated channel on the signal is to
make the modulated signal undergo analog changes through k(t) and n(t). The effect
of the coded channel on the signal is a transformation of the digital sequence, which
changes from one digital sequence into another. Therefore, the modulation channel is
sometimes regarded as an analog channel and the coded channel as a digital channel.
Since the coded channel contains the modulation channel, it is affected by the
modulation channel. However, from an encoding and decoding point of view, this
effect is already reflected in the demodulator’s sequence of output digits, that is, the
output digits will slip with some probability. Obviously, the worse the modulated
channel, that is, the less ideal the characteristic and the more serious the additive
noise, the greater the probability of error will be. Therefore, the coded channel
model can be described by the transfer probability of numbers.
The mathematical model of the two-pair channel is described in detail above, and
the following concepts are very important in discussing the effect of the channel on
the tag work.
Channel bandwidth is defined as the bandwidth of the channel allowed to pass,
referred to as bandwidth [20]. The bandwidth is calculated as follows:
BW = f 2 − f 1
(1.3)
where f 2 is the highest frequency that the signal can pass in the channel; f 1 is the
lowest frequency. Both are determined by the physical properties of the channel.
When the composition of the channel is determined, the bandwidth is determined.